[Transcriber's Notes] Obvious spelling errors have been corrected. I have not reconciled thevariety of spellings of names and other words. Obvious factual errors, typographical errors, discoveries made after 1892, and contemporary(2008) theories and use of words are noted in the text within squarebrackets. I have not researched and checked every assertion by theauthor. This book was published 5 years before discovery of the electron. Seethe labored and completely inaccurate explanations of aurora and"energy, atomic". The author and his contemporaries were like fifteenthcentury sailors. They had a good idea of their latitude and direction(Ampere, Kirkoff, Maxwell, Gauss, Faraday, Edison, …), but only thevaguest notion of their longitude (nuclear structure, electrons, ions). Altitude (special relativity, quantum theory) was not even imagined. Some relevant dates:Franklin's Kite--1752Faraday's Law of Induction--1831Maxwell's Equations--1861Edison's Phonograph--1877Edison's light bulb--1879Edison's first DC power station--1882Michelson-Morley experiment disproving ether--1887Hertz demonstrates radio waves--1888Westinghouse first AC power station--1891This book--1892Discovery of the electron--1897Marconi radio signals cross the English Channel--1897First Vacuum Tube--1904Special Relativity, photo-electric effect explained with photons--1905General Relativity: space-time dilation and curvature--1915Confirmation of general relativity's prediction of the deflection of starlight by the Sun--1919Discovery of the proton--1920Quantum theory--1926Discovery of neutron--1932First transistor--1947Soviet satellite Luna measures solar wind--1959Edward M. Purcell explains magnetism with special relativity--1963 Purcell's explanation of magnetism as a result of Lorentz contraction ofspace along the direction of a current is a welcome relief from theconvoluted descriptions in this book. Mathematical notation is rendered using "programming" notation.^ Power--Exponential; A^3 means "A cubed"* Multiply/ Divide+ Add- Subtract( ) Precedence--Perform before enclosing expression2E6 Scientific Notation (2, 000, 000) A---------------------4. 452 X 10^12 X t is rendered as A / ( 4. 452E12 * t ) Where the rendering of a mathematical expression is in doubt, an imageof the original text is included. Here are some definitions absent from the text. Foucault currents. Eddy currents. inspissate To thicken, as by evaporation. riband Ribbon. sapotaceous Order Sapotace[ae] of trees and shrubs, including the star apple, the Lucuma, or natural marmalade tree, the gutta-percha tree (Isonandra), and the India mahwa, as well as the sapodilla, or sapota, after which the order is named. Don Kostuch, MS, Electrical Engineering. [End Transcriber's notes. ] WORKS OFT. O'CONOR SLOANE, A. M. , E. M. , Ph. D. ARITHMETIC OF ELECTRICITYA MANUAL OF ELECTRICAL CALCULATIONSBY ARITHMETICAL METHODS. Third Edition. Illustrated. $1. 00. It is very useful to that class of readers to whom Algebra is acomparatively unknown quantity, and will meet its wantsadmirably. --Electrical World. ELECTRICITY SIMPLIFIED. A POPULAR TREATMENT OF THE SUBJECT. Illustrated. $1. 00. We especially recommend it to those who would like to acquire a popularidea of the subject. --Electric Age. ELECTRIC TOY MAKING. FOR AMATEURS. INCLUDING BATTERIES, MAGNETS, MOTORS, MISCELLANEOUS TOYS, AND DYNAMO CONSTRUCTION. Fully Illustrated. $1. 00. THE STANDARD ELECTRICAL DICTIONARY. A POPULAR DICTIONARY OF WORDS AND TERMSUSED IN THE PRACTICE OF ELECTRICAL ENGINEERING. BYT. O'CONOR SLOANE, A. M. , E. M. , Ph. D. NEW YORKGEORGE D. HURSTPUBLISHER Copyright 1892byNORMAN W. HENLEY & CO. PREFACE The purpose of this work is to present the public with a concise andpractical book of reference, which it is believed will be appreciated inthis age of electricity. The science has expanded so much that thelimits of what may be termed strictly a dictionary of the present daywould a few years ago have sufficed for an encyclopedia. It follows thatan encyclopedia of electricity would be a work of great size. Yet adictionary with adequate definitions, and kept within the closest limitsby the statement of synonyms, and by the consigning of all theinnumerable cross-references to a concise index will be far more than amere dictionary in the ordinary sense of the term. Duplication of matter is to be avoided. This makes many definitionsappear short. Yet, by the assistance of the reader's own generalknowledge, and by referring to the very complete index, almost anysubject can be found treated in all its aspects. There are exceptions tothis statement. So much has been done in the way of mechanical detail, so many inventions in telegraphy and other branches have sprung intoprominence only to disappear again, or to be modified out ofrecognition, that to embody descriptions of many ingenious andcomplicated apparatus has been absolutely impossible for want of space. A word as to the use of the book and the system of its construction maybe given here. Each title or subject is defined once in the text. Wherea title is synonymous with one or more others the definition is onlygiven under one title, and the others appear at the foot of the articleas synonyms. It may be that the reader is seeking the definition of oneof these synonyms. If so a reference to the index shows him at once whatpage contains the information sought for. The use of an index in a work, necessarily of an encyclopedic form, will be appreciated by all users ofthis book. vi PREFACE. Where a title embraces several words, all orders of the words will becited in the index. To make the operation of finding references easythis rule has been carried out very fully. It is customary to regard electricity as a growing science. It isunquestionably such, but the multiplication of terms and words is nownot nearly so rapid as it has been, and the time for the compiling of awork of this character seems most propitious. It is hoped that thepublic will indulgently appreciate the labor it has entailed on allconcerned in its production. SYMBOLS AND ABBREVIATIONS. adj. Adjective. V. Verb. Q. V. "Which see. '/ A mark of division, as A/B, meaning "A divided by B. ". /. The same as above. [Transcriber's note: / will be substituted for this divide symbol. ]= A mark of equality, meaning "is equal to. "X A mark of multiplication, meaning "multiplied by. " [Transcriber's note: * will be substituted for this divide symbol. ] Fractional exponents indicate the roots expressed by their denominatorsand the powers expressed by their numerators. Thus, A^1/2 means the"square root of A;" A^1/3 means the "cube root of A;" B^3/2 means the"square root of the cube or third power of B. " The use of powers of ten, as 10^10, 10^11, as multipliers, will be foundexplained at length in the definition "Ten, Powers of. " vii STANDARD ELECTRICAL DICTIONARY A. Abbreviation for anode, employed in text relating toelectro-therapeutics. It is sometimes written An. Abscissa. In a system of plane co-ordinates (see Co-ordinates) thedistance of any point from the axis of ordinates measured parallel tothe axis of abscissas. In the cut the abscissa of the point a is the line or distance a c. Fig. 1. AXES OF CO-ORDINATES. Absolute. Adj. In quantities it may be defined as referring to fixed units of quantity, and it is opposed to "relative, " which merely refers to the relation ofseveral things to each other. Thus the relative resistance of one wiremay be n times that of another; its absolute resistance might be 5 ohms, when the absolute resistance of the second wire would be 5/n ohms. Agalvanometer gives absolute readings if it is graduated to read directlyamperes or volts; if not so graduated, it may by "calibration" q. V. Bemade to do practically the same thing. 8 STANDARD ELECTRICAL DICTIONARY. Absolute Measurement. Measurement based upon the centimeter, gram, and second. (SeeCentimeter-Gram-Second System. ) Absolute Temperature. Temperature reckoned from absolute zero (see "Zero, Absolute"). It isobtained by adding for the centigrade scale 273, and for the Fahrenheitscale 459, to the degree readings of the regular scale. Absorption, Electric. A property of the static charge. When a Leyden jar is being charged itdilates a little and the capacity increases, so that it can take alittle more charge for a given potential difference existing between itstwo coatings. This phenomenon occurs with other static condensers, varying in degree with the dielectric. With shellac, paraffin, sulphurand resin, for instance, the absorption is very slight; withgutta-percha, stearine, and glass, the absorption is relatively great. The term is due to Faraday. Iceland spar seems almost or quite destituteof electric absorption. A. C. C. Symbol of or abbreviation for "anodic closure contraction" q. V. Acceleration. The rate of change of velocity. If of increase of velocity it ispositive; if of decrease, it is negative. It can only be brought aboutby the exercise of force and is used as the measure of or as determiningthe unit of force. It is equal to velocity (L/T) imparted, divided bytime (T); its dimensions therefore are L/(T^2). The c. G. S. Unit ofacceleration is one centimeter in one second. [Transcriber's note: The unit of acceleration is "centimeters per secondper second. "] Accumulator. (a) A term sometimes applied to the secondary or storage battery. (SeeBattery, Secondary. )(b) See Accumulator, Electrostatic(c) See Accumulator, Water Dropping. (d) See Wheel, Barlow's Accumulator, Electrostatic. Two conducting surfaces oppositely placed, and separated by adielectric and arranged for the opposite charging of the two surfaces, constitute an accumulator, sometimes termed a condenser. As thisarrangement introduces the element of a bound and of a binding charge, the electrostatic capacity of such is greater than that of either or ofboth of its component surfaces. The thinner the dielectric whichseparates the conducting surfaces, and the larger the surfaces thegreater is the capacity; or the less will be the potential differencewhich a given charge will establish between its two coatings. The natureof the dielectric also determines its capacity. (See Capacity, SpecificInductive. ) 9 STANDARD ELECTRICAL DICTIONARY. Fig. 2. SIR WILLIAM THOMSON'S WATER-DROPPING ACCUMULATOR. Accumulator, Water Dropping. This is also known as Sir William Thomson's Water-Gravity ElectricMachine. It is an apparatus for converting the potential energy offalling water drops, due to gravity, into electric energy. Referring tothe illustration, G represents a bifurcated water pipe whose two faucetsare adjusted to permit a series of drops to fall from each. C and F aretwo metallic tubes connected by a conductor; E and D are the same. TwoLeyden jars, A and B, have their inner coatings represented by strongsulphuric acid, connected each to its own pair of cylinders, B to D andE, and A to F and C. The outer coatings are connected to earth, as isalso the water supply. One of the jars, say A, is charged interiorilywith positive electricity. This charge, C and F, share with it, being inelectric contact therewith. Just before the drops break off from the jetleading into C, they are inductively charged with negative electricity, the positive going to earth. Thus a series of negatively excited dropsfall into the metal tube D, with its interior funnel or drop arrester, charging it, the Leyden jar B, and the tube E with negative electricity. This excitation causes the other stream of drops to work in the converseway, raising the positive potential of F and C and A, thus causing theleft-hand drops to acquire a higher potential. This again raises thepotential of the right-hand drops, so that a constant accumulatingaction is kept up. The outer coatings of the Leyden jars are connectedto earth to make it possible to raise the potential of their innercoatings. In each case the drops are drawn by gravity into contact withobjects similarly excited in opposition to the electric repulsion. Thisovercoming of the electric repulsion is the work done by gravity, andwhich results in the development of electric energy. 10 STANDARD ELECTRICAL DICTIONARY. Acidometer. A hydrometer or areometer used to determine the specific gravity ofacid. They are employed in running storage batteries, to determine whenthe charging is completed. (See Areometer. ) Aclinic Line. A terrestrial element; the locus on the earth's surface of noinclination of the magnetic needle; the magnetic equator. (See MagneticElements. ) Acoustic Telegraphy. The system of sound-reading in telegraphy, universally used in the Morsesystem. The direct stroke of the armature of the electro-magnet and its"back stroke" disclose to the ear the long and short strokes, dots andlines, and long and short spaces as produced by the dispatcher of themessage. In the Morse system a special magnet and armature is used toproduce the sound called the "sounder;" in other systems, e. G. , Steinheil's and Bright's apparatus, bells are used. (See Alphabets, Telegraphic. ) Acoutemeter. A Hughes audiometer or sonometer applied to determining the quality of aperson's hearing (See Hughes' Induction Balance, --Audiometer). Thecentral coil by means of a tuning fork and microphone with batteryreceives a rapidly varying current tending to induce currents in theother two coils. Telephones are put in circuit with the latter and pickup sound from them. The telephones are applied to the ears of the personwhose hearing is to be tested. By sliding the outer coils back and forththe intensity of induction and consequent loudness of the sounds in thetelephones is varied. The position when the sounds grow so faint as tobe no longer audible, gives the degree of delicacy of the person'shearing. By using a single telephone the same apparatus affords a meansof testing the relative capacity of the right and left ears. 11 STANDARD ELECTRICAL DICTIONARY. Actinic Rays. The rays of light at the violet end of the spectrum; also the invisiblerays beyond such end, or the ether waves of short periods which moststrongly induce chemical change. Actinism. The power possessed by ether waves of inducing chemical change, eitherof decomposition or of combination. The violet and ultra-violet end ofthe spectrum of white light, generally speaking, represent the mosthighly actinic rays. Actinometer, Electric. Properly an apparatus for measuring the intensity of light by its actionupon the resistance of selenium. A current produced by fixedelectro-motive force passing through the selenium affects a galvanometermore or less according to the intensity of the light. It is moreproperly an electric photometer. The term has also been applied to acombination of a thermo-electric pile and galvanometer, the lightfalling on the pile affecting the motions of the galvanometer. Action, Local. (a) The wasteful oxydation of the zinc in a galvanic battery due tolocal impurities and variations in the composition of the zinc. Theseact to constitute local galvanic couples which cause the zinc todissolve or oxydize, without any useful result. Amalgamation of the zincprevents local action. Chemically pure zinc is also exempt from localaction, and can be used in an acid battery without amalgamation. (SeeAmalgamation. ) (b) The same term has been employed to indicate the eddy or foucaultcurrents in dynamo electric machines. (Sec Current, Foucault. ) Activity. The rate of doing work; the work done per second by any expenditure ofenergy. The activity of a horse-power is 550 foot lbs. Per second, or746 volt-coulombs per second. The practical electric unit is thevolt-ampere, often called the watt. (Sec Energy, Electric. ) Adapter. A screw coupling to engage with a different sized screw on each end; oneof the uses is to connect incandescent lamps to gas-fixtures. A. D. C. Abbreviation for Anodic Duration Contraction, q. V. ; a term inelectro-therapeutics. Adherence, Electro-magnetic. The adherence between surfaces of iron due to elcctro-magneticattraction. It has been applied to the driving-wheels of an engine andrail, whose grip is increased by such action. In one method a deepgroove was cut around the wheel which was wound with a magnetizing coil. Thus one rim becomes a north and the other a south pole, and the railcompleting the circuit acts as the armature. Such an arrangementprevents a wheel from sliding. Electro-magnetic adherence has also beenemployed to drive friction gear wheels. In one arrangement the twowheels are surrounded by a magnetizing coil, under whose induction eachattracts the other, developing high adherence between their peripheries. 12 STANDARD ELECTRICAL DICTIONARY. Fig. 3. ELECTRO-MAGNETIC CAR WHEEL. Fig. 4. ELECTRO-MAGNETIC FRICTION GEAR. Admiralty Rule of Heating. The British Admiralty specifications for the permissible heating ofdynamos. It holds that at the end of a run of six hours no part of thedynamo under trial shall show a rise of temperature greater than 11º C. (20º F. ) above the temperature of the air surrounding it. This isthought to be a very stringent and unnecessarily high requirement. Aerial Conductor. An electric conductor carried from housetops, poles, or otherwise so asto be suspended in the air, as distinguished from an underground orsubmarine conductor. Affinity. The attraction of atoms and in some cases perhaps of molecules for eachother by the force of chemical attraction. When the affinity is allowedto act or is carried out, a chemical change, as distinguished from aphysical or mechanical change, ensues. Thus if sulphur and iron are eachfinely powdered and are mixed the change and mixture are mechanical. Ifslightly heated the sulphur will melt, which is a physical change. Ifheated to redness the iron will combine with the sulphur forming a newsubstance, ferric sulphide, of new properties, and especiallycharacterized by unvarying and invariable ratios of sulphur to iron. Such change is a chemical one, is due to chemical affinity, is due to acombination of the atoms, and the product is a chemical compound. 13 STANDARD ELECTRICAL DICTIONARY. Agir Motor. The Anderson and Girdlestone motor. The term "agir" is made up from thefirst portions of each name. Agonic Line. The locus of points on the earth's surface where the magnetic needlepoints to the true north; an imaginary line determined by connectingpoints on the earth's surface where the needle lies in the truegeographical meridian. Such a line at present, starting from the northpole goes through the west of Hudson's Bay, leaves the east coast ofAmerica near Philadelphia, passes along the eastern West Indies, cutsoff the eastern projection of Brazil and goes through the South Atlanticto the south pole. Thence it passes through the west of Australia, theIndian Ocean, Arabia, the Caspian sea, Russia and the White sea to theNorth Pole. It crosses the equator at 70° W. And 55° E. Approximately. (See Magnetic Elements. ) Synonym--Agone. [Transcriber's note: The file Earth_Declination_1590_1990. Gif providedby the U. S. Geological Survey (http://www. Usgs. Gov) is an animation ofthe declination of the entire earth. ] Air. Air is a dielectric whose specific inductive capacity at atmospherepressure is taken as 1. It is practically of exactly the samecomposition in all places and hence can be taken as a standard. When dryit has high resistance, between that of caoutchouc and dry paper. Dampness increases its conductivity. It is a mixture of oxygen and nitrogen, with a little carbonic acid gasand other impurities. Its essential composition is: Oxygen: (by weight) 23. 14 (by volume) 21Nitrogen: 76. 86 79 The specific inductive capacity varies for different pressures thus: Approximate vacuum (. 001 mm. , . 0004 inch) 0. 94 (Ayrton) " " ( 5 mm. , . 2 inches ) 0. 9985 (Ayrton) 0. 99941 (Boltzman. ) The specific gravity of air under standard conditions 15. 5° C (60° F. )and 760 mm. Barometric pressure (30 inches) is taken as unity as astandard for gases. [Transcriber's note: Argon accounts for 0. 9340%. It was discovered in1894, two years after this book. ] Air-Blast. (a) In the Thomson-Houston dynamo an air-blast is used to blow away thearc-producing spark liable to form between the brushes and commutator. It is the invention of Prof. Elihu Thomson. The air is supplied by apositive action rotary blower connected to the main shaft, and driventhereby. The wearing of the commutator by destructive sparking is thusprevented. A drum H H is rotated, being mounted on the axis X of the dynamo. As itrotates the three vanes are thrown out against the irregular shapedperiphery of the outer case T T. The arrow shows the direction ofrotation. The air is thus sent out by the apertures a a. O is theoil-cup. (b) The air-blast has also been used by Prof. Thomson in experimentswith high frequency currents of high potential. By directing a blast ofair against a spark discharge between ball terminals of an alternatingcurrent, the nature of the current was changed and it became capable ofproducing most extraordinary effects by induction. 14 STANDARD ELECTRICAL DICTIONARY. Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO. Air Condenser. A static condenser whose dielectric is air. The capacity of an aircondenser in farads is equal to A / ( 4. 452E12 * t )in which A is the area of one sheet or sum of the areas of one set ofconnected sheets in square inches and t is the thickness of the layer ofair separating them. A convenient construction given by Ayrton consists in a pile of glassplates P separated by little bits of glass F of known thickness, threefor each piece. Tin-foil T is pasted on both sides of each piece ofglass and the two coatings are connected. The tin-foil on each secondplate is smaller in area than that on the others. The plates areconnected in two sets, each set comprising every second plate. For A inthe formula the area of the set of smaller sheets of tin-foil is taken. By this construction it will be seen that the glass does not act as thedielectric, but only as a plane surface for attachment of the tin-foil. Posts E E keep all in position. One set of sheets connects with thebinding post A, the other with B. The capacity of any condenser with a dielectric of specific inductivecapacity i is given by the formula: ( i *A^1 ) / ( 4. 452E12 * t1 ) The air condenser is used for determining the value of i for differentdielectrics. Fig. 6. AIR CONDENSER. 15 STANDARD ELECTRICAL DICTIONARY. Air Gaps. In a dynamo or motor the space intervening between the poles of thefield magnet and the armature. They should be of as small thickness, andof as extended area as possible. Their effect is to increase themagnetic reluctance of the circuit, thereby exacting the expenditure ofmore energy upon the field. They also, by crowding back the potentialdifference of the two limbs, increase the leakage of lines of force fromlimb to limb of the magnet. Air Line Wire. In telegraphy the portion of the line wire which is strung on poles andcarried through the air. Air Pump, Heated. It has been proposed to heat portions of a mercurial air pump to securemore perfect vacua, or to hasten the action. Heating expands the air andthus produces the above effects. 16 STANDARD ELECTRICAL DICTIONARY. Air Pump, Mercurial. An air pump operated by mercury. The mercury acts virtually as thepiston, and the actuating force is the weight of the column of mercury, which must exceed thirty inches in height. There are many types. Mercurial air pumps are largely used for exhausting incandescent lampchambers. (See Geissler Air Pump, --Sprengel Air Pump. ) Air Pumps, Short Fall. A mercurial air pump in which the fall of mercury or the height of theactive column is comparatively small. It is effected by using severalcolumns, one acting after the other. A height of ten inches for eachcolumn suffices in some forms. Enough columns must be used in successionto make up an aggregate height exceeding 30 inches. Fig. 7. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Fig. 8. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Alarm, Burglar. A system of circuits with alarm bell extending over a house orapartments designed to give notice of the opening of a window or door. As adjuncts to the system the treads of the stairs are sometimesarranged to ring the bell, by completing a circuit when trod on. Doormats are also arranged to close circuits in like manner. 17 STANDARD ELECTRICAL DICTIONARY. For doors and windows switches are provided which are open as long asthe door or window is closed, but which, on being released by openingthe door or windows, automatically close the circuit. The circuitincludes an alarm bell and battery, and the latter begins to ring andcontinues until stopped, either by the closing of the door or by aswitch being turned. The connections are sometimes so contrived that thereclosing of the door or window will not stop the bell from ringing. The cuts show various switches for attachment to doors and windows. Itwill be seen that they normally keep the circuit closed, and that it isonly open when pressure, as from a closed door, is brought upon them. Inthe case of a door a usual place for them is upon the jamb on the hingeside, where they are set into the wood, with the striking pinprojecting, so that as the door is closed the pin is pressed in, thusbreaking the circuit. Sometimes the connections are arranged so as to switch on the electriclights if the house is entered. Special annunciators showing where thehouse has been entered are a part of the system. A clock which turns thealarm on and off at predetermined hours is also sometimes used. The circuits may be carried to a central station or police station. Oneform of burglar alarm device is the Yale lock switch. This is a contactattached to a Yale lock which will be closed if the wrong key is used, completing a circuit and ringing a bell. Fig. 9. BURGLAR ALARM SWITCH OR CIRCUIT BREAKER. Alarm, Electric. An appliance for calling attention, generally byringing a bell. It is used to notify of water-level in boilers or tanks, of entrance of a house, or of other things as desired. It is evidentthat any number of alarms could be contrived. 18 STANDARD ELECTRICAL DICTIONARY. Alarm, Fire and Heat. An alarm for giving notice of the existence of a conflagration. Such aresometimes operated by a compound bar thermostat (see Thermostat), whichon a given elevation of temperature closes a circuit and rings anelectric bell. Sometimes the expansion of a column of mercury whenheated is used. This, by coming in contact with one or two platinumpoints, completes a circuit, and rings the bell. The identical apparatus may be used in living rooms, greenhouses. Factories and elsewhere, to give an alarm when the temperature rises orfalls beyond predetermined limits. Alarm, Overflow. An alarm to indicate an overflow of water has been suggested on thelines of a contact completed by water, or of the elements of a batterywhich would be made active by water. Thus two sheets of metal might beseparated by bibulous paper charged with salt. If these sheets wereterminals of a circuit including a bell and battery, when water reachedthem the circuit would be closed and the bell would ring. It was alsoproposed to use one copper and one zinc sheet so as to constitute abattery in itself, to be thrown into action by moisture. These contactsor inactive batteries could be distributed where water from an overflowwould be most likely to reach them. Alarm, Water Level. An alarm operated by a change of water level in a tank or boiler. By afloat a contact is made as it rises with the water. Another float may bearranged to fall and close a contact as the level falls. The closing ofthe contacts rings an electric bell to notify the attendant in charge. Alcohol, Electrical Rectification of. A current of electricity passed through impure alcohol between zincelectrodes is found to improve its quality. This it does by decomposingthe water present. The nascent hydrogen combines with the aldehydes, converting them into alcohols while the oxygen combines with the zincelectrode. Alignment. The placing in or occupying of the same straight line. The bearings of ashaft in dynamos, engines, and other machinery have to be in accuratealignment. Allotropy. The power of existing in several modifications possessed by somesubstances, notably by chemical elements. Instances of the allotropicstate are found in carbon which exists as charcoal, as graphite(plumbago or black lead), and as the diamond. All three are the sameelemental substance, although differing in every physical and electricalproperty. 19 STANDARD ELECTRICAL DICTIONARY. Alloy. A mixture, produced almost universally by fusion, of two or more metals. Sometimes alloys seem to be chemical compounds, as shown by their havinggenerally a melting point lower than the average of those of theirconstituents. An alloy of a metal with mercury is termed an amalgam. Animportant application in electricity is the use of fusible alloys forfire alarms or for safety fuses. German silver is also of importance forresistance coils, and palladium alloys are used for unmagnetizablewatches. An alloy of wrought iron with manganese is almostunmagnetizable, and has been proposed for use in ship building to avoiderrors of the compass. Alloys or what are practically such can be deposited by electrolysis inthe electro- plater's bath. We give the composition of some alloysinteresting to the electrician. Solder: Lead 1 part Tin 2 parts " " " 1 " " " " 2 " German Silver: Copper, 2 parts; Nickel, 1 part; Zinc, 1 part (used for resistances). Platinum, Silver Alloys: Platinum, 1 part; silver, 2 parts (used for resistances. ) Palladium alloys for watch springs. (See Palladium. ) Alphabet, Telegraphic. The combinations of sounds, of dots and dashes marked on paper, ofright-hand and left-hand deflections of a needle, of bells of differentnotes, or of other symbols by which a fixed combination is expressed foreach character of the alphabet, for numerals, and for punctuation. Whilethe code is designed for telegraphic uses it can be used not only forthe conveyance of signals and messages by the electrical telegraphs, butalso by any semaphoric or visual system, as by flashes of light, movements of a flag or even of the arms of the person signalling. In the English and continental needle telegraphy in which the message istransmitted by the movements of an index normally vertical, butoscillating to one side or the other under the influence of the current, the latter being controlled by the transmitter of the message, the lefthand swings of the needle are interpreted as dots, the right hand asdashes. This system enables one alphabet to be translated into the other, orvirtually one alphabet answers for both Morse and needle transmitters. There are two principal telegraphic alphabets, the American Morse andthe International codes. They are very similar, their essentialdistinction being that spaces are used in the American code, while theyare excluded from the International code. In the American Morse system the message is now universally received bysound. (See Sounder--Sound Reading. ) 20 STANDARD ELECTRICAL DICTIONARY. The two codes or telegraphic alphabets are given here. THE INTERNATIONAL ALPHABET. Parenthesis, - . - - . - Understand, ... - . I don't understand, .. -- .... --.. Wait, . -. . . Erase, ... ... ... Call signal, -. -. -. - End of message, . -. -. -. Cleared out all right, . -.. -.. -. A . - L . -.. W . -- B -... M -- X -.. - C -. -. N -. Y -. -- D -.. O --- Z --.. E . P . --. F .. -. Q --. - Ch ---- G --. R . -. Ä . -. - H .... S ... Ö ---. I .. T - Ü .. -- J . --- U .. - É .. -.. K -. - V ... - Ñ --. -- NUMERALS 1 . ---- 4 .... - 8 ---.. 2 .. --- 5 ..... 9 ----. 3 ... -- 6 -.... 0 ----- 7 --... [Transcriber's note: The original image of the dot/dash pattern is somewhatambiguous. Since there may be differences from contemporary specifications, the original image is included. ] [Image of page 20: THE INTERNATIONAL ALPHABET. ] 21 STANDARD ELECTRICAL DICTIONARY. PUNCTUATION, ETC. , Period (. ) ... ... Comma (, ) . -. -. - Query(?) .. --.. Exclamation (!) --.. -- Apostrophe (') . ----. Hyphen (-) -.... - Fresh paragraph, . -. -.. Inverted commas, -.. -. THE AMERICAN ALPHABET. A . - L ----(Continuous) W . -- B -... M -- X . -.. C .. S. N -. Y .. S.. D -.. O . S. Z …. E . P ..... F . -. Q .. -. Ch ---- G --. R . S.. Ä . -. - H .... S ... Ö ---. I .. T - Ü .. -- J - . - . U .. - É .. -.. K -. - V ... - Ñ --. -- NUMERALS 1 . --. 4 .... - 8 -.... 2 .. -.. 5 --- 9 -.. - 3 ... -. 6 ... ... 0 -----(Continuous) 7 --.. [Transcriber's Note: The "s" in the American Code indicates a "space". Ileave the following to the reader's imagination. See the originalimage. ] Comma (, )Semicolon (;)Colon (:)Colon Dash (:~)Period (. )Interrogation (?)Exclamation (!)Dash (-)Hyphen (-)Pound Sterling (£)Shilling Mark ( ) [Image of page 21: THE AMERICAN ALPHABET. ] 22 STANDARD ELECTRICAL DICTIONARY. [Transcriber's Note: I leave these to the reader's imagination. See thefollowing original image. ] Dollars ($)Decimal Point (. )Cents (c)Paragraph ()Pence (d. )Fractional Mark (--)Capitalized LetterItalics or UnderlineColon followed by Quotation :"Parenthesis ( )Brackets [ ]Quotation Marks " "Quotation within a Quotation " ' ' " [Image of page 22: THE AMERICAN ALPHABET. ] The principal differences in the two codes are the use of spaces in theAmerican code, such being excluded from the International code. Thisaffects the letters C, R, Y, & Z. The following diagram, due to Commandant Perian, enables the lettercorresponding to an International code sign to be rapidly found with theexception of R. <- dot start dash -> / \ E T / \ / \ I A N M / \ / \ / \ / \ S U R W D K G O / \ / \ / \ / \ / \ / \ / \ / \H V F U L A P J B X C Y Z Q Ô CH Fig. 10. Diagram for translating the Morse Alphabet. In order to find what letter corresponds to a given sign, starting fromthe top of the diagram, each line is traced down to a bifurcation, taking the right hand line of each bifurcation for a dash, and the lefthand line for a dot, and stopping when the dots and dashes are used up. Thus, for example, the signal -. - - leads us to the letter d, the signal - - - - to the letter j and so on. 23 STANDARD ELECTRICAL DICTIONARY. Alternating. Adj. Term descriptive of a current changing periodically indirection. (See Current, Alternating. ) Synonyms--Oscillatory--periodic--undulatory--harmonic. Alternating Current Arc. The arc produced by the alternating current. It presents severalpeculiarities. With an insufficient number of alternations per second itgoes out. As the carbons wear away equally it is adopted for such lampsas the Jablochkoff candle, (see Candle, Jablochkoff). As no crater isformed the light is disseminated equally both up and down. For thisreason to get full downward illumination a reflector is recommended. Alternating Current System. A system of electric distribution employing the alternating current. Fortransmission in the open air or in conduits a high potential circuit isused, from 1, 000 to 10, 000 volts being maintained at the centralstation. Two leads unconnected at the end lead from the station. Wherecurrent is desired a converter or transformer (see Converter) is placed, whose primary is connected to the two leads bridging the intervalbetween them. From the secondary the house leads are taken with aninitial potential in some cases of 50 volts. The converters are thus allplaced in parallel. By law or insurance rules the converters aregenerally kept outside of buildings. Where no secondary current is takenfrom the converters very little primary current passes them on accountof their counter-electromotive force. As more secondary current is takenthe primary increases and this accommodation of one to the other is oneof the interesting and valuable features. Street lamps are sometimesconnected in series. Each lamp in such case is in parallel with a smallcoil with iron core. While the lamp is intact little current passesthrough the coil. If the lamp is broken, then the converter impedes thecurrent by its spurious resistance, q. V. , just enough to represent andreplace the resistance of the extinguished and broken lamp filament. (See Meter, Alternating Current; Motor, Alternating Current. ) Alternation. The change in direction of a current. The number of such changes isexpressed as number of alternations; thus a current may have a frequencyof 500 or 20, 000 alternations per second. [Transcriber's note: One alternation per second is now called one hertz. ] Alternation, Complete. A double alternation; a change from one directionto the other and back again to the original phase. A symbol derived fromits graphic representation by a sine curve is used to indicate it. Thesymbol is ~ 24 STANDARD ELECTRICAL DICTIONARY. Alternative Path. A second path for a current appearing as a disruptivedischarge. Where two paths are offered the discharge, as it is ofalternating or oscillatory type, selects the path of leastself-induction. Thus a thick bar of copper, with no air gap, may beabandoned by the current in favor of a small iron wire with an air gap, but which has less self-induction. The lightning arresters, q. V. , for the protection of telegraph officesare sometimes based on these principles. A path of very high resistancebut of small self-induction is offered between the line and the earth. This the lightning discharge selects in preference to the instrumentswith their iron cores, as the latter are of very high self-induction. Alternator. A dynamo electric generator supplying an alternating current. (SeeDynamo, Alternating Current. ) Synonym--Alternating current generator or dynamo. Alternator, Constant Current. An alternating current dynamo supplying a current of unvarying virtualamperage. Alternators of this type are constructed with an armature ofhigh self-induction. Sometimes fine winding contained in deep peripheralnotches in the core-discs is employed to magnify the self-induction. Such generators are employed for series lighting, especiallyarc-lighting. Aluminum. A metal; one of the elements; symbol: Al. Atomic weight: 27. 4. Equivalent: 9. 13. Valency: 3. Specific gravity: 2. 6. It is a conductor of electricity. Relative resistance annealed, (Silver = 1) 1. 935Specific resistance at 0ºC (32°F. ) 2. 912 microhms Resistance of a wire at 0ºC (32°F. )a) 1 foot long, weighing 1 grain, 0. 1074 ohms. B) 1 foot long, 1/1000 inch thick, 17. 53 "c) 1 meter long, weighing 1 gram, 0. 0749 "d) 1 meter long, 1 millimeter thick 0. 03710 "Resistance of a 1-inch cube at 0ºC (32°F. ) 1. 147 microhmsElectro-chemical equivalent. . 0958 (hydrogen == . 0105) 25 STANDARD ELECTRICAL DICTIONARY. Amalgam. (a) A combination or alloy in which one of the constituents is mercury. Usually the term is applied to an alloy of a single metal with mercury. Some metals readily form amalgams; such metals are: Gold, zinc, silver, lead and others; some, such as platinum and iron, form amalgams onlyunder exceptional circumstances. (b) The word is also applied to compositions for application to thecushions of frictional electric machine in which cases it is often amisnomer. True amalgams used for this purpose are made as follows: (a) Tin, 1 part; Zinc, 1 part; Mercury, 2 parts (Kienmayer). (b) Tin, 2 parts; Zinc, 3 parts. (c) Tin, 3 parts; Zinc, 5 parts; Mercury, 4 parts. (d) Zinc, 1 part: Mercury, 4 parts; Mercury, 9 parts. [sic] The tin, if such is used, (formula a, b and c) is first melted, the zincis added in successive portions. The mercury, which must be heated, isslowly poured into the melted alloy after removal of the latter from thefire, and the mixture, while making, is constantly stirred. It is keptstirred or rubbed in a mortar until cold. Sometimes it is poured intowater and kept in constant agitation until cold. It is thus obtained ina granular condition, and is pounded in a mortar until reduced topowder. It must be dried and kept in tightly stopped bottles and isapplied to the cushions after they have been greased. It is to benoticed that it is said that alloy (d) requires no pulverization beyondconstant rubbing in a mortar as it cools. Sometimes the amalgam isshaken about in a wooden tray with chalk while cooling. The action ofamalgams is not very clearly understood. Some claim that there is achemical action, others that they simply act as conductors, others thatthey are more highly negative to the glass than the leather of thecushions. Graphite or sulphide of tin (mosaic gold) are sometimes used to coat thecushions; it is these that are sometimes incorrectly called amalgams. Amalgamation. The application of mercury to a metal with which it forms an amalgam, orwith which it amalgamates. Battery zincs are amalgamated in two ways. Inthe immersion method, the plate is dipped into an acid solution ofmercuric chloride or nitrate. The latter is best. In the directapplication method the plate is first wet all over with dilute acid anda little mercury is dropped upon it and is rubbed over the surface witha rag or, what is better, with a piece of galvanized iron. A very littlemercury answers the purpose. The whole surface of the plate should beleft as bright as silver. (See Action, Local. ) Amber. Amber is a fossil resin, supposed to be a product of the extinct PinitesSuccinifer and other coniferous trees. Most of it is gathered on theshores of the Baltic between Koenigsberg and Memel. It is also found insmall pieces at Gay Head, Mass. , and in New Jersey green sand. It isfound among the prehistoric remains of the Swiss Lake dwellers. Whenrubbed with a cloth it becomes excited with negative electricity. TheGreek word for it is electron, which gave the name electricity to themodern science. Thales of Miletus, 600 B. C. , and Theophrastus, about300 B. C. , both mention its electric properties or power of attractingsmall objects when rubbed. 26 STANDARD ELECTRICAL DICTIONARY. Ammeter. The commercial name for an ampere-meter, an instrument designedto show by direct reading the number of amperes of current which arepassing through a circuit. A great variety of ammeters have been invented, based on differentprinciples. The definitions following this one give some idea of thelines of construction followed. Synonym--Ampere meter. Ammeter, Ayrton's. A direct reading instrument for measuring current intensity. A solenoid receives the current. In the axis of the solenoid an irontube is suspended by a long spiral spring that passes down within it, and the upper end of which spring is fastened to the glass top of theinstrument. The tube is provided with proper guides so as to maintain avertical position, and is free to rotate. Its upper end carries anindex. The whole operates as a magnifying device. A slight longitudinaldisplacement of the tube causes it to rotate through a considerableangle by the action of the spring. By properly proportioning the parts, the angle of displacement of the index is directly proportional to thecurrent between 15º and 270º angular displacement. The same instrument is wound for use as a volt-meter. Its principal fault is its restricted range. Ammeter, Commutator. A commutator ammeter is one whose windings consist of separate strands, each of any desired number of turns, and provided with a commutatingattachment for throwing them into series or into parallel as desired. The essential condition is that all the wires shall be of equalresistance and of equal number of turns. Such an instrument can be usedfor heavy or light currents. Two sets of graduations are marked on itsscale if it is a calibrated instrument. (See Calibration. ) Commutatorvolt-meters are constructed on the same principle. Ammeter, Cunynghame's. A modification of the Siemens' electro-dynamometer. (SeeElectro-dynamometer, Siemens'. ) An electro-magnet with very massive coreis excited by the current. As the core is of small reluctance thestrength of the magnet is nearly proportional to the current strength. Between the poles of the magnet a soft iron armature or induced magnetis pivoted. It carries a pointer so adjusted that when the axis of thesoft iron magnet is at an angle of about 30º with the line joining thepoles of the electro-magnet the pointer will indicate zero. The soft iron armature is so massive that the magnetism induced in it isproportional to the strength of the electro-magnet. Hence the coupleexerted by the electro-magnet on the pivoted armature will beproportional to the square of the current. The armature is retained in place by a spiral spring lying in line withits axis of rotation. The instrument is operated as a zero readinginstrument. The current is passed through it. The needle is deflected;it is brought back to zero by turning a milled head which twists thespring. The current will be proportional to the square root of the angleof displacement of the milled head. A scale with index is provided, giving directly the square roots of the angle over which the pointer ismoved. The same instrument is wound for use as a volt-meter. 27 STANDARD ELECTRICAL DICTIONARY. Ammeter, Eccentric Iron Disc. This ammeter comprises a cylindrical electro-magnet excited by thecurrent to be measured. A disc of iron free to rotate is suspended onpivots below it. A piece is cut off the disc at one part of itsperiphery so as to give more metal to one side than to the other. In itszero position this portion of the disc swings towards the magnet. As thelatter is more and more excited the other or more projecting portion ofthe disc turns towards it, being attracted like an armature, and movesagainst the force of gravity, the disc rotating. An index attached tothe disc swings over the face of a graduated scale. The disc is socounterpoised that in its natural position the index points to zero. Ammeter, Electro-magnetic. An ammeter depending for its working upon the action of anelectro-magnet, which is excited by the current to be measured. Ammeter, Gravity. An ammeter whose hand or index is drawn into the zero position bygravity, and whose displacement therefrom is produced by the action ofthe current to be measured. Fig. 11. GRAVITY SOLENOID AMMETER. Ammeter, Magnetic Vane. A fixed plate of soft iron is placed within a coil. Facing it is asecond disc free to move or swing on an axis. When the field is excitedthe two repel each other because like polarity is induced in each, andthe motion of the movable disc indicates the strength of the current. The same instrument is wound for high resistance and constitutes aMagnetic Vane Voltmeter. 28 STANDARD ELECTRICAL DICTIONARY. Ammeter, Magnifying Spring. A solenoid ammeter in which a spiral spring is used to convert thelongitudinal motion of the armature or movable core into a rotary motion(see Ammeter, Ayrton's) and magnify the apparent range of motion. Ammeter, Permanent Magnet. An ammeter with a magnetic field produced by a permanent magnet. Ammeter, Solenoid. An ammeter in which the attraction, when a current is passing throughit, exerted by a hollow coil of wire upon an iron bar or tube in linewith its axis, is utilized to indicate the strength of current. The baris drawn into the coil to different extents proportional to theattraction. As an example see Ammeter, Ayrton's, and cut of GravityAmmeter. Ammeter, Spring. An ammeter in which the part moved by the current is controlled orbrought to the zero position by a spring. Ammeter, Steel Yard. A solenoid ammeter in which the solenoid core is suspended verticallyfrom the short end of a steel yard fitted with a sliding weight. Thecurrent passes through the solenoid coil and attracts or draws downwardsthe coil. A sliding weight is moved in and out on the long steel-yardarm which is graduated for amperes. In use the weight is slid out untilthe arm is in equipose; the divisions give the amperes. Fig. 12. STEEL YARD AMMETER. 29 STANDARD ELECTRICAL DICTIONARY. Ammunition Hoist, Electric. An apparatus for use on ships for hoisting ammunition to the guns by anelectric elevator. The characteristic feature of it is that a constantmotion of the switch or handle is required to keep it in action. If theoperator is shot so as to be incapacitated from taking charge of theswitch, the hoist stops until another is assigned to it. Amperage. Current intensity expressed in amperes, as an amperage of ten amperes. Ampere. The practical unit of electric current strength. It is the measure ofthe current produced by an electro-motive force of one volt through aresistance of one ohm. In electric quantity it is the rate of onecoulomb per second. It is one-tenth the absolute C. G. S. Unit ofcurrent strength. Its best analogy is derived from water. Assuming theelectric current to be represented by a current of water, the pressure, head, or descent producing such current would be the electro-motiveforce. The current might be measured in gallons (or other unit) passedper second. In the analogy these gallons would be coulombs. But it mightbe measured by reference to a standard stream, as for instance, thestream which would pass through a hole an inch square under a givenhead, say six inches of water. This unit is the miner's inch, and is theexact analogy of the ampere. A current of water may flow at the rate ofso many miner's inches, just as a current of electricity may flow at therate of so many amperes. In neither case it will be noted is there anyreference to time. "An ampere per second" is a redundant expression, andmeans no more than "an ampere"; an "ampere-second, " on the other hand, is a coulomb. The number of coulombs passed per second gives the amperesof current. For value of ampere, see Coulomb. [Transcriber's note: The SI definition of an ampere: A current in twostraight parallel conductors of infinite length and negligiblecross-section, 1 metre apart in vacuum, would produce a force equal to2E-7 newton per metre of length. ] Fig. 13. THE MINER'S INCH AS AN ANALOGY FOR THE AMPERE. 30 STANDARD ELECTRICAL DICTIONARY. Ampere, Arc. A conductor bent into the arc of a circle, and employed in measuring theelectric current by the electric balance. Ampere-currents. The currents assumed to be the cause of magnetism. (See Magnetism, Ampere's Theory of. ) Ampere-feet. The product of amperes of current by the length, in feet, of a conductorpassing such current. It may be in empiric calculations of dynamo ormotor construction, but is little used. One ampere-foot is a current ofone ampere passing through one foot length of a conductor, or one-tenthampere through ten feet, and so on. Ampere-hour. The quantity of electricity passed by a current of one ampere in onehour. It is used by electric power and lighting companies as the unit ofenergy supplied by them, because they maintain a constant potentialdifference in their leads, so that only the amperes and hours needmeasuring or recording to give the energy, viz. : volt-ampere-hours. The same unit is applied to batteries to indicate their potentialenergy, because they also are assumed to be of constant voltage orelectro-motive force. Ampere-meters. The product of amperes of current by the length, in meters, of aconductor carrying such current. One ampere-meter is a current of oneampere passing through one meter of a conductor. The term must not be confused with the identically spelled Ampere-meter, a synonym for Ammeter. Ampere-minute. The quantity of electricity passed by a current of one ampere in oneminute; sixty coulombs. Ampere Ring. A conductor forming a ring or circle used in electric balances formeasuring currents. (See Balance, Ampere. ) Ampere-second. The quantity of electricity passed by a current of one ampere in onesecond; the coulomb, q. V. Amperes, Lost. In a shunt or compound-wound dynamo, part of the total amperes ofcurrent produced in the armature coils go through the shunt, and hence, do not appear in the outer circuit. S. P. Thompson has proposed the term"lost amperes" for this portion of the current. Ampere's Memoria Technica. An expression of the effect of a current on a magnetic needle. If weimagine the observer in the line of the current and facing the magneticneedle, the current entering by his feet and leaving by his head, thenorth pole is deflected to his left. 31 STANDARD ELECTRICAL DICTIONARY. Ampere-turns. The amperes of current supplied to a magnet coil multiplied by thenumber of turns the current makes in the coil. If the coil is wound twoor three in parallel, the virtual turns by which the amperes aremultiplied are one-half or one-third the actual turns of wire. Synonym--Ampere Windings. Ampere-turns, Primary. The ampere-turns in the primary coil of an induction coil ortransformer. Ampere-turns, Secondary. The ampere-turns in the secondary coil of an induction coil ortransformer. Amplitude of Waves. Waves are distinguished by length and amplitude. The latter, in the caseof transverse waves, such as those of water and of the ether, correspondwith and measure the height from lowest to highest point, or from valleyto summit of the waves in question. In the case of longitudinal waves, such as those of the air, due to sounding bodies, the ratio of degree ofrarefaction to degree of condensation existing in the system is theamplitude. The latter can be graphically represented by a sinuous line, such as would represent the section of a transverse wave. Ether wavesare produced by heated bodies and by electro-magnetic impulses, as inthe discharge of the Leyden jar. The amplitude of a wave, other things being equal, is the measure of itsintensity. Thus, the louder a sound the greater is the amplitude of thesystem of waves to which it is due. The same applies to ether waves, whether they are perceived in the electro-magnetic, light, orheat-giving modification. As the amplitude of ether waves cannot beaccurately known, amplitude is a relative term and is not statedgenerally in any absolute unit. Analogous Pole. One of the elements of a pyro-electric crystalline substance, such astourmaline. When heated, such bodies acquire electrical properties. Ifof such crystalline form that they are differently modified at the endsof their crystalline axis, by hemihedral modifications, the ends may bedifferently affected. One end may show positive electricity when thetemperature is rising, and negative when falling. Such end is thencalled the analogous pole. The opposite end presents, in such cases, theopposite phenomena; becoming negative when the temperature is rising, and becoming positive when it is falling; such end is called theantilogous pole. Analysis. The determination of the elements of a case. It may be chemical, andconsist in finding what a substance consists of; it may be mathematical, and consist in determining the unknown quantities in a problem; or itmay belong to other branches of science. The term has a very extendedapplication. Where the constituents are only determined in kind it iscalled qualitative analysis; where their quantity or percentage isascertained it is called quantitative analysis. 32 STANDARD ELECTRICAL DICTIONARY. Analysis, Electric. Chemical analysis by electrolytic methods. (See Electrolytic Analysis. ) Analyzer, Electric. An apparatus used in investigations on electric ether waves. It consistsof a series of parallel metallic wires. When the electric waves havebeen polarized, the analyzer will only permit them to go through itintact, when the plane of vibration of the waves is parallel to itswires. Anelectrics. (a) Bodies which do not become electrified by friction; a termintroduced by Gilbert, now little used, as all bodies developelectricity under proper conditions by contact action; the reverse ofidioelectrtics. (b) Also a conductor of electricity, the reverse of a dielectric, q. V. (See Conductor. ) It will be seen that Gilbert's anelectrics were, after all, the same asthe modern anelectrics, i. E. , conductors. Anelectrotonus. A term used in medical electricity or electro-therapeutics to indicatethe deceased functional activity induced in a nerve by the proximity ofthe anode of an active electric circuit completed through the nerve. Theconverse of Kathelectrotonus. Angle of Declination. The angle of error of the magnetic needle or compass, measuring theextent of its deviation from the meridian in any locality. It is theangle between the plane of the magnetic axis of a magnetic needle freeto take its natural position, and the geographical meridian, the needlebeing counterpoised if necessary, so as to hold an absolutely horizontalposition. The deviation is expressed as being east or west, referringalways to the north pole. (See Magnetic Elements. ) Synonym--Variation of the Compass. [Transcriber's note: See Agonic Line. ] Angle of the Polar Span. In a dynamo or motor the angle subtended by the portion of a pole piecefacing the armature, such angle being referred to the centre of thecross-section of the armature as its centre. STANDARD ELECTRICAL DICTIONARY. 33 Angular Velocity. The velocity of a body moving in a circular path, measured withreference to the angle it passes over in one second multiplied by theradius and divided by the time. A unit angle is taken (57°. 29578 =57° 17' 44". 8 nearly) such that it is subtended by a portion of thecircumference equal in length to the radius. Hence, the circumference, which is 360°, is equal to 2*PI*unit angle, PI being equal to 3. 1416--. "Unit angular velocity" is such as would in a circle of radius = 1represent a path = 1, traversed in unit time = 1 second. If the radiusis r and the angle passed over is theta, the distance is proportional tor*theta; if this distance is traversed in t seconds the angular velocityis theta / t. The angular velocity, if it is multiplied by r, thetaexpressing a distance, will give the linear velocity. The dimensions ofangular velocity are an angle (= arc / radius) / a Time = (L/L)/T =(T^-1). The velocity expressed by the rate of an arc of a circle of unit radius, which arc subtends an angle of 57° 17' 44". 8, such arc being traversedin unit time, is unit angular velocity. Animal Electricity. Electricity, notably of high tension, generated in the animal system, inthe Torpedo, Gymnotus and Silurus. The shocks given by these fish aresometimes very severe. The gymnotus, or electric eel, was elaboratelyinvestigated by Faraday. It has the power of voluntarily effecting thisdischarge. There is undoubtedly some electricity in all animals. Thecontact of the spinal column of a recently killed frog with the lumbarmuscles produces contraction, showing electric excitement. Currents canbe obtained from nerve and muscle, or from muscle sides and muscle cuttransversely, in each case one thing representing positive and the othernegative elements of a couple. Angle of Inclination or Dip. The angle which the magnetic axis of a magnet, which magnet is free tomove in the vertical plane of the magnetic meridian, makes with ahorizontal line intersecting such axis. To observe it a specialinstrument, the dipping compass, inclination compass, dipping needle, ordipping circle, as it is called, is used. (See Elements, Magnetic, --Dipping Needle, --Compass, Inclination. ) Angle of Lag. The angle expressing the displacement of the magnetic axis of thearmature core of a dynamo in the direction of its rotation. (See Lag. )Lag is due to the motion of the armature core. Angle of Lead. The angle expressing the displacement in the direction of rotation ofthe armature of a dynamo which has to be given the brushes to compensatefor the lag. (See Lag. ) This is positive lead. In a motor the brushesare set the other way, giving a negative angle of lead or angle ofnegative lead. Anion. The electro-negative element or radical of a molecule, such as oxygen, chlorine or the radical sulphion. (See Ions. ) It is the portion whichgoes to the anode, q. V. , in electrolytic decomposition. 34 STANDARD ELECTRICAL DICTIONARY. Anisotropic. (adj. )Unequal in physical properties, as in conduction and specific inductivecapacity, along various axes or directions. An anisotropic conductor isone whose conductivity varies according to the direction of the current, each axis of crystallization in a crystalline body marking a directionof different conductivity. An anisotropic medium is one varying in likemanner with regard to its specific inductive capacity. In magnetism ananisotropic substance is one having different susceptibilities tomagnetism in different directions. The term is applicable to other thanelectric or magnetic subjects. Synonym--AEolotropic. Annealing, Electric. Annealing by the heat produced by the passage of the electric currentthrough the body to be annealed. The object is clamped or otherwisebrought into a circuit, and a current strong enough to heat it toredness, or to the desired temperature is passed through it. Annunciator. An apparatus for announcing a call from any place to another, as from aliving-room to an office in a hotel, or for announcing the entering ofany given room or window in a building protected by a burglar alarm. A usual system comprises for each annunciator an electro-magnet. Itsarmature is normally held away from its poles by a spring, and when inthat position a latch connected to the armature holds a little shutter. When by a push-button or other device a current is sent through acircuit which includes the electro-magnet the armature is attracted, this releases the latch and the shutter drops. In dropping it displays anumber, letter or inscription which indicates the locality of thepush-button or other circuit-closing device. Often annunciators areconnected in circuit with a bell. Fig. 14. ANNUNCIATOR. 35 STANDARD ELECTRICAL DICTIONARY. Annunciator Clock. A clock operating an annunciator by making contact at determined times. Annunciator Drop. The little shutter which is dropped by some forms of annunciators, andwhose fall discloses a number, character or inscription, indicatingwhence the call was sent. Fig. 15. DROP ANNUNCIATOR. Fig. 16. ANNUNCIATOR DETACHING MECHANISM. Annunciator, Gravity Drop. An annunciator whose operations release shutters which fall by gravity. Annunciator, Needle. A needle annunciator is one whose indications are given by the movementsof needles, of which there is usually a separate one for each place ofcalling. Annunciator, Swinging or Pendulum. An annunciator which gives its indications by displacing from itsvertical position a pendulum or vertically suspended arm. 36 STANDARD ELECTRICAL DICTIONARY. Anodal Diffusion. A term in electro-therapeutics; the introduction of a medicine into theanimal system by using a sponge-anode saturated with the solution of thedrug in question. On passing a current the desired result is secured bycataphoresis, q. V. Anode. The positive terminal in a broken metallic or true conducting circuit;the terminal connected to the carbon plate of a galvanic battery or toits equivalent in case of any other generator. In general practice it isrestricted to the positive terminal in a decomposition or electrolyticcell, such as the nickel anode in a nickel-plating bath or the anode ofplatinum in a gas voltameter. It is the terminal out of or from whichthe current is supposed to flow through the decomposition cell. Inelectro-therapeutics the term is used simply to indicate the positiveterminal. In an electrolytic cell the electro-negative substance oranion goes to the anode. Hence, it is the one dissolved, if either areattacked. The nickel, copper or silver anodes of the electroplaterdissolve in use and keep up the strength of the bath. The platinum anodein a gas voltameter is unattacked because the anion cannot act upon itchemically. Anodic Closure Contraction. A physiological change in a living subject produced by the closing ofthe electric current; the muscular contraction which takes place beneaththe anode applied to the surface of the body when the circuit is closed, the kathode being applied elsewhere; it is due, presumably, to directaction on the motor nerve. It is a term in electro-therapeutics. It isthe converse of anodic opening contraction, q. V. An abbreviation A. C. C. Is often used to designate it. Anodic Duration Contraction. A term in electro-therapeutics. On the opening or closing of an electriccircuit, the anode of which is placed over a muscle, a contraction isobserved (see Anodic Closure Contraction--Anodic Opening Contraction). The above term is used to designate the duration of such contraction. Anabbreviation A. D. C. Is often used to designate it. Anodic Opening Contraction. The converse of Anodic Closure Contraction, q. V. ; it is the contractionof living muscle beneath or near the anode where the circuit, includingsuch anode and the body in its course, is closed; a physiologicalphenomenon observed in electro-therapeutics to which branch of sciencethe term belongs. An abbreviation A. O. C. Is often used to designateit. Anodic Reactions. A term in electro-therapeutics; the diagnosis of disease by the actionsof the tissue near the anode of a circuit. Anti-Induction Conductor. A conductor constructed to avoid induction effects in the conductingelement. Many kinds have been made. A tubular metal shield or envelopewhich may be grounded will protect an enclosed conductor to some extent. Or the conductor may be a double wire twisted around itself, one branchbeing used for the regular and the other for the return circuit, thusconstituting a closed metallic circuit. The inductive effects are due tointerrupted or varying currents in neighboring wires and circuits. Manyanti-induction conductors have been invented and patented. 37 STANDARD ELECTRICAL DICTIONARY. Anti-magnetic Shield. In general terms a hollow screen of soft iron designed to protect anymass of steel behind or enclosed by it from magnetization by any magnetnear it, such as a dynamo field magnet. This it does by concentratingthe lines of force within its own mass, so that the space within it orenclosed by it is comparatively free from lines of force. It is oftenapplied to watches, and is virtually an iron case in which they areenclosed. Antimony. A metal, one of the elements, atomic weight, 122:equivalent, 40. 6 and 24. 4; valency, 3 and 5;specific gravity, 6. 8. It is a conductor of electricity. Relative resistance, compressed (silver = 1), 23. 60Specific resistance, 35. 50 microhms. Resistance of a wire, (a) 1 foot long, weighing 1 grain, 3. 418 ohms. (b) 1 foot long, 1/1000 inch thick, 213. 6 "(c) 1 meter long, weighing 1 gram, 2. 384 "(d) 1 meter long. 1 millimeter thick, 0. 4521 " Resistance of a 1-inch cube, 13. 98 microhms. Approximate percentage resistance per degree C. (1. 8º F. At 20º C. 88º F. ) 0. 389 per cent. Elcctro-chemical equivalent (hydrogen = . 0105) . 2560(See Thermo-Electric Series. ) Anvil. An intermittent contact, or "make and break" of the current is sometimesproduced by directly pressing a key down upon a metallic surface, thetwo being terminals of the circuit. The surface or stud on which suchpressure is produced is called the anvil. The ordinary telegraph key, which makes a contact by the pressure of the operator's fingers does itby making a contact between a contact piece upon the front end of thekey and the anvil. In the induction coil the anvil is also found. Thusin the cut representing the end of an induction coil and its circuitbreaker in which O and O' and P and P' represent the secondary circuitterminal connections A is the core of soft iron wires, h is the anvil;the hammer when resting upon it so as to be in contact closes thecircuit. When the current coming from the primary to the post i, passesthrough the hammer and anvil h, and emerges by m, it magnetizes thecore; this attracts the hammer, which is made of or is armed with a massof iron. This breaks the circuit. The hammer falls at once on the anvil, again making the circuit, and the action is repeated with greatrapidity. Hammer and anvil or key and anvil connections should be madeof platinum. Fig. 17. INDUCTION COIL CIRCUIT BREAKER. 38 STANDARD ELECTRICAL DICTIONARY. A. O. C. Abbreviation for Anodic Opening Contraction, q. V. Aperiodic. Adj. In an oscillating apparatus, or in the oscillating member of apparatus, the fact of having no reference to time of vibration; dead-beat. Synonym. Dead-beat. 39 STANDARD ELECTRICAL DICTIONARY. Fig. 18. ARAGO'S DISC. Arago's Disc. An apparatus consisting of a disc of copper mounted horizontally, or ona vertical spindle, and so arranged as to be susceptible of rapidrotation. Immediately over it, and best with a pane of glassintervening, a magnetic needle is mounted on a pivot directly over theaxis of the disc. If the disc is rotated the lines of force of themagnet are cut by it, and consequently currents are produced in thecopper. These currents act upon the needle and cause it to rotate, although quite disconnected. It is advisable for the needle to be strongand close to the disc, which should rotate rapidly. Arc v. To form a voltaic arc. Arc, Compound. A voltaic arc springing across between more than two electrodes. Arc, Metallic. The voltaic arc produced between terminals or electrodes of metal. Thecharacteristics of such arc as contrasted with the more usual arcbetween carbon electrodes are its greater length for the sameexpenditure of energy, its flaming character and characteristic colorsdue to the metals employed. It is sometimes, for the latter reason, usedin spectroscopic investigations. Arc Micrometer. A micrometer for measuring the distance between the electrodes of avoltaic arc. Arc, Simple. A voltaic arc produced, as usual, between only two electrodes. 40 STANDARD ELECTRICAL DICTIONARY. Arc, Voltaic. The voltaic arc is the arc between two carbon electrodes slightlyseparated, which is produced by a current of sufficient strength andinvolving sufficient potential difference. The pencils of carbon aremade terminals in a circuit. They are first placed in contact and afterthe current is established they are separated a little. The current nowseems to jump across the interval in what sometimes appears an arch oflight. At the same time the carbon ends become incandescent. As regardsthe distance of separation with a strong current and high electro-motiveforce, the arc may be several inches long. The voltaic arc is the source of the most intense heat and brightestlight producible by man. The light is due principally to theincandescence of the ends of the carbon pencils. These are differentlyaffected. The positive carbon wears away and becomes roughly cupped orhollowed; the negative also wears away, but in some cases seems to haveadditions made to it by carbon from the positive pole. All this is bestseen when the rods are slender compared to the length of the arc. It is undoubtedly the transferred carbon dust which has much to do withits formation. The conductivity of the intervening air is due partly, perhaps, to this, but undoubtedly in great measure to the intenseheating to which it is subject. But the coefficient of resistance of theintervening air is so much higher than that of any other part of thecircuit that an intense localization of resistance occurs withcorresponding localization of heating effect. This is the cause of theintense light. Thus if the carbons are but 1/32 of an inch apart as in acommercial lamp the resistance may be 1. 5 ohms. The poor thermalconductivity of the carbon favors the concentration of heat also. Theapparent resistance is too great to be accounted for by the ohmicresistance of the interposed air. A kind of thermoelectric effect isproduced. The positive carbon has a temperature of about 4, 000° C. (7, 232° F. ), the negative from 3, 000° C. (5, 432° F. ) to 3, 500° C. (6, 322° F. ). This difference of temperature produces acounter-electro-motive force which acts to virtually increase theresistance of the arc. The carbon ends of an arc can be projected withthe lantern. Globules are seen upon them due to melted silica from thearc of the carbon. Fig. 19. EXPERIMENTAL APPARATUS FOR PRODUCING THE VOLTAIC ARC. 41 STANDARD ELECTRICAL DICTIONARY. Areometer. An instrument for determining the specific gravity of a fluid. Itconsists of an elongated body ballasted so as to float vertically andprovided with a mark or a scale. It floats deeper in a light than in aheavy liquid. If it carries but one mark weights are added until thatmark is reached, when the weights required give the specific gravity. Orthe scale may give the reading directly based upon the depth to which itsinks. Areometers are often made of glass, ballasted with shot ormercury enclosed in their bottom bulb as shown. They are used inregulating battery solutions, and in watching the charging anddischarging of storage batteries. Fig. 20. AREOMETER Fig. 21. BEAD AREOMETER Areometer, Bead. A tube of glass containing beads of different specific gravities. It hasapertures at top and bottom. When immersed in a liquid, the same fillsit, and the specific gravity within certain limits, depending on thefactors of the beads, is shown by the beads which float and those whichsink. It is used for storage batteries and other purposes where acidsand solutions have to be tested. Argyrometry. The method of ascertaining the weight and inferentially the thickness ofan electroplater's deposit of silver. It is done by weighing the articlebefore and after plating. Arm. The four members of a Wheatstone bridge, q. V. , are termed its arms. Referring to the diagram of a bridge, P, Q, R, S, are the arms. Fig. 22. DIAGRAM OF WHEATSTONE'S BRIDGE. Armature. (a. ) A mass or piece of iron or steel, or a collection of pieces of irondesigned to be acted on by a magnet. While nickel or cobalt might beused, they rarely or never are except in experimental apparatus. Thearmature of a permanent horse shoe magnet is simply a little bar of softiron. When the magnet is not in use it is kept in contact with the poleswith the idea of retaining its magnetism. It is then said to be used asa keeper. A bar magnet does not generally have an armature. The armatureis also used to exhibit the attraction of the magnet. Sometimes an armature is made of steel and is permanently magnetized. Such an armature, termed a polarized armature, is repelled when its likepoles are opposed to like poles of the magnet and otherwise is attractedwith force due to the sums of the magnetism. If the magnet issufficiently powerful depolarization of the armature may ensue when likepoles are opposed to like poles. Polarized armatures are used in variousappliances, magneto generators, telegraphic instruments and others. (b) In a dynamo or Motor the mass of laminated iron or of wire whichcarries the coils of insulated wires which are caused to rotate in thefield of force of the field magnets in order to establish and maintainpotential difference with its accompanying current, or which rotatesunder the effects of a current in a motor. (See Dynamo ElectricGenerator. ) The work of the armature core is twofold. It acts as a portion of themagnetic circuit, conducting the lines of force, and by virtue of itshigh permeability or multiplying power concentrating a number of thelines of force through its own substance. To enable it to act withefficiency in this direction it should be made of iron of the highestpermeability, and should approach as closely as possible to the armaturecores consistent with leaving space for the wire winding. It next actsas a support for the wires which are to be swept through the field offorce. Thus it acts both to establish a strong field and then acts as acarrier for the wires which are to be cut by the wires in question. Inconnection with this subject the different definitions under Armature, Dynamo, Commutator, Induction and similar topics may be consulted. (c) See Armature of Influence Machine. (d) See Armature of Leyden Jar or Static Condenser. 42 STANDARD ELECTRICAL DICTIONARY. Armature, Bar. An armature in a dynamo or motor whose winding is made up of conductorsin the form of bars, round, rectangular and of other sections. This typeof armature conductor is objectionable as Foucault currents are producedin it. It is found best to laminate or subdivide low resistance armaturewindings. [Transcriber's Note: Foucault currents are also called eddy currents. ] Armature, Bipolar. An armature in which two poles are induced by the field. A bipolar fieldmagnet produces a bipolar armature. Armature Bore. The cylindrical space defined by the pole pieces of a dynamo or motorwithin which the armature rotates. Synonym--Armature Chamber. 43 STANDARD ELECTRICAL DICTIONARY. Armature, Closed Coil. An armature for a motor or dynamo, the ends of all of whose coils areunited, so as to be in one closed circuit all the way around. Fig. 23. CLOSED COIL GRAMME RING ARMATURE. Armature Coil, or Coils. The insulated wire wound around the core of the armature of an electriccurrent generator or motor. Armature Core. The central mass of iron on which the insulated wire, to be rotated inthe field of an electric current generator or motor, is wound. (SeeDynamo-electric Machine and Motor, Electric. ) Armature, Cylinder. An armature of the Gramme ring type, but longer in the axial direction, so that its core resembles a long hollow cylinder, the wire being woundinside and outside as in the Gramme ring. (See Gramme Ring. ) Armature, Disc. (a) An armature of a dynamo electric machine or motor in which the coilsare wound so as to be flat and are carried on the face of a disc formingthe core or part of the core of the armature. S. P. Thompson treats itas a modified drum armature extended radially, the outer peripherycorresponding to the back end of the drum. The poles of the field aregenerally placed to face the side or sides of the disc. (b) Another type of disc armature has its wire wound on bobbins arrangedaround the periphery of a disc. In disc armatures there is often no iron core, their thinness enablingthis to be dispensed with. 44 STANDARD ELECTRICAL DICTIONARY. Fig. 24. DISC ARMATURE OF FRITSCHE MACHINE. Fig. 25. PLAN OF WINDING PACINOTTI'S DISC ARMATURE. Armature, Discoidal Ring. In a dynamo an armature of the shape of a ring of considerable radialdepth of section as compared to its axial depth. It is generally made ofiron ribbon or thin band wound to the proper size. Synonym--Flat Ring Armature. 45 STANDARD ELECTRICAL DICTIONARY. Armature, Drum. An armature for a dynamo or motor, consisting of a cylinder of ironpreferably made up of discs insulated from each other by thin shellackedpaper, or simply by their oxidized surfaces, and wound with wireparallel to the axis where it lies on the cylindrical periphery andcrossing the heads approximately parallel to the diameter. It operatespractically on the same principle as a Gramme Ring Armature. (See GrammeRing. ) Synonym--Cylindrical Armature. Armature Factor. The number of conductors on an armature, counted or enumerated allaround its external periphery. Armature, Hinged. An armature pivoted to the end of one of the legs of an electro-magnetso as to be free to swing and bring its other end down upon the otherpole. Fig. 26. HINGED ARMATURES OF CLUB-FOOT ELECTRO MAGNETS. Armature, Hole. An armature whose core is perforated to secure cooling. Synonym--perforated Armature. Armature, Intensity. An armature wound for high electro-motive force. A term little used atthe present time. Armature Interference. A limit to the ampere turns permissible on a given armature is found inthe increase of cross magnetizing effect, q. V. , the increased leadnecessitated, and the growth of the demagnetizing power. All suchperturbing effects are sometimes expressed as armature interference. 46 STANDARD ELECTRICAL DICTIONARY. Armature, Load of. The circumflux, q. V. , of the armature, or the ampere turns of the same. The maximum load which can be carried by an armature without sparking isdirectly proportional to the radial depth of core and to the length ofthe gap, and inversely proportional to the breadth of the polar span. Armature, Multipolar. An armature in which a number of poles greater than two is determined bythe field. A multipolar field is employed for its production. Armature, Neutral. An armature of a magnet or telegraph relay which is not polarized ormagnetized. Synonym--Non-polarized Armature--Neutral Relay Armature. Armature of Influence Machine. Pieces of paper pasted on the stationary plate of an electric machine ofthe Holtz type. Armature of Leyden Jar or Static Condenser. The inner and outer tin-foil coatings of a Leyden jar or othercondenser. Armature, Open Coil. An armature of a dynamo or motor on which the coils are not joined inone closed circuit, but have their ends or some of them separated, andconnected each to its own commutator bar or each set to their own bar. Fig. 27. OPEN COIL RING ARMATURE. 47 STANDARD ELECTRICAL DICTIONARY. Armature, Pivoted. An armature for an electro-magnet mounted on a pivot, which is at rightangles to the yoke or parallel with the legs of the magnet, so as to befree to rotate. When the magnet is excited the armature is drawn intoline or approximately so with its base or yoke. The system is used insome telegraph apparatus. Armature Pockets. Spaces or recesses in armatures provided for the reception of the coils. Armature, Polarized. An armature made of steel or having a steel core to which permanentmagnetism has been imparted. Such are used in some forms of magnetocurrent generators, and in telegraphic instruments. (See Relay, Polarized. ) Armature, Pole. An armature having coils wound on separate poles projecting radially allaround the periphery of its central hub or disc, or projectinginternally from a ring-like frame, their ends facing the field magnet. Synonym--Radial Armature. Armature, Quantity. An armature of a dynamo or motor wound for current of large quantity. The term is now but little used. Armature-Reactions. When an armature is running in an active dynamo a series ofreactions is established, the more important of which are:I. A tendency to cross-magnetize the armature. II. A tendency to spark at the brushes. III. A tendency for the armature current to demagnetize on account ofthe lead which has to be given to the brushes. IV. Variations in the neutral points as more or less current is takenfrom the machine. V. Heating of armature, both core and conductors, and of pole pieces, which heating is due to Foucault currents. Armature, Revolving, Page's. An early form of motor. The field is produced by a permanent magnet. Above its poles is a soft iron armature wound with a coil of insulatedwire. A two-part commutator with contact springs conveys the current tothe coil. The whole is so arranged that the polarity of the armature, asinduced by the coil, through which a current is passed, is reversed asits ends sweep by the poles of the magnet. Then it is repelled from thepoles and swings through 180° to have its polarity reversed and to gothrough the next 180°, and so on. Thus it rotates at a very high rate ofspeed. In the cut showing the elevation A, B, is the armature; f, g, thesprings or brushes; h, the commutator with its sections o, i. In thesection of the commutator W, W, designate the springs or brushes, A, thevertical spindle carrying the armature and commutator, and S, S, thecommutator sections. 48 STANDARD ELECTRICAL DICTIONARY. Fig. 28. PAGE'S REVOLVING ARMATURE. Fig. 29. SECTION OF COMMUTATOR OF PAGE'S REVOLVING ARMATURE. W, W, Brushes; A, Spindle; S, S, Armature Segments. Armature, Ring. An armature whose core is in the shape of a ring, as the Gramme RingArmature. (See Figs. 23 & 27. ) 49 STANDARD ELECTRICAL DICTIONARY. Armature, Rolling. (a) An armature for a permanent horseshoe magnet consisting of astraight cylinder of soft iron on which a heavy wheel is mounted. Whenthe legs of the magnet are inclined downward and the bar is laid acrossthem it rolls down to the poles, across their ends, and back up theunder side. It is merely a magnetic toy or illustrative experiment. Synonym--Wheel Armature. (b) Another form consists of little bars of iron with brass discsattached to the ends. On placing two of these together and bringing thepoles of a magnet near them, as shown, they become magnetized with likepolarity by induction and repel each other, rolling away in oppositedirections. Fig. 30. ROLLING OR WHEEL ARMATURE. Fig. 31. ROLLING ARMATURES. Armature, Shuttle. The original Siemens' armature, now discarded. The core was long andnarrow, and its cross section was nearly of the section of an H. Thegrooves were wound full of wire, so that the whole formed almost aperfect cylinder, long and narrow comparatively. (See Winding Shuttle. ) Synonym--Siemens' Old Armature--Girder Armature--H Armature. Fig. 32. SHUTTLE OR H ARMATURE. Armature, Spherical. An armature of a dynamo which is wound on a spherical core, so as to bealmost a sphere. It is employed in the Thomson-Houston dynamo, beingenclosed in a cavity nearly fitting it, formed by the pole pieces. Armature, Stranded Conductor. A substitute for bar-armatures in which stranded copper wire conductorsare substituted for the solid bar conductors, to avoid Foucaultcurrents. (See Armature, Bar. ) 50 STANDARD ELECTRICAL DICTIONARY. Armature, Unipolar. An armature of a unipolar dynamo. (See Dynamo Unipolar. ) Armor of Cable. The metal covering, often of heavy wire, surrounding a telegraph orelectric cable subjected to severe usage, as in submarine cables. Synonym--Armature of Cable. Arm, Rocker. An arm extending from a rocker of a dynamo or motor, to which arm one ofthe brushes is attached. (See Rocker. ) Ordinarily there are two arms, one for each brush. Articulate Speech. Speech involving the sounds of words. It is a definition which hasacquired importance in the Bell telephone litigations, one contention, concerning the Bell telephone patent, holding that the patentee did notintend his telephone to transmit articulations, but only sound andmusic. Astatic. Adj. Having no magnetic directive tendency due to the earth's magnetism. Examples are given under Astatic Needle; Circuit, Astatic; andGalvanometer Astatic. Fig. 33. NOBILI'S PAIR. FIG. 34. VERTICAL PAIR ASTATIC COMBINATION. Astatic Needle. A combination of two magnetic needles so adjusted as tohave as slight directive tendency as possible. Such a pair of needleswhen poised or suspended will hardly tend to turn more to one point ofthe compass than another. The combination is generally made up of twoneedles arranged one above the other, with their poles in oppositedirections. This combination is usually called Nobili's pair. If ofequal strength and with parallel magnetic axes of equal length theywould be astatic. In practice this is very rarely the case. A resultantaxis is generally to be found which may even be at right angles to thelong axis of the magnets, causing them to point east and west. Such acompound needle requires very little force to turn it one way or theother. If one of the needles is placed within a coil of insulated wire afeeble current will act almost as strongly to deflect the system as ifthe other was absent, and the deflection will only be resisted by theslight directive tendency of the pair of needles. This is the basis ofconstruction of the astatic galvanometer. Sometimes coils wound inopposite directions and connected in series, or one following the other, surround both needles, thus producing a still greater effect ofdeflection. Other astatic needles are shown in the cuts below. [Figures 33 to 35. ] 51 STANDARD ELECTRICAL DICTIONARY. FIG. 35. SIMPLE ASTATIC NEEDLE. Asymptote. A line continuously approached by a curve, but which the curve, owing toits construction or nature of curvature, can never touch, be tangent to, or intersect. Atmosphere. (a) A term applied to the atmospheric pressure as a practical unit ofpressure equal to 15 lbs. To the square inch as generally taken. It isreally about 14. 7 lbs. Per square inch, or 1, 033 grams per squarecentimeter. (b) Air, q. V. Atmosphere Residual. The atmosphere left in a vessel after exhaustion. The term may beapplied to any gas. In an incandescent lamp after flashing the residualatmosphere consists of hydro-carbons. Atmospheric Electricity. The electricity of the atmosphere, rarely absent, but often changing inamount and sign. Benjamin Franklin, in a memoir published in 1749, indicated the method of drawing electricity from the clouds by pointedconductors. In June, 1752, he flew a kite and by its moistened cord drewan electric spark from the clouds, confirming his hypothesis thatlightning was identical with the disruptive discharge of electricity. Toobserve electricity in fine weather a gold-leaf or other electroscopemay be connected to the end of a long pointed insulated conductor. Theelectricity during thunderstorms can be shown by a similar arrangement, or burning alcohol or tinder gives an ascending current of warm air thatacts as a conductor. Quite elaborate apparatus for observing andrecording it have been devised. Atmospheric electricity is usuallypositive, but occasionally negative. When the sky is cloudless it isalways positive, increasing with the elevation and isolation of theplace. In houses, streets, and under trees no positive electricity canbe found. In the Isle of Arran, Scotland, a rise of 24 to 48 volts perfoot of increase in elevation was found by Sir William Thomson. Atsunrise the electrification of the air is feeble, it increases towardsnoon and decreases again to reach a second maximum a few hours aftersunset. It increases with the barometric pressure generally. In cloudyweather it is sometimes negative and the sign often changes severaltimes in the same day. In a thunderstorm the changes in sign andpotential are very rapid. The cause of atmospheric electricity is farfrom clear. Tait attributes it to a contact effect between air and watervapor, Solmeke to friction of water vesicles against ice particles inthe upper atmosphere, he first showing that the two may coexist. Thecause of the enormous increase of potential producing lightning isattributed to the decreased capacity due to the change of water fromcloud vesicles to drops, thus diminishing the electrostatic capacity ofthe water in question. (See Lightning. ) 52 STANDARD ELECTRICAL DICTIONARY. Atom. The ultimate particle or division of an elementary substance; thesmallest part that can exist in combination, and one which cannot existalone. An elementary substance is composed of molecules just as truly asa compound one, but the atoms in the molecule of an elementary substanceare all precisely alike. Hence atoms are the units of chemistry, theyhave to do with combinations, but the physical unit, the smallestparticle of matter that can have an independent existence, is themolecule. The two are often confounded, especially by writers of a fewyears ago, so that by "atom" the molecule is often meant. There isnothing to be said of their size or mass. All such calculations refer tothe molecule, q. V. , often spoken of and called the atom. [Transcriber's note: Yet to be discovered: electron--1897 (5 years), proton--1920 (28 years), neutron--1932 (30 years), quark--1961 (69 years). ] Atomic Attraction. The attraction of atoms for each other, in virtue of which they combineinto molecules; chemical affinity, q. V. , treats principally of this, although molecular attraction also plays a part in it. Atomic Heat. The product of the atomic weight of a substance by its specific heat. This product is approximately the same, 6. 4; this approximation is soclose that it is of use in determining the valency and atomic weights ofsubstances. The atomic weight of a substance therefore represents theapproximate number of gram-calories required to raise one gram-atom, q. V. , of such substance through 1° C. (1. 8° F. ) Atomicity. The quantivalence or valency of the atoms; the number of combinationbonds, or bonds of affinity, possessed by the atoms of any substance. Thus two atoms of hydrogen combine with one atom of oxygen, and three ofoxygen with one of sulphur, forming saturated compounds. Therefore, taking hydrogen as of single atomicity or a monad, oxygen is of doubleatomicity or a dyad, and sulphur is of six-fold atomicity, or a hexad. The elements are thus classified into seven orders of atomicities, thus: 1, Monads or Univalent elements, Hydrogen, etc. 2, Dyads or Bivalent " Oxygen, etc. 3, Triads or Trivalent " Nitrogen, etc. 4, Tetrads or Quadrivalent " Lead, etc. 5, Pentads or Quinquivalent " Phosphorous, etc. 6, Hexads or Sexivalent " Chromium, etc. 7, Heptads or Septivalent " Chromium, etc. The same element often possesses several atomicities. Barium isgenerally a dyad, sometimes a tetrad; nitrogen acts as a monad, dyad, triad, tetrad and pentad. The familiar electrolysis of water, giving twovolumes of hydrogen to one of oxygen, is one of the illustrations of thetheory indicating that two atoms of hydrogen are combined with one ofoxygen. 53 STANDARD ELECTRICAL DICTIONARY. Atomic Weight. The number expressing the relative weight of the atom of any substance, that of hydrogen being generally taken as unity. This is the universalsystem, although any other element might be taken as the basis of thesystem. The whole theory of atomic weights is based on theindivisibility of the atom and on the theory of atomicity, q. V. (SeeEquivalents. ) [Transcriber's note: The standard is now the isotope carbon-12 asexactly 12. ] Attraction. The tendency to approach and adhere or cohere, shown by all forms ofmatter. It includes gravitation, cohesion, adhesion, chemical affinityand other forms, and is opposed by repulsion, and is sometimes overcomeby it, although it may be assumed to be always present. See thedifferent kinds of attractions under their titles: Atomic Attraction, Electro-magnetic Attraction and Repulsion, Electro Static Attraction andRepulsion, Electro-dynamic Attraction and Repulsion; Magnetic Attractionand Repulsion; Molar Attraction. Audiometer. An apparatus for obtaining a balance of induction from two coils actingupon a third. The third is placed between the other two and is free tomove towards either. A scale is provided to show the extent of itsmovement. A varying or interrupted current being passed through the twoouter coils, the preponderating current will produce the most inductionif the central coil is equidistant. It can always be moved to such apoint that there will be no inductive effect, one counteracting theother. Thus its position measures the relative induction. A telephone isin circuit with the intermediate coil and is used to determine when itsposition is such that no current is induced in it. It is sometimes usedas a direct test of hearing. (See Hughes' Induction Balance. ) Synonym--Acoutemeter. Aura, Electrical. The blast of air produced at highly electrified points. Aurora. A luminous display seen in the northern heavens in the northernhemisphere, where it is the Aurora Borealis, and seen in the southernheavens in the southern hemisphere, where it is called Aurora Australis, or indifferently for either, the Aurora Polaris. It takes the form ofpale luminous bands, rays and curtains varying in color. Near the polesthey are very numerous. A French commission observed 150 auroras in 200days. Their height is variously estimated at from 90 to 460 miles; theyare most frequent at the equinoxes and least so at the solstices. Thereis a secular variation also, they attain a maximum of occurrence every11 years together with sun spots, with a minimum 5 or 6 years after themaximum. There is also a period of 60 years, coincident withdisturbances in the earth's magnetism. Various attempts have been madeto account for them. They have a constant direction of arc withreference to the magnetic meridian (q. V. ) and act upon the magneticneedle; in high latitudes they affect telegraph circuits violently. There is a strong probability that they represent electric currents ordischarges. De la Rive considers them due to electric discharges betweenthe earth and atmosphere, which electricities are separated by theaction of the sun in equatorial regions. According to Balfour Stewart, auroras and earth currents. (q. V. ) may be regarded as secondary currentsdue to small but rapid changes in the earth's magnetism. The subject isvery obscure. Stewart treats the earth as representing the magnetic coreof an induction coil, the lower air is the dielectric, and the upperrarefied and therefore conducting atmosphere is the secondary coil. Thismakes the aurora a phenomenon of induced currents. Then the sun may beregarded as the instigator of the primary changes in the earth's linesof force representing the primary of an induction coil. [Transcriber's note: Solar wind, streams of electrons and protons, interacting with the earth's magnetic field causes aurora. Neitherelectrons (1897) nor protons (1920) were known in 1892. The Sovietsatellite Luna first measured the solar wind in 1959. Even todayincreased understanding of solar and auroral phenomenon continues. ] 54 STANDARD ELECTRICAL DICTIONARY. Austral Pole. The north pole of the magnet is thus called sometimes in France; theaustral pole of a magnet is the one which points towards the north polarregions As unlike magnetic poles attract each other, it is but rationalto call the north-seeking pole of the magnet the south or Austral Pole. In the same nomenclature the south pole of a magnet, or thesouth-seeking pole, is called the Boreal Pole. A. W. G. Abbreviation for American Wire Gauge, q. V. Axis, Electric. The electric axis of a pyroelectric crystal, such as a tourmalinecrystal; the line connecting the points of greatest pyroelectricexcitability. Axis of Abscissa. In a system of rectilinear, or right angle co-ordinates, the horizontalaxis. (See Co-ordinates. ) Synonym--Axis of X. Axis of Ordinates. In a system of rectilinear right angle co-ordinates, the vertical axis. (See Co-ordinates. ) Synonym--Axis of Y. Azimuth. The angle between the plane of the meridian and the plane of an azimuthcircle, q. V. Azimuth Circle. A great circle, whose plane passes through the zenith or point of theheavens directly overhead; any great circle in whose plane the verticalat the point of observation is included. Each celestial body has or determines an azimuth circle. 55 STANDARD ELECTRICAL DICTIONARY. B. (a) Abbreviation for Baumé, a hydrometer scale. (See Baumé. ) Thus 10º B. Means "ten degrees Baumé. " (b) Symbol for the coefficient of induced magnetization, or the numberof lines per square centimeter induced in a magnetic circuit or in anyspecified part of it. B. A. Abbreviation for British Association. It is prefixed to standards fixedby the committee of the British Association for the Advancement ofScience. Thus the B. A. Ohm means the British Association ohm, a measureof resistance which is equal to the resistance of a column of mercury104. 9 centimeters long and one square millimeter area of cross-section. (See Ohm. ) Back Induction. A demagnetizing force produced in a dynamo armature when a lead is giventhe brushes. The windings by such setting of the brushes are virtuallydivided into two sets, one a direct magnetizing set, the other a crossmagnetizing set. The latter have a component due to the obliqueness ofthe neutral line, which component is demagnetizing in its action. Back Shock or Stroke of Lightning. A lightning stroke received after the main discharge of the lightning, and caused by a charge induced in neighboring surfaces by the maindischarge. The discharge affects the evenness of distribution ofsurrounding surfaces so that a species of secondary discharge isrequired to make even the distribution, or to supply charge where neededto bind an opposite one. The effects are much lese severe as a rule thanthose of the main charge, although the back stroke has caused death. Theback stroke is sometimes felt a considerable distance from the place ofthe original lightning stroke. Synonym--Return Stroke. Back Stroke. (a) In telegraphy the return stroke of the lever in a telegraph sounder, striking the end of the regulating screw with a sound distinct from thatwhich it produces on the forward stroke as it approaches the magnetpoles. It is an important factor in receiving by ear or sound reading. (b) See Back Shock or Stroke of Lightning. Balance. (a) Wheatstone's Bridge, q. V. , is sometimes termed the ElectricBalance. (b) A suspension or torsion balance is one which includes a filament orpair of filaments to whose lower end or ends are attached a horizontalindicator often called a needle, or a magnetic needle. (See TorsionBalance. ) (c) See Induction Balance, Hughes'. (d) For Thermic Balance, see Bolometer. (e) See Balance, Ampere. 56 STANDARD ELECTRICAL DICTIONARY. Balance, Ampere. A class of electrical measuring instruments due to Sir William Thomsonmay be grouped under this head. The instrument is a true balance or scales such as used for weighing. Itis supported by a torsional wire support in place of knife edges. Ateach end it carries a circle of wire through which the current to betested is passed. The torsional wire support enables the current to becarried to these wire rings. Above and below each of these rings are twosimilar rings, also connected so as to receive the current. They are soconnected that the current shall go through them in opposite senses. When a current passes, therefore, one of these rings repels and oneattracts the balanced ring. The extent of this action measures the intensity of the current. Asliding weight moving along a graduated scale on the balance is used tobring the balance beam into equilibrium when the current is passing. Thedegree of displacement of this weight gives the strength of the currentin amperes. These balances are made for different currents. Thus there is acenti-ampere balance, deka-ampere balance and others, as well as anampere balance. Balata. A gum used as an insulating material. It is the inspissated juice of asapotaceous tree, the bullet tree, Mimusops globosa, of tropicalAmerica, from the Antilles to Guiana. It is intermediate in characterbetween caoutchouc and gutta percha. It is superior to gutta percha insome respects, being very slightly acted on by light. Synonym--Chicle. B. & S.. W. G. Abbreviation for Brown & Sharpe Wire Gauge; the regular American WireGauge. (See Wire Gauge, American. ) Barad. An absolute or fundamental unit of pressure, equal to one dyne persquare centimeter. Barometer. An apparatus for measuring the pressure exerted by the atmosphere. Itconsists, in the mercurial form, of a glass tube, over 31 inches long, closed at one end, filled with mercury and inverted, with its open endimmersed in a cistern of mercury. The column falls to a heightproportional to the pressure of the atmosphere from 30 to 31 inches atthe sea level. The "standard barometer" is a height of the mercury or ofthe "barometric column" of 30 inches or 760 centimeters, measured fromthe surface of the mercury in the cistern. The column of mercury is termed the barometric column. Above it in thetube is the Torricellian vacuum. [Transcriber's note: More accurately, 29. 92 inches of mercury or 14. 696PSI. ] Bars of Commutators. The metal segments of a commutator of a dynamo or motor. They are madeof bars of copper, brass or bronze insulated from one another. (SeeCommutator. ) Synonyms--Segments, Commutator Segments, Commutator Bars. 57 STANDARD ELECTRICAL DICTIONARY. Bath. (a) In electro-plating the solution used for depositing metal ascontained in a vat or tank; as a silver, copper, or nickel bath used forplating articles with silver, copper, or nickel respectively. (b) In electro-therapeutics a bath with suitable arrangements, electrodes and connections for treating patients with electricity. It istermed an electric bath or electro-therapeutic bath. Bath, Bipolar Electric. In electro-therapeutics a bath in which the electrodes are both immersedin the water. The patient placed between them receives part of thedischarge. The electrodes are large copper plates, termed shovelelectrodes. Bath, Electric Shower. An electro-medical shower bath. The patient is placed on a metallicstove or support connected to one of the electric terminals. Waterslightly alkaline is showered upon him. The other electrode is inconnection with the water. The rain of drops and streamlets is theconductor of the current or discharge. Bath, Multipolar Electric. An electro-medical bath with a number of electrodes instead of two. Bath, Stripping. In electro-plating a solution used for dissolving and thus removing theplating from any object. The stripping bath is of the same general typeas the plating bath for the same metal as the one to be dissolved. Theobject to be "stripped" is made the anode of a plating circuit, and asthe current acts the old plating is attacked and dissolves, leaving thebody of the article bare. It is simply the operation of platingreversed. The same term is applied to baths acting by simple solution. Stripping baths are described under the different metals as Silver Bath, Stripping--Gold Bath, Stripping. Bath, Unipolar Electric. An electro-medical bath, in which only one electrode connects with thewater of the bath. The second electrode is supported above the bath. Thepatient touches this while in the water whenever electric action isdesired. FIG. 36. THREE WIRE MOULDING OR BATTEN. FIG. 37. TWO WIRE MOULDING OR BATTEN. 58 STANDARD ELECTRICAL DICTIONARY. Batten. A strip of wood grooved longitudinally for holding wires in wiringapartments for electric light or power. In use they are fastened to thewall, grooves inward, or else grooves outward, with the wires lying inthe grooves and covered with the covering strip. For two wire work eachbatten contains two grooves; for the three wire system it contains threegrooves. Synonym--Moulding. Battery. A combination of parts or elements for the production of electricalaction. The term is principally applied to voltaic batteries, but thereare also magnetic batteries, batteries of Leyden jars, and othercombinations, described in their places, which come under this category. [Transcriber's note: A group of similar items such as questions, machines, parts, guns, or electric cells. ] Battery, Acetic Acid. A battery whose active solution or excitant is acetic acid or vinegar. This acid has been used by Pulvermacher in his medical battery, as beinga substance found in every household in the form of vinegar. It is nowbut little used. Battery, Alum. A battery using as excitant a solution of alum. This battery has hadsome application for electric clocks, but only to a limited extent. Fig. 38. BALLOON OR FLASK BATTERY. Battery, Aluminum. A battery in which aluminum is the negative plate and aluminum sulphatethe excitant. It is mounted like the gravity battery. Its electro-motiveforce is 0. 2 volt. 59 STANDARD ELECTRICAL DICTIONARY. Battery, Bagration. A battery with zinc and carbon electrodes immersed in earth sprinkledwith sal ammoniac (ammonium chloride). The copper is preferably firstimmersed in sal ammoniac solution and dried, until a green layer isformed on its surface. The battery is highly praised for its constancy by De la Rive, but maybe regarded as obsolete. Battery, Balloon. A form of gravity battery into whose centre a globular flask, B, isinverted, which is filled before inversion with copper sulphate, ofwhich 2 lbs. Are used, and water, so as to remain full. This acts as areservoir of copper sulphate, which it constantly supplies. The glassjar is closed with a perforated wooden cover. Battery, Banked. (a) A battery arranged to feed a number of separate circuits. (b) A battery connected in parallel or in multiple arc. Battery, Bichromate. A battery with amalgamated zinc and carbon plates, with an excitingfluid composed of sulphuric acid, water, and potassium bichromate. Forformula of such solutions see Electropoion Fluid--Kookogey'sSolution--Poggendorff's Solution--Trouvé's Solution--Delaurier'sSolution, and others. (See Index. ) Battery, Bunsen. A two fluid porous cell battery. The negative plate is carbon, thepositive plate, amalgamated zinc. The depolarizer is nitric acid orelectropoion fluid, q. V. , in which the carbon is immersed. The lastnamed depolarizer or some equivalent chromic acid depolarizing mixtureis now universally used. The excitant is a dilute solution of sulphuricacid. Originally the carbon was made cylindrical in shape and surroundedthe porous cups, in which the zinc was placed. This disposition is nowgenerally reversed. The electro-motive force is 1. 9 volts. Thedepolarizing solution is placed in the compartment with the carbon. Theexcitant surrounds the zinc. Fig. 39. BUNSEN'S BATTERY. 60 STANDARD ELECTRICAL DICTIONARY. Battery, Cadmium. A battery in which cadmium is the negative plate, sulphate of cadmiumsolution the excitant and depolarizer, and zinc the positive plate. Electro-motive force, . 31 volt or about one third of a Daniell cell. Itis mounted like a gravity battery. Battery, Callan. A modification of Grove's battery. Platinized lead is used for thenegative plate, and as a depolarizer a mixture of 4 parts concentratedsulphuric acid, 2 parts of nitric acid, and 2 parts of a saturatedsolution of potassium nitrate. (See Battery, Grove's. ) Battery, Camacho's. A battery with carbon negative and amalgamated zinc positive electrodes. The carbon is contained in a porous cup, packed with loose carbon. Electropoion or other fluid of that type serves as excitant anddepolarizer, and is delivered as shown from cell to cell by syphons. Fig. 40. CAMACHO'S BATTERY. Battery, Carré's. A Daniell battery for whose porous cup a vessel or species of sack madeof parchment paper is substituted. The battery has been used forelectric light, and has been run for 200 successive hours, by replacingevery 24 hours part of the zinc sulphate solution by water. 61 STANDARD ELECTRICAL DICTIONARY. Battery, Cautery. A battery used for heating a platinum wire or other conductor used forcauterization in electro-therapeutics. The term is descriptive, notgeneric. Battery, Chloric Acid. A battery of the Bunsen type in which an acidulated solution ofpotassium chlorate is used as depolarizer. Battery, Chloride of Lime. A battery in which bleaching powder is the excitant. The zinc electrodeis immersed in a strong solution of salt, the carbon in a porous vesselis surrounded with fragments of carbon and is packed with chloride oflime (bleaching powder). There is no action on open circuit. It has tobe hermetically sealed on account of the odor. Its electro-motive forceis--initial, 1. 65 volts; regular, 1. 5 volts. Synonym--Niaudet's Battery. Battery, Chromic Acid. Properly a battery in which chromic acid is used as a depolarizer. Itincludes the bichromate battery. (See Battery, Bichromate. ) Battery, Closed Circuit. A battery adapted by its construction to maintain a current on a closedcircuit for a long time without sensible polarization. The term ismerely one of degree, for any battery becomes exhausted sooner or later. As examples the Grove, Bunsen or Daniell batteries may be cited. 62 STANDARD ELECTRICAL DICTIONARY. Fig. 41. COLUMN BATTERY. Battery, Column. The original Volta's pile. It consists of a series of compound circularplates, the upper or lower half, A, copper; the other, Z, of zinc. Between each pair of plates some flannel or cloth, u, u, is laid, whichis saturated with dilute acid. As shown in the cut, the parts are laidup in two piles, connected at the top with a bar, c, c, and with vesselsof acidulated water, b, b, as electrodes. The great point in setting itup is to be sure that no acid runs from one disc of flannel to the nextover the outside of the plates, as this would create a short circuit. The plates are best compound, being made up of a zinc and a copper platesoldered together. They may, however, be separate, and merely laid oneon the other. In such case great care must be taken to admit no acidbetween them. Volta's pile is no longer used, except occasionally. Trouvé's blottingpaper battery (see Battery, Trouvé's) is a relic of it, and the same isto be said for Zamboni's dry pile. It rapidly polarizes, the flannel retains but little acid, so that it issoon spent, and it is very troublesome to set up. Great care must betaken to have the cloth discs thoroughly saturated, and wrung out toavoid short circuiting by squeezing out of the acid. Battery, D'Arsonval's. A battery of the Bunsen type, differing therefrom in the solutions. Asexcitant in which the zinc electrode is immersed, the following solutionis used: Water, 20 volumes;Sulphuric Acid (purified by shaking with a little olive or similar oil), 1 volume;hydrochloric acid, 1 volume. As polarizer in which the carbon is immersed the following is used: Nitric acid, 1 volume;hydrochloric acid, 1 volume;water acidulated with 1/20th sulphuric acid, 2 volumes. Battery, de la Rue. A battery with zinc positive and silver negative electrode; thedepolarizer is silver chloride; the excitant common salt or ammoniumchloride. The cut shows one of its forms of construction. The right hand portion of the cut, Fig. 42, shows the zinc perforated atC for the connection from the next silver plate. The next to it is thenegative electrode of silver around which a mass of silver chloride iscast in cylindrical form. A is a parchment paper cylinder with two holesnear its top, through which the silver wire of the negative electrode isthreaded, as shown in B. A solution of 23 parts ammonium chloride in1, 000 parts of water is the approved excitant. Its electro-motive forceis 1. 03 volts. The jars are closed with paraffin. Fig. 42. DE LA RUE'S BATTERY. 63 STANDARD ELECTRICAL DICTIONARY. Battery, Dry. (a) A form of open circuit battery in which the solutions by a mass ofzinc oxychloride, gypsum, or by a gelatinous mass such as gelatinoussilica, or glue jelly, are made practically solid. Numbers of such havebeen patented, and have met with considerable success. (b) Zamboni's dry pile, q. V. , is sometimes termed a dry battery. Battery, Element of. A term applied sometimes to a single plate, sometimes to the pair ofplates, positive and negative, of the single couple. Battery, Faradic. A term applied, not very correctly however, to apparatus for producingmedical faradic currents. It may be an induction coil with battery, or amagneto-generator worked by hand. Battery, Ferric Chloride. A battery of the Bunsen type, in which a solution of perchloride of iron(ferric chloride) is used for the depolarizing agent. A little bromineis added with advantage. The depolarizing agent recuperates on standing, by oxidation from the oxygen of the air. Battery, Fuller's. A battery of the Bunsen type. The zinc plate is short and conical, andrests in the porous jar into which some mercury is poured. An insulatedcopper wire connects with the zinc. A plate of carbon is in the outerjar. The solutions are used as in the Bunsen battery. Synonym--Mercury Bichromate Battery. Battery, Gas. (a) A battery whose action depends on the oxidation of hydrogen as itsgenerating factor. It was invented by Grove. Plates of platinum areimmersed in cups of dilute acid, arranged as if they were plates of zincand carbon, in an ordinary battery. Each plate is surrounded by a glasstube sealed at the top. The plates are filled with acid to the tops. Through the top the connection is made. A current from another batteryis then passed through it, decomposing the water and surrounding theupper part of one set of plates with an atmosphere of oxygen and of theother with hydrogen. Considerable quantities of these gasses are alsooccluded by the plates. On now connecting the terminals of the battery, it gives a current in the reverse direction of that of the chargingcurrent. This battery, which is experimental only, is interesting as being thefirst of the storage batteries. (b) Upward's Chlorine Battery and any battery of that type (see Battery, Upward's, ) is sometimes termed a gas battery. 64 STANDARD ELECTRICAL DICTIONARY. Battery Gauge. A pocket or portable galvanometer for use in testing batteries andconnections. Battery, Gravity. A battery of the Daniell type, in which the porous cup is suppressed andthe separation of the fluids is secured by their difference in specificgravity. A great many forms have been devised, varying only in details. The copper plate, which is sometimes disc shaped, but in any case ofinconsiderable height, rests at the bottom of the jar. Near the top thezinc plate, also flat or of slight depth, is supported. As excitingliquid a strong solution of copper sulphate lies at the bottom of thejar. This is overlaid by a solution of zinc sulphate, or sodiumsulphate, which must be of considerably less specific gravity than thatof the copper sulphate solution. In charging the jar one-tenth of asaturated solution of zinc sulphate mixed with water is sometimes usedas the upper fluid. This may be first added so as to half fill the jar. The strong solution of copper sulphate may then be added with a syphonor syringe underneath the other so as to raise it up. From time to timecopper sulphate in crystals are dropped into the jar. They sink to thebottom and maintain the copper sulphate solution in a state ofsaturation. Fig. 43. GRAVITY BATTERY OF THE TROUVÉ-CALLAUD TYPE. If the battery is left on open circuit the liquids diffuse, and metalliccopper precipitates upon the zincs. This impairs its efficiency andcreates local action. As long as the battery is kept at work on closedcircuit work but little deposition, comparatively speaking, occurs. From time to time, in any case, the zinc plates are removed and scraped, so as to remove the copper which inevitably forms on their surface. Caremust be taken that the zinc sulphate solution, which is constantlyincreasing in strength, does not get so strong as to become of as highspecific gravity as the copper sulphate solution. From time to time someof the upper solution is therefore removed with a syphon or syringe andreplaced with water. An areometer is useful in running this battery. 65 STANDARD ELECTRICAL DICTIONARY. Battery, Grenet. A plunge battery with zinc positive and carbon negative electrodes. Electropoion or other chromic acid or bichromate solution is used asdepolarizer and excitant. The zinc plate alone is plunged into andwithdrawn from the solution. Fig. 44. GRENET'S BATTERY. Fig. 45. GROVE'S BATTERY. Battery, Grove's. A two fluid galvanic battery. A porous cup has within it a riband ofplatinum, which is the negative plate; amalgamated zinc in the outer jaris the positive plate. Dilute sulphuric acid (10 per cent. Solution) isplaced in the outer jar, and strong nitric acid (40° B. ) as adepolarizer in the porous cups. Its E. M. F. Is 1. 96 volts. It is objectionable, as it gives off corrosive nitrous fumes. These areproduced by the oxidation of the nascent hydrogen by the nitric acid, bythe following reaction: 3 H + H N O3 = 2 H2 O + N O. There are other reactions, one of whichresults in the formation of ammonia by the reduction of the nitric acidradical by the hydrogen. Ammonium can be detected in the spent liquids. 66 STANDARD ELECTRICAL DICTIONARY. Battery, Hydrochloric Acid. A battery in which hydrochloric acid is used as the excitant. Manyattempts have been made to use this acid in batteries, but the volatilenature of the acid causes the production of so much odor with corrosivefumes that it has never come into use. Battery, Lead Chloride. A battery of the lead sulphate type in which lead chloride is thedepolarizer. It has had no extended use. Battery, Lead Sulphate. A battery similar to Marié Davy's battery or the gravity battery, butusing lead sulphate as depolarizer and excitant. Lead, copper or tin isthe material of the negative plate. Becquerel used the lead sulphate asa solid cylindrical mass surrounding a lead rod 1/5 to 1/4 inch indiameter. One part of common salt may be mixed with 5 parts of the leadsulphate. The electro-motive force is about 0. 5 volt. The resistance isvery high. Battery, Leclanché. An open circuit battery with porous cup. In the outer jar is a zinc rod;a carbon plate is placed in the porous cup. The latter is packed with amixture of clean powdered manganese binoxide as depolarizer, andgraphite in equal volumes. A strong solution of ammonium chloride (salammoniac) is placed in the outer jar. It is only used on open circuitwork. Its electromotive force is 1. 48 volts, when not polarized. The reaction is supposed to be about the following: 2 N H4 Cl + 2 Mn O2 + Zn = Zn Cl2 + 2 N H3 + H2 0 + M2 O3 The battery rapidly weakens on open circuit, but quickly recuperates. There is another form of this battery, termed the agglomerate battery. (See Battery, Leclanché Agglomerate. ) Fig. 46. LECLANCHÉ BATTERY. Battery, Leclanché Agglomerate. A form of the Leclanché in which the porous jar is suppressed. Cakesmade of a mixture of carbon, 52 parts; manganese binoxide, 40 parts; gumlac, 5 parts; potassium bisulphate, 3 parts, compressed at 300atmospheres, at a temperature of 100° C. (212° F. ), are fastened byIndia rubber bands or otherwise against the carbon plate. Theseconstitute the depolarizer. Various shapes are given the carbon anddepolarizing agglomerates. Battery, Local. A battery supplying a local circuit (see Circuit. Local). The current isgoverned by the relay situated on the main line and operated by itscurrent. Battery, Main. The battery used in operating the main line. It is usually applied totelegraphy. Its function is then to supply current for working relays, which in turn actuate the local circuits. Main and local circuits and batteries are also used in the automaticblock system of railroad signalling. 67 STANDARD ELECTRICAL DICTIONARY. Battery, Marié Davy's. A two fluid porous cup battery with carbon negative plate, zinc positiveplate, and mercury sulphate, a nearly insoluble salt, as depolarizer andexcitant. Mercurous or mercuric sulphates have been used in it. Itselectromotive force is 1. 5 volts. The local action and waste, owing tothe slight solubility of the mercury compounds, is very slight. If usedon close circuit it becomes polarized. It is also subject under extremecircumstances to reversal of polarity, zinc becoming deposited upon thecarbon, and there forming a positive electrode. In using the cells in series the level of liquid in all must be thesame, otherwise the cell in which it is lowest will become polarized andexhausted. Modifications of this battery on the lines of the gravity battery havebeen constructed. Synonym--Sulphate of Mercury Battery. Battery, Maynooth's. A battery of the Bunsen type, with cast iron negative plate. The irontakes the passive form and is not attacked. Battery, Medical. A term applied very indiscriminately to medical current generators, andto medical induction coils, or to any source of electricity, static orcurrent, for medical application. 68 STANDARD ELECTRICAL DICTIONARY. Battery, Meidinger's. A variety of Daniell cell of the gravity type. The plates arecylindrical. The zinc plate lies against the upper walls of the vessel. The copper plate of smaller diameter rests on the bottom. A large tube, with an aperture in its bottom, is supported in the centre and ischarged with copper sulphate crystals. The cup is filled with a dilutesolution of Epsom salts (magnesium sulphate) or with dilute sulphuricacid. Battery Mud. A deposit of mud-like character which forms in gravity batteries andwhich consists of metallic copper precipitated by the zinc. It indicateswasteful action. Battery, Multiple-connected. A battery connected in parallel, all the positive plates being connectedto one electrode, and all the negative to another. Battery, Nitric Acid. A battery in which nitric acid is used as the excitant. Owing to itscost and volatility this acid has been but little used in batteries, other than as a depolarizer. In Grove's battery (see Battery, Grove's)it has been thus used. Battery of Dynamos. A number of dynamos may be arranged to supply the same circuit. They arethen sometimes termed as above, a Dynamo Battery. They may be arrangedin series or in parallel or otherwise combined. Battery of Leyden Jars. To produce the quantity effect of a single large Leyden jar with anumber of small ones they are often connected in parallel and termed abattery. In such case the inner coatings are all connected by regularbar conductors, and the outside coatings are also all in connection. They are conveniently placed in a box or deep tray whose inner surfaceis lined with tinfoil, with an outside connection for grounding, etc. The cascade, q. V. , arrangement is not so generally termed a battery. Battery, Open Circuit. A battery adapted for use in open circuit work. Its main requirement isthat it shall not run down, or exhaust itself when left on open circuit. The Leclanché battery is very extensively used for this work. Its actionis typical of that of most open circuit batteries. It is without anyaction on open circuit. It is very quickly exhausted on closed circuit, but recuperates or depolarizes quite soon when on open circuit. It isalways in condition for a momentary connection, but useless for steadywork. Battery, Oxide of Copper. A battery with zinc positive and iron negative electrodes. The excitantis a 30 or 40 per cent. Solution of sodium or potassium hydrate (causticsoda or caustic potash). The depolarizer is copper oxide. In action thecopper is gradually reduced to the metallic state. The iron element isoften the containing vessel. The battery is practically inactive on opencircuit. Its electro-motive force varies from . 75 to . 90 volt. To prevent theformation of sodium or potassium carbonate the cell should be closed, orelse the liquid should be covered with mineral oil. Synonyms--Lalande & Chaperon Battery--Lalande-Edison Battery. 69 STANDARD ELECTRICAL DICTIONARY. Battery, Peroxide of Lead. A battery in which peroxide of lead (lead binoxide) is the depolarizer. It is a sort of predecessor of the present secondary battery. Battery, Platinized Carbon. A modification of Smee's battery, in which platinized carbon is used forthe negative plates. Before polarization the E. M. F. Is equal to thatof Smee's battery. Polarization reduces its electro-motive forceone-half. Battery, Plunge. A battery whose plates are mounted so as to be immersed in the batterycups or cells, when the battery is to be used, and withdrawn andsupported out of the cups when not in use. The object is to preventwasting of the plates by standing in the solution. It is a constructiongenerally used with sulphuric acid--chromic acid solution andamalgamated zinc and carbon plates. Battery, Pneumatic. A battery arranged to have air blown through the solution to assistdiffusion and depolarization. It is a construction applied to chromicacid or bichromate batteries. Battery, Primary. A battery in which the current is supplied by the solution of one of theplates by the solution. The term distinguishes it from a secondary orstorage battery. Battery, Pulvermacher's Electro-Medical. In this battery, the electrodes were zinc and copper wires wound uponsmall pieces of wood. Dilute vinegar was used as the excitant, becauseit could be found in every household. Formerly the battery had greatsuccess. It is now little used. Battery, Sal Ammoniac. Batteries in which a solution of ammonium chloride is the excitant; theyare very extensively used on open circuit work. (See Battery, Leclanché. ) The crystals formed in these batteries have been analyzed and found toconsist of ammonium zinc chloride, 3 Zn Cl2, 8 N H3, 4 H20. Battery, Salt, or Sea Salt. Batteries in which a solution of sodium chloride or common salt is theexcitant, have been largely used, especially for telegraphic purposes. The Swiss telegraphs use a carbon-zinc combination with salt and wateras the excitant. The batteries are sometimes mounted as plungebatteries. They are exhausted by short circuiting after some hours, butrecuperate on standing. The zinc is not amalgamated. 70 STANDARD ELECTRICAL DICTIONARY. Battery, Sand. A battery whose cells are charged with sand saturated with dilute acid. It prevents spilling of acid. It is now practically obsolete. Fig. 47. SECONDARY BATTERY. Battery, Secondary. A voltaic battery whose positive and negative electrodes are formed ordeposited by a current from a separate source of electricity byelectrolysis. On disconnection the battery is ready to yield a current, in the reverse direction of that of the charging current. The usual typehas lead plates on one of which lead binoxide and on the other of whichspongy lead is formed. The lead binoxide seems to be the negativeelement, and it also acts as the depolarizer. The spongy lead is thepositive electrode. The solution is dilute sulphuric acid of specificgravity 1. 17. The action consists first in the oxidation of the spongylead. The hydrogen set free by the reaction, and which by electrolytictransfer goes to the other plate, reduces the lead binoxide toprotoxide. The sulphuric acid then attacks the oxides and converts theoxides into sulphates. The charging process consists in sending a current in the reversedirection through the battery. If there are several cells they arearranged in series, so that each one receives the same intensity ofcurrent. An electrolytic decomposition takes place, the lead sulphate onone plate is reduced to metallic lead, and that on the other plate isoxidized to lead binoxide. It is then ready for use. 71 STANDARD ELECTRICAL DICTIONARY. The plates in a lead plate battery are of very large area per cell, andare placed close together. Sometimes, as in Planté's battery, large flatplates are laid together with a separating insulator between them, andare then rolled into a spiral. Sometimes, the most usual arrangement, the plates are in sets, the positive and negative ones alternating, andeach cell containing a number of plates. To secure a good quantity of active material, the plates are sometimesperforated, and the perforations are filled with oxide of lead. Thisgives a good depth of material for the charging current to act on, andavoids the necessity for a tedious "forming, " q. V. The electro-motive force of such a battery per cell is 2 volts. Itsresistance may only be one or two-hundredths of an ohm. An intensecurrent of many amperes can be supplied by it, but to avoid injuring thecell a current far less than the maximum is taken from it. To charge it, a slightly greater electro-motive force, the excess beingtermed spurious voltage, is required. Fig. 48. SIEMENS' AND HALSKE'S PAPER PULP BATTERY. 72 STANDARD ELECTRICAL DICTIONARY. Battery, Secondary, Plante's. Plante's secondary battery is one of the earlier forms of storagebattery, but has had much success. Two lead plates, large in area andclose together but not touching, are "formed, " by exposure to anelectrolyzing current of electricity in one direction, while they areimmersed in dilute sulphuric acid. This converts the surface of oneplate into binoxide. The cell is then allowed to discharge itself almostcompletely, when the charging current is again turned on. This processis repeated over and over again, until the surfaces of the plates areconsiderably attacked, one plate, however, being maintained in a stateof oxidation. After a few days of this operation a period of rest isallowed between the reversals, which sets up a local action on theoxidized plate, between the metallic lead of the plate, and its coatingof binoxide. This causes the lead to be attacked, under the influence ofthe local couple, and sulphate of lead is formed, which, ultimately, bythe charging current is converted into peroxide. These operationsproduce an exceedingly good battery. The process described is termedforming. The plates separated by strips of insulating material are generallywound into a double spiral. Battery, Siemens' and Halske's. A Daniell battery of peculiar shape. The copper, C, is at the bottom ofthe glass jar, A. The inner jar, K, has the form of a bell, and supportsa mass of paper pulp, which is dampened with sulphuric acid. The zinc, Z, rests on top of the mass of pulp. The battery is very durable, but ofhigh resistance. Battery, Sir William Thomson's. A form of Daniell battery, of the gravity type. The receptacles areshallow wooden trays lined with lead. A thin plate of copper rests onthe bottom. The zinc plate is of gridiron shape, and rests on woodenblocks which support it in a horizontal position above the copper. Onetray is placed on top of the other, the upper tray resting on thecorners of the zinc plate which rise above the level of the top of theflat vessel. Thus connection is assured without wires or binding posts. It is charged like a gravity battery. The density of the zinc sulphatesolution should be between 1. 10 and 1. 30. The circuit must be keptclosed to prevent deposition of metallic copper on the zinc. The entiredisposition of the battery is designed to reduce resistance. Battery, Skrivanow. A pocket battery of the De la Rue type, with a solution of 75 partscaustic potash in 100 parts of water as the excitant. The silverchloride is contained in a parchment paper receptacle. Itselectro-motive force is 1. 45 to 1. 5 volts. Battery, Smee's. A single fluid combination, with zinc positive plate, and a plate ofsilver, coated with platinum black, for the negative plate. The finelydivided platinum affords a surface from which the hydrogen bubblesinstantly detach themselves, thus preventing polarization. The liquid isa mixture of one part sulphuric acid to seven parts of water. For thenegative plate silver-plated copper, coated with platinum black, isused. Electromotive force, . 47 volt. Fig. 49. SMEE'S BATTERY. 73 STANDARD ELECTRICAL DICTIONARY. Fig. 50. SPIRAL BATTERY, OR HARE'S DEFLAGRATOR. Battery, Spiral. A battery whose plates of thin zinc and copper are wound into a spiralso as to be very close, but not touching. Dilute sulphuric acid is theexcitant. It is now practically obsolete. Synonyms--Calorimeter--Hare's Deflagrator. Battery, Split. A battery of a number of voltaic cells, connected in series, with theircentral portion grounded or connected to earth. This gives the ends ofopposite potentials from the earth, and of difference therefrom equal tothe product of one-half of the number of cells employed, multiplied bytheir individual voltage. Battery Solutions, Chromic Acid. A number of formulae have been proposed for these solutions. (SeeElectropoion Fluid--Kookogey's Solution--Poggendorff's Solution--Trouvé's Solution--Delaurier's Solution--Chutaux's Solution--Dronier'sSalt--Tissandier's Solution. ) Battery, Trough. A battery whose elements are contained in a trough, which is divided bycross-partitions so as to represent cups. A favorite wood for the troughis teak, which is divided by glass or slate partitions. Marine glue orother form of cement is used to make the joints tight. For porous cupdivisions plates of porous porcelain or pottery are placed across, alternating with the impervious slate partitions. Battery, Trouvé's Blotting Paper. A battery of the Daniell type in which the solutions are retained byblotting paper. A considerable thickness of blotting paper lies betweenthe two plates. The upper half of the thickness of the blotting paper issaturated with a solution of zinc sulphate, on which the zinc platerests. The lower half of the paper is saturated with copper sulphate solution, and this rests upon the copper plate. Fig. 51. TROUVÉ'S BLOTTING PAPER BATTERY. 74 STANDARD ELECTRICAL DICTIONARY. Battery, Tyer's. A modification, as regards the positive element, of Smee's battery, q. V. The bottom of the battery jar contains a quantity of mercury in whichpieces of zinc are thrown, and this constitutes the positive element. A ball of zinc at the end of an insulated copper wire affords theconnection with the zinc and mercury. Its great advantage is that thesmallest scraps of zinc can be used in it, by being dropped into themercury. The negative plate is platinized silver; the exciting liquid, dilute sulphuric acid. Fig. 52. TYER'S BATTERY. 75 STANDARD ELECTRICAL DICTIONARY. Fig. 53. SECTION OF UPWARD'S BATTERY. Fig. 54. ELEVATION OF UPWARD'S BATTERY. Battery, Upward's. A primary voltaic cell, the invention of A. Renée Upward. Referring tothe cuts, the positive plate. Z, is of cast zinc; it is immersed inwater, in a porous cup, B. Outside of the porous cup and contained inthe battery jar are two carbon plates, C, C, connected together. Therest of the space between the porous cup and battery jar is packed withcrushed carbon, and the top is cemented. Chlorine gas is led by a pipe, D, into the outer cell. It diffuses through the fine carbon, dissolvesin the water, and so finds its way to the zinc, which it attacks, directly combining therewith, and forming zinc chloride (Zn + 2 Cl = ZnCl 2). Such of the chlorine as is not absorbed finds its way by an outlettube, E, to the next cell. Arrangements are provided for generatingchlorine gas as required. The high specific gravity of the gas isutilized in regulating its distribution through the cells. Theelectro-motive force of the cell is 2. 1 volts. A cell 11. 5 by 5. 5 inchesand 12. 5 inches deep has a resistance of 0. 2 ohm. An overflow pipe, F, with faucet, T, is supplied to withdraw thesolution of zinc chloride as it accumulates. 76 STANDARD ELECTRICAL DICTIONARY. Battery, Varley's. A Daniell battery of the Siemens' and Halske's type (see Battery, Siemens' and Halske's), in which zinc oxide is substituted for the paperpulp of the other battery. It has been very little used. Battery, Volta's. The original acid battery. It has a negative electrode of copper, apositive electrode of zinc; the excitant is sulphuric acid diluted withsixteen times its volume of water. It rapidly polarizes, and is verylittle used. Battery, Voltaic or Galvanic. An apparatus for converting chemical energy directly into electricenergy. This is as broad a definition as can well be given. The generalconception of a battery includes the action of electrolysis, a solutionin the battery acting upon one of two conducting electrodes immersed insuch fluid, which dissolves one of them only, or one more than theother. The best way to obtain a fundamental idea of a battery is tostart with the simplest. Dilute sulphuric acid dissolves neither purezinc nor copper. But it has a far stronger affinity for the first namedmetal. If now we immerse in dilute acid two plates, one of pure zinc, and one of copper, no action will be discernible. But if the plates arebrought in contact with each other a stream of bubbles of hydrogen gaswill escape from the surface of the copper and the zinc will dissolve. By applying proper tests and deductions it will be found that the copperand zinc are being constantly charged with opposite electricities, andthat these are constantly recombining. This recombination produces whatis known as an electric current. To constitute a battery the zinc and copper plates must be connectedoutside of the solution. This connection need not be immediate. Anyconductor which touches both plates will bring about the action, and thecurrent will pass through it. The easiest way to picture the action of a battery is to accept thedoctrine of contact action. In the battery the molecules of water arepulled apart. The hydrogen molecules go to the copper, the oxygenmolecules go to the zinc, each one, leaving its contact with the other, comes off charged with opposite electricity. This charges the plates, and the continuous supply of charge and its continuous dischargeestablishes the current. The accumulation of hydrogen acts to stop the action by polarization. Its own affinity for oxygen acts against or in opposition to theaffinity of the zinc for the same element, and so cuts down the action. A depolarizer of some kind is used in acid batteries for this reason. Assuch depolarizer has only to act upon one plate, in most batteries it isusual to surround such plate only, as far as it is possible, with thedepolarizer. The solution which dissolves the zinc is termed theexcitant or exciting solution. To this concrete notion of a voltaic battery the different modificationsdescribed here may be referred. Zinc, it will be seen, forms the almostuniversally used dissolved plate; carbon or copper forms the most usualundissolved plate; sulphuric acid in one form or another is the mostusual excitant. The solution in a voltaic battery is electrolyzed (see Electrolysis). Hence the solutions must be electrolytes. The sulphuric acid and otheringredients play a secondary role as imparting to the battery fluidsthis characteristic. It is not necessary to have electrodes of different substances, the samemetal maybe used for both if they are immersed in different solutionswhich act differentially upon them, or which act with more energy on onethan on the other. Such are only of theoretical interest. 77 STANDARD ELECTRICAL DICTIONARY. Battery, Water. A voltaic battery, whose exciting fluid is water. They are used forcharging quadrant electrometer needles and similar purposes. Theypolarize very quickly and are of high resistance. Hence very smallplates in large number can be used without impairing their advantage. Rowland's water battery dispenses with cups and uses capillarityinstead. The zinc and platinum or copper plates of a couple are placedvery close together, while the couples are more distant. On dipping intowater each couple picks up and retains by capillarity a little waterbetween its plates, which forms the exciting fluid. Many hundred couplescan be mounted on a board, and the whole is charged by dipping intowater and at once removing therefrom. It then develops its fullpotential difference. Fig. 55. SECTION OF WOLLASTON BATTERY. Fig. 56. PLATES OF WOLLASTON'S BATTERY. 78 STANDARD ELECTRICAL DICTIONARY. Battery, Wollaston. The original plunge battery is attributed to Wollaston. He also inventedthe battery known by his name, having the disposition shown in the cut, of zinc Z, surrounded by a thin sheet of copper C; o, o', o", are theterminals and B, B, the battery jars. Dilute sulphuric acid is used forexciting fluid. B. A. U. Abbreviation for British Association unit, referring generally to the B. A. Unit of resistance. B. A. Unit of Resistance. The original ohm used under that name previous to 1884. The Pariscommittee of that year recommended as a practical unit what is known asthe legal ohm. (See Ohm, Legal. ) 1 Legal Ohm = 1. 0112 B. A. Units of Resistance. 1 B. A. Unit of Resistance = . 9889 Legal Ohms. 1 B. A. Unit of Resistance = . 98651E9 C. G. S. Units. B. E. Adj. British Engineering, a qualification of a set of units, the B. E. Units, having for base the foot and pound. The term is but little used. Beaumé Hydrometer. A hydrometer graduated on the following principle: The zero point corresponds to the specific gravity of water for liquidsheavier than water. A solution of 15 parts of salt in 85 parts of watercorresponds in specific gravity to 15° B. , and between that and zerofifteen equal degrees are laid out. The degrees are carried down belowthis point. The zero points for liquids lighter than water correspond to thespecific gravity of a solution of 10 parts of salt in 90 parts of water. The specific gravity of water is taken as 10° B. This gives ten degreeswhich are continued up the scale. Becquerel's Laws of Thermoelectricity. These are stated under the heads, Law of Intermediate Metals and Law ofSuccessive Temperatures, q. V. Bed Piece. In a dynamo or motor the frame carrying it, including often thestandards in which the armature shaft is journaled, and often the yokeor even entire field magnet core. Bell, Automatic Electric. A bell which rings as long as the circuit is closed, having a circuitbreaker operated by its own motion. (See Bell, Electric. ) Synonyms--Trembling Bell--Vibrating Bell. Bell, Call. A bell operated by electricity, designed to call attention, as to atelephone or telegraphic receiver. (See Bell, Electric. ) 79 STANDARD ELECTRICAL DICTIONARY. Bell Call. A calling device for attracting the attention of any one, consisting ofsome type of electric bell. Bell, Circular. A gong-shaped bell, whose clapper and general mechanism is within itscavity or behind it. Bell, Differentially Wound. An electric bell, whose magnet is wound differentially so as to preventsparking. Fig 57. AUTOMATIC ELECTRIC BELL. Bell, Electric. A bell rung by electricity. Generally it is worked by a current excitingan electro-magnet, attracting or releasing an armature which is attachedto the vibrating or pivoted tongue of the bell. It may be worked by adistant switch or press-button, q. V. , ringing once for each movement ofthe distant switch, etc. , or it may be of the vibrating bell type asshown in the cut. When the current is turned on in this case it attractsthe armature. As this moves towards the poles of the magnet it breaksthe circuit by drawing the contact spring, q. V. , away from the contactpoint, q. V. This opens the circuit, to whose continuity the contact ofthese two parts is essential. The hammer, however, by its momentumstrikes the bell and at once springs back. This again makes the contactand the hammer is reattracted. This action continues as long as thecircuit is closed at any distant point to which it may be carried. Theordinary vibrating bell is a typical automatic circuit breaker, q. V. , this type keeping up the ringing as long as the circuit is closed. Otherbells have no electric contact and simply ring once every time thecircuit is closed. Others worked by an alternating current ring once foreach change of direction of current. 80 STANDARD ELECTRICAL DICTIONARY. Bell, Electro-mechanical. A bell which has its striking train operated by a spring or descendingweight, and which train is thrown into action by the release of a detentor equivalent action by the closing of an electric circuit. It rings forany given time after being started. Bell, Indicating. A bell which by drop-shutter or other indicator connected in circuitwith it, indicates its number or other designation of its call. Bell, Magneto. An electric bell operated by the alternating current from a magnetogenerator. It has a polarized armature and no circuit breaker. Thearmature is attracted first in one direction and then in the other, asthe current alternates and reverses the polarity of the electro-magnet. Bell, Relay. A bell operated by a relay circuit. Bias. In polarized relay the adjustment of the tongue to lie normally againstone or the other contact. (See Relay, Polarized. ) 81 STANDARD ELECTRICAL DICTIONARY. Fig. 58. RESISTANCE COILS SHOWING BIFILAR WINDING. Bifilar Winding. The method followed in winding resistance coils to prevent them fromcreating fields of force. The wire is doubled, and the doubled wirestarting with the bend or bight is wound into a coil. The current goingin opposite senses in the two lays of the winding produces no field offorce. Binary Compound. A chemical compound whose molecule contains only two elements, such aswater (H2 0), lead oxide (Pb 0), and many others. Binding. In a dynamo or motor armature the wire wound around the coils to securethem in place and prevent their disturbance by centrifugal action. Fig. 59. DOUBLE BINDING POST. Fig. 60. BINDING POST, ENGLISH PATTERN. FIG. 61. WOOD SCREW BINDING POST. Binding Posts or Screws. Arrangements for receiving the loose end of a wire of an electriccircuit, and securing such end by a screw. Several constructions areused, as shown here. Sometimes the wire is passed through a hole, and ascrew tapped in at right angles to the hole is screwed down upon thewire. Sometimes the wire is clamped between two shoulders, one on thescrew, the other on the post. The screw is often a flat-headed thumbscrew or has a milled edge. Sometimes the screw has a slot and is turnedby a screw-driver. Several openings are often provided in the same post for differentwires. Binnacle. The case containing a mariner's compass on shipboard. It is enclosedcompletely; it has a glass side or window through which the compass canbe seen, and is provided with one or two lamps arranged to light thecard, while showing as little light as possible outside. 82 STANDARD ELECTRICAL DICTIONARY. Bioscopy, Electric. The diagnosis of life and death by the action of the animal system whensubjected to an electric current or electrification. Bismuth. A metal, one of the elements, atomic weight, 210 ; equivalent, 70;valency, 3; specific gravity, 9. 9. It is a conductor of electricity. Relative Resistance, compressed, (silver = 1) 87. 23Specific Resistance, 131. 2 microhmsResistance of a wire (a) 1 foot long, weighing 1 grain, 18. 44 ohms (b) 1 foot long, 1/1000 inch thick, 789. 3 " (c) 1 meter long, weighing 1 gram, 12. 88 " (d) 1 meter long, 1 millimeter thick, 1. 670 "Resistance of a 1-inch cube 51. 65 microhmsElectro chemical equivalent, . 7350(Hydrogen = . 0105)(See Thermo-electric Series. ) FIGS. 62, 63. INCANDESCENT WIRE FUSE. ABEL'S PATENT. FIG 64. VON EBNER'S FRICTIONAL ELECTRIC MACHINE FOREXPLODING ELECTRIC FUSES OR DETONATORS. Bi-telephone. A pair of telephones arranged with a curved connecting arm or spring, sothat they can be simultaneously applied to both ears. They areself-retaining, staying in position without the use of the hands. 83 STANDARD ELECTRICAL DICTIONARY. Blasting, Electric. The ignition of blasting charges of powder or high explosives by theelectric spark, or by the ignition to incandescence (red or white heat)of a thin wire immersed in or surrounded by powder. Special influence orfrictional electric machines or induction coils are used to producesparks, if that method of ignition is employed. For the incandescentwire a hand magneto is very generally employed. (See Fuse, Electric. ) The cuts, Figs. 62 and 63, show one form of incandescent wire fuse. Thelarge wires are secured to the capsule, so that no strand can come uponthe small wire within the cavity. The cut, Fig. 64, shows a frictional electric machine for igniting sparkfuses. Bleaching, Electric. Bleaching by agents produced or made available by the direct action ofelectricity. Thus if a current under proper conditions is sent through asolution of common salt (sodium chloride), the electrodes being closetogether, the salt is decomposed, chlorine going to one pole and sodiumhydrate to the other. The two substances react upon each other andcombine, forming sodium hypochlorite, which bleaches the tissue immersedin its solution. Block System. A system of signalling on railroads. The essence of the system consistsin having signal posts or stations all along the road at distancesdepending on the traffic. The space between each two signal posts istermed a block. From the signal posts the trains in day time aresignalled by wooden arms termed semaphores, and at night by lanterns. The arms may be moved by hand or by automatic mechanism depending inpart on electricity for carrying out its functions. Thus in theWestinghouse system the semaphores are moved by pneumatic cylinders andpistons, whose air valves are opened and shut by the action of solenoidmagnets, q. V. The current of these magnets is short circuited bypassing trains, so as to let the valves close as the train passes thesignal post. The block system causes the semaphore to be set at "danger"or "caution, " as the train enters the next block. Then the followingtrain is not allowed to enter the block until the safety signal isshown. The Westinghouse system provides for two semaphores on a post, one indicating "danger" as long as the train is on the next block; theother indicating "caution" as long as the train is on the next twoblocks. The rails form part of the circuit, their joints being bridgedby copper wire throughout the block, and being insulated where theblocks meet. Block Wire. In the block system a wire connecting adjacent block-signal towers orsemaphore poles. Blow-pipe. A name sometimes given to an electric experiment illustrating therepulsion of electrified air particles from a point held at highrelative potential. A metallic point, placed on the prime conductor ofan electric friction or influence machine, becomes highly electrified, and the air becoming excited is repelled and acts upon the candle flame. If the candle is placed on the conductor and a point held towards it therepulsion is still away from the point. 84 STANDARD ELECTRICAL DICTIONARY. Blow-pipe, Electric Arc. A name sometimes given to devices for using the voltaic arc to producelocal heating effects. The directive action of the magnet may be used toforce out the arc like a blow-pipe flame, or a blast of air may bedirectly applied for the same purpose. Blue-stone. A trade name for crystallized copper sulphate, used in Daniell's andgravity batteries. Boat, Electric. A boat propelled by electricity. The electricity drives a motor whichactuates a screw propeller. The current is generally supplied by astorage battery. When used on rivers charging stations are establishedat proper places. When the boat is used as a tender or launch for asteam ship, such as a war-vessel, the battery is charged by a plant onboard the ship. From their noiselessness electric boats are peculiarlyavailable for nocturnal torpedo operations, and the universal equipmentof modern war-ships with electric lightning and power plants makes theiruse possible at all points. This type is often termed an electriclaunch, and most or all electric boats fall under this category. Bobbins. A spool of wood or other material wound with insulated wire. In atangent galvanometer the bobbin becomes a ring, with a channel toreceive the winding. As the ring is not infinitely large compared to theneedle the tangent law is not absolutely fulfilled. It is mostaccurately fulfilled (S. P. Thomson) when the depth of the groove orchannel in the radial direction bears to the breadth in the axialdirection the ratio of square root of 3 to the square root of 2 orapproximately 11 : 9 Body Protector. A metallic short circuit connected with the wrists and lower legs of thehuman body, so that if by accident an active circuit is grounded by thehands and body of the workman wearing it, most of the current will passthrough the wire conductors, thus avoiding the vital organs of the body. Boiler Feed, Electric. An apparatus by which an electric current acting on an electro-magnet, or other equivalent device, opens the water supply when the water levelin a boiler sinks too low, and cuts off the water supply as the waterlevel rises. Boiling. In secondary batteries the escape of hydrogen and oxygen gas when thebattery is charged. The bubbling of the escaping gases produces theeffect of boiling. 85 STANDARD ELECTRICAL DICTIONARY. Boll. An absolute, or c. G. S. , unit of momentum; a gram moving at the rate ofone centimeter per second; a gram-kine (see Kine); a unit proposed bythe British Association. Bolometer. An apparatus for detecting small amounts of radiant energy (radiantheat, so called). A coil suspended by a fine wire or filament so as tobe free to rotate under the effect of force is made up of two paralleland equal wires, insulated from each other, but connected so thatparallel currents sent through them go in opposite direction througheach. This coil is hung in a strong electro-magnetic field produced by alarge coil surrounding it. When a current passes through the suspendedcoil no effect will follow, because the oppositely wound portionscounteract each other exactly. In the circuit with one half of thesuspended coil is an exceedingly thin strip of platinum wire. The otherhalf of the coil has no strips. Both halves unite after leaving thecoil. If now the strip of platinum is heated its conductivity isaffected and its half of the coil receives less current than the otherhalf. This disturbs the balance and the coil swings through a small arc. This apparatus may be made very sensitive, so that an increase oftemperature of 1/1400º F. , 9/70000°C. (1/14000º F. ) will be perceptible. Another construction takes the form of a Wheatstone Bridge, q. V. , inwhose arms are introduced resistances consisting of bands of iron, . 5Millimeter wide (. 02 inches), . 004 millimeter (. 00016 inch) thick, andfolded on themselves 14 times so as to make a rectangular grating, 17 x12 millimeters (. 68 x . 48 inch). The least difference of heat applied tothe grating affects the galvanometer. Synonym-Thermic Balance. Boreal Pole. The south pointing pole of the magnet. (See Austral Pole. ) Bot. A colloquial expression for the English Board of Trade unit ofElectrical Supply. It is formed of the initials of the words "Board ofTrade. " (See Unit, Board of Trade. ) Box Bridge. A constriction of Wheatstone's Bridge in which the necessary resistancecoils are contained in a single box with plugs for throwing the coils inand out of circuit, and connections to bring the coils into thedifferent arms of the system. The cut shows a box bridge. Connectionsfor the galvanometer, battery wires, and terminals of the unknownresistance are provided, by which its resistances and the connectionsare brought into the exact relations indicated in the conventionaldiagram of Wheatstone's bridge. (See Wheatstone's Bridge. ) Referring to the cut, the battery wire, say from the zinc plate, connects at A1, thereby reaching A, its true connecting point. To B1 oneend of the galvanometer circuit or lead is attached, thereby reaching B, its true connecting point. To C are connected the other end from thegalvanometer and one end of the unknown resistance. The other end of theunknown resistance, and the other end of the battery wire, in this casefrom the carbon plate, connect to D. At G is an infinity plug, as it iscalled. When out it breaks the circuit. In use after the connections are made the key is depressed and thegalvanometer observed. The resistance is changed until no action of thegalvanometer is produced by closing the circuit when the ratio of theresistances of the arms gives the proportion for calculating the unknownresistances. Synonym--Commercial Wheatstone Bridge, or commercial form of same. Fig. 65. TOP OF BOX BRIDGE. 86 STANDARD ELECTRICAL DICTIONARY. Boxing the Compass. Naming the thirty-two points of the compass in order, and in sequence toany point called out at random. There are many exercises in the relativesailing points and bearings that come under the same head. Thus thedirection of two given points being given by names of the compasspoints, it may be required to state the number of points intervening. Brake, Electro-magnetic. A brake to stop a wheel from rotating. It comprises a shoe, or sometimesa ring, which by electro-magnetic attraction is drawn against therotating wheel, thus preventing it from turning, or tending to bring itto rest. (See Electro-magnet, Annular. ) Fig. 66. ELECTRIC BRAKE. 87 STANDARD ELECTRICAL DICTIONARY. Branch. A conductor branching from a main line. Sometimes the term is restrictedto a principal conductor, from which current is distributed. Branch Block. In electric wiring of buildings, a block of porcelain or other materialwith grooves, holes and screws for the connection of branch wires to amain wire. Its functions are not only to afford a basis for connectingthe wires, but also to contain safety fuses. As when a branch wire istaken off, fuses have to be put in its line, the branch block carriesthese also. One end of each fuse connects with a main wire, the otherend connects with one of the wires of the branch leader or wire. Porcelain is a favorite material for them, as the fusing or "blowingout" of the safety fuses cannot set it on fire. Branch Conductor. A parallel or shunt conductor. Brazing, Electric. Brazing in which the spelter is melted by means of electricity; eithercurrent incandescence or the voltaic arc may be used. It is identical ingeneral with electric welding. (See Welding, Electric. ) Branding, Electric. A system of branding in which the heat of electrically ignited orincandescent conductors is used to produce or burn in the marks upon thesurface. For the alternating current a small transformer is connected toor forms part of the tool. 88 STANDARD ELECTRICAL DICTIONARY. Brassing. The deposition of a coating of brass by electrolysis. The plating bathcontains both copper and zinc. As anode a plate of brass is used. Theoperation must be constantly watched. The deposition of both metals goeson simultaneously, so that a virtual alloy is deposited. By changingthe depth of immersion of the anode the color of the deposit is varied. As a formula for a brassing bath the following are typical. They areexpressed in parts by weight. (a) For iron and steel. I. Sodium Bisulphate, 200 Potassium Cyanide, 70 per cent. , 500 Sodium Carbonate, 1, 000 Water, 8, 000II. Copper Acetate, 125 Zinc Chloride, 100 Water, 2, 000Add the second solution to the first. (b) For zinc. I. Sodium Bisulphate, 700 Potassium Cyanide, 70 per cent. , 1, 000 Water, 20, 000II. Copper Acetate, 350 Zinc Chloride, 350 Aqua Ammoniae, 400 Water, 5, 000Add the second solution to the first. Use a brass anode; add more zinc to produce a greenish color; morecopper for a red color. A weak current gives a red color; a strongcurrent lightens the color. The battery power can be altered, a largeror smaller anode can be used, or a copper or zinc anode can be used tochange the color of the deposit. The bath may vary from 1. 036 to 1. 100sp. Gr. , without harm. Break. A point where an electric conductor is cut, broken, or opened by aswitch or other device, or simply by discontinuity of the wires. Break-down Switch. A switch used in the three-wire system to provide for the discontinuanceof the running of one of the dynamos. By connecting the positive and negative bus wires to one terminal of theactive dynamo, and the neutral bus wire to the other terminal, onedynamo will supply the current and the system operates like a two-wiresystem, but can only be used for half its normal capacity. Breaking Weight. The weight which, applied in tension, will break a prism or cylinder, asan electric current conductor. 89 STANDARD ELECTRICAL DICTIONARY. Breath Figures, Electric. If a conductor is electrified and placed upon a piece of glass, it willelectrify the glass in contact with it by conduction or discharge. Onremoving the conductor the glass remains electrified. The localizedelectrification is shown by breathing gently on the glass, when aspecies of image of the conductor is produced by the condensed moisture. A coin is often used for conductor. Breeze, Electric. A term in medical electricity, used to designate the silent or brushdischarge of high tension electricity. As an instance of its employment, the electric head bath (see Bath, Electric Head, ) may be cited. Thepatient forming one electrode, being insulated and connected to one ofthe conductors, the other conductor, on being brought near his person, discharges into his body. Bridge. (a) A special bar of copper connecting the dynamos to the bus wire, q. V. , in electric lighting or power stations. (b) Wheatstone's bridge, q. V. , and its many modifications, all of whichmay be consulted throughout these pages. British Association Bridge. The type of Wheatstone bridge used by the committee of the associationin determining the B. A. Ohm; the meter bridge, q. V. Broadside Method. A method of determining the magnetic moment of a magnet. The magnet, n, s, under examination is fixed so that it is at right angles to themagnetic meridian, M, R, which passes through its own center and that ofa compass needle. From the deflection of the latter the moment iscalculated. FIG 67. BROADSIDE METHOD. Bronzing. In electro-plating the deposition of a mixture or virtual alloy ofcopper and tin. In general manipulation it resembles the operation ofdepositing gold and silver alloy, or of brassing. For bronzing the following bath is recommended: Prepare each by itself (a) a solution of copper phosphate and (b) asolution of stannous chloride in a solution of sodium pyrophosphate. Fora, dissolve recently precipitated copper phosphate in concentratedsolution of sodium pyrophosphate. For b, add to a saturated solution ofsodium pyrophosphate solution of stannous chloride as long as theprecipitate which is formed dissolves. Of these two solutions add to asolution of sodium pyrophosphate which contains about 1. 75 oz. Of thesalt to the quart, until the precipitate appears quickly and of thedesired color. For anodes use cast bronze plates. Sodium phosphate mustbe added from time to time; if the deposit is too light add coppersolution, if too dark add tin solution. (W. T. Brannt. ) 90 STANDARD ELECTRICAL DICTIONARY. Brush. In electric current generators and motors, the pieces of copper or othermaterial that bear against the cylindrical surface of the commutator arethus termed. Many different constructions have been employed. Some haveemployed little wheels or discs bearing against and rotating on thesurface of the commutator. A bundle of copper strips is often employed, placed flatwise. Sometimes the same are used, but are placed edgewise. Wire in bundles, soldered together at their distant ends have beenemployed. Carbon brushes, which are simply rods or slabs of carbon, areused with much success. Synonym--Collecting Brush. Brush, Carbon. A brush for a dynamo or motor, which consists of a plate or rod ofcarbon, held in a brush holder and pressed against the commutatorsurface. Brushes, Adjustment of. In electric current generators and motors, the brushes which bear uponthe commutator when the machine is in action need occasional adjustment. This is effected by shifting them until sparking between them and thecommutator is nearly or quite suppressed. Fig. 68. BRUSH HOLDER. Brushes, Lead of. In a dynamo electric generator, the lead or displacement in advance ofor beyond the position at right angles to the line connecting the polesof the field magnet, which is given the brushes. In a motor the brushesare set back of the right angle position, or are given a negative lead. (See Lag. ) 91 STANDARD ELECTRICAL DICTIONARY. Brush Holders. The adjustable (generally) clutch or clamps for holding the commutatorbrushes of a dynamo, which keep them in contact with the commutator, andadmit of adjustment by shifting backward and forward of the brushes tocompensate for wear. They are connected to and form part of the rocker, q. V. By rotating the latter the brush-holders and brushes are carriedin one direction or other around the commutator, so as to vary the leadas required. Brush, Pilot. A third brush, used for application to different parts of a revolvingarmature commutator to determine the distribution of potentialdifference between its different members. (See Curve of Distribution ofPotential in Armature. ) One terminal of a volt-meter is connected to oneof the regular brushes, A, of a dynamo; the other to a third brush, p, which is pressed against different portions of the commutator of thedynamo. The readings of the volt-meter are plotted in a curve ofdistribution of potential. Fig. 69. PILOT BRUSH. Brush, Rotating. Brushes for taking off the current from dynamo commutators, or givingcurrent connection to motors, whose ends are in the form of rollerswhich rotate like little wheels, and press against the commutatorsurface. Brush, Third. A third brush is sometimes provided in a dynamo for regulating purposes. Applied to a series machine it adjoins one of the regular brushes anddelivers its current to a resistance, to whose further end the regularcircuit is connected. By a sliding connection the resistance is dividedbetween the third brush circuit and the regular circuit, and by varyingthe position of this contact regulation is obtained. It is to be distinguished from the pilot brush used for determining thecharacteristic of the commutator, although based on the same generalprinciples. Fig. 70. THIRD BRUSH REGULATION. 92 STANDARD ELECTRICAL DICTIONARY. Brush, Wire Gauze. A collecting or commutator brush for a dynamo or motor, which brush ismade of wire gauze rolled up and compressed into shape. Buckling. The bending up and distortion of secondary battery plates. It is largelydue to over-exhausting the batteries. Where the E. M. F. Is neverallowed to fall below 1. 90 volt it is far less liable to occur. Bug. Any fault or trouble in the connections or working of electricapparatus. Bug Trap. A connection or arrangement for overcoming a "bug. " It is said that theterms "bug" and "bug trap" originated in quadruplex telegraphy. Bunsen Disc. In photometry, the Bunsen Disc is a piece of paper upon whose centre aspot is saturated with melted paraffin, or a ring of paraffined surfacesurrounds an untouched central spot. If placed in such a position thatit receives an equal illumination on each side, the spot almostdisappears. It is used on the bar photometer. (See Photometer, Bar. ) Synonym--Grease Spot. 93 STANDARD ELECTRICAL DICTIONARY. Buoy, Electric. A buoy for use to indicate channels or dangers in harbors and elsewhere, which carries an electric light, whose current is supplied by cable fromshore. It has been proposed to use glass tubes exhausted of air andcontaining mercury, which, as moved by the waves, would produce aluminous effect. A fifty-candle power incandescent lamp is an approvedsource of light. Burner, Electric Gas. A gas burner arranged for the flame to be lighted by electricity. Ittakes a great variety of forms. In some cases a pair of terminals arearranged near the flame or a single terminal is placed near the metaltip, the latter forming one of the terminals. The spark is generallyproduced by an induction coil, or a spark coil. The gas may first beturned on and the spark then passed. Sometimes the turning of the gascock of an individual burner makes and breaks a contact as it turns, andthereby produces simultaneously with the turning on of the gas a sparkwhich lights it. Another form is wholly automatic. A pair of electro-magnets are attachedbelow the base of the burner, one of which, when excited, turns on thegas, and the other one when it is excited turns it off. At the same timea spark is produced with the turning on of the gas so that it islighted. Thus, by use of a automatic burner, a distant gas burner can belighted by turning an electric switch. An out-door lamp may be lightedfrom within a house. The increasing use of electric incandescent lamps, lighted by theturning of a switch, tends to displace electric gas burners. The latterhave been classified into a number of types depending on theirconstruction. Burners are sometimes connected in series with leads from an inductioncoil. Then the gas is turned on all at once, and a succession of sparkspassed until the gas is all lighted. The ignition is practicallyinstantaneous. Button, Push. A species of switch which is actuated by the pressure of a button. Inits normal position the button is pressed outwards by a spring, and thecircuit is open. When pressed inwards, it closes the circuit. Whenreleased it springs backward and opens the circuit again. They are principally used for ringing bells. If the latter are of theautomatic type, they ring as long as the button is pressed. For door-bells and room-bells, the button often occupies the center of arosette of wood or bronze or other ornamental piece. Sometimes, as shownin the cut, they are constructed for use on floors to be pressed by thefoot. The general principle of their construction is shown, although themethod of making the contact varies. Synonym--Press Button. Fig. 71. FLOOR PUSH BUTTON. 94 STANDARD ELECTRICAL DICTIONARY. Burning. (a) In a dynamo, the production of shifting and temporary arcs betweenthe commutator and brushes, which arcs produce heat enough to injure theparts in question. (b) In electro-plating, a defect due to too strong a current inproportion to the strength of solution and area of electrodes. Thisgives a black or badly-colored deposit. Bus Rod. A copper conductor used in electric lighting or power stations, toreceive the current from all the dynamos. The distributing leads areconnected to the bus wires. In the three-wire system there are three; in the two-wire system thereare two bus wires. The name is undoubtedly derived from "omnibus. " The bus wires may be divided into positive, negative, and, in thethree-wire system, neutral bus wires. Synonyms--Omnibus Rod, Wire, or Bar--Bus Bar, or Wire. Buzzer. An electric alarm or call produced by a rapid vibration of electric makeand break mechanism, which is often magnified by enclosure in aresonating chamber, resembling a bell, but which is not struck ortouched by the vibrating parts. Sometimes a square wooden box is used asresonator. Fig. 72. BUZZER. 95 STANDARD ELECTRICAL DICTIONARY. B. W. G. Abbreviation for Birmingham Wire Gauge. (See Wire Gauge, Birmingham. ) C. (a) Abbreviation for Centigrade, as 100 C. , meaning 100 Centigrade. (SeeCentigrade Scale. ) (b) A symbol of current or of current strength. Thus in the expressionof Ohm's law C = E/R. C indicates current strength or intensity, not inany fixed unit, but only in a unit of the same order in which E and Rare expressed; E Indicating electro-motive force and R resistance. Cable. (a) Abbreviation for Cablegram, q. V. (b) v. It is also used as a verb, meaning to transmit a message bysubmarine cable. (c). An insulated electric conductor, of large diameter. It often isprotected by armor or metallic sheathing and may be designed for use asan aerial, submarine, subterranean or conduit cable. A cable oftencontains a large number of separately insulated conductors, so as tosupply a large number of circuits. Cable, Aerial. A cable usually containing a large number of separately insulated wires, and itself insulated. It is suspended in the air. As its weight issometimes so great that it could not well sustain it, a suspending wireis in such cases carried along with it, to which it is suspended bycable hangers, q. V. Cable Box. A box for receiving underground cable ends and connecting the separatewires of the cable to air-line wires. It is often mounted on a pole, which forms the starting point of the air-line portion of the system. Cable, Bunched. A cable containing a number of separate and individual conductors. Insome forms it consists virtually of two or more small cables laidtangent to each other and there secured. Thus each in section representstwo or more tangent circles with the interstice solidly filled with themetal sheathing. Cable, Capacity of. The electrostatic capacity of a cable. A cable represents a Leyden jaror static condenser. The outer sheathing or armor, or even the more orless moist coating, if it is unarmored, represents one coating. The wireconductors represent the other coating, and the insulator is thedielectric. The capacity of a cable interferes with its efficiency as a conductor ofbroken or interrupted currents, such as are used in telegraphy ortelephoning. As each impulse or momentary current is sent into the line, it has to charge the cable to at least a certain extent before theeffects of the current are perceptible at the other end. Then the cablehas to discharge itself. All this creates a drag or retardation. The capacity of a cable is used to determine the locality of breaks inthe continuity of the conductors. The capacity per unit of length beingaccurately known, it is obvious that, if the conductor breaks withoutdisturbance of the insulator, the distance of the break from the end canbe ascertained by determining the capacity of the cable from one end. This capacity will be in proportion to the capacity of a mile, a knot orany fixed unit, as the distance to the break is to the length used asstandard. 96 STANDARD ELECTRICAL DICTIONARY. Cable Core. The conductors of a cable. They are generally copper wire. In atelephone cable they may be very numerous and insulated from each other. In ocean cables they may be a group of bare wires twisted or laidtogether. Sometimes the conductors are arranged for metallic circuits, each pair being distinguished by special colored windings. Cable, Duplex. A cable containing two wires, each with separate insulation, so as to bevirtually two cables, laid and secured parallel and side by side. Cable, Flat. A cable, flat in shape, so as to lie closely against a wall or ceiling. Cablegram. A message which has been transmitted or is to be transmitted by asubmarine cable. It is sometimes called a cable. Cable Grip. A grip for holding the end of a cable, when the cable is to be drawninto a conduit in a subway. It is an attachment to provide the cablewith an eye or loop. Its end is a split socket and embraces the end ofthe cable, and is secured thereto by bolts driven through the cable end. In drawing a cable into a conduit a capstan and rope are often used, andthe rope is secured to the cable end by the grip. Fig. 73. CABLE HANGER, CABLE, AND SUSPENDING WIRE. Fig. 74. CABLE HANGER, OPEN. Cable Hanger. When a heavy electric cable is suspended from poles it often would beunsafe to trust to its longitudinal strength to support or sustain itsown weight unless the poles were very near together. In such case anauxiliary or sustaining wire is run along with it, and by clips orhangers the cable is connected thereto at as frequent intervals as seemdesirable. The contrivance may take the form of a strip of metalsurrounding the cable and carrying a hook or eye through which thesupporting wire passes. Synonym--Cable Clip. 97 STANDARD ELECTRICAL DICTIONARY Cable Hanger Tongs. Tongs for attaching cable hangers, q. V. They have long handles so as tobe worked from the ground at the middle of a span. Cable, Suspending Wire of. A wire by which an aerial cable is in part or entirely suspended. Thecable, being incapable of sustaining its own weight, is secured by clipsor hangers to a wire, strong from pole to pole immediately above it. (See Cable Hanger. ) Cable Tank. A tank in which a submarine cable is coiled away on board a cable-layingship, or in the factory on shore for the purpose of testing orwatching its insulation. Sometimes, in order to test it under pressuresapproximating to those it will be subjected to in practice, the tank isclosed and the portion of cable within it is subjected to hydraulicpressure. This represents the pressure it will be exposed to in deepwater. Calamine. A mineral; zinc silicate; formula Zn2 Si 03, crystalline system, Orthorhombic; specific gravity, 3. 16-3. 9. The crystals often show strong pyroelectric properties. Calibration. The determination by experiment or calculation of the value of thereadings of an instrument, such as a galvanometer or eudiometer. Thus ifa tangent galvanometer has its circle graduated in degrees, a table ofthe value of tangents corresponding to every reading occurring inpractice would represent a calibration by calculation. A determinationof the current required to produce each deflection would be acalibration in the more usual sense. Calibration is generally absolute, as referring to some fixed unit, but it may be relative, as between twothings both of unknown absolute value. Calibration, Absolute. The determination of the absolute value of currents producing givendeflections in a galvanometer, or in other instruments the determinationof corresponding values, as the instrument may be a magnetometer, quadrant electrometer, or other apparatus. Calibration, Invariable. Calibration applicable to specially constructed galvanometers, which isunaffected by the proximity of masses of iron or field magnets. Suchgalvanometers must have a constant controlling field. Such is given by apowerful permanent magnet, whose field is practically unaffected by thecauses named. Or else, in place of a controlling field, a spring maybeused to which the needle is attached, and which tends to hold it in oneposition. 98 STANDARD ELECTRICAL DICTIONARY. Calibration, Relative. The determination of the law connecting the various indications of aninstrument, such as the deflections of the needle of a galvanometer, with the relative causes; in the case of a galvanometer, the strength ofthe currents or the electro-motive forces producing them directly orindirectly. Call Bell. A bell rung by pressing a button or otherwise to call the attention of aperson in a distant place. They can be classified into a great varietyof types according to their uses or construction. Call Button. A push button used for ringing a call bell, sounding a buzzer, workingan annunciator and for similar purposes. (See Push Button. ) Synonym--Push Button. Calling Drop. In a telephone exchange or telegraph office a drop shutter annunciator, which falls to call the attention of the operator, notifying him thatthe line connected to such drop is to be connected to some othercircuit. Calorie or Calory. A practical unit of heat. There are two calories, respectively calledthe great and the small calorie, or the kilogram and the gram calorie. The first is the quantity of heat required to raise the temperature ofone kilogram of water one degree centigrade. The second is the quantityof heat required to raise the temperature of one gram of water onedegree centigrade. Calorimeter. An apparatus for measuring the quantity of heat evolved or produced byor under different conditions. Dulong's water calorimeter consists of awater jacket, and by the increase of temperature of the water andenclosing vessels the amount of heat produced by anything in the innervessels is determined. The amount of ice a heated body will melt issometimes made the basis of a calorimeter. The expansion of a fluid, aswater, may be used. In the calorimeter shown in the cut the heatproduced in a conductor by the passage of an electric current is causedto heat water whose temperature is shown by a thermometer immersedtherein. The increase of temperature and the weight of the water givethe basis for a determination of the heat produced by the current. Knowing the resistance of the conductor immersed, the watts can becalculated. This gives the bases for the determination of theheat-equivalent of electric energy. This is but an imperfectcalorimeter, as it constantly would lose heat by the surroundingatmosphere, and would cease to operate as a calorimeter when the waterwas as hot as the wire normally would be, for then it would not absorball the heat. Fig. 75. CALORIMETER. 99 STANDARD ELECTRICAL DICTIONARY. Candle. The generally accepted unit of illuminating power; there arethree kinds in use as standards. (See Candle, Decimal--Candle, GermanStandard--Candle, Standard. ) Candle, Concentric. An electric candle of the Jablochkoff type, having a small solid carboninside of an outside tubular carbon, the space between being filled withrefractory material corresponding to the colombin, q. V. , of theordinary type. The arc springs across from one carbon to the other. Candle, Debrun. An arc lamp with approximately parallel carbons. A transverse primingconnects their bases, and the arc starting there at once flies out tothe end. Candle, Decimal. A standard of illuminating power, proposed to the Congress ofElectricians of 1889 by Picou. It is one-twentieth of a Viole, or almostexactly one standard candle. (See Viole's Standard of IlluminatingPower. ) Candle, Electric. An arc lamp regulated by simple gravity, or without any feed of thecarbons or special feeding apparatus, generally for the production of anarc light of low intensity. This definition may be considered tooelastic, and the word may be restricted to parallel carbon lamps inwhich the arc springs across from carbon to carbon. For the latter classan alternating current is used to keep the carbons of equal length. Theyare but little used now. Various kinds have been invented, some of whichare given here. Candle, German Standard. A standard of illuminating power used in Germany. It is a paraffincandle, 6 to the pound, 20 millimeters diameter; flame, 56 millimetershigh; rate of consumption, 7. 7 grams per hour. Its value is about twoper cent. Lower than the English standard candle. 100 STANDARD ELECTRICAL DICTIONARY. Candle Holder. A clamp for holding electric candles of the Jablochkoff type. The onesshown in the cut designed for Jablochkoff candles comprise a pair ofmetallic clamps, each member insulated from the other, and connected asterminals of the circuit. When the candle is placed in position themetal pieces press against the carbons of the candle and thus convey thecurrent. Below each member of the clamps is a binding screw for the linewire terminals. Fig. 76. JABLOCHKOFF CANDLE HOLDERS. Fig. 77. JABLOCHKOFF CANDLE. Candle, Jablochkoff. An arc lamp without regulating mechanism, producing an arc between theends of parallel carbons. It consists of two parallel rods of carbon, between which is an insulating layer of non-combustible material calledthe colombin. Kaolin was originally employed for this part; later, asthe fusion of this material was found to short- circuit the arc, amixture of two parts of calcium sulphate and one of barium sulphate wasused. The carbons are 4 millimeters (. 16 inch) thick, and the colombinis 3 millimeters (. 12 inch) wide and two-thirds as thick. A little slipof carbon is placed across the top, touching both carbons to start thearc. Once started the candle burns to the end, and cannot be restartedafter ignition, except by placing a short conductor across the ends, asat first. The Jablochkoff candle may now be considered as virtuallyextinct in this country. In France at one time a great number were inuse. To keep the carbons of equal length an alternating current must alwaysbe used with them. Special alternating combinations were employed insome cases where a direct current had to be drawn upon. Candle, Jamin. An arc lamp with approximately parallel carbons, one of which oscillatesand is controlled by an electro-magnet and armature. A coil of wire iscarried around the carbons to keep the arc steady and in place. Theframe and wire coils have been found unsatisfactory, as causing ashadow. Candle Power. The amount of light given by the standard candle. The legal English andstandard American candle is a sperm candle burning two grains a minute. It should have burned some ten minutes before use, and the wick shouldbe bent over and have a red tip. Otherwise its readings or indicationsare useless. A sixteen candle power lamp means a lamp giving the lightof sixteen candles. The candle power is a universal unit of illuminatingpower. 101 STANDARD ELECTRICAL DICTIONARY. Candle Power, Rated. The candle power of arc lamps is always stated in excess of the truth, and this may be termed as above. A 2000 candle power lamp really givesabout 800 candles illumination. Synonym--Nominal Candle Power. Candle Power, Spherical. The average candle power of a source of light in all directions. An arclamp and an incandescent lamp vary greatly in the intensity of lightemitted by them in different directions. The average of a number ofdeterminations at various angles, the lamp being moved about intodifferent positions, is taken for the spherical candle power. Candle, Standard. A standard of illuminating power. Unless otherwise expressed the Englishstandard sperm candle is indicated by this term. (See Candle Power. ) Candle, Wilde. An arc lamp with approximately parallel carbons. One of the carbons canrotate through a small arc being pivoted at its base. This oscillationis regulated by an electro-magnet at its base, and the carbons touchwhen no current is passing. They separate a little when the currentpasses, establishing an arc. The regulation is comparable to that of aregular arc lamp. Fig. 78. WILDE CANDLE. Caoutchouc. India rubber; a substance existing in an emulsion or solution in thejuice of certain trees and vines of the tropics, whence it is obtainedby coagulation and drying. The name "rubber" is due to the fact that oneof its earliest uses was for erasing pencil marks by rubbing. It has avery high value as an insulator. The unworked crude rubber is calledvirgin gum; after working over by kneading, it is termed masticated orpure gum rubber; after mixture with sulphur and heating, it is termedvulcanized rubber. If enough sulphur is added it becomes hard, and ifblack, is termed ebonite; if vermilion or other pigment is also added toproduce a reddish color, it is termed vulcanite. The masticated gumdissolves more or less completely in naphtha (sp. Gr. , . 850) benzole, turpentine, chloroform, ether and other similar liquids.. The resistanceper centimeter cube of "Hooper's" vulcanized India rubber, such as isused in submarine cables is 1. 5E16 ohms. The specific inductive capacityof pure India rubber is 2. 34--of vulcanized 2. 94 (Schiller). Synonyms--India Rubber--Rubber. 102 STANDARD ELECTRICAL DICTIONARY. Capacity, Dielectric. The capacity of a dielectric in retaining an electrostatic charge; thesame as Specific Inductive Capacity. 'The number expressing it issometimes called the dielectric constant. (See Capacity, SpecificInductive. ) Capacity, Electric, or Electrostatic. The relative capacity of a conductor or system to retain a charge ofelectricity with the production of a given difference of potential. Thegreater the charge for a given change of potential, or the less thechange of potential for a given charge the greater the capacity. Themeasure of its capacity is the amount of electricity required to raisethe potential to a stated amount. The unit of capacity is the farad, q. V. Electric capacity is comparable to the capacity of a bottle for air. A given amount of air will raise the pressure more or less, and theamount required to raise its pressure a stated amount might be taken asthe measure of capacity, and would be strictly comparable toelectrostatic charge and potential change. The capacity, K, is obviouslyproportional to the quantity, Q, of the charge at a given potential, E, and inversely proportional to the potential, E, for a given quantity, Q, or, (1) K == Q/E and (2) Q = K * E, or, the quantity required to raise a conductor by a given potential isequal to the capacity of the conductor or system multiplied by the riseof potential. The capacity of a conductor depends upon its environments, such as the nature of the dielectric surrounding it, the proximity ofoppositely charged bodies and other similar factors. (SeeDielectric-Condenser-Leyden jar. ) The dimensions of capacity are found by dividing a quantity ofelectricity by the potential produced in the conductor by suchquantity. Quantity ( ((M^. 5)*(L^1. 5)) / T ) / potential ( ((M^. 5)*(L^. 5)) / T ) = L. Capacity, Instantaneous. The capacity of a condenser when connected only for an instant to asource of electricity. This is in contrast to electric absorption (seeAbsorption, Electric), and is capacity without such absorption takingpart in the action. 103 STANDARD ELECTRICAL DICTIONARY. Capacity of a Telegraph Conductor. The electric capacity of a telegraphic conductor is identical in qualitywith that of any other conductor. It varies in quantity, not only fordifferent wires, but for the same wire under different environments, asthe wire reacting through the surrounding air or other dielectric uponthe earth, represents one element of a condenser, the earth, in general, representing the other. Hence, a wire placed near the earth has greatercapacity than one strung upon high poles, although the wires may beidentical in length, material and diameter. The effect of high capacityis to retard the transmission of intermitting signals. Thus, when--as inthe Morse system--a key is depressed, closing a long telegraph currentand sending a signal into a line, it is at least very probable that aportion of the electricity travels to the end of the wire with thevelocity of light. But as the wire has to be charged, enough current tomove the relay may not reach the end for some seconds. Capacity of Polarization of a Voltaic Cell. The relative resistance to polarization of a voltaic cell, measured bythe quantity of electricity it can supply before polarization. Acounter-electromotive force may be developed, or the acid or othersolution may become exhausted. The quantity of electricity deliveredbefore this happens depends on the size and type of cell and otherfactors. Capacity, Residual. When two insulated conductors are separated by a dielectric, and aredischarged disruptively by being connected or nearly connectedelectrically, on removing the discharger it is found that a slightcharge is present after a short interval. This is the residual charge. (See Charge, Residual. ) Shaking or jarring the dielectric facilitatesthe complete discharge. This retaining of a charge is a phenomenon ofthe dielectric, and as such, is termed residual capacity. It variesgreatly in different substances. In quartz it is one-ninth what it is inair. Iceland spar (crystalline calcite) seems to have no residualcapacity. The action of shaking and jarring in facilitating a dischargeindicates a mechanical stress into which the electrostatic polarizationof the conductor has thrown the intervening dielectric. Capacity, Specific Inductive. The ratio of the capacity of a condenser when its plates are separatedby any substance to the capacity of the same condenser when its platesare separated by air. A static accumulator consists of two conducting surfaces separated by aninsulator. It is found that the capacity of an accumulator for anelectric charge, which varies with or may be rated by the potentialdifference to which its conductors will be brought by the given charge, varies with the nature of the interposed dielectric, and is proportionalto a constant special to each substance. This constant is the specificinductive capacity of the dielectric. The same condenser will have a higher capacity as the dielectric isthinner, other things being equal. But different dielectrics havingdifferent specific inductive capacities, the constant may be determinedby ascertaining the relative thicknesses of layers having the same totalinductive capacity. The thicker the layer, the higher is its specificinductive capacity. Thus it is found that 3. 2 units thickness of sulphur have the same totalinductive capacity as 1 unit thickness of air. In other words, ifsulphur is interposed between two conducting plates, they may beseparated to over three times the distance that would be requisite toretain the same capacity in air. Hence, sulphur is the betterdielectric, and air being taken as unity, the specific inductivecapacity of sulphur is 3. 2. 104 STANDARD ELECTRICAL DICTIONARY. The specific inductive capacity of a dielectric varies with the time andtemperature. That of glass rises 2. 5 per cent. Between 12° C. (53. 6° F. )and 83° C. (181. 4° F. ). If a condenser is discharged disruptively, itretains a small residual charge which it can part with later. If ametallic connection is made between the plates, the discharge is notinstantaneous. Vibration shaking and jarring facilitate the completedischarge. All this shows that the charge is a phase of the dielectricitself, and indicates a strained state into which it is brought. The following table gives the specific inductive capacity of varioussubstances: Specific Inductive Capacity. Substance Specific Inductive Authority Capacity. Vacuum, air at about 0. 001 millimeters pressure 0. 94 about AyrtonVacuum, air at about 5 millimeters 0. 9985 Ayrton 0. 99941 BoltzmannHydrogen at about 760 millimeters pressure 0. 9997 Boltzmann 0. 9998 AyrtonAir at about 760 millimeters pressure 1. 0 Taken as the standardCarbon Dioxide at about 760 millimeters pressure 1. 000356 Boltzmann 1. 0008 AyrtonOlefiant Gas at about 760 millimeters pressure 1. 000722 BoltzmannSulphur Dioxide at about 760 millimeters pressure 1. 0037 AyrtonParaffin Wax, Clear 1. 92 Schiller 1. 96 Wüllner 1. 977 Gibson and Barclay 2. 32 BoltzmannParaffin Wax, Milky 2. 47 SchillerIndia Rubber, Pure 2. 34 SchillerIndia Rubber, Vulcanized 2. 94 SchillerResin 2. 55 BoltzmannEbonite 2. 56 Wüllner 2. 76 Schiller 3. 15 BoltzmannSulphur 2. 88 to 3. 21 Wüllner 3. 84 BoltzmannShellac 2. 95 to 3. 73 WüllnerGutta percha 4. 2Mica 5Flint Glass, Very light 6. 57 J. HopkinsonFlint Glass, Light 6. 85 J. HopkinsonFlint Glass, Dense 7. 4 J. HopkinsonFlint Glass, Double extra dense 10. 1 J. Hopkinson 105 STANDARD ELECTRICAL DICTIONARY. Capacity, Unit of. The unit of capacity is the capacity of a surface which a unit quantitywill raise to a unit potential. The practical unit is the surface whicha coulomb will raise to one volt, and is called the farad, q. V. Capacity, Storage. In secondary batteries the quantity of electrical current which they cansupply when charged, without undue exhaustion. It is expressed inampere-hours. The potential varies so little during the discharge thatit is assumed to be constant. Capillarity. The reaction between liquid surfaces of different kinds or betweenliquid and solid surfaces due to surface tension. Its phenomena aregreatly modified by electric charging, which alters the surface tension. Capillarity is the cause of solutions "creeping, " as it is termed. Thusin gravity batteries a crust of zinc sulphate often formed over the edgeof the jar due to the solution creeping and evaporating. As a liquidwithdraws from a surface which it does not wet, creeping as above isprevented by coating the edge with paraffin wax, something which waterdoes not moisten. It also causes the liquids of a battery cell to reachthe connections and injure them by oxidation. The solutions creep up inthe pores of the carbons of a battery and oxidize the clamps. To givegood connections a disc of platinum or of lead is used for the contactas not being attacked. Another way is to dip the upper ends of the dryand warm carbons into melted paraffin wax, or to apply the wax to thehot carbons at the top, and melt it in with a hot iron. 106 STANDARD ELECTRICAL DICTIONARY. Carbon. (a) One of the elements; atomic weight, 12. It exists in threeallotropic modifications, charcoal, graphite and diamond. In thegraphitic form it is used as an electric current conductor, as inbatteries and for arc lamp, electrodes and incandescent lamp filaments. It is the only substance which conducts electricity and which cannot bemelted with comparative ease by increase of current. (See Resistance. ) (b) The carbon plate of a battery or rod of an arc lamp. To securegreater conductivity in lamp carbons, they are sometimes plated withnickel or with copper. (c) v. To place carbons in arc lamps. This has generally to be done oncein twenty-four hours, unless the period of burning is very short. Carbon, Artificial. For lamps, carbons and battery plates carbons are made by igniting, while protected from the action of the air, a mixture of carbon dust anda cementing and carbonizable substance. Lamp black may be added also. Powdered coke or gas carbon is mixed with molasses, coal tar, syrup, orsome similar carbonaceous liquid. It is moulded into shape. For lampcarbons the mixture is forced from a vessel through a round aperture ordie, by heavy pressure, and is cut into suitable lengths. For batteryplates it may be simply pressed into moulds. The carbons are ignited incovered vessels and also covered with charcoal dust, lamp black or itsequivalent. They are heated to full redness for some hours. Afterremoval and cooling they are sometimes dipped again into the liquid usedfor cementing and reignited. Great care in securing pure carbon issometimes necessary, especially for lamps. Fine bituminous coal issometimes used, originally by Robert Bunsen, in 1838 or 1840;purification by different processes has since been applied; carbon fromdestructive distillation of coal tar has been used. The famous Carrécarbons are made, it is said, from 15 parts very pure coke dust, fiveparts calcined lamp-black, and seven or eight parts sugar--syrup mixedwith a little gum. Five hours heating, with subsequent treatment withboiling caramel and reignition are applied. The latter treatment istermed "nourishing. " Napoli used three parts of coke to one of tar. Sometimes a core of different carbon than the surrounding tube isemployed. 107 STANDARD ELECTRICAL DICTIONARY. The following are the resistances of Carré's carbons per meter (39. 37inches): Diameter in Diameter in Resistance in Ohms. Millimeters. Inches. @ 20° C. (98° F. ) 1 . 039 50. 000 2 . 078 12. 5 3 . 117 5. 55 4 . 156 3. 125 5 . 195 2. 000 6 . 234 1. 390 8 . 312 . 781 10 . 390 . 5 12 . 468 . 348 15 . 585 . 222 18 . 702 . 154 20 . 780 . 125 At high temperatures the resistance is about one-third these amounts. Alayer of copper may increase the conductivity one hundred times andprolong the duration 14 per cent. Thus a layer of copper 1/695millimeter (1/17300 inch) thick increases the conductivity 4. 5 times; acoating 1/60 millimeter (1/1500 inch) thick increases the conductivityone hundred and eleven times. Carbon, Cored. A carbon for arc lamps with a central core of softer carbon than theexterior zone. It fixes the position of the arc, and is supposed to givea steadier light. Synonym--Concentric Carbon. Carbon Holders. In arc lamps, the fixed clamps for holding the ends of the carbons. Carbonization. The igniting in a closed vessel, protected from air, of an organicsubstance so as to expel from it all the constituents except part ofthe carbon; destructive distillation. (See Carbonized Cloth. ) Carbonized Cloth. Cloth cut in discs and heated in vessels protected from the air, untilreduced to carbon. The heating is sometimes conducted in vacuo. They areplaced in a pile in a glass or other insulating tube, and offer aresistance which can be varied by pressure. The greater the pressure theless will be the resistance, and vice versa. Carbon Dioxide. A compound gas, CO2. It is composed of Carbon, 12 parts by weight. Oxygen. 32 " Specific gravity, 1. 524 (Dulong and Berzelins). Molecular weight, 44. It is a dielectric of about the resistance of air. Its specificinductive capacity at atmospheric pressures is 1. 000356 (Boltzmann). 1. 0008 (Ayrton). Synonyms--Carbonic Acid--Carbonic Acid Gas. 108 STANDARD ELECTRICAL DICTIONARY Carbon, Volatilization of. In arc lamps the heat is so intense that it is believed that part of thecarbon is volatilized as vapor before being burned or oxidized by theoxygen of the air. The same volatilization may take place inincandescent lamps which are overheated. Carcel. The standard of artificial illumination used in France. It is the lightyielded by a standard lamp burning 42 grams (648 grains) of colza oilper hour, with a flame 40 millimeters (1. 57 inch) in height. One carcelis equal to 9. 5 to 9. 6 candles. Carcel Lamp. The lamp giving the standard of illuminating power. The wick iscylindrical, giving an Argand or central draft flame. It is woven with75 strands, and weighs 3. 6 grams (55. 5 grains) per decimeter (3. 9inches) of length. The chimney is 29 centimeters (11. 3 inches) high, 47millimeters (1. 88 inch) in diameter at the bottom, contracting justabove the wick to 34 millimeters (1. 36 inch). Carcel Gas Jet. A standard Argand gas burner, made with proper rating to give the lightof a definite number of carcels illuminating power. Cognizance must betaken of the quality of the gas as well as of the burner used. Carrying Capacity. In a current conductor, its capacity for carrying a current withoutbecoming unduly heated. It is expressed in amperes. (See Wire Gauge, American. ) Cascade. The arrangement of Leyden jars in series on insulating supports, asdescribed below. Cascade, Charging and Discharging Leyden Jars In. An arrangement of Leyden jars in series for the purpose of charging anddischarging. They are placed on insulating supports, the inner coatingof one connected with the outer coating of the next one all through theseries. The actual charge received by such a series, the outer coatingof one end jar being grounded, and the inner coating of the other beingconnected to a source of high potential, or else the same beingconnected to electrodes of opposite potentials is no greater than thatof a single jar, but a much higher potential difference can be developedwithout risk of perforating the glass of a jar. The difference ofpotential in each jar of the series is equal to the total potentialdifference divided by the number of jars. The energy of discharge isequal to the same fraction of the energy of a single jar charged withthe same quantity. [Transcriber's note: The equal distribution of potential assumes all thejars have the same capacity. The charge on all jars is the same sincethey are in series. ] 109 STANDARD ELECTRICAL DICTIONARY. Case-hardening, Electric. The conversion of the surface of iron into steel by applying a propercarbonaceous material to it while it is heated by an electric current. It is a superficial cementation process. Cataphoresis. Electric osmore; the transfer of substances in solution through porousmembranes under the influence probably of electrolysis, but withoutthemselves being decomposed. Cautery, Electric. An electro-surgical appliance for removing diseased parts, or arrestinghemorrhages, taking the place of the knife or other cutting instrument. The cautery is a platinum wire heated to whiteness by an electriccurrent, and when in that condition used to cut off tumors, stop theflow of blood and parallel operations. The application is painful, butby the use of anaesthetics pain is avoided, and the healing after theoperation is greatly accelerated. The heated wire of the cautery can be used for cutting operations inmany cases where excision by a knife would be almost impracticable. Synonyms--Galvano-cautery--Galvano-caustry--Galvano-electric, do. --Galvano-thermal, do. C. C. A contraction of cubic centimeter. It is often written in small letters, as 100 c. C. , meaning 100 cubic centimeters. Cell, Constant. A cell which yields a constant and uniform current under unvaryingconditions. This implies that neither the electro-motive force or theresistance of the cell shall vary, or else that as the electro-motiveforces run down the resistance shall diminish in proper proportion tomaintain a constant current. There is really no constant cell. Theconstancy is greatest when the external resistance is high in proportionto the internal resistance. Cell, Electrolytic. A vessel containing the electrolyte, a liquid decomposable by thecurrent, and electrodes, arranged for the passage of a decomposingcurrent. The voltameter, q. V. , is an example. Cell, Standard Voltaic. A cell designed to be a standard of electro-motive force; one in whichthe same elements shall always be present under the same conditions, soas to develop the same electro-motive force. In use the circuit isclosed only for a very short time, so that it shall not become alteredby polarization or exhaustion. Cell, Standard Voltaic, Daniell's. A zinc-copper-copper sulphate couple. Many forms are used. Sometimes anumber of pieces of blotting paper are interposed between two plates, one of copper--the other of zinc. The paper next the copper is soaked incopper sulphate solution, and those next the zinc in zinc sulphatesolution, of course before being put together. Sometimes the ordinaryporous cup combination is employed. The cut shows a modification due toDr. Fleming (Phil. Mag. S. 5, vol. Xx, p. 126), which explains itself. The U tube is 3/4-inch diameter, and 8 inches long. Starting with itempty the tap A is opened, and the whole U tube filled with zincsulphate solution, and the tap A is closed. The zinc rod usually kept inthe tube L is put in place, tightly corking up its end of the U tube. The cock C is opened, which lowers the level of the solution in theright-hand limb of the U tube only. The tap B is opened and the coppersulphate solution is run in, preserving the line of separation of thetwo solutions. The copper rod is taken out of its tube M, and is put inplace. India rubber corks are used for both rods. As the liquids beginto mix the mixture can be drawn off at C and the sharp line ofdemarcation re-established. In Dr. Sloane's standard cell two test tubesare employed for the solutions and a syphon is used to connect them. Oxidation of the zinc lowers the E. M. F. ; oxidation of the copperraises it. With solutions of equal sp. Gr. The E. M. F. Is 1. 104 volts. If the copper sulphate solution is 1. 100 sp. Gr. And the zinc sulphatesolution 1. 400 sp. Gr. , both at 15° C. (59°F. ), the E. M. F. Will be1. 074 volt. Clean pure zinc and freshly electrolyzed copper should beused. Fig. 79 STANDARD DANIELL CELL--FLEMING'S FORM. 110 STANDARD ELECTRICAL DICTIONARY. Cell, Standard Voltaic, Latimer Clark's. A mercury and zinc electrode couple with mercurous sulphate as excitantand depolarizer. The positive element is an amalgam of zinc, thenegative is pure mercury. Each element, in a representative form, the Hform, is contained in a separate vessel which communicate by a tube. Over the pure mercury some mercurous sulphate is placed. Both vesselsare filled to above the level of the connecting tube with zinc sulphatesolution, and kept saturated. It is tightly closed or corked. The E. M. F. At 15° C (59° F. ) is 1. 438. Temperature correction (1 - (. 00077 *(t - 15° C) ) ) t being expressed in degrees centigrade (Rayleigh). A diminution inspecific gravity of the zinc solution increases the E. M. F. The cellpolarizes rapidly and the temperature coefficient is considered toohigh. Fig. 80. LATIMER CLARK'S STANDARD CELL. 111 STANDARD ELECTRICAL DICTIONARY. Cements, Electrical. A few cements find their use in electrical work. Marine glue, Chatterton's compound, and sealing wax may be cited. Centi-. Employed as a prefix to indicate one-hundredth, as centimeter, theone-hundredth of a meter; centi-ampere, the one-hundredth of an ampere. Centigrade-scale. A thermometer scale in use by scientists of all countries and in generaluse in many. The temperature of melting ice is 0º; the temperature ofcondensing steam is 100° ; the degrees are all of equal length. Toreduce to Fahrenheit degrees multiply by 9 and divide by 5, and add 32algebraically, treating all readings below 0º as minus quantities. Forits relations to the Reamur scale, see Reamur Scale. Its abbreviation isC. , as 10º C. , meaning ten degrees centigrade. Centimeter. A metric system unit of length; one-hundredth of a meter; 0. 3937 inch. The absolute or c. G. S. Unit of length. Centimeter-gram-second System. The accepted fundamental or absolute system of units, called the C. G. S. System. It embraces units of size, weight, time, in mechanics, physics, electricity and other branches. It is also called the absolutesystem of units. It admits of the formation of new units as required byincreased scope or classification. The following are basic units of thesystem : Of length, centimeter;of mass, gram;of time, second:of force, dyne:of work or energy, erg. See Dyne, Erg. , and other units in general. 112 STANDARD ELECTRICAL DICTIONARY. Central Station Distribution or Supply. The system of supplying electric energy in current form from a maingenerating plant to a district of a number of houses, factories, etc. Itis in contrast with the isolated plant system in which each house orfactory has its own separate generating installment, batteries ordynamos. Centre of Gravity. A point so situated with respect to any particular body, that theresultant of the parallel attracting forces between the earth and theseveral molecules of the body always passes through it. These areresultants of the relative moments of the molecules. If a body issuspended, as by a string, the centre of gravity always lies verticallyunder its point of suspension. By two trials the point of intersectionof plumb lines from the point of suspension being determined the centreof gravity is known. The vertical from the point of support coincideswith the line of direction. Centre of Gyration. The centre of gyration with respect to the axis of a rotating body is apoint at which if the entire mass of the body were concentrated itsmoment of inertia would remain unchanged. The distance of this pointfrom the axis is the radius of gyration. Centre of Oscillation. The point referred to in a body, suspended or mounted to swing like apendulum, at which if all the mass were concentrated, 1t would completeits oscillations in the same time. The distance from the axis of supportto this point gives the virtual length of the pendulum which the bodyrepresents. Centre of Percussion. The point in a suspended body, one free to swing like a pendulum, atwhich an impulse may be applied, perpendicular to the plane through theaxis of the body and through the axis of support without shock to theaxis. It is identical with the centre of oscillation, q. V. , when suchlies within the body. Centrifugal Force. The force which draws a body constrained to move in a curved path awayfrom the centre of rotation. It is really due to a tangential impulseand by some physicists is called the centrifugal component of tangentialvelocity. It has to be provided against in generator and motorarmatures, by winding them with wire or bands to prevent the coils ofwire from spreading or leaving their bed upon the core. 113 STANDARD ELECTRICAL DICTIONARY. Centrifugal Governor. The usual type of steam-engine governor. The motion of the enginerotates a system of weights, which are forced outward by centrifugalforce, and are drawn inwards by gravity or by springs. Moving outwardsthey shut off steam, and moving inwards they admit it, thus keeping theengine at approximately a constant speed. The connections between themand the steam supply and the general construction vary widely indifferent governors. C. G. S. Abbreviation or symbol for Centimeter-gram-second, as the C. G. S. System. (See Centimeter-gram-second System. ) It is sometimes expressedin capitals, as above, and sometimes in small letters, as the c. G. S. Unit of resistance. Chamber of Incandescent Lamp. The interior of the bulb of an incandescent lamp. (See Lamp, Incandescent. ) Fig. 81. CHARACTERISTIC CURVE OF A DYNAMO. FIG. 82. DROOPING CHARACTERISTIC. Characteristic Curve. A curve indicating the variations in electro-motive force developedduring the rotations of the armature of a dynamo or other generator ofE. M. F. The term as used in the electrical sense is thus applied, although the indicator diagram of a steam engine may be termed itscharacteristic curve, and so in many other cases. As the amperes takenfrom a series generator are increased in number, the E. M. F. Rises, itmay be very rapidly up to a certain point, and thereafter more slowly. To construct the curve coordinates, q. V. , are employed. The resistanceof the dynamo and of the outer circuit being known, the currentintensity is measured. To obtain variations in electro-motive force theexternal resistance is changed. Thus a number of ampere readings withvarying known resistance are obtained, and for each one anelectro-motive force is calculated by Ohm's law. From these data a curveis plotted, usually with volts laid off on the ordinate and amperes onthe abscissa. By other methods other characteristic curves may be obtained, for whichthe titles under Curve may be consulted. 114 STANDARD ELECTRICAL DICTIONARY. Characteristic, Drooping. A characteristic curve of a dynamo which indicates a fall in voltagewhen an excessive current is taken from the dynamo in question. It isshown strongly in some Brush machines, and is partly due to thearrangements for cutting out two of the coils as they approach theneutral line. It is an advantage, as it protects from overheating onshort circuit. Characteristic, External. In a dynamo the characteristic curve in which the relations of voltsbetween terminals to amperes in the outer circuit are plotted. (SeeCurve, External Characteristic. ) Characteristic, Internal. A characteristic curve of a shunt dynamo, in which the relations ofvolts to amperes in the shunt circuit is plotted. Characteristics of Sound. Of interest, electrically, as affecting the telephone, they comprise: (1) Pitch, due to frequency of vibrations. (2) Intensity or loudness, due to amplitude of waves of sound. (3) Quality or timbre, the distinguishing characteristics of anyspecific sound due to overtones, discords, etc. , by which the sound isrecognizable from others. The telephone is held by the U. S. Courts tobe capable of reproducing the voice by means of the undulatory current. (See Current, Undulatory. ) Charge. The quantity of electricity that is present on the surface of a body orconductor. If no electricity is supplied, and the conductor is connectedto the earth, it is quickly discharged. A charge is measured by theunits of quantity, such as the coulomb. The charge that a conductor canretain at a given rise of potential gives its capacity, expressible inunits of capacity, such as the farad. A charge implies the stretching orstraining between the surface of the charged body, and somecomplimentary charged surface or surfaces, near or far, of large orsmall area, of even or uneven distribution. Charge. V. (a) To introduce an electrostatic charge, as to charge a condenser. (b) To decompose the elements of a secondary battery, q. V. , so as torender it capable of producing a current. Thus, a spent battery ischarged or recharged to enable it to do more work. Synonyms--Renovate--Revivify--Recharge. 115 STANDARD ELECTRICAL DICTIONARY. Charge, Bound. A charge of electricity borne by the surface of a body so situated withreference to another oppositely charged body, that the charge isimperceptible to ordinary test, will not affect an electroscope norleave the surface if the latter is connected to the earth. To dischargesuch a body it must be connected to its complimentarily charged body. The bound charge was formerly called dissimulated or latent electricity. (See Charge, Free. ) The charge or portion of a charge of a surface which is neutralizedinductively by a neighboring charge of opposite kind. The degree ofneutralization or of binding will depend on the distance of the twocharged surfaces from one another and on the electro-static nature ofthe medium intervening, which must of necessity be a dielectric. Acharge not so held or neutralized is termed a free charge. Thus asurface may be charged and by the approach of a surface less highlycharged may have part of its charge bound. Then if connected to earth. It will part with its unbound or free charge, but will retain the otheruntil the binding surface is removed, or until the electricity of suchsurface is itself bound, or discharged, or until connection is madebetween the two surfaces. Thus a body may have both a bound and a freecharge at the same time. Charge, Density of. The relative quantity of electricity upon a given surface. Thus acharged surface may have an evenly distributed charge or one of evendensity, or an unevenly distributed charge or one of uneven density. Ina thunderstorm the earth has a denser charge under the clouds thanelsewhere. Synonym--Electrical Density. Charge, Dissipation of. As every body known conducts electricity, it is impossible so toinsulate a surface that it will not lose its charge by leakage. Anabsolute vacuum might answer, and Crookes in a high vacuum has retaineda charge against dissipation for years. The gradual loss is termed asabove. Charge, Distribution of. The relation of densities of charge on different parts of a chargedbody. On a spherical conductor the charge is normally of evendistribution; on other conductors it is unevenly distributed, being ofgreatest density at points, edges, and parts of smallest radius ofcurvature. Even distribution can also be disturbed by local induction, due to the presence of oppositely charged bodies. 116 STANDARD ELECTRICAL DICTIONARY. Charge, Free. The charge borne by an insulated body, independent of surroundingobjects. Theoretically it is an impossibility. A charge always has itscompliment somewhere in surrounding objects. As a matter of convenienceand convention, where the complimentary charge is so distributed thatits influence is not perceptible the charge is called a free charge. Ifconnected to earth the free charge will leave the body. If the body isconnected with an electroscope the free charge will affect the same. (See Charge, Bound. ) Charge, Residual. When a Leyden jar or other condenser is discharged by the ordinarymethod, after a few minutes standing a second discharge of less amountcan be obtained from it. This is due to what is known as the residualcharge. It seems to be connected in some way with the mechanical ormolecular distortion of the dielectric. The jarring of the dielectricafter discharge favors the rapidity of the action, diminishing the timerequired for the appearance of the residual charge. The phenomenon, itwill be seen, is analogous to residual magnetism. This charge is thereciprocal of electric absorption and depends for its amount upon thenature of the dielectric. (See Absorption, Electric, and Capacity, Residual. ) Synonym--Electric Residue. Chatterton's Compound. A cement used for cementing together layers or sheets of gutta percha, and for similar purposes in splicing telegraph cables. Its formula is: Stockholm Tar, 1 part. Resin, 1 part. Gutta Percha, 3 parts. All parts by weight. Chemical Change. When bodies unite in the ratio of their chemical equivalents, so as torepresent the satisfying of affinity or the setting free of thermal orother energy, which uniting is generally accompanied by sensible heatand often by light, as in the ignition of a match, burning of a candle, and, when the new compound exhibits new properties distinct from thoseof its components, a chemical combination is indicated. More definitelyit is a change of relation of the atoms. Another form of chemical changeis decomposition, the reverse of combination, and requiring or absorbingenergy and producing several bodies of properties distinct from those ofthe original compound. Thus in a voltaic battery chemical combinationand decomposition take place, with evolution of electric instead ofthermal energy. Chemical Equivalent. The quotient obtained by dividing the atomic weight, q. V. , of anelement by its valency, q. V. Thus the atomic weight of oxygen is 16, its valency is 2. Its chemical equivalent is 8. It is the weight of theelement corresponding to a unit weight of hydrogen, either as replacingit, or combining with it. In electro-chemical calculations the chemicalequivalent is often conveniently used to avoid the necessity of dividingby the valency when atomic weights are used. The latter is really thebetter practice. The atomic weights in the old system of chemicalnomenclature were chemical equivalents. 117 STANDARD ELECTRICAL DICTIONARY. Chemical Recorder. A form of telegraphic recorder in which the characters, often of theMorse alphabet or some similar one, are inscribed on chemically preparedpaper by decomposition affecting the compound with which the paper ischarged. In the original chemical recorder of Bain, the instrument wassomewhat similar to the Morse recorder, except that the motionlessstylus, S, always pressing against the paper was incapable of making anymark, but being of iron, and the paper strip being impregnated withpotassium ferrocyanide, on the passage of a current a stain of Prussianblue was produced where the stylus touched the paper. The current passesfrom the line by way of the iron stylus, through the paper, and by wayof a brass surface, M, against which the paper is held and is pressed bythe stylus, to the earth. This recorder is extremely simple and has nopart to be moved by the current. The solution in which the paper isdipped contains a mixture of potassium ferrocyanide and ammoniumnitrate. The object of the latter is to keep the paper moist. In recentrecorders a solution of potassium iodide has been used, which gives abrown stain of free iodine, when the current passes. This staindisappears in a few days. Fig. 83. BAIN'S TELEGRAPH EMPLOYING CHEMICAL RECORDER. In the cut, R is the roll of paper, B is a tank of solution with roll, W1, for moistening the paper; M is the brass surface against which thestylus, S, presses the paper, P P; W, W are feed rollers; T is thetransmitting key, and zk the battery; Pl, Pl are earth plates. Theapparatus is shown duplicated for each end. 118 STANDARD ELECTRICAL DICTIONARY. Chemistry. The science treating of atomic and molecular relations of the elementsand of chemical compounds of the same. Chimes, Electric. An apparatus employed to illustrate the principles of the electrostaticcharge, involving the ringing of bells by electrostatic attraction andrepulsion. It is used in connection with a frictional, or influenceelectric machine. Two bells are employed with a button or clappersuspended between them. One bell is connected to one of the primeconductors, q. V. , of the machine. The other insulated therefrom isconnected to earth, or if an influence machine is used, to the otherprime conductor. The clappers are hung by a silk thread, so as to beentirely insulated. On working the machine the bells become oppositelyexcited. A clapper is attracted to one, then when charged is repelledand attracted to the other, it gives up its charge and becoming chargedwith similar electricity to that of the bell it touches, is repelled andattracted to the other, and this action is kept up as long as theexcitement continues, the bells ringing continuously. Fig. 84. ELECTRIC CHIMES. Chronograph, Electric. An apparatus for indicating electrically, and thereby measuring, thelapse of time. The periods measured may be exceedingly short, such asthe time a photographic shutter takes to close, the time required by aprojectile to go a certain distance, and similar periods. A drum rotated with even and known velocity may be marked by a styluspressed upon it by the action of an electro-magnet when a key istouched, or other disturbance. Then the space between two marks wouldgive the period elapsing between the two disturbances of the circuit. Asit is practically impossible to secure even rotation of a drum, it isnecessary to constantly measure its rate of rotation. This is effectedby causing a tuning-fork of known rate of vibration to be maintained invibration electrically. A fine point or bristle attached to one of itsarms, marks a sinuous line upon the smoked surface of the cylinder. Thisgives the basis for most accurately determining the smallest intervals. Each wave drawn by the fork corresponds to a known fraction of a second. For projectiles, the cutting of a wire opens a circuit, and the openingis recorded instead of the closing. By firing so as to cut two wires ata known distance apart the rate is obtained by the chronograph. Synonym--Chronoscope. 119 STANDARD ELECTRICAL DICTIONARY. Chutaux's Solution. A solution for bichromate batteries. It is composed as follows: Water, 1, 500 parts Potassium bichromate, 100 parts mercury bisulphate, 100 parts 66° sulphuric acid, 50 parts. Circle, Galvanic or Voltaic. A term for the voltaic circuit; obsolete. Fig. 85. MAGIC CIRCLE. Circle, Magic. A form of electro-magnet. It is a thick circle of round iron and is usedin connection with a magnetizing coil, as shown, to illustrateelectro-magnetic attraction. 120 STANDARD ELECTRICAL DICTIONARY. Circuit. A conducting path for electric currents properly forming a complete pathwith ends joined and including generally a generating device of somekind. Part of the conduction may be true and part electrolytic. (SeeElectrolytic Conduction. ) The term has become extended, so that the termis often applied to any portion of a circuit conveniently considered byitself. The simplest example of a complete circuit would be a circularconductor. If rotated in the earth's field so as to cut its lines offorce a current would go through it, and it would be an electriccircuit. Another example is a galvanic battery with its ends connectedby a wire. Here the battery generates the current which, by electrolyticconduction, goes through the battery and by true conduction through thewire. For an example of a portion of a circuit spoken of as "a circuit"see Circuit, Astatic. Circuit, Astatic. A circuit so wound with reference to the direction of the currentspassing through it that the terrestrial or other lines of force have nodirective effect upon it, one member counteracting the other. It may beproduced by making the wire lie in two closed curves, A and B, eachenclosing an equal area, one of identical shape and disposition with theother, and with the current circulating in opposite directions in eachone. Thus each circuit represents a magnetizing turn of oppositepolarity and counteracting each other's directive tendency exhibited ina field of force with reference to an axis a c. Another form of astaticcircuit is shown in Fig. 86. The portions C, D, lying on opposite sidesof the axis of rotation a c, are oppositely acted on by the earth'sdirective force as regards the direction of their rotation. Figs. 86 and 87. ASTATIC CIRCUITS. Circuit, Branch. A circuit dividing into two or more parts in parallel with each other. 121 STANDARD ELECTRICAL DICTIONARY. Circuit Breaker. Any apparatus for opening and closing a circuit is thus termed, but itis generally applied to automatic apparatus. A typical circuit breakeris the hammer and anvil of the induction coil. (See Induction Coil;Anvil. ) Again a pendulum connected to one terminal of a circuit mayswing so as to carry a point on its lower end through a globule ofmercury as it swings, which globule is connected to the other terminal. A great many arrangements of this character have been devised. Synonym. --Contact Breaker. Circuit Breaker, Automatic. A circuit breaker worked by the apparatus to which it is attached, orotherwise automatically. (See Induction Coil; Anvil; Bell, Electric. ) Circuit Breaker, File. A coarsely cut file, forms one terminal of an electric circuit, with astraight piece of copper or steel for the other terminal. The latterterminal drawn along the teeth makes and breaks the contact once forevery tooth. The movable piece should have an insulated handle. Circuit Breaker, Mercury. A circuit breaker which may be identical in principle, with theautomatic circuit breaker of an induction coil, but in which in place ofthe anvil, q. V. , a mercury cup is used, into which the end of a wiredips and emerges as it is actuated by the impulses of the current. Eachdip makes the contact, which is broken as the wire springs back. Themercury should be covered with alcohol to protect it from oxidation. Circuit Breaker, Pendulum. A circuit breaker in which a pendulum in its swing makes and breaks acontact. It may be kept in motion by clockwork, or by an electro-magnet, attracting intermittently an armature attached to its rod, themagnet circuit being opened and closed by the pendulum or circuitbreaker itself. A mercury contact may be used with it. Fig. 88. PENDULUM CIRCUIT BREAKER. 122 STANDARD ELECTRICAL DICTIONARY. Circuit Breaker, Tuning Fork. A circuit breaker in which a tuning fork makes and breaks the circuit. Each vibration of one of the prongs in one direction makes a contact, and the reverse vibration breaks a contact. The adjustment isnecessarily delicate, owing to the limited amplitude of the motion ofthe fork. The fork is kept in vibration sometimes by an electro-magnet, which is excited as the circuit is closed by the fork. One leg of thefork acts as the armature of the magnet, and is attracted according toits own natural period. Circuit Breaker, Wheel. A toothed wheel with a spring bearing against its teeth. One terminal ofa circuit connects with the wheel through its axle, the other connectswith the spring. When the wheel is turned the circuit is opened andclosed once for each tooth. The interstices between teeth on such awheel may be filled with insulating material, giving a cylindricalsurface for the contact spring to rub on. Fig. 89--TOOTHED WHEEL CIRCUIT BREAKER. Circuit, Closed. A circuit whose electric continuity is complete; to make an open circuitcomplete by closing a switch or otherwise is to close, complete, or makea circuit. Synonyms--Completed Circuit--Made Circuit. Circuit, Compound. A circuit characterized by compounding of generating or receivingdevices, as including several separate batteries, or several motors, orother receiving devices. It is sometimes used to indicate a circuithaving its battery arranged in series. It should be restricted to thefirst definition. 123 STANDARD ELECTRICAL DICTIONARY. Circuit, Derived. A partial circuit connected to two points of another circuit, so as tobe in parallel with the portion thereof between such two points; a shuntcircuit. Synonyms--Shunt Circuit--Derivative Circuit--Parallel Circuit. Circuit, Electric, Active. A circuit through which a current passes. The circuit itself need onlybe a conducting ring, or endless wire. Generally it includes, as part ofthe circuit, a generator of electro-motive force, and through whichgenerator by conduction, ordinary or electrolytic, the same current goesthat passes through the rest of the circuit. One and the same currentpasses through all parts of a series circuit when such current isconstant. A current being produced by electro-motive force, and electromotiveforce disappearing in its production in an active circuit, there must besome source of energy which will maintain electromotive force againstthe drain made upon it by the current. The simplest conception of an active electric circuit is a ring orendless conductor swept through a field of force so as to cut lines offorce. A simple ring dropped over a magnet pole represents thesimplification of this process. In such a ring a current, exceedinglyslight, of course, will be produced. In this case there is no generatorin the circuit. An earth coil (see Coil, Earth, ) represents such acircuit, with the addition, when experimented with, of a galvanometer inthe circuit. In practice, a circuit includes a generator such as a battery or dynamo, and by conductors is led through a continuous path. Electric lamps, electrolytic cells, motors and the like may be included in it. The term "circuit" is also applied to portions of a true circuit, as theinternal circuit, or external circuit. A certain amount of elasticity isallowed in its use. It by no means necessarily indicates a completethrough circuit. Circuit, Electrostatic. (a) A circuit through which an electrostatic or high tension dischargetakes place. It is virtually an electric circuit. (b) The term is applied also to the closed paths of electrostatic linesof force. Circuit, External. The portion of a circuit not included within the generator. Circuit, Grounded. A circuit, one of whose members, the return circuit, is represented bythe earth, so that the earth completes the circuit. In telegraphy eachend of the line is grounded or connected to an earth-plate, q. V. , or tothe water or gas-pipes, and the current is assumed to go through theearth on its return. It really amounts to a discharging at one end, andcharging at the other end of the line. The resistance of the earth iszero, but the resistance of the grounding or connection with the earthmay be considerable. Synonyms--Ground Circuit--Earth Circuit--Single Wire Circuit. [Transcriber's note: The resistance of the earth is high enough thatlarge power system return currents may produce dangerous voltagegradients when a power line is shorted to the ground. Don't walk neardowned lines!] 124 STANDARD ELECTRICAL DICTIONARY. Circuit Indicator. A pocket compass, decomposition apparatus, galvanometer or other devicefor indicating the condition of a wire, whether carrying a current ornot, and, if carrying one, its direction, and sometimes roughlyindicating its strength. Circuit, Internal. The portion of an electric circuit included within the generator. Circuit, Line. The portion of a circuit embracing the main line or conductor, as in atelegraph circuit the line carried on the poles; distinguished from thelocal circuit (see Circuit, Local, ) in telegraphy. Circuit, Local. In telegraphy, a short circuit with local generator or battery included, contained within the limits of the office or station and operated by arelay, q. V. This was the original local circuit; the term is applicableto any similar arrangement in other systems. Referring to the cut, themain line circuit includes the main battery, E, Key, P, Relay, R, groundplates, G, G1. The relay magnet opens and closes the local circuit withits local battery, L, and sounder magnet, H, with its armature, B. Theminor parts, such as switches, are omitted. Fig. 90. LOCAL CIRCUIT OF TELEGRAPH SYSTEM. Circuit, Local Battery. A local circuit worked by and including a local battery in its course. 125 STANDARD ELECTRICAL DICTIONARY. Circuit, Loop. A minor circuit introduced in series into another circuit by a cut-out, or other device, so as to become a portion of the main circuit. Circuit Loop Break. A supporter or bracket with two arms for carrying insulators. Its use isto enable a loop connection to be introduced into a line which is cut, so as to enable the connection of the ends of the loop to be made, oneto each end of the through wire, which ends are attached, one to each ofthe two insulators. Circuit, Main. The circuit including the main line and apparatus supplied by the mainbattery, as distinguished from the local circuit. (See Circuit, Local. ) Circuit, Main Battery. The main circuit, including the main or principal battery in its course. Circuit, Metallic. A circuit in which the current outside the generator, or similar parts, is carried on a metallic conductor; a circuit without any groundcircuit. The including of a galvanic battery or electro plating bathwould not prevent the application of the term; its essential meaning isthe omission of the earth as the return circuit. Circuit, Negative Side of. The side of a circuit opposite to the positive side. (See Circuit, Positive Side of) It is defined as the half of a circuit leading to thepositive terminal of the generator. Circuit, Open. A circuit with its continuity broken, as by disconnecting a wire fromthe battery, or opening a switch; a broken circuit is its synonym. Toopen a switch or disconnect or cut the wire is termed opening orbreaking the circuit. Synonyms--Incomplete Circuit--Broken Circuit. Circuit, Positive Side of. This side is such that an observer standing girdled by the current withhis head in the positive side or region, would see the current passaround him from his right toward his left hand. It is also defined asthe half of the circuit leading to the negative terminal of thegenerator. Circuit, Recoil. The portion of a parallel circuit presenting an alternative path, q. V. , for a disruptive discharge. Circuit, Return. (a) The part of a circuit extending from the generator to the extremepoint in general, upon which no apparatus is placed. In telegraphsystems the ground generally forms the return circuit. The distinctionof return and working circuit cannot always be made. (b) It may also be defined as the portion of a circuit leading to thenegative terminal of the generator. 126 STANDARD ELECTRICAL DICTIONARY Circuits, Forked. Circuits starting in different paths or directions from one and the samepoint. Circuit, Simple. A circuit containing a single generator, and single receiver of anykind, such as a motor or sounder, with a single connecting conductor. Itis also used to indicate arrangement in multiple arc, but not generally, or with approval. Circuits, Parallel. Two or more conductors starting from a common point and ending atanother common point are termed, parallel circuits, although really butparts of circuits. If of equal resistance their joint resistance isobtained by dividing the resistance of one by the number of parallelcircuits. If of unequal resistance r, r', r", etc. , the formula forjoint resistance, R, of two is R = ( r * r' ) / ( r + r' ) This resistance may then be combined with a third one by the sameformula, and thus any number may be calculated. Synonym--Shunt Circuit. Circuit, Voltaic. Properly a circuit including a conductor and voltaic couple. It is also applied to the electric circuit, q. V. , or to any circuitconsidered as a bearer of current electricity. Circular Units. Units of area, usually applied to cross sectional area of conductors, bywhose use area is expressed in terms of circle of unit diameter, usually a circular mil, which is the area of a circle of one-thousandthof an inch diameter, or a circular millimeter, which is the area of acircle of one millimeter diameter. Thus a wire one-quarter of an inchin diameter has an area of 250 circular mils; a bar one centimeter indiameter has an area of ten circular millimeters. [Transcriber's Note: Area is the diameter squared. A 1/4 inch wire has62500 circular mils of area. A one centimeter (10 millimeter) wire has100 circular millimeters of area. Actual area = circular mils * (PI/4). ] Circumflux. The product of the total number of conductor turns on the armature of adynamo or motor, into the current carried thereby. For two pole machinesit is equal to twice the armature ampere-turns; for four pole machinesto four times such quantity, and so on. Clamp. The appliance for grasping and retaining the end of the rod that holds acarbon in the arc lamp. Clark's Compound. A cement used for the outside of the sheath of telegraph cables. Its formula is: Mineral Pitch, 65 parts. Silica, 30 parts. Tar, 5 parts. All parts by weight. 127 STANDARD ELECTRICAL DICTIONARY. Cleats. A support; a short block of wood, grooved transversely, for holdingelectric wires against a wall. For the three wire system three groovesare used. The entire wiring of apartments is sometimes done by the"cleat system, " using cleats instead of battens, q. V. , or mouldings. The cleats are secured against the wall with the grooves facing it, andthe wires are introduced therein. Fig. 91. TWO WIRE CLEAT. Fig. 92. THREE WIRE CLEAT. Cleat, Crossing. A cleat with grooves or apertures to support wires which cross eachother. Two or three grooves are transverse, and on the under side, asabove; one groove is longitudinal and on the upper side. Cleavage, Electrification by. If a mass of mica is rapidly split in the dark a slight flash isperceived. Becquerel found that in such separation the two pieces cameaway oppositely charged with electricity. The splitting of mica is itscleavage. Clock, Controlled. In a system of electric clocks, the clocks whose movements arecontrolled by the current, regulated by the master or controlling clock. Synonym--Secondary Clock. Clock, Controlling. In a system of electric clocks the master clock which controls themovements of the others, by regulating the current. Synonym--Master Clock. Clock, Electric Annunciator. A clock operating any form of electric annunciator, as droppingshutters, ringing bells, and the like. It operates by the machineryclosing circuits as required at any desired hour or intervals. 128 STANDARD ELECTRICAL DICTIONARY. Clock, Electrolytic. A clock worked by the electrolytic deposition and resolution of adeposit of metal upon a disc. It is the invention of Nikola Tesla. Ametallic disc is mounted on a transverse axis, so as to readily rotate. It is immersed in a vessel of copper sulphate. A current is passedthrough the bath, the terminals or electrodes being near to and facingthe opposite edges of the disc, so that the line connecting theelectrodes lies in the plane of the disc. If a current is passed throughthe solution by the electrodes, copper is deposited on one side of thedisc, and as it rotates under the influence of the weight thusaccumulated on one side, the same metal as it is brought to the otherside of the disc is redissolved. Thus a continuous rotation ismaintained. The cause of the deposition and solution is the position ofthe disc; one-half becomes negative and the other positive in theirmutual relations. Clock, Self-winding Electric. A clock which is wound periodically by an electric motor and battery. Clockwork, Feed. In arc-lamps the system of feeding the carbon or carbons by clockworkwhose movements are controlled by the resistance of the arc. This systemis employed in the Serrin, and in the Gramme regulators, among others. The carbons, if they approach, move clockwork. The movement of this isstopped or freed by an electro-magnet placed in shunt around the arcand carbons. Cloisons. Partitions or divisions; applied to the winding of electro-magnets andcoils where the winding is put on to the full depth, over singlesections of the core, one section at a time, until the whole core isfilled up. Closure. The closing or completion of a circuit by depressing a key or moving aswitch. Clutch. In arc lamps a device for the feed of the upper carbons. In its simplestform it is simply a plate or bar pierced with a hole through which thecarbon passes loosely. The action of the mechanism raises or lowers oneend of the plate or bar. As it rises it binds and clutches the carbon, and if the action continues it lifts it a little. When the same end islowered the carbon and clutch descend together until the opposite end ofthe clutch being prevented from further descent, the clutch approachesthe horizontal position and the rod drops bodily through the aperture. The cut shows the clutches of the Brush double carbon lamp. In practicethe lifting and releasing as regulated by an electro-magnet are so veryslight that practically an almost absolutely steady feed is secured. Asimilar clutch is used in the Weston lamp. 129 STANDARD ELECTRICAL DICTIONARY. Clutch, Electro-magnetic. A clutch or appliance for connecting a shaft to a source of rotarymotion while the latter is in action. In one form a disc, in whose facea groove has been formed, which groove is filled with a coil of wire, isattached to the loose wheel, while the shaft carries a flat plate to actas armature. On turning on the current the flat plate is attached, adheres, and causes its wheel to partake of the motion of the shaft. Contact is made by brushes and collecting rings. In the cut, A A is the attracted disc; the brushes, B B, take current tothe collecting rings, C. The magnetizing coil is embedded in the body ofthe pulley, as shown. Fig. 93. CLUTCH OF BRUSH LAMP. Fig. 94. ELECTRO-MAGNETIC CLUTCH. 130 STANDARD ELECTRICAL DICTIONARY. Coatings of a Condenser or Prime Conductor. The thin conducting coatings of tinfoil, gold leaf or other conductingsubstance, enabling the surface to receive and part with the electriccharge readily. Without such a coating the charge and discharge would bevery slow, and would operate by degrees only, as one part of anon-conducting surface might be densely charged and another part bequite devoid of sensible charge. Code, Cipher. A code of arbitrary words to designate prearranged or predeterminedwords, figures or sentences. The systems used in commerce have singlewords to represent whole sentences or a number of words of a sentence. This not only imparts a degree of secrecy, but makes the messages muchshorter. Codes are used a great deal in cable transmission. Code, Telegraphic. A telegraphic alphabet. (See Alphabets, Telegraphic. ) Coefficient. In algebra, the numerical multiplier of a symbol, as in the expression"5x, " 5 is the coefficient. In physics, generally a number expressingthe ratio or relation between quantities, one of which is often unity, as a standard or base of the set of coefficients. Thus the coefficientof expansion by heat of any substance is obtained by dividing its volumefor a given degree of temperature by its volume at the standardtemperature as 0º C. , or 32º F. This gives a fraction by which if anyvolume of a substance, taken at 0º C. , or at whatever may be taken asthe basic temperature, is multiplied, the expanded volume for the givenchange of temperature will be obtained as the product. A coefficientalways in some form implies the idea of a multiplier. Thus thecoefficient of an inch referred to a foot would be 1/12 or . 833+, because any number of inches multiplied by that fraction would give thecorresponding number of feet. [Transcriber's note: 1/12 is 0. 0833+] Coefficient, Economic. In machinery, electric generators, prime motors and similar structures, the number expressing the ratio between energy absorbed by the device, and useful, not necessarily available, work obtained from it. It isequal to work obtained divided by energy absorbed, and is necessarily afraction. If it exceeded unity the doctrine of the conservation ofenergy would not be true. The economic coefficient expresses theefficiency, q. V. , of any machine, and of efficiencies there are severalkinds, to express any one of which the economic coefficient may be used. Thus, let W--energy absorbed, and w = work produced ; then w/W is theeconomic coefficient, and for each case would be expressed numerically. (See Efficiency, Commercial--Efficiency, Electrical--Efficiency ofConversion. ) The distinction between useful and available work in a dynamo is asfollows: The useful work would include the work expended by the field, and the work taken from the armature by the belt or other mechanicalconnection. Only the latter would be the available work. 131 STANDARD ELECTRICAL DICTIONARY. Coercive or Coercitive Force. The property of steel or hard iron, in virtue of which it slowly takesup or parts with magnetic force, is thus termed ("traditionally";Daniell). It seems to have to do with the positions of the molecules, asjarring a bar of steel facilitates its magnetization or accelerates itsparting, when not in a magnetic field, with its permanent or residualmagnetism. For this reason a permanent magnet should never be jarred, and permitting the armature to be suddenly attracted and to strikeagainst it with a jar injures its attracting power. Coercive force is defined also as the amount of negative magnetizingforce required to reduce remnant magnetism to zero. By some authorities the term is entirely rejected, as the phenomenondoes not seem directly a manifestation of force. Coil and Coil Plunger. A device resembling the coil and plunge, q. V. , except that for theplunger of iron there is substituted a coil of wire of such diameter asto enter the axial aperture of the other, and wound or excited in thesame or in the opposite sense, according to whether attraction orrepulsion is desired. Coil and Plunger. A coil provided with a core which is free to enter or leave the centralaperture. When the coil is excited, the core is drawn into it. Variousforms of this device have been used in arc lamp regulators. Synonym--Sucking coil. Fig. 95. COIL AND COIL PLUNGER OF MENGIES ARC LAMP. Fig. 96. COIL AND PLUNGER EXPERIMENT. 132 STANDARD ELECTRICAL DICTIONARY. Coil and Plunger, Differential. An arrangement of coil and plunger in which two plungers or one plungerare acted on by two coils, wound so as to act oppositely ordifferentially on the plunger or plungers. Thus one coil may be inparallel with the other, and the action on the plunger will then dependon the relative currents passing through the coils. Coil, Choking. A coil of high self-induction, used to resist the intensity of or"choke" alternating currents. Any coil of insulated wire wound aroundupon a laminated or divided iron core forms a choking coil. The ironcoil is usually so shaped as to afford a closed magnetic circuit. A converter or transformer acts as a choking coil as long as itssecondary is left open. In alternating current work special chokingcoils are used. Thus for theatrical work, a choking coil with a movableiron core is used to change the intensity of the lights. It is incircuit with the lamp leads. By thrusting in the core the self-inductionis increased and the current diminishes, lowering the lamps; bywithdrawing it the self-induction diminishes, and the current increases. Thus the lamps can be made to gradually vary in illuminating power likegas lights, when turned up or down. Synonyms--Kicking Coil--Reaction Coil. Fig. 97. DIFFERENTIAL COILS AND PLUNGERS. Fig. 98. BISECTED COILS. 133 STANDARD ELECTRICAL DICTIONARY. Coils, Bisected. Resistance coils with connections at their centers, as shown in thediagram. They are used for comparing the resistances of two conductors. The connections are arranged as shown in the coil, each coil beingbisected. For the wires, movable knife-edge contacts are employed. Theprinciple of the Wheatstone bridge is used in the method andcalculations. Coil, Earth. A coil of wire mounted with commutator to be rotated so as to cut thelines of force of the earth's magnetic field, thereby generatingpotential difference. The axis of rotation may be horizontal, when thepotential will be due to the vertical component of the earth's field, orthe axis may be horizontal, when the potential will be due to thevertical component, or it may be set at an intermediate angle. Synonym--Delezenne's Circle. Fig. 99. DELEZENNE'S CIRCLE OR EARTH COIL. Coil, Electric. A coil of wire used to establish a magnetic field by passing a currentthrough it. The wire is either insulated, or so spaced that itsconvolutions do not touch. Coil, Flat. A coil whose windings all lie in one plane, making a sort of disc, or anincomplete or perforated disc. Coil, Induction. A coil in which by mutual induction the electromotive force of a portionof a circuit is made to produce higher or lower electro-motive force, inan adjoining circuit, or in a circuit, part of which adjoins theoriginal circuit, or adjoins part of it. An induction coil comprises three principal parts, the core, the primarycoil and the secondary coil. If it is to be operated by a steadycurrent, means must be provided for varying it or opening and closingthe primary circuit. A typical coil will be described. 134 STANDARD ELECTRICAL DICTIONARY. The core is a mass of soft iron preferably divided to prevent extensiveFoucault currents. A cylindrical bundle of soft iron wires is generallyused. Upon this the primary coil of reasonably heavy wire, and of one ortwo layers in depth, is wrapped, all being carefully insulated withshellac and paper where necessary. The secondary coil is wrapped upon orover the primary. It consists of very fine wire; No. 30 to 36 is aboutthe ordinary range. A great many turns of this are made. In generalterms the electro-motive force developed by the secondary stands to thatof the primary terminals in the ratio of the windings. This is onlyapproximate. The greatest care is required in the insulating. The secondary issometimes wound in sections so as to keep those parts differing greatlyin potential far from each other. This prevents sparking, which woulddestroy the insulation. A make and break, often of the hammer and anvil type, is operated by thecoil. (See Circuit Breaker, Automatic. ) As the current passes throughthe primary it magnetizes the core. This attracts a little hammer whichnormally resting on an anvil completes the circuit. The hammer asattracted is lifted from the anvil and breaks the circuit. The soft ironcore at once parts with its magnetism and the hammer falls upon theanvil again completing the circuit. This operation goes on rapidly, thecircuit being opened and closed in quick succession. Every closing of the primary circuit tends to produce a reverse currentin the secondary, and every opening of the primary circuit tends toproduce a direct current in the secondary. Both are of extremely shortduration, and the potential difference of the two terminals of thesecondary may be very high if there are many times more turns in thesecondary than in the primary. The extra currents interfere with the action of an induction coil. Toavoid their interference a condenser is used. This consists of twoseries of sheets of tin foil. Leaves of paper alternate with the sheetsof tin-foil, the whole being built up into a little book. Each sheet oftin-foil connects electrically with the sheet next but one to it. Thuseach leaf of a set is in connection with all others of the same set, butis insulated from the others. One set of leaves of tin-foil connectswith the hammer, the other with the anvil. In large coils there may be75 square feet of tin-foil in the condenser. The action of the condenser is to dispose of the direct extra current. When the primary circuit is opened this current passes into thecondenser, which at once discharges itself in the other directionthrough the coil. This demagnetizes the core, and the action intensifiesand shortens the induced current. The condenser prevents sparking, andin general improves the action of the coil. Many details enter into the construction of coils, and many variationsin their construction obtain. Thus a mercury cup into which a plungerdips often replaces the anvil and hammer. 135 STANDARD ELECTRICAL DICTIONARY. The induction coil produces a rapid succession of sparks, which mayspring across an interval of forty inches. The secondary generally endsin special terminals or electrodes between which the sparking takesplace. A plate of glass, two inches in thickness, can be pierced bythem. In the great Spottiswoode coil there are 280 miles of wire in thesecondary, and the wire is about No. 36 A. W. G. Fig. 100. VERTICAL SECTION OF INDUCTION COIL. Fig. L01. PLAN OF INDUCTION COIL CONNECTIONS. Induction coils have quite extended use in electrical work. They areused in telephone transmitters, their primary being in circuit with themicrophone, and their secondary with the line and receiving telephone. In electric welding, and in the alternating current system they haveextended application. In all these cases they have no automatic circuitbreaker, the actuating current being of intermittent or alternatingtype. 136 STANDARD ELECTRICAL DICTIONARY. In the cuts the general construction of an induction coil is shown. Inthe sectional elevation, Fig. 100, A, is the iron core; B is the primaryof coarse wire; C is a separating tube, which may be of pasteboard; D isthe secondary of fine wire; E, E are the binding posts connected to thesecondary; H, H are the heads or standards; K, K are the terminals ofthe primary; F is the vibrating contact spring; G, a standard carryingthe contact screw; J is the condenser with wires, L, M, leading to it. Referring to the plan, Fig. 101, H represents the primary coil; B and Aare two of the separate sheets of the condenser, each sheet withprojecting ears; G, G are the heads of the coil; the dark lines areconnections to the condenser. One set of sheets connects with theprimary coil at C, and also with the vibrating spring shown in plan andin the elevation at F. The other set of sheets connects with the post, carrying the contact screw. The other terminal of the primary runs to abinding post E. F, in the plan is a binding post in connection with thestandard and contact screw. Coil, Induction, Inverted. An induction coil arranged to have a lower electro-motive force in thesecondary than in the primary. This is effected by having moreconvolutions in the primary wire than in the secondary. Such coils inpractice are used with the alternating current and then do not include acircuit breaker or condenser. They are employed in alternating currentsystem and in electric welding. (See Welding, Electric--Converter. ) In the cut an inverted coil, as constructed for electric welding isshown. In it the primary coil is marked P; the secondary, merely a barof metal, is marked E, with terminals S, S; the heavy coils, I, of ironwire are the core; K is a screw for regulating the clamps; J, Z is asecond one for the same purpose, while between D and D' the heat isproduced for welding the bars, B, B', held in the clamps, C, C'. It willbe seen how great may be the difference in turns between the singlecircle of heavy copper rod or bar which is the secondary of the coil, and the long coil of wire forming the primary. Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING. 137 STANDARD ELECTRICAL DICTIONARY. Coil, Induction, Telephone. An induction coil used in telephone circuits. It is placed in the box orcase near the transmitter. The primary is in circuit with themicrophone. The secondary is in circuit with the line and receivingtelephone. In the Bell telephone apparatus the primary of the inductioncoil is wound with No. 18 to 24 A. W. G. Wire to a resistance of 1/2ohm; the secondary, with No. 36 wire to a resistance of 80 ohms. TheEdison telephone induction coil was wound with similar wires to aresistance of 3 to 4 ohms and of 250 ohms respectively. Coil, Magnetizing. A coil of insulated wire for making magnets; and for experimental uses;it has a short axis and central aperture of as small size as consistentwith the diameter of the bar to be magnetized, which has to pass throughit readily. The wire may be quite heavy, 2 or 3 millimeters (. 08--. 12inch) thick, and is cemented together with carpenter's glue, or withshellac or ethereal solution of gum copal. In use it is passed over thebar a few times while a heavy current is going through it. It is usedfor magic circles also. (See Circle, Magic. ) Fig. 103. MAGNETIZING COIL. Coil, Resistance. A coil constructed for the purpose of offering a certain resistance to asteady current. This resistance may be for the purpose of carrying outquantitative tests, as in Wheatstone bridge work (see Wheatstone'sBridge), or simply to reduce the intensity of a current. For the firstclass of work the coils are wound so as to prevent the creation of amagnetic field. This is effected by first doubling the wire withoutbreaking it, and then starting at the bend the doubled wire, which isinsulated, is wound on a bobbin or otherwise until a proper resistanceis shown by actual measurement. The coils are generally contained or setin closed boxes with ebonite tops. Blocks of brass are placed on thetop, and one end from one coil and one end from the next connect withthe same block. By inserting a plug, P, so as to connect any two blocks, which have grooves reamed out for the purpose, the coil beneath will beshort circuited. German silver, platinoid or other alloy, q. V. , isgenerally the material of the wire. A great object is to have a wirewhose resistance will be unaffected by heat. 138 STANDARD ELECTRICAL DICTIONARY. Fig. 104. RESISTANCE COILS AND CONNECTIONS, SHOWING PLUG. Coil, Rhumkorff. The ordinary induction coil with circuit breaker, for use with originaldirect and constant current, is thus termed. (See Coil, Induction. ) Synonym--Inductorium. Coil, Ribbon. A coil made of copper ribbon wound flatwise, often into a disc-likeshape, and insulated by tape or strips of other material interveningbetween the successive turns. Coils, Compensating. Extra coils on the field magnets of dynamos or motors, which coils arein series with the armature windings for the purpose of keeping thevoltage constant. In compound wound machines the regular series-woundcoil is thus termed. In a separately excited dynamo a coil of the samekind in circuit with the armature may be used as a compensator. Coils, Henry's. An apparatus used in repeating a classic experiment in electro-magneticinduction, due to Prof. Henry. It consists in a number of coils, thefirst and last ones single, the intermediate ones connected in pairs, and one of one pair placed on the top of one of the next pair. Onopening or closing the circuit of an end coil the induced effect goesthrough the series and is felt in the circuit of the other end coil. Prof. Henry extended the series so as to include seven successiveinductions, sometimes called inductions of the first, second, third andother orders. Frequently ribbon coils (see Coil, Ribbon, ) are used inthese experiments. Coils, Sectioned. A device for prolonging the range of magnetic attraction. It consists ofa series of magnetizing coils traversed by an iron plunger. As it passesthrough them, the current is turned off the one in the rear or passingto the rear and turned into the next one in advance. The principle wasutilized in one of Page's electric motors about 1850, and later byothers. The port-electric railroad, q. V. , utilizes the same principle. 139 STANDARD ELECTRICAL DICTIONARY. Collecting Ring. In some kinds of generators instead of the commutator a pair ofcollecting rings of metal, insulated from the machine and from eachother, are carried on the armature shaft. A brush, q. V. , presses oneach, and the circuit terminals connect to these two brushes. Such ringsare employed often on alternating current generators, where the currentdoes not have to be changed or commuted. Collecting rings with theirbrushes are used also where a current has to be communicated to arevolving coil or circuit as in the magnetic car wheel, the cut of whichis repeated here. The coil of wire surrounding the wheel and rotatingwith it has to receive current. This it receives through the twostationary brushes which press upon two insulated metallic rings, surrounding the shaft. The terminals of the coil connect one to eachring. Thus while the coil rotates it constantly receives current, thebrushes being connected to the actuating circuit. Fig. 105. MAGNETIC CAR WHEEL SHOWING COLLECTING RINGS AND BRUSHES. Collector. (a) A name for the brush, q. V. , in mechanical electric generators, suchas dynamos, a pair of which collectors or brushes press on thecommutator or collecting rings, and take off the current. (b) The pointed connections leading to the prime conductor on a staticmachine for collecting the electricity; often called combs. The pointsof the combs or collectors face the statically charged rotating glassplate or cylinder of the machine. Colombin. The insulating material between the carbons in a Jablochkoff candle orother candle of that type. Kaolin was originally used. Later a mixtureof two parts calcium sulphate (plaster of Paris) and one part bariumsulphate (barytes) was substituted. The colombin was three millimeters (. 12 inch) wide, and two millimeters(. 08 inch) thick. (See Candle, Jablochkoff. ) Column, Electric. An old name for the voltaic pile, made up of a pile of discs of copperand zinc, with flannel discs, wet with salt solution or dilute acid, between each pair of plates. 140 STANDARD ELECTRICAL DICTIONARY. Comb. A bar from which a number of teeth project, like the teeth of a comb. Itis used as a collector of electricity from the plate of a frictional orinfluence electric machine; it is also used in a lightning arrester todefine a path of very high resistance but of low self-induction, for thelightning to follow to earth. Communicator. The instrument by which telegraph signals are transmitted is sometimesthus termed. Commutator. In general an apparatus for changing. It is used on electric currentgenerators, and motors, and on induction coils, and elsewhere, forchanging the direction of currents, and is of a great variety of types. Synonym--Commuter (but little used). Fig. 106. DYNAMO OR MOTOR COMMUTATOR. Commutator Bars. The metallic segments of a dynamo or motor commutator. Commutator, Flats in. A wearing away or lowering in level of one or more metallic segments ofa commutator. They are probably due in many cases to sparking, set up byperiodic springing in the armature mounting, or by defective commutatorconnections. Commutator of Current Generators and Motors. In general a cylinder, formed of alternate sections of conducting andnon-conducting material, running longitudinally or parallel with theaxis. Its place is on the shaft of the machine, so that it rotatestherewith. Two brushes, q. V. , or pieces of conducting material, pressupon its surface. 141 STANDARD ELECTRICAL DICTIONARY. As a part of electric motors and generators, its function is to collectthe currents produced by the cutting of lines of force so as to causethem all to concur to a desired result. The cut shows the simplest formof commutator, one with but two divisions. Its object may be to enable acurrent of constant direction to be taken from a rotating armature, inwhich the currents alternate or change direction once in each rotation. It is carried by the shaft A of the armature and rotates with it. Itconsists of two leaves, S S, to which the terminals of the armature areconnected. Two springs, W W, the terminals of the outer circuit, pressagainst the leaves. The springs which do this take off the current. Itis so placed, with reference to the springs and armature, that just asthe current changes in direction, each leaf changes from one spring tothe other. Thus the springs receive constant direction currents. Thechanging action of this commutator appears in its changing the characterof the current from alternating to constant. Were two insulatedcollecting rings used instead of a commutator, the current in the outercircuit would be an alternating one. On some dynamos the commutator hasa very large number of leaves. Taking the Gramme ring armature, there must be as many divisions of thecommutator as there are connections to the coils. In this case thefunction of the commutator is simply to lessen friction, for the brushescould be made to take current from the coils directly outside of theperiphery of the ring. Commutator, Split Ring. A two-division commutator for a motor; it consists of two segments ofbrass or copper plate, bent to arcs of a circle, and attached to aninsulating cylinder. They are mounted on the revolving spindle, whichcarries the armature, and acts as a two part commutator. For an exampleof its application, see Armature, Revolving, Page's. (See also Fig. 107. ) Fig. 107. SECTION OF SPLIT RING COMMUTATOR, WITH BRUSHES. Compass. An apparatus for utilizing the directive force of the earth upon themagnetic needle. It consists of a circular case, within which is poiseda magnetized bar of steel. This points approximately to the north, andis used on ships and elsewhere to constantly show the direction of themagnetic meridian. Two general types are used. In one the needle ismounted above a fixed "card" or dial, on which degrees or points of thecompass, q. V. , are inscribed. In the other the card is attached to theneedle and rotates with it. The latter represents especially the typeknown as the mariner's compass. (See Compass, Mariner's--Compass, Spirit, and other titles under compass, also Magnetic Axis--MagneticElements. ) The needle in good compasses carries for a bearing at itscentre, a little agate cup, and a sharp brass pin is the point ofsupport. Compass, Azimuth. A compass with sights on one of its diameters; used in determining themagnetic bearing of objects. 142 STANDARD ELECTRICAL DICTIONARY. Compass Card. The card in a compass; it is circular in shape, and its centre coincideswith the axis of rotation of the magnetic needle; on it are marked thepoints of the compass, at the ends generally of star points. (SeeCompass, Points of the. ) It may be fixed, and the needle may be poisedabove it, or it may be attached to the needle and rotate with it. Compass, Declination. An instrument by which the magnetic declination of any place may bedetermined. It is virtually a transit instrument and compass combined, the telescope surmounting the latter. In the instrument shown in thecut, L is a telescope mounted by its axis, X, in raised journals withvernier, K, and arc x, for reading its vertical angle, with level n. Theazimuth circle, Q, R, is fixed. A vernier, V is carried by the box, A, E, and both turn with the telescope. A very light lozenge-shapedmagnetic needle, a, b, is pivoted in the exact centre of the graduatedcircles, Q R, and M. The true meridian is determined by any convenientastronomical method, and the telescope is used for the purpose. Thevariation of the needle from the meridian thus determined gives themagnetic declination. FIG. 108. DECLINATION COMPASS. Compass, Inclination. A magnetic needle mounted on a horizontal axis at its centre of gravity, so as to be free to assume the dip, or magnetic inclination, when placedin the magnetic meridian. It moves over the face of a vertical graduatedcircle, and the frame also carries a spirit level and graduatedhorizontal circle. In use the frame is turned until the needle isvertical. Then the axis of suspension of the needle is in the magneticmeridian. The vertical circle is then turned through 90° of the horizon, which brings the plane of rotation of the needle into the magneticmeridian, when it assumes the inclination of the place. 143 STANDARD ELECTRICAL DICTIONARY. Compass, Mariner's. A compass distinguished by the card being attached to and rotating withthe needle. A mark, the "lubber's mark" of the sailors is made upon thecase. This is placed so that the line connecting it, and the axis ofrotation of the card is exactly in a plane, passing through the keel ofthe ship. Thus however the ship may be going, the point of the cardunder or in line with the "lubber's mark, " shows how the ship ispointing. The case of the mariner's compass is often bowl-shaped andmounted in gimbals, a species of universal joint, so as to bc alwayshorizontal. (See Compass, Spirit-Gimbals. ) FIG. 109. MARINER'S COMPASS. Compass, Points of the. The circle of the horizon may bc and is best referred to angulardegrees. It has also been divided into thirty-two equiangular and namedpoints. A point is 11. 25°. The names of the points are as follows:North, North by East, North North-east, North-east by North, North-east, North-east by East, East North-east, East by North, East, East by South, East South-east, South-east by East, South-east, South-east by South, South South-east, South by East, South, South by West, South South-west, South-west by South, South-west, South-west by West, West South-west, West by South, West, West by North, West North-west, North-west by West, North-west, North West by North, North North-west, North by West. Theyare indicated by their initials as N. N. W. , North North-west, N. By W. , North by West. Compass, Spirit. A form of mariner's compass. The bowl or case is hermetically sealed andfilled with alcohol or other nonfreezing liquid. The compass card ismade with hollow compartments so as nearly to float. In this way thefriction of the pivot or point of support is greatly diminished, and thecompass is far more sensitive. Compass, Surveyor's. A species of theodolite; a telescope with collimation lines, mountedabove a compass, so as to be applicable for magnetic surveys. Its use isto be discouraged on account of the inaccuracy and changes indeclination of the magnetic needle. 144 STANDARD ELECTRICAL DICTIONARY. Compensating Resistances. In using a galvanometer shunt the total resistance of the circuit isdiminished so that in some cases too much current flows through it; insuch case additional resistance, termed as above, is sometimesintroduced in series. The shunt in parallel with the galvanometer isthus compensated for, and the experimental or trial circuit does nottake too much current. Complementary Distribution. Every distribution of electricity has somewhere a correspondingdistribution, exactly equal to it of opposite electricity; the latter isthe complimentary distribution to the first, and the first distributionis also complimentary to it. Component. A force may always be represented diagrammatically by a straight line, terminating in an arrow-head to indicate the direction, and of length torepresent the intensity of the force. The line may always be assumed torepresent the diagonal of a parallelogram, two of whose sides arerepresented by lines starting from the base of the arrow, and of lengthfixed by the condition that the original force shall be the diagonal ofthe parallelogram of which they are two contiguous sides; such lines arecalled components, and actually represent forces into which the originalforce may always be resolved. The components can have any direction. Thus the vertical component of a horizontal force is zero; itshorizontal component is equal to itself. Its 450 component is equal tothe square root of one-half of its square. Condenser. An appliance for storing up electrostatic charges: it is also called astatic accumulator. The telegraphic condenser consists of a box packedfull of sheets of tinfoil. Between every two sheets is a sheet ofparaffined paper, or of mica. The alternate sheets of tinfoil areconnected together, and each set has its own binding post. (SeeAccumulator, Electrostatic. ) Condenser, Sliding. An apparatus representing a Leyden jar whose coatings can be slid pasteach other. This diminishes or increases the facing area, andconsequently in almost exactly similar ratio diminishes or increases thecapacity of the condenser. Conductance. The conducting power of a given mass of specified material of specifiedshape and connections. Conductance varies in cylindrical or prismaticconductors, inversely as the length, directly as the cross-section, andwith the conductivity of the material. Conductance is an attribute ofany specified conductor, and refers to its shape, length and otherfactors. Conductivity is an attribute of any specified material withoutdirect reference to its shape, or other factors. Conduction. The process or act of conducting a current. 145 STANDARD ELECTRICAL DICTIONARY. Conductivity. The relative power of conducting the electric current possessed bydifferent substances. A path for the current through the ether is openedby the presence of a body of proper quality, and this quality, probablycorrelated to opacity, is termed conductivity. There is no perfectconductor, all offer some resistance, q. V. , and there is hardly anyperfect non-conductor. It is the reverse and reciprocal of resistance. Conductivity, Specific. The reciprocal of specific resistance. (See Resistance--Specific. ) Conductivity, Unit of. The reciprocal of the ohm; it is a more logical unit, but has never beengenerally adopted; as a name the title mho (or ohm written backwards)has been suggested by Sir William Thomson, and provisionally adopted. Conductivity, Variable. The conductivity for electric currents of conductors varies with theirtemperature, with varying magnetization, tension, torsion andcompression. Conductor. In electricity, anything that permits the passage of an electriccurrent. Any disturbance in the ether takes the form of waves becausethe ether has restitutive force or elasticity. In a conductor, on theother hand, this force is wanting; it opens a path through the ether anda disturbance advances through it from end to end with a wave front, butwith no succession of waves. This advance is the beginning of what istermed a current. It is, by some theorists, attributed to impulses givenat all points along the conductor through the surrounding ether, so thata current is not merely due to an end thrust. If ether waves preclude acurrent on account of their restitutive force, ether waves cannot bemaintained in a conductor, hence conductors should be opaque to light, for the latter is due to ether waves. This is one of the more practicalevery day facts brought out in Clerk Maxwell's electromagnetic theory oflight. The term conductor is a relative one, as except a vacuum there isprobably no substance that has not some conducting power. For relativeconducting power, tables of conductivity, q. V. , should be consulted. The metals beginning with silver are the best conductors, glass is oneof the worst. [Transcriber's note: See "ether" for contemporary comments on this nowdiscarded concept. ] Conductor, Anti-Induction. A current conductor arranged to avoid induction from other lines. Manykinds have been invented and made the subject of patents. A fairapproximation may be attained by using a through metallic circuit andtwisting the wires composing it around each other. Sometimes concentricconductors, one a wire and the other a tube, are used, insulated, oneacting as return circuit for the other. Conductor, Conical. A prime conductor of approximately conical shape, but rounded on allpoints and angles. Its potential is highest at the point. 146 STANDARD ELECTRICAL DICTIONARY. Conductor, Imbricated. A conductor used in dynamo armatures for avoiding eddy currents, made bytwisting together two or more strips of copper. Conductor, Prime. A body often cylindrical or spherical in shape, in any case with nopoints or angles, but rounded everywhere, whose surface, if theconductor itself is not metallic, is made conducting by tinfoil or goldleaf pasted over it. It is supported on an insulating stand and is usedto collect or receive and retain static charges of electricity. Conductors, Equivalent. Conductors of identical resistance. The quotient of the length dividedby the product of the conductivity and cross-section must be the same ineach, if each is of uniform diameter. Conjugate. Adj. Conjugate coils or conductors are coils placed in such relation that thelines of force established by one do not pass through the coils of theother. Hence variations of current in one produce no induced currents inthe other. Connect. V. To bring two ends of a conductor together, or to bring one end of aconductor in connection with another, or in any way to bring about anelectrical connection. Connector. A sleeve with screws or other equivalent device for securing the ends ofwires in electrical contact. A binding-post, q. V. , is an example. Sometimes wire spring-catches are used, the general idea being a devicethat enables wires to be connected or released at will without breakingoff or marring their ends. The latter troubles result from twistingwires together. Consequent Poles. A bar magnet is often purposely or accidentally magnetized so as to haveboth ends of the same polarity, and the center of opposite polarity. Thecenter is said to comprise two consequent poles. (See Magnet, Anomalous. ) Conservation of Electricity. As every charge of electricity has its equal and opposite chargesomewhere, near or far, more or less distributed, the sum of negative isequal always to the sum of positive electrical charges. For thisdoctrine the above title was proposed by Lippman. Contact Breaker. Any contrivance for closing a circuit, and generally for opening andclosing in quick succession. An old and primitive form consisted of avery coarsely cut file. This was connected to one terminal, and theother terminal was drawn over its face, making and breaking contact asit jumped from tooth to tooth. (See Circuit Breaker--do. Automatic, etc. --do. Wheel-do. Pendulum. ) 147 STANDARD ELECTRICAL DICTIONARY. Contact, Electric. A contact between two conductors, such that a current can flow throughit. It may be brought about by simple touch or impact between the endsor terminals of a circuit, sometimes called a dotting contact, or by asliding or rubbing of one terminal on another, or by a wheel rolling ona surface, the wheel and surface representing the two terminals. There are various descriptions of contact, whose names areself-explanatory. The term is applied to telegraph line faults also, andunder this, includes different descriptions of contact with neighboringlines, or with the earth. Contact Electricity. When two dissimilar substances are touched they assume differentelectric potentials. If conductors, their entire surfaces are affected;if dielectrics, only the surfaces which touch each other. (See ContactTheory. ) Contact Faults. A class of faults often called contacts, due to contact of the conductorof a circuit with another conductor. A full or metallic contact is wherepractically perfect contact is established; a partial contact andintermittent contact are self-explanatory. Contact Point. A point, pin or stud, often of platinum, arranged to come in contactwith a contact spring, q. V. , or another contact point or surface, underany determined conditions. Contact Potential Difference. The potential difference established by the contact of two dissimilarsubstances according to the contact theory, q. V. Contact Series. An arrangement or tabulation of substances in pairs, each intermediatesubstance appearing in two pairs, as the last member of the first, andfirst member of the succeeding pair, with the statement of the potentialdifference due to their contact, the positively electrified substancecoming first. The following table of some contact potentials is due toAyrton and Perry:CONTACT SERIES. Difference of Potential in Volts. Zinc--Lead . 210Lead--Tin . 069Tin--Iron . 313Iron--Copper . 146Copper--Platinum . 238Platinum-Carbon . 113 The sum of these differences is 1. 089, which is the contact potentialbetween zinc and carbon. Volta's Law refers to this and states that-- The difference of potential produced by the contact of any two substances is equal to the sum of the differences of potentials between the intervening substances in the contact series. It is to be remarked that the law should no longer be restricted to orstated only for metals. 148 STANDARD ELECTRICAL DICTIONARY. Contact-spring. A spring connected to one lead of an electric circuit, arranged to pressagainst another spring, or contact point, q. V. , under any conditionsdetermined by the construction of the apparatus. (See Bell, Electric--Coil, Induction. ) Contact Theory. A theory devised to explain electrification, the charging of bodies byfriction, or rubbing, and the production of current by the voltaicbattery. It holds that two bodies, by mere contact become oppositelyelectrified. If such contact is increased in extent by rubbing together, the intensity of their electrification is increased. Thiselectrification is accounted for by the assumption of different kineticenergy, or energy of molecular motion, possessed by the two bodies;there being a loss and gain of energy, on the two sides respectively, the opposite electrifications are the result. Then when separated, thetwo bodies come apart oppositely electrified. The above accounts for the frictional production of electricity. In thevoltaic battery, a separation of the atoms of hydrogen and oxygen, andtheir consolidation into molecules occurs, and to such separation andthe opposite electrification of the electrodes by the oxygen andhydrogen, the current is attributed, because the hydrogen goes to oneelectrode, and the oxygen to the other, each giving up or sharing itsown charge with the electrodes to which it goes. If zinc is touched tocopper, the zinc is positively and the copper negatively electrified. Inthe separation of hydrogen and oxygen, the hydrogen is positively andthe oxygen negatively electrified. In the battery, the current is due tothe higher contact difference of oxygen and hydrogen compared to thatbetween zinc and copper. It will be seen that the two contact actions ina battery work against each other, and that the current is due to adifferential contact action. The zinc in a battery is electrifiednegatively because the negative electrification of the oxygen is greaterin amount than its own positive electrification due to contact with thecopper. Contractures. A muscular spasm or tetanus due to the passage of a current ofelectricity; a term in electro-therapeutics. Controlling Field. The magnetic or electro-magnetic field, which is used in galvanometersto control the magnetic needle, tending to restore it to a definiteposition whenever it is turned therefrom. It may be the earth's field orone artificially produced. Controlling Force. In galvanometers and similar instruments, the force used to bring theneedle or indicator back to zero. (See ControllingField--Electro-Magnetic Control--Gravity Control--MagneticControl--Spring Control. ) 149 STANDARD ELECTRICAL DICTIONARY. Convection, Electric. The production of blasts or currents of air (convection streams) frompoints connected to statically charged conductors. The term is sometimesapplied to electric convection of heat. (See Convection of Heat, Electric. ) Convection, Electrolytic. The resistance of acidulated water as a true conductor is known to bevery, almost immeasurably, high. As an electrolytic, its resistance isvery much lower. Hence the current produced between immersed electrodesis theoretically almost null, unless the difference of potential betweenthem is high enough to decompose the liquid. Yet a feeble current toogreat for a true conduction current is sometimes observed when twoelectrodes with potential difference too low to cause decomposition areimmersed in it. Such a current is termed an electrolytic convectioncurrent. It is supposed to be due to various causes. Some attribute itto the presence of free oxygen from the air, dissolved in the water withwhich the hydrogen combines. Others attribute it to the diffusion of thegases of decomposition in the solution; others assume a partialpolarization of the molecules without decomposition. Other theories aregiven, all of which are unsatisfactory. The term is due to Helmholtz. Convection of Heat, Electric. The effect of a current upon the distribution of heat in an unevenlyheated conductor. In some, such as copper, the current tends to equalizethe varying temperatures; the convection is then said to be positive, ascomparable to that of water flowing through an unequally heated tube. Inothers, such as platinum or iron, it is negative, making the heatedparts hotter, and the cooler parts relatively cooler. The effect of the electric current in affecting the distribution of heatin unequally heated metal (Thomson's effect. Q. V. ), is sometimes sotermed. If a current passes through unequally heated iron it tends toincrease the difference of temperature, and the convection is negative;in copper it tends to equalize the temperature, and the convection ispositive. Converter. An induction coil used with the alternating current for changingpotential difference and inversely therewith the available current. Theygenerally lower the potential, and increase the current, and are placedbetween the primary high potential system that connects the houses withthe central station, and the secondary low potential system within thehouses. A converter consists of a core of thin iron sheets, wound with afine primary coil of many convolutions, and a coarse secondary coil offew convolutions. The ratio of convolutions gives the ratio of maximumpotential differences of their terminals between the primary andsecondary coils. The coil may be jacketed with iron to increase thepermeance. (See Alternating Current System. ) Fig. 110. FERRANTI'S CONVERTER OR TRANSFORMER. Fig. 111. SWINBURNE'S HEDGEHOG TRANSFORMER. 150 STANDARD ELECTRICAL DICTIONARY. Co-ordinates, System of. A system for indicating the position of points in space by reference tofixed lines, intersecting at a determined and arbitrary point 0, termedthe origin of co-ordinates. In plane rectangular co-ordinates two linesare drawn through the origin, one horizontal, termed the axis ofabscissas, or axis of X. All distances measured parallel to it, ifunknown, are indicated by x, and are termed abscissas. The other axis isvertical, and is termed the axis of ordinates, or axis of Y. Alldistances measured parallel to it, if unknown, are indicated by y andare termed ordinates. Thus by naming its abscissa and ordinate a pointhas its position with reference to the axes determined, and byindicating the relation between a point, line or curve, and a system ofabscissas and ordinates, the properties of a line or curve can beexpressed algebraically. Co-ordinates may also be inclined to each otherat any other angles, forming oblique co-ordinates; relations may beexpressed partly in angles referred to the origin as a centre, givingpolar co-ordinates. For solid geometry or calculations in threedimensions, a third axis, or axis of Z, is used, distances parallel towhich if unknown are indicated by z. Fig. 112. AXES OF CO-ORDINATES. 151 STANDARD ELECTRICAL DICTIONARY. Cooling Box. In a hydroelectric machine, q. V. , a conduit or chest through which thesteam passes on its way to the nozzles. Its object is to partiallycondense the steam so as to charge it with water vesicles whose frictionagainst the sides of the nozzles produces the electrification . 152 STANDARD ELECTRICAL DICTIONARY. Copper. A metal; one of the elements. Symbol, Cu; atomic weight, 63. 5;equivalent, 63. 5 and 31. 75; valency, 1 and 2; specific gravity, 8. 96. It is a conductor of electricity, whose conductivity is liable tovary greatly on account of impurities. Annealed. Hard drawn. Relative resistance (Silver = 1), 1. 063 1. 086Specific resistance, 1. 598 1. 634 microhms. Resistance of a wire at 0° C. (32° F. ), Annealed. Hard Drawn. (a) 1 foot long, weighing 1 grain, . 2041 ohms . 2083 ohms. (b) 1 foot long, 1/1000 inch thick, 9. 612 " 9. 831 "(c) 1 meter long, weighing 1 gram, . 1424 " . 1453 "(d) 1 meter long, 1 millimeter thick, . 02034 " . 02081 " microhm. Microhm. Resistance of 1 inch cube at 0°C. (32° F. ) . 6292 . 6433 Percentage of resistance change, per 1° C. (1. 8° F. ) at about 20° C. (68° F. ) = 0. 388 per cent. Electro-chemical Equivalent (Hydrogen = . 0105) Cuprous . 6667 Cupric . 3334 In electricity it has been very extensively used as the negative plateof voltaic batteries. It has its most extensive application asconductors for all classes of electrical leads. Copper Bath. A solution of copper used for depositing the metal in the electroplatingprocess. For some metals, such as zinc or iron, which decompose coppersulphate solution, special baths have to be used. The regular bath for copper plating is the following: To water acidulated with 8 to 10 percent. Of sulphuric acid as muchcopper sulphate is added as it will take up at the ordinary temperature. The saturated bath should have a density of 1. 21. It is used cold and iskept in condition by the use of copper anodes, or fresh crystals may beadded from time to time. For deposition on zinc, iron, tin and other metals more electropositivethan copper, the following baths may be used, expressed in parts byweight: Tin Iron and Steel. Cast Iron Cold Hot. And Zinc. Zinc. Sodium Bisulphate, 500 200 300 100Potassium Cyanide, 500 700 500 700Sodium Carbonate, 1000 500 --- ---Copper Acetate, 475 500 350 450Aqua Ammoniae, 350 300 200 150Water, 2500 2500 2500 2500 These are due to Roseleur. 153 STANDARD ELECTRICAL DICTIONARY. Copper Stripping Bath. There is generally no object in stripping copper from objects. It can bedone with any of the regular copper baths using the objects to bestripped as anode. The danger of dissolving the base itself and therebyinjuring the article and spoiling the bath is obvious. Cord Adjuster. A device for shortening or lengthening the flexible cord, or flexiblewire supplying the current, and by which an incandescent lamp issuspended. It often is merely a little block of wood perforated with twoholes through which the wires pass, and in which they are retained inany desired position by friction and their own stiffness. Fig. 113. FLEXIBLE CORD ADJUSTER. Cord, Flexible. A pair of flexible wire conductors, insulated lightly, twisted togetherand forming apparently a cord. They are used for minor services, such assingle lamps and the like, and are designated according to the servicethey perform, such as battery cords, dental cords (for supplying dentalapparatus) and other titles. Core. (a) The conductor or conductors of an electric cable. (See Cable Core. ) (b) The iron mass, generally central in an electro-magnet or armature, around which the wire is coiled. It acts by its high permeance toconcentrate or multiply the lines of force, thus maintaining a moreintense field. (See Armature--Magnet, Electro--Magnet, Field--Core, Laminated). In converters or transformers (See Converter) it oftensurrounds the wire coils. Core-discs. Discs of thin wire, for building up armature cores. (See LaminatedCore. ) The usual form of core is a cylinder. A number of thin discs ofiron are strung upon the central shaft and pressed firmly together byend nuts or keys. This arrangement, it will be seen, gives a cylinder asbasis for winding the wire on. Core-discs, Pierced. Core-discs for an armature of dynamo or motor, which are pierced aroundthe periphery. Tubes of insulating material pass through the peripheralholes, and through these the conductors or windings are carried. Theconductors are thus embedded in a mass of iron and are protected fromeddy currents, and they act to reduce the reluctance of the air gaps. From a mechanical point of view they are very good. For voltages over100 they are not advised. Synonym--Perforated Core-discs. 154 STANDARD ELECTRICAL DICTIONARY. Core-discs, Segmental. Core-discs made in segments, which are bolted together to form acomplete disc or section of the core. The plan is adopted principally onlarge cores. The discs thus made up are placed together to form the coreexactly as in the case of ordinary one piece discs. Fig. 114. PIERCED OR PERFORATED CORE-DISC. Core-discs, Toothed. Core-discs of an armature of a dynamo or motor, which discs are cut intonotches on the periphery. These are put together to form the armaturecore, with the notches corresponding so as to form a series of groovesin which the wire winding is laid. This construction reduces the actualair-gaps, and keeps the wires evenly spaced. Distance-pieces ofbox-wood, m, m, are sometimes used to lead the wires at the ends of thearmature. Fig. 115. TOOTHED CORE-DISC. Core, Laminated. A core of an armature, induction coil or converter or other similarconstruction, which is made up of plates insulated more or lessperfectly from each other. The object of lamination is to prevent theformation of Foucault currents. (See Currents, Foucault. ) As insulation, thin shellacked paper may be used, or sometimes the superficialoxidation of the plates alone is relied on. The plates, in general, arelaid perpendicular to the principal convolutions of the wire, orparallel to the lines of force. The object is to break up currents, andsuch currents are induced by the variation in intensity of the field offorce, and their direction is perpendicular to the lines of force, orparallel to the inducing conductors. A core built up of core discs is sometimes termed a tangentiallylaminated core. Made up of ribbon or wire wound coil fashion, it istermed a radially laminated core. 155 STANDARD ELECTRICAL DICTIONARY. Core Ratio. In a telegraph cable the ratio existing between the diameter of theconducting core and the insulator. To get a ratio approximately accuratein practical calculations, the diameter of the core is taken at 5 percent. Less than its actual diameter. The calculations are thosereferring to the electric constants of the cable, such as its staticcapacity and insulation resistance. Core, Ribbon. For discoidal ring-shaped cores of armatures, iron ribbon is often usedto secure lamination and prevent Foucault currents. Synonym--Tangentially Laminated Core. Core, Ring. A core for a dynamo or motor armature, which core forms a complete ring. Core, Stranded. In an electric light cable, a conducting core made up of a group ofwires laid or twisted together. Core, Tubular. Tubes used as cores for electro-magnets. For very small magnetizingpower, tubular cores are nearly as efficient as solid ones in straightmagnets, because the principal reluctance is due to the air-path. Onincreasing the magnetization the tubular core becomes less efficientthan the solid core, as the reluctance of the air-path becomesproportionately of less importance in the circuit. Corpusants. The sailors' name for St. Elmo's Fire, q. V. Coulomb. The practical unit of quantity of electricity. It is the quantity passedby a current of one ampere intensity in one second. It is equal to 1/10the C. G. S. Electro-magnetic unit of quantity, and to 3, 000, 000, 000 C. G. S. Electrostatic units of quantity. It corresponds to thedecomposition of . 0935 milligrams of water, or to the deposition of1. 11815 milligrams of silver. [Transcriber's note: A coulomb is approximately 6. 241E18 electrons. Twopoint charges of one coulomb each, one meter apart, exerts a force of900, 000 metric tons. ] Coulomb's Laws of Electrostatic Attraction and Repulsion. 1. The repulsions or attractions between two electrified bodies are inthe inverse ratio of the squares of their distance. 2. The distance remaining the same, the force of attraction or repulsionbetween two electrified bodies is directly as the product of thequantities of electricity with which they are charged. 156 STANDARD ELECTRICAL DICTIONARY. Counter, Electric. A device for registering electrically, or by electro-magnetic machinery, the revolutions of shafts, or any other data or factors. Counter-electro-motive Force. A potential difference in a circuit opposed to the main potentialdifference, and hence, resisting the operation of the latter, anddiminishing the current which would be produced without it. It appearsin electric motors, which, to a certain extent, operate as dynamos andreduce the effective electro-motive force that operates them. Itappears in the primary coils of induction coils, and when the secondarycircuit is open, is almost equal to the main electro-motive force, sothat hardly any current can go through them under such conditions. Itappears in galvanic batteries, when hydrogen accumulates on the copperplate, and in other chemical reactions. A secondary battery is chargedby a current in the reverse direction to that which it would normallyproduce. Its own potential difference then appears as acounter-electro-motive force. Synonym--Back Electro-motive Force. Counter-electro-motive Force of Polarization. To decompose a solution by electrolysis, enough electro-motive force isrequired to overcome the energy of composition of the moleculedecomposed. A part of this takes the form of a counter-electromotiveforce, one which, for a greater or less time would maintain a current inthe opposite direction if the original source of current were removed. Thus in the decomposition of water, the electrodes become covered, onewith bubbles of oxygen, the others with bubbles of hydrogen; thiscreates a counter E. M. F. Of polarization. In a secondary battery, theworking current may be defined as due to this cause. Synonym--Back Electro-motive Force of Polarization. Couple. Two forces applied to different points of a straight line, when opposedin direction or unequal in amount, tend to cause rotation about a pointintermediate between their points of application and lying on thestraight line. Such a pair constitute a couple. Couple, Voltaic or Galvanic. The combination of two electrodes, and a liquid or liquids, theelectrodes being immersed therein, and being acted on differentially bythe liquid or liquids. The combination constitutes a source ofelectro-motive force and consequently of current. It is the galvanic orvoltaic cell or battery. (See Battery, Voltaic--ContactTheory--Electro-motive Force--Electro-motive Series. ) Coupling. The joining of cells of a galvanic battery, of dynamos or of otherdevices, so as to produce different effects as desired. 157 STANDARD ELECTRICAL DICTIONARY Couple, Astatic. An astatic couple is a term sometimes applied to astatic needles, q. V. C. P. (a) An abbreviation of or symbol for candle power, q. V. (b) An abbreviation of chemically pure. It is used to indicate a highdegree of purity of chemicals. Thus, in a standard Daniell battery, theuse of C. P. Chemicals may be prescribed or advised. Crater. The depression that forms in the positive carbon of a voltaic arc. (SeeArc, Voltaic. ) Creeping. A phenomenon of capillarity, often annoying in battery jars. Thesolution, by capillarity, rises a little distance up the sides, evaporates, and as it dries more creeps up through it, and to a point alittle above it. This action is repeated until a layer of the salts mayform over the top of the vessel. To avoid it, paraffine is often appliedto the edges of the cup, or a layer of oil, often linseed oil, is pouredon the battery solution, Crith. The weight of a litre of hydrogen at 0º C. (32º F. ), and 760 mm. (30inches) barometric pressure. It is . 0896 grams. The molecular weight ofany gas divided by 2 and multiplied by the value of the crith, gives theweight of a litre of the gas in question. Thus a litre of electrolyticgas, a mixture of two molecules of hydrogen for one of oxygen, with amean molecular weight of 12, weighs (12/2) * . 0896 or . 5376 gram. Critical Speed. (a) The speed of rotation at which a series dynamo begins to excite itsown field. (b) In a compound wound dynamo, the speed at which the same potential isgenerated with the full load being taken from the machine, as would begenerated on open circuit, in which case the shunt coil is the onlyexciter. The speed at which the dynamo is self-regulating. (c) In a dynamo the rate of speed when a small change in the speed ofrotation produces a comparatively great change in the electro-motiveforce. It corresponds to the same current (the critical current) in anygiven series dynamo. Cross. (a) A contact between two electric conductors; qualified to expressconditions as a weather cross, due to rain, a swinging cross when a wireswings against another, etc. (b) vb. To make such contact. Cross-Connecting Board. A special switch board used in telephone exchanges and central telegraphoffices. Its function is, by plugs and wires, to connect the line wireswith any desired section of the main switchboard. The terminals of thelines as they enter the building are connected directly to thecross-connecting board. 158 STANDARD ELECTRICAL DICTIONARY. Cross Connection. A method of disposing of the effects of induction from neighboringcircuits by alternately crossing the two wires of a metallic telephonecircuit, so that for equal intervals they lie to right and left, or oneabove, and one below. [Transcriber's note: Also used to cancel the effect of variations in theambient magnetic field, such as solar activity. ] Crossing Wires. The cutting out of a defective section in a telegraph line, by carryingtwo wires from each side of the defective section across to aneighboring conductor, pressing it for the time into service and cuttingthe other wire if necessary. Cross-magnetizing Effect. A phase of armature interference. The current in an armature of a dynamoor motor is such as to develop lines of force approximately at rightangles to those of the field. The net cross-magnetizing effect is suchcomponent of these lines, as is at right angles to the lines produced bythe field alone. Cross-over Block. A piece of porcelain or other material shaped to receive two wires whichare to cross each other, and hold them so that they cannot come incontact. It is used in wiring buildings, and similar purposes. (SeeCleat, Crossing. ) Cross Talk. On telephone circuits by induction or by contact with other wires soundeffects of talking are sometimes received from other circuits; sucheffects are termed cross talk. Crucible, Electric. A crucible for melting difficultly fusible substances, or for reducingores, etc. , by the electric arc produced within it. Sometimes theheating is due more to current incandescence than to the action of anarc. Fig. 116. ELECTRIC FURNACE OR CRUCIBLE. Crystallization, Electric. Many substances under proper conditions take a crystalline form. Thegreat condition is the passage from the fluid into the solid state. Whensuch is brought about by electricity in any way, the term electriccrystallization may be applied to the phenomenon. A solution of silvernitrate for instance, decomposed by a current, may give crystals ofmetallic silver. 159 STANDARD ELECTRICAL DICTIONARY. Cup, Porous. A cup used in two-fluid voltaic batteries to keep the solutions separateto some extent. It forms a diaphragm through which diffusion inevitablytakes place, but which is considerably retarded, while electrolysis andelectrolytic convection take place freely through its walls. Asmaterial, unglazed pottery is very generally used. In some batteries the cup is merely a receptacle for the soliddepolarizer. Thus, in the Leclanché battery, the cup contains themanganese dioxide and graphite in which the carbon electrode isembedded, but does not separate two solutions, as the battery only usesone. Nevertheless, the composition of the solution outside and insidemay vary, but such variation is incidental only, and not an essential ofthe operation. Current. The adjustment, or effects of a continuous attempt at readjustment ofpotential difference by a conductor, q. V. , connecting two points ofdifferent potential. A charged particle or body placed in a field offorce tends to move toward the oppositely charged end or portion of thefield. If a series of conducting particles or a conducting body are heldso as to be unable to move, then the charge of the field tends, as itwere, to move through it, and a current results. It is really aredistribution of the field and as long as such redistribution continuesa current exists. A current is assumed to flow from a positive to anegative terminal; as in the case of a battery, the current in the outercircuit is assumed to flow from the carbon to the zinc plate, and in thesolution to continue from zinc to carbon. As a memoria technica the zincmay be thought of as generating the current delivering it through thesolution to the carbon, whence it flows through the wire connectingthem. (See Ohm's Law--Maxwell's Theory of Light--Conductor-Intensity. ) [Transcriber's note: Supposing electric current to be the motion ofpositive charge causes no practical difficulty, but the current isactually the (slight) motion of negative electrons. ] Current, After. A current produced by the animal tissue after it has been subjected to acurrent in the opposite direction for some time. The tissue acts like asecondary battery. The term is used in electro-therapeutics. Current, Alternating. Usually defined and spoken of as a current flowing alternately inopposite directions. It may be considered as a succession of currents, each of short duration and of direction opposite to that of itspredecessor. It is graphically represented by such a curve as shown inthe cut. The horizontal line may denote a zero current, that is nocurrent at all, or may be taken to indicate zero electro-motive force. The curve represents the current, or the corresponding electro-motiveforces. The further from the horizontal line the greater is either, andif above the line the direction is opposite to that corresponding to thepositions below the line. Thus the current is alternately in oppositedirections, has periods of maximum intensity, first in one and then inthe opposite sense, and between these, passing from one direction to theother, is of zero intensity. It is obvious that the current may risequickly in intensity and fall slowly, or the reverse, or may rise andfall irregularly. All such phases may be shown by the curve, and a curvedrawn to correctly represent these variations is called thecharacteristic curve of such current. It is immaterial whether theordinates of the curve be taken as representing current strength orelectromotive force. If interpreted as representing electro-motiveforce, the usual interpretation and best, the ordinates above the lineare taken as positive and those below as negative. Synonyms--Reversed Current--Periodic Currents. Fig. 117. CHARACTERISTIC CURVE OF ALTERNATING CURRENT. 160 STANDARD ELECTRICAL DICTIONARY. Current, Atomic. A unit of current strength used in Germany; the strength of a currentwhich will liberate in 24 hours (86, 400 seconds) one gram of hydrogengas, in a water voltameter. The atomic current is equal to 1. 111amperes. In telegraphic work the milliatom is used as a unit, comparableto the milliampere. The latter is now displacing it. Current, Charge. If the external coatings of a charged and uncharged jar are placed inconnection, and if the inner coatings are now connected, afterseparating them they are both found to be charged in the same manner. Inthis process a current has been produced between the outside coatingsand one between the inner ones, to which Dove has given the name ChargeCurrent, and which has all the properties of the ordinary dischargecurrent. (Ganot. ) Current, Circular. A current passing through a circular conductor; a current whose path isin the shape of a circle. Current, Commuted. A current changed, as regards direction or directions, by a commutator, q. V. , or its equivalent. Current, Constant. An unvarying current. A constant current system is one maintaining sucha current. In electric series, incandescent lighting, a constant currentis employed, and the system is termed as above. In arc lighting systems, the constant current series arrangement is almost universal. 161 STANDARD ELECTRICAL DICTIONARY. Current, Continuous. A current of one direction only; the reverse of an alternating current. (See Current, Alternating. ) Current, Critical. The current produced by a dynamo at its critical speed; at that speedwhen a slight difference in speed produces a great difference inelectro-motive force. On the characteristic curve it corresponds to thepoint where the curve bends sharply, and where the electro-motive forceis about two-thirds its maximum. Current, Daniell/U. S. , Daniell/Siemens' Unit. A unit of current strength used in Germany. It is the strength of acurrent produced by one Daniell cell in a circuit of the resistance ofone Siemens' unit. The current deposits 1. 38 grams of copper per hour. It is equal to 1. 16 amperes. Current, Demarcation. In electro-therapeutics, a current which can be taken from an injuredmuscle, the injured portion acting electro-negatively toward theuninjured portion. Current Density. The current intensity per unit of cross-sectional area of the conductor. The expression is more generally used for electrolytic conduction, wherethe current-density is referred to the mean facing areas of theelectrodes, or else to the facing area of the cathode only. The quality of the deposited metal is intimately related to the currentdensity. (See Burning. ) Proper Current Density for Electroplating Amperes Per Square Foot of Cathode. --(Urquhart. )Copper, Acid Bath. 5. 0 to 10. 0" Cyanide Bath, 3. 0 " 5. 0Silver, Double Cyanide, 2. 0 " 5. 0Gold, Chloride dissolved in Potassium Cyanide, 1. 0 " 2. 0Nickel, Double Sulphate, 6. 6 " 8. 0Brass, Cyanide, 2. 0 " 3. 0 Current, Diacritical. A current, which, passing through a helix surrounding an iron core, brings it to one-half its magnetic saturation, q. V. Current, Diaphragm. If a liquid is forced through a diaphragm, a potential differencebetween the liquid on opposite sides of the diaphragm is maintained. Electrodes or terminals of platinum may be immersed in the liquid, and acontinuous current, termed a diaphragm current, may be taken as long asthe liquid is forced through the diaphragm. The potential difference isproportional to the pressure, and also depends on the nature of thediaphragm and on the liquid. 162 STANDARD ELECTRICAL DICTIONARY. Current, Direct. A current of unvarying direction, as distinguished from an alternatingcurrent. It may be pulsatory or intermittent in character, but must beof constant direction. Current, Direct Induced. On breaking a circuit, if it is susceptible of exercisingself-induction, q. V. , an extra current, in the direction of theoriginal is induced, which is called "direct" because in the samedirection as the original. The same is produced by a current in onecircuit upon a parallel one altogether separated from it. (SeeInduction, Electro-Magnetic-Current, Extra. ) Synonym--Break Induced Current. Current, Direction of. The assumed direction of a current is from positively charged electrodeto negatively charged one; in a galvanic battery from the carbon orcopper plate through the outer circuit to the zinc plate and backthrough the electrolyte to the carbon or copper plate. (See Current. ) [Transcriber's note: Current is caused by the motion of negativeelectrons, from the negative pole to the positive. The electron wasdiscovered five years after this publication. ] Current, Displacement. The movement or current of electricity taking place in a dielectricduring displacement. It is theoretical only and can only be assumed tobe of infinitely short duration. (See Displacement, Electric. ) Currents, Eddy Displacement. The analogues of Foucault currents, hypothetically produced in the massof a dielectric by the separation of the electricity or by itselectrification. (See Displacement. ) Current, Extra. When a circuit is suddenly opened or closed a current of very briefduration, in the first case in the same direction, in the other case inthe opposite direction, is produced, which exceeds the ordinary currentin intensity. A high potential difference is produced for an instantonly. These are called extra currents. As they are produced byelectro-magnetic induction, anything which strengthens the field offorce increases the potential difference to which they are due. Thus thewire may be wound in a coil around an iron core, in which case the extracurrents may be very strong. (See Induction, Self-Coil, Spark. ) Current, Faradic. A term in medical electricity for the induced or secondary alternatingcurrent, produced by comparatively high electro-motive force, such asgiven by an induction coil or magneto-generator, as distinguished fromthe regular battery current. 163 STANDARD ELECTRICAL DICTIONARY. Current, Foucault. A current produced in solid conductors, and which is converted into heat(Ganot). These currents are produced by moving the conductors through afield, or by altering the strength of a field in which they arecontained. They are the source of much loss of energy and otherderangement in dynamos and motors, and to avoid them the armature coresare laminated, the plane of the laminations being parallel to the linesof force. (See Core, Laminated. ) The presence of Foucault currents, if of long duration, is shown by theheating of the metal in which they are produced. In dynamo armaturesthey are produced sometimes in the metal of the windings, especially ifthe latter are of large diameter. Synonyms--Eddy Currents--Local Currents--Parasitical Currents. Current, Franklinic. In electro-therapeutics the current produced by a frictional electricmachine. Current, Induced. The current produced in a conductor by varying the conditions of a fieldof force in which it is placed; a current produced by induction. Current Induction. Induction by one current on another or by a portion of a current onanother portion of itself. (See Induction. ) Current Intensity. Current strength, dependent on or defined by the quantity of electricitypassed by such current in a given time. The practical unit of currentintensity is the ampere, equal to one coulomb of quantity per second oftime. Current, Inverse Induced. The current induced in a conductor, when in a parallel conductor or inone having a parallel component a current is started, or is increased instrength. It is opposite in direction to the inducing current and henceis termed inverse. (See Induction, Electro-magnetic. ) The parallelconductors may be in one circuit or in two separate circuits. Synonyms--Make-induced Current--Reverse-induced Current. Current, Jacobi's Unit of. A current which will liberate one cubic centimeter of mixed gases(hydrogen and oxygen) in a water voltameter per minute, the gases beingmeasured at 0º C. (32º F. ) and 760 mm. (29. 92 inches) barometricpressure. It is equal to . 0961 ampere. Current, Joint. The current given by several sources acting together. Properly, itshould be restricted to sources connected in series, thus if two batterycells are connected in series the current they maintain is their jointcurrent. Current, Linear. A current passing through a straight conductor; a current whose pathfollows a straight line. 164 STANDARD ELECTRICAL DICTIONARY. Current, Make and Break. A succession of currents of short duration, separated by absolutecessation of current. Such current is produced by a telegraph key, or bya microphone badly adjusted, so that the circuit is broken at intervals. The U. S. Courts have virtually decided that the telephone operates bythe undulatory currents, and not by a make and break current. Manyattempts have been made to produce a telephone operating by ademonstrable make and break current, on account of the abovedistinction, in hopes of producing a telephone outside of the scope ofthe Bell telephone patent. [Transcriber's note: Contemporary long distance telephone service isdigital, as this item describes. ] Current-meter. An apparatus for indicating the strength of current. (See Ammeter. ) Current, Negative. In the single needle telegraph system the current which deflects theneedle to the left. Current, Nerve and Muscle. A current of electricity yielded by nerves or muscles. Under properconditions feeble currents can be taken from nerves, as the same can betaken from muscles. Current, Opposed. The current given by two or more sources connected in opposition to eachother. Thus a two volt and a one volt battery may be connected inopposition, giving a net voltage of only one volt, and a current due tosuch net voltage. Current, Partial. A divided or branch current. A current which goes through a singleconductor to a point where one or more other conductors join it inparallel, and then divides itself between the several conductors, whichmust join further on, produces partial currents. It produces as manypartial currents as the conductors among which it divides. The point ofdivision is termed the point of derivation. Synonym--Derived Current. Current, Polarizing. In electro-therapeutics, a constant current. Current, Positive. In the single needle telegraph system the current which deflects theneedle to the right. Current, Pulsatory. A current of constant direction, but whose strength is constantlyvarying, so that it is a series of pulsations of current instead of asteady flow. Current, Rectified. A typical alternating current is represented by a sine curve, whoseundulations extend above and below the zero line. If by a simple twomember commutator the currents are caused to go in one direction, inplace of the sine curve a series of short convex curves following oneanother and all the same side of the zero line results. The currents allin the same direction, become what is known as a pulsating current. Synonym--Redressed Current. 165 STANDARD ELECTRICAL DICTIONARY. Current, Rectilinear. A current flowing through a rectilinear conductor. The action ofcurrents depending on their distance from the points where they act, their contour is a controlling factor. This contour is determined by theconductors through which they flow. Current Reverser. A switch or other contrivance for reversing the direction of acurrent in a conductor. Currents, Ampérian. The currents of electricity assumed by Ampere's theory to circulatearound a magnet. As they represent the maintenance of a current or ofcurrents without the expenditure of energy they are often assumed to beof molecular dimensions. As they all go in the same sense of rotationand are parallel to each other the result is the same as if a single setof currents circulated around the body of the magnet. More will be foundon this subject under Magnetism. The Ampérian currents are purelyhypothetical and are predicated on the existence of a field of forceabout a permanent magnet. (See Magnetism, Ampére's Theory of. ) If the observer faces the north pole of a magnet the Ampérian currentsare assumed to go in the direction opposite to that of a watch, and thereverse for the south pole. Figs. 118-119 DIRECTION OF AMPÉRIAN CURRENTS. Currents, Angular. Currents passing through conductors which form an angle with each other. Currents, Angular, Laws of. 1. Two rectilinear currents, the directions of which form an angle witheach other, attract one another when both approach to or recede from theapex of the angle. 2. They repel one another, if one approaches and the other recedes fromthe apex of the angle. 166 STANDARD ELECTRICAL DICTIONARY Currents, Earth. In long telegraph lines having terminal grounds or connected to earthonly at their ends, potential differences are sometimes observed thatare sufficient to interfere with their working and which, of course, canproduce currents. These are termed earth-currents. It will be noted thatthey exist in the wire, not in the earth. They may be of 40 milliamperesstrength, quite enough to work a telegraph line without any battery. Lines running N. E. And S. W. Are most affected; those running N. W. AndS. E. Very much less so. These currents only exist in lines grounded atboth ends, and appear in underground wires. Hence they are notattributable to atmospheric electricity. According to Wilde they are theprimary cause of magnetic storms, q. V. , but not of the periodicalchanges in the magnetic elements. (See Magnetic Elements. ) Synonym--Natural Currents. Current, Secondary. (a) A current induced in one conductor by a variation in the current ina neighboring one; the current produced in the secondary circuit of aninduction coil or alternating current converter. (b) The current given by a secondary battery. This terminology is not tobe recommended. Current, Secretion. In electro-therapeutics, a current due to stimulation of the secretorynerves. Current Sheet. (a) If two terminals of an active circuit are connected to two points ofa thin metallic plate the current spreads over or occupies practically aconsiderable area of such plate, and this portion of the current is acurrent sheet. The general contour of the current sheet can be laid out in lines offlux. Such lines resemble lines of force. Like the latter, they arepurely an assumption, as the current is not in any sense composed oflines. (b) A condition of current theoretically brought about by the Ampériancurrents in a magnet. Each molecule having its own current, thecontiguous portions of the molecules counteract each other and give aresultant zero current. All that remains is the outer sheet of electriccurrent that surrounds the whole. Current, Sinuous. A current passing through a sinuous conductor. Currents, Multiphase. A term applied to groups of currents of alternating type whichconstantly differ from each other by a constant proportion of periods ofalternation. They are produced on a single dynamo, the winding being socontrived that two, three or more currents differing a constant amountin phase are collected from corresponding contact rings. There arevirtually as many windings on the armature as there are currents to beproduced. Separate conductors for the currents must be used throughout. Synonyms--Polyphase Currents--Rotatory Currents. 167 STANDARD ELECTRICAL DICTIONARY. Currents of Motion. In electro-therapeutics, the currents produced in living muscle ornerves after sudden contraction or relaxation. Currents of Rest. In electro-therapeutics, the currents traversing muscular or nervoustissue when at rest. Their existence is disputed. Currents, Orders of. An intermittent current passing through a conductor will inducesecondary alternating currents in a closed circuit near it. Thissecondary current will induce a tertiary current in a third closedcircuit near it, and so on. The induced currents are termed as of thefirst, second, third and other orders. The experiment is carried out byHenry's coils. (See Coils, Henry's. ) Currents, Thermo-electric. These currents, as produced from existing thermo-electric batteries, are generated by low potential, and are of great constancy. The oppositejunctions of the plates can be kept at constant temperatures, as bymelting ice and condensing steam, so that an identical current can bereproduced at will from a thermopile. Thermo-electric currents were used by Ohm in establishing his law. (SeeOhm's Law. ) Current, Swelling. In electro-therapeutics, a current gradually increasing in strength. Current, Undulatory. A current varying in strength without any abrupt transition from actionto inaction, as in the make and break current. The current may becontinually changing in direction (see Current, Alternating), and hence, of necessity, may pass through stages of zero intensity, but suchtransition must be by a graduation, not by an abrupt transition. Suchcurrent may be represented by a curve, such as the curve of sines. It isevident that the current may pass through the zero point as it crossesthe line or changes direction without being a make and break current. When such a current does alternate in direction it is sometimes called a"shuttle current. " The ordinary commercial telephone current and thealternating current is of this type. (See Current, Make and Break. ) Current, Unit. Unit current is one which in a wire of unit length, bent so as to forman arc of a circle of unit length of radius, would act upon a unit pole(see Magnetic Pole, Unit, ) at the center of the circle with unit force. Unit length is the centimeter; unit force is the dyne. [Transcriber's note: The SI definition of an ampere: A current in twostraight parallel conductors of infinite length and negligiblecross-section, 1 metre apart in vacuum, would produce a force equal to2E-7 newton per metre of length. ] 168 STANDARD ELECTRICAL DICTIONARY. Current, Wattless. Whenever there is a great difference in phase in an alternating currentdynamo between volts and current, the true watts are much less than theproduct of the virtual volts and amperes, because the the watts areobtained by multiplying the product of the virtual volts and amperes bythe cosine of the angle of lag (or lead). Any alternating current may beresolved into two components in quadrature with each other, one in phasewith the volts, the other in quadrature therewith, the former is termedby S. P. Thompson the Working Current, the latter the Wattless Current. The greater the angle of lag the greater will be the wattless current. Curve, Arrival. A curve representing the rate of rise of intensity of current at the endof a long conductor when the circuit has been closed at the other end. In the Atlantic cable, for instance, it would require about 108 secondsfor the current at the distant end to attain 9/10 of its full value. Thecurve is drawn with its abscissa representing time and its ordinatescurrent strength. Curve, Characteristic. A curve indicating, graphically, the relations between any two factors, which are interdependent, or which vary simultaneously. Thus in adynamo, the voltage increases with the speed of rotation, and acharacteristic curve may be based on the relations between the speed ofrotation and voltage developed. The current produced by a dynamo varieswith the electro-motive force, and a curve can express the relationsbetween the electro-motive force and the current produced. A characteristic curve is usually laid out by rectangular co-ordinates(see Co-ordinates). Two lines are drawn at right angles to each other, one vertical, and the other horizontal. One set of data are marked offon the horizontal line, say one ampere, two amperes, and so on, in thecase of a dynamo's characteristic curve. For each amperage of current there is a corresponding voltage in thecircuit. Therefore on each ampere mark a vertical is erected, and onthat the voltage corresponding to such amperage is laid off. This givesa series of points, and these points may be connected by a curve. Suchcurve will be a characteristic curve. The more usual way of laying out a curve is to work directly upon thetwo axes. On one is laid off the series of values of one set of data; onthe other the corresponding series of values of the other dependentdata. Vertical lines or ordinates, q. V. , are erected on the horizontalline or axis of abscissas at the points laid off; horizontal lines orabscissas, q. V. , are drawn from the points laid off on the verticalline or axis of ordinates. The characteristic curve is determined by theintersections of each corresponding pair of abscissa and ordinate. 169 STANDARD ELECTRICAL DICTIONARY. Variations exist in characteristic curve methods. Thus to get thecharacteristic of a commutator, radial lines may be drawn from a circlerepresenting its perimeter. Such lines may be of length proportional tothe voltage developed on the commutator at the points whence the linesstart. A cut giving an example of such a curve is given in Fig. 125. (See Curve of Distribution of Potential in Armature. ) There is nothing absolute in the use of ordinates or abscissas. They maybe interchanged. Ordinarily voltages are laid off as ordinates, but thepractise may be reversed. The same liberty holds good for allcharacteristic curves. Custom, however, should be followed. Synonym--Characteristic. Fig. 120. CHARACTERISTIC CURVE OF A DYNAMO WITH HORSE POWER CURVES. Curve, Characteristic, of Converter. The characteristic curve of the secondary circuit of an alternatingcurrent converter. It gives by the usual methods (see Curve, Characteristic, ) the relations between the electro-motive force and thecurrent in the secondary circuit at a fixed resistance. If connected inparallel a constant electro-motive force is maintained, and the curve isvirtually a straight line. If connected in series an elliptical curve isproduced. 170 STANDARD ELECTRICAL DICTIONARY. Curve, Charging. In secondary battery manipulation, a curve indicating the increase ofvoltage as the charging is prolonged. The rise in voltage with theduration of the charging current is not uniform. In one case, shown inthe cut, there was a brief rapid rise of about 0. 1 volt; then a longslow rise for 0. 15 volt; then a more rapid rise for nearly 0. 40 volt, and then the curve became a horizontal line indicating a cessation ofincrease of voltage. The charging rate should be constant. The horizontal line is laid off in hours, the vertical in volts, so thatthe time is represented by abscissas and the voltage by ordinates of thecurve. Fig. 121. CHARGING CURVE OF A SECONDARY BATTERY. Curve, Discharging. A characteristic curve of a storage battery, indicating the fall involtage with hours of discharge. The volts may be laid off on the axisof ordinates, and the hours of discharging on the axis of abscissas. Togive it meaning the rate of discharge must be constant. Curve, Electro-motive Force. A characteristic curve of a dynamo. It expresses the relation betweenits entire electromotive force, as calculated by Ohm's Law, and thecurrent intensities corresponding thereto. To obtain the data the dynamois driven with different resistances in the external circuit and thecurrent is measured for each resistance. This gives the amperes. Thetotal resistance of the circuit, including that of the dynamo, is known. By Ohm's Law the electro-motive force in volts is obtained for each caseby multiplying the total resistance of the circuit in ohms by theamperes of current forced through such resistance. Taking the voltagesthus calculated for ordinates and the corresponding amperages forabscissas the curve is plotted. An example is shown in the cut. 171 STANDARD ELECTRICAL DICTIONARY. Curve, External Characteristic. A characteristic curve of a dynamo, corresponding to the electro-motiveforce curve, except that the ordinates represent the voltages of theexternal circuit, the voltages as taken directly from the terminals ofthe machine, instead of the total electro-motive force of the circuit. The dynamo is run at constant speed. The resistance of the externalcircuit is varied. The voltages at the terminals of the machine and theamperages of current corresponding thereto are determined. Using thevoltages thus determined as ordinates and the corresponding amperages asabscissas the external characteristic curve is plotted. This curve can be mechanically produced. A pencil may be moved against aconstant force by two electro-magnets pulling at right angles to eachother. One must be excited by the main current of the machine, the otherby a shunt current from the terminals of the machine. The point of thepencil will describe the curve. Fig. 122. CHARACTERISTIC CURVE OF A DYNAMO. Curve, Horse Power. Curves indicating electric horse power. They are laid out withco-ordinates, volts being laid off on the axis of ordinates, and ampereson the axis of abscissas generally. The curves are drawn through pointswhere the product of amperes by volts equals 746. On the same diagram 1, 2, 3 .... And any other horse powers can be plotted if within thelimits. See Fig. 120. Curve, Isochasmen. A line drawn on the map of the earth's surface indicating the locus ofequal frequency of auroras. 172 STANDARD ELECTRICAL DICTIONARY. Curve, Life. A characteristic curve showing the relations between the durability andconditions affecting the same in any appliance. It is used most forincandescent lamps. The hours of burning before failure give ordinates, and the rates of burning, expressed indirectly in volts or incandle-power, give abscissas. For each voltage or for each candle-poweran average duration is deducible from experience, so that two dependentsets of data are obtained for the construction of the curve. Curve, Load. A characteristic curve of a dynamo, expressing the relation between itsvoltage and the amount of excitation under a definite condition ofampere load, at a constant speed. The ordinates represent voltage, theabscissas ampere turns in the field, and the curves may be constructedfor a flow of 0, 50, 100, or .. , or any other number of amperes. Fig. 123. LOAD CURVES. Curve, Magnetization. A characteristic curve of an electromagnet, indicating the relation ofmagnetization to exciting current. Laying off on the axis of ordinatesthe quantities of magnetism evoked, and the corresponding strengths ofthe exciting current on the axis of abscissas, the curve can be plotted. It first rises rapidly, indicating a rapid increase of magnetization, but grows nearly horizontal as the iron becomes more saturated. Theeffect due to the coils alone, or the effect produced in the absence ofiron is a straight line, because air does not change in permeability. Curve of Distribution of Potential in Armature. A characteristic curve indicating the distribution of potentialdifference between adjoining sections of the commutator of an armaturein different positions all around it. The potential differences aretaken by a volt-meter or potential galvanometer, connection with thearmature being made by two small metal brushes, held at a distance apartequal to the distance from centre to centre of two adjoining commutatorbars. The curve is laid out as if by polar co-ordinates extending aroundthe cross-section of the commutator, with the distances from thecommutator surface to the curve proportional to the potentialdifferences as determined by shifting the pair of brushes all around thecommutator. The above is S. P. Thompson's method. Another method of W. M. Mordeyinvolves the use of a pilot brush. (See Brush, Pilot. ) Otherwise themethod is in general terms identical with the above. 173 STANDARD ELECTRICAL DICTIONARY. Fig. 124. MAGNETIZATION CURVE. Fig. 125. ARMATURE: CURVE. Fig. 126. DEVELOPMENT OF ARMATURE CURVE. Curve of Dynamo. The characteristic curve of a dynamo. (See Curve, Characteristic. ) Curve of Sines. An undulating curve representing wave motion. It is produced bycompounding a simple harmonic motion, or a two and fro motion like thatof an infinitely long pendulum with a rectilinear motion. Along ahorizontal line points may be laid off to represent equal periods oftime. Then on each point a perpendicular must be erected. The length ofeach must be equal to the length of path traversed by the point up tothe expiration of each one of the given intervals of time. The abscissasare proportional to the times and the ordinates to the sines of anglesproportional to the times. Thus if a circle be drawn upon the line anddivided into thirty-two parts of equal angular value, the sines of theseangles may be taken as the ordinates and the absolute distance or lengthof arc of the angle will give the abscissas. Synonyms--Sine Curve--Sinusoidal Curve--Harmonic Curve. Fig. 127. CURVE OF SINES. 174 STANDARD ELECTRICAL DICTIONARY. Curve of Saturation of the Magnetic Circuit. A characteristic curve whose ordinates may represent the number ofmagnetic lines of force induced in a magnetic circuit, and whoseabscissas may represent the ampere turns of excitation or otherrepresentative of the inducing force. Curve of Torque. A characteristic curve showing the relations between torque, q. V. , andcurrent in a dynamo or motor. Curve, Permeability Temperature. A characteristic curve expressing the changes in permeability of aparamagnetic substance as the temperature changes. The degrees oftemperature may be abscissas, and the permeabilities correspondingthereto ordinates of the curve. Cut In. V. To connect any electric appliance, mechanism or conductor, into acircuit. Cut Out. V. The reverse of to cut in; to remove from a circuit any conductingdevice, and sometimes so arranged as to leave the circuit completed insome other way. Cut Out. An appliance for removing any apparatus from an electric circuit, sothat no more current shall pass through such apparatus, and sometimesproviding means for closing the circuit so as to leave it complete afterthe removal of the apparatus. 175 STANDARD ELECTRICAL DICTIONARY. Cut Out, Automatic. (a) A mechanism for automatically shunting an arc or other lamp when itceases to work properly. It is generally worked by an electro-magnet ofhigh resistance placed in parallel with the arc. If the arc grows toolong the magnet attracts its armature, thereby completing a shunt ofapproximately the resistance of the arc, and which replaces it until thecarbons approach again to within a proper distance. Sometimes a strip orwire of fusible metal is arranged in shunt with the arc. When the arclengthens the current through the wire increases, melts it and a springis released which acts to complete or close a shunt circuit ofapproximately arc-resistance. (b) See Safety Device--Safety Fuse. (c) See below. Cut-out, Magnetic. A magnetic cut-out is essentially a coil of wire with attracted core orarmature. When the coil is not excited the core, by pressing down astrip of metal or by some analogous arrangement, completes the circuit. When the current exceeds a certain strength the core rises as it isattracted and the circuit is opened. Cut-out, Safety. A block of porcelain or other base carrying a safety fuse, which meltsand breaks the circuit before the wire connected to it is dangerouslyheated. Synonyms--Fuse Block--Safety Catch--Safety Fuse. Cut Out, Wedge. A cut out operated by a wedge. The line terminals consist of a springbearing against a plate, the circuit being completed through their pointof contact. A plug or wedge composed of two metallic faces insulatedfrom each other is adapted to wedge the contact open. Terminals of aloop circuit are connected to the faces of the wedge. Thus on sliding itinto place, the loop circuit is brought into series in the main circuit. Synonym--Plug Cut Out--Spring Jack. Cutting of Lines of Force. A field of force is pictured as made up of lines of force; a conductorswept through the field is pictured as cutting these lines. By so doingit produces potential difference or electro-motive force in itself witha current, if the conductor is part of a closed circuit. Cycle of Alternation. A full period of alternation of an alternating current. It beginsproperly at the zero line, goes to a maximum value in one sense andreturns to zero, goes to maximum in the other sense and returns to zero. Cystoscopy. Examination of the human bladder by the introduction of a specialincandescent electric lamp. The method is due to Hitze. 176 STANDARD ELECTRICAL DICTIONARY. Damper. (a) A copper frame on which the wire in a galvanometer is sometimescoiled, which acts to damp the oscillations of the needle. (b) A tube of brass or copper placed between the primary and secondarycoils of an induction coil. It cuts off induction and diminishes thecurrent and potential of the secondary circuit. On pulling it out, thelatter increases. It is used on medical coils to adjust their strengthof action. Damping. Preventing the indicator of an instrument from oscillating in virtue ofits own inertia or elasticity. In a galvanometer it is defined asresistance to quick vibrations of the needle, in consequence of which itis rapidly brought to rest when deflected (Ayrton). In dead-beatgalvanometers (see Galvanometer, Dead-Beat, ) damping is desirable inorder to bring the needle to rest quickly; in ballistic galvanometers(see Galvanometer, Ballistic, ) damping is avoided in order to maintainthe principle of the instrument. Damping may be mechanical, thefrictional resistance of air to an air-vane, or of a liquid to animmersed diaphragm or loosely fitting piston, being employed. Adash-pot, q. V. , is an example of the latter. It may beelectro-magnetic. A mass of metal near a swinging magnetic needle tendsby induced currents to arrest the oscillations thereof, and is used forthis purpose in dead-beat galvanometers. This is termed, sometimes, magnetic friction. The essence of damping is to develop resistance tomovement in some ratio proportional to velocity, so that no resistanceis offered to the indicator slowly taking its true position. (SeeGalvanometer, Dead-Beat. ) Dash-Pot. A cylinder and piston, the latter loosely fitting or perforated, or someequivalent means being provided to permit movement. The cylinder maycontain a liquid such as glycerine, or air only. Thus the piston isperfectly free to move, but any oscillations are damped (see Damping). In some arc lamps the carbon holder is connected to a dash-pot to checktoo sudden movements of the carbon. The attachment may be either to thepiston or to the cylinder. In the Brush lamp the top of the carbonholder forms a cylinder containing glycerine, and in it a looselyfitting piston works. This acts as a dash-pot. Dead Beat. Adj. Reaching its reading quickly; applied to instruments having a movingindicator, which normally would oscillate back and forth a number oftimes before reaching its reading were it not prevented by damping. (SeeGalvanometer, Aperiodic--Damping. ) Dead Earth. A fault in a telegraph line which consists in the wire being thoroughlygrounded or connected to the earth. 177 STANDARD ELECTRICAL DICTIONARY. Dead Point of an Alternator. A two-phase alternator of the ordinary type connected as a motor toanother alternator cannot start itself, as it has dead points where therelations and polarity of field and armature are such that there is notorque or turning power. Dead-Turns. In the winding of an armature, a given percentage of the turns, it maybe 80 per cent. , more or less, is assumed to be active; the other 20 percent. Or thereabouts, is called dead-turns. This portion represents thewire on such portions of the armature as comes virtually outside of themagnetic field. They are termed dead, as not concurring to theproduction of electro-motive force. Dead Wire. (a) The percentage or portion of wire on a dynamo or motor armature thatdoes not concur in the production of electromotive force. Thedead-turns, q. V. , of a drum armature or the inside wire in a Grammering armature are dead wire. (b) A disused and abandoned electric conductor, such as a telegraphwire. (c) A wire in use, but through which, at the time of speaking, nocurrent is passing. Death, Electrical. Death resulting from electricity discharged through the animal system. The exact conditions requisite for fatal results have not beendetermined. High electro-motive force is absolutely essential; achanging current, pulsatory or alternating, is most fatal, possiblybecause of the high electro-motive force of a portion of each period. Amperage probably has something to do with it, although the totalquantity in coulombs may be very small. As applied to the execution ofcriminals, the victim is seated in a chair and strapped thereto. Oneelectrode with wet padded surface is placed against his head or someadjacent part. Another electrode is placed against some of the lowerparts, and a current from an alternating dynamo passed for 15 seconds ormore. The potential difference of the electrodes is given at 1, 500 to2, 000 volts, but of course the maximum may be two or three times themeasured amount, owing to the character of the current. Decalescence. The converse of recalescence, q. V. When a mass of steel is being heatedas it reaches the temperature of recalescence it suddenly absorbs alarge amount of heat, apparently growing cooler. Deci. Prefix originally used in the metric system to signify one-tenth of, nowextended to general scientific units. Thus decimeter means one-tenth ofa meter; decigram, one-tenth of a gram. Declination, Angle of. The angle intercepted between the true meridian and the axis of amagnetic needle at any place. The angle is measured to east or west, starting from the true meridian as zero. 178 STANDARD ELECTRICAL DICTIONARY. Declination of the Magnetic Needle. The deviation of the magnetic needle from the plane of the earth'smeridian. It is also called the variation of the compass. (See MagneticElements. ) Decomposition. The reduction of a compound substance into its constituents, as inchemical analysis. The constituents may themselves be compounds orproximate constituents, or may be elemental or ultimate constituents. Decomposition, Electrolytic. The decomposition or separation of a compound liquid into itsconstituents by electrolysis. The liquid must be an electrolyte, q. V. , and the decomposition proceeds subject to the laws of electrolysis, q. V. See also Electrolytic Analysis. Decrement. When a suspension needle which has been disturbed is oscillating theswings gradually decrease in amplitude if there is any damping, as therealways is. The decrement is the ratio of the amplitude of oneoscillation to the succeeding one. This ratio is the same for anysuccessive swings. De-energize. To cut off its supply of electric energy from an electric motor, or anydevice absorbing and worked by electric energy. Deflagration. The explosive or violent volatilizing and dissipating of a substance byheat, violent oxidation and similar means. It may be applied among otherthings to the destroying of a conductor by an intense current, or thevolatilization of any material by the electric arc. Deflecting Field. The field produced in a galvanometer by the current which is beingtested, and which field deflects the needle, such deflection being themeasure of the current strength. Deflection. In magnetism the movement out of the plane of the magnetic meridian of amagnetic needle, due to disturbance by or attraction towards a mass ofiron or another magnet. Deflection Method. The method of electrical measurements in which the deflection of theindex of the measuring instrument is used as the measure of the currentor other element under examination. It is the opposite of and is to bedistinguished from the zero or null method, q. V. In the latterconditions are established which make the index point to zero and fromthe conditions necessary for this the measurement is deduced. TheWheatstone Bridge, q. V. , illustrates a zero method, the sine or thetangent compass, illustrates a deflection method. The use of deflectionmethods involves calibration, q. V. , and the commercial measuringinstruments, such as ammeters and volt meters, which are frequentlycalibrated galvanometers, are also examples of deflection instruments. 179 STANDARD ELECTRICAL DICTIONARY. Degeneration, Reaction of. The diminished sensibility to electro-therapeutic treatment exhibited bythe human system with continuance of the treatment in question. Thegeneral lines of variation are stated in works on the subject. Deka. Prefix originally used in the metric system to signify multiplying byten, as dekameter, ten meters, dekagram, ten grams; now extended to manyscientific terms. De la Rive's Floating Battery. A small galvanic couple, immersed in a little floating cell andconnected through a coil of wire immediately above them. When theexciting battery solution is placed in the cell the whole, as it floatsin a larger vessel, turns until the coil lies at right angles to themagnetic needle. Sometimes the two plates are thrust through a cork andfloated thus in a vessel of dilute sulphuric acid. A magnet acts to attract or repel the coil in obedience to Ampére'sTheory, (See Magnetism, Ampere's Theory of. ) Delaurier's Solution. A solution for batteries of the Bunsen and Grenet type. It is of thefollowing composition: Water, 2, 000 parts; potassium bichromate, 184 parts; sulphuric acid, 428 parts. Demagnetization. Removal of magnetism from a paramagnetic substance. It is principallyused for watches which have become magnetized by exposure to themagnetic field surrounding dynamos or motors. The general principles of most methods are to rotate the object, as awatch, in a strong field, and while it is rotating to gradually removeit from the field, or to gradually reduce the intensity of the fielditself to zero. A conical coil of wire within which the field isproduced in which the watch is placed is sometimes used, the idea beingthat the field within such a coil is strongest at its base. Such a coilsupplied by an alternating current is found effectual (J. J. Wright). If a magnetized watch is made to turn rapidly at the end of a twistedstring and is gradually brought near to and withdrawn from the poles ofa powerful dynamo it may be considerably improved. A hollow coil of wire connected with a pole changer and dip-battery hasbeen used. The battery creates a strong field within the coil. The watchis placed there and the pole changer is worked so as to reverse thepolarity of the field very frequently. By the same action of the polechanger the plates of the battery are gradually withdrawn from thesolution so as to gradually reduce the magnetic field to zero whileconstantly reversing its polarity. (G. M. Hopkins. ) Steel may be demagnetized by jarring when held out of the magneticmeridian, or by heating to redness. 180 STANDARD ELECTRICAL DICTIONARY. Density, Electric Superficial. The relative quantity of electricity residing as an electric charge upona unit area of surface. It may be positive or negative. Synonyms--Density of Charge--Surface Density. Dental Mallet, Electric. A dentist's instrument for hammering the fillings as inserted intoteeth. It is a little hammer held in a suitable handle, and which ismade to strike a rapid succession of blows by electro-magnetic motormechanism. Depolarization. (a) The removal of permanent magnetism. (See Demagnetization. ) (b) The prevention of the polarization of a galvanic cell. It iseffected in the Grove battery by the reduction of nitric acid; in theBunsen, by the reduction of chromic acid; in the Smee battery, mechanically, by the platinum coated or rather platinized negativeplate. Other examples will be found under the description of variouscells and batteries. A fluid which depolarizes is termed a depolarizeror depolarizing fluid or solution. (See Electropoion Fluid. ) Deposit, Electrolytic. The metal or other substance precipitated by the action of a battery orother current generator. Derivation, Point of. A point where a circuit branches or divides into two or more leads. Theseparate branches then receive derived or partial currents. Desk Push. A press or push button, with small flush rim, for setting into thewoodwork of a desk. Detector. A portable galvanometer, often of simple construction, used for rough orapproximate work. Detector, Lineman's. A portable galvanometer with a high and a low resistance actuating coil, constructed for the use of linemen and telegraph constructors when inthe field, and actually putting up, repairing or testing lines. Deviation, Quadrantal. Deviation of the compass in iron or steel ships due to the magnetizationof horizontal beams by the earth's induction. The effect of thisdeviation disappears when the ship is in the plane of the electricmeridian, or at right angles thereto; its name is taken from the factthat a swing of the ship through a quadrant brings the needle from zerodeviation to a maximum and back to zero. 181 STANDARD ELECTRICAL DICTIONARY. Deviation, Semicircular. Deviation of the compass in iron or steel ships due to verticalinduction. (See Induction, Vertical. ) The effect of this inductiondisappears when the ship is in the electric meridian. Its name isderived from the fact that a swing of the ship through half the circlebrings the needle from zero deviation to a maximum and back to zero. Dextrotorsal. Adj. Wound in the direction or sense of a right-handed screw; the reverse ofsinistrotorsal, q. V. Fig. 128. DEXTROTORSAL HELIX. Diacritical. Adj. (a) The number of ampere turns, q. V. , required to bring an iron core toone half its magnetic saturation, q. V. , is termed the diacriticalnumber. (b) The diacritical point of magnetic saturation is proposed by SylvanusP. Thompson as a term for the coefficient of magnetic saturation whichgives a magnet core one-half its maximum magnetization. Diagnosis, Electro. A medical diagnosis of a patient's condition based on the action ofdifferent parts of the body under electric excitement. Diamagnetic. Adj. Possessing a negative coefficient of magnetic susceptibility; havingpermeability inferior to that of air. Such substances placed between thepoles of a magnet are repelled; if in the form of bars, they tend toturn so as to have their long axis at right angles to the line joiningthe poles. The reason is that the lines of force always seek the easiestpath, and these bodies having higher reluctance than air, impede thelines of force, and hence are as far as possible pushed out of the way. The above is the simplest explanation of a not well understood set ofphenomena. According to Tyndall, "the diamagnetic force is a polarforce, the polarity of diamagnetic bodies being opposed to that ofparamagnetic ones under the same conditions of excitement. " Bismuth isthe most strongly diamagnetic body known; phosphorus, antimony, zinc, and many others are diamagnetic. (See Paramagnetic. ) 182 STANDARD ELECTRICAL DICTIONARY. Diagometer. An apparatus for use in chemical analysis for testing the purity ofsubstances by the time required for a charged surface to be dischargedthrough them to earth. It is the invention of Rousseau. An electrometer is charged with a dry pile. One of its terminals isconnected with one surface of the solution or substance to be tested, and the other with the other surface. The time of discharge gives theindex of the purity of the substance. Diamagnetic Polarity. Treating diamagnetism as due to a polar force, the polarity of adiamagnetic body is the reverse of the polarity of iron or otherparamagnetic bodies. A bar-shaped diamagnetic body in a field of forcetends to place itself at right angles to the lines of force. Diamagnetism. (a) The science or study of diamagnetic substances and phenomena. (b) The magnetic property of a diamagnetic substance. Diameter of Commutation. The points on the commutator of a closed circuit ring--ordrum--armature, which the brushes touch, and whence they take thecurrent, mark the extremities of the diameter of commutation. Were itnot for the lag this would be the diameter at right angles to the lineconnecting the centers of the opposite faces of the field. It is alwaysa little to one side of this position, being displaced in the directionof rotation. In open circuit armatures the brushes are placed on thediameter at right angles to this one, and sometimes the term diameter ofcommutation is applied to it. All that has been said is on thesupposition that the armature divisions correspond not only inconnection but in position with those of the armature coils. Of course, the commutator could be twisted so as to bring the diameter ofcommutation into any position desired. Diapason, Electric. A tuning-fork or diapason kept in vibration by electricity. In generalprinciple the ends of the fork act as armatures for an electro-magnet, and in their motion by a mercury cup or other form of contact they makeand break the circuit as they vibrate. Thus the magnet alternatelyattracts and releases the leg, in exact harmony with its natural periodof vibration. Diaphragm. (a) In telephones and microphones a disc of iron thrown into motion bysound waves or by electric impulses, according to whether it acts as thediaphragm of a transmitter or receiver. It is generally a plate ofjapanned iron such as used in making ferrotype photographs. (SeeTelephone and Microphone. ) (b) A porous diaphragm is often used in electric decomposition cells andin batteries. The porous cup represents the latter use. [Transcriber's note: Japanned--covered with heavy black lacquer, likeenamel paint. ] 183 STANDARD ELECTRICAL DICTIONARY. Dielectric. A non-conductor; a substance, the different parts of which may, after anelectric disturbance, remain, without any process of readjustment, andfor an indefinite period of time, at potentials differing to any extent(Daniell). There is no perfect dielectric. The term dielectric isgenerally only used when an insulator acts to permit induction to takeplace through it, like the glass of a Leyden jar. Dielectric Constant. The number or coefficient expressing the relative dielectric capacity ofa medium or substance. (See Capacity, Specific Inductive. ) Dielectric, Energy of. In a condenser, the conducting coatings are merely to conduct thecurrent all over the surface they cover; the keeping the electricitiesseparated is the work of the dielectric, and represents potential energywhich appears in the discharge. The amount of energy is proportional tothe charge, and to the potential difference. As any electrified bodyimplies an opposite electrification somewhere, and a separatingdielectric, the existence of a condenser is always implied. [Transcriber's note: The energy stored in a capacitor (condenser) is(Q*Q)/2C = (Q*V)/2 = (C*V*V)/2The energy is proportional to the voltage SQUARED or the charge SQUARED. ] Dielectric Polarization. A term due to Faraday. It expresses what he conceived to be thecondition of a dielectric when its opposite faces are oppositelyelectrified. The molecules are supposed to be arranged by theelectrification in a series of polar chains, possibly being originallyin themselves seats of opposite polarities, or having such imparted tothem by the electricities. The action is analogous to that of a magnetpole on a mass of soft iron, or on a pile of iron filings. Dielectric Strain. The strain a solid dielectric is subjected to, when its oppositesurfaces are electrified. A Leyden jar dilates under the strain, andwhen discharged gives a dull sound. The original condition is notimmediately recovered. Jarring, shaking, etc. , assist the recovery fromstrain. The cause of the strain is termed Electric Stress. (See Stress, Electric. ) This is identical with the phenomenon of residual charge. (See Charge, Residual. ) Each loss of charge is accompanied with aproportional return of the dielectric towards its normal condition. Dielectric Resistance. The mechanical resistance a body offers to perforation or destruction bythe electric discharge. Dielectric Strength. The resistance to the disruptive discharge and depending on itsmechanical resistance largely or entirely. It is expressible in voltsper centimeter thickness. Dry air requires 40, 000 volts per centimeterfor a discharge. 184 STANDARD ELECTRICAL DICTIONARY. Differential Winding Working. A method of working an electro-magnet intermittently, so as to avoidsparking. The magnet is wound with two coils. One is connected straightinto the circuit, the other is connected in parallel therewith with aswitch inserted. The coils are so connected that when the switch isclosed the two are in opposition, the current going through them inopposite senses. Thus one overcomes the effect of the other and themagnet core shows no magnetism, provided the two coils are of equalresistance and equal number of convolutions or turns. Fig. 129. DIFFERENTIAL WINDING WORKING OF ELECTRO-MAGNETIC APPARATUS. Diffusion. A term properly applied to the varying current density found inconductors of unequal cross sectional area. In electro-therapeutics itis applied to the distribution of current as it passes through the humanbody. Its density per cross-sectional area varies with the area andwith the other factors. Diffusion Creep. When electrodes of an active circuit are immersed in a solution of anelectrolyte, a current passes electrolytically if there is a sufficientpotential difference. The current passes through all parts of thesolution, spreading out of the direct prism connecting or defined by theelectrodes. To this portion of the current the above term is applied. Ifthe electrodes are small enough in proportion to the distance betweenthem the current transmission or creep outside of the line becomes theprincipal conveyor of the current so that the resistance remains thesame for all distances. Dimensions and Theory of Dimensions. The expression of the unitary value of a physical quantity in one ormore of the units of length (L), time (T) and mass (M) is termed thedimensions of such quantity. Thus the dimension or dimensions of adistance is simply L; of an angle, expressible by dividing the arc bythe radius is L/L; of a velocity, expressible by distance divided bytime--L/T; of acceleration, which is velocity acquired in a unit oftime, and is therefore expressible by velocity divided by time--L/T/T orL/T2; of momentum, which is the product of mass into velocity--M*L/T; ofkinetic energy taken as the product of mass into the square ofvelocity--M*(L2/T2); of potential energy taken as the product of massinto acceleration into space-M*(L/T2)*L reducing to M*(L2/T2). Thetheory is based on three fundamental units and embraces all electricquantities. The simple units generally taken are the gram, centimeterand second and the dimensions of the fundamental compound units areexpressed in terms of these three, forming the centimeter-gram-second orC. G. S. System of units. Unless otherwise expressed or implied theletters L, M and T, may be taken to indicate centimeter, gram and secondrespectively. It is obvious that very complicated expressions ofdimensions may be built up, and that a mathematical expression ofunnamed quantities may be arrived at. Dimensions in their application bythese symbols are subject to the laws of algebra. They were invented byFourier and were brought into prominence by J. Clerk Maxwell. Anotherexcellent definition reads as follows: "By the dimensions of a physicalquantity we mean the quantities and powers of quantities, involved inthe measurement of it. " (W. T. A. Emtage. ) 185 STANDARD ELECTRICAL DICTIONARY. Dimmer. An adjustable choking coil used for regulating the intensity of electricincandescent lights. Some operate by the introduction and withdrawal ofan iron core as described for the choking coil (see Coil, Choking), others by a damper of copper, often a copper ring surrounding the coiland which by moving on or off the coil changes the potential of thesecondary circuit. Dip of Magnetic Needle. The inclination of the magnetic needle. (See Elements, Magnetic. ) Dipping. (a) Acid or other cleaning processes applied by dipping metals incleaning or pickling solutions before plating in the electroplater'sbath. (b) Plating by dipping applies to electroplating without a battery bysimple immersion. Copper is deposited on iron from a solution of coppersulphate in this way. Synonym--Simple Immersion. Dipping Needle. A magnet mounted in horizontal bearings at its centre of gravity. Placedin the magnetic meridian it takes the direction of the magnetic lines offorce of the earth at that point. It is acted on by the verticalcomponent of the earth's magnetism, as it has no freedom of horizontalmovement. (See Magnetic Elements, and Compass, Inclination. ) Directing Magnet. In a reflecting galvanometer the magnet used for controlling themagnetic needle by establishing a field. It is mounted on the spindle ofthe instrument above the coil and needle. Synonym--Controlling Magnet. 186 STANDARD ELECTRICAL DICTIONARY. Direction. (a) The direction of an electric current is assumed to be from apositively charged electrode or terminal to a negatively charged one inthe outer circuit. (See Current. ) (b) The direction of magnetic and electro-magnetic lines of force isassumed to be from north to south pole of a magnet in the outer circuit. It is sometimes called the positive direction. Their general course isshown in the cuts diagrammatically. The circles indicate a compass usedin tracing their course. The magnetic needle tends to place itself inthe direction of or tangential to the lines of force passing nearest it. (c) The direction of electrostatic lines of force is assumed to be outof a positively charged and to a negatively charged surface. Fig. 130. DIRECTION OF LINES OF FORCE OF A PERMANENT MAGNET. Fig. 131, DIRECTION OF LINES OF FORCE OF AN ELECTRO-MAGNET. 187 STANDARD ELECTRICAL DICTIONARY. Directive Power. In magnetism the power of maintaining itself in the plane of themagnetic meridian, possessed by the magnetic needle. Discharge, Brush. The static discharge of electricity into or through the air may be ofthe brush or spark form. The brush indicates the escape of electricityin continuous flow; the spark indicates discontinuity. The conditionsnecessary to the production of one or the other refer to the nature ofthe conductor, and of other conductors in its vicinity and to theelectro-motive force or potential difference; small alterations maytransform one into the other. The brush resembles a luminous core whoseapex touches the conductor. It is accompanied by a slight hissing noise. Its luminosity is very feeble. The negative conductor gives a smallerbrush than that of the positive conductor and discharges it morereadily. When electricity issues from a conductor, remote from anoppositely excited one, it gives an absolutely silent discharge, showingat the point of escape a pale blue luminosity called electric glow, orif it escapes from points it shows a star-like centre of light. It canbe seen in the dark by placing a point on the excited conductor of astatic-electric machine. Synonyms--Silent Discharge--Glow Discharge. Discharge, Conductive. A discharge of a static charge by conduction through a conductor. Discharge, Convective. The discharge of static electricity from an excited conductor throughair or rarefied gas; it is also called the quiet or silent discharge. The luminous effect in air or gas at atmospheric pressures takes theform of a little brush from a small positive electrode; the negativeshows a star. The phenomena of Gassiot's cascade, the philosopher's eggand Geissler tubes, all of which may be referred to, are instances ofconvective discharge. Discharge, Dead Beat. A discharge that is not oscillatory in character. Discharge, Disruptive. A discharge of a static charge through a dielectric. It involvesmechanical perforation of the dielectric, and hence the mere mechanicalstrength of the latter has much to do with preventing it. A disruptivedischarge is often oscillatory in character; this is always the casewith the discharge of a Leyden jar. 188 STANDARD ELECTRICAL DICTIONARY. Discharge, Duration of. The problem of determining this factor has been attacked by variousobservers. Wheatstone with his revolving mirror found it to be 1/24000second. Fedderson, by interposing resistance, prolonged it to 14/10000and again to 138/10000 second. Lucas & Cazin made it from 26 to 47millionths of a second. All these experiments were performed with Leydenjars. Discharge, Impulsive. A disruptive discharge produced between conductors by suddenly producedpotential differences. The self-induction of the conductor plays anespecially important part in discharges thus produced. Discharge, Lateral. (a) A lightning discharge, which sometimes takes place between alightning rod and the building on which it is. (b) In the discharge of a Leyden jar or condenser the discharge whichtakes the alternative path, q. V. Discharge, Oscillatory. The sudden or disruptive discharge of a static condenser, such as aLeyden jar, or of many other charged conductors, is oscillatory incharacter. The direction of the currents rapidly changes, so that thedischarge is really an alternating current of excessively short totalduration. The discharge sends electro-magnetic waves through the ether, which are exactly analogous to those of light but of too long period toaffect the eye. Synonym--Surging Discharge. [Transcriber's note: Marconi's transmission across the English channeloccurs in 1897, five years after the publication of this book. ] Fig. 132. DISCHARGER. Discharger. An apparatus for discharging Leyden jars. It consists of a conductorterminating in balls, and either jointed like a tongs or bent with aspring-action, so that the balls can be set at distances adapted todifferent sized jars. It has an insulating handle or a pair of such. Inuse one ball is brought near to the coating and the other to the spindleball of the jar. When nearly or quite in contact the jar discharges. Synonyms--Discharging Rod--Discharging Tongs. 189 STANDARD ELECTRICAL DICTIONARY. Discharger, Universal. An apparatus for exposing substances to the static discharge spark. Itconsists of a base with three insulating posts. The central post carriesan ivory table to support the object. The two side posts carryconducting rods, terminating in metal balls, and mounted with universaljoints. A violent shock can be given to any object placed on the table. Synonym--Henley's Universal Discharger. Discharge, Silent. This term is sometimes applied to the glow or brush discharge andsometimes to the condition of electric effluvium. (See Discharge, Brush--Effluvium, Electric. ) Discharge, Spark. The discontinuous discharge of high tension electricity through adielectric or into the air produces electric sparks. These are quitestrongly luminous, of branching sinuous shape, and in long sparks theluminosity varies in different parts of the same spark. A sharp noiseaccompanies each spark. High density of charge is requisite for theformation of long sparks. Disconnection. The separation of two parts of, or opening a circuit, as by turning aswitch, unscrewing a binding screw, or the like. The term is sometimesused to indicate a class of faults in telegraph circuits. Disconnectionsmay be total, partial or intermittent, and due to many causes, such asopen or partially replaced switches, oxidized or dirty contact points, or loose joints. Displacement, Electric. A conception of the action of charging a dielectric. The charge is allon the surface. This fact being granted, the theory of displacementholds that charging a body is the displacing of electricity, forcing itfrom the interior on to the surface, or vice versa, producing a positiveor negative charge by displacement of electricity. While displacement istaking place in a dielectric there is assumed to be a movement orcurrent of electricity called a displacement current. Disruptive Tension. When the surface of a body is electrified, it tends to expand, allportions of the surface repelling each other. The film of airsurrounding such a body is electrified too, and is subjected to adisruptive tension, varying in intensity with the square of the density. Dissimulated Electricity. The electricity of a bound charge. (See Charge, Bound. ) Dissociation. The separation of a chemical compound into its elements by asufficiently high degree of heat. All compounds are susceptible ofdissociation, so that it follows that combustion is impossible at hightemperatures. 190 STANDARD ELECTRICAL DICTIONARY. Distance, Critical, of Alternative Path. The length of air gap in an alternative path whose resistance joined tothe impedance of the rest of the conductors of the path just balancesthe impedance of the other path. Distance, Sparking. The distance between electrodes, which a spark from a given Leyden jaror other source will pass across. Synonym--Explosive Distance. Distillation. The evaporation of a liquid by heat, and sometimes in a vacuum, followedby condensation of the vapors, which distil or drop from the end of thecondenser. It is claimed that the process is accelerated by the liquidbeing electrified. Distributing Box. In an electric conduit system, a small iron box provided for givingaccess to the cable for the purpose of making house and minorconnections. Synonym--Hand Hole. Distributing Switches. Switch systems for enabling different dynamos to supply different linesof a system as required. Spring jacks, q. V. , are used for the lines, and plug switches for the dynamo leads. Thus, dynamos can be thrown inor out as desired, without putting out the lights. Distribution of Electric Energy, Systems of. The systems of electric current distribution from central stations orfrom private generating plants, mechanical or battery, the latterprimary or secondary. They include in general the alternating currentsystem and direct current systems. Again, these may be subdivided intoseries and multiple arc, multiple-series and series-multipledistribution, and the three, four, or five wire system may be applied tomultiple arc or multiple series systems. (See AlternatingCurrent--Current System--Multiple Arc--Multiple Series--SeriesMultiple--Three Wire System. ) Door Opener, Electric. An apparatus for opening a door by pushing back the latch. A spring thendraws the door open, and it is closed against the force of the spring bythe person entering. Electro-magnetic mechanism actuates the latch, andis operated by a switch or press-button. Thus a person on the upperfloor can open the hall door without descending. Dosage, Galvanic. In electro-therapeutics the amount of electric current or discharge, andduration of treatment given to patients. Double Carbon Arc Lamp. An arc lamp designed to burn all night, usually constructed with twoparallel sets of carbons, one set replacing the other automatically, thecurrent being switched from the burnt out pair to the other by theaction of the mechanism of the lamp. 191 STANDARD ELECTRICAL DICTIONARY. Double Fluid Theory. A theory of electricity. Electricity is conveniently treated as a fluidor fluids. According to the double fluid hypothesis negative electricityis due to a preponderance of negative fluid and vice versa. Like fluidrepels like, and unlike attracts unlike; either fluid is attracted bymatter; the presence in a body of one or the other induceselectrification; united in equal proportions they neutralize each other, and friction, chemical decomposition and other causes effect theirseparation. The hypothesis, while convenient, is overshadowed by thecertainty that electricity is not really a fluid at all. (See SingleFluid Theory--Fluid, Electric. ) Synonym--Symmer's Theory. [Transcriber's note: Current is the motion of negative electrons in aconductor or plasma. Unequal distribution of electrons is staticelectricity. The relatively immobile nuclei of atoms are positive whenone or more of its electrons is absent and accounts for part of thecurrent in electrolysis and plasmas. ] Double Fluid Voltaic Cell. A cell in which two fluids are used, one generally as depolarizersurrounding the negative plate, the other as excitant surrounding thepositive plate. A porous diaphragm or difference in specific gravitiesis used to keep the solutions separate and yet permit the essentialelectrolytic diffusion. Grove's Cell, Bunsen's Cell, and Daniell's Cell, all of which may be referred to, are of this type, as are many others. Double Wedge. A plug for use with a spring-jack. It has connection strips at its endand another pair a little distance back therefrom, so that it can maketwo loop connections at once. Synonym--Double Plug. Doubler. A continuously acting electrophorous, q. V. ; an early predecessor of themodern electric machines. It is now no longer used. D. P. Abbreviation for Potential Difference. Drag. The pull exercised by a magnetic field upon a conductor moving throughit or upon the motion of an armature in it. Dreh-strom. (German)Rotatory currents; a system of currents alternating in periodicsuccession of phases and producing a rotatory field. (See Field, Rotatory--Multiphase Currents. ) Drill Electric. A drill for metals or rock worked by an electro-magnetic motor. Formetals a rotary motion, for rocks a reciprocating or percussion actionis imparted. It is used by shipbuilders for drilling holes in plateswhich are in place in ships, as its flexible conductors enable it to beplaced anywhere. For rock-drilling a solenoid type of construction isadopted, producing rapid percussion. 192 STANDARD ELECTRICAL DICTIONARY. Drip Loop. A looping downward of wires entering a building, so that rain water, asit runs along the wire, will drip from the lowest part of the loopinstead of following the wire into or against the side of the building. Driving Horns. Projections on the periphery of an armature of a dynamo for holding thewinding in place and preventing its displacement. Various arrangementshave been adopted. They are sometimes wedges or pins and are sometimesdriven into spaces left in the drum core. The toothed disc armaturecores make up an armature in which the ridges formed by the teeth formpractically driving horns. Dronier's Salt. A substance for solution for use in bichromate batteries. It is amixture of one-third potassium bichromate and two-thirds potassiumbisulphate. It is dissolved in water to make the exciting fluid. Drop, Automatic. A switch or circuit breaker, operating to close a circuit by droppingunder the influence of gravity. It is held up by a latch, the circuitremaining open, until the latch is released by a current passing throughan electro-magnet. This attracting an armature lets the drop fall. As itfalls it closes a local or second circuit, and thus may keep a bellringing until it is replaced by hand. It is used in burglar alarms, itsfunction being to keep a bell ringing even though the windows or door bywhich entrance was made is reclosed. 193 STANDARD ELECTRICAL DICTIONARY. Fig. 133. THE MAGIC DRUM. Drum, Electric. A drum with a mechanism within for striking the head with a hammer orsome equivalent method so as to be used as a piece of magical apparatus. In the one shown in the cut a sort of telephone action is used toproduce the sound, the electro-magnet D and armature being quitescreened from observation through the hole. (See Fig. 133) A ring, C, shown in Fig. 133, with two terminals, the latter shown by the unshadedportions a a, and a suspending hook E, also with two terminals, and twosuspending conductors A, B, carry the current to the magnet. A suddenopening or closing of the circuit produces a sound. Dub's Laws. 1. The magnetism excited at any transverse section of a magnet isproportional to the square root of the distance between the givensection and the end. 2. The free magnetism at any given transverse section of a magnet isproportional to the difference between the square root of half thelength of the magnet and the square root of the distance between thegiven section and the nearest end. Duct. The tube or compartment in an electric subway for the reception of acable. (See Conduit, Electric Subway. ) Dyad. A chemical term; an element which in combination replaces two monovalentelements; one which has two bonds or is bivalent. Dyeing, Electric. The producing mordanting or other dyeing effects on goods in dyeing bythe passage of an electric current. Dynamic Electricity. Electricity of relatively low potential and large quantity; currentelectricity as distinguished from static electricity; electricity inmotion. 194 STANDARD ELECTRICAL DICTIONARY. Dynamo, Alternating Current. A dynamo-electric machine for producing an alternating current; analternator. They are classified by S. P. Thompson into three classes--I. Those with stationary field-magnet and rotating armature. II. Those withrotating field magnet and stationary armature. III. Those with bothfield magnet part and armature part stationary, the amount of magneticinduction from the latter through the former being caused to vary oralternate in direction by the revolution of appropriate pieces of iron, called inductors. Another division rests on whether they give one simplealternating current, a two phase current, or whether they give multiphase currents. (See Current, Alternating--Currents, Multiphase. ) A great many kinds of alternators have been constructed. Only an outlineof the general theory can be given here. They are generally multipolar, with north and south poles alternating around the field. The armaturecoils, equal in number in simple current machines, to the poles, arewound in opposite senses, so that the current shall be in one direction, though in opposite senses, in all of them at anyone time. As thearmature rotates the coils are all approaching their poles at one timeand a current in one sense is induced in every second coil, and one inthe other sense in the other coils. They are all in continuous circuitwith two open terminals, each connected to its own insulated connectingring on the shaft. As the coils pass the poles and begin to recede fromthem the direction changes, and the current goes in the other directionuntil the next poles are reached and passed. Thus there are as manychanges of direction of current per rotation as there are coils in thearmature or poles in the field. Fig. 134. ALTERNATING CURRENT DYNAMO WITHSEPARATE EXCITER MOUNTED ON MAIN SHAFT. 195 STANDARD ELECTRICAL DICTIONARY. The field-magnets whose windings may be in series are often excited by aseparate direct current generation. Some are self-exciting, one or moreof the armature coils being separated from the rest, and connected to aspecial commutator, which rectifies its current. By properly spacing the coils with respect to the poles of the field, and connecting each set of coils by itself to separate connecting rings, several currents can be taken from the same machine, which currentsshall have a constant difference in phase. It would seem at first sightthat the same result could be attained by using as many separatealternators as there were currents to be produced. But it would bealmost impossible to preserve the exact relation of currents and currentphase where each was produced by its own machine. The currents wouldoverrun each other or would lag behind. In a single machine withseparate sets of coils the relation is fixed and invariable. Fig. I35. DIAGRAM OF ARRANGEMENT OF ARMATURE COILS ANDCOLLECTING RINGS IN AN ALTERNATING CURRENT DYNAMO. Dynamo, Alternating Current, Regulation of. Transformers, converters, or induction coils are used to regulatealternating current dynamos, somewhat as compound winding is applied inthe case of direct-current dynamos. The arrangement consists inconnecting the primary of an induction coil or transformer into theexternal circuit with its secondary connected to the field circuit. Thusthe transformer conveys current to the field picked up from the maincircuit, and represents to some extent the shunt of a direct-currentmachine. Dynamo, Commercial Efficiency of. The coefficient, q. V. , obtained by dividing the mechanically useful oravailable work of a dynamo by the mechanical energy absorbed by it. Thisonly includes the energy available in the outer circuit, for doinguseful work. 196 STANDARD ELECTRICAL DICTIONARY. Fig. 136. COMPOUND WOUND DYNAMO. Dynamo. Compound. A compound wound dynamo; one which has two coils on its field magnet;one winding is in series with the external circuit and armature; theother winding is in parallel with the armature winding, or else with thearmature winding and field winding, both in series. (See Winding, LongShunt--Winding, Short Shunt. ) Such a dynamo is, to a certain extent, self-regulating, the two coilscounteracting each other, and bringing about a more regular action forvarying currents than that of the ordinary shunt or series dynamo. The extent of the regulation of such a machine depends on theproportions given its different parts. However good the self-regulatingmay be in a compound wound machine, it can only be perfect at oneparticular speed. To illustrate the principle on which the approximate regulation isobtained the characteristic curve diagram may be consulted. Fig. 137. CURVES OF SERIES AND SHUNT WINDINGS SUPERIMPOSED. One curve is the curve of a series winding, the other that of a shuntwinding, and shows the variation of voltage in each with resistance inthe external or working circuit. The variation is opposite in each case. It is evident that the two windings could be so proportioned on acompound machine that the resultant of the two curves would be astraight line. This regulation would then be perfect and automatic, butonly for the one speed. 197 STANDARD ELECTRICAL DICTIONARY. Dynamo, Direct Current. A dynamo giving a current of unvarying direction, as distinguished froman alternator or alternating current dynamo. Dynamo, Disc. A dynamo with a disc armature, such as Pacinotti's disc, q. V. (See alsoDisc, Armature. ) The field magnets are disposed so that the disc rotatesclose to their poles, and the poles face or are opposite to the side orsides of the disc. The active leads of wire are those situated on theface or faces of the disc. Fig. 138. POLECHKO'S DISC DYNAMO. Dynamo-electric Machine. A machine driven by power, generally steam power, and converting themechanical energy expended on driving it into electrical energy of thecurrent form. The parts of the ordinary dynamo may be summarized asfollows: First, A circuit as complete as possible of iron. Such circuitis composed partly of the cores of an electro-magnet or of severalelectro-magnets, and partly of the cylindrical or ring-shaped core of anarmature which fits as closely as practicable between the magnet ends orpoles which are shaped so as to partly embrace it. Second, of coils ofinsulated wire wound upon the field-magnet cores. When these coils areexcited the field-magnets develop polarity and the circuit just spokenof becomes a magnetic circuit, interrupted only by the air gaps betweenthe poles and armatures. Thirdly, of coils of insulated wire upon thearmature core. These coils when rotated in the magnetic field cutmagnetic lines of force and develop electro-motive force. 198 STANDARD ELECTRICAL DICTIONARY. Fourthly, of collecting mechanism, the commutator in direct currentdynamos, attached to the armature shaft and rotating with it. Thisconsists of insulated rings, or segments of rings to which the wirecoils of the armature are connected, and on which two springs of copperor plates of carbon or some other conductor presses. The electro-motiveforce developed by the cutting of lines of force, by the wires of thearmature, shows itself as potential difference between the two springs. If the ends of a conductor are attached, one to each of these brushes, the potential difference will establish a current through the wire. Byusing properly divided and connected segments on the commutator thepotential difference and consequent direction of the current may be keptalways in the same sense or direction. It is now clear that the externalwire may be connected with the windings of the field-magnet. In suchcase the excitement of the field-magnets is derived from the armatureand the machine is self-excited and entirely self-contained. The above is a general description of a dynamo. Sometimes the coils ofthe field-magnets are not connected with the armature, but derive theircurrent from an outside source. Such are termed separately exciteddynamos. Some general features of dynamo generators may be seen in thedefinitions under this head and elsewhere. The general conception is tocut lines of force with a conductor and thus generate electromotiveforce, or in some way to change the number of lines of force within aloop or circuit with the same effect. Dynamo, Electroplating. A dynamo designed for low potential and high current intensity. They arewound for low resistance, frequently several wires being used inparallel, or ribbon, bar or rectangular conductors being employed. Theyare of the direct current type. They should be shunt wound or they areliable to reverse. They are sometimes provided with resistance in theshunt, which is changed as desired to alter the electro-motive force. Dynamo, Equalizing. A combination for three and five-wire systems. A number of armatures orof windings on the same shaft are connected across the leads. If thepotential drops at any pair of mains, the armature will begin to bedriven by the other mains, acting to an extent as an element of a motor, and will raise the potential in the first pair. Dynamo, Far Leading. A motor dynamo, used to compensate the drop of potential in long mains. Into the mains at a distant point a series motor is connected, driving adynamo placed in shunt across the mains. The dynamo thus driven raisesthe potential difference between the two mains. 199 STANDARD ELECTRICAL DICTIONARY. Dynamograph. A printing telegraph in which the message is printed at bothtransmitting and receiving ends. Dynamo, Inductor. A generator in which the armature or current-generating windings are allcomprised upon the poles of the field magnets. Masses of iron, whichshould be laminated and are the inductors, are carried past the fieldmagnet poles concentrating in their passage the lines of force, thusinducing currents in the coils. In one construction shown in the cut thefield magnets a, a .. Are U shaped and are arranged in a circle, theirpoles pointing inwards. A single exciting coil c, c ... Is wound aroundthe circle in the bend of the V-shaped segments. The poles carry thearmature coils e, e ... The laminated inductors i, i ... Are mounted ona shaft S, by spiders h, to be rotated inside the circle of magnets, thus generating an alternating current. Synonym--Inductor Generator. Fig. 139. INDUCTOR DYNAMO. Dynamo, Interior Pole. A dynamo with a ring armature, with field magnet pole pieces whichextend within the ring. 200 STANDARD ELECTRICAL DICTIONARY. Dynamo, Iron Clad. A dynamo in which the iron of the field magnet is of such shape as toenclose the field magnet coils as well as the armature. Dynamometer. A device or apparatus for measuring force applied, or rate ofexpenditure of energy by, or work done in a given time by a machine. Acommon spring balance can be used as a force dynamometer, viz: todetermine how hard a man is pulling and the like. The steam engineindicator represents an energy-dynamometer of the graphic type, theinstrument marking an area whence, with the aid of the fixed factors ofthe engine, the work done may be determined. Prony's Brake, q. V. , is atype of the friction dynamometer, also of the energy type. In the lattertype during the experiment the whole power must be turned on or beexpended on the dynamometer. Dynamo, Motor. A motor dynamo is a machine for (a) converting a continuous current atany voltage to a continuous current of different strength at a differentvoltage or for (b) transforming a continuous current into an alternatingone, and vice versa. For the first type see Transformer, Continuous Current; for the secondtype see Transformer, Alternating Current. Dynamo, Multipolar. A dynamo having a number of field magnet poles, not merely a singlenorth and a single south pole. The field magnet is sometimes of agenerally circular shape with the poles arranged radially within it, thearmature revolving between the ends. Dynamo, Non-polar. A name given by Prof. George Forbes to a dynamo invented by him. In it acylinder of iron rotates within a perfectly self-contained iron-cladfield magnet. The current is taken off by brushes bearing near theperiphery, at two extremities of a diameter. A machine with a disc 18inches in diameter was said to give 3, 117 amperes, with 5. 8 volts E. M. F. Running at 1, 500 revolutions per second. The E. M. F. Of suchmachines varies with the square of the diameter of the disc or cylinder. Dynamo, Open Coil. A dynamo the windings of whose armatures may be grouped in coils, whichare not connected in series, but which have independent terminals. Theseterminals are separate divisions of the commutator and so spaced thatthe collecting brushes touch each pair belonging to the same coilsimultaneously. As the brushes come in contact with the sections formingthe terminals they take current from the coil in question. This coil isnext succeeded by another one, and so on according to the number ofcoils employed. Dynamo, Ring. A dynamo the base of whose field magnets is a ring in general shape, orperhaps an octagon, and with poles projecting inwardly therefrom. 201 STANDARD ELECTRICAL DICTIONARY. Dynamo, Coupling of. Dynamos can be coupled exactly like batteries and with about the samegeneral results. An instance of series coupling would be given by thedynamos in the three wire system when no current is passing through theneutral wire, and when the lamps on each side of it are lighted in equalnumber. Dynamo, Self-exciting. A dynamo which excites its own field. The majority of dynamos are ofthis construction. Others, especially alternating current machines, areseparately excited, the field magnets being supplied with current from aseparate dynamo or current generator. Dynamo, Separate Circuit. A dynamo in which the field magnet coils are entirely disconnected fromthe main circuit, and in which current for the field is supplied byspecial coils carried for the purpose by the same armature, or by aspecial one, in either case a special commutator being provided tocollect the current. Dynamo, Separately Excited. A dynamo whose field magnets are excited by a separate currentgenerator, such as a dynamo or even a battery. Alternating currentdynamos are often of this construction. Direct current dynamos are notgenerally so. The term is the opposite of self-exciting. Fig. 140. SERIES DYNAMO. Dynamo, Series. A dynamo whose armature, field winding, and external circuit are all inseries. In such a dynamo short circuiting or lowering the resistance of theexternal circuit strengthens the field, increases the electro-motiveforce and current strength and may injure the winding by heating thewire, and melting the insulation. 202 STANDARD ELECTRICAL DICTIONARY. Dynamo, Shunt. A dynamo whose field is wound in shunt with the external circuit. Twoleads are taken from the brushes; one goes around the field magnets toexcite them; the other is the external circuit. In such a dynamo the lowering of resistance on the outer circuit takescurrent from the field and lowers the electro-motive force of themachine. Short circuiting has no heating effect. Fig. 141. SHUNT DYNAMO. Dynamo, Single Coil. A dynamo whose field magnet is excited by a single coil. Several suchhave been constructed, with different shapes of field magnet cores, inorder to obtain a proper distribution of poles. Dynamo, Tuning Fork. A dynamo in which the inductive or armature coils were carried at theends of the prongs of a gigantic tuning fork, and were there maintainedin vibration opposite the field magnets. It was invented by T. A. Edison, but never was used. Dynamo, Uni-polar. A dynamo in which the rotation of a conductor effects a continuousincrease in the number of lines cut, by the device of arranging one partof the conductor to slide on or around the magnet. (S. P. Thomson. )Faraday's disc is the earliest machine of this type. 203 STANDARD ELECTRICAL DICTIONARY. Dyne. The C. G. S. Or fundamental unit of force. It is the force which canimpart an acceleration of one centimeter per second to a mass of onegram in one second. It is equal to about 1/981 the weight of a gram, this weight varying with the latitude. Earth. (a) The earth is arbitrarily taken as of zero electrostatic potential. Surfaces in such condition that their potential is unchanged whenconnected to the earth are said to be of zero potential. All othersurfaces are discharged when connected to the earth, whose potential, for the purposes of man at least, never changes. (b) As a magnetic field of force the intensity of the earth's field isabout one-half a line of force per square centimeter. (c) The accidental grounding of a telegraph line is termed an earth, asa dead, total, partial, or intermittent earth, describing the extent andcharacter of the trouble. [Transcriber's note: Fallen power lines can produce voltage gradients onthe earth's surface that make walking in the area dangerous, as inhundreds of volts per foot. Lightning may be associated with substantialchanges in the static ground potential. ] Earth, Dead. A fault, when a telegraph or other conductor is fully connected to earthor grounded at some intermediate point. Synonyms--Solid Earth--Total Earth. Earth, Partial. A fault, when a telegraph or other conductor is imperfectly connected toearth or grounded at some intermediate point. Earth Plate. A plate buried in the earth to receive the ends of telegraph lines orother circuits to give a ground, q. V. A copper plate is often used. Aconnection to a water or gas main gives an excellent ground, far betterthan any plate. When the plate oxidizes it is apt to introduceresistance. Earth Return. The grounding of a wire of a circuit at both ends gives the circuit anearth return. Earth, Swinging. A fault, when a telegraph or other conductor makes intermittentconnection with the earth. It is generally attributable to wind actionswinging the wire, whence the name. Ebonite. Hard vulcanized India rubber, black in color. Specific resistance inohms per cubic centimeter at 46º C. (115º F. ): 34E15 (Ayrton); specificinductive capacity, (air = 1): 2. 56 (Wüllner); 2. 76 (Schiller); 3. 15(Boltzmann). It is used in electrical apparatus for supporting memberssuch as pillars, and is an excellent material for frictional generationof potential. Its black color gives it its name, and is sometimes made apoint of distinction from Vulcanite, q. V. 204 STANDARD ELECTRICAL DICTIONARY. Economic Coefficient. The coefficient of electric efficiency. (See Efficiency, Electric. ) Edison Effect. A continuous discharge resulting in a true current which takes placebetween a terminal of an incandescent lamp filament and a plate placednear it. The lamp must be run at a definitely high voltage to obtain it. Ediswan. An abbreviation for Edison-Swan; the trade name of the incandescent lampused in Great Britain, and of other incandescent system apparatus. Fig. 142. GYMNOTUS ELECTRICUS. Eel, Electric (Gymnotus Electricus). An eel capable of effecting the discharge of very high potentialelectricity, giving painful or dangerous shocks. Its habitat is thefresh water, in South America. Faraday investigated it and estimated itsshock as equal to that from fifteen Leyden jars, each of 1. 66 squarefeet of coating. (See Animal Electricity and Ray, Electric. ) Effect, Counter-inductive. A counter-electro-motive force due to induction, and opposing a current. Efficiency. The relation of work done to energy absorbed. A theoretically perfectmachine would have the maximum efficiency in which the two qualitiesnamed would be equal to each other. Expressed by a coefficient, q. V. , the efficiency in such case would be equal to 1. If a machine producedbut half the work represented by the energy it absorbed, the restdisappearing in wasteful expenditure, in heating the bearings, inovercoming the resistance of the air and in other ways, its efficiencywould be expressed by the coefficient 1/2 or . 5, or if one hundred wasthe basis, by fifty per centum. There are a number of kinds ofefficiencies of an electric generator which are given below. Efficiency, Commercial. Practical efficiency of a machine, obtained by dividing the availableoutput of work or energy of a machine by the energy absorbed by the samemachine. Thus in a dynamo part of the energy is usefully expended inexciting the field magnet, but this energy is not available for use inthe outer circuit, is not a part of the output, and is not part of thedividend. If M represents the energy absorbed, and W the useful or availableenergy, the coefficient of commercial efficiency is equal to W/M. M ismade up of available, unavailable and wasted (by Foucault currents, etc. , ) energy. Calling available energy W, unavailable but utilizedenergy w, and wasted energy m, the expression for the coefficient ofcommercial efficiency becomes W / ( W + w + m ) when M = W + w + m Synonym--Net efficiency. 205 STANDARD ELECTRICAL DICTIONARY. Efficiency, Electrical. In a dynamo or generator the relation of total electric energy produced, both wasted and useful or available to the useful or availableelectrical energy. If we call W the useful electric and w the wastedelectric energy, the coefficient of electrical efficiency is equal to W / ( W + w ) Synonyms--Intrinsic Efficiency--Economic Coefficient--Coefficient ofElectrical Efficiency. Efficiency of Conversion. In a dynamo or generator the relation of energy absorbed to totalelectric energy produced. Part of the electric energy is expended inproducing the field and in other ways. Thus a generator with highefficiency of conversion may be a very poor one, owing to theunavailable electric energy which it produces. The coefficient ofEfficiency of Conversion is obtained by dividing the total electricenergy produced by the energy absorbed in working the dynamo. If Mrepresents the energy absorbed, or work done in driving the dynamo orgenerator, W the useful electric, and w the wasted electrical energy, then the coefficient of efficiency of conversion is equal to (W + w ) / M In the quantity M are included besides available (W) and unavailable (w)electric energy, the totally wasted energy due to Foucault currents, etc. , calling the latter m, the above formula may be given ( W+ w ) / (W + w + m ) This coefficient may refer to the action of a converter, q. V. , in thealternating system. Synonym--Gross Efficiency. Efficiency of Secondary Battery, Quantity. The coefficient obtained by dividing the ampere-hours obtainable from asecondary battery by the ampere hours required to charge it. Efficiency of Secondary Battery, Real. The coefficient obtained by dividing the energy obtainable from asecondary battery by the energy absorbed in charging it. The energy isconveniently taken in watt-hours and includes the consideration of thespurious voltage. (See Battery, Secondary. ) 206 STANDARD ELECTRICAL DICTIONARY. Efflorescence. The appearance of a dry salt upon the walls of a vessel containing asolution above the normal water-line from evaporation of a liquid. Itappears in battery jars and in battery carbons, in the latterinterfering with the electrical connections, and oxidizing or rustingthem. (See Creeping. ) Effluvium, Electric. When a gas is made to occupy the position of dielectric between twooppositely electrified surfaces a peculiar strain or condition of thedielectric is produced, which promotes chemical change. The condition istermed electrical effluvium or the silent discharge. By an apparatusspecially constructed to utilize the condition large amounts of ozoneare produced. Synonym--Silent Discharge. Elastic Curve. A crude expression for a curve without projections or suddensinuosities; such a curve as can be obtained by bending an elastic stripof wood. Electrepeter. An obsolete name for a key, switch or pole changer of any kind. Elasticity, Electric. The phenomenon of the dielectric is described under this term. When apotential difference is established between two parts of the dielectric, a flow of electricity displacement current starts through thedielectric, which current is due to the electric stress, but isinstantly arrested by what has been termed the electric elasticity ofthe dielectric. This is expressed by ( electric stress ) / ( electric strain )and in any substance is inversely proportional to the specific inductivecapacity. Electricity. It is impossible in the existing state of human knowledge to give asatisfactory definition of electricity. The views of various authoritiesare given here to afford a basis for arriving at the general consensusof electricians. We have as yet no conception of electricity apart from the electrifiedbody; we have no experience of its independent existence. (J. E. H. Gordon. ) What is Electricity? We do not know, and for practical purposes it isnot necessary that we should know. (Sydney F. Walker. ) Electricity … is one of those hidden and mysterious powers of naturewhich has thus become known to us through the medium of effects. (Weale's Dictionary of Terms. ) This word Electricity is used to express more particularly the cause, which even today remains unknown, of the phenomena that we are about toexplain. (Amédée Guillemin. ) 207 STANDARD ELECTRICAL DICTIONARY. Electricity is a powerful physical agent which manifests itself mainlyby attractions and repulsions, but also by luminous and heating effects, by violent commotions, by chemical decompositions, and many otherphenomena. Unlike gravity, it is not inherent in bodies, but it isevoked in them by a variety of causes … (Ganot's Physics. ) Electricity and magnetism are not forms of energy; neither are theyforms of matter. They may, perhaps, be provisionally defined asproperties or conditions of matter; but whether this matter be theordinary matter, or whether it be, on the other hand, thatall-pervading ether by which ordinary matter is surrounded, is a questionwhich has been under discussion, and which now may be fairly held to besettled in favor of the latter view. (Daniell's Physics. ) The name used in connection with an extensive and important class ofphenomena, and usually denoting the unknown cause of the phenomena orthe science that treats of them. (Imperial Dictionary. ) Electricity. . . Is the imponderable physical agent, cause, force or themolecular movement, by which, under certain conditions, certainphenomena, chiefly those of attraction and repulsion, . . . Areproduced. (John Angell. ) It has been suggested that if anything can rightly be called"electricity, " this must be the ether itself; and that all electricaland magnetic phenomena are simply due to changes, strains and motions inthe ether. Perhaps negative electrification. . . Means an excess ofether, and positive electrification a defect of ether, as compared withthe normal density. (W. Larden. ) Electricity is the name given to the supposed agent producing thedescribed condition (i. E. Electrification) of bodies. (FleemingJenkin. ) There are certain bodies which, when warm and dry, acquire by friction, the property of attracting feathers, filaments of silk or indeed anylight body towards them. This property is called Electricity, and bodieswhich possess it are said to be electrified. (Linnaeus Cumming. ) What electricity is it is impossible to say, but for the present it isconvenient to look upon it as a kind of invisible something whichpervades all bodies. (W. Perren Maycock. ) What is electricity? No one knows. It seems to be one manifestation ofthe energy which fills the universe and which appears in a variety ofother forms, such as heat, light, magnetism, chemical affinity, mechanical motion, etc. (Park Benjamin. ) 208 STANDARD ELECTRICAL DICTIONARY. The theory of electricity adopted throughout these lessons is, thatelectricity, whatever its true nature, is one, not two; that thisElectricity, whatever it may prove to be, is not matter, and is notenergy; that it resembles both matter and energy in one respect, however, in that it can neither be created nor destroyed. (Sylvanus P. Thomson. ) In Physics a name denoting the cause of an important class of phenomenaof attraction and repulsion, chemical decomposition, etc. , or, collectively, these phenomena themselves. (Century Dictionary. ) A power in nature, often styled the electric fluid, exhibiting itself, when in disturbed equilibrium or in activity, by a circuit movement, thefact of direction in which involves polarity, or opposition ofproperties in opposite directions; also, by attraction for manysubstances, by a law involving attraction between substances of unlikepolarity, and repulsion between those of like; by exhibiting accumulatedpolar tension when the circuit is broken; and by producing heat, light, concussion, and often chemical changes when the circuit passes betweenthe poles, or through any imperfectly conducting substance or space. Itis evolved in any disturbance of molecular equilibrium, whether from achemical, physical, or mechanical cause. (Webster's Dictionary. ) In point of fact electricity is not a fluid at all, and only in a few ofits attributes is it at all comparable to a fluid. Let us ratherconsider electricity to be a condition into which material substancesare thrown. . . (Slingo & Brooker. ) [Transcriber's note: 2008 Dictionary: Phenomena arising from thebehavior of electrons and protons caused by the attraction of particleswith opposite charges and the repulsion of particles with the samecharge. ] Electricity, Cal. The electricity produced in the secondary of a transformer by changes oftemperature in the core. This is in addition to the regularly inducedcurrent. Synonym--Acheson Effect. Electrics. Substances developing electrification by rubbing or friction; asGilbert, the originator of the term, applied it, it would indicatedielectrics. He did not know that, if insulated, any substance was oneof his "electrics. " A piece of copper held by a glass handle becomeselectrified by friction. Electrification. The receiving or imparting an electric charge to a surface; a termusually applied to electrostatic phenomena. Electrization. A term in electro-therapeutics; the subjection of the human system toelectric treatment for curative, tonic or diagnostic purposes. Electro-biology. The science of electricity in its relation to the living organism, whether as electricity is developed by the organism, or as it affectsthe same when applied from an external source. 209 STANDARD ELECTRICAL DICTIONARY. Electro-capillarity. The relations between surface tension, the potential difference and theelectrostatic capacity of fluids in contact. Although nominally incontact such surfaces are separated by about one-twenty-millionth of acentimeter (1/50000000 inch) ; thus a globule of mercury and water inwhich it is immersed constitute an electrostatic accumulator of definiteelectrostatic capacity. Again the mercury and water being in electricconnection differ in potential by contact (see Contact Theory). Adefinite surface tension is also established. Any change in one of thesefactors changes the other also. A current passed through the contactsurfaces will change the surface tension and hence the shape of themercury globule. Shaking the globule will change its shape and capacityand produce a current. Heating will do the same. (See Electrometer, Capillary; and Telephone, Capillary. ) Mercury and water are named asliquids in which the phenomena are most conveniently observed. They areobservable in other parallel cases. Electro-chemical Equivalent. The quantity of an element or compound liberated from or brought intocombination, electrolytically, by one coulomb of electricity. Theelectro-chemical equivalent of hydrogen is found by experiment to be. 0000105 gram. That of any other substance is found by multiplying thisweight by its chemical equivalent referred to hydrogen, which is itsatomic or molecular weight divided by its valency. Thus the atomicweight of oxygen is 16, its valency is 2, its equivalent is 16/2 = 8;its electro-chemical equivalent is equal to . 0000105 X 8 = . 000840 gram. Electro-chemical Series. An arrangement of the elements in the order of their relative electricalaffinities so that each element is electro-negative to all the elementsfollowing it, and electro-positive to the elements preceding it. Theusual series begins with oxygen as the most electro-negative and endswith potassium as the most electro-positive element. There is, ofcourse, no reason why other series of compound radicals, such assulphion (SO4), etc. , should not also be constructed. For each liquidacting on substances a separate series of the substances acted on may beconstructed. Thus for dilute sulphuric acid the series beginning withthe negatively charged or most attacked one is zinc, amalgamated orpure, cadmium, iron, tin, lead, aluminum, nickel, antimony, bismuth, copper, silver, platinum. In other liquids the series is altogetherdifferent. Electro--chemistry. The branch of electricity or of chemistry treating of the relationsbetween electric and chemical force in different compounds andreactions. (See Electrolysis--Electrochemical series--Electro-chemicalEquivalent . ) 210 STANDARD ELECTRICAL DICTIONARY. Electro-culture. The application of electricity to the cultivation of plants. In onesystem wires are stretched or carried across the bed under the surface, and some are connected to one pole and others to the other pole of agalvanic battery of two or more elements. In some experiments improvedresults have thus been obtained. Another branch refers to the action of the electric arc light onvegetation. This has an effect on vegetation varying in results. Electrode. (a) The terminal of an open electric circuit. (b) The terminals of the metallic or solid conductors of an electriccircuit, immersed in an electrolytic solution. (c) The terminals between which a voltaic arc is formed, always inpractice made of carbon, are termed electrodes. (d) In electro-therapeutics many different electrodes are used whosenames are generally descriptive of their shape, character, or uses towhich they are to be applied. Such are aural electrodes for the ears, and many others. (e) The plates of a voltaic battery. Electrode, Indifferent. A term in electro-therapeutics. An electrode to which no therapeuticaction is attributed but which merely provides a second contact with thebody to complete the circuit through the same. The other electrode istermed the therapeutic electrode. Electrodes, Erb's Standards of. Proposed standard sizes for medical electrodes as follows: Name. Diameter. Fine Electrode, 1/2 centimeter . 2 inch Small " 2 " . 8 " Medium " 7. 5 " 3. 0 " Large " 6X2 " 2. 4 X . 8 " Very large " 16x8 " 6. 4 x 3. 2 " Electrodes, Non-polarizable. In electro-therapeutics electrodes whose contact surface is virtuallyporous clay saturated with zinc chloride solution. The series terminatein amalgamated zinc ends, enclosed each in a glass tube, and closed withclay. Contact of metal with the tissues is thus avoided. Electrode, Therapeutic. A term in electro-therapeutics. An electrode applied to the body for thepurpose of inducing therapeutic action, or for giving the basis for anelectric diagnosis of the case. The other electrode is applied tocomplete the circuit only; it is termed the indifferent electrode. Electro-diagnosis. The study of the condition of a patient by the reactions which occur atthe terminals or kathode and anode of an electric circuit applied to theperson. The reactions are divided into kathodic and anodic reactions. 211 STANDARD ELECTRICAL DICTIONARY. Electro-dynamic. Adj. The opposite of electrostatic; a qualification of phenomena due tocurrent electricity. Synonym--Electro-kinetic. Electro-dynamic Attraction and Repulsion. The mutual attraction and repulsion exercised by currents of electricityupon each other. The theory of the cause is based upon stress of theluminiferous ether and upon the reaction of lines of force upon eachother. For a resumé of the theory see Induction, Electro-magnetic. Electro-dynamics. The laws of electricity in a state of motion; the inter-reaction ofelectric currents. It is distinguished from electro-magnetic inductionas the latter refers to the production of currents by induction. Thegeneral laws of electro-dynamics are stated under Induction, Electro-magnetic, q. V. Synonym--Electro-kinetics. Fig. 143. DIAGRAM OF CONNECTIONS OF SIEMENS' ELECTRO-DYNAMOMETER. 212 STANDARD ELECTRICAL DICTIONARY. Electro-dynamometer, Siemens'. An apparatus for measuring currents by the reaction between two coils, one fixed and one movable, through which the current to be measuredpasses. It is one of the oldest commercial ammeters or currentmeasurers. It comprises a fixed coil of a number of convolutions and amovable coil often of only one convolution surrounding the other. Themovable coil is suspended by a filament or thread from a spiral spring. The spring is the controlling factor. Connection is established throughmercury cups so as to bring the two coils in series. In use the springand filament are adjusted by turning a milled head to which they areconnected until the coils are at right angles. Then the current isturned on and deflects the movable coil. The milled head is turned untilthe deflection is overcome. The angle through which the head is turnedis proportional to the square of the current. The movable coil must inits position at right angles to the fixed one lie at right angles to themagnetic meridian. Thus in the diagram, Fig. 143 A B C D is the fixed coil; E F G H is themovable coil; S is the spiral spring attached at K to the movable coil. The arrows show the course of the current as it goes through the coils. Electrolier. A fixture for supporting electric lamps; the analogue in electriclighting of the gasolier or gas chandelier. Often both are combined, thesame fixture being piped and carrying gas burners, as well as beingwired and carrying electric lamps. Electrolysis. The separation of a chemical compound into its constituent parts orelements by the action of the electric current. The compound may bedecomposed into its elements, as water into hydrogen and oxygen, or intoconstituent radicals, as sodium sulphate into sodium and sulphion, whichby secondary reactions at once give sodium hydrate and sulphuric acid. The decomposition proceeds subject to the laws of electrolysis. (SeeElectrolysis, Laws of. ) For decomposition to be produced there is foreach compound a minimum electro-motive force or potential differencerequired. The current passes through the electrolyte or substanceundergoing decomposition entirely by Electrolytic Conduction, q. V. Inaccordance with Grothüss' Hypothesis, q. V. The electrolyte thereforemust be susceptible of diffusion and must be a fluid. The general theory holds that under the influence of a potentialdifference between electrodes immersed in an electrolyte, the moleculestouching the electrodes are polarized, in the opposite sense for eachelectrode. If the potential difference is sufficient the molecules willgive up one of their binary constituents to the electrode, and the otherconstituent will decompose the adjoining molecule, and that one beingseparated into the same two constituents will decompose its neighbor, and so on through the mass until the other electrode is reached. Thisone separates definitely the second binary constituent from themolecules touching it. 213 STANDARD ELECTRICAL DICTIONARY. Thus there is an exact balance preserved. Just as many molecules aredecomposed at one electrode as at the other, and the exact chain ofdecomposition runs through the mass. Each compound electrolyzed developsa binary or two-fold composition, and gives up one constituent to oneelectrode and the other to the other. Fig. 144. ACTION OF MOLECULES IN A SOLUTIONBEFORE AND DURING ELECTROLYSIS. The cut shows the assumed polarization of an electrolyte. The upper rowshows the molecules in irregular order before any potential differencehas been produced, in other words, before the circuit is closed. Thenext row shows the first effects of closing the circuit, and alsoindicates the polarization of the mass, when the potential difference isinsufficient for decomposition. The third row indicates thedecomposition of a chain of molecules, one constituent separating ateach pole. 214 STANDARD ELECTRICAL DICTIONARY. Electrolysis, Laws of. The following are the principal laws, originally discovered byFaraday, and sometimes called Faraday's Laws of Electrolysis: 1. Electrolysis cannot take place unless the electrolyte is a conductor. Conductor here means an electrolytic conductor, one that conducts by itsown molecules traveling, and being decomposed. (See Grothüss'Hypothesis. ) II. The energy of the electrolytic action of the current is the samewherever exercised in different parts of the circuit. III. The same quantity of electricity--that is the same current for thesame period----- decomposes chemically equivalent quantities of thebodies it decomposes, or the weights of elements separated inelectrolytes by the same quantity of electricity (in coulombs or someequivalent unit) are to each other as their chemical equivalent. IV. The quantity of a body decomposed in a given time is proportional tothe strength of the current. To these may be added the following: V. A definite and fixed electro-motive force is required for thedecomposition of each compound, greater for some and less for others. Without sufficient electro-motive force expended on the molecule nodecomposition will take place. (See Current, Convective. ) Electrolyte. A body susceptible of decomposition by the electric current, and capableof electrolytic conduction. It must be a fluid body and thereforecapable of diffusion, and composite in composition. An elemental bodycannot be an electrolyte. Electrolytic Analysis. Chemical analysis by electrolysis. The quantitative separation of anumber of metals can be very effectively executed. Thus, suppose that asolution of copper sulphate was to be analyzed. A measured portion ofthe solution would be introduced into a weighed platinum vessel. Thevessel would be connected to the zinc plate terminal of a battery. Fromthe other terminal of the battery a wire would be brought and wouldterminate in a plate of platinum. This would be immersed in the solutionin the vessel. As the current would pass the copper sulphate would bedecomposed and eventually all the copper would be deposited in a firmcoating on the platinum. The next operations would be to wash the metalwith distilled water, and eventually with alcohol, to dry and to weighthe dish with the adherent copper. On subtracting the weight of the dishalone from the weight of the dish and copper, the weight of the metalliccopper in the solution would be obtained. In similar ways many other determinations are effected. The processes ofanalysis include solution of the ores or other substances to be analyzedand their conversion into proper form for electrolysis. Copper as justdescribed can be precipitated from the solution of its sulphate. Foriron and many other metals solutions of their double alkaline oxalatesare especially available forms for analysis. The entire subject has been worked out in considerable detail byClassen, to whose works reference should be made for details ofprocesses. Electrolytic Convection. It is sometimes observed that a single cell of Daniell battery, forinstance, or other source of electric current establishing too low apotential difference for the decomposition of water seems to produce afeeble but continuous decomposition. This is very unsatisfactorilyaccounted for by the hydrogen as liberated combining with dissolvedoxygen. (Ganot. ) The whole matter is obscure. (See Current, Convection. ) 215 STANDARD ELECTRICAL DICTIONARY. Electrolytic Conduction. Conduction by the travel of atoms or radicals from molecule to moleculeof a substance with eventual setting free at the electrodes of the atomsor radicals as elementary molecules or constituent radicals. A substanceto be capable of acting as an electrolytic conductor must be capable ofdiffusion, and must also have electrolytic conductivity. Such a body iscalled an electrolyte. (See Grothüss' Hypothesis--Electrolysis--Electrolysis, Laws of--Electro-chemical Equivalent. ) Electro-magnet. A mass, in practice always of iron, around which an electric circuit iscarried, insulated from the iron. When a current is passed through thecircuit the iron presents the characteristics of a magnet. (SeeMagnetism, Ampére's Theory of--Solenoid--Lines of Force. ) In generalterms the action of a circular current is to establish lines of forcethat run through the axis of the circuit approximately parallel thereto, and curving out of and over the circuit, return into themselves outsideof the circuit. If a mass of iron is inserted in the axis or elsewherenear such current, it multiplies within itself the lines of force, q. V. (See also Magnetic Permeability--Permeance--Magnetic Induction, Coefficient of Magnetic Susceptibility--Magnetization, Coefficient ofInduced. ) These lines of force make it a magnet. On their direction, which again depends on the direction of the magnetizing current, dependsthe polarity of the iron. The strength of an electro-magnet, belowsaturation of the core (see Magnetic Saturation), is proportional nearlyto the ampere-turns, q. V. More turns for the same current or morecurrent for the same turns increase its strength. In the cut is shown the general relation of current, coils, core andline of force. Assume that the magnet is looked at endwise, the observerfacing one of the poles; then if the current goes around the core in thedirection opposite to that of the hands of a clock, such pole will bethe north pole. If the current is in the direction of the hands of aclock the pole facing the observer will be the south pole. The wholerelation is exactly that of the theoretical Ampérian currents, alreadyexplained. The direction and course of the lines of force created areshown in the cut. The shapes of electro-magnets vary greatly. The cuts show several formsof electro-magnets. A more usual form is the horseshoe or double limbmagnet, consisting generally of two straight cores, wound with wire andconnected and held parallel to each other by a bar across one end, whichbar is called the yoke. In winding such a magnet the wire coils must conform, as regardsdirection of the current in them to the rule for polarity already cited. If both poles are north or both are south poles, then the magnet cannotbe termed a horseshoe magnet, but is merely an anomalous magnet. In thefield magnets of dynamos the most varied types of electro-magnets havebeen used. Consequent poles are often produced in them by the directionof the windings and connections. To obtain the most powerful magnet the iron core should be as short andthick as possible in order to diminish the reluctance of the magneticcircuit. To obtain a greater range of action a long thin shape isbetter, although it involves waste of energy in its excitation. 216 STANDARD ELECTRICAL DICTIONARY. Fig. 145 DIAGRAM OF AN ELECTRO-MAGNET SHOWING RELATION OFCURRENT AND WINDING TO ITS POLARITY AND LINES OF FORCE. Fig. 146. ANNULAR ELECTRO-MAGNET Electro-magnet, Annular. An electro-magnet consisting of a cylinder with a circular groove cut inits face, in which groove a coil of insulated wire is placed. On thepassage of a current the iron becomes polarized and attracts an armaturetowards or against its grooved face. The cut shows the construction ofan experimental one. It is in practice applied to brakes and clutches. In the cut of the electro-magnetic brake (see Brake, Electro-magnetic), C is the annular magnet receiving its current through the brushes, andpressed when braking action is required against the face of the movingwheel. The same arrangement, it can be seen, may apply to a clutch. 217 STANDARD ELECTRICAL DICTIONARY. Fig. 147. BAR ELECTRO-MAGNET. Electro-magnet, Bar. A straight bar of iron surrounded with a magnetizing coil of wire. Barelectromagnets are not much used, the horseshoe type being by far themore usual. Electro-magnet, Club-foot. An electro-magnet, one of whose legs only is wound with wire, the otherbeing bare. Fig. 148. CLUB-FOOT ELECTRO-MAGNETS WITH HINGED ARMATURES. Electro-magnet, Hinged. An electro-magnet whose limbs are hinged at the yoke. On excitation by acurrent the poles tend to approach each other. Fig. 149. ELECTRO-MAGNET, HINGED Electro-magnetic Attraction and Repulsion. The attraction and repulsion due to electromagnetic lines of force, which lines always tend to take as short a course as possible and alsoseek the medium of the highest permeance. This causes them toconcentrate in iron and steel or other paramagnetic substance and todraw them towards a magnet by shortening the lines of force connectingthe two. It is exactly the same attraction as that of the permanentmagnet for its armature, Ampére's theory bringing the latter under thesame title. In the case of two magnets like poles repel and unlikeattract. In the case of simple currents, those in the same directionattract and those in opposite directions repel each other. This refersto constant current reactions. Thus the attraction of unlike poles oftwo magnets is, by the Ampérian theory, the attraction of two sets ofcurrents of similar direction, as is evident from the diagram. Therepulsion of like poles is the repulsion of unlike currents and the sameapplies to solenoids, q. V. (See Magnetism and do. Ampére's Theoryof--Induction, Electro-dynamic--Electro-magnetic Induction. ) 218 STANDARD ELECTRICAL DICTIONARY. Electro-magnetic Control. Control of a magnet, iron armature, or magnetic needle in agalvanometer, ammeter, voltmeter or similar instrument by anelectro-magnetic field, the restitutive force being derived from anelectro-magnet. The restitutive force is the force tending to bring theindex to zero. Electro-magnetic Field of Force. A field of electro-magnetic lines of force, q. V. , established throughthe agency of an electric current. A wire carrying a current issurrounded by circular concentric lines of force which have the axis ofthe wire as the locus of their centres. Electro-magnets produce lines offorce identical with those produced by permanent magnets. (See Field ofForce--Magnetic Field of Force--Controlling Field--Deflecting Field. ) Electro-magnetic Induction. When two currents of unlike direction are brought towards each other, against their natural repulsive tendency work is done, and theconsequent energy takes the form of a temporary increase in bothcurrents. When withdrawn, in compliance with the natural tendency ofrepulsion, the currents are diminished in intensity, because energy isnot expended on the withdrawal, but the withdrawal is at the expense ofthe energy of the system. The variations thus temporarily produced inthe currents are examples of electro-magnetic induction. The currentshave only the duration in each case of the motion of the circuits. Onecircuit is considered as carrying the inducer current and is termed theprimary circuit and its current the primary current, the others aretermed the secondary circuit and current respectively. We may assume asecondary circuit in which there is no current. It is probable thatthere is always an infinitely small current at least, in every closedcircuit. Then an approach of the circuits will induce in the secondaryan instantaneous current in the reverse direction. On separating the twocircuits a temporary current in the same direction is produced in thesecondary. 219 STANDARD ELECTRICAL DICTIONARY. A current is surrounded by lines of force. The approach of two circuits, one active, involves a change in the lines of force about the secondarycircuit. Lines of force and current are so intimately connected that achange in one compels a change in the other. Therefore the inducedcurrent in the secondary may be attributed to the change in the field offorce in which it lies, a field maintained by the primary circuit andcurrent. Any change in a field of force induces a current or change ofcurrent in any closed circuit in such field, lasting as long as thechange is taking place. The new current will be of such direction as tooppose the change. (See Lenz's Law. ) The action as referred to lines of force may be figured as the cuttingof such lines by the secondary circuit, and such cutting may be broughtabout by moving the secondary in the field. (See Lines of Force--Fieldof Force. ) The cutting of 1E8 lines of force per second by a closedcircuit induces an electro-motive force of one volt. (See Induction, Mutual, Coefficient of. ) Electro-magnet, Iron Clad. A magnet whose coil and core are encased in a iron jacket, generallyconnected to one end of the core. This gives at one end two poles, onetubular, the other solid, and concentric with each other. It issometimes called a tubular magnet. Electro-magnet, One Coil. An electro-magnet excited by one coil. In some dynamos the field magnetsare of this construction, a single coil, situated about midway betweenthe poles, producing the excitation. Electro-magnetic Leakage. The leakage of lines of force in an electro-magnet; the same as magneticleakage. (See Magnetic Leakage. ) Electro-magnetic Lines of Force. The lines of force produced in an electro-magnetic field. They areidentical with Magnetic Lines of Force, q. V. (See also Field ofForce-Line of Force. ) Electro-magnetic Stress. The stress in an electro-magnetic field of force, showing itself in thepolarization of light passing through a transparent medium in such afield. (See Magnetic Rotary Polarization. ) Electro-magnetic Theory of Light. This theory is due to J. Clark Maxwell, and the recent Hertz experimentshave gone far to prove it. It holds that the phenomena of light are dueto ether waves, identical in general factors with those produced byelectro-magnetic induction of alternating currents acting on the ether. In a non-conductor any disturbance sets an ether wave in motion owing toits restitutive force; electricity does not travel through such amedium, but can create ether waves in it. Therefore a non-conductor ofelectricity is permeable to waves of ether or should transmit light, orshould be transparent. A conductor on the other hand transmitselectrical disturbances because it has no restitutive force and cannotsupport an ether wave. Hence a conductor should not transmit light, orshould be opaque. With few exceptions dielectrics or non-conductors aretransparent, and conductors are opaque. 220 STANDARD ELECTRICAL DICTIONARY. Again, the relation between the electrostatic and electro-magnet unitsof quantity is expressed by 1 : 30, 000, 000, 000; the latter figure incentimeters gives approximately the velocity of light. Theelectro-magnetic unit depending on electricity in motion should havethis precise relation if an electro-magnetic disturbance was propagatedwith the velocity of light. If an electrically charged body were whirledaround a magnetic needle with the velocity of light, it should act inthe same way as a current circulating around it. This effect to someextent has been shown experimentally by Rowland. A consequence of these conclusions is (Maxwell) that the specificinductive capacity of a non-conductor or dielectric should be equal tothe square of its index of refraction for waves of infinite length. Thisis true for some substances--sulphur, turpentine, petroleum and benzole. In others the specific inductive capacity is too high, e. G. , vegetableand animal oils, glass, Iceland spar, fluor spar, and quartz. Electro-magnetic Unit of Energy. A rate of transference of energy equal to ten meg-ergs per second. Electro-magnetism. The branch of electrical science treating of the magnetic relations of afield of force produced by a current, of the reactions ofelectro-magnetic lines of force, of the electromagnetic field of force, of the susceptibility, permeability, and reluctance of diamagnetic andparamagnetic substances, and of electro-magnets in general. Electro-magnet, Long Range. An electro-magnet so constructed with extended pole pieces or otherwise, as to attract its armature with reasonably constant force over aconsiderable distance. The coil and plunger, q. V. , mechanismsillustrate one method of getting an extended range of action. When atrue electro-magnet is used, one with an iron core, only a very limitedrange is attainable at the best. (See Electro-magnet, Stopped Coil--do. Plunger. ) Electro-magnet, Plunger. An electro-magnet with hollow coils, into which the armature enters as aplunger. To make it a true electro-magnet it must have either a yoke, incomplete core, or some polarized mass of iron. Electro-magnet, Polarized. An electro-magnet consisting of a polarized or permanently magnetizedcore wound with magnetizing coils, or with such coils on soft iron coresmounted on its ends. The coils may be wound and connected so as tocooperate with or work against the permanent magnet on which it ismounted. In Hughes' magnet shown in the cut it is mounted in opposition, so that an exceedingly feeble current will act to displace the armature, a, which is pulled away from the magnet by a spring, s. 221 STANDARD ELECTRICAL DICTIONARY. Fig. 150 HUGHES' POLARIZED ELECTRO-MAGNET Electro-magnets, Interlocking. Electro-magnets so arranged that their armatures interlock. Thus twomagnets, A A and B B, may be placed with their armatures, M and N, atright angles and both normally pulled away from the poles. When thearmature M is attracted a catch on its end is retained by a hole in theend of the other armature N, and when the latter armature N is attractedby its magnet the armature M is released. In the mechanism shown in thecut the movements of the wheel R are controlled. Normally it is heldmotionless by the catch upon the bottom of the armature M, comingagainst the tooth projecting from its periphery. A momentary currentthrough the coils of the magnet A A releases it, by attracting M, whichis caught and retained by N, and leaves it free to rotate. A momentarycurrent through the coils of the magnet B B again releases M, whichdrops down and engages the tooth upon R and arrests its motion. Fig. 151. INTERLOCKING ELECTRO-MAGNETS. 222 STANDARD ELECTRICAL DICTIONARY. Electro-magnet, Stopped Coil. An electro-magnet consisting of a tubular coil, in which a short fixedcore is contained, stopping up the aperture to a certain distance, whilethe armature is a plunger entering the aperture. This gives a longerrange of action than usual. Electro-magnet, Surgical. An electro-magnet, generally of straight or bar form, fitted withdifferent shaped pole pieces, used for the extraction of fragments ofiron or steel from the eyes. Some very curious cases of successfuloperations on the eyes of workmen, into whose eyes fragments of steel oriron had penetrated, are on record. Electro-medical Baths. A bath for the person provided with connections and electrodes forcausing a current of electricity of any desired type to pass through thebody of the bather. Like all electro-therapeutical treatment, it shouldbe administered under the direction of a physician only. Electro-metallurgy. (a) In the reduction of ores the electric current has been proposed butnever extensively used, except in the reduction of aluminum and itsalloys. (See Reduction of Ores, Electric. ) (b) Electro-plating and deposition of metal from solutions is anotherbranch. (See Electroplating and Electrotyping. ) (c) The concentration of iron ores by magnetic attraction may come underthis head. (See Magnetic Concentration of Ores. ) Electrometer. An instrument for use in the measurement of potential difference, by theattraction or repulsion of statically charged bodies. They aredistinguished from galvanometers as the latter are really currentmeasurers, even if wound for use as voltmeters, depending for theiraction upon the action of the current circulating in their coils. Electrometer, Absolute. An electrometer designed to give directly the value of a charge inabsolute units. In one form a plate, a b, of conducting surface issupported or poised horizontally below a second larger plate C, also ofconducting surface. The poised plate is surrounded by a detached guardring--an annular or perforated plate, r g r' g'--exactly level and evenwith it as regards the upper surface. The inner plate is carried by adelicate balance. In use it is connected to one of the conductors andthe lower plate to earth or to the other. The attraction between them isdetermined by weighing. By calculation the results can be made absolute, as they depend on actual size of the plates and their distance, outsideof the potential difference of which of course nothing can be said. If Sis the area of the disc, d the distance of the plates, V-V1 thedifference of their potential, which is to be measured, and F the forcerequired to balance their attraction, we have: F = ( ( V - V1 )^2 * S ) / ( 8 * PI * d^2 ) 223 STANDARD ELECTRICAL DICTIONARY. If V = 0 this reduces to F = ( V^2 * S ) / ( 8 * PI * d^2 ) (2) or V = d * SquareRoot( (8 * PI * F ) / S ) (3) As F is expressed as a weight, and S and a as measures of area andlength, this gives a means of directly obtaining potential values inabsolute measure. (See Idiostatic Method--Heterostatic Method. ) Synonyms--Attracted Disc Electrometer--Weight Electrometer. Fig. 152. SECTION OF BASE OF PORTABLE ELECTROMETER. In some forms the movable disc is above the other, and supported at theend of a balance beam. In others a spring support, arranged so as toenable the attraction to be determined in weight units, is adopted. Thecuts, Figs. 152 and 154, show one of the latter type, the portableelectrometer. The disc portion is contained within a cylindrical vessel. Fig. 153. DIAGRAM ILLUSTRATING THEORY OF ABSOLUTE ELECTROMETER. Referring to Fig. 152 g is the stationary disc, charged through thewire connection r; f is the movable disc, carried by a balance beampoised at i on a horizontal and transverse stretched platinum wire, acting as a torsional spring. The position of the end k of the balancebeam shows when the disc f is in the plane of the guard ring h h. Theend k is forked horizontally and a horizontal sighting wire or hair isfastened across the opening of the fork. When the hair is midway betweentwo dots on a vertical scale the lever is in the sighted position, as itis called, and the disc is in the plane of the guard ring. 224 STANDARD ELECTRICAL DICTIONARY. Fig. 154. PORTABLE ELECTROMETER. The general construction is seen in Fig. 154. There the fixed disc D iscarried by insulating stem g1. The charging electrode is supported by aninsulating stem g2, and without contact with the box passes out of itscover through a guard tube E, with cover, sometimes called umbrella, V. The umbrella is to protect the apparatus from air currents. At m is thesighting lens. H is a lead box packed with pumice stone, moistened withoil of vitriol or concentrated sulphuric acid, to preserve theatmosphere dry. Before use the acid is boiled with some ammoniumsulphate to expel any corrosive nitrogen oxides, which might corrode thebrass. In use the upper disc is charged by its insulated electrode within thetube E; the movable disc is charged if desired directly through the caseof the instrument. The upper disc is screwed up or down by themicrometer head M, until the sighted position is reached. The readingsof the micrometer on the top of the case give the data for calculation. 225 STANDARD ELECTRICAL DICTIONARY. Fig. 155. LIPPMAN'S CAPILLARY ELECTROMETER. Electrometer, Capillary. An electrometer for measuring potential difference by capillary action, which latter is affected by electrostatic excitement. A tube A containsmercury; its end drawn out to a fine aperture dips into a vessel B whichcontains dilute sulphuric acid with mercury under it, as shown. Wiresrunning from the binding-posts a and b connect one with the mercury inA, the other with that in B. The upper end of the tube A connects with athick rubber mercury reservoir T, and manometer H. The surface tensionof the mercury-acid film at the lower end of the tube A keeps all inequilibrium. If now a potential difference is established between a andb, as by connecting a battery thereto, the surface tension is increasedand the mercury rises in the tube B. By screwing down the compressingclamp E, the mercury is brought back to its original position. Themicroscope M is used to determine this position with accuracy. Thechange in reading of the manometer gives the relation of change ofsurface tension and therefore of potential. Each electrometer needsspecial graduation or calibration, but is exceedingly sensitive andaccurate. It cannot be used for greater potential differences than . 6volt, but can measure . 0006 volt. Its electrostatic capacity is so smallthat it can indicate rapid changes. Another form indicates potentialdifference by the movement of a drop of sulphuric acid in a horizontalglass tube, otherwise filled with mercury, and whose ends lead into twomercury cups or reservoirs. The pair of electrodes to be tested areconnected to the mercury vessels. The drop moves towards the negativepole, and its movement for small potential differences (less than onevolt) is proportional to the electro-motive force or potentialdifference. 226 STANDARD ELECTRICAL DICTIONARY. Electrometer Gauge. An absolute electrometer (see Electrometer, Absolute) forming anattachment to a Thomson quadrant electrometer. It is used to test thepotential of the flat needle connected with the inner surface of theLeyden jar condenser of the apparatus. This it does by measuring theattraction between itself and an attracting disc, the latter connectedby a conductor with the interior of the jar. Electrometer, Lane's. A Leyden jar with mounted discharger, so that when charged to a certainpoint it discharges itself. It is connected with one coating of any jarwhose charge is to be measured, which jar is then charged by the othercoating. As the jar under trial becomes charged to a certain point theelectrometer jar discharges itself, and the number of discharges is themeasure of the charge of the other jar. It is really a unit jar, q. V. Fig. 156. THOMSON'S QUADRANT ELECTROMETER. Fig. 157. HENLEY'S QUADRANT ELECTROSCOPE. 227 STANDARD ELECTRICAL DICTIONARY. Electrometer, Quadrant. (a) Sir William Thomson's electrometer, a simple form of which is shownin the cut, consists of four quadrants of metal placed horizontally;above these a broad flat aluminum needle hangs by a very fine wire, acting as torsional suspension. The quadrants are insulated from eachother, but the opposite ones connect with each other by wires. Theapparatus is adjusted so that, when the quadrants are in an unexcitedcondition the needle is at rest over one of the diametrical divisionsbetween quadrants. The needle by its suspension wire is in communicationwith the interior of a Leyden jar which is charged. The whole is coveredwith a glass shade, and the air within is kept dry by a dish ofconcentrated sulphuric acid so that the jar retains its charge for along time and keeps the needle at approximately a constant potential. Ifnow two pairs of quadrants are excited with opposite electricities, aswhen connected with the opposite poles of an insulated galvanic cell, the needle is repelled by one pair and attracted by the other, andtherefore rotates through an arc of greater or less extent. A smallconcave mirror is attached above the needle and its image is reflectedon a graduated screen. This makes the smallest movement visible. Sometimes the quadrants are double, forming almost a complete box, within which the needle moves. (b) Henley's quadrant electrometer is for use on the prime conductor ofan electric machine, for roughly indicating the relative potentialthereof. It consists of a wooden standard attached perpendicularly tothe conductor. Near one end is attached a semi-circular or quadrant arcof a circle graduated into degrees or angular divisions. An index, consisting of a straw with a pith-bell attached to its end hangs fromthe center of curvature of the arc. When the prime conductor is chargedthe index moves up over the scale and its extent of motion indicates thepotential relatively. When the "quadrant electrometer" is spoken of it may always be assumedthat Sir William Thomson's instrument is alluded to. Henley's instrumentis properly termed a quadrant electroscope. (See Electroscope. ) Electro-motive Force. The cause which produces currents of electricity. In general it can beexpressed in difference of potentials, although the term electro-motiveforce should be restricted to potential difference causing a current. Itis often a sustained charging of the generator terminals whence thecurrent is taken. Its dimensions are (work done/the quantity of electricity involved), or ( M * (L^2) /(T^2 ) ) / ((M^. 5) * (L^. 5)) = ( (M^. 5) * (L^1. 5) ) /(T^2) The practical unit of electro-motive force is the volt, q. V. It isoften expressed in abbreviated form, as E. M. D. P. , or simply as D. P. , i. E. , potential difference. Electro-motive force and potential difference are in many casesvirtually identical, and distinctions drawn between them vary withdifferent authors. If we consider a closed electric circuit carrying acurrent, a definite electro-motive force determined by Ohm's law fromthe resistance and current obtains in it. But if we attempt to definepotential difference as proper to the circuit we may quite fail. Potential difference in a circuit is the difference in potential betweendefined points of such circuit. But no points in a closed circuit can befound which differ in potential by an amount equal to the entireelectro-motive force of the circuit. Potential difference is properlythe measure of electro-motive force expended on the portion of a circuitbetween any given points. Electro-motive force of an entire circuit, asit is measured, as it were, between two consecutive points but aroundthe long portion of the circuit, is not conceivable as merely potentialdifference. Taking the circle divided in to degrees as an analogy, theelectro-motive force of the entire circuit might be expressed as 360º, which are the degrees intervening between two consecutive points, measured the long way around the circle. But the potential differencebetween the same two points would be only 1º, for it would be measuredby the nearest path. [Transcriber's notes: If 360º is the "long" way, 0º is the "short". Aformal restatement of the above definition of EMF: "If a charge Q passesthrough a device and gains energy U, the net EMF for that device is theenergy gained per unit charge, or U/Q. The unit of EMF is a volt, ornewton-meter per coulomb. "] 228 STANDARD ELECTRICAL DICTIONARY. Electro-motive Force, Counter. A current going through a circuit often has not only true or ohmicresistance to overcome, but meets an opposing E. M. F. This is termedcounter-electro-motive force. It is often treated in calculations asresistance, and is termed spurious resistance. It may be a part of theimpedance of a circuit. In a primary battery hydrogen accumulating on the negative platedevelops counter E. M. F. In the voltaic arc the differential heating ofthe two carbons does the same. The storage battery is changed by acurrent passing in the opposite direction to its own natural current;the polarity of such a battery is counter E. M. F. Electro-motive Force, Unit. Unit electro-motive force is that which is created in a conductor movingthrough a magnetic field at such a rate as to cut one unit line of forceper second. It is that which must be maintained in a circuit of unitresistance to maintain a current of unit quantity therein. It is thatwhich must be maintained between the ends of a conductor in order thatunit current may do unit work in a second. Electro-motive Intensity. The force acting upon a unit charge of electricity. The mean force isequal to the difference of potential between two points within the fieldsituated one centimeter apart, such distance being measured along thelines of force. The term is due to J. Clerk Maxwell. Electro-motive Series. Arrangement of the metals and carbon in series with the mostelectro-positive at one end, and electronegative at the other end. Thefollowing are examples for different exciting liquids: Dilute Sulphuric Dilute Hydrochloric Caustic PotassiumAcid Acid. Potash. Sulphide. Zinc Zinc Zinc ZincCadmium Cadmium Tin CopperTin Tin Cadmium CadmiumLead Lead Antimony TinIron Iron Lead SilverNickel Copper Bismuth AntimonyBismuth Bismuth Iron LeadAntimony Nickel Copper BismuthCopper Silver Nickel NickelSilver Antimony Silver IronGoldPlatinumCarbon In each series the upper metal is the positive, dissolved or attackedelement. 229 STANDARD ELECTRICAL DICTIONARY. Electro-motograph. An invention of Thomas A. Edison. A cylinder of chalk, moistened withsolution of caustic soda, is mounted so as to be rotated by a handle. Adiaphragm has an arm connected to its center. This arm is pressedagainst the surface of the cylinder by a spring. When the cylinder isrotated, a constant tension is exerted on the diaphragm. If a current ispassed through the junction of arm and cylinder the electrolytic actionalters the friction so as to change the stress upon the diaphragm. If the current producing this effect is of the type produced by thehuman voice through a microphone the successive variations in strainupon the diaphragm will cause it to emit articulate sounds. These areproduced directly by the movement of the cylinder, the electrolyticaction being rather the regulating portion of the operation. Hence veryloud sounds can be produced by it. This has given it the name of theloud- speaking telephone. The same principle may be applied in other ways. But the practicalapplication of the motograph is in the telephone described. Fig. 158. ELECTRO-MOTOGRAPH TELEPHONE Electro-motor. This term is sometimes applied to a current generator, such as a voltaicbattery. Electro-muscular Excitation. A term in medical electricity indicating the excitation of muscle as theeffect of electric currents of any kind. Electro-negative. Adj. Appertaining to negative electrification; thus of the elements oxygen isthe most electro-negative, because if separated by electrolytic actionfrom any combination, it will be charged with negative electricity. 230 STANDARD ELECTRICAL DICTIONARY. Electro-optics. The branch of natural science treating of the relations between lightand electricity. Both are supposed to be phenomena of or due to theluminiferous ether. To it may be referred the following: (a) Electro-magnetic Stress and Magnetic Rotary Polarization; (b) Dielectric Strain; all of which may be referred to in this book; (c) Change in the resistance of a conductor by changes in light to whichit is exposed (see Selenium); (d) The relation of the index of refraction of a dielectric to thedielectric constant (see Electro-magnetic Theory of Light); (e) The identity (approximate) of the velocity of light in centimetersand the relative values of the electrostatic and electro-magnet unitsof intensity, the latter being 30, 000, 000, 000 times greater than theformer, while the velocity of light is 30, 000, 000, 000 centimeters persecond. Electrophoric Action. The action of an electrophorous; utilized in influence machines. (SeeElectrophorous. ) Fig. 159. ELECTROPHOROUS. Electrophorous. An apparatus for the production of electric charges of high potential byelectrostatic induction, q. V. It consists of a disc of insulatingmaterial B, such as resin or gutta percha, which is held in a shallowmetal-lined box or form. The disc may be half an inch thick and a footor more in diameter, or may be much smaller and thinner. A metal disc A, smaller in diameter is provided with an insulating handle which may beof glass, or simply silk suspension strings. To use it the disc B isexcited by friction with a cat-skin or other suitable substance. Themetallic disc is then placed on the cake of resin exactly in its centre, so that the latter disc or cake projects on all sides. Owing toroughness there is little real electric contact between the metal anddielectric. On touching the metal disc a quantity of negativeelectricity escapes to the earth. On raising it from the cake it comesoff excited positively, and gives a spark and is discharged. It can bereplaced, touched, removed and another spark can be taken from it, andso on as long as the cake stays charged. The successive discharges represent electrical energy expended. This isderived from the muscular energy expended by the operator in separatingthe two discs when oppositely excited. As generally used it is thereforean apparatus for converting muscular or mechanical energy into electricenergy. 231 STANDARD ELECTRICAL DICTIONARY. Electro-physiology. The science of the electric phenomena of the animal system. It may alsobe extended to include plants. The great discovery of Galvani with thefrog's body fell into this branch of science. The electric fishes, gymnotus, etc. , present intense phenomena in the same. Electroplating. The deposition by electrolysis of a coating of metal upon a conductingsurface. The simplest system makes the object to be plated the negativeelectrode or plate in a galvanic couple. Thus a spoon or other objectmay be connected by a wire to a plate of zinc. A porous cup is placedinside a battery jar. The spoon is placed in the porous cup and the zincoutside it. A solution of copper sulphate is placed in the porous cup, and water with a little sodium or zinc sulphate dissolved in it, outside. A current starts through the couple, and copper is deposited onthe spoon. A less primitive way is to use a separate battery as the source ofcurrent; to connect to the positive plate by a wire the object to beplated, and a plate of copper, silver, nickel or other metal to theother pole of the battery. On immersing both object and plate (anode) ina bath of proper solution the object will become plated. In general the anode is of the same material as the metal to bedeposited, and dissolving keeps up the strength of the bath. There are agreat many points of technicality involved which cannot be given here. The surface of the immersed object must be conductive. If not a finewire network stretched over it will gradually fill up in the bath andgive a matrix. More generally the surface is made conductive by beingbrushed over with plumbago. This may be followed by a dusting of irondust, followed by immersion in solution ot copper sulphate. This has theeffect of depositing metallic copper over the surface as a starter forthe final coat. Attention must be paid to the perfect cleanliness of the objects, to thecondition of the bath, purity of anodes and current density. Voltaic batteries are largely used for the current as well as speciallow resistance dynamos. Thermo-electric batteries are also used to someextent but not generally. Electro-pneumatic Signals. Signals, such as railroad signals or semaphores, moved by compressedair, which is controlled by valves operated by electricity. The Housetelegraph, which was worked by air controlled by electricity, might comeunder this term, but it is always understood as applied to railroadsignals, or their equivalent. 232 STANDARD ELECTRICAL DICTIONARY. Electropoion Fluid. An acid depolarizing solution for use in zinc-carbon couples, such asthe Grenet battery. The following are formulae for its preparation: (a) Dissolve one pound of potassium bichromate in ten pounds of water, to which two and one-half pounds of concentrated sulphuric acid havebeen gradually added. The better way is to use powdered potassiumbichromate, add it to the water first, and then gradually add thesulphuric acid with constant stirring. (b) To three pints of water add five fluid ounces of concentratedsulphuric acid; add six ounces pulverized potassium bichromate. (c) Mix one gallon concentrated sulphuric acid and three gallons ofwater. In a separate vessel dissolve six pounds potassium bichromate intwo gallons of boiling water. Mix the two. The last is the best formula. Always use electropoion fluid cold. (SeeTrouvé's Solution--Poggendorff's Solution--Kakogey's Solution--Tissandrier's Solution--Chutaux's Solution. ) Electro-positive. Adj. Appertaining to positive electrification; thus potassium is the mostelectro-positive of the elements. (See Electro-negative. ) Electro-puncture. The introduction into the system of a platinum point or needle, insulated with vulcanite, except near its point, and connected as theanode of a galvanic battery. The kathode is a metal one, covered with awet sponge and applied on the surface near the place of puncture. It isused for treatment of aneurisms or diseased growths, and also forremoval of hair by electrolysis. (See Hair, Removal of by Electrolysis. ) Synonym--Galvano-puncture. Electro-receptive. Adj. A term applied to any device or apparatus designed to receive and absorbelectric energy. A motor is an example of an electro-receptivemechanism. Electroscope. An apparatus for indicating the presence of an electric charge, and alsofor determining the sign, or whether the charge is positive or negative. The simplest form consists of a thread doubled at its centre and hungtherefrom. On being charged, or on being connected to a charged body thethreads diverge. A pair of pith balls may be suspended in a similar way, or a couple of strips of gold leaf within a flask (the gold leafelectroscope). To use an electroscope to determine the sign of thecharge it is first slightly charged. The body to be tested is thenapplied to the point of suspension, or other charging point. If at oncefurther repelled the charge of the body is of the same sign as theslight charge first imparted to the electroscope leaves; the leaves asthey become more excited will at once diverge more. If of different signthey will at first approach as their charge is neutralized and willafterwards diverge. The gold-leaf electroscope is generally enclosed in a glass bell jar orflask. Sometimes a pair of posts rise, one on each side, to supplypoints of induction from the earth to intensify the action. (SeeElectrometer, Quadrant--Electroscope, Gold leaf, and others. ) 233 STANDARD ELECTRICAL DICTIONARY. Electroscope, Bennett's. A gold-leaf electroscope, the suspended leaves of which are contained ina glass shade or vessel of dry air. On the inside of the glass shade aretwo strips of gold leaf, which rise from the lower edge a shortdistance, being pasted to the glass, and connected to the ground. Theseact by induction to increase the sensitiveness of the instruments. Electroscope, Bohenberger's. A condensing electroscope (see Electroscope, Condensing) with a singlestrip of gold leaf suspended within the glass bell. This is at an equaldistance from the opposite poles of two dry piles (see Zamboni's DryPile) standing on end, one on each side of it. As soon as the leaf isexcited it moves toward one and away from the other pile, and the signof its electrification is shown by the direction of its motion. Electroscope, Condensing. A gold leaf electroscope, the glass bell of which is surmounted by anelectrophorous or static condenser, to the lower plate of which theleaves of gold are suspended or connected. In use the object to be tested is touched to the lower plate, and theupper plate at the same time is touched by the finger. The plates arenow separated. This reduces the capacity of the lower plate greatly andits charge acquires sufficient potential to affect the leaves, althoughthe simple touching may not have affected them at all. Electroscope, Gold Leaf. An electroscope consisting of two leaves of gold leaf hung in contactwith each other from the end of a conductor. When excited they diverge. The leaves are enclosed in a glass vessel. Fig. 160. GOLD LEAF ELECTROSCOPE. 234 STANDARD ELECTRICAL DICTIONARY. Electroscope, Pith Ball. Two pith balls suspended at opposite ends of a silk thread doubled inthe middle. When charged with like electricity they repel each other. The extent of their repulsion indicates the potential of their charge. Electrostatic Attraction and Repulsion. The attraction and repulsion of electrostatically charged bodies foreach other, shown when charged with electricity. If charged withelectricity of the same sign they repel each other. If with oppositethey attract each other. The classic attraction and subsequent repulsionof bits of straw and chaff by the excited piece of amber is a case ofelectrostatic attraction and repulsion. (See Electricity, Static--Electrostatics--Coulomb's Laws of Electrostatic Attraction andRepulsion. ) Electrostatic Induction, Coefficient of. The coefficient expressing the ratio of the charge or change of chargedeveloped in one body to the potential of the inducing body. Electrostatic Lines of Force. Lines of force assumed to exist in an electrostatic field of force, andto constitute the same. In general they correspond in action andattributes with elcctro-magnetic lines of force. They involve in almostall cases either a continuous circuit, or a termination at both ends inoppositely charged surfaces. Fig. 161. ELECTROSTATIC LINES OF FORCE BETWEEN NEAR SURFACES. Fig. 162. ELECTROSTATIC LINKS OF FORCE BETWEEN DISTANT SURFACES. 235 STANDARD ELECTRICAL DICTIONARY. The cut, Fig. 161, shows the general course taken by lines of forcebetween two excited surfaces when near together. Here most of them arestraight lines reaching straight across from surface to surface, while afew of them arch across from near the edges, tending to spread. If thebodies are drawn apart the spreading tendency increases and thecondition of things shown in the next cut, Fig. 162, obtains. There isan axial line whose prolongations may be supposed to extendindefinitely, as occupying a position of unstable equilibrium. Here theexistence of a straight and unterminated line of force may be assumed. A direction is predicated to lines of force corresponding with thedirection of an electric current. They are assumed to start from apositively charged and to go towards a negatively charged surface. Apositively charged body placed in an electrostatic field of force willbe repelled from the region of positive into or towards the region ofnegative potential following the direction of the lines of force, notmoving transversely to them, and having no transverse component in itsmotion. [Transcriber's note: More precisely, "A positively charged body placedin an electrostatic field of force will be repelled from the region ofpositive into or towards the region of negative potential ACCELERATINGin the direction of the lines of force, not ACCELERATING transversely tothem, and having no transverse component in its ACCELERATION. "Previously acquired momentum can produce a transverse component ofVELOCITY. ] Electrostatics. The division of electric science treating of the phenomena of electriccharge, or of electricity in repose, as contrasted with electro-dynamicsor electricity in motion or in current form. Charges of like sign repel, and of unlike sign attract each other. The general inductive action isexplained by the use of the electrostatic field of force andelectrostatic lines of force, q. V. The force of attraction andrepulsion of small bodies or virtual points, which are near enough toeach other, vary as the square of the distance nearly, and with theproduct of the quantities of the charges of the two bodies. Electrostatic Refraction. Dr. Kerr found that certain dielectrics exposed to electric strain bybeing placed between two oppositely excited poles of a Holtz machine orother source of very high tension possess double refracting powers, inother words can rotate a beam of polarized light, or can develop twocomplimentary beams from common light. Bisulphide of carbon shows thephenomenon well, acting as glass would if the glass were stretched inthe direction of the electrostatic lines of force. To try it with glass, holes are drilled in a plate and wires from an influence machine areinserted therein. The discharge being maintained through the glass itpolarizes light. Synonym--Kerr Effect. Electrostatic Series. A table of substances arranged in the order in which they areelectrostatically charged by contact, generally by rubbing against eachother. The following series is due to Faraday. The first members becomepositively excited when rubbed with any of the following members, andvice versa. The first elements correspond to the carbon plate in agalvanic battery, the succeeding elements to the zinc plate. Cat, and Bear-skin--Flannel--Ivory--Feathers--Rock Crystal--FlintGlass--Cotton--Linen--Canvas--White Silk--the Hand--Wood--Shellac--theMetals (Iron-Copper-Brass-Tin-Silver-Platinum)--Sulphur. There are someirregularities. A feather lightly drawn over canvas is negativelyelectrified; if drawn through folds pressed against it it is positivelyexcited. Many other exceptions exist, so that the table is of littlevalue. 236 STANDARD ELECTRICAL DICTIONARY. Electrostatic Stress. The stress produced upon a transparent medium in an electrostatic fieldof force by which it acquires double refracting or polarizing propertiesas regards the action of such medium upon light. (See ElectrostaticRefraction. ) Electro-therapeutics or Therapy. The science treating of the effects of electricity upon the animalsystem in the treatment and diagnosis of disease. Electrotonus. An altered condition of functional activity occurring in a nervesubjected to the passage of an electric current. If the activity isdecreased, which occurs near the anode, the state is one ofanelectrotonus, if the activity is increased which occurs near thekathode the condition is one of kathelectrotonus. Electrotype. The reproduction of a form of type or of an engraving or of the like byelectroplating, for printing purposes. The form of type is pressed upona surface of wax contained in a shallow box. The wax is mixed withplumbago, and if necessary some more is dusted and brushed over itssurface and some iron dust is sprinkled over it also. A matrix orimpression of the type is thus obtained, on which copper is deposited byelectroplating, q. V. Element, Chemical. The original forms of matter that cannot be separated into constituentsby any known process. They are about seventy in number. Some of therarer ones are being added to or cancelled with the progress of chemicaldiscovery. For their electric relations see Electro-chemicalEquivalents--Electro-chemical Series. The elements in entering into combination satisfy chemical affinity andliberate energy, which may take the form of electric energy as in thegalvanic battery, or of heat energy, as in the combustion of carbon ormagnesium. Therefore an uncombined element is the seat of potentialenergy. (See Energy, Potential. ) In combining the elements alwayscombine in definite proportions. A series of numbers, one being properto each element which denote the smallest common multipliers of theseproportions, are called equivalents. Taking the theory of valency intoconsideration the product of the equivalents by the valencies gives theatomic weights. 237 STANDARD ELECTRICAL DICTIONARY. Element, Mathematical. A very small part of anything, corresponding in a general way to adifferential, as the element of a current. Element of a Battery Cell. The plates in a galvanic couple are termed elements, as the carbon andzinc plates in a Bunsen cell. The plate unattacked by the solution, asthe carbon plate in the above battery, is termed the negative plate orelement; the one attacked, as the zinc plate, is termed the positiveplate or element. Synonym--Voltaic Element. Elements, Electrical Classification of. This may refer to Electro-chemical Series, Electrostatic Series, orThermo-electric Series, all of which may be referred to. Element, Thermo-electric. One of the metals or other conductors making a thermo-electric couple, the heating of whose junction produces electro-motive force and acurrent, if on closed circuit. The elements of a couple are respectivelypositive and negative, and most conductors can be arranged in a seriesaccording to their relative polarity. (See Thermo-electric Series. ) Elongation. The throw of the magnetic needle. (See Throw. ) Synonym--Throw. Embosser, Telegraph. A telegraphic receiver giving raised characters on a piece of paper. Itgenerally refers to an apparatus of the old Morse receiver type, oneusing a dry point stylus, which pressing the paper into a groove in theroller above the paper, gave raised characters in dots and lines. Fig. 163. MORSE RECEIVER. 238 STANDARD ELECTRICAL DICTIONARY. E. M. D. P. Abbreviation for "electro-motive difference of potential" or forelectro-motive force producing a current as distinguished from mereinert potential difference. E. M. F. Abbreviation for "electro-motive force. " Fig. 164. END-ON METHOD. End-on Method. A method of determining the magnetic moment of a magnet. The magnetunder examination, N S, is placed at right angles to the magneticmeridian, M O R, and pointing directly at or "end on" to the centre of acompass needle, n s. From the deflection a of the latter the moment iscalculated. Endosmose, Electric. The inflowing current of electric osmose. (See Osmose, Electric. ) End Play. The power to move horizontally in its bearings sometimes given toarmature shafts. This secures a more even wearing of the commutatorfaces. End play is not permissible in disc armatures, as the attractionof the field upon the face of the armature core would displace itendwise. For such armatures thrust-bearings preventing end play have tobe provided. Energy. The capacity for doing work. It is measured by work units which involvethe exercise of force along a path of some length. A foot-pound, centimeter-gram, and centimeter-dyne are units of energy and work. The absolute unit of energy is the erg, a force of one dyne exercisedover one centimeter of space. (See Dyne. ) The dimensions of energy are force (M * L / T^2) * space (L) = M * (L^2 / T^2). Energy may be chemical (atomic or molecular), mechanical, electrical, thermal, physical, potential, kinetic, or actual, and otherdivisions could be formulated. 239 STANDARD ELECTRICAL DICTIONARY. Energy, Atomic. The potential energy due to atomic relations set free by atomic change;a form of chemical energy, because chemistry refers to molecular as wellas to atomic changes. When atomic energy loses the potential form itimmediately manifests itself in some other form, such as heat orelectric energy. It may be considered as always being potential energy. (See Energy, Chemical. ) [Transcriber's note: This item refers to chemical energy, that ismanifest in work done by electric forces during re-arrangement ofelectrons. Atomic energy now refers to re-arrangement of nucleons(protons and neutrons) and the resulting conversion of mass intoenergy. ] Energy, Chemical. A form of potential energy (see Energy, Potential) possessed by elementsin virtue of their power of combining with liberation of energy, as inthe combination of carbon with oxygen in a furnace; or by compounds invirtue of their power of entering into other combinations moresatisfying to the affinities of their respective elements or to theirown molecular affinity. Thus in a galvanic couple water is decomposedwith absorption of energy, but its oxygen combines with zinc withevolution of greater amount of energy, so that in a voltaic couple thenet result is the setting free of chemical energy, which is at onceconverted into electrical energy in current form, if the battery is on aclosed circuit. Energy, Conservation of. A doctrine accepted as true that the sum of energy in the universe isfixed and invariable. This precludes the possibility of perpetualmotion. Energy may be unavailable to man, and in the universe theavailable energy is continually decreasing, but the total energy is thesame and never changes. [Transcriber's note: If mass is counted a energy (E=m*(c^2)) then energyis strictly conserved. ] Energy, Degradation of. The reduction of energy to forms in which it cannot be utilized by man. It involves the reduction of potential energy to kinetic energy, and thereduction of kinetic energy of different degrees to energy of the samedegree. Thus when the whole universe shall have attained the sametemperature its energy will have become degraded or non-available. Atpresent in the sun we have a source of kinetic energy of high degree, incoal a source of potential energy. The burning of all the coal will bean example of the reduction of potential to kinetic energy, and thecooling of the sun will illustrate the lowering in degree of kineticenergy. (See Energy, Conservation of--Energy, Potential--Energy, Kinetic. ) Energy, Electric. The capacity for doing work possessed by electricityunder proper conditions. Electric energy may be either kinetic orpotential. As ordinary mechanical energy is a product of force andspace, so electric energy is a product of potential difference andquantity. Thus a given number of coulombs of electricity in falling agiven number of volts develop electric energy. The dimensions are foundtherefore by multiplying electric current intensity quantity ((M^. 5) * (L^. 5)), by electric potential ((M^. 5)*(L^1. 5) / (T^2)), giving (M * (L^2)/(T^2)), the dimensions of energy in general as it should be. The absolute unit of electric energy in electro-magnetic measure is(1E-7) volt coulombs. 240 STANDARD ELECTRICAL DICTIONARY. The practical unit is the volt-coulomb. As the volt is equal to 1E8absolute units of potential and the coulomb to 0. 1 absolute units ofquantity, the volt-coulomb is equal to 1E7 absolute units of energy. The volt-coulomb is very seldom used, and the unit of Electric Activityor Power (see Power, Electric), the volt-ampere, is universally used. This unit is sometimes called the Watt, q. V. , and it indicates the rateof expenditure or of production of electric energy. The storing up in a static accumulator or condenser of a given charge ofelectricity, available for use with a given change of potentialrepresents potential electric energy. The passing of a given quantity through a conductor with a given fall ofpotential represents kinetic electric energy. In a secondary battery there is no storage of energy, but the chargingcurrent simply accumulates potential chemical energy in the battery, which chemical energy is converted into electric energy in the dischargeor delivery of the battery. It is customary to discuss Ohm's law in this connection; it is properlytreated under Electric Power, to which the reader is referred. (SeePower, Electric. ) [Transcriber's note: A volt-ampere or watt is a unit of power. Avolt-coulomb second or watt-second is a unit of energy. Power multipliedby time yields energy. ] Energy, Electric Transmission of. If an electric current passes through a conductor all its energy isexpended in the full circuit. Part of the circuit may be an electricalgenerator that supplies energy as fast as expended. Part of the circuitmay be a motor which absorbs part of the energy, the rest being expendedin forcing a current through the connecting wires and through thegenerator. The electric energy in the generator and connecting wires isuselessly expended by conversion into heat. That in the motor in greatpart is utilized by conversion into mechanical energy which can douseful work. This represents the transmission of energy. Every electriccurrent system represents this operation, but the term is usuallyrestricted to the transmission of comparatively large quantities ofenergy. A typical installation might be represented thus. At a waterfall aturbine water wheel is established which drives a dynamo. From thedynamo wires are carried to a distant factory, where a motor or severalmotors are established, which receive current from the dynamo and drivethe machinery. The same current, if there is enough energy, may be usedfor running lamps or electroplating. As electric energy (see Energy, Electric, ) is measured by the product of potential difference byquantity, a very small wire will suffice for the transmission of a smallcurrent at a high potential, giving a comparatively large quantity ofenergy. It is calculated that the energy of Niagara Falls could betransmitted through a circuit of iron telegraph wire a distance of over1, 000 miles, but a potential difference of 135, 000, 000 volts would berequired, something quite impossible to obtain or manage. [Transcriber's note: Contemporary long distance power transmission linesuse 115, 000 to 1, 200, 000 volts. At higher voltages corona discharges(arcing) create unacceptable losses. ] 241 STANDARD ELECTRICAL DICTIONARY. Energy, Kinetic. Energy due to matter being actually in motion. It is sometimes calledactual energy. The energy varies directly with the mass and with thesquare of the velocity. It is represented in formula by . 5 *M * (v^2). Synonyms--Actual Energy--Energy of Motion--Dynamic Energy. Energy, Mechanical. The energy due to mechanical change or motion, virtually the same asmolar energy. (See Energy, Molar. ) Energy, Molar. The energy of masses of matter due to movements of or positions ofmatter in masses; such as the kinetic energy of a pound or of a ton inmotion, or the potential energy of a pound at an elevation of onehundred feet. Energy, Molecular. The potential energy due to the relations of molecules and set free bytheir change in the way of combination. It is potential for the samereason that applies to atomic and chemical energy, of which latter it isoften a form, although it is often physical energy. The potential energystored up in vaporization is physical and molecular energy; thepotential energy stored up in uncombined potassium oxide and water, orcalcium oxide (quicklime) and water is molecular, and when either twosubstances are brought together kinetic, thermal or heat energy is setfree, as in slaking lime for mortar. Energy of an Electrified Body. An electrified body implies the other two elements of a condenser. It isthe seat of energy set free when discharged. (See Dielectric, Energyof. ) The two oppositely charged bodies tend to approach. This tendency, together with the distances separating them, represents a potentialenergy. Energy of Stress. Potential energy due to stress, as the stretching of a spring. This ishardly a form of potential energy. A stressed spring is merely in aposition to do work at the expense of its own thermal or kinetic energybecause it is cooled in doing work. If it possessed true potentialenergy of stress it would not be so cooled. Energy of Position. Potential energy due to position, as the potential energy of a poundweight raised ten feet (ten foot lbs. ). (See Energy, Potential. ) Energy, Physical. The potential energy stored up in physical position or set free inphysical change. Thus a vapor or gas absorbs energy in its vaporization, which is potential energy, and appears as heat energy when the vaporliquefies. 242 STANDARD ELECTRICAL DICTIONARY. Energy, Potential, or Static Energy. The capacity for doing work in a system due to advantage of position orother cause, such as the stress of a spring. A pound weight supportedten feet above a plane has ten foot lbs. Of potential energy of positionreferred to that plane. A given weight of an elementary substancerepresents potential chemical energy, which will be liberated as actualenergy in its combination with some other element for which it has anaffinity. Thus a ton of coal represents a quantity of potential chemicalenergy which appears in the kinetic form of thermal energy when the coalis burning in a furnace. A charged Leyden jar represents a source ofpotential electric energy, which becomes kinetic heat energy as the sameis discharged. Energy, Thermal. A form of kinetic molecular energy due to the molecular motion of bodiescaused by heat. Entropy. Non-available energy. As energy may in some way or other be generallyreduced to heat, it will be found that the equalizing of temperature, actual and potential, in a system, while it leaves the total energyunchanged, makes it all unavailable, because all work represents a fallin degree of energy or a fall in temperature. But in a system such asdescribed no such fall could occur, therefore no work could be done. Theuniverse is obviously tending in that direction. On the earth theexhaustion of coal is in the direction of degradation of its highpotential energy, so that the entropy of the universe tends to zero. (See Energy, Degradation of. ) [Transcriber's note: Entropy (disorder) INCREASES, while AVAILABLEENERGY tends to zero. ] Entropy, Electric. Clerk Maxwell thought it possible to recognize in the Peltier effect, q. V. , a change in entropy, a gain or loss according to whether thethermo-electric junction was heated or cooled. This is termed ElectricEntropy. (See Energy, Degradation of. ) 243 STANDARD ELECTRICAL DICTIONARY. Fig. 165. EPINUS' CONDENSER, Epinus' Condenser. Two circular brass plates, A and B, are mounted on insulating supports, and arranged to be moved towards or away from each other as desired. Between them is a plate of glass, C, or other dielectric. Pith balls maybe suspended back of each brass plate as shown. The apparatus is chargedby connecting one plate to an electric machine and the other to theearth. The capacity of the plate connected to the machine is increasedby bringing near to it the grounded plate, by virtue of the principle ofbound charges. This apparatus is used to illustrate the principles ofthe electric condenser. It was invented after the Leyden jar wasinvented. Fig. 166. EPINUS' CONDENSER. E. P. S. Initials of Electrical Power Storage; applied to a type of secondarybattery made by a company bearing that title. Fig. 167. CAM EQUALIZER. 244 STANDARD ELECTRICAL DICTIONARY. Equalizer. In electro-magnetic mechanism an arrangement for converting the pull ofthe electro-magnet varying in intensity greatly over its range ofaction, into a pull of sensibly equal strength throughout. The use of arocking lever acting as a cam, with leverage varying as the armatureapproaches or recedes from the magnet core is one method of effectingthe result. Such is shown in the cut. E is an electro-magnet, witharmature a. A and B are the equalizer cams. The pull on the short end ofthe cam B is sensibly equal for its whole length. Many other methods have been devised, involving different shapes of polepieces, armatures or mechanical devices other than the one just shown. Equipotential. Adj. Equal in potential; generally applied to surfaces. Thus every magneticfield is assumed to be made up of lines of force and intersecting thoselines, surfaces, plane, or more or less curved in contour, can bedetermined, over all parts of each one of which the magnetic intensitywill be identical. Each surface is the locus of equal intensity. Thesame type of surface can be constructed for any field of force, such asan electrostatic field, and is termed an equipotential surface. Equipotential Surface, Electrostatic. A surface in an electrostatic field of force, which is the locus of allpoints of a given potential in such field; a surface cutting all thelines of force at a point of identical potential. Lines of force are cutperpendicularly by an equipotential surface, or are normal thereto. Equipotential Surface, Magnetic and Electro-magnetic. A surface bearing the same relation to a magnetic or electro-magneticfield of force that an electrostatic equipotential surface (seeEquipotential Surface, Electrostatic, ) does to an electrostatic field offorce. Equivalent, Chemical. The quotient obtained by dividing the atomic weight of an element by itsvalency. Equivalents, Electro-chemical. The weight of any substance set free by one coulomb of electricity. Thefollowing give some equivalents expressed in milligrams: Hydrogen . 0105 Mercury (mercurous) 2. 10Gold . 6877 Iron (ferric) . 1964Silver 1. 134 Iron (ferrous) . 294Copper (cupric) . 3307 Nickel . 3098Mercury (mercuric) 1. 05 Zinc . 3413Lead 1. 0868 Chlorine . 3728Oxygen . 89 245 STANDARD ELECTRICAL DICTIONARY. Equivalent, Electro-mechanical. The work or energy equivalent to unit quantities of electric energy, q. V. ; or equivalent to a unit current in a conductor whose ends differ oneunit of potential. The unit of electric energy taken is the watt-secondor volt-coulomb. One volt-coulomb is equal to Ergs 1E7 [10000000] Foot Pound . 737337 Gram-degree C. . 24068 Horse Power Second . 0013406 Pound-degree F. . 000955 One horse power is equal to 745. 943 volt coulombs per second. Equivalent, Electro-thermal. The heat produced by a unit current passing through a conductor withunit difference of potential at its ends; the heat equivalent of avolt-coulomb or watt-second. It is equal to Gram-degree C. . 24068 Pound-degree F. . 000955 Equivalent, Thermo-chemical. The calories evolved by the combination of one gram of any substancewith its equivalent of another substance being determined, the productobtained by multiplying this number by the equivalent (atomic ormolecular weight / valency) of the first element or substance is thethermo-chemical equivalent. If expressed in kilogram calories, theproduct of the thermo-chemical equivalent by 0. 43 gives the voltagerequired to effect such decomposition. The following are thermo-chemical equivalents of a few combinations: Water 34. 5 Zinc oxide 43. 2 Iron protoxide 34. 5 Iron Sesquioxide 31. 9 X 3 Copper oxide 19. 2 Equivolt. "The mechanical energy of one volt electro-motive force exerted underunit conditions through one equivalent of chemical action in grains. "(J. T. Sprague. ) This unit is not in general use as the unit of electricenergy, the volt-coulomb and (for rate of electric energy) thevolt-ampere being always used. Erg. The absolute or fundamental C. G. S. Unit of work or energy. The workdone or energy expended in moving a body through one centimeter againsta resistance of one dyne. Erg-ten. Ten millions of ergs, or ten meg-ergs. Escape. A term applied to leakage of current. Etching, Electric. A process of producing an etched plate. The plate is coated with wax, and the design traced through as in common etching. It is then placed ina bath and is connected to the positive terminal from a generator, whosenegative is immersed in the same bath, so that the metal is dissolved byelectrolytic action. By attaching to the other terminal and using aplating bath, a rough relief plate may be secured, by deposition in thelines of metal by electroplating. Synonym--Electric Engraving. 246 STANDARD ELECTRICAL DICTIONARY. Ether. The ether is a hypothetical thing that was invented to explain thephenomena of light. Light is theoretically due to transverse vibrationsof the ether. Since the days of Young the conception of the ether hasextended, and now light, "radiant heat, " and electricity are all treatedas phenomena of the ether. Electrical attraction and repulsion areexplained by considering them due to local stresses in the ether;magnetic phenomena as due to local whirlpools therein. The ether wasoriginally called the luminiferous ether, but the adjective should nowbe dropped. Its density is put at 936E-21 that of water, or equal tothat of the atmosphere at 210 miles above the earth's surface. Itsrigidity is about 1E-9 that of steel (see Ten, Powers of); as a whole itis comparable to an all-pervading jelly, with almost perfect elasticity. The most complete vacuum is filled with ether. All this is a hypothesis, for the ether has never been proved to exist. Whether gravitation will ever be explained by It remains to be seen. [Transcriber's note: The Michelson-Morley experiment in 1887 (five yearsbefore this book) cast serious doubt on the ether. In 1905 Einsteinexplained electromagnetic phenomenon with photons. In 1963 Edward M. Purcell used special relativity to derive the existence of magnetism andradiation. ] Eudiometer. A graduated glass tube for measuring the volumes of gases. In itssimplest form it is simply a cylindrical tube, with a scale etched orengraved upon it, closed at one end and open at the other. The gas to bemeasured is collected in it over a liquid, generally water, dilutesulphuric acid in the gas voltameter, or mercury. Many different shapeshave been given them by Hoffmann, Ure, Bunsen and others. Evaporation, Electric. The superficial sublimation or evaporation of a substance under theinfluence of negative electricity. It is one of the effects investigatedby Crookes in his experiments with high vacua. He found that when ametal, even so infusible as platinum, was exposed to negativeelectrification in one of his high vacuum tubes, that it was volatilizedperceptibly. A cadmium electrode heated and electrified negatively wasfound to give a strong coating of metal on the walls of the tube. Evenin the open air the evaporation of water was found to be accelerated bynegative electrification. Exchange, Telephone. The office to which telephone wires lead in a general telephone system. In the office by a multiple switch board, or other means, the differenttelephones are interconnected by the office attendants, so that anycustomers who desire it may be put into communication with each other. The exchange is often termed the Central Office, although it may be onlya branch office. Excitability, Faradic. The action produced in nerve or muscle of the animal system by analternating or intermitting high potential discharge from an inductioncoil. 247 STANDARD ELECTRICAL DICTIONARY. Excitability, Galvanic. The same as Faradic excitability, except that it refers to the effectsof the current from a galvanic battery. Excitability of Animal System, Electric. The susceptibility of a nerve or muscle to electric current shown by theeffect produced by its application. Exciter. A generator used for exciting the field magnet of a dynamo. Inalternating current dynamos, e. G. , of the Westinghouse type, a specialdynamo is used simply to excite the field magnet. In central stationdistribution the same is often done for direct current dynamos. Exosmose, Electric. The outflowing current of electric osmose. (See Osmose, Electric. ) Expansion, Coefficient of. The number expressing the proportional increase in size, either length, area or volume, of a substance under the influence generally of heat. There are three sets of coefficients, (1) of linear expansion, (2) ofsuperficial expansion, (3) of cubic expansion or expansion of volume. The first and third are the only ones much used. They vary for differentsubstances, and for the same substance at different temperatures. Theyare usually expressed as decimals indicating the mixed number referredto the length or volume of the body at the freezing point as unity. Expansion, Electric. (a) The increase in volume of a condenser, when chargedelectrostatically. A Leyden jar expands when charged, and contracts whendischarged. (b) The increase in length of a bar of iron when magnetized. This is more properly called magnetic expansion or magnetic elongation. Exploder. (a) A small magneto-generator for producing a current for heating thewire in an electric fuse of the Abel type (see Fuse, Electric), andthereby determining an explosion. (b) The term may also be applied to a small frictional or influencemachine for producing a spark for exploding a spark fuse. Explorer. A coil, similar to a magnetizing coil (see Coil, Magnetizing), used forinvestigating the electro-magnetic circuit and for similar purposes. Ifplaced around an electro-magnet and connected with a galvanometer, itwill produce a deflection, owing to a momentary induced current, uponany change in the magnet, such as removing or replacing the armature. Itis useful in determining the leakage of lines of force and for generalinvestigations of that nature. It is often called an exploring coil. Hughes' Induction Balance (see Induction Balance, Hughes') is sometimescalled a Magnetic Explorer. The exploring coil may be put in circuitwith a galvanometer for quantitative measurements or with a telephonefor qualitative ones. 248 STANDARD ELECTRICAL DICTIONARY. Extension Bell Call. A system of relay connection, q. V. , by which a bell is made to continueringing after the current has ceased coming over the main line. It isdesigned to prolong the alarm given by a magneto call bell, q. V. , whichlatter only rings as long as the magneto handle is turned. A vibratingelectric bell (see Bell, Electric, ) is connected in circuit with a localbattery and a switch normally open, but so constructed as to close thecircuit when a current is passed and continue to do so indefinitely. Thedistant circuit is connected to this switch. When the magneto is workedit acts upon the switch, closes the local battery circuit and leaves itclosed, while the bell goes on ringing until the battery is exhausted orthe switch is opened by hand. Eye, Electro-magnetic. An apparatus used in exploring a field of electro-magnetic radiations. It is a piece of copper wire 2 millimeters (. 08 inch) in diameter, bentinto an almost complete circle 70 millimeters (. 28 inch) in diameter, with terminals separated by an air gap. This is moved about in theregion under examination, and by the production of a spark indicates thelocality of the loops or venters in systems of stationary waves. F. Abbreviation for Fahrenheit, as 10º F. , meaning 10º Fahrenheit. (SeeFahrenheit Scale. ) Fahrenheit Scale. A thermometer scale in use in the United States and England. On thisscale the temperature of melting ice is 32°; that of condensing steam is212°; the degrees are all of equal length. Its use is indicated by theletter F. , as 180° F. To convert its readings into centigrade, subtract32 and multiply by 5/9. (b) To convert centigrade into F. Multiply by9/5 and add 32. Thus 180° F. = ((180-32) * 5/9)° C. = 82. 2° C. Again180° C. = (180 * 9/5) + 32 = 324° F. [Transcribers note: 180° C. = (180 * 9/5) + 32 = 356° F. ] The additions and subtractions must be algebraic in all cases. Thus whenthe degrees are minus or below zero the rules for conversion might beput thus: To convert degrees F. Below zero into centigrade to the numberof degrees F. Add 32, multiply by 5/9 and place a minus sign (-) beforeit. (b) To convert degrees centigrade below zero into Fahrenheit, multiply the number of degrees by 9/5, subtract from 32 if smaller; ifgreater than 32 subtract 32 therefrom, and prefix a minus sign, thus:-10° C. = 32 - (10 * 9/5) = 14°. Again, -30°C. = (30 * 9/5) - 32 = 22 =-22° F. 249 STANDARD ELECTRICAL DICTIONARY. Farad. The practical unit of electric capacity; the capacity of a conductorwhich can retain one coulomb of electricity at a potential of one volt. The quantity of electricity charged upon a conducting surface raises itspotential; therefore a conductor of one farad capacity can hold twocoulombs at two volts potential, and three coulombs at three volts, andso on. The electric capacity of a conductor, therefore, is relativecompared to others as regards its charge, for the latter may be as greatas compatible with absence of sparking and disruptive discharge. Inother words, a one farad or two farad conductor may hold a great manycoulombs. Charging a conductor with electricity is comparable to pumpingair into a receiver. Such a vessel may hold one cubic foot of air atatmospheric pressure and two at two atmospheres, and yet be of one cubicfoot capacity however much air is pumped into it. The farad is equal to one fundamental electrostatic unit of capacitymultiplied by 9E11 and to one electro-magnetic unit multiplied by 1E-9. The farad although one of the practical units is far too large, so themicro-farad is used in its place. The capacity of a sphere the size ofthe earth is only . 000636 of a farad. [Transcriber's note: Contemporary calculations give about . 000720farad. ] Faraday, Effect. The effect of rotation of its plane produced upon a polarized beam oflight by passage through a magnetic field. (See Magnetic RotaryPolarization. ) Faraday's Cube. To determine the surface action of a charge, Faraday constructed a room, twelve feet cube, insulated, and lined with tinfoil. This room hecharged to a high potential, but within it he could detect no excitementwhatever. The reason was because the electricity induced in the bodieswithin the room was exactly equal to the charge of the room-surface, andwas bound exactly by it. The room is termed Faraday's cube. Faraday's Dark Space. A non-luminous space between the negative and positive glows, producedin an incompletely exhausted tube through which a static discharge, asfrom an induction coil, is produced. It is perceptible in a rarefactionof 6 millimeters (. 24 inch) and upwards. If the exhaustion is very higha dark space appears between the negative electrode and its discharge. This is known as Crookes' dark space. Faraday's Disc. A disc of any metal, mounted so as to be susceptible of rotation in amagnetic field of force, with its axis parallel to the general directionof the lines of force. A spring bears against its periphery and anotherspring against its axle. When rotated, if the springs are connected by aconductor, a current is established through the circuit including thedisc and conductor. The radius of the disc between the spring contactsrepresents a conductor cutting lines of force and generating a potentialdifference, producing a current. If a current is sent through themotionless wheel from centre to periphery it rotates, illustrating thedoctrine of reversibility. As a motor it is called Barlow's orSturgeon's Wheel. If the disc without connections is rapidly rotated itproduces Foucault currents, q. V. , within its mass, which resist itsrotation and heat the disc. 250 STANDARD ELECTRICAL DICTIONARY. Fig. 168. "FARADAY'S NET. " Faraday's Net. An apparatus for showing that the electric charge resides on thesurface. It consists of a net, conical in shape and rather deep, towhose apex two threads, one on each side, are attached. Its mouth isfastened to a vertical ring and the whole is mounted on an insulatingsupport. It is pulled out to its full extent and is electrified. No charge can bedetected inside it. By pulling one of the threads it is turned with theother side out. Now all the charge is found on the outside just asbefore, except that it is of course on the former inside surface of thebag. The interior shows no charge. Faraday's Transformer. The first transformer. It was made by Michael Faraday. It was a ring ofsoft iron 7/8 inch thick, and 6 inches in external diameter. It waswound with bare wire, calico being used to prevent contact of the wirewith the ring and of the layers of wire with each other, while twine waswound between the convolutions to prevent the wires from touching. Seventy-two feet of copper wire, 1/20 inch diameter, were wound in threesuperimposed coils, covering about one-half of the ring. On the otherhalf sixty feet of copper wire were wound in two superimposed coils. Faraday connected his coils in different ways and used a galvanometer tomeasure the current produced by making and breaking one of the circuitsused as a primary. The coil is of historic interest. Faraday's Voltameter. A voltameter, in which the coulombs of current are measured by thevolume of the gas evolved from acidulated water. (See Voltameter, Gas. ) Faradic. Adj. Referring to induced currents, produced from induction coils. As Faradaywas the original investigator of the phenomena of electro-magneticinduction, the secondary or induced electro-magnetic currents and theirphenomena and apparatus are often qualified by the adjective Faradic, especially in electro-therapeutics. A series of alternatingelectrostatic discharges, as from an influence machine (Holtz), aresometimes called Franklinic currents. They are virtually Faradic, exceptas regards their production. 251 STANDARD ELECTRICAL DICTIONARY. Faradic Brush. A brush for application of electricity to the person. It is connected asone of the electrodes of an induction coil or magneto generator. Forbristles wire of nickel plated copper is generally employed. Faradization. In medical electricity the analogue of galvanization; the effects due tosecondary or induced currents; galvanization referring to currents froma galvanic battery; also the process of application of such currents. Faults. Sources of loss of current or of increased resistance or other troublesin electric circuits. Feeder. A lead in an electric central station distribution system, which leadruns from the station to some point in the district to supply current. It is not used for any side connections, but runs direct to the pointwhere current is required, thus "feeding" the district directly. In thetwo wire system a feeder may be positive or negative; in the three wiresystem there is also a neutral feeder. Often the term feeder includesthe group of two or of three parallel lines. Feeder Equalizer. An adjustable resistance connected in circuit with a feeder at thecentral station. The object of the feeder being to maintain a definitepotential difference at its termination, the resistance has to be variedaccording to the current it is called on to carry. Feeder, Main or Standard. The main feeder of a district. The standard regulation of pressure(potential difference between leads) in the district is often determinedby the pressure at the end of the feeder. Feeder, Negative. The lead or wire in a set of feeders, which is connected to the negativeterminal of the generator. Feeder, Neutral. In the three wire system the neutral wire in a set of feeders. It isoften made of less diameter than the positive and negative leads. Feeder, Positive. The lead or wire in a set of feeders, which wire is connected to thepositive terminal of the generator. Ferranti Effect. An effect as yet not definitely explained, observed in the mains of theDeptford, Eng. , alternating current plant. It is observed that thepotential difference between the members of a pair of mains rises orincreases with the distance the place of trial is from the station. [Transcriber's note: This effect is due to the voltage drop across theline inductance (due to charging current) being in phase with thesending end voltages. Both capacitance and inductance are responsiblefor producing this phenomenon. The effect is more pronounced inunderground cables and with very light loads. ] 252 STANDARD ELECTRICAL DICTIONARY. Ferro-magnetic. Adj. Paramagnetic; possessing the magnetic polarity of iron. Fibre and Spring Suspension. A suspension of the galvanometer needle used in marine galvanometers. The needle is supported at its centre of gravity by a verticallystretched fibre attached at both its ends, but with a springintercalated between the needle and one section of the fibre. Fibre Suspension. Suspension, as of a galvanometer needle, by a vertical or hanging fibreof silk or cocoon fibre, or a quartz fibre. (See Quartz. ) This suspension, while the most delicate and reliable known, is verysubject to disturbance and exacts accurate levelling of the instrument. Fibre suspension is always characterized by a restitutive force. Pivotsuspension, q. V. , on the other hand, has no such force. Field, Air. A field the lines of force of which pass through air; the position of afield comprised within a volume of air. Field, Alternating. Polarity or direction being attributed to lines of force, if suchpolarity is rapidly reversed, an alternating field results. Such fieldmay be of any kind, electro-magnetic or electrostatic. In one instancethe latter is of interest. It is supposed to be produced by highfrequency discharges of the secondary of an induction coil, existing inthe vicinity of the discharging terminals. Field Density. Field density or density of field is expressed in lines of force perunit area of cross-section perpendicular to the lines of force. Field, Distortion of. The lines of force reaching from pole to pole of an excited field magnetof a dynamo are normally symmetrical with respect to some axis and oftenwith respect to several. They go across from pole to pole, sometimesbent out of their course by the armature core, but still symmetrical. The presence of a mass of iron in the space between the pole piecesconcentrates the lines of force, but does not destroy the symmetry ofthe field. When the armature of the dynamo is rotated the field becomes distorted, and the lines of force are bent out of their natural shape. The newdirections of the lines of force are a resultant of the lines of forceof the armature proper and of the field magnet. For when the dynamo isstarted the armature itself becomes a magnet, and plays its part informing the field. Owing to the lead of the brushes the polarity of thearmature is not symmetrical with that of the field magnets. Hence thecompound field shows distortion. In the cut is shown diagrammaticallythe distortion of field in a dynamo with a ring armature. The arrowdenotes the direction of rotation, and n n * * * and s s * * * indicatepoints of north and south polarity respectively. 253 STANDARD ELECTRICAL DICTIONARY. The distorted lines must be regarded as resultants of the two inducedpolarities of the armature, one polarity due to the induction of thefield, the other to the induction from its own windings. The positionsof the brushes have much to do with determining the amount and degree ofdistortion. In the case of the ring armature it will be seen that someof the lines of force within the armature persist in their polarity anddirection, almost as induced by the armature windings alone, and leakacross without contributing their quota to the field. Two such lines areshown in dotted lines. In motors there is a similar but a reversed distortion. Fig. 169. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE DYNAMO. Fig. 170. DISTORTION OF FIELD IN A RING ARMATURE OF AN ACTIVE MOTOR. 254 STANDARD ELECTRICAL DICTIONARY. Field, Drag of. When a conductor is moved through a field so that a current is generatedin it, the field due to that current blends with the other field andwith its lines of force, distorting the field, thereby producing a dragupon its own motion, because lines of force always tend to straightenthemselves, and the straightening would represent cessation of motion inthe conductor. This tendency to straightening therefore resists themotion of the conductor and acts a drag upon it. Field of Force. The space in the neighborhood of an attracting or repelling mass orsystem. Of electric fields of force there are two kinds, theElectrostatic and the Magnetic Fields of Force, both of which may bereferred to. A field of force may be laid out as a collection ofelements termed Lines of Force, and this nomenclature is universallyadopted in electricity. The system of lines may be so constructed that(a) the work done in passing from one equipotential surface to the nextis always the same; or (b) the lines of force are so laid out anddistributed that at a place in which unit force is exercised there is asingle line of force passing through the corresponding equipotentialsurface in each unit of area of that surface. The latter is theuniversal method in describing electric fields. It secures the followingadvantages:--First: The potential at any point in the field of spacesurrounding the attracting or repelling mass or masses is found bydetermining on which imaginary equipotential surface that point lies. Second: If unit length of a line of force cross n equipotentialsurfaces, the mean force along that line along the course of that partof it is equal to n units; for the difference of potential of the twoends of that part of the line of force = n; it is also equal to F s (F= force), because it represents numerically a certain amount of work;but s = I, whence n = F. Third: The force at any part of the fieldcorresponds to the extent to which the lines of force are crowdedtogether; and thence it may be determined by the number of lines offorce which pass through a unit of area of the correspondingequipotential surface, that area being so chosen as to comprise thepoint in question. (Daniell. ) Field of Force, Electrostatic. The field established by the attracting, repelling and stressinginfluence of an electrostatically charged body. It is often termed anElectrostatic Field. (See Field of Force. ) 255 STANDARD ELECTRICAL DICTIONARY. Field of Force of a Current. A current establishes a field of force around itself, whose lines offorce form circles with their centres on the axis of the current. Thecut, Fig. 172, shows the relation of lines of force to current. Fig. 171. EXPERIMENT SHOWING LINES OF FORCESURROUNDING AN ACTIVE CONDUCTOR. Fig. 172. DIAGRAM OF FIELD OF FORCE SURROUNDING AN ACTIVE CONDUCTOR. Fig. 173. LINK OF FORCE INDUCED BY A CURRENT SHOWING THE MAGNETIC WHIRLS. The existence of the field is easily shown by passing a conductorvertically through a horizontal card. On causing a current to go throughthe wire the field is formed, and iron filings dropped upon the card, tend, when the latter is gently tapped, to take the form of circles. Theexperiment gives a version of the well-known magnetic figures, q. V. SeeFig. 171. The cut shows by the arrows the relation of directions of current to thedirection of the lines of force, both being assumptions, and merelyindicating certain fixed relations, corresponding exactly to therelations expressed by the directions of electro-magnetic or magneticlines of force 256 STANDARD ELECTRICAL DICTIONARY. Field, Pulsatory. A field produced by pulsatory currents. By induction such field canproduce an alternating current. Field, Rotating. In a dynamo the field magnets are sometimes rotated instead of thearmature, the latter being stationary. In Mordey's alternator thearmature, nearly cylindrical, surrounds the field, and the latterrotates within it, the arrangement being nearly the exact reverse of theordinary one. This produces a rotating field. Field, Rotatory. A magnetic field whose virtual poles keep rotating around its centre offigure. If two alternating currents differing one quarter period inphase are carried around four magnetizing coils placed and connected insets of two on the same diameter and at right angles to each other, thepolarity of the system will be a resultant of the combination of theirpolarity, and the resultant poles will travel round and round in acircle. In such a field, owing to eddy currents, masses of metal, journaled like an armature, will rotate, with the speed of rotation ofthe field. Field, Stray. The portion of a field of force outside of the regular circuit;especially applied to the magnetic field of force of dynamos expressingthe portion which contributes nothing to the current generation. Synonym--Waste Field. Field, Uniform. A field of force of uniform density. (See Field Density. ) Figure of Merit. In the case of a galvanometer, a coefficient expressing its delicacy. Itis the reciprocal of the current required to deflect the needle throughone degree. By using the reciprocal the smaller the current required thelarger is the figure of merit. The same term may be applied to otherinstruments. It is often defined as the resistance of a circuit through which oneDaniell's element will produce a deflection of one degree on the scaleof the instrument. The circuit includes a Daniell's cell of resistancer, a rheostat R, galvanometer G and shunt S. Assume that with the shuntin parallel a deflection of a divisions is obtained. The resistance ofthe shunted galvanometer is (GS/G+S ; the multiplying power m of theshunt is S+G/S; the formula or figure of merit is m d (r+R +G S/G+S). The figure of merit is larger as the instrument is more sensitive. Synonym--Formula of Merit. 257 STANDARD ELECTRICAL DICTIONARY. Filament. A thin long piece of a solid substance. In general it is so thin as toact almost like a thread, to be capable of standing considerableflexure. The distinction between filament and rod has been of muchimportance in some patent cases concerning incandescent lamps. As usedby electricians the term generally applies to the carbon filament ofincandescent lamps. This as now made has not necessarily any fibres, butis entitled to the name of filament, partly by convention, partly by itsrelative thinness and want of stiffness. (See IncandescentLamps--Magnetic Filament. ) Fire Alarm, Electric, Automatic. A system of telegraph circuits, at intervals supplied with thermostatsor other apparatus affected by a change of temperature, which on beingheated closes the circuit and causes a bell to ring. (See Thermostat. ) Fire Alarm Telegraph System. A system of telegraphic lines for communicating the approximate locationof a fire to a central station and thence to the separate fire-enginehouses in a city or district. It includes alarm boxes, distributed atfrequent intervals, locked, with the place where the key is keptdesignated, or in some systems left unlocked. On opening the door of thebox and pulling the handle or otherwise operating the alarm, adesignated signal is sent to the central station. From this it istelegraphed by apparatus worked by the central station operator to theengine houses. The engines respond according to the discipline of theservice. Fire Cleansing. Freeing the surface of an article to be plated from grease by heating. Fire Extinguisher, Electric, Automatic. A modification of the electric fire alarm (see Fire Alarm, Electric, Automatic), in which the thermostats completing the circuits turn onwater which, escaping through the building, is supposed to reach andextinguish a fire. Flashing in a Dynamo or Magneto-electric Generator. Bad adjustment of the brushes at the commutator, or other fault ofconstruction causes the production of voltaic arcs at the commutator ofa generator, to which the term flashing is applied. Flashing of Incandescent Lamp Carbons. A process of treatment for the filaments of incandescent lamps. Thechamber before sealing up is filled with a hydro-carbon vapor or gas, such as the vapor of a very light naphtha (rhigolene). A current is thenpassed through the filament heating it to redness. The more attenuatedparts or those of highest resistance are heated the highest, anddecompose most rapidly the hydro-carbon vapor, graphitic carbon beingdeposited upon these parts, while hydrogen is set free. This goes onuntil the filament is of uniform resistance throughout. It gives also away of making the resistance of the filament equal to any desired numberof ohms, provided it is originally of high enough resistance. Theprocess increases the conductivity of the filament. After flashing the chambers are pumped out and sealed up. 258 STANDARD ELECTRICAL DICTIONARY. Flashing Over. A phenomenon observed in high potential dynamos. On a sudden alterationof the resistance of the circuit a long blue spark will be drawn outaround the surface of the commutator from brush to brush. The spark issomewhat of the nature of an arc, and may seriously injure commutatorswhose sections are only separated by mica, or other thin insulation. Inthe case of commutators whose sections are separated by air spaces it isnot so injurious. Flats. In a commutator of a dynamo, the burning or wearing away of a commutatorsegment to a lower level than the rest. Sometimes two adjacent bars willbe thus affected, causing a flat place on the commutator. It is notalways easy to account for the formation of flats. They may have theirorigin in periodic vibrations due to bad mounting, or to sparking at theparticular point. Floor Push. A press or push button constructed to be set into the floor to beoperated by pressing with the foot. It is used to ring an alarm bell, sound a buzzer or for similar service. Fluid, Depolarizing. A fluid used in voltaic batteries to dispose of the hydrogen, which goesto the negative plate. This it does by oxidizing it. Chromic acid, nitric acid, and chloric acids are among the constituents of liquiddepolarizers. (See Electropoion Fluid. ) Fluid, Electric. The electric current and charge have sometimes been attributed to afluid. The theory, which never was much more than hypothetical, survivesto some extent in the single and double fluid theory. (See Single FluidTheory-Double Fluid Theory. ) Fluorescence. The property of converting ether waves of one length, sometimes ofinvisible length, into waves of another length (visible). AEsculin, quinine salts, uranium glass and other substances exhibit thisphenomenon. The phenomenon is utilized in the production of Geisslertubes. Flush Boxes. A heavy iron box covered with a heavy hand plate and laid flush (whencethe name), or even with the surface of a roadway. Into it conductors ofan underground system lead, and it is used to make connections therewithand for examining the leakage of the conductors and for similarpurposes. It is a "man-hole" (q. V. ) in miniature. Fluviograph. An electric registering tide gauge or water level gauge. 259 STANDARD ELECTRICAL DICTIONARY. Fly or Flyer, Electric. A little wheel, ordinarily poised on a point, like a compass needle. Itcarries several tangentially directed points, all pointing in the samesense. When connected with a source of electricity of high potential itrevolves by reaction. The tension of its charge is highest at thepoints, the air there is highly electrified and repelled, the reactionpushing the wheel around like a Barker's mill or Hero's steam engine. Sometimes the flyer is mounted with its axis horizontal and across therails on a railroad along which it travels. Synonym--Reaction Wheel. Foci Magnetic. The two points on the earth's surface where the magnetic intensity isgreatest. They nearly coincide in position with the magnetic poles. Fog, Electric. Fogs occurring when the atmosphere is at unusually high potential andaccompanied by frequent change of such polarity. Following Horns. In dynamo-electric machines the projecting ends of the pole piecestowards which the outer uncovered perimeter of the armature turns in itsregular operations. The leading horns are those away from which thearmature rotates. In considering rotation the exposed portion of thesuperficies of the armature is considered. The definition would have tobe reversed if the part facing the pole pieces were considered. Synonym--Trailing Horns. Foot-candle. A unit of illuminating power; the light given by one standard candle ata distance of one foot. The ordinary units of illuminating power areentirely relative; this is definite. It is due to Carl Herring. Foot-pound. A practical unit of work or energy. The quantity of work required toraise a pound one foot, or one hundred pounds one-hundredth of a foot, and so on; or the potential energy represented by a weight at anelevation under these conditions. Foot-step. In a dynamo with armature at the lower end of its field magnets, theplate generally of zinc, interposed between it and the iron base plateto prevent the leakage of lines of force outside of the circuit. Anydiamagnetic material which is mechanically suitable may be used. Force. Force may be variously defined. (a) Any cause of change of the condition of matter with respect tomotion or rest. (b) A measurable action upon a body under which the state of rest ofthat body, or its state of uniform motion in a straight line, sufferschange. (c) It may be defined by its measurement as the rate of change ofmomentum, or (d) as the rate at which work is done per unit of space traversed. Force is measured by the acceleration or change of motion it can impartto a body of unit mass in a unit of time, or, callingforce, F, mass, macceleration per second awe have F = m a. The dimensions of force aremass (M) * acceleration (L/(T^2)) = (M*L)/(T^2). 260 STANDARD ELECTRICAL DICTIONARY. Force de Cheval. Horse power (French). It is the French or metric horse power. It is equal to: 542. 496 Foot lbs. Per second. . 9864 English Horse Power. 75. 0 Kilogram-meters per second. Force, Electro-magnetic. The mechanical force of attraction or repulsion acting on theelectro-magnetic unit of quantity. Its intensity varies with the squareof the distance. It may also be defined as electric force in theelectro-magnetic system. Its dimensions are equal tomechanical force ((M*L)/(T^2)) divided by quantity ((M^. 5)*(L^. 5))= ((M^. 5)*(L^. 5))/(T^2). Force, Electrostatic. The force by which electric matter or electrified surfaces attract orrepel each other. It is also termed electric force (not good) andelectro-motive intensity. It is the mechanical force acting upon a unitquantity of electricity. Its intensity varies with the square of thedistance. Its dimensions are therefore equal to(quantity * unity / (square of distance) Q. * 1 / (L^2) = ((M^. 5) * (L^1. 5) )/ T*1 / (L^2) = ((M^. 5) * (L^. 5)) / TThese dimensions are also those of potential difference. [Transcriber's Note: The image of the preceding paragraph is includedfor "clarity". ] The objection to the term electric force is that it may be applied alsoto electro-magnetic force, and hence be a source of confusion. Forces, Parallelogram of. The usual method of composing forces or resolving a force. The sides ofa parallelogram of forces represent component forces and the diagonalrepresents the resultant. See Component--Resultant--Forces, Compositionof--Forces, Resolution of. Forces, Composition of. When several forces act in a different direction upon a point they maybe drawn or graphically represented as arrows or lines emanating fromthe point in the proper direction and of lengths proportional to theforce they exercise. Any two can be treated as contiguous sides of aparallelogram and the parallelogram can be completed. Then its diagonal, called the resultant, will represent the combined action of the twoforces, both as regards direction and intensity. This is the compositionof two forces. If more than two forces act upon the given point the resultant can becomposed with any of the others and a new force developed. The newresultant can be combined with another force, and the process kept up, eliminating the components one by one until a final resultant of all isobtained. This will give the exact direction and intensity of theforces, however many or varied. 261 STANDARD ELECTRICAL DICTIONARY. Forces, Resolution of. The developing from a single force treated as a resultant, two otherforces in any desired direction. The reverse of composition of forces. (See Forces, Composition of--Forces, Parallelogramof--Components--Resultant. ) Force, Tubes of. Aggregations of lines of force, either electrostatic or magnetic. Theygenerally have a truncated, conical or pyramidal shape and are nothollow. Every cross-section contains the same number of lines. The nameit will seem is not very expressive. Force, Unit of. The fundamental or C. G. S. Unit or force is the dyne, q. V. The British unit of force is the poundal (the force which will producean acceleration of one foot per second in a mass of one pound). It isequal to about 10/322 pound. A force cannot be expressed accurately inweight units, because weight varies with the latitude. Forming. The process of producing secondary battery plates from lead plates byalternately passing a charging current through the cell and thenallowing it to discharge itself and repeating the operation. (SeeBattery, Secondary, Planté's. ) Foundation Ring. In a dynamo armature the ring-shaped core on which Gramme ring armaturesand other ring armatures are wound. Fourth State of Matter. Gas so rarefied that its molecules do not collide, or rarely do so;radiant matter, q. V. [Transcriber's note: This term now refers to plasma, an ionized gas, which contains free electrons. The ions and electrons move somewhatindependently making plasma electrically conductive. It respondsstrongly to electromagnetic fields. ] Frame. In a dynamo the bed-piece is sometimes called the frame. Franklin's Experiment. Franklin proved the identity of lightning and electricity by flying akite in a thunder storm. The kite was of silk so as to endure thewetting. When the string became wet sparks could be taken from a keyattached to its end. The main string was of hemp; at the lower end was alength of silk to insulate it. The key was attached near the end of andto the hemp string. Franklin's Plate. A simple form of condenser. It consists of a plate of glass coated oneach side with tinfoil with a margin of about an inch of clear glass. One coating may be grounded as indicated in the cut, and the platecharged like a Leyden jar. Or one side may be connected with oneterminal, and the other with the other terminal of an influence machineand the pane will be thus charged. Synonym--Fulminating Pane. 262 STANDARD ELECTRICAL DICTIONARY. Fig. 174. FRANKLIN'S PLATE. Franklin's Theory. The single fluid theory, q. V. , of electricity. Frequency. The number of double reversals or complete alternations per second in analternating current. Synonym--Periodicity. Frictional Electricity. Electricity produced by friction of dissimilar substances. (SeeElectrostatic Series. ) The contact theory holds that friction plays onlya secondary rôle in this process; that it increases the thoroughness ofcontact, and tends to dry the rubbing surfaces, but that the chargesinduced are due to contact of dissimilar substances, not to friction ofone against the other. Frictional Heating. The heating of a conductor by the passage of a current; the Jouleeffect, q. V. Fringe. The outlying edge of a magnetic field. Frog, Galvani's Experiment With. A classic experiment in electricity, leading to the discovery of currentor dynamic electricity. If a pair of legs of a recently killed frog areprepared with the lumbar nerves exposed near the base of the spinalcolumn, and if a metallic conductor, one half-length zinc and the otherhalf-length copper, is held, one end between the lumbar nerves and thespine, and the other end against one of the muscles of the thigh orlower legs, the moment contact occurs and the circuit is completedthrough the animal substance the muscles contract and the leg isviolently drawn upwards. Galvani, in 1786, first performed, by accident, this famous experiment, it is said, with a scalpel with which he wasdissecting the animal. He gave his attention to the nerves and muscles. Volta, more happily, gave his attention to the metals and invented thevoltaic battery, described by him in a letter to Sir Joseph Banks, dated1800. Frog, Rheoscopic. If the nerve or living muscle of a frog is suddenly dropped upon anotherliving muscle so as to come in contact with its longitudinal andtransverse sections, the first muscle will contract on account of thestimulation of its nerve due to the passage of a current derived fromthe second muscle (Ganot). The experiment goes under the above title. 263 STANDARD ELECTRICAL DICTIONARY. Frying. A term applied to a noise sometimes produced in a voltaic arc due to tooclose approach of the carbons to each other. It has been suggested thatit may be due to volatilization of the carbon. (Elihu Thomson. ) Fulgurite. An irregular and tubular mass of vitrified quartz, believed to be formedby melting under the lightning stroke. Fig. 175. CRUCIBLE, ELECTRIC. Furnace, Electric. A furnace in which the heat is produced by the electric current. It hashitherto been practically used only in the extraction of aluminum andsilicium from their ores. The general principle involves the formationof an arc between carbon electrodes. The substances to be treated areexposed to the heat thus produced. Sometimes the substances in the arcform imperfect conductors, and incandescence takes a part in the action. Sometimes the substances are merely dropped through the arc. [Transcriber's note: Silicium is silicon. ] Fuse Board. A tablet on which a number of safety fuses are mounted. Slate isexcellent material for the tablet, as it is incombustible, and is easilydrilled and worked. Fuse Box. A box containing a safety fuse. Porcelain is an excellent material forits base. No combustible material should enter into its composition. Fuse, Cockburn. A safety fuse or cut off which consists of a wire of pure tin runningfrom terminal to terminal, to whose centre a leaden ball is secured bybeing cast into position. The connection with the terminals is made byrings at the ends of the wire through which the terminal screws arepassed and screwed home. When the tin softens under too heavy a currentthe weight of the shot pulls it apart. Fig. 176 COCKBURN SAFETY FUSE. 264 STANDARD ELECTRICAL DICTIONARY. Fig. 177. ELECTRIC FUSE. Fuse, Electric. A fuse for igniting an explosive by electricity. There are two kinds. Inone a thin wire unites the ends of the two conducting wires as theyenter the case of the fuse. The larger wires are secured to the case, sothat no strain comes on the fine wire. On passing a current ofsufficient strength the small wire is heated. In use the fuse is beddedin powder, which again may be surrounded by fulminating powder, allcontained in a copper or other metallic case. Such a detonator is usedfor exploding guncotton and other high explosives. The other kind of fuse is similar, but has no thin connecting wire. Theends of the conductors are brought nearer together without touching. Inuse a static discharge is produced across from end to end of theconductors, igniting a proper explosive placed there as in the othercase. The first kind of fuse is generally operated by a battery or smallmechanical generator--the latter by a spark coil, frictional orinfluence machine or by a Leyden jar. Galvanic. Adj. Voltaic; relating to current electricity or the electrolytic andelectro-chemical relations of metals. (For titles in general under thishead see Voltaic--or the main title. ) Galvanic Element. A galvanic couple with exciting fluid and adjuncts; a galvanic cell. Theword element is sometimes applied to the electrodes of a cell, as thecarbon element or zinc element. 265 STANDARD ELECTRICAL DICTIONARY. Galvanic Polarization. The polarization of a voltaic couple. (See Polarization. ) Galvanism. The science of voltaic or current electricity. Galvanization. (a) Electroplating or depositing a metal over the surface of another byelectrolysis. (b) In medical electricity the effects produced on any part of thesystem by the current of voltaic battery. Various descriptivequalifications are prefixed, such as "general" galvanization, indicatingits application as applied to the whole body, "local" for the reversecase, and so on. Galvanization, Labile. Application of the galvanic current in electro-therapeutics where onesponge electrode is employed which is rubbed or moved over the body, theother being in constant contact with the body. Galvanized Iron. Iron coated with zinc by cleaning and immersion in melted zinc. The ironis prevented from rusting by galvanic action. It forms the negativeelement in a couple of which the zinc is the positive element. From thiselectric protective action the name is derived. Galvano-cautery, Chemical. Electro-therapeutic treatment with sharp electrodes, one of which isinserted in the tissue and a current passed by completing the circuitthrough the tissue so as to electrolyze or decompose the fluids of thetissue. It is applied in the removal of hair or extirpation of thefollicle. The process is not one of heating, and is improperly namedcautery. Galvano-faradization. In medical electricity the application of the voltaic and induced orsecondary current simultaneously to any part of the system. Galvanometer. An instrument for measuring current strength and sometimes for measuringinferentially potential difference, depending on the action of amagnetic field established by the current, such action being exerted ona magnetic needle or its equivalent. A current passing through a conductor establishes circular lines offorce. A magnetic needle placed in their field is acted on and tends toplace itself parallel with the lines, in accordance with the principlesof current induction. (See Induction, Electro-magnetic. ) A commoncompass held near a conductor through which a current is passing tendsto place itself at right angles to such conductor. For a maximum effectthe conductor or the part nearest the needle should lie in the magneticmeridian. If at right angles thereto its action will only strengthen thedirective force of the earth's induction or magnetic field, as theneedle naturally points north and south. Such combination is virtually agalvanometer. 266 STANDARD ELECTRICAL DICTIONARY. A typical galvanometer comprises a flat coil of wire placed horizontallywithin which a magnetic needle is delicately poised, so as to be free torotate with the least possible friction. The needle may be supported ona sharp point like a compass needle, or may be suspended by a long finefilament. It should be covered by a glass plate and box, or by a glassshade. Finally a graduated disc may be arranged to show the amount ofdeflection of the needle. In use the apparatus is turned about until the needle, as acted on bythe earth's magnetic field, lies parallel to the direction of the coilsof wire. On passing a current through the coil the needle is deflected, more or less, according to its strength. By using exceedingly fine wire, long enough to give high resistance, theinstrument can be used for very high potentials, or is in condition foruse in determining voltage. By using a coil of large wire and lowresistance it can be employed in determining amperage. In either casethe deflection is produced by the current. The needle is often placed above or below the coil so as only to receivea portion of its effect, enough for all practical purposes in thecommoner class of instruments. The galvanometer was invented by Schweigger a short time after Oersted'sdiscovery, q. V. Galvanometer, Absolute. A galvanometer giving absolute readings; properly one whose law ofcalibration can be deduced from its construction. Thus the diameter ofthe coil, and the constants and position of a magnetic needle suspendedin its field being known, the current intensity required to deflect theneedle a given number of degrees could be calculated. Galvanometer, Aperiodic. A galvanometer whose needle is damped (see Damping) as, for instance, bythe proximity of a plate of metal, by an air vane or otherwise, so thatit reaches its reading with hardly any oscillation. A very light needleand a strong magnetic field also conduce to vibrations of short perioddying out very quickly. Such galvanometers are termed "dead-beat. " Noinstrument is absolutely dead-beat, only relatively so. 267 STANDARD ELECTRICAL DICTIONARY. Fig. 178. ASTATIC GALVANOMETER. Galvanometer, Astatic. A galvanometer with a pair of magnetic needles connected astatically, orparallel with their poles in opposition. (See Astatic Needle. ) Eachneedle has its own coil, the coils being wound in opposite directions soas to unite in producing deflections in the same sense. As there shouldbe some directive tendency this is obtained by one of the magnets beingslightly stronger than the other or by the proximity of a fixed andadjustable controlling magnet, placed nearer one needle than the other. For small deflections the currents producing them are proportional totheir extent. Galvanometer, Ballistic. A galvanometer whose deflected element has considerable moment ofinertia; the exact opposite of an aperiodic or dead beat galvanometer. (See Galvanometer, Aperiodic. ) All damping by air vanes or otherwisemust be carefully done away with. Fig. 179. SIEMENS & HALSKE'S GALVANOMETER. Siemens & Halske's galvanometer is of the reflecting or mirror type (seeGalvanometer, Reflecting) with suspended, bell-shaped magnet, in placeof the ordinary magnetic needle, or astatic combination of the lightestpossible weight in the regular instrument. A copper ball drilled out toadmit the magnet is used as damper in the ordinary use of theinstrument. To convert it into a ballistic galvanometer the copper ballis removed. The heavy suspended magnet then by its inertia introducesthe desired element into the instrument. 268 STANDARD ELECTRICAL DICTIONARY. Referring to the cut, Fig. 179, M is the suspended magnet, with northand south poles n and s; S is the reflecting mirror; r is the tubecontaining the suspending thread; R is the damper removed for ballisticwork. The ballistic galvanometer is used to measure quantities of electricityin an instantaneous discharge, which discharge should be completedbefore the heavy needle begins to move. The extreme elongation or throwof the needle is observed, and depends (1) on the number of coulombs (K)that pass during the discharge; (2) on the moment of inertia of theneedle and attached parts; (3) on the moment of the controlling forces, i. E. , the forces tending to pull the needle back to zero; (4) on themoment of the damping forces; (5) on the moment of the deflecting forcesdue to a given constant current. The formula is thus expressed: K = (P / PI ) * A * sin( kº / 2 ) / tan( aº ) in which K = coulombs discharged; P = periodic time of vibration ofneedle; A = amperes producing a steady deflection equal to aº ; kº =first angular deflection of needle. For accuracy kº and aº should bothbe small and the damping so slight as to be negligible. Otherwise acorrection for the latter must be applied. For approximate work for kºand aº the deflections read on the scale may be used with the followingformula: K = (P / PI ) * ( A / 2 ) * ( kº / aº ) Galvanometer Constant. Assume a galvanometer with a very short needle and so placed withrespect to its coils that the magnetic field produced by a currentcirculating in them is sensibly uniform in the neighborhood of theneedle, with its lines of force at right angles thereto. The field isproportional to the current i, so that it may be denoted by G i. Then Gis the galvanometer constant. If now the angle of deflection of theneedle is ? against the earth's field H, M being the magnetic moment ofthe needle we have G i M cos ? = H M sin ? or i = (H/G)* tan ?. H/G isthe reduction factor; variable as H varies for different places. For a tangent galvanometer the constant G is equal to 2*PI*(n/a), inwhich n denotes the number of turns of wire, and a denotes the radius ofthe circle. Galvanometer, Differential. A galvanometer in which the needle is acted on by two coils wound inopposition, each of equal deflecting action and of equal resistance. Ifa current is divided between two branches or parallel conductors, eachincluding one of the coils, when the needle points to zero theresistances of the two branches will bc equal. In the cut, C C'represent the coils, and A and B the two leads into which the circuit, PQ, is divided. 269 STANDARD ELECTRICAL DICTIONARY. Fig. 180. THEORY OF DIFFERENTIAL GALVANOMETER. Fig. 181. DIFFERENTIAL GALVANOMETER. Galvanometer, Direct Reading. A calibrated galvanometer, whose scale is graduated by volts or amperes, instead of degrees. Galvanometer, Marine. (Sir William Thomson's. )A galvanometer of the reflecting type, for use on shipboard. A fibresuspension is adopted for the needle. The fibre is attached to a fixedsupport at one end and to a spring at the other, and the needle issuspended by its centre of gravity. This secures it to a considerableextent from disturbance due to the rolling of the ship. A thick iron boxencloses the needle, etc. , to cut off any magnetic action from the ship. (See Galvanometer, Reflecting. ) Galvanometer, Potential. A galvanometer wound with fine German silver wire to secure highresistance used for determination of potential difference. Galvanometer, Proportional. A galvanometer so constructed that the deflections of its index areproportional to the current passing. It is made by causing thedeflecting force to increase as the needle is deflected, more and more, or by causing the restitutive force to diminish under like conditions, or by both. The condition is obtained in some cases by the shape andposition of the deflecting coils. Galvanometer, Quantity. A galvanometer for determining quantities of electricity, by thedeflections produced by discharging the quantities through their coils. It is a ballistic galvanometer with very little or no damping. 270 STANDARD ELECTRICAL DICTIONARY. Fig. 182. PRINCIPLE OF REFLECTING GALVANOMETER. Fig. 183. REFLECTING GALVANOMETER. Galvanometer, Reflecting. A galvanometer the deflections of whose needle are read by an imageprojected by light reflected from a mirror attached to the needle or toa vertical wire carrying the needle. A lamp is placed in front of theinstrument facing the mirror. The light of the lamp is reflected by themirror upon a horizontal scale above the lamp. An image of a slit or ofa wire may be caused thus to fall upon the scale, the mirror beingslightly convex, or a lens being used to produce the projection. 271 STANDARD ELECTRICAL DICTIONARY. If the mirror swings through a horizontal arc, the reflected image willmove, in virtue of a simple geometrical principle, through an arc oftwice as many degrees. The scale can be placed far from the mirror, sothat the ray of light will represent a weightless index of very greatlength, and minute deflections of the needle will be shown distinctlyupon the scale. In the cut, Fig. 182, the ray of light from the lamp passes through theaperture, m m, and is made parallel by the lens, L. At s is the mirrorattached to the needle and moving with it. A scale placed at t receivesthe reflection from the mirror. The cut, Fig. 183, shows one form of theinstrument set up for use. Synonym--Mirror Galvanometer. Galvanometer Shunt. To prevent too much current passing through a galvanometer (for fear ofinjury to its insulation) a shunt is sometimes placed in parallel withit. The total current will be distributed between galvanometer and shuntin the inverse ratio of their respective resistances. (See MultiplyingPower of a Shunt. ) 272 STANDARD ELECTRICAL DICTIONARY. Fig. 184. SINE GALVANOMETER. Galvanometer, Sine. A galvanometer whose measurements depend upon the sine of the angle ofdeflection produced when the coil and needle lie in the same verticalplane. The needle, which may be a long one, is surrounded by a coil, which canbe rotated about a vertical axis passing through the point of suspensionof the needle. Starting with the needle at rest in the plane of thecoil, a current is passed through the coil deflecting the needle, thecoil is swung around deflecting the needle still more, until the needlelies in the plane of the coil; the intensity of the current will then bein proportion to the sine of the angle through which the coil and needlemove. In the galvanometer M is a circle carrying the coil, N is a scale overwhich the needles, m and n, move, the former being a magnetic needle, the latter an index at right angles and attached thereto; a and b arewires carrying the current to be measured. The circles, M and N, arecarried by a base, O, around which they rotate. H is a fixed horizontalgraduated circle. In use the circle, M, is placed in the magneticmeridian, the current is passed through the coil, M; the needle isdeflected; M is turned until its plane coincides with the direction ofthe needle, m. The current strength is proportional to the sine of theangle of deflection. This angle is measured by the vernier, C, on thecircle, H. The knob, A, is used to turn the circle, M. 273 STANDARD ELECTRICAL DICTIONARY. Fig. 185. TANGENT GALVANOMETER. Galvanometer, Tangent. A galvanometer in which the tangents of the angles of deflection areproportional to the currents producing such deflections. For this law to apply the instrument in general must fulfill thefollowing conditions: (1) The needle must be controlled by a uniform magnetic field such asthat of the earth; (2) the diameter of the coil must be large compared to the length of theneedle; (3) the centre of suspension of the needle must be at the centre of thecoil; (4) the magnetic axis of the needle must lie in the plane of the coilwhen no current is passing. If a single current strength is to be measured the best results will beattained when the deflection is 45°; in comparing two currents the bestresults will be attained when the deflections as nearly as possible areat equal distances on both sides of 45°. The needle should not exceed in length one-tenth the diameter of thecoil. For very small deflections any galvanometer follows the law oftangential deflection. As for very small deflections the tangents are practically equal to thearcs subtended, for such deflections the currents are proportional tothe deflections they produce. The sensibility is directly proportional to the number of convolutionsof wire and inversely proportional to their diameter. The tangent law is most accurately fulfilled when the depth of the coilin the radial direction is to the breadth in the axial direction assquareRoot(3):squareRoot(2), or about as 11:9. Galvanometer, Torsion. A galvanometer whose needle is suspended by a long filament or by athread and spiral spring against whose force of torsion the movements ofthe needle are produced. The current strength is determined by bringingthe needle back to its position of rest by turning a hand-button orother arrangement. The angle through which this is turned gives theangle of torsion. From this the current strength is calculated on thegeneral basis that it is proportional to the angle of torsion. Fig. 186. TORSION GALVANOMETER. 274 STANDARD ELECTRICAL DICTIONARY. Galvanometer, Vertical. A galvanometer whose needle is mounted on a horizontal axis and isdeflected in a vertical plane. One of the poles is weighted to keep itnormally vertical, representing the control. It is not used for accuratework. Synonym--Upright Galvanometer. Fig. 187. VERTICAL GALVANOMETER. Galvanometer, Volt- and Ampere-meter. A galvanometer of Sir William Thomson's invention embodying the tangentprinciple, and having its sensibility adjustable by moving the magneticneedle horizontally along a scale (the "meter") towards or away from thecoil. A curved magnet is used to adjust the control. The leads aretwisted to prevent induction. The instrument is made with a high resistance coil for voltagedeterminations, and with a low resistance coil for amperagedeterminations. At one end of a long base board a vertical coil with its plane at rightangles to the axis of the board is mounted. A scale (the "meter" of thename) runs down the centre of the board. A groove also runs down thecentre. The magnetic needle is contained in a quadrant-shapedglass-covered box which slides up and down the groove. A number of shortparallel needles mounted together, with an aluminum pointer are used. Fig. 188. SIR WILLIAM THOMSON'S AMPERE-METER GALVANOMETER. 275 STANDARD ELECTRICAL DICTIONARY. In the cut P is the base board, M is a glass covered case containing themagnetic needle, and sliding along the base board, being guided by thecentral groove, C, is the coil. Between the coil and the needle is thearched or bent controlling magnet. The long twisted connecting wires areseen on the right hand. Galvano-plastics. The deposition of metals by electrolysis, a disused term replacedby electro-deposition, electroplating, and electro-metallurgy. Galvano-puncture. An operation in medical electricity. (See Electro-puncture. ) Galvanoscope. An instrument, generally of the galvanometer type, used for ascertainingwhether a current is flowing or not. Any galvanoscope, when calibrated, if susceptible thereof, becomes a galvanometer. Gas, Electrolytic. Gas produced by the decomposition, generally of water, by electrolysis. It may be hydrogen or oxygen, or a mixture of the two, according to howit is collected. (See Gases, Mixed. ) Gases, Mixed. The mixture of approximately one volume of oxygen and two volumes ofhydrogen collected in the eudiometer of a gas voltameter or otherelectrolytic apparatus. Gassing. The evolution of gas from the plates of a storage battery in thecharging process, due to too high voltage in the circuit of the chargingdynamo. Gastroscope. An apparatus for illuminating by an incandescent lamp the interior ofthe stomach, and with prisms to refract the rays of light so that thepart can be seen. The stomach is inflated with air, if desirable, togive a better view. An incandescent platinum spiral in a water jackethas been employed for the illumination. Gassiot's Cascade. A goblet lined for half its interior surface with tinfoil. It is placedin the receiver of an air pump from the top of whose bell a conductordescends into it, not touching the foil. On producing a goodrarefaction, and discharging high tension electricity from between theconductor just mentioned and the metal of the machine, a luminous effectis produced, as if the electricity, pale blue in color, was overflowingthe goblet. Gauss. A name suggested for unit intensity of magnetic field. Sylvanus P. Thomson proposed for its value the intensity of a field of 1E8 C. G. S. Electro-magnetic units. J. A. Fleming proposed the strength of fieldwhich would develop one volt potential difference in a wire 1E6centimeters long, moving through such field with a velocity of onecentimeter per second. This is one hundred times greater than Thomson'sstandard. Sir William Thomson suggested the intensity of field producedby a current of one ampere at a distance of one centimeter The gauss is not used to any extent; practical calculations are based onelectro-magnetic lines of force. 276 STANDARD ELECTRICAL DICTIONARY. Gauss' Principle. An electric circuit acts upon a magnetic pole in such a way as to makethe number of lines of force that pass through the circuit a maximum. Fig. 189. GAUSS' TANGENT POSITION. Gauss, Tangent Positions of. The "end on" and "broadside" methods of determining magnetizationinvolve positions which have been thus termed. (See Broadside Method andEnd on Method. ) Gear, Magnetic Friction. Friction gear in which the component wheels are pressed against eachother by electromagnetic action. In the cut, repeated from Adherence, Electro-magnetic, the magnetizing coil makes the wheels, which are ofiron, press strongly together. Fig. 190. MAGNETIC FRICTION GEAR. 277 STANDARD ELECTRICAL DICTIONARY. Geissler Tubes. Sealed tubes of glass containing highly rarefied gases, and providedwith platinum electrodes extending through the glass tightly sealed asthey pass through it, and often extending a short distance beyond itsinterior surface. On passing through them the static discharge luminous effects areproduced varying with the degree of exhaustion, the contents (gas), theglass itself, or solutions surrounding it. The two latter conditionsinvolve fluorescence phenomena often of a very beautiful description. The pressure of the gas is less than one-half of a millimeter ofmercury. If a complete vacuum is produced the discharge will not pass. If too high rarefaction is produced radiant matter phenomena (seeRadiant State) occur. Geissler tubes have been used for lighting purposes as in mines, or forilluminating the interior cavities of the body in surgical or medicaloperations. Generating Plate. The positive plate in a voltaic couple, or the plate which is dissolved;generally a plate of zinc. Synonyms--Positive Plate--Positive Element. Generator, Current. Any apparatus for maintaining an electric current. It may be as regardsthe form of energy it converts into electrical energy, mechanical, as amagneto or dynamo electric machine or generator; thermal, as athermo-electric battery; or chemical, as a voltaic battery; all of whichmay be consulted. Generator, Secondary. A secondary or storage battery. (See Battery, Secondary. ) German Silver. An alloy of copper, 2 parts, nickel, 1 part, and zinc, 1 part. Owing toits high resistance and moderate cost and small variation in resistancewith change of temperature, it is much used for resistances. From Dr. Mathiessen's experiment the following constants are deduced in legalohms: Relative Resistance (Silver = 1), 13. 92 Specific Resistance at 0° C. (32F. ), 20. 93 microhms. Resistance of a wire, (a) 1 foot long, weighing 1 grain, 2. 622 ohms. 1 foot long, 1/1000 inch thick, 125. 91 " 1 meter long, weighing 1 gram, 1. 830 " 1 meter long, 1 millimeter thick, 0. 2666 " Resistance of a 1 inch cube at 0°C. (32° F. ), 8. 240 microhms. Approximate percentage increase of resistance per 1° C. (1. 8° F. ) atabout 20° C. (68° F. ), 0. 044 per cent. Gilding, Electro-. The deposition of gold by an electric current, or electrolytically inthe electroplating bath. Gilding Metal. A special kind of brass, with a high percentage of copper, used to makeobjects which are to be gilded by electrolysis. 278 STANDARD ELECTRICAL DICTIONARY. Gimbals. A suspension used for ships' compasses and sometimes for otherapparatus. It consists of a ring held by two journals, so as to bc freeto swing in one plane. The compass is swung upon this ring, being placedconcentrically therewith. Its journals are at right angles to those ofthe ring. This gives a universal joint by which the compass, weightedbelow its line of support, is always kept horizontal. Fig. 191. COMPASS SUSPENDED IN GIMBALS. Glass. A fused mixture of silicates of various oxides. It is of extremelyvaried composition and its electric constants vary greatly. Manydeterminations of its specific resistance have been made. For flintglass at 100° C. (212° F. ) about (2. 06E14) ohms --at 60° C (140° F. )(1. 020E15) (Thomas Gray) is given, while another observer (Beetz) givesfor glass at ordinary temperatures an immeasurably high resistance. Itis therefore a non-conductor of very high order if dry. As a dielectricthe specific inductive capacity of different samples of flint glass isgiven as 6. 57--6. 85--7. 4--10. 1 (Hopkinson), thus exceeding all otherordinary dielectrics. The densest glass, other things being equal, hasthe highest specific inductive capacity. Gold. A metal, one of the elements; symbol Au. C . ; atomic weight, 196. 8;equivalent, 65. 6; valency, 3; specific gravity 19. 5. It is a conductor of electricity. Annealed. Hard drawn. Relative Resistance (Annealed Silver = 1), 1. 369 1. 393Specific Resistance, 2. 058 2. 094Resistance of a wire at 0° C. (32°F. )(a) 1 foot long, weighing 1 grain, 57. 85 58. 84 ohms(b) 1 foot long, 1/1000 inch thick, 12. 38 12. 60 "(c) 1 meter long, weighing 1 gram, . 4035 . 4104 "(d) 1 meter long, 1 millimeter thick, . 02620 . 02668 "Resistance of a 1 inch cube at 0° C. (32° F. ) . 8102 . 8247 Approximate increase in resistance per 0° C. , (1. 8° F)at about 20° C. (68° F. ), 0. 365 per cent. Electro-chemical equivalent (Hydrogen = . 0105), . 6888 279 STANDARD ELECTRICAL DICTIONARY. Gold Bath. A solution of gold used for depositing the metal in the electroplatingprocess. A great number of formulae have been devised, of which a fewrepresentative ones are given here. COLD BATHS. HOT BATHS. Water, 10, 000 10, 000 10, 000 10, 000 5, 000 3, 000Potassium Cyanide, 200 -- 200 10 -- 50Gold, 100 15 100 10 10 10Potassium Ferrocyanide, -- 200 -- -- 150 --Potassium Carbonate, -- 150 -- -- 50 --Ammonium Chloride, -- 30 -- -- 20 --Aqua Ammoniae, -- -- 500 -- -- --Sodium Phosphate, -- -- -- 600 -- --Sodium Bisulphite, -- -- -- 100 -- -- (Roseleur. ) In the baths the gold is added in the form of neutral chloride, Auricchloride (Au Cl6). Gold Stripping Bath. A bath for removing gold from plated articles without dissolving thebase in order to save the precious metal. A bath of 10 parts ofpotassium cyanide and 100 parts of water may be used, the articles to bestripped being immersed therein as the anode of an active circuit. Ifthe gilding is on a silver or copper basis, or on an alloy of thesemetals the same solution attacks the base and dissolves it, which isobjectionable. For silver articles it is enough to heat to cherry redand throw into dilute sulphuric acid. The gold scales off in metallicspangles. For copper articles, a mixture of 10 volumes concentratedsulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acidmay be used by immersion only, or with a battery. The sulphuric acid insuch large excess is supposed to protect the copper. For copper articlesconcentrated sulphuric acid alone with the battery may be used. Thisdoes not sensibly attack the copper if it is not allowed to becomediluted. Even the dampness of the air may act to dilute it. Graduator. Apparatus for enabling the same line to be used for telegraph signalsand telephoning. One type consists in coils with iron cores or simply electromagnets. These act to retard the current in reaching its full power and alsoprolong it. This gives a graduated effect to the signals, so that thetelephone diaphragm is not audibly affected by the impulses. The telephoning current is so slight and so rapid in its characteristicchanges that it is without effect upon the ordinary telegraph. 280 STANDARD ELECTRICAL DICTIONARY. Gram. The unit of weight in the metric system; accepted as the unit ofmass in the absolute of C. G. S. System of units. It is theone-thousandth part of mass of a standard weight preserved under properconditions in Paris, and supposed to be the mass of a cubic decimeter ofdistilled water at the temperature of the maximum density of water. Thestandard is the kilogram; the temperature is 3. 9º C. (39º F. ). Thestandard kilogram is found to be not exactly the weight of a cubicdecimeter of water, the latter weighing 1. 000013 kilogram. If therefore the defined gram on the water basis is taken as the unit itvaries very slightly from the accepted gram. 1 gram is equal to 15. 43234874 grains. (Prof. W. H. Miller. ) Gram-atom. The number of grams of an element equal numerically to the atomicweight, as 16 grams of oxygen, 1 gram of hydrogen, 35. 5 grams ofchlorine; all which might be expressed as gram-atoms of oxygen, hydrogenand chlorine respectively. The gram-atom approximately expresses the number of gram-caloriesrequired to heat one gram of the substance 1º C. (1. 8º F. ). This is invirtue of Dulong and Petit's discovery that the atomic weight of anelement multiplied by its specific heat gives approximately a constantfor all elements. [Transcriber's note: A gram-atom is the mass, in grams, of one mole ofatoms in a monatomic element. A mole consists of Avogadro's number ofatoms, approximately 6. 02214E23. ] Gram-molecule. The number of grams of a substance equal numerically to its molecularweight. Graphite. Carbon; one of three allotropic modifications of this element. It occursin nature as a mineral. It is used as a lubricant for machinery; for commutator brushes; formaking surfaces to be plated conductive, and for mixing with manganesebinoxide in Leclanché cells. Gravitation. A natural force which causes all masses of matter to attract each other. Its cause is unknown; it is often supposed to be due to the luminiferousether. [Transcriber's note: Einstein's explanation of gravity, GeneralRelativity and the curvature of space-time, came 23 years later, 1915. ] 281 STANDARD ELECTRICAL DICTIONARY. Gravity, Acceleration of. The velocity imparted to a body in one second by the action ofgravitation at any standard point upon the earth's surface in a vacuum. This will vary at different places, owing principally to the variationin centrifugal force due to the earth's rotation. For standard valuationit must be reduced to sea level. The following are examples of itsvariation: Equator, 978. 1028 centimeters per secondParis, 980. 94 "Greenwich 981. I7 "Edinburgh, 981. 54 "Pole (N. Or S. ), 983. 1084 (theoretical) " As round numbers for approximate calculations 981 centimeters or 32. 2feet may be employed. [Transcriber's note: The acceleration of gravity at the equator is alsoreduced by the increased distance from the center of the earth(equatorial bulge). Increased altitude reduces gravity. Reduced airdensity at altitude reduces buoyancy and increases apparent weight. Local variations of rock density affects gravity. ] Gravity, Control. Control by weight. In some ammeters and voltmeters gravity is thecontrolling force. Grid. A lead plate perforated or ridged for use in a storage battery as thesupporter of the active materials and in part as contributing theretofrom its own substance. Ground. The contact of a conductor of an electric circuit with the earth, permitting the escape of current if another ground exists. Ground-wire. A metaphorical term applied to the earth when used as a return circuit. Fig. 192. GROVE'S GAS BATTERY. Grove's Gas Battery. A voltaic battery depending for its action on the oxidation of hydrogeninstead of the oxidation of zinc. Its action is more particularlydescribed under Battery, Gas. In the cut B, B1 * * * are the terminalsof the positive or hydrogen electrodes, marked H, and A, Al * * * arethe terminals of the negative or oxygen electrodes marked O, while M, M1* * * is dilute sulphuric acid. 282 STANDARD ELECTRICAL DICTIONARY. Guard Ring. An annular horizontal surface surrounding the balanced disc in theabsolute electrometer. (See Electrometer, Absolute. ) Guard Tube. A metal tube surrounding a dry pile used with a quadrant electrometer, or other electrometers of that type. It prevents the capacity of thelower brass end of the pile (which brass end closes the glass tubecontaining the discs) from momentary change by approach of someconductor connected to the earth. There are other guard tubes also. Gun, Electro-magnetic. An electro-magnet with tubular core. If, when it is excited a piece ofan iron rod is pushed into the central aperture of the core and isreleased, the magnetic circle will try to complete itself by pushing therod out so that it can thus be discharged, as if from a popgun. Synonym--Electric Popgun. Fig. 193. "ELECTRIC POPGUN. " Gutta Percha. The hardened milky juice of a tree, the Isonandra gutta, growing inMalacca and other parts of the Eastern Archipelago. It is much used asan insulator or constituent of insulators. Resistance after several minutes electrification per 1 centimeter cubeat 54º C. (75º F. ), 4. 50E14 ohms. The specific resistance varies--from 2. 5E13 to 5. 0E14 ohms. A usualspecification is 2. 0E14 ohms. The influence of temperature on itsresistance is given in Clark & Bright's empirical formula, R = R0 at, inwhich R is the resistance at temperature tº C--Ro the resistance at 0º C(32º F), a is the coefficient . 8944. The resistance increases with the time of passage of the current, thevariation being less the higher the temperature. 283 STANDARD ELECTRICAL DICTIONARY. Time of Relative Resistance Relative ResistanceElectrification. At 0º C (32º F. ) at 24º C (75º F. ) 1 minute 100 5. 51 2 " 127. 9 6. 5 " 163. 1 6. 66 10 " 190. 9 6. 94 20 " 230. 8 7. 38 30 " 250. 6 7. 44 60 " 290. 4 7. 6 90 " 318. 3 7. 66 In cable testing one minute is generally taken as the time ofelectrification. Pressure increases the resistance by the formula Rp=R (1+ . 00327 P) inwhich Rp is the resistance at pressure p--R resistance at atmosphericpressure--p pressure in atmospheres. Thus in the ocean at a depth of4, 000 meters (2. 4855 miles), the resistance is more than doubled. Thelonger the pressure is applied, the greater is the resistance. The specific inductive capacity of gutta percha is 4. 2. Good gutta percha should not break when struck with a hammer, shouldrecover its shape slowly, and it should support much more than 300 timesits own weight. Gyrostatic Action of Armatures. Owing to gyrostatic action a rotating armature resists any change ofdirection of its axis. On ships and in railway motors which have to turncurves this action occurs. A 148 lb. Armature running at 1, 300revolutions per minute may press with 30 lbs. On each journal as theship rolls through an angle of 20° in 16 seconds. H. (a) The symbol for the horizontal component of the earth'smagnetization. (b) The symbol for the intensity of a magnetizing force or field. Thesymbol H, as it is generally used, may mean either the number of dyneswhich act upon a unit pole, or the number of lines of force percentimeter. (c) The symbol for the unit of self-induction. Hair, Removal of, by Electrolysis. A method of depilation by destruction of individual hair follicles byelectrolysis. A fine platinum electrode is thrust into a hair follicle. It is thenegative electrode. The positive electrode is in contact with the bodyof the person under treatment; it is often a sponge electrode simplyheld in his hand. A current of two to four milliamperes from an E. M. F. Of 15 to 20 volts, is passed. This destroys the follicle, the hair isremoved and never grows again. A gradual increase of current is advisedfor the face. As only one hair is removed at once, but a small numberare taken out at a sitting. 284 STANDARD ELECTRICAL DICTIONARY. Haldat's Figures. With a pole of a strong bar magnet, used like a pencil, imaginaryfigures are drawn upon a hard steel plate, such as a saw-blade. Thepattern is gone over several times. By dusting iron filings on a sheetof paper laid over the steel plate, while horizontal, very complicatedmagnetic figures are produced. Hall's Experiment. A cross of thin metal, such as gold leaf, is secured upon a pane ofglass. To two opposite arms a battery is connected in circuit with them. To the other two arms a galvanometer is connected in circuit. If thecross is put into a field of force whose lines are perpendicularthereto, the galvanometer will disclose a constant current. The currentis pushed, as it were, into the galvanometer circuit. Other metals havebeen used with similar results. They must be thin or the experimentfails. If the arm receiving the battery current is horizontal, and if itflows from left to right, and if the lines of force go from downwardthrough the cross, the current in the galvanometer circuit will flowfrom the observer through the other arms of the cross, if the cross isof gold, silver, platinum or tin, and the reverse if of iron. Theexperiment has indicated a possible way of reaching the velocity ofelectricity in absolute measure. Hall Effect. The effect observed in Hall's experiment, q. V. Hall Effect, Real. A transverse electro-motive force in a conductor through which a currentis passing produced by a magnetic field. Hall Effect, Spurious. A spurious electro-motive force produced in a conductor, through which acurrent is passing by changes in conductivity of the conductor broughtabout by a magnetic field. Hanger Board. A board containing two terminals, a suspending hook, and a switch, sothat an arc lamp can be introduced into a circuit thereby, or can beremoved as desired. Harmonic Receiver. A receiver containing a vibrating reed, acted on by an electro-magnet. Such a reed answers only to impulses tuned to its own pitch. If such arereceived from the magnet it will vibrate. Impulses not in tune with itwill not affect it. (See Telegraph, Harmonic. ) Head Bath, Electric. A fanciful name for an electro-medical treatment of the head. Thepatient is insulated by an insulating stool or otherwise. His person isconnected with one terminal of an influence machine. An insulatedmetallic circle, with points of metal projecting inward or downward, isplaced about the head. The circle is connected with the other pole ofthe machine. On working it a silent or brush discharge with airconvection streams occurs between the patient's head and the circle ofpoints. 285 STANDARD ELECTRICAL DICTIONARY. Head-light, Electric. An electric head-light for locomotives has been experimented with. Itincludes the parabolic reflection of the regular light with an arc-lampin place of the oil lamp. An incandescent lamp may be used in the sameplace, but has no great advantage over oil as regards illuminatingpower. Heat. A form of kinetic energy, due to a confused oscillatory movement of themolecules of a body. Heat is not motion, as a heated body does notchange its place; it is not momentum, but it is the energy of motion. Ifthe quantity of molecular motion is doubled the momentum of themolecules is also doubled, but the molecular mechanical energy or heatis quadrupled. As a form of energy it is measured by thermal units. The calorie is themost important, and unfortunately the same term applies to two units, the gram-degree C. And the kilogram-degree C. (See Calorie. ) Caloriesare determined by a calorimeter, q. V. Independent of quantity of heat a body may be hotter or colder. Thermometers are used to determine its temperature. Heat is transmitted by conduction, a body conducting it slowly for somedistance through its own substance. Bodies vary greatly in theirconductivity for heat. It is also transmitted by convection of gases orliquids, when the heated molecules traveling through the mass imparttheir heat to other parts. Finally it is transmitted by ether waves withprobably the speed of light. This mode of transmission and the phenomenaof it were attributed to radiant heat. As a scientific term this is nowdropped by many scientists. This practice very properly restricts theterm "heat" to kinetic molecular motion. The mechanical equivalent of heat is the number of units of work whichthe energy of one unit quantity of heat represents. (See Equivalents, Mechanical and Physical. ) Heat, Atomic. The product of the specific heat of an element by its atomic weight. Theproduct is approximately the same for all the elements, and varies asdetermined between 5. 39 and 6. 87. The variations are by some attributedprincipally to imperfection of the work in determining them. The atomicheat represents the number of gram calories required to raise thetemperature of a gram atom (a number of grams equal numerically to theatomic weight) one degree centigrade. 286 STANDARD ELECTRICAL DICTIONARY. Heat, Electric. This term has been given to the heat produced by the passage of acurrent of electricity through a conductor. It is really electricallyproduced heat, the above term being a misnomer. The rise of temperature produced in a cylindrical conductor by a currentdepends upon the diameter of the conductor and on the current. Thelength of the wire has only the indirect connection that the currentwill depend upon the resistance and consequently upon its length. The quantity of heat produced in a conductor by a current is ingram-degree C. Units equal to the product of the current, by theelectro-motive force or potential difference maintained between the endsof the wire, by . 24. The cube of the diameter of a wire for a given rise of temperatureproduced in such conductor by a current is equal approximately to theproduct of the square of the current, by the specific resistance (q. V. )of the material of the conductor, by . 000391, the whole divided by thedesired temperature in centigrade units. Heat, Electrical Convection of. A term applied to the phenomena included under the Thomson effect, q. V. , the unequal or differential heating effect produced by a current ofelectricity in conductors whose different parts are maintained atdifferent temperatures. Heater, Electric. An apparatus for converting electrical energy into thermal energy. An incandescent lamp represents the principle, and in the Edison meterhas been used as such to maintain the temperature of the solutions. Heaters for warming water and other purposes have been constructed, utilizing conductors heated by the passage of the current as a source ofheat. (See also Heating Magnet. ) Heating Error. In voltmeters the error due to alteration of resistance of the coil byheating. If too strong a current is sent through the instrument, thecoils become heated and their resistance increased. They then do notpass as much current as they should for the potential difference towhich they may be exposed. Their readings then will be too low. One wayof avoiding the trouble is to have a key in circuit, and to pass only aninstantaneous or very brief current through the instrument and thus getthe reading before the coils have time to heat. The heating error does not exist for ammeters, as they are constructedto receive the entire current, and any heating "error" within theirrange is allowed for in the dividing of the scale. Heating Magnet. An electro-magnet designed to be heated by Foucault currents induced inits core by varying currents in the windings. It has been proposed as asource of artificial heat, a species of electric heating apparatus forwarming water, or other purposes. 287 STANDARD ELECTRICAL DICTIONARY. Heat, Irreversible. The heat produced by an electric current in a conductor of identicalqualities and temperature throughout. Such heat is the same whatever thedirection of the current. The heating effect is irreversible because ofthe absence of the Thomson effect, q. V. ) or Peltier effect, q. V. Heat, Mechanical Equivalent of. The mechanical energy corresponding to a given quantity of heat energy. Mechanical energy is generally represented by some unit of weight andheight, such as the foot-pound; and heat energy is represented by agiven weight of water heated a given amount, such as a pound-degreecentigrade. Joule's equivalent is usually accepted; it states that772. 55 foot pounds of mechanical energy are equivalent to 1 pound-degreeF. (one pound avds. Of water raised in temperature one degreeFahrenheit). Other equivalencies have also been deduced. Heat, Molecular. The product of a specific heat of the compound by its molecular weight. It is approximately equal to the sum of the atomic heats of itsconstituent elements. The molecular heat represents the number of gram calories required toraise the temperature of a gram-molecule (a number of grams equalnumerically to the molecular weight) one degree centigrade. The molecular heat is approximately equal for all substances. Heat, Specific. The capacity of a body for heat; a coefficient representing the relativequantity of heat required to raise the temperature of an identicalweight of a given body a defined and identical amount. The standard of comparison is water; its specific heat is taken asunity. The specific heats by weight of other substances are less thanunity. The specific heat varies with the temperature. Thus the specificheat of water is more strictly 1+. 00015 tº C. Specific heat is greater when a substance is in the liquid than when itis in the solid state. Thus the specific heat of ice is 0. 489; lessthan half that of water. It differs with the allotropic modifications ofbodies; the specific heat of graphite is . 202; of diamond, . 147. The product of the specific heat by the atomic weight of elements givesa figure approximately the same. A similar law applies in the case ofmolecules. (See Heat, Atomic-Heat, Molecular. ) The true specific heat of a substance should be separated from the heatexpended in expanding a body against molecular and atomic forces, andagainst the atmospheric pressure. So far this separation has not beenpossible to introduce in any calculations. 288 STANDARD ELECTRICAL DICTIONARY. Heat, Specific, of Electricity. A proposed term to account for the heat absorbed or given out inunhomogeneous conductors, by the Thomson effect, or Peltier effect (seeEffect, Thomson--Effect, Peltier. ) If a current of electricity beassumed to exist, then under the action of these effects it may beregarded as absorbing or giving out so many coulombs of heat, and thusestablishing a basis for specific heat. Heat Units. The British unit of heat is the pound degree F--the quantity of heatrequired to raise the temperature of a pound of water from 32° to 33° F. The C. G. S. Unit is the gram-degree C. ; another metric unit is thekilogram-degree C. The latter is the calorie; the former is sometimescalled the small calorie or the joule; the latter is sometimes calledthe large calorie. The term joule is also applied to a quantity of heatequivalent to the energy of a watt-second or volt-coulomb. This is equalto . 24l gram degree calorie. Hecto. A prefix to terms of measurement--meaning one hundred times, ashectometer, one hundred meters. Heliograph. An apparatus for reflecting flashes of light to a distant observer. Byusing the Morse telegraph code messages may thus be transmitted longdistances. When possible the sun's light is used. Helix. A coil of wire; properly a coil wound so as to follow the outlines of ascrew without overlaying itself. Fig. 194. LEFT-HANDED HELIX. Fig. 195. RIGHT-HANDED HELIX. Henry. The practical unit of electro-magnetic or magnetic inductance. It isequal to 1E9 C. G. S. , or absolute units of inductance. As thedimensions of inductance are a length the henry is equal to 1E9centimeters, or approximately to one quadrant of the earth measured onthe meridian. Synonyms--Secohm--Quadrant--Quad. 289 STANDARD ELECTRICAL DICTIONARY. Hermetically Sealed. Closed absolutely tight. Glass vessels, such as the bulbs ofincandescent lamps, are hermetically sealed often by melting the glasstogether over any opening into their interior. Heterostatic Method. A method of using the absolute or attracted disc electrometer. (SeeElectrometer Absolute. ) The formula for its idiostatic use, q. V. , involves the determination of d, the distance between the suspended andfixed discs. As this is difficult to determine the suspended disc andguard ring may be kept at one potential and the lower fixed disc is thenconnected successively with the two points whose potential difference isto be determined. Their difference is determined by the differencebetween d and d', the two distances between the discs. This differenceis the distance through which the micrometer screw is moved. Theheterostatic formula is: V' - V = (d' - d)* squareRoot( 8*PI*F / S ) in which V and V' are potentials of the two points; d' and d the twodistances between the discs necessary for equilibrium; S the area of thedisc and F the force of attraction in dynes. (See Idiostatic Method. ) High Bars of Commutator. Commutator bars, which in the natural wear of the commutator, projectbeyond the others. The surface then requires turning down, as it shouldbe quite cylindrical. High Frequency. A term used as a noun or as an adjective to indicate in an alternatingcurrent, the production of a very great number of alternations per unitof time--usually expressed as alternations per second. Hissing. A term applied to a noise sometimes produced by a voltaic arc; probablydue to the same cause as frying, q. V. Hittorf's Solution. A solution used as a resistance. It is a solution of cadmium iodide inamylic alcohol. Ten per cent. Of the salt is used. It is contained in atube with metallic cadmium electrodes. (See Resistance, Hittorf' s. ) Fig. 196. HITTORF'S RESISTANCE TUBE. 290 STANDARD ELECTRICAL DICTIONARY. Holders. (a) The adjustable clamps for holding the armature brushes of dynamosand motors. (b) The clamps for holding the carbons of arc lamps. (c) The clamps for holding safety fuses, q. V. (d) Holders for Jablochkoff candles and other electric candles. (SeeCandle Holders. ) (e) A box or block of porcelain for holding safety fuses. Hood. A tin hood placed over an arc-lamp. Such hoods are often truncated conesin shape, with the small end upwards. They reflect a certain amount oflight besides protecting the lamp to some extent from rain. Horns. The extensions of the pole pieces of a dynamo or motor. (See FollowingHorns-Leading Horns. ) Synonym--Pole Tips. Horse Power. A unit of rate of work or activity. There are two horse powers. The British horse power is equal to 33, 000 pounds raised one foot perminute, or 550 foot pounds per second, or 1. 0138 metric horse power. The metric horse power (French) is equal to 75 kilogram-meters, or 542foot pounds per second, or . 986356 British horse power. H. P. Is the abbreviation for horse power. (See Horse Power, Electric. ) Horse Power, Actual. The rate of activity of a machine, as actually developed in conditionfor use. It is less than the indicated or total horse power, becausediminished by the hurtful resistances of friction, and other sources ofwaste. It is the horse power that can be used in practise, and which inthe case of a motor can be taken from the fly-wheel. Horse Power, Electric. The equivalent of a mechanical horse power in electric units, generallyin volt-amperes or watts; 745. 943 watts are equivalent to the activityof one British horse power; 735. 75 are equivalent to one metric horsepower. The number 746 is usually taken in practical calculations to givethe equivalency. [Transcriber's note: Contemporary values are: Mechanical (British)horsepower = 745. 6999 Watts; Metric horsepower = 735. 49875 Watts] Horse Power, Indicated. The horse power of an engine as indicated by its steam pressure, lengthof stroke, and piston area, and vacuum, without making any deduction forfriction or hurtful resistances. The steam pressure is in accurate workdeduced from indicator diagrams. Horse Power, Hour. A horse power exerted for one hour, or the equivalent thereof. As thehorse power is a unit of activity, the horse power hour is a unit ofwork or of energy. It is equal to 1, 980, 000 foot pounds. H. P. Abbreviation for "horse power. " 291 STANDARD ELECTRICAL DICTIONARY. Hughes' Electro-magnet. A horseshoe electro-magnet with polarized core. It is made by mountingtwo bobbins of insulated wire on the ends of a permanent horseshoemagnet. It was devised for use in Hughes' printing telegraph, where veryquick action is required. The contact lasts only . 053 second, 185letters being transmitted per minute. Fig. 197 HUGHES' ELECTRO-MAGNET. Fig. 198. HUGHES' INDUCTION BALANCE. Hughes' Induction Balance. An apparatus for determining the presence of a concealed mass of metal. The apparatus is variously connected. The cut shows a representativeform; a and a' are two primary coils, each consisting of 100 meters (328feet) of No. 32 silk covered copper wire (0. 009 inch diameter) wound ona boxwood spool ten inches in depth; b and b' are secondary coils. Allcoils are supposed to be alike. The primary coils are joined in serieswith a battery of three or four Daniell cells. A microphone m isincluded in the same circuit. The secondary coils are joined in serieswith a telephone and in opposition with each other. The clock is used toproduce a sound affecting the microphone. If all is exactly balancedthere will be no sound produced in the telephone. This balance isbrought about by slightly varying the distance of one of the secondariesfrom the primary, until there is no sound in the telephone. If now apiece of metal is placed within either of the coils, it disturbs thebalance and the telephone sounds. 292 STANDARD ELECTRICAL DICTIONARY. To measure the forces acting a sonometer or audiometer is used. This isshown in the upper part of the cut. Two fixed coils, c and e are mountedat the ends of a graduated bar. A movable coil d is connected in thetelephone circuit; c and e by a switch can be connected with the batteryand microphone circuit, leaving out the induction balance coils. Theends of the coils c and e, facing each other are of the same polarity. If these coils, c and e, were equal in all respects, no sound would beproduced when d was midway between them. But they are so wound that thezero position for d is very near one of them, c. Assume that a balance has been obtained in the induction balance withthe coil d at zero. No sound is heard whether the switch is moved tothrow the current into one or the other circuit. A piece of metal placedin one of the balance coils will cause the production of a sound. Thecurrent is turned into the sonometer and d is moved until the samesound, as tested by rapid movements of the switch, is heard in bothcircuits. The displacement of d gives the value of the sound. A milligram of copper is enough to produce a loud sound. Two coins canbe balanced against each other, and by rubbing one of them, or bybreathing on one of them, the balance will be disturbed and a sound willbe produced. Prof. Hughes has also dispensed with the audiometer. He has used a stripof zinc tapering from a width of 4 mm. (. 16 inch) at one end to a sharpedge or point at the other. The piece to be tested being in place in onecoil, the strip is moved across the face of the other until a balance isobtained. As possible uses the detection of counterfeit coins, the testing ofmetals for similarity of composition and the location of bullets in thebody have been suggested. Care has to be taken that no masses of metalinterfere. Thus in tests of the person of a wounded man, the presence ofan iron truss, or of metallic bed springs may invalidate allconclusions. The same principle is carried out in an apparatus in which the parts arearranged like the members of a Wheatstone bridge. One pair of coils isused, which react on each other as primary and secondary coils. One ofthe coils is in series with a telephone in the member of the bridgecorresponding to that containing the galvanometer of the Wheatstonebridge. The latter is more properly termed an induction bridge. Synonyms--Inductance Bridge--Inductance Balance--Induction Bridge. 293 STANDARD ELECTRICAL DICTIONARY. Hydro-electric. Adj. (a) A current produced by a voltaic couple or the couple itself issometimes thus characterized or designated as a "hydro-electric current"or a "hydro-electric couple. " It distinguishes them fromthermo-electric. (b) Armstrong's steam boiler electric machine (see HydroelectricMachine) is also termed a hydro-electric machine. Hydro-electric Machine. An apparatus for generating high potential difference by the escape ofsteam through proper nozzles. It consists of a boiler mounted on four glass legs or otherwiseinsulated. An escape pipe terminates in a series of outlets so shaped asto impede the escape of the steam by forcing it out of the directcourse. These jets are lined with hard wood. They are enclosed in or ledthrough a box which is filled with cold water. Fig. 199. ARMSTRONG'S HYDRO-ELECTRIC MACHINE. This is to partly condense the steam so as to get it into the vesicularstate, which is found essential to its action. Dry steam produces noexcitation. If the boiler is fired and the steam is permitted to escapeunder the above conditions the vesicles presumably, or the "steam" isfound to be electrified. A collecting comb held against the jet becomescharged and charges any connected surface. 294 STANDARD ELECTRICAL DICTIONARY. The boiler in the above case is negatively and the escaping "steam" ispositively charged. By changing the material of the linings of the jets, or by adding turpentine the sign of the electricity is reversed. If thewater contains acid or salts no electricity is produced. The regularhydro-electric machine is due to Sir William Armstrong. Faraday obtained similar results with moist air currents. Hydrogen. An element existing under all except the most extreme artificialconditions of pressure and cold as a gas. It is the lightest of knownsubstances. Atomic weight, 1; molecular weight, 2; equivalent, 1;valency, 1; specific gravity, . 0691-. 0695. (Dumas & Boussingault. ) It is a dielectric of about the same resistance as air. Its specificinductive capacity at atmospheric pressure is: . 9997 (Baltzman) . 9998 (Ayrton) Electro-chemical equivalent, . 0105 milligram. The above is usually taken as correct. Other values are as follows:. 010521 (Kohllrausch) . 010415 (Mascart) The electro-chemical equivalent of any element is obtained bymultiplying its equivalent by the electro-chemical equivalent ofhydrogen. The value . 0105 has been used throughout this book. Hygrometer. An instrument for determining the moisture in the air. One form consistsof a pair of thermometers, one of which has its bulb wrapped in clothwhich is kept moist during the observation. The evaporation is more orless rapid according to the dryness or moisture of the air, and as thetemperature varies with this evaporation the relative readings of thetwo thermometers give the basis for calculating the hygrometric state ofthe air. Another form determines the temperature at which dew isdeposited on a silver surface, whence the calculations are made. Hysteresis, Magnetic. A phenomenon of magnetization of iron. It may be attributed to a sort ofinternal or molecular friction, causing energy to be absorbed when ironis magnetized. Whenever therefore the polarity or direction ofmagnetization of a mass of iron is rapidly changed a considerableexpenditure of energy is required. It is attributed to the work done inbringing the molecules into the position of polarity. 295 STANDARD ELECTRICAL DICTIONARY. The electric energy lost by hysteresis may be reduced by vibrations orjarring imparted to the iron, thus virtually substituting mechanical forelectrical work. On account of hysteresis the induced magnetization of a piece of iron orsteel for fields of low intensity will depend on the manner in which thematerial has been already magnetized. Let the intensity of fieldincrease, the magnetization increasing also; then lower the intensity;the substance tends to and does retain some of its magnetism. Then onagain strengthening the field it will have something to build on, sothat when it attains its former intensity the magnetization will exceedits former value. For a moderate value of intensity of field themagnetization can have many values within certain limits. Synonym--Hysteresis--Hysteresis, Static--Magnetic Friction. Hysteresis, Viscous. The gradual increase or creeping up of magnetization when a magneticforce is applied with absolute steadiness to a piece of iron. It maylast for half an hour or more and amount to several per cent. Of thetotal magnetization. It is a true magnetic lag. I. A symbol sometimes used to indicate current intensity. Thus Ohm's law isoften expressed I = E/R, meaning current intensity is equal toelectro-motive force divided by resistance. C is the more general symbolfor current intensity. Ideoelectrics or Idioelectrics. Bodies which become electric by friction. This was the old definition, the term originating with Gilbert. It was based on a misconception, asinsulation is all that is requisite for frictional electrification, metals being thus electrified if held by insulating handles. The term isvirtually obsolete; as far as it means anything it means insulatingsubstances such as scaling wax, sulphur, or glass. Idle Coils. Coils in a dynamo, in which coils no electro-motive force is beinggenerated. This may occur when, as a coil breaks connection with thecommutator brush, it enters a region void of lines of magnetic force, orwhere the lines are tangential to the circle of the armature. Idiostatic Method. A method of using the absolute or attracted disc electrometer. (SeeElectrometer, Absolute. ) The suspended disc and guard ring are kept atthe same potential, which is that of one of the points whose potentialdifference is to be determined; the lower fixed disc is connected to theother of the points whose potential difference is to be determined. Thenwe have the formula V = d * SquareRoot( 8 * PI * F ) / S in which d is the distance between the discs, V is the difference ofpotential of the two points, F the force of attraction between the discsin dynes, and S the area of the suspended disc. (See HeterostaticMethod. ) 296 STANDARD ELECTRICAL DICTIONARY. Idle Poles. Poles of wire sealed into Crookes' tubes, not used for the dischargeconnections, but for experimental connections to test the effect ofdifferent excitation on the discharge. Idle Wire. In a dynamo the wire which plays no part in generating electro-motiveforce. In a Gramme ring the wire on the inside of the ring is idle wire. Igniter. In arc lamps with fixed parallel carbons of the Jablochkoff type (seeCandle, Jablochkoff) a strip of carbon connects the ends of the carbonsin the unused candle. This is necessary to start the current. Such stripis called an igniter. It burns away in a very short time when an arcforms producing the light, and lasts, if all goes well, until the candleburns down to its end. Without the igniter the current would not startand no arc would form. I. H. P. Symbol for indicated horse-power. Illuminating Power. The relative light given by any source compared with a standard light, and stated in terms of the same, as a burner giving an illuminatingpower of sixteen candles. For standards see Candle, Carcel--MethvenStandard--Pentane Standard. Illuminating Power, Spherical. The illuminating power of a lamp or source of light may vary indifferent directions, as in the case of a gas burner or incandescentlamp. The average illuminating power determined by photometric test orby calculation in all directions from the source of light is called thespherical illuminating power, or if stated in candles is called thespherical candle power. Illumination, Unit of. An absolute standard of light received by a surface. Preece proposed assuch the light received from a standard candle (see Candle, Standard) ata distance of 12. 7 inches. The object of selecting this distance was tomake it equal to the Carcel Standard (see Carcel), which is the lightgiven by a Carcel lamp at a distance of one meter. From one-tenth to one-fiftieth this degree of illumination was found ingas-lighted streets by Preece, depending on the proximity of the gaslamps. Image, Electric. An electrified point or system of points on one side of a surface whichwould produce on the other side of that surface the same electricalaction which the actual electrification of that surface really doesproduce. (Maxwell. ) The method of investigating the distribution of electricity by electricimages is due to Sir William Thomson. The conception is purely atheoretical one, and is of mathematical value and interest. 297 STANDARD ELECTRICAL DICTIONARY. Impedance. The ratio of any impressed electro-motive force to the current which itproduces in a conductor. For steady currents it is only the resistance. For variable currents it may include besides resistance inductance andpermittance. It is the sum of all factors opposing a current, both ohmicand spurious resistances. It is often determined and expressed as ohms. Synonym--Apparent Resistance--Virtual Resistance. Impedance, Oscillatory. The counter-electro-motive force offered to an oscillatory discharge, asthat of a Leyden jar. It varies with the frequency of the dischargecurrent. Synonym--Impulsive Impedance. Impressed Electro-motive Force. The electro-motive force expending itself in producing current inductionin a neighboring circuit. Impulse. (a) An electro-magnetic impulse is the impulse produced upon theluminiferous ether by an oscillatory discharge or other varying type ofcurrent; the impulse is supposed to be identical, except as regardswave-length, with a light wave. (b) An electro-motive impulse is the electro-motive force which rises sohigh as to produce an impulsive or oscillatory discharge, such as thatof a Leyden jar. Incandescence, Electric. The heating or a conductor to red, or, more etymologically, to whiteheat by the passage of an electric current. The practical conditions area high intensity of current and a low degree of conductance of theconductor relatively speaking. Inclination Map. A map showing the locus of equal inclination or dips of the magneticneedle. The map shows a series of lines, each one of which follows theplaces at which the dip of the magnetic needle is identical. The mapchanges from year to year. (See Magnetic Elements. ) Independence of Currents in Parallel Circuits. If a number of parallel circuits of comparatively high resistance aresupplied by a single generator of comparatively low resistance, thecurrent passed through each one will be almost the same whether a singleone or all are connected. Under the conditions named the currents arepractically independent of each other. [Transcriber's note: The current in each parallel branch depends on theresistance/impedance of that branch. Only if they all have the sameimpedance will the current be the same. ] Indicating Bell. An electric bell arranged to drop a shutter or disclose in some otherway a designating number or character when rung. 298 STANDARD ELECTRICAL DICTIONARY. Indicator. (a) An apparatus for indicating the condition of a distant element, suchas the water level in a reservoir, the temperature of a drying room orcold storage room or any other datum. They are of the most variedconstructions. (b) The receiving instrument in a telegraph system is sometimes thustermed. Indicator, Circuit. A galvanometer used to show when a circuit is active, and to give anapproximate measurement of its strength. It is a less accurate anddelicate form of instrument than the laboratory appliance. Inductance. The property of a circuit in virtue of which it exercises induction anddevelops lines of force. It is defined variously. As clear andsatisfactory a definition as any is the following, due to Sumpner andFleming: Inductance is the ratio between the total induction through acircuit to the current producing it. "Thus taking a simple helix of fiveturns carrying a current of two units, and assuming that 1, 000 lines offorce passed through the central turn, of which owing to leakage only900 thread the next adjacent on each side, and again only 800 throughthe end turns, there would be 800 + 900 + 1000 + 900 + 800, or 4, 400linkages of lines with the wire, and this being with 2 units of current, there would be 2, 200 linkages with unit current, and consequently theself-inductance of the helix would be 2, 200 centimetres. " (Kennelly. )Inductance, as regards its dimensions is usually reduced to a length, hence the last word of the preceding quotation. The practical unit of inductance is termed the henry, from Prof. JosephHenry; the secohm, or the quad or quadrant. The latter alludes to thequadrant of the earth, the value in length of the unit in question. [Transcriber's note: (L (di/dt) = V). A current changing at the rate ofone ampere per second through a one henry inductance produces one volt. A sinusoidal current produces a voltage 90 degrees ahead of the current, a cosine (the derivative of sine is cosine). One volt across one henrycauses the current to increase at one ampere per second. ] Induction, Coefficient of Self. The coefficient of self-induction of a circuit is the quantity ofinduction passing through it per unit current in it. If a given circuitis carrying a varying current it is producing a varying quantity ofmagnetic induction through itself. The quantity of induction through thecircuit due to its current is generally proportional to its current. Thequantity for unit current is the coefficient of self-induction. (Emtage. ) Induction, Cross. The induction of magnetic lines of force in a dynamo armature core bythe current passing around such armature. These lines in a symmetricaltwo pole machine are at right angles to the lines of force which wouldnormally extend across the space between the two magnet poles. The jointmagnetizing effect of the field and of the cross induction produces adistorted field between the poles . Synonym--Cross-magnetizing Effect. 299 STANDARD ELECTRICAL DICTIONARY. Induction, Electro-magnetic. The inter-reaction of electromagnetic lines of force with the productionof currents thereby. A current passing through a conductor establishes around it a field offorce representing a series of circular lines of force concentric withthe axis of the conductor and perpendicular thereto. These lines offorce have attributed to them, as a representative of their polarity, direction. This is of course purely conventional. If one is supposed tobe looking at the end of a section of conductor, assuming a current bepassing through it towards the observer, the lines of force will have adirection opposite to the motion of the hands of a watch. The idea ofdirection may be referred to a magnet. In it the lines of force areassumed to go from the north pole through the air or other surroundingdielectric to the south pole. Two parallel wires having currents passing through them in the samedirection will attract each other. This is because the oppositelydirected segments of lines of force between the conductors destroy eachother, and the resultant of the two circles is an approximation to anellipse. As lines of force tend to be as short as possible theconductors tend to approach each other to make the ellipse become of assmall area as possible, in other words to become a circle. If on the other hand the currents in the conductors are in oppositedirections the segments of the lines of force between them will havesimilar directions, will, as it were, crowd the intervening ether andthe wires will be repelled. Fig. 200. ATTRACTION OF CONDUCTORS CARRYING SIMILAR CURRENTS. By Ampére's theory of magnetism, (see Magnetism, Ampére's Theory of, ) amagnet is assumed to be encircled by currents moving in the directionopposite to that of the hands of a watch as the observer faces the northpole. A magnet near a wire tends to place the Ampérian currents parallelto the wire, and so that the portion of the Ampérian currents nearestthereto will correspond in direction with the current in the wire. 300 STANDARD ELECTRICAL DICTIONARY. This is the principle of the galvanometer. A number of methods ofmemoria technica have been proposed to remember it by. Thus if we imagine a person swimming with the current and always facingthe axis of the conductor, a magnetic needle held where the person issupposed to be will have its north pole deflected to the right hand ofthe person. Fig. 201. REPULSION OF CONDUCTORS CARRYING OPPOSITE CURRENTS. Again if we think of a corkscrew, which as it is turned screws itselfalong with the current, the motion of the handle shows the direction ofthe lines of force and the direction in which the north pole of a needleis deflected. This much is perhaps more properly electro-dynamics, butis necessary as a basis for the expression of induction. If a current is varied in intensity in one conductor it will induce atemporary current in another conductor, part of which is parallel to theinducing current and which conductor is closed so as to form a circuit. If the inducing current is decreased the induced current in the near andparallel portion of the other circuit will be of identical direction; ifincreased the induced current will be of opposite direction. This is easiest figured by thinking of the lines of force surroundingthe inducing conductor. If the current is decreased these can beimagined as receiving a twist or turn contrary to their normaldirection, as thereby establishing a turn or twist in the ethersurrounding the other wire corresponding in direction with the directionof the original lines of force, or what is the same thing, opposite indirection to the original twist. But we may assume that theestablishment of such a disturbance causes a current, which must begoverned in direction with the requirements of the new lines of force. The same reasoning applies to the opposite case. 301 STANDARD ELECTRICAL DICTIONARY. The general statement of a variable current acting on a neighboringcircuit also applies to the approach or recession of an unvaryingcurrent, and to the cutting of lines of force by a conductor at rightangles thereto. For it is evident that the case of a varying current isthe case of a varying number of lines of force cutting or being cut bythe neighboring conductor. As lines of force always imply a current, they always imply a direction of such current. The cutting of any linesof force by a closed conductor always implies a change of position withreference to all portions of such conductor and to the current andconsequently an induced current or currents in one or the otherdirection in the moving conductor. As the inducing of a current represents energy abstracted from that ofthe inducing circuit, the direction of the induced current is determinedby (Lenz's Law) the rule that the new current will increase alreadyexisting resistances or develop new ones to the disturbance of theinducing field. In saying that a conductor cutting lines of force at right angles toitself has a current induced in it, it must be understood that if not atright angles the right angle component of the direction of the wire actsin generating the current. The case resolves itself into the number oflines of force cut at any angle by the moving wire. The lines of force may be produced by a magnet, permanent or electro. This introduces no new element. The magnet may be referred, as regardsdirection of its lines of force, to its encircling currents, actual orAmpérian, and the application of the laws just cited will cover allcases. Induction, Coefficient of Mutual. The coefficient of mutual induction of two circuits is the quantity ofmagnetic induction passing through either of them per unit current inthe other. (Emtage. ) It is also defined as the work which must be doneon either circuit, against the action of unit current in each, to takeit away from its given position to an infinite distance from the other;and also as the work which would be done by either circuit on the otherin consequence of unit current in each, as the other moves from aninfinite distance to its given position with respect to the otherconductor. It depends on the form, size, and relative position of thetwo circuits; and on the magnetic susceptibilities of neighboringsubstances. The ether surrounding two circuits of intensity i' and i" must possessenergy, expressible (Maxwell) as 1/2 L i2 + M i i + 1/2 N i12. It can beshown that M i i1 in any given position of the two circuits isnumerically equal (1) to the mutual potential energy of the two circuits(2) to the number of lines of induction, which being due to A, pass fromA through B, or equally being due to B, pass from B through A, and M isstyled the coefficient of mutual induction. (Daniell. ) 302 STANDARD ELECTRICAL DICTIONARY. Induction, Electrostatic. An electrostatic charge has always an opposite and bound charge. Thismay be so distributed as not to be distinguishable, in which case thecharge is termed, incorrectly but conventionally, a free charge. Butwhen a charge is produced an opposite and equal one always is formed, which is the bound charge. The region between the two charges andpermeated by their lines of force, often curving out so as to embrace avolume of cross-sectional area larger than the mean facing area of theexcited surfaces, is an electrostatic field of force. The establishingof an electrostatic field, and the production of a bound charge areelectrostatic induction. An insulated conductor brought into such a field suffers aredistribution of its electricity, or undergoes electrostatic induction. The parts nearest respectively, the two loci of the original and thebound charges, are excited oppositely to such charges. The conductorpresents two new bound charges, one referred to the original charge, theother to the first bound charge. Induction, Horizontal. In an iron or steel ship the induction exercised upon the compass needleby the horizontal members of the structure, such as deck-beams, whenthey are polarized by the earth's magnetic induction. This inductiondisappears four times in swinging a ship through a circle; deviation dueto it is termed quadrantal deviation. (See Deviation, Quadrantal. ) Induction, Lateral. A term formerly used to express the phenomenon of the alternativedischarge of a Leyden jar or other oscillatory discharge of electricity. (See Discharge, Alternative. ) Induction, Magnetic. The magnetization of iron or other paramagnetic substance by a magneticfield. On account of its permeability or multiplying power for lines of force, a paramagnetic body always concentrates lines of force in itself ifplaced in a magnetic field, and hence becomes for the time being amagnet, or is said to be polarized. As the tendency of lines of force is to follow the most permeable path, a paramagnetic bar places itself lengthwise or parallel with theprevailing direction of the lines of force so as to carry them as far ontheir way as possible. Every other position of the bar is one ofunstable equilibrium or of no equilibrium. The end of the bar where thelines of force enter (see Lines of Force) is a south pole and isattracted towards the north pole of the magnet. The production of magnetic poles under these conditions in the bar isshown by throwing iron filings upon it. They adhere to both ends but notto the middle. Induction, Mutual, Electro-magnetic. The induction due to two electric currents reacting on each other. 303 STANDARD ELECTRICAL DICTIONARY. Induction, Mutual, Electrostatic. A charged body always induces a charge upon any other body near it; andthe same charge in the second body will induce the other charge in thefirst body if the latter is unexcited. In other words the second body'sinduction from the first is the measure of the charge the second wouldrequire to induce in the first its own (the second's) induced charge. This is the law of mutual electrostatic induction. Induction, Open Circuit. Inductive effects produced in open circuits. By oscillatory discharges adischarge can be produced across a break in a circuit otherwisecomplete. The requirements for its production involve a correspondenceor relation of its dimensions to the inducing discharge. The whole isanalogous to the phenomena of sound resonators and sympatheticvibrations. Synonym--Oscillatory induction. Induction, Self-. (a) A phenomenon of electric currents analogous to the inertia ofmatter. Just as water which fills a pipe would resist a sudden change inits rate of motion, whether to start from rest, to cease or decrease itsmotion, so an electric current requires an appreciable time to start andstop. It is produced most strongly in a coiled conductor, especially ifa core of iron is contained within it. As in the case of two parallel wires, one bearing currents which vary, momentary currents are induced in the other wire, so in a singleconductor a species of inertia is found which retards and prolongs thecurrent. If a single conductor is twisted into a helix or correspondingshape, its separate turns react one on the other in accordance with thegeneral principles of electromagnetic induction. (See Induction, Electro-magnetic. ) Thus when a current is suddenly formed the coilsacting upon each other retard for an instant its passage, producing theeffect of a reverse induced current or extra current opposing theprincipal current. Of course no extra current is perceptible, but onlythe diminution. When the current is passing regularly and the current isbroken, the corresponding action prolongs the current or ratherintensifies it for an instant, producing the true extra current. This iscurrent self-induction. [Transcriber's note: See inductance. ] Synonyms--Electric Inertia--Electro-dynamic Capacity. (b) A permanent magnet is said to tend to repel its own magnetism, andthus to weaken itself; the tendency is due to magnetic self-induction. Induction Sheath. In the brush dynamo a thin sheet of copper surrounding the magnet coreswith edges soldered together. The winding is outside of it. Its objectis to absorb extra currents set up by variations in magnetic intensityin the cores. These currents otherwise would circulate in the cores. 304 STANDARD ELECTRICAL DICTIONARY. Induction, Unit of Self-. The unit of self-induction is the same as that of induction in general. It is the henry, q. V. Induction, Unipolar. Induction produced in a conductor which continuously cuts the lines offorce issuing from one pole of a magnet. As the lines of force arealways cut in the same sense a continuous and constant direction currentis produced. Induction, Vertical. In an iron or steel ship the induction or attraction exercised in thecompass by vertical elements of the structure. Such vertical masses ofiron in the northern hemisphere would have their upper ends polarized assouth poles, and would affect the magnet as soon as the vessel swung outof the magnetic meridian. Thus this induction disappears twice inswinging a ship through a complete circle; deviation due to it is termedsemi-circular deviation. (See Deviation, Semi-circular. ) Fig. 202. INDUCTOR DYNAMO. Inductophone. A method of train telegraphy. The train carries a circuit including acoil, and messages are picked up by it from coils along the line intowhich an alternating current is passed. A telephone is used as areceiver in place of a sounder or relay. The invention, neverpractically used, is due to Willoughby Smith. 305 STANDARD ELECTRICAL DICTIONARY. Inductor. (a) In a current generator a mass of iron, generally laminated, which ismoved past a magnet pole to increase the number of lines of forceissuing therefrom. It is used in inductor dynamos. (See DynamoInductor. ) In the cut Fig. 202, of an inductor dynamo i, i, are thelaminated inductors. (b) In influence machines the paper or tinfoil armatures on which theelectrification is induced. Inertia. A force in virtue of which every body persists in its state of motion orrest except so far as it is acted on by some force. Inertia, Electro-magnetic. This term is sometimes applied to the phenomena of self-induction, orrather to the cause of these phenomena. Infinity Plug. A plug in a resistance box, which on being pulled out of its seat opensthe circuit or makes it of infinite resistance. The plug seats itselfbetween two brass plates which are not connected with each other in anyway. The other plates are connected by resistance coils of varyingresistance. Influence, Electric. Electric induction, which may be either electrostatic, current, orelectro-magnetic. Insolation, Electric. Exposure to powerful arc-light produces effects resembling those ofsun-stroke. The above term or the term "electric sun-stroke" has beenapplied to them. [Transcriber's note: Operators of arc welders are prone to skin cancerfrom ultra violet rays if not properly protected. ] Installation. The entire apparatus, buildings and appurtenances of a technical ormanufacturing establishment. An electric light installation, forinstance, would include the generating plant, any special buildings, themains and lamps. Insulating Stool. A support for a person, used in experiments with static generators. Ithas ordinarily a wooden top and glass legs. It separates one standing onit from the earth and enables his surface to receive an electrostaticcharge. This tends to make his hair stand on end, and anyone on thefloor who touches him will receive a shock. Insulating Tape. Prepared tape used in covering the ends of wire where stripped formaking joints. After the stripped ends of two pieces are twistedtogether, and if necessary soldered and carefully cleaned of solderingfluid, they may be insulated by being wound with insulating tape. The tape is variously prepared. It may be common cotton or other tapesaturated with any insulating compound, or may be a strip of guttapercha or of some flexible cement-like composition. 306 STANDARD ELECTRICAL DICTIONARY. Insulating Varnish. Varnish used to coat the surface of glass electrical apparatus, toprevent the deposition of hygrometric moisture, and also in theconstruction of magnetizing and induction coils and the like. Shellacdissolved in alcohol is much used. Gum copal dissolved in ether isanother. A solution of sealing wax in alcohol is also used. If appliedin quantities these may need baking to bring about the last drying. (SeeShellac Varnish. ) Insulator. (a) Any insulating substance. (b) A telegraph or line insulator for telegraph wires. (See Insulator, Line or Telegraph. ) Synonyms--Dielectric--Non-conductor. Insulator Cap. A covering or hood, generally of iron, placed over an insulator toprotect it from injury by fracture with stones or missiles. Insulator, Fluid. (a) For very high potentials, as in induction coils or alternatingcircuits, fluid insulators, such as petroleum or resin oil, have beenused. Their principal merit is that if a discharge does take placethrough them the opening at once closes, so that they are self-healing. (b) Also a form of telegraph or line insulator in which the lower rim isturned up and inwards, so as to form an annular cup which is filled withoil. Insulator, Line or Telegraph. A support often in the shape of a collar or cap, for a telegraph orother wire, made of insulating material. Glass is generally used in theUnited States, porcelain is adopted for special cases; pottery or stoneware insulators have been used a great deal in other countries. Sometimes the insulator is an iron hook set into a glass screw, which isinserted into a hole in a telegraph bracket. Sometimes a hook is causedto depend from the interior of an inverted cup and the space between theshank of the hook and cup is filled with paraffine run in while melted. Insulators are tested by measuring their resistance while immersed in avessel of water. Intensity. Strength. The intensity of a current or its amperage or strength; the intensity orstrength of a magnetic field or its magnetic density; the intensity orstrength of a light are examples of its use. In the case of dynamicelectricity it must be distinguished from tension. The lattercorresponds to potential difference or voltage and is not an attributeof current; intensity has no reference to potential and is acharacteristic of current. Intensity of a Magnetic Field. The intensity of a magnetic field at any point is measured by the forcewith which it acts on a unit magnet pole placed at that point. Henceunit intensity of field is that intensity of field which acts on a unitpole with a force of one dyne. (S. P. Thomson. ) (See Magnetic Lines ofForce. ) 307 STANDARD ELECTRICAL DICTIONARY. Intercrossing. Crossing a pair of conductors of a metallic circuit from side to side toavoid induction from outside sources. Intermittent. Acting at intervals, as an intermittent contact, earth, or grounding ofa telegraph wire. Interpolar Conductor. A conductor connecting the two poles of a battery or current generator;the external circuit in a galvanic circuit. Interpolation. A process used in getting a closer approximation to the truth from twovarying observations, as of a galvanometer. The process varies fordifferent cases, but amounts to determining an average or deducing aproportional reading from the discrepant observed ones. Interrupter. A circuit breaker. It may be operated by hand or be automatic. (SeeCircuit Breaker--Circuit Breaker, Automatic--and others. ) Interrupter, Electro-magnetic, for a Tuning Fork. An apparatus for interrupting a current which passes through anelectromagnet near and facing one of the limbs of a tuning fork. Thecircuit is made and broken by the vibrations of another tuning forkthrough which the current passes. The second one is thus made tovibrate, although it may be very far off and may not be in exact unisonwith the first. The first tuning fork has a contact point on one of itslimbs, to close the circuit; it may be one which dips into a mercurycup. Intrapolar Region. A term in medical electricity, denoting the part of a nerve throughwhich a current is passing. Ions. The products of decomposition produced in any given electrolysis aretermed ions, the one which appears at the anode or negative electrode isthe anion. The electrode connected to the carbon or copper plate of awet battery is an anode. Thus in the electrolysis of water oxygen is theanion and hydrogen is termed the kation. In this case both anion andkation are elements. In the decomposition of copper sulphate the anionis properly speaking sulphion (S O4), a radical, and the kation iscopper, an element. Electro-negative elements or radicals are anions, such as oxygen, sulphion, etc. , while electro-positive ones are kations, such as potassium. Again one substance may be an anion referred to onebelow it and a kation referred to one above it, in the electro-chemicalseries, q. V. Anion means the ion which goes to the anode or positiveelectrode; kation, the ion which goes to the kathode or negativeelectrode. [Transcriber's note: An ion is an atom or molecule that has lost orgained one or more valence electrons, giving it a positive or negativeelectrical charge. A negatively charged ion, with more electrons thanprotons in its nuclei, is an anion. A positively charged ion, with fewerelectrons than protons, is a cation. The electron was discovered fiveyears after this publication. ] 308 STANDARD ELECTRICAL DICTIONARY. Iron. A metal; one of the elements; symbol, Fe; atomic weight, 56;equivalent, 28 and 14, ; valency, 4 and 2. It is a conductor of electricity. The following data are at0° C. 32° F. , with annealed metal. Specific Resistance, 9. 716 microhms. Relative Resistance. 6. 460 Resistance of a wire, (a) 1 foot long weighing 1 grain, 1. 085 ohms. (b) 1 foot long 1/1000 inch thick, 58. 45 " (c) 1 meter long weighing 1 gram, . 7570 " (d) 1 meter long, 1 millimeter thick, . 1237 "Percentage increase in resistance per degree C. (1. 8° F. ) at about 20° C. (68°F. ), about 0. 5 per cent. Resistance of a 1 inch cube, 3. 825 microhms. Electro-chemical equivalent (Hydrogen = . 0105), . 147 and . 294 Iron, Electrolytic. Iron deposited by electrolytic action. Various baths are employed forits formation. (See Steeling. ) It has very low coercive power, onlyseven to ten times that of nickel. Ironwork Fault of a Dynamo. A short circuiting of a dynamo by, or any connection of its coils with, the iron magnet cores or other iron parts. Isochronism. Equality of periodic time; as of the times of successive beats of atuning fork, or of the times of oscillations of a pendulum. Isoclinic Lines. The lines denoting the locus of sets of equal dips or inclinations ofthe magnetic needle upon the earth's surface, the magnetic parallels, q. V. These lines are very irregular. (See Magnetic Elements. ) Isoclinic Map. A map showing the position of isoclinic lines. Isodynamic Lines. Lines marking the locus of places of equal magnetic intensity on theearth's surface. (See Magnetic Elements, Poles of Intensity. ) Isodynamic Map. A map showing the position of isodynamic lines. (See Poles ofIntensity. ) Isogonic Lines. Lines on a map marking the locus of or connecting those points where thedeclination or variation of the magnetic needle is the same. (SeeMagnetic Elements--Declination of Magnetic Needle. ) Synonyms--Isogonal Lines--Halleyan Lines. 309 STANDARD ELECTRICAL DICTIONARY. Isogonic Map. A map showing the isogonic lines. On such a map each line ischaracterized and marked with the degrees and direction of variation ofthe compass upon itself. Synonym--Declination Map. Isolated Plant, Distribution or Supply. The system of supplying electric energy by independent generatingsystems, dynamo or battery, for each house, factory or other place, ascontra-distinguished from Central Station Distribution or Supply. Isotropic. (Greek, equal in manner. ) Having equal properties in all directions; the reverse of anisotropic, q. V. Thus a homogeneous mass of copper or silver has the same specificresistance in all directions and is an isotropic conductor. Glass hasthe same specific inductive capacity in all directions and is anisotropic medium or dielectric. The same applies to magnetism. Iron isan isotropic paramagnetic substance. (See Anisotropic. ) The term appliesto other branches of physics also. I. W. G. Contraction for Indian Wire Gauge--the gauge adopted in British India. J. Symbol for the unit joule, the unit of electric energy. Jacobi's Law. A law of electric motors. It states that the maximum work of a motor isperformed when the counter-electromotive force is equal to one-half theelectro-motive force expended on the motor. Jewelry. Small incandescent lamps are sometimes mounted as articles of jewelry inscarf-pins or in the hair. They may be supplied with current fromstorage or from portable batteries carried on the person. Joint, American Twist. A joint for connecting telegraph wires, especially aerial lines. Itsconstruction is shown in the cut. The end of each wire is closely woundaround the straight portion of the other wire for a few turns. Fig. 203. AMERICAN TWIST JOINT. 310 STANDARD ELECTRICAL DICTIONARY. Joint, Britannia. A joint for uniting the ends of telegraph and electric wires. The endsof the wires are scraped clean and laid alongside each other for twoinches, the extreme ends being bent up at about right angles to thewire. A thin wire is wound four or five times around one of the wires, back of the joint, the winding is then continued over the lappedportion, and a few more turns are taken around the other single wire. The whole is then soldered. Fig. 204. BRITANNIA JOINT. Joint, Butt. A joint in belting or in wire in which the ends to be joined are cut offsquare across, placed in contact and secured. It ensures even runningwhen used in belting. Any irregularity in thickness of a belt affectsthe speed of the driven pulley. As dynamos are generally driven bybelts, and it is important to drive them at an even speed to preventvariations in the electro-motive force, butt joints should be used onbelting for them, unless a very perfect lap joint is made, which doesnot affect either the thickness or the stiffness of the belt. When a butt joint is used in wire a sleeve may be used to receive theabutting ends, which may be secured therein by soldering. This speciesof joint has been used on lightning rods and may more properly be termeda sleeve joint. Joint, Lap. (a) In belting a joint in which the ends are overlapped, and riveted orotherwise secured in place. If made without reducing the thickness ofthe ends it is a bad joint for electrical work, as it prevents evenrunning of machinery to which it is applied. Hence dynamo belts shouldbe joined by butt joints, or if by lap joints the ends should be shavedoff so that when joined and riveted, there will be no variation in thethickness of the belt. (b) In wire lap joints are made by overlapping the ends of the wire andsoldering or otherwise securing. The Britannia joint (see Joint, Britannia, ) may be considered a lap-joint. Joint, Marriage. A joint for stranded conductors used for Galende's cables. It is madesomewhat like a sailor's long splice. Each one of the strands is woundseparately into the place whence the opposite strand is unwound and theends are cut off so as to abutt. In this way all are smoothly laid inplace and soldering is next applied. Fig. 205. MARRIAGE JOINT. 311 STANDARD ELECTRICAL DICTIONARY. Joint, Sleeve. A joint in electric conductors, in which the ends of the wires areinserted into and secured in a metallic sleeve or tube, whose internaldiameter is just sufficient to admit them. Joint, Splayed. The method of joining the ends of stranded conductors. The insulatingcovering is removed, the wires are opened out, and the center wire, heart or core of the cable is cut off short. The two ends are broughttogether, the opened out wires are interlaced or crotched like thefingers of the two hands, and the ends are wound around the body of thecable in opposite directions. The joint is trimmed and well soldered. Tinned wire with rosin flux for the soldering is to be recommended. Insulating material is finally applied by hand, with heat if necessary. Joints in Belts. Belt-joints for electric plants where the belts drive dynamos should bemade with special care. The least inequality affects the electro-motiveforce. Butt joints are, generally speaking, the best, where the ends ofthe belt are placed in contact and laced. Lap-joints are made byoverlapping the belt, and unless the belt is carefully tapered so as topreserve uniform strength, the speed of the dynamo will vary and alsothe electromotive force. Joulad. A name proposed to be substituted for "joule, " q. V. It has not beenadopted. Joule. This term has been applied to several units. (a) The practical C. G. S. Unit of electric energy and work--thevolt-coulomb. It is equal to 1E7 ergs--0. 73734 foot pound. --. 00134 horsepower seconds. A volt-ampere represents one joule per second. (b) It has also been used as the name of the gram-degree C. Thermalunit--the small calorie. Synonym--Joulad. Joule Effect. The heating effect of a current passing through a conductor. It varieswith the product of the resistance by the square of the current, or with(C^2)*R. Joule's Equivalent. The mechanical equivalent of heat, which if stated in foot-pounds perpound-degree F. Units, is 772 (772. 55). (See Equivalents. ) Junction Box. In underground distribution systems, an iron casing or box in which thefeeders and mains are joined, and where other junctions are made. Synonym--Fishing Box. K. The symbol for electrostatic capacity. Kaolin. A product of decomposition of feldspar, consisting approximately ofsilica, 45, alumina, 40, water, 15. It was used in electric candles ofthe Jablochkoff type as a constituent of the insulating layer orcolombin. Later it was abandoned for another substance, as it was foundthat it melted and acted as a conductor. 312 STANDARD ELECTRICAL DICTIONARY. Kapp Line of Force. A line of force proposed by Kapp. It is equal to 6, 000 C. G. S. Lines offorce, and the unit of area is the square inch. Unfortunately it hasbeen adopted by many manufacturers, but its use should be discouraged, as it is a departure from the uniform system of units. One Kapp line per square inch = 930 C. G. S. Lines per squarecentimeter. Kathelectrotonus. A term used in medical electricity or electro-therapeutics to indicatethe increased functional activity induced in a nerve by the proximity ofthe kathode of an active circuit which is completed through the nerve. The converse of anelectrotonus. Kathode. The terminal of an electric circuit whence an electrolyzing currentpasses from a solution. It is the terminal connected to the zinc plateof a primary battery. Kathodic Closure Contraction. A term in electro-therapeutics; the contractions near where the kathodeof an active circuit is applied to the body, which are observed at theinstant when the circuit is closed. Kathodic Duration Contraction. A term in electro-therapeutics; the contraction near where the kathodeof an active circuit is applied to the body for a period of time. K. C. C. Abbreviation for Kathodic Closure Contraction, q. V. K. D. C. Abbreviation for Kathodic Duration Contraction, q. V. Keeper. A bar of soft iron used to connect the opposite poles of a horseshoemagnet or the opposite poles of two bar magnets placed side by side. Itis designed to prevent loss of magnetism. The armature of a horseshoemagnet is generally used as its keeper. For bar magnets a keeper is usedfor each end, the magnets being laid side by side, with their poles inopposite direction but not touching, and a keeper laid across at eachend connecting the opposite poles. Kerr Effect. The effect of an electrostatic field upon polarized light traversing adielectric contained within the field. (See Electrostatic Refraction. ) Kerr's Experiment. Polarized light reflected from the polished face of a magnet pole hasits plane of polarization rotated; when it is reflected from the northpole the rotation is from left to right. 313 STANDARD ELECTRICAL DICTIONARY. Key. A switch adapted for making and breaking contact easily when worked byhand, as a Morse telegraph key. Key Board. A board or tablet on which keys or switches are mounted. Key-board. (a) A switch board, q. V. (b) A set of lettered keys similar to those of a typewriter employed insome telegraph instruments. As each key is depressed it produces thecontact or break requisite for the sending of the signal correspondingto the letter marked upon the key. The signal in printing telegraphs, onwhich such key-boards are used, is the reprinting of the letter at thedistant end of the line. Key, Bridge. A key for use with a Wheatstone Bridge, q. V. It is desirable to firstsend a current through the four arms of the bridge in using it fortesting resistances and then through the galvanometer, because it takesa definite time for the current to reach its full strength. This isespecially the case if the element being measured has high staticcapacity, as a long ocean cable. If the galvanometer connections werecompleted simultaneously with the bridge connections a momentary swingwould be produced even if the arms bore the proper relation to eachother. This would cause delay in the testing. A bridge key avoids thisby first connecting the battery circuit through the arms of the bridge, and then as it is still further depressed the galvanometer circuit iscompleted. 314 STANDARD ELECTRICAL DICTIONARY. Fig. 206. CHARGE AND DISCHARGE KEY Key, Charge and Discharge. A key for use in observing the discharge of a condenser immediatelyafter removing the battery. In one typical form it has two contacts, onebelow and one above, and being a spring in itself is pressed up againstthe upper one. Connections are so made that when in its upper positionit brings the two coatings of the condenser in circuit with thegalvanometer. When depressed it does the same for a battery. In use itis depressed and suddenly released when the galvanometer receives thefull charge, before there has been time for leakage. This is one methodof connection illustrating its principle. In the cut L is the spring-key proper. S2, is the upper contact screwagainst which the spring normally presses. In this position thegalvanometer G is in circuit with the opposite coatings of the condenserC. On depressing the contact S2, is broken and S1, is made. This bringsthe battery B in circuit with the condenser coatings. On releasing thekey it springs up and the galvanometer receives the effect of the chargeof the condenser as derived from the battery. Key, Double Contact. A key arranged to close two distinct circuits, holding the first closeduntil the second is completed. It is used for Wheatstone bridge work. Key, Double Tapper. A telegraph key giving contacts alternately for currents in oppositedirections, used in needle telegraphy. Key, Increment. A key for use in duplex and quadruplex telegraphy. Its action is toincrease the line current, not merely to suddenly turn current into it. 315 STANDARD ELECTRICAL DICTIONARY. Fig. 207. KEMPE'S DISCHARGE KEY. Key, Kempe's Discharge. A key giving a charging, discharging and insulating connection, forstatic condenser work. Referring to the cut l is a lever or spring withupper discharging contact s, and lower charging contact s'. In use it ispressed down by the insulating handle or finger piece C, until caught bythe hook attached to the key I. This hook is lower down than that on thekey D, and holds it in contact with the charging contact piece S'. Onpressing the key I, marked or designated "Insulate, " it springs up, breaks contact at S', and catching against the hook on D, which key isdesignated "Discharge, " remains insulated from both contacts; next onpressing D it is released and springs up and closes the dischargecontact S. It is a form of charge and discharge key. (See Key, Chargeand Discharge. ) Key, Magneto-electric. A telegraph key whose movements operate what is virtually a smallmagneto-generator, so as to produce currents of alternating direction, one impulse for each motion of the key. It is employed for telegraphingwithout a line battery, a polarized relay being used. In one very simpleform a key is mounted on a base with a permanent magnet and connected tothe armature, so that when the key is pressed downwards it draws thearmature away from the poles of the magnet. If the magnet or itsarmature is wound with insulated wire this action of the key will causeinstantaneous currents to go through a circuit connected to the magnetor armature coils. Fig. 208. SIEMENS' MAGNETO-ELECTRIC KEY. In Siemens & Halske's key an H armature E is pivoted between the poles NS, of a powerful compound horseshoe magnet, G G. It is wound with finewire and a key handle H is provided for working it. In its normalposition the handle is drawn upward, and the end S S of the armaturecore is in contact with the south pole S of the permanent magnet, andthe end D D with the north pole. This establishes the polarity of thearmature. On depressing the key the contacts are broken and in theirplace the end D D comes in contact with the south pole and the end S Swith the north pole. This suddenly reverses the polarity of the armatureand sends a momentary current through the armature coil which is incircuit with the line. The cut only shows the principle of the key, whose construction is quite complicated. 316 STANDARD ELECTRICAL DICTIONARY. Key, Make and Break. An ordinary electric key, usually making a contact when depressed, andrising by spring action when released, and in its rise breaking thecontact. Fig. 209. PLUG KEY Key, Plug. An appliance for closing a circuit. Two brass blocks are connected tothe terminals, but are disconnected from each other. A brass plugslightly coned or with its end split so as to give it spring action isthrust between the blocks to complete the circuit. It is used inResistance coils and elsewhere. (See Coil, Resistance. ) Grooves areformed in the blocks to receive the plug. Key, Reversing. (a) A double key, arranged so that by depressing one key a current flowsin one direction, and by depressing the other a current flows in theopposite direction. It is used in connection with a galvanometer inexperimental, testing or measuring operations. (b) A key effecting the same result used in quadruplex telegraphy. Key, Sliding-Contact. A name given to the key used for making instantaneous contacts with themetre wire of a metre bridge, q. V. The name is not strictly correct, because it is important that there should be no sliding contact made, asit would wear out the wire and make it of uneven resistance. It is a key which slides along over the wire and which, when depressed, presses a platinum tipped knife edge upon the wire. On being releasedfrom pressure the key handle springs up and takes the knife edge off thewire. This removal is essential to avoid wearing the wire, whoseresistance per unit of length must be absolutely uniform. Key, Telegraph. The key used in telegraphy for sending currents as desired over theline. It consists of a pivoted lever with finger piece, which lever whendepressed makes contact between a contact point on its end and astationary contact point on the base. This closes the circuit throughthe line. When released it springs up and opens the line circuit. Kilo. A prefix to the names of units; it indicates one thousand times, askilogram, one thousand grams. A few such units are given below. Kilodyne. A compound unit; one thousand dynes. (See Dyne. ) Kilogram. A compound unit; one thousand grams; 2. 2046 pounds avds. 317 STANDARD ELECTRICAL DICTIONARY. Kilojoule. A compound unit; one thousand joules, q. V. Kilometer. A compound unit; one thousand meters; 3280. 899 feet; 0. 621382 statutemiles. (See Meter. ) Kilowatt. A compound unit; one thousand watts, q. V. Kine. An absolute or C. G. S. Unit of velocity or rate of motion; onecentimeter per second; proposed by the British Association. Kirchoff's Laws. These relate to divided circuits. I. When a steady current branches, the quantity of electricity arrivingby the single wire is equal to the quantity leaving the junction by thebranches. The algebraical sum of the intensities of the currents passingtowards (or passing from) the junction is equal to zero; Summation(C) =0 (Daniell. ) In the last sentence currents flowing towards the point areconsidered of one sign and those flowing away from it of the other. II. In a metallic circuit comprising within it a source of permanentdifference of potential, E, the products of the intensity of the currentwithin each part of the circuit into the corresponding resistance are, if the elements of current be all taken in cyclical order together, equal to E; Summation(C * r) =E. In a metallic circuit in which there isno source of permanent difference of potential E = 0, and Summation(C *r) = 0. This law applies to each several mesh of a wire network as well as to asingle metallic loop, and it holds good even when an extraneous currentis passed through the loop. (Daniell. ) In this statement of the two laws E stands for electro-motive force, Cfor current intensity; and r for resistance of a single member of thecircuit. [Transcriber's note: These laws may be restated as: At any point in ansteady-state electrical circuit, the directed sum of currents flowingtowards that point is zero. The directed sum of the electrical potentialdifferences around any closed circuit is zero. ] Knife-edge Suspension. The suspension of an object on a sharp edge of steel or agate. The knifeedge should abut against a plane. The knife edge is generally carried bythe poised object. Its edge then faces downward and on the support oneor more plane or approximately plane surfaces are provided on which itrests. In the ordinary balance this suspension can be seen. It issometimes used in the dipping needle. It is applied in cases where vertical oscillations are to be providedfor. Knot. The geographical mile; a term derived from the knots on the log line, used by navigators. It is equal to 6, 087 feet. Synonyms--Nautical Mile--Geographical Mile. [Transcriber's note: A knot is a velocity, 1 nautical mile per hour, nota distance. The contemporary definition is: 1 international knot = 1nautical mile per hour = 1. 852 kilometres per hour = 1. 1507794 miles perhour = 0. 51444444 meters per second = 6076. 1152 feet per hour. ] 318 STANDARD ELECTRICAL DICTIONARY. Kohlrausch's Law. A law of the rate of travel of the elements and radicals in solutionsunder the effects of electrolysis. It states that each element under theeffects of electrolysis has a rate of travel for a given liquid, whichis independent of the element with which it was combined. The rates oftravel are stated for different elements in centimeters per hour for apotential difference of one or more volts per centimeter of path. [Friedrich Wilhelm Georg Kohlrausch (1840-1910)] Kookogey's Solution. An acid exciting and depolarizing solution for a zinc-carbon couple, such as a Bunsen battery. Its formula is: Potassium bichromate, 227parts; water, boiling, 1, 134 parts; while boiling add very carefully andslowly 1, 558 parts concentrated sulphuric acid. All parts are by weight. Use cold. Krizik's Cores. Cores of iron for use with magnetizing coils, q. V. They are so shaped, the metal increasing in quantity per unit of length, as the centre isapproached, that the pull of the excited coil upon them will as far aspossible be equal in all positions. A uniform cylinder is attracted withvarying force according to its position; the Krizik bars or cores areattracted approximately uniformly through a considerable range. L. Symbol for length and also for the unit of inductance or coefficient ofinduction, because the dimensions of inductance are length. Lag, Angle of. (a) The angle of displacement of the magnetic axis of an armature of adynamo, due to its magnetic lag. The axis of magnetism is displaced inthe direction of rotation. (See Magnetic Lag. ) (b) The angle expressing the lag of alternating current andelectro-motive force phases. Laminated. Adj. Made up of thin plates, as a laminated armature core or converter core. Lamination. The building up of an armature core or other thing out of plates. Thecores of dynamo armatures or of alternating current converters are oftenlaminated. Thus a drum armature core may consist of a quantity of thiniron discs, strung upon a rod and rigidly secured, either with orwithout paper insulation between the discs. If no paper is used the filmof oxide on the iron is relied on for insulation. The object oflamination is to break up the electrical continuity of the core, so asto avoid Foucault currents. (See Currents, Foucault. ) The laminationsshould be at right angles to the direction of the Foucault currentswhich would be produced, or in most cases should be at right angles tothe active parts of the wire windings. 319 STANDARD ELECTRICAL DICTIONARY. Lamination of Armature Conductors. These are sometimes laminated to prevent the formation of eddy currents. The lamination should be radial, and the strips composing it should beinsulated from each other by superficial oxidation, oiling orenamelling, and should be united only at their ends. Fig. 210. PILSEN ARC LAMP. Lamp, Arc. A lamp in which the light is produced by a voltaic arc. Carbonelectrodes are almost universally employed. Special mechanism, operatingpartly by spring or gravity and partly by electricity, is employed toregulate the distance apart of the carbons, to let them touch when nocurrent passes, and to separate them when current is first turned on. The most varied constructions have been employed, examples of which willbe found in their places. Lamps may in general be divided into classesas follows, according to their regulating mechanism and other features: (a) Single light regulators or monophotes. Lamps through whoseregulating mechanism the whole current passes. These are only adapted towork singly; if several are placed in series on the same circuit, theaction of one regulator interferes with that of the next one. (b) Multiple light regulators or polyphotes. In these the regulatingmechanism and the carbons with their arc are in parallel; the regulatingdevice may be a single magnet or solenoid constituting a derived orshunt-circuit lamp, or it may include two magnets working differentiallyagainst or in opposition to each other constituting a differential lamp. 320 STANDARD ELECTRICAL DICTIONARY. (c) Lamps with fixed parallel carbons termed candles (q. V. , of varioustypes). (d) Lamps without regulating mechanism. These include lamps withconverging carbons, whose object was to dispense with the regulatingmechanism, but which in some cases have about as much regulatingmechanism as any of the ordinary arc lamps. Lamp, Contact. A lamp depending for its action on loose contact between two carbonelectrodes. At the contact a species of incandescence with incipientarcs is produced. One of the electrodes is usually flat or nearly so, and the other one of pencil shape rests upon it. Lamp, Differential Arc. An arc lamp, the regulation of the distance between whose carbonsdepends on the differential action of two separate electrical coils. Thediagram illustrates the principle. The two carbons are seen in black;the upper one is movable, The current arrives at A. It divides, and thegreater part goes through the low resistance coil M to a contact rollerr, and thence by the frame to the upper carbon, and through the arc andlower carbon to B, where it leaves the lamp. A smaller portion of thecurrent goes through the coil M1 of higher resistance and leaves thelamp also at B. A double conical iron core is seen, to which the uppercarbon holder is attached. This is attracted in opposite directions bythe two coils. If the arc grows too long its resistance increases andthe coil M1 receiving more current draws it down and thus shortens thearc. If the arc grows too short, its resistance falls, and the coil Mreceives more current and draws the core upwards, thus lengthening thearc. This differential action of the two cores gives the lamp its name. R is a pulley over which a cord passes, one end attached to the core andthe other to a counterpoise weight, W. Fig. 211. DIAGRAM OF THE PILSEN DIFFERENTIAL ARC LAMP. 321 STANDARD ELECTRICAL DICTIONARY. Lamp, Holophote. A lamp designed for use alone upon its own circuit. These have theregulating mechanism in series with the carbon and arc, so that thewhole current goes through both. (See Lamp, Arc. ) Synonym--Monophote Lamp. Lamp-hour. A unit of commercial supply of electric energy; the volt-coulombsrequired to maintain an electric lamp for one hour. A sixteen-candlepower incandescent lamp is practically the lamp alluded to, and requiresabout half an ampere current at 110 volts, making a lamp-hour equal toabout 198, 000 volt-coulombs. [Transcriber's note: 0. 55 KW hours. ] Lamp, Incandescent. An electric lamp in which the light is produced by heating to whitenessa refractory conductor by the passage of a current of electricity. It isdistinguished from an arc lamp (which etymologically is also anincandescent lamp) by the absence of any break in the continuity of itsrefractory conductor. Many different forms and methods of constructionhave been tried, but now all have settled into approximately the sametype. The incandescent lamp consists of a small glass bulb, called thelamp-chamber, which is exhausted of air and hermetically sealed. Itcontains a filament of carbon, bent into a loop of more or less simpleshape. This shape prevents any tensile strain upon the loop and alsoapproximates to the outline of a regular flame. Fig. 212. INCANDESCENT ELECTRIC LAMP. 322 STANDARD ELECTRICAL DICTIONARY. The loop is attached at its ends to two short pieces of platinum wire, which pass through the glass of the bulb and around which the glass isfused. As platinum has almost exactly the same coefficient ofheat-expansion as glass, the wires do not cause the glass to crack. The process of manufacture includes the preparation of the filament. This is made from paper, silk, bamboo fibre, tamidine, q. V. , or othermaterial. After shaping into the form of the filament the material iscarbonized at a high heat, while embedded in charcoal, or otherwiseprotected from the air. The flashing process (see Flashing ofincandescent Lamp Carbons) may also be applied. The attachment to theplatinum wires is effected by a minute clamp or by electric soldering. The loop is inserted and secured within the open globe, which the glassblower nearly closes, leaving one opening for exhaustion. The air is pumped out, perhaps first by a piston pump, but always at theend by a mercurial air pump. (See Pump, Geissler--and others. ) As theexhaustion becomes high a current is passed through the carbons heatingthem eventually to white heat so as to expel occluded gas. The occludedgases are exhausted by the pump and the lamp is sealed by melting theglass with a blowpipe or blast-lamp flame. For the exhaustion severallamps are usually fastened together by branching glass tubes, and aresealed off one by one. The incandescent lamps require about 3. 5 watts to the candle power, orgive about 12 sixteen-candle lamps to the horse power expended on them. Generally incandescent lamps are run in parallel or on multiple arccircuits. All that is necessary in such distribution systems is tomaintain a proper potential difference between the two leads acrosswhich the lamps are connected. In the manufacture of lamps they arebrought to an even resistance and the proper voltage at which theyshould be run is often marked upon them. This may be fifty volts andupward. One hundred and ten volts is a very usual figure. As current oneampere for a fifty-volt, or about one-half an ampere for a one hundredand ten volt lamp is employed. Lamp, Incandescent, Three Filament. A three filament lamp is used for three phase currents. It has threefilaments whose inner ends are connected, and each of which has oneleading-in wire. The three wires are connected to the three wires of thecircuit. Each filament receives a current varying in intensity, so thatthere is always one filament passing a current equal to the sum of thecurrents in the other two filaments. Lamp, Lighthouse. A special type of arc light. It is adapted for use in a lighthousedioptric lantern, and hence its arc has to be maintained in the sameposition, in the focus of the lenses. The lamps are so constructed as tofeed both carbons instead of only one, thereby securing the aboveobject. 323 STANDARD ELECTRICAL DICTIONARY. Lamp, Pilot. A lamp connected to a dynamo, and used by its degree of illumination toshow when the dynamo on starting becomes excited, or builds itself up. Lamp, Polyphote. An arc lamp adapted to be used, a number in series, upon the samecircuit. The electric regulating mechanism is placed in shunt or inparallel with the carbons and arc. (See Lamp, Arc. ) Lamps, Bank of. A number of lamps mounted on a board or other base, and connected toserve as voltage indicator or to show the existence of grounds, or forother purposes. Lamp, Semi-incandescent. A lamp partaking of the characteristics of both arc and incandescence; alamp in which the imperfect contact of two carbon electrodes produces apart of or all of the resistance to the current which causesincandescence. The usual type of these lamps includes a thin carbon rod which restsagainst a block of carbon. The species of arc formed at the junction ofthe two heats the carbons. Sometimes the upper carbon or at least itsend is heated also by true incandescence, the current being conveyednear to its end before entering it. Semi-incandescent lamps are not used to any extent now. Lamp Socket. A receptacle for an incandescent lamp; the lamp being inserted thenecessary connections with the two leads are automatically made in mostsockets. The lamps may be screwed or simply thrust into the socket anddifferent ones are constructed for different types of lamps. A key forturning the current on and off is often a part of the socket. Latent Electricity. The bound charge of static electricity. (See Charge, Bound. ) Law of Intermediate Metals. A law of thermo-electricity. The electro-motive force between any twometals is equal to the sum of electro-motive forces between each of thetwo metals and any intermediate metal in the thermo-electric series, orthe electro-motive force between any two metals is equal to the sum ofthe electromotive forces between all the intermediate ones and theoriginal two metals; it is the analogue of Volta's Law, q. V. Law of Inverse Squares. When force is exercised through space from a point, its intensity variesinversely with the square of the distance. Thus the intensity of lightradiated by a luminous point at twice a given distance therefrom is ofone-fourth the intensity it had at the distance in question. Gravitation, electric and magnetic attraction and repulsion and otherradiant forces are subject to the same law. 324 STANDARD ELECTRICAL DICTIONARY. Law of Successive Temperatures. A law of thermo-electricity. The electro-motive force due to a givendifference of temperature between the opposite junctions of the metalsis equal to the sum of the electro-motive forces produced by fractionaldifferences of temperature, whose sum is equal to the given differenceand whose sum exactly fills the given range of temperature. Law, Right-handed Screw. This rather crude name is given by Emtage to a law expressing therelation of direction of current in a circuit to the positive directionof the axis of a magnet acted on by such current. It is thus expressed:A right-handed screw placed along the axis of the magnet and turned inthe direction of the current will move in the positive direction, i. E. , towards the north pole of the axis of the magnet. Lead. A metal; one of the elements; symbol Pb. Atomic weight, 207;equivalent, 103-1/2; valency, 2. Lead may also be a tetrad, when its equivalent is 51. 75. The following data are at 0º C. (32º F. ) with compressed metal:Relative Resistance, (Silver = l) 13. 05Specific Resistance, 19. 63 microhms. Resistance of a wire, (a) 1 ft. Long, weighing 1 grain, 3. 200 ohms. (b) 1 meter long, weighing 1 gram, 2. 232 "(c) 1 meter long, 1 millimeter thick, . 2498 "Resistance of 1 inch cube, 7. 728 microhms. Electro-Chemical Equivalent (Hydrogen = . 0105) 1. 086 mgs. Leading Horns. The tips of pole pieces in a dynamo, which extend in the direction ofmovement of the armature. Leading-in Wires. The platinum wires passing through the glass of an incandescentlamp-chamber, to effect the connection of the carbon filament with thewires of the circuit. Lead of Brushes, Negative. In a motor the brushes are set backwards from their normal position, orin a position towards the direction of armature rotation or given anegative lead instead of a positive one, such as is given to dynamobrushes. Leak. A loss or escape of electricity by accidental connection either with theground or with some conductor. There are various kinds of leak to whichdescriptive terms are applied. Leakage. The loss of current from conductors; due to grounding at least at twoplaces, or to very slight grounding at a great many places, or all alonga line owing to poor insulation. In aerial or pole telegraph lines inwet weather there is often a very large leakage down the wet poles fromthe wire. (See Surface Leakage--Magnetic Leakage. ) 325 STANDARD ELECTRICAL DICTIONARY. Leakage Conductor. A conductor placed on telegraph poles to conduct directly to earth anyleakage from a wire and thus prevent any but a very small portionfinding its way into the other wires on the same pole. It presents achoice of evils, as it increases the electrostatic capacity of the line, and thus does harm as well as good. It consists simply of a wiregrounded and secured to the pole. Leg of Circuit. One lead or side of a complete metallic circuit. Lenz's Law. A law expressing the relations of direction of an inducing current orfield of force to the current induced by any disturbance in therelations between such field and any closed conductor within itsinfluence. It may be variously expressed. (a) If the relative position of two conductors, A and B, be changed, ofwhich A is traversed by a current, a current is induced in B in such adirection that, by its electro-dynamic action on the current in A, itwould have imparted to the conductors a motion of the contrary kind tothat by which the inducing action was produced. (Ganot. ) (b) The new (induced) current will increase the already existingresistances, or develop new resistance to that disturbance of the fieldwhich is the cause of induction. (Daniell. ) (c) When a conductor is moving in a magnetic field a current is inducedin the conductor in such a direction as by its mechanical action tooppose the motion. (Emtage. ) (d) The induced currents are such as to develop resistance to the changebrought about. Letter Boxes, Electric. Letter boxes with electrical connections to a bell or indicator of somesort, which is caused to act by putting a letter into the box. Leyden Jar. A form of static condenser. In its usual form it consists of a glass jar. Tinfoil is pasted aroundthe lower portions of its exterior and interior surfaces, covering fromone-quarter to three-quarters of the walls in ordinary examples. Therest of the glass is preferably shellacked or painted over withinsulating varnish, q. V. The mouth is closed with a wooden or corkstopper and through its centre a brass rod passes which by a short chainor wire is in connection with the interior coating of the jar. The topof the rod carries a brass knob or ball. If such a jar is held by the tinfoil-covered surface in one hand and itsknob is held against the excited prime conductor of a static machine itsinterior becomes charged; an equivalent quantity of the same electricityis repelled through the person of the experimenter to the earth and whenremoved from the conductor it will be found to hold a bound charge. Ifthe outer coating and knob are both touched or nearly touched by aconductor a disruptive discharge through it takes place. 326 STANDARD ELECTRICAL DICTIONARY. Fig. 213. LEYDEN JAR WITH DISCHARGER. If one or more persons act as discharging conductors they will receive ashock. This is done by their joining hands, a person at one end touchingthe outer coating and another person at the other end touching the knob. From an influence machine a charge can be taken by connecting thecoating to one electrode and the knob to the other. Fig. 214. SULPHURIC ACID LEYDEN JAR. 327 STANDARD ELECTRICAL DICTIONARY. Leyden Jar, Sir William Thomson's. An especially efficient form of Leyden jar. It consists of a jar withouter tinfoil coating only. For the interior coating is substituted aquantity of concentrated sulphuric acid. The central rod is of lead witha foot, which is immersed in the acid and from which the rod rises. Awooden cover partly closes the jar, as the central tube through whichthe rod passes is so large as not to allow the wood to touch it. Thusany leakage from inner to outer coating has to pass over the inside andoutside glass surfaces. In the common form of jar the wooden cover mayshort circuit the uncoated portion of the inner glass surface. In thecut a simplified form of Thomson's Leyden jar is shown, adapted forscientific work. Lichtenberg's Figures. If the knob of a Leyden jar or other exited electrode is rubbed over thesurface of ebonite, shellac, resin or other non-conducting surface itleaves it electrified in the path of the knob. If fine powder such asflowers of sulphur or lycopodium is dusted over the surface and theexcess is blown away, the powder will adhere where the surface waselectrified, forming what are called Lichtenberg's Figures, Lycopodiumand sulphur show both positive and negative figures, that is to say, figures produced by a positively or negatively charged conductor. Redlead adheres only to negative figures. If both positive and negativefigures are made and the surface is sprinkled with both red lead andflowers of sulphur each picks out its own figure, the sulphur goingprincipally to the positive one. The red lead takes the form of small circular heaps, the sulphurarranges itself in tufts with numerous diverging branches. Thisindicates the difference in the two electricities. The figures have beendescribed as "a very sensitive electrosope for investigating thedistribution of electricity on an insulating surface. " (Ganot. ) Life of Incandescent Lamps. The period of time a lamp remains in action before the carbon filamentis destroyed. The cause of a lamp failing may be the volatilization ofthe carbon of the filament, causing it to become thin and to break; orthe chamber may leak. The life of the lamp varies; 600 hours is a fairestimate. Sometimes they last several times this period. The higher the intensity at which they are used the shorter is theirlife. From their prime cost and the cost of current the most economicalway to run them can be approximately calculated. [Transcriber's note: Contemporary incandecent buls are rated for 1000hours; flourescent bulbs up to 24000 hours; LED lamps up to 100000 hours. ] Lightning. The electrostatic discharge to the earth or among themselves of cloudsfloating in the atmosphere. The discharge is accompanied by a spark orother luminous effect, which may be very bright and the effects, thermaland mechanical, are often of enormous intensity. The lightning flash is white near the earth, but in the upper regionswhere the air is rarefied it is of a blue tint, like the spark of theelectric machine. The flashes are often over a mile in length, andsometimes are four or five miles long. They have sometimes a curioussinuous and often a branching shape, which has been determined byphotography only recently. To the eye the shape seems zigzag. 328 STANDARD ELECTRICAL DICTIONARY. In the case of a mile-long flash it has been estimated that 3, 516, 480 Dela Rue cells, q. V. , would be required for the development of thepotential, giving the flash over three and one-half millions of volts. But as it is uncertain how far the discharge is helped on its course bythe rain drops this estimate may be too high. There are two general types of flash. The so-called zigzag flashresembles the spark of an electric machine, and is undoubtedly due tothe disruptive discharge from cloud to earth. Sheet lightning has noshape, simply is a sudden glow, and from examination of the spectrumappears to be brush discharges (see Discharge, Brush) between clouds. Heat lightning is attributed to flashes below the horizon whose lightonly is seen by us. Globe or ball lightning takes the form of globes offire, sometimes visible for ten seconds, descending from the clouds. Onreaching the earth they sometimes rebound, and sometimes explode with aloud detonation. No adequate explanation has been found for them. The flash does not exceed one-millionth of a second in duration; itsabsolute light is believed to be comparable to that of the sun, but itsbrief duration makes its total light far less than that of the sun forany period of time. If the disruptive discharge passes through a living animal it is oftenfatal. As it reaches the earth it often has power enough to fuse sand, producing fulgurites, q. V. (See also Back Shock or Stroke ofLightning. ) Volcanic lightning, which accompanies the eruptions of volcanoes, isattributed to friction of the volcanic dust and to vapor condensation. [Transcriber's note: The origin of lightning is still (2008) not fullyunderstood, but is thought to relate to charge separation in thevertical motion of water droplets and ice crystals in cloud updrafts. Alightning bolt carries a current of 40, 000 to 120, 000 amperes, andtransfers a charge of about five coulombs. Nearby air is heated to about10, 000 °C (18, 000 °F), almost twice the temperature of the Sun’ssurface. ] Lightning Arrester. An apparatus for use with electric lines to carry off to earth anylightning discharge such lines may pick up. Such discharge would imperillife as well as property in telegraph offices and the like. Arresters are generally constructed on the following lines. The linewires have connected to them a plate with teeth; a second similar plateis placed near this with its teeth opposite to those of the first plateand nearly touching it. The second plate is connected by a lowresistance conductor to ground. Any lightning discharge is apt to jumpacross the interval, of a small fraction of an inch, between theoppositely placed points and go to earth. Another type consists of two plates, placed face to face, and pressingbetween them a piece of paper or mica. The lightning is supposed toperforate this and go to earth. One plate is connected to the line, theother one is grounded. The lightning arrester is placed near the end of the line before itreaches any instrument. (See Alternative Paths. ) 329 STANDARD ELECTRICAL DICTIONARY. Fig. 215. COMB OR TOOTHED LIGHTNING ARRESTER. Fig. 216. FILM OR PLATE LIGHTNING ARRESTER. Lightning Arrester, Counter-electro-motive Force. An invention of Prof. Elihu Thompson. A lightning arrester in which thelightning discharge sets up a counter-electro-motive force opposed toits own. This it does by an induction coil. If a discharge to earthtakes place it selects the primary of the coil as it has lowself-induction. In its discharge it induces in the secondary a reverseelectro-motive force which protects the line. Lightning Arrester Plates. The toothed plates nearly in contact, tooth for tooth, or the flatplates of a film lightning arrester, which constitute a lightningarrester. Some advocate restricting the term to the plate connected tothe line. Lightning Arrester, Vacuum. A glass tube, almost completely exhausted, into which the line wire isfused, while a wire leading to an earth connection has its end fused inalso. A high tension discharge, such as that of lightning, goes to earthacross the partial vacuum in preference to going through the line, whichby its capacity and self-induction opposes the passage through it of alightning discharge. It is especially adapted for underground and submarine lines. 330 STANDARD ELECTRICAL DICTIONARY. Lightning, Ascending. Lightning is sometimes observed which seems to ascend. It is thoughtthat this may be due to positive electrification of the earth andnegative electrification of the clouds. Lightning, Globe or Globular. A very unusual form of lightning discharge, in which the flashes appearas globes or balls of light. They are sometimes visible for ten seconds, moving so slowly that the eye can follow them. They often rebound onstriking the ground, and sometimes explode with a noise like a cannon. They have never been satisfactorily explained. Sometimes the phenomenonis probably subjective and due to persistence of vision. Lightning Jar. A Leyden jar whose coatings are of metallic filings dusted on to thesurface while shellacked, and before the varnish has had time to dry. Inits discharge a scintillation of sparks appears all over the surface. Line of Contact. The line joining the points of contact of the commutator brushes in adynamo or motor. Synonym--Diameter of Commutation. Lines of Force. Imaginary lines denoting the direction of repulsion or attraction in afield of force, q. V. They may also be so distributed as to indicate therelative intensity of all different parts of the field. They are normalto equipotential surfaces. (See Electro-magnetic Lines ofForce--Electrostatic Lines of Force--Magnetic Lines of Force. ) Lines of Induction. Imaginary lines within a body marking the direction taken within it bymagnetic induction. These are not necessarily parallel to lines offorce, but may, in bodies of uniform agglomeration, or in crystallinebodies, take various directions. Synonym--Lines of Magnetic Induction. Lines of Slope. Lines in a field of force which mark the directions in which theintensity of force in the field most rapidly falls away. Links, Fuse. Links made of more or less easily fusible metal, for use as safetyfuses. Listening Cam. In a telephone exchange a cam or species of switch used to connect theoperator's telephone with a subscriber's line. 331 STANDARD ELECTRICAL DICTIONARY. Lithanode. A block of compressed lead binoxide, with platinum connecting foils foruse as an electrode in a storage battery. It has considerable capacity, over 5 ampere-hours per pound of plates, but has not met with anyextended adoption. Load. In a dynamo the amperes of current delivered by it under any givenconditions. Local Action. (a) In its most usual sense the electric currents within a battery, dueto impurities in the zinc, which currents may circulate in exceedinglyminute circuits, and which waste zinc and chemicals and contributenothing to the regular current of the battery. Amalgamated or chemicallypure zinc develops no local action. (b) The term is sometimes applied to currents set up within the armaturecore or pole pieces of a dynamo. (See Currents, Foucault. ) Local Battery. A battery supplying a local circuit (q. V. ); in telegraphy, where it isprincipally used, the battery is thrown in and out of action by a relay, and its current does the work of actuating the sounder and any otherlocal or station instruments. (See Relay. ) Local Circuit. A short circuit on which are placed local apparatus or instruments. Suchcircuit is of low resistance and its current is supplied by a localbattery, q. V. Its action is determined by the current from the mainline throwing its battery in and out of circuit by a relay, q. V. , orsome equivalent. Local Currents. Currents within the metal parts of a dynamo. (See Currents, Foucault. )In a galvanic battery. Where there is local action, q. V. , there arealso local currents, though they are not often referred to. Localization. Determining the position of anything, such as a break in a cable, or agrounding in a telegraph line. In ocean cables two typical cases are thelocalization of a break in the conductor and of a defect in theinsulation admitting water. The first is done by determining the staticcapacity of the portion of the line which includes the unbroken portionof the conductor; the other by determining the resistance of the line ona grounded circuit. Locus. A place. The word is used to designate the locality or position of, orseries of positions of definite conditions and the like. Thus anisogonic line is the locus of equal declinations of the magnetic needle;it is a line passing through all places on the earth's surface where thecondition of a given declination is found to exist. 332 STANDARD ELECTRICAL DICTIONARY. Lodestone. Magnetic magnetite; magnetite is an ore of iron, Fe3 04 which isattracted by the magnet. Some samples possess polarity and attract iron. The latter are lodestones. Synonym--Hercules Stone Logarithm. The exponent of the power to which it is necessary to raise a fixednumber to produce a given number. The fixed number is the base of thesystem. There are two systems; one, called the ordinary system, has 10for its base, the other, called the Naperian system, has 2. 71828 for itsbase. The latter are also termed hyperbolic logarithms, and are onlyused in special calculations. Log, Electric. An apparatus for measuring the speed of a ship. A rotating helical vaneof known pitch is dragged behind the vessel. As the helix rotates itsmovements may actuate electric machinery for registering its rotations. The number of these in a given time, multiplied by the pitch of thevane, gives the distance traversed in such time. Loop. A portion of a circuit introduced in series into another circuit. Thelatter circuit is opened by a spring-jack, q. V. Or other device, andthe loop inserted. By loops any number of connections can be insertedinto a circuit in series therewith, and in series or in parallel withone another. Loop Break. A double bracket or similar arrangement for holding on insulators theends of a conductor which is cut between them, and to which areconnected the ends of a loop. The space between the insulators may beabout a foot. Luces. This may be used as the plural of lux, q. V. It is the Latin plural. Luminous Jar. A Leyden jar whose coatings are of lozenge-shaped pieces of tinfoilbetween which are very short intervals. When discharged, sparks appearall over the surface where the lozenges nearly join. Lux. A standard of illumination, q. V. , as distinguished from illuminatingpower. It is the light given by one candle at a distance of 12. 7 inches--by acarcel, q. V. , at a distance of one meter---or by 10, 000 candles at105. 8 feet. It was proposed by W. H. Preece. All the above valuations are identical. M. (a) Symbol of gaseous pressure equal to one-millionth of an atmosphere. (b) The Greek m, µ, is used as the symbol of magnetic permeability. 333 STANDARD ELECTRICAL DICTIONARY. Machine, Cylinder Electric. A frictional electric machine whose rotating glass is in the shape of acylinder instead of a disc as in the more recent machines. Fig. 217. PLATE FRICTIONAL ELECTRIC MACHINE. Machine, Frictional Electric. An apparatus for development of high tension electricity by contactaction, brought about by friction. It consists of a plate or cylinder of glass mounted on insulatingstandards and provided with a handle for turning it. One or morecushions of leather are held on an insulated support, so as to rubagainst the plate or cylinder as it is turned. A metal comb or combs areheld on another insulating support so as to be nearly in contact withthe surface of the glass plate at a point as far removed as possiblefrom the rubbers. The combs are attached to a brass ball or round-endedcylinder, which is termed the prime conductor. In use either the prime conductor or cushions are connected by a chainor otherwise with the earth. Assume it to be the cushions. As themachine is worked by turning the plate, the glass and cushion being incontact develop opposite electricities. The glass is charged withpositive electricity, and as it turns carries it off and as it reachesthe prime conductor by induction and conduction robs it of its negativeelectricity. Meanwhile the cushions negatively excited deliver theircharge to the earth. The action thus goes on, the prime conductor beingcharged with positive electricity. 334 STANDARD ELECTRICAL DICTIONARY. If the prime conductor is connected to the earth and the cushions areleft insulated, negative electricity can be collected from the cushions. In some machines both prime conductor and cushions are kept insulatedand without ground contact. Electrodes connecting with each are broughtwith their ends close enough to maintain a sparking discharge. Machine Influence. A static electric machine working by induction to build up charges ofopposite nature on two separate prime conductors. In general they arebased on the principle of the electrophorous. Work is done by theoperator turning the handle. This rotates a disc and draws excited partsof it away from their bound charges. This represents a resistance tomechanical motion. The work absorbed in overcoming this mechanicalresistance appears as electric energy. There are various types ofinfluence machines, the Holtz, Toeppler-Holtz and Wimshurst being themost used. The electrophorous, q. V. , is a type of influence machine. Machine, Holtz Influence. A static electric machine. It includes two plates, one of which israpidly rotated in front of the other. Two armatures of paper aresecured to the back of the stationary plate at opposite ends of adiameter. To start it one of these is charged with electricity. Thischarge by induction acts through the two thicknesses of glass upon ametal bar carrying combs, which lies in front of the further side of themovable plate. The points opposite the armature repel electrified air, which strikes the movable disc and charges it. A second rod with comb atthe opposite end of the same diameter acts in the reverse way. Thusopposite sections of the disc are oppositely charged and the combs withthem. By induction these portions of the disc react upon the twoarmatures. The opposite electricities escape from the armatures by papertongues which are attached thereto and press against the back of themovable plate. As the plate rotates the opposite electricities on itsface neutralize the electricity repelled from the combs. The charges onthe back strengthen the charges of the armatures and brass combs. Thusthe machine builds up, and eventually a discharge of sparks takes placefrom the poles of the brass combs. 335 STANDARD ELECTRICAL DICTIONARY. Machine, Toeppler-Holtz. A modification of the Holtz machine. The priming charge of the armaturesis produced by friction of metallic brushes against metallic buttons onthe face of the rotating plate. (See Machine, Holtz. ) Machine, Wimshurst. A form of static influence machine. It consists of two plates of glass, on which radial sectors of tinfoil are pasted. Both plates are rotatedin opposite directions. The sectors of the two plates react one upon theother, and electric charges of opposite sign accumulate on the oppositesides of the plates and are collected therefrom by collecting combs. Mack. A name, derived from Maxwell, and suggested for the unit of inductance. It is due to Oliver Heaviside, but has never been adopted. (See Henry. ) Magne-Crystallic Action. The action of a supposed force of the same name, proposed by Faraday. Itrelates to the different action of a magnetic field upon crystallinebodies, according to the position of their axes of crystallization. Aneedle of tourmaline, normally paramagnetic, if poised with its axishorizontal, is diamagnetic. Bismuth illustrates the same phenomenon. Thesubject is obscure. Faraday thought that he saw in it the action of aspecific force. Magnet. A body which tends when suspended by its centre of gravity to lay itselfin a definite direction, and to place a definite line within it, itsmagnetic axis, q. V. , in a definite direction, which, roughly speaking, lies north and south. The same bodies have the power of attracting iron(Daniell), also nickel and cobalt. Magnets are substances which possess the power of attracting iron. (Ganot. ) [Transcriber's note: Edward Purcell and others have explained magneticand electromagnetic phenomenon as relativistic effects related toelectrostatic attraction. Magnetism is caused by Lorentz contraction ofspace along the direction of a current. Electromagnetic waves are causedby charge acceleration and the resulting disturbance of theelectrostatic field. (Electricity and Magnetism: Berkeley PhysicsCourse Volume 2, 1960)] Magnet, Anomalous. A magnet possessing more than the normal number (two) of poles. If twostraight magnets are placed end to end with their south poles injuxtaposition the compound bar will seem to possess three poles, one ateach end and one in the middle. The apparent pole in the middle isreally made up of two consequent poles, q. V. It sometimes happens thatwhen a single long thin bar is magnetized consequent poles are produced, although such magnet is in one piece. This may be accidental, as in suchcase it is quite hard to avoid anomalous poles, or, as in the fieldmagnets of some forms of dynamos, anomalous poles may be purposelyproduced. Magnet, Artificial. A magnet formed artificially by any method of magnetization (seeMagnetism) applicable to permanent magnets, electro-magnets andsolenoids. It expresses the distinction from the natural magnets orlodestone, q. V. It is made of steel in practice magnetized by some ofthe methods described under Magnetization. 336 STANDARD ELECTRICAL DICTIONARY. Magnet, Axial. A straight-solenoid with axial core. Magnet, Bar. A bar magnet is one in the shape of a bar, i. C. , straight with parallelsides and considerably longer than wide or deep. Magnet, Bell-shaped. A form of permanent magnet used in some galvanometers. In shape it is athick-sided cylindrical box with two slots cut out of opposite sides, soas to make it represent a horseshoe magnet. Its shape enables it to besurrounded closely by a mass of copper, for damping its motion, torender the instrument dead-beat. Such a magnet is used in Siemens &Halske's galvanometer. Magnet Coil. A coil to be thrust over an iron core, to make an electro-magnet. Theyare often wound upon paper or wooden bobbins or spools, so as to beremovable from the core if desired. Magnet, Compensating. (a) A magnet fastened near a compass on an iron or steel ship tocompensate the action of the metal of the ship upon the magnetic needle. The ship itself always has some polarity and this is neutralized by oneor more compensating magnets. (b) See below. Magnet, Controlling. A magnet attached to a galvanometer by which the directive tendency ofits magnetic needle is adjusted. In the reflecting galvanometer it oftenis a slightly curved magnet carried by a vertical brass spindle risingfrom the center of the instrument, and which magnet may be slid up anddown on the spindle to regulate or adjust its action. Synonym--Compensating Magnet. Magnet, Compound. A permanent magnet, built up of a number of magnets. Small bars can bemore strongly magnetized than large. Hence a compound magnet may be mademore powerful than a simple one. Magnet Core. The iron bar or other mass of iron around which insulated wire is woundfor the production of an electro-magnet. The shapes vary greatly, especially for field magnets of dynamos and motors. For these they areusually made of cast iron, although wrought iron is preferable from thepoint of view of permeability. Magnet, Damping. A damping magnet is one used for bringing an oscillating body to rest. The body may be a metallic disc or needle, and the action of the magnetdepends on its lines of force which it establishes, so that the body hasto cut them, and hence has its motion resisted. 337 STANDARD ELECTRICAL DICTIONARY. Magnet, Deflection of. The change of position of a magnet from the plane of the earth'smeridian in which it normally is at rest into another position at someangle thereto, by the effect of an artificial magnetic field, as thedeflection of a galvanometer needle. Magnet, Electro-. A magnet consisting of a bar of iron, bundle of iron wires, iron tube orsome equivalent, around which a coil of insulated wire is wound. Suchcombination becomes polarized when a current is passed through it and isan active magnet. On the cessation of the current its magnetism in partor almost completely disappears. (See Electro-magnet. ) Magnet, Equator of. In a magnet the locus of points of no attractive power and of nopolarity. In a symmetrical, evenly polarized magnet it is the imaginaryline girdling the centre. The terms Neutral Point or Neutral Line havedisplaced it. Synonyms--Neutral Line--Neutral Point. Magnet, Field. A magnet, generally an electro-magnet, used to produce the field in adynamo or motor. Magnet, Haarlem. Celebrated magnets made in Haarlem, Holland. Logeman, Van Wetteren, Funckler and Van der Willigen were the makers who gave the celebrity tothe magnets. They were generally horseshoe magnets, and would carryabout twenty times their own weight. Magnet, Horseshoe. A magnet of U shape--properly one with the poles brought a little closertogether than the rest of the limbs. For direct lifting and attractiveeffects it is the most generally adopted type. Its advantage as regardslifting effect is due to small reluctance, q. V. , offered by a completeiron circuit, such as the armature and magnet together produce. As theterm is now used it is applied to any U shaped magnet. Fig. 218. JOULE'S ELECTRO-MAGNET. Magnet, Joule's Electro. An electro-magnet of the shape of a cylinder with a longitudinal segmentcut-off. It is wound with wire as shown. The segment cut-off is a pieceof the same shape as the armature. It is of high power. 338 STANDARD ELECTRICAL DICTIONARY. Magnetic Adherence. The tendency of a mass of iron to adhere to the poles of a magnet. It isbest figured as due to the virtual shortening of lines of force, as themore permeable iron gives a better path for them than the air canafford, and consequently a virtually shorter one. Magnetic Attraction and Repulsion. The attraction of a magnet for iron, steel, nickel and cobalt and ofunlike poles of magnets for each other. It is identical withelectro-magnetic attraction, q. V. (Also see Electro-magnetism. ) Magnetic Attraction and Repulsion, Coulomb's Law of. Magnetic attraction and repulsion are inversely as the square of thedistance. (Ganot. ) While theoretically true in the case of isolated poles, in practise itdoes not generally apply on account of the large diameter and relativeshortness of magnets. Magnetic Axis. The line connecting the poles of a magnet. It does not generallycoincide exactly with any symmetrical axis of figure. In such cases anerror is introduced into the indications of the needle which must bedetermined and allowed for in compasses. To determine it with a magneticneedle the suspension cup is made removable, so that the needle can bereversed. Readings are taken with one side of the needle and then withthe other side of the needle up, and the average corresponds with theposition of the magnetic axis in both positions of the needle. Magnetic Azimuth. The angle, measured on a horizontal circle, between the magneticmeridian and a great circle of the earth passing through the observerand any observed body. It is the astronomical azimuth of a body referredto the magnetic meridian and therefore subject to the variation of thecompass. The angle is the magnetic azimuth of the observed body. Magnetic Battery. A name for a compound permanent magnet; one made up by bolting orclamping together, or to single soft iron pole pieces, a number ofsingle permanent magnets. There are a number of forms of compoundmagnets. In making them care has to be taken to have them of evenstrength. It is also well to have them slightly separated. The object ofboth these precautions is to prevent a stronger element or magnet fromdepolarizing its neighbor. Synonym--Compound Magnet. Magnetic Bridge. An apparatus for testing the relative permeability of iron. It consistsof a rectangular system of iron cores. Three of the sides are wound withwire as shown. The other side is built up of double bars, and from thecentre two curved arms rise, as shown in the cut. The arms do not touch. Between them a short magnet is suspended by a filament, which alsocarries a mirror and an index. 339 STANDARD ELECTRICAL DICTIONARY. Fig. 219. MAGNETIC BRIDGE. A lamp and scale are provided as in the reflecting galvanometer. Whenadjusted the magnetic needle hangs as shown in the cut, Fig. 219, without any tendency to turn towards either curved pole piece. If alliron parts are symmetrical and of similar metal, a current through thecoils will make no difference. It will work in magnetic opposition uponthe two arms, or, in other words, will maintain both arms at identicalpotential. Fig. 220. POLE PIECES, MAGNETIC NEEDLE AND MIRROR OF MAGNETIC BRIDGE. If there is the least difference in permeability, length or thicknessbetween any of the iron bars the magnetic potential of the two curvedarms will differ, and the magnetic needle will turn one way or theother. In practical use different samples of iron are substituted forthe unwound members of the fourth side of the parallelogram, and theneedle by its motions indicates the permeability. In the cut, Fig. 220, D D are the ends of the curved pole pieces; A thewire carrying the mirror B and magnetic needle N, and E is the indexwhich shows the larger deflections. 340 STANDARD ELECTRICAL DICTIONARY. Magnetic Circuit. A magnetic field of force is characterized by the presence of lines offorce, which, while approximately parallel, curve around and tend toform closed curves. The polarity of a field of force is referred to animaginary direction of the lines of force from the north pole throughspace to the south pole, and in the part of the field corresponding tothe body of the magnet, from the south to the north pole. The cutindicates these features. Hence the magnetic field of force is termedthe magnetic circuit, and to it are attributed a species of resistancetermed reluctance, q. V. , and the producing cause of the field or linesof force is termed sometimes magneto-motive force, q. V. ) correspondingto the electro-motive force. The modern treatment of the magneticcircuit is similar to the application of Ohm's law and the laws ofresistance and conductivity to the electric circuit. Magnetic Circuit, Double. A magnetic circuit which virtually represents two horseshoe magnetsplaced with their like poles in contact. It is used for field magnets, the armatures occupying a place between the consequent poles. Fig. 221. ONE-HALF PORTION OF A DOUBLE MAGNETIC CIRCUIT. Magnetic Concentration of Ores. The concentration of ores or the freeing them from their gangue bymagnetic attraction. It is only applicable to those cases in whicheither the ore itself or the gangue is attracted by the magnet. Itsprincipal application is to the concentration of magnetic iron sands. (See Magnetic Concentration. ) Magnetic Concentrator. An apparatus similar to a magnetic separator, q. V. , but used toconcentrate magnetic iron sands. By the action of electro-magnets themagnetic iron sand (magnetite) is separated from the sand with which itis mixed. Magnetic Conductivity and Conductance. The first notion of permeance and of the magnetic circuit included theidea of magnetic conductivity, which conducted lines of force urged bymagneto-motive force through a magnetic circuit. The terms are displacedby permeability and permeance. 341 STANDARD ELECTRICAL DICTIONARY. Magnetic Continuity. The completeness of a magnetic circuit, as when the armature of ahorseshoe magnet is in contact with both poles. It is an attribute of aparamagnetic substance only and is identical for permanent magnets orfor electro-magnets. An air space intervening between armature andmagnet poles, or a space filled with any diamagnetic substance preventscontinuity, although the lines of force to some extent still find theirway around. The leakage is increased by discontinuity. Magnetic Control. Control of a magnetic needle, magnet, iron index or armature, in agalvanometer, ammeter or voltmeter by a magnetic field; the restitutiveforce being derived from a permanent magnet. Magnetic Couple. The couple of magnetic force which tends to bring the magnetic needleinto the plane of the magnetic meridian. One force is represented by theimaginary pull upon the north pole, and the other by the opposite pullupon the south pole of the needle. The moment of the couple varies froma maximum when the needle is at right angles to the plane of themagnetic meridian to zero when it is in such plane. Magnetic Creeping. Viscous hysteresis; the slow increase of magnetism in a paramagneticbody when exposed to induction. Fig. 222. MAGNETIC CURVES OR FIGURES. Magnetic Curves. The pictorial representation of magnetic lines of force. It is generallyproduced by scattering filings on a sheet of paper or pane of glass heldover a magnet. The filings arrange themselves in characteristic curves. Tapping the paper or pane of glass facilitates the arrangement, orjarring the filings off a smaller magnet, so that they fall polarizedupon the paper, is thought by some to improve the effect. The group ofcurves forms what are termed magnetic figures, q. V. 342 STANDARD ELECTRICAL DICTIONARY. Magnetic Declination. The angular deviation of the magnetic needle, causing it to rest at anangle with the true meridian; the variation of the compass. (SeeMagnetic Elements. ) Magnetic Density. The intensity of magnetization expressed in lines of force per statedarea of cross-section in a plane at right angles to the lines of force. Magnetic Dip. The inclination from the horizontal assumed by a magnetic needle free tomove in the vertical plane. (See Magnetic Elements. ) The angle of dip orinclination is entirely a function of the earth, not of the needle. Magnetic Discontinuity. A break or gap in a magnetic circuit. To make a complete circuit theiron or other core must be continuous. If the armature of a horseshoemagnet is in contact with both poles the continuity is complete. If thearmature is not in contact magnetic continuity gives place todiscontinuity. It is an attribute of a paramagnetic substance only, andis identical for permanent magnets, or for electro-magnets. Magnetic Elements. The qualities of the terrestrial magnetism at any place as expressed inits action upon the magnetic needle. Three data are involved. I. The Declination or Variation. II. The Inclination or Dip. III. The Force or Intensity. I. The Declination is the variation expressed in angular degrees of themagnetic needle from the true north and south, or is the angle which theplane of the magnetic meridian makes with that of the geographicalmeridian. It is expressed as east or west variation according to theposition of the north pole; east when the north pole of the needle is tothe east of the true meridian, and vice versa. Declination is differentfor different places; it is at present west in Europe and Africa, andeast in Asia and the greater part of North and South America. Thedeclination is subject to (a) secular, (b) annual and (c) diurnalvariations. These are classed as regular; others due to magnetic stormsare transitory and are classed as irregular, (a) Secular variations. Thefollowing table shows the secular variations during some three hundredyears at Paris. These changes are termed secular, because they requirecenturies for their completion. 343 STANDARD ELECTRICAL DICTIONARY. Table of Declination or Variation at Paris. Year. Declination. 1580 11º 30' E. 1663 0°1700 8° 10' W. 1780 19º 55' W. 1785 22º 00' W. 1805 22º 5' W. 1814 22º 34' W. 1825 22° 22' W. 1830 22º 12' W. 1835 22º 4' W. 1850 20º 30' W. 1855 19º 57' W. 1860 19º 32' W. 1865 18º 44' W. 1875 17º 21' W. 1878 17º 00' W. [Transcriber's note The value for 2008 is about 0° 48' W, changing by0° 7' E/year. ] On scrutinizing these figures it will be seen that there is part of acycle represented and that the declination is slowly returning to thezero point after having reached its maximum western variation in 1814. Upwards of 300 years would be required for its completion on the basisof what is known. In other places, notably the coast of Newfoundland, the Gulf of the St. Lawrence and the rest of the North American seaboardand in the British Channel, the secular variations are much more rapidin progress. (b) Annual variations--These were first discovered in 1780by Cassini. They represent a cycle of annual change of small extent, from 15' to 18' only. In Paris and London the annual variation isgreatest about the vernal equinox, or March 21st, and diminishes for thenext three months, and slowly increases again during the nine followingmonths. It varies during different epochs. (c) Diurnal variations werediscovered in 1722 by Graham. A long needle has to be employed, or thereflection of a ray of light, as in the reflecting galvanometer, has tobe used to observe them. In England the north pole of the magneticneedle moves every day from east to west from sunrise until 1 or 2 P. M. ; it then tends towards the east and recovers its original position by10 P. M. During the night the needle is almost stationary. As regardsrange the mean amplitude of diurnal variations at Paris is from April toSeptember 13' to 15'; for the other months from 8' to 10'. On some daysit amounts to 25' and sometimes is no more than 5'. The amplitude ofdiurnal variations decreases from the poles to the equator. Irregularvariations accompany earthquakes, the aurora borealis and volcaniceruptions. In Polar regions the auroral variations may be very great;even at 40° latitude they may be 1° or 2°. Simultaneous irregularitiessometimes extend over large areas. Such are attributed to magneticstorms. II. The Inclination is the angle which the magnetic needle makeswith the horizon, when the vertical plane in which the needle is assumedto be free to move coincides with the magnetic meridian. It is sometimescalled the dip of the needle. It varies as does the declination, asshown in the following table of inclinations of London. 344 STANDARD ELECTRICAL DICTIONARY. Table of Inclination or Dip at LondonYear. Inclination. 1576 71° 50'1600 72°1676 73° 30'1723 74° 42'1773 72° 19'1780 72° 8'1790 71° 33'1800 70° 35'1821 70° 31'1828 69° 47'1838 69° 17'1854 68° 31'1859 68° 21'1874 67° 43'1876 67° 39'1878 67° 36'1880 67° 35'1881 67° 35' III. Force or Intensity is the directive force of the earth. It varieswith the squares of the number of oscillations the magnetic needle willmake if caused to oscillate from a determined initial range. Theintensity is supposed to be subject to secular change. According toGauss the total magnetic intensity of the earth is equal to that whichwould be exerted if in each cubic yard there were eight bar magnets, each weighing one pound. This is, of course, a rough way of expressingthe degree of intensity. Intensity is least near the magnetic equatorand greatest near the magnetic poles; the places of maximum intensityare termed the magnetic foci. It varies with the time of day andpossibly with changes in altitude. Magnetic Elongation. The elongation a bar of iron or steel undergoes when magnetized. Bymagnetization it becomes a little longer and thinner, there being noperceptible change in volume. The change is accompanied by a slightsound--the magnetic tick. An exceedingly delicate adjustment ofapparatus is required for its observation. Magnetic Equator. A locus of the earth's surface where the magnet has no tendency to dip. It is, approximately speaking, a line equally distant from the magneticpoles, and is called also the aclinic line. It is not a great circle ofthe earth. 345 STANDARD ELECTRICAL DICTIONARY. Magnetic Field of Force. The field of force established by a magnet pole. The attractions andrepulsions exercised by such a field follow the course of the electro-magnetic lines of force. (See also Field of Force. ) Thus the tendency ofa polarized needle attracted or repelled is to follow, always keepingtangential to curved lines, the direction of the lines of force, howeversweeping they may be. The direction of magnetic lines of force isassumed to be the direction in which a positive pole is repelled or anegative one attracted; in other words, from the north pole of a magnetto its south pole in the outer circuit. The direction of lines of forceat any point, and the intensity or strength of the field at that point, express the conditions there. The intensity may bc expressed in terms ofthat which a unit pole at unit distance would produce. This intensity asunitary it has been proposed to term a Gauss. (See Weber. ) The direction of the lines of force in a magnetic field are shown by thetime-honored experiment of sprinkling filings of iron upon a sheet ofpaper held over a magnet pole or poles. They arrange themselves, if thepaper is tapped, in more or less curved lines tending to reach from onepole of the magnet to the other. Many figures may be produced bydifferent conditions. Two near poles of like name produce lines of forcewhich repel each other. (See Magnetic Curves. ) A magnetic and an electro-magnetic field are identical in all essentialrespects; the magnetic field may be regarded as a special form of theelectro-magnetic field, but only special as regards its production andits defined north and south polar regions. Synonyms--Magnetic Spin (not much used). Magnetic Field, Uniform. A field of identical strength in all parts, such as the earth's magneticfield. If artificially produced, which can only be approximately done, it implies large cross-section of magnet pole in proportion to thelength of the magnetic needle affected by it, which is used indetermining its uniformity. Magnetic Figures. The figures produced by iron filings upon paper or glass held nearmagnetic poles. By these figures the direction of lines of force isapproximately given, and a species of map of the field is shown. (SeeMagnetic Field of Force--Magnetic Curves. ) Magnetic Filament. The successive rows of polarized molecules assumed to exist inmagnetized iron. Each molecule represents an infinitely small magnet, and its north pole points to the south pole of the next molecule. Such astring or row is a theoretical conception based on the idea that themolecules in a magnet are all swung in to parallelism in the magnetizingprocess. A magnetic filament may be termed the longitudinal element of amagnet. (See Magnetism, Hughes' Theory of. ) [Transcriber's note: This description parallels the modernnotion of electron spin as the basis of magnetism in materials. ] Magnetic Fluids. A two-fluid theory of magnetism has been evolved, analogous to thetwo-fluid theory of electricity. It assumes north fluid or "redmagnetism" and a south fluid or "blue magnetism. " Each magnetism issupposed to predominate at its own pole and to attract its opposite. Before magnetization the fluids are supposed to neutralize each otherabout each molecule; magnetization is assumed to separate them, accumulating quantities of them at the poles. Magnetic Flux. Magnetic induction; the number of lines of force that pass through amagnetic circuit. Synonym--Magnetic Flow. 346 STANDARD ELECTRICAL DICTIONARY. Magnetic Force. The forces of attraction and repulsion exercised by a magnet. ByAmpere's theory it is identical with the forces of attraction andrepulsion of electric currents. Magnetic Friction. The damping effect produced on the movements of a mass of metal byproximity to a magnet; the phenomenon illustrated in Arago's wheel, q. V. When a mass of metal moves in the vicinity of a magnet it cuts thelines of force emanating from its poles, thereby producing currents inits mass; as the production of these currents absorbs energy a dampingeffect is produced upon the movements of the mass. Magnetic Gear. Friction gear in which electro-magnetic adherence is employed to drawthe wheels together. (See Adherence, Electro-magnetic--Electro-magneticFriction Gear. ) Magnetic Inclination. The inclination from the horizontal of a magnetic needle placed in themagnetic meridian. (See Magnetic Element--Inclination Map. ) Synonym--Magnetic Dip. Magnetic Induction. The force of magnetization within an induced magnet. It is in part dueto the action of the surrounding particles of polarized material; inpart to the magnetic field. (See Magnetic Induction, Coefficient of. ) In a more general way it is the action of a magnet upon bodies in itsfield of force. In some cases the magnetism induced causes the northpole of the induced magnet to place itself as far as possible from thenorth pole of the inducing magnet and the same for the south poles. Suchsubstances are called paramagnetic or ferromagnetic. They lie parallelor tangential to the lines of force. In other cases the bodies lie atright angles or normal to the lines of force. Such bodies are calleddiamagnetic. Some bodies are crystalline or not homogeneous in structure, and in themthe lines of magnetic induction may take irregular or eccentric paths. (See AEolotropic. ) Synonym--Magnetic Influence. Magnetic Induction, Apparent Coefficient of. The apparent permeability of a paramagnetic body as affected by thepresence of Foucault currents in the material itself. These currents actexactly as do the currents in the coils surrounding the cores ofelectro-magnets. They produce lines of force which may exhaust thepermeability of the iron, or may, if in an opposite direction, add toits apparent permeability. Magnetic Induction, Coefficient of. The number, obtained by dividing the magnetization of a body, expressedin lines of force produced in it, by the magnetizing force which hasproduced such magnetization, expressed in lines of force producible bythe force in question in air. It always exceeds unity for iron, nickeland cobalt. It is also obtained by multiplying the coefficient ofinduced magnetization by 4 PI (4 * 3. 14159) and adding 1. (See MagneticSusceptibility--Magnetization, Coefficient of Induced. ) 347 STANDARD ELECTRICAL DICTIONARY. The coefficient of magnetic induction varies with the material of theinduced mass, and varies with the intensity of the magnetizing force. This variation is due to the fact that as the induced magnetism in abody increases, the magnetizing force required to maintain suchinduction, increases in a more rapid ratio. The coefficient of magneticinduction is the same as magnetic permeability, and in a certain senseis the analogue of conductivity. It is also termed the multiplying powerof the body or core magnetized. It is the coefficient of inducedmagnetization (see Magnetization, Coefficient of Induced) referred to amass of matter. For diamagnetic bodies the coefficient has a negativesign; for paramagnetic bodies it has a positive sign. Synonyms--Permeability--Multiplying Power--Magnetic Inductive Capacity. Magnetic Induction, Dynamic. The induction produced by a magnetic field which moves with respect to abody, or where the body if moving moves at a different rate, or wherethe body moves and the field is stationary. In the case where both move, part of the induction may be dynamic and part static. (See MagneticInduction, Static. ) Magnetic Induction, Static. Magnetic induction produced by a stationary field acting upon astationary body. Magnetic Induction, Tube of. An approximate cylinder or frustrum of a cone whose sides are formed oflines of magnetic induction. (See Magnetic Induction, Lines of. ) Theterm tube is very curiously applied in this case, because the element orportion of a magnetic field thus designated is in no sense hollow ortubular. Magnetic Inertia. A sensible time is required to magnetize iron, or for it to part withits magnetism, however soft it may be. This is due to its magneticinertia and is termed the lag. Permanent or residual magnetism is aphase of it. It is analogous to self-induction of an electric circuit, or to the residual capacity of a dielectric. Magnetic Insulation. Only approximate insulation of magnetism is possible. There is noperfect insulator. The best ones are only 10, 000 times less permeablethan iron. Hence lines of force find their way through air and all othersubstance, being simply crowded together more in paths of iron or otherparamagnetic substance. 348 STANDARD ELECTRICAL DICTIONARY. Magnetic Intensity. The intensity of the magnetization of a body. It is measured by themagnetic lines of force passing through a unit area of the body, sucharea being at right angles to the direction of the lines of force. Magnetic Lag. In magnetism the tendency of hard iron or steel especially to take upmagnetism slowly, and to part with it slowly. (See Magnetic Inertia. )The lag affects the action of a dynamo, and is a minor cause of thosenecessitating the lead of the brushes. Synonym--Magnetic Retardation. Magnetic Latitude. Latitude referred to the magnetic equator and isoclinic lines. Magnetic Leakage. The lines of force in a field magnet which pass through the air and notthrough the armature are useless and represent a waste of field. Suchlines constitute magnetic leakage. Magnetic Limit. The temperature beyond which a paramagnetic metal cannot be magnetized. The magnetic limit of iron is from a red to a white heat; of cobalt, farbeyond a white heat; of chromium, below a red heat; of nickel at about350° C. (662°F. ) of manganese, from 15° C. To 20° C. (59° to 68° F. ) Magnetic Lines of Force. Lines of force indicating the distribution of magnetic force, which isdue presumably to whirls of the ether. A wire or conductor through whicha current is passing is surrounded by an electro-magnetic field offorce, q. V. , whose lines of force form circles surrounding theconductor in question. A magnet marks the existence of a similarelectro-magnetic field of force whose lines form circuits comprisingpart of and in some places all of the body of the magnet, and which arecompleted through the air or any surrounding paramagnetic or diamagneticbody. They may be thought of as formed by the Ampérian sheet of current, and analogous to those just mentioned as surrounding a conductor. Fig. 223. MAGNETIC LINES OF FORCE, DIRECTION OF. A magnetic line of force may be thought of as a set of vortices orwhirls, parallel to each other, and strung along the line of force whichis the locus of their centres. If as many lines are drawn per square centimeter as there are dynes (perunit pole) of force at the point in question, each such line will be aunitary c. G. S. Line of force. 349 STANDARD ELECTRICAL DICTIONARY. Magnetic Mass. A term for a quantity of magnetism. Unit mass is the quantity which atunit distance exercises unit force. Magnetic Matter. Imaginary matter assumed as a cause of magnetism. Two kinds, onepositive and one negative, may be assumed as in the two fluid theory ofelectricity, or only one kind, as in the single fluid theory ofelectricity. Various theories of magnetic matter have been presentedwhose value is only in their convenience. [Transcriber's note: See "magnet" and Edward Purcell's explanation ofmagnetism using general relativity. ] Magnetic Memory. The property of retaining magnetism; coercive force; magnetic inertia;residual magnetism. [Transcriber's note: Small ferrite magnetic donuts were used as computermain memory from 1950 to 1970. ] Magnetic Meridian. A line formed on the earth's surface by the intersection therewith of aplane passing through the magnetic axis. It is a line determined by thedirection of the compass needle. The meridians constantly change indirection and correspond in a general way to the geographical meridians. Magnetic Moment. The statical couple with which a magnet would be acted on by a uniformmagnetic field of unit intensity if placed with its magnetic axis atright angles to the lines of force of the field. (Emtage. ) A uniformlyand longitudinally magnetized bar has a magnetic moment equal to theproduct of its length by the strength of its positive pole. Magnetic Needle. A magnet with a cup or small depression at its centre and poised upon asharp pin so as to be free to rotate or oscillate in a horizontal plane. The cup is often made of agate. Left free to take any position, itplaces its magnetic axis in the magnetic meridian. Magnetic Parallels. Lines roughly parallel to the magnetic equator on all parts of each ofwhich the dip of the magnetic needle is the same; also called IsoclinicLines. These lines mark the places of the intersection of equipotentialsurfaces with the earth's surface. They are not true circles, and nearthe poles are irregular ellipses; the magnet there points toward theircentres of curvature. They correspond in a general way with theGeographical Parallels of Latitude. Magnetic Permeability. The specific susceptibility of any substance, existing in a mass, formagnetic induction. (See Magnetic Induction, Coefficient of, synonym forMagnetic Permeability and Magnetization, Coefficient of Induced. ) Synonyms--Magnetic Inductive Capacity--Multiplying Power--Coefficient ofMagnetic Induction. 350 STANDARD ELECTRICAL DICTIONARY. Magnetic Perturbations. Irregular disturbances of the terrestrial magnetism, as by the auroraand in electric storms. Magnetic Poles. The points where the equipotential surfaces of the terrestrial field offorce graze the earth's surface; the points toward which the north orsouth poles of the magnetic needle is attracted. Over a magnetic polethe magnetic needle tends to stand in a vertical position. There are twopoles, Arctic or negative, and Antarctic or positive. Magnetic needlessurrounding them do not necessarily point toward them, as they point tothe centres of curvature of their respective magnetic parallels. Thepoles constantly change in position. The line joining them does notcoincide with anything which may be termed the magnetic axis of theearth. Magnetic Poles, False. Poles on the earth's surface other than the two regular magnetic poles. There seem by observation to be several such poles, while analogy wouldlimit true magnetic poles to two in number. Magnetic Potential. The potential at any point of a magnetic field is the work which wouldbe done by the magnetic forces of the field upon a positive unit ofmagnetism as it moves from that point to an infinite distance. (Emtage. ) Magnetic Proof Piece. A piece of iron used for testing magnets and the distribution ofmagnetism in bars, by suspending or supporting above or near the magnet, by detaching after adherence, and in other ways. Magnetic Proof Plane. An exploring coil used for testing the distribution of magnetism. It isconnected in circuit with a galvanometer, and exposed to alternation ofcurrent, or to other disturbing action produced by the magnet or fieldunder examination. This affects the galvanometer, and from its movementsthe current produced in the coil, and thence the magnetic induction towhich it was exposed, are calculated. Synonym--Exploring Coil. Magnetic Quantity. The magnetism possessed by a body; it is proportional to the action ofsimilar poles upon each other, or to the field produced by the pole inquestion. It is also called the strength of a pole. The force exercised by two similar poles upon each other varies withtheir product and inversely with the square of the distance separatingthem; or it may be expressed thus (m * m) / (L^2). This is a force, andthe dimensions of a force are ML/(T^2). Therefore, (m^2)/(L^2) =ML/(T^2) or m = (M^. 5)*(L^1. 5)/T. 351 STANDARD ELECTRICAL DICTIONARY. Magnetic Reluctance. The reciprocal of permeance; magnetic resistance; the relativeresistance to the passage of lines of force offered by differentsubstances. The idea is derived from treating the magnetic circuit likean electric one, and basing its action on magneto-motive force actingthrough a circuit possessing magnetic reluctance. Magnetic Reluctivity. The reciprocal of magnetic permeability, q. V. Synonym--Magnetic Resistance. Magnetic Retentivity. The property of steel or hard iron by which it slowly takes up andslowly parts with a magnetic condition--traditionally (Daniell) calledcoercitive force. Magnetic Rotary Polarization. If a plane polarized beam of light is sent through a transparent mediumin a magnetic field its plane of polarization is rotated, and thisphenomenon is denoted as above. (Compare Refraction, Electric, and seeElectro-magnetic Stress. ) This has been made the basis of a method formeasuring current. A field of force varies with the current; thepolarization produced by such field is therefore proportional to thecurrent. (Becquerel & Rayleigh. ) A plane polarized beam of light passing through the transparent mediumin the magnetic field by the retardation or acceleration of one of itscircular components has its plane of polarization rotated as described. The direction of the lines of force and the nature of the mediumdetermine the sense of the rotation; the amount depends upon theintensity of the field resolved in the direction of the ray, and on thethickness and nature of the medium. Magnetic Saturation. The maximum magnetic force which can be permanently imparted to a steelbar. A bar may be magnetized beyond this point, but soon sinks to it. The magnetism produced in a bar is prevented from depolarization by theretentivity or coercive force of the bar. The higher the degree ofmagnetization the greater the tendency to depolarization. It is also defined as the maximum intensity of magnetism produced in aparamagnetic substance by a magnetic field as far as affected by thepermeability of the substance in question. The more lines of forcepassed through such a substance the lower is its residual permeability. It is assumed that this becomes zero after a certain point, and then thepoint of saturation is reached. After this point is reached the additionof any lines of force is referred entirely to the field and not at allto the permeability of the substance. But such a zero is only definableapproximately. Magnetic Screen. A box or case of soft iron, as thick as practicable, for protectingbodies within it from the action of a magnetic field. The lines of forceto a great extent keep within the metal of the box on account of itspermeability, and but a comparatively few of them cross the space withinit. Such screens are used to prevent watches from being magnetized, and area part of Sir William Thomson's Marine galvanometer. A magnetic screen may be a sphere, an infinite or very large plane, orof the shape of any equipotential surface. Synonym--Magnetic Shield. 352 STANDARD ELECTRICAL DICTIONARY. Magnetic Self-induction. The cause of a magnet weakening is on account of this quality, which isdue to the direction of the lines of force within a magnet from thepositive towards the negative pole. "A magnet thus tends to repel itsown magnetism and to weaken itself by self-induction. " (Daniell. ) Magnetic Separator. An apparatus for separating magnetic substances from mixtures. Suchseparators depend on the action of electro-magnets. In one form thematerial falls upon an iron drum, magnetized by coils. Any magneticsubstance adheres to the drum and is thereby separated. They are used byporcelain makers for withdrawing iron particles from clay, by machiniststo separate iron filings and chips from brass, and for similar purposes. Fig. 224. MAGNETIC SEPARATOR. Magnetic Shell. A theoretical conception of a cause of a magnetic field or of adistribution of magnetism. If we imagine a quantity of very shortmagnets arranged in contact with their like poles all pointing in thesame direction so as to make a metal sheet, we have a magnetic shell. Its magnetic moment is equal to the sum of the magnetic moment of allits parts. If the shell is of uniform strength the magnetic moment of aunit area gives the strength of the shell; it is equal to the magneticquantity per unit of area, multiplied by the thickness of the shell. If its strength is uniform throughout a magnetic shell is called simple;if its strength varies it is termed complex. Emtage thus defines it: A magnetic shell is an indefinitely thin sheetmagnetized everywhere in the direction normal to itself. Magnetic Shell, Strength of. The magnetic quantity per unit of area of the shell multiplied by thethickness of the shell. 353 STANDARD ELECTRICAL DICTIONARY. Magnetic Shield. In general a magnetic screen, q. V. Sometimes a strong local field ismade to act as a shield, by its predominance overcoming any local orterrestrial field to which the needle to be protected may be exposed. Magnetic Shunt. The conception of a magnetic circuit being formed, the shunt is acorollary of the theory. It is any piece of iron which connects pointsof a magnet differing in polarity, so as to divert part of the lines offorce from the armature or yoke. The shunt is especially applicable inthe case of horseshoe magnets. Thus a bar of iron placed across fromlimb to limb a short distance back from the poles would act as a shuntto the armature and would divert to itself part of the lines of forcewhich would otherwise go through the armature and would weaken theattraction of the magnet for the latter. In dynamos a bar of iron usedas a magnetic shunt has been used to diminish the lines of force goingthrough the armature and hence to weaken the field and diminish theelectro-motive force. By moving the shunt nearer or further from thepoles the dynamo is regulated. In the cut the projections between the yoke and poles of the magnetshown act as a shunt to the yoke, taking some lines of force therefrom. Fig. 225. MAGNETIC SHUNT. Magnetic Storms. Terrestrial magnetic disturbances sometimes covering very wide areas, and affecting the magnetic declination and inclination. One suchdisturbance was felt simultaneously at Toronto, Canada, the Cape of GoodHope, Prague and Van Diemen's Land. (Sabine. ) 354 STANDARD ELECTRICAL DICTIONARY. Magnetic Strain. The strain produced by magnetic lines of force in substances exposed totheir action. It is observed in substances placed between the poles of astrong electro-magnet, and evinces itself in the alteration of theoptical properties of transparent substances. Magnetic Stress. The stress produced by magnetic lines of force on substances throughwhich they pass, evidenced in alteration of the optical properties oftransparent bodies thus treated. Magnetic Susceptibility. The specific intrinsic susceptibility of any material for magneticinduction. It refers to the particle of matter, and not to the mass, asin the latter its own particles react on each other and bring about whatis termed permeability, q. V. (See also Magnetization, Coefficient ofInduced, and Magnetic Induction, Coefficient of. ) Synonym--Coefficient of Induced Magnetization. Magnetic Tick. When a bar of iron is suddenly magnetized or demagnetized it emits aslight sound, called the Page sound, or the magnetic tick. This has beenutilized in a telephone by Reiss. The telephone will receive sound, butis very weak. It consists of a bar surrounded with a coil of insulatedwire. Variations in current produce sounds, which may be articulate ifthe currents are produced by a telephonic transmitter. Magnetic Twist. A bar of iron held in the magnetic meridian and pointing to the pole andtwisted becomes to some extent permanently magnetized. Conversely a barwhen magnetized seems to have a twist set up in it. The latter ismagnetic twist. Magnetic Variations. Changes in the value of magnetic declination or inclination. (SeeMagnetic Elements. ) Magnetism, Ampére's Theory of. A theory accounting for magnetic phenomena by assuming the existence ofcurrents circulating around the molecules of permanent magnets. If suchcurrents so circulate and all in the same direction, the result is thesame as if the body of the magnet was enveloped in currents representingthose of an electro-magnet or solenoid. This is because in the interiorthe current around one molecule would counteract the current around itsneighboring ones in part, so that the only virtual currents left wouldbe represented by those on the outer surfaces of the outer shell ofmolecules, and these virtually resolve themselves into one generalcurrent sheet, surrounding the magnet and coinciding with its surface. The theory assumes that such currents permanently circulate around themolecules of paramagnetic substances. Under ordinary conditions there isno coincidence in their direction and no resultant current is produced. When magnetized or polarized the molecules are brought into order, sothat the direction of their current coincides and the body becomes amagnet. 355 STANDARD ELECTRICAL DICTIONARY. Fig. 226. AMPÉRIAN CURRENTS IN MAGNETS. At the north pole of the magnet the direction of the Ampérian currentsis the reverse of that of a watch when the observer faces the pole; thereverse obtains for the south pole. The attraction of opposite and repulsion of similar poles is explainedby the actions of the Ampérian currents upon each other. If north andsouth pole are placed together these currents will coincide in directionand hence will attract each other. If two like poles are put togetherthe currents will have opposite directions and will repel each other. No energy is supposed to be required to maintain currents around or in asingle molecule. Fig. 227. NORTH AND SOUTH POLES OF A MAGNET SHOWING DIRECTION OFAMPÉRIAN CURRENTS. Magnetism, Blue. A term arising from the two fluid theory of magnetism; the magnetism ofthe south pole of a magnet. (See Magnetic Fluids. ) The magnetism of thenorth pole is termed red magnetism. Both terms originated presumably inthe painting of magnets, and are little used. Synonym--South Magnetic Fluid. 356 STANDARD ELECTRICAL DICTIONARY. Magnetism, Components of Earth's. The magnetic force of the earth acts in the plane of the magneticmeridian and in direction generally lies oblique to the plane of thehorizon. It can be resolved into two components, one vertical, which hasno directive effect upon the magnetic needle, the other horizontal, which represents the directive element for the usual compass needle. Forthe dipping needle, q. V. , the vertical component is the only activeone. A magnetic needle mounted on a universal joint at its centre ofgravity would be acted on by both components. Magnetism, Creeping of. The gradual increase of magnetism when a magnetic force is applied withabsolute steadiness to a piece of iron. It is a form of magnetic lag. Itmay last for half an hour and involve an increase of several per cent. Of the total magnetism. Synonym--Viscous Hysteresis. Magnet, Iron Clad. A magnet with a casing of iron connected at one end to the core. Theterm is generally applied to electromagnets of this form. Synonyms--Tubular Magnet--Jacketed Magnet. Magnetism, Decay of. The gradual loss of magnetism by permanent magnets, due to accidentalshocks, changes of temperature, slow spontaneous annealing of the ironand other similar causes. Magnetism, Discharge of. The loosing of magnetization. Thus in a shunt-wound dynamo there is acritical resistance for the outer circuit, below which the field ceasesto be magnetized, as enough current ceases to be shunted into it tomagnetize it. The machine is said to unbuild itself, and a discharge ofmagnetism occurs from the field magnet. Magnetism, Ewing's Theory of. Ewing found by a model consisting of a number of pivoted magneticneedles that the observed phenomena of magnetization could berepresented thereby. Thus there would be no need of assuming internalfrictional forces of Maxwell, nor the closed rings or chains of Hughes. The theory retains the notion, however, of paramagnetic matter, consisting of an assemblage of molecular magnets. The loss of energy byhysteresis is represented in the model by the energy lost by the needlesin beating against the air. 357 STANDARD ELECTRICAL DICTIONARY. Magnetism, Free. The magnetism or magnetic field outside of a magnetic circuit. It is dueto escape of lines of force and to the magnetic leakage through the air. The lines of force are never, under the most favorable circumstances, confined to the metallic circuit of the magnet and armature. In a simplemagnet without armature all the lines of force have to follow an airpath, and the field is at its strongest. As the magnetism is strongestat the surface near the poles, the term is sometimes understood asapplying to the surface attraction. In such case it is defined as thedistribution, on a magnetized bar or mass, of magnetic lines of force asthey emerge from its surface. Synonym--Surface Magnetization. Magnetism, Hughes' Theory of. A theory accounting for magnetic phenomena by assuming that eachmolecule is a magnet, and that in a polarized or magnetized body theyare all arranged with their poles in the same direction, while in anunmagnetized body their poles, alternating in direction, neutralize eachother. Magnetization consists in a partial rotation of the molecules so as tomake them agree in position, thus, as a resultant developing north andsouth poles at the ends of the bar. The theory is in a certain sense simpler than Ampere's theory, but isnot so generally adopted. Magnetism, Lamellar Distribution of. The distribution of magnetism in thin and uniform or "simple magneticshells, " q. V. A given distribution is termed lamellar if the substancein which it exists can be divided into simple magnetic shells, whicheither form closed surfaces, or have their edges in the surface of thesubstance. In lamellar distribution the polar area is very largecompared with the distance between opposite poles. Magnetism of Gases. Faraday experimented on this point by coloring gases with a little vaporof iodine or other colored gas, and letting them flow between the twopoles of a powerful electromagnet. In this way he found some arerepelled, some attracted, and in the case of oxygen, it is attracted atone temperature and repelled at another. At ordinary temperatures acubic yard of oxygen possesses the magnetism of 5. 5 grains of iron andwhen liquefied it is strongly attracted. Magnetism or Magnetization, Temporary. When a mass of iron is magnetized by a current, when the current ceasesthe portion of its magnetism which disappears is the temporarymagnetism; the portion retained is the residual or permanent magnetism. Magnetism, Red. A term arising from the two fluid theory of magnetism; the magnetism ofthe north pole of a magnet. (See Magnetic Fluids. ) The magnetism of thesouth pole is termed blue magnetism. Both terms originated in thepainting of magnets. They are but little used. Synonym--North Magnetic Fluid. 358 STANDARD ELECTRICAL DICTIONARY. Magnetic Remanence. The residual magnetism left in a bar of steel or other paramagneticmaterial after the application of a powerful magnet. It is distinguishedfrom coercive force, as the latter is the amount of negative magnetizingor of demagnetizing force required to reduce the remanent magnetism tozero. Synonym--Remanence--Residual Magnetism. Magnetism, Solenoidal Distribution of. The distribution of magnetism in such a way that the poles are very farapart in proportion to their area. The magnetization of a long thin barof steel illustrates solenoidal distribution. Magnetism Sub-permanent. The magnetism of a paramagnetic substance which presents a considerabledegree of permanency, but which gradually disappears, leaving thepermanent magnetism present. It is noticeable in iron or steel shipswhose magnetism gradually reduced in quantity, eventually becomes fullypermanent. Magnetism, Weber's Theory of. The molecules of a magnetizable material by this theory are supposed tobe magnets with their poles lying in every direction, and henceneutralizing each other. By magnetization these are supposed to beturned with their similar poles in the same direction, and their axisparallel, hence acting like a group of magnets. It is practicallyidentical with Hughes' theory. Magnetism, Terrestrial. The magnetism of the earth. (See Magnetic Elements. ) Fig. 228. MAGNETIZATION BY DOUBLE TOUCH. Magnetization by Double Touch. The process of magnetizing a steel bar by simultaneously stroking itwith two poles of a horseshoe magnet or with two opposite poles of twobar magnets. The poles must be close but not touching. A block of woodmay be placed between the ends if single magnets are used. The poles areplaced on the middle of the bar and carried back and forth to one end, then to the other, and so on, ending at the middle of the bar in suchdirection as to give each end the same number of strokes. The poles mustbe close together or consequent poles will be produced. If bar magnetsare used they may be held inclined at an angle of 15º to 20º with thehorizontal bar to be magnetized. The ends of the latter may rest onpoles of two other magnets, each end on a pole of the same name as thatof the magnetizing magnet on its side. (See Magnetization, Hoffer'sMethod. ) 359 STANDARD ELECTRICAL DICTIONARY. Magnetization by Separate Touch. A method of magnetization. Two magnets are used. Held in an inclinedposition two opposite poles are touched to the bar near its centre, andare drawn off to the two ends. They are returned through the air and theprocess is repeated. Magnetization by Single Touch. A method of polarizing or magnetizing steel bars, by stroking themalways in one direction with one pole of a magnet, returning it throughthe air. The stroking is best done on both sides. The stroking may beginat one end and end at the other, or it may be commenced in the center ofthe bar and be carried to one end with one pole, and the same done forthe other half with the other pole. Magnetization by the Earth. The earth imparts magnetism to iron masses. If a rod of steel is heldparallel to the inclination and in the magnetic meridian it exhibitspolarity, which by jarring or hammering, can be made to some extentpermanent. A piece of soft iron held vertically, or still better in theline of the dip as above, and which is twisted when in that position, becomes magnetized with some degree of permanence. Many other instancesare cited, such as fire-irons, lamp-posts, iron gates, lathe turnings, all of which often exhibit polarity, having been magnetized by theearth's field. [Transcriber's note: The earth's magnetic field is believed to originateit electric currents in the moving molten core. ] Magnetization, Coefficient of Induced. The coefficient (q. V. ) expressing the relation between the specificintensity of magnetization of a particle and the magnetizing force. Themagnetizing force is measured by the lines of force it can produce in afield of air. The coefficient of induced magnetization is the factor bywhich the intensity of a magnetizing field must be multiplied to producethe magnetization imparted by it to a particle of any substance. Thiscoefficient varies for different substances, and is also called magneticsusceptibility. It is distinguished from permeability as referring onlyto a particle isolated from influence of a mass of surrounding particlesof its own kind. It is definable as the intensity of the magnetizationassumed by an exceedingly long and exceedingly thin bar placed in a unitfield. If a mass of metal were placed in such a field all its particleswould become affected and within the mass no unit field could exist. Hence magnetic susceptibility (another name for this coefficient) doesnot apply to the case of large cores of electro-magnets anddynamo-armatures, but is really a theoretical rather than a practicalfigure. The sign of the coefficient of diamagnetic bodies is negative; ofparamagnetic bodies is positive. Synonym--Magnetic Susceptibility. \ 360 STANDARD ELECTRICAL DICTIONARY. Magnetization, Cycle of. A cycle of positive or of positive and negative magnetization representsthe application of a magnetizing force beginning at a fixed value, generally zero, rising to a maximum, or to a value of maximum distancefrom the initial and then returning to the original basis. It isvirtually a full wave of magnetization and may extend on both sides of azero line giving positive and negative values. Cycles of magnetization apply especially to transformers and otherapparatus of that character used with the alternating current system. Magnetization, Hoffer's Method. For horseshoe bars an armature is placed against the poles of the magnetbar to be treated. The poles of a strong horseshoe magnet are strokedover it from poles to bend and returned through the air, or vice versa. In the first case the poles will be the same as those of the inducingmagnet; in the second case they will be opposite. A maximum effect isproduced in ten strokes. The stroking should be applied to both sides. An electro-magnet may be used as inducer as shown, but an armatureshould be used; in the cut it is omitted. Fig. 229. MAGNETIZING A HORSESHOE MAGNET. Magnetization, Intensity of. The amount of magnetism induced in or present in a body. It is expressedin Magnetic Lines of Force, q. V. , per cross-sectional area. Magnetization, Isthmus Method of. A method used by Ewing in a research on the magnetization of iron invery strong fields. He used samples of iron turned down in the centre toa narrow neck, and thus concentrated the lines of force greatly. Magnetization, Elias' Method. The bar to be magnetized is surrounded by a magnetizing coil, q. V. Astrong current is passed through it, and the coil is moved back andforth a few times. Magnetization, Jacobi's Method. For horseshoe bars. The bar is placed with its poles against those of ahorseshoe magnet. A bar of soft iron, long enough to reach from outsideto outside of the legs, is laid across near the junction and is drawnalong towards the bend of the new bar and away from it. This is repeateda few times on both sides. 361 STANDARD ELECTRICAL DICTIONARY. Magnetization, Limit of. As the induction of magnetizing force increases, magnetization ofparamagnetic metals tends towards a limit, the increase in magnetizationbeing continually less and less as the metal becomes more highlymagnetized. In diamagnetic substances no limit is discernible. Synonym--Maximum Magnetization. Magnetization, Specific. The magnetic moment per gram of a substance. Magnet-keeper. A bar of iron connecting the two poles of a permanent magnet. Often thesame bar serves as armature and keeper. Magnet, Lamination of. It is advantageous to make magnets of laminated construction, or of thinplates of steel. The thin metal can be better tempered or hardened thanthick metal. A slight separation of the plates is advantageous from somepoints of view. If in actual contact there is some danger that theweaker members will have their polarity reversed by the stronger ones. This is counteracted to some extent by separation. Magnet, Long Coil. A high resistance electro-magnet; one whose coil is of thin wire ofconsiderable length. Magnet, Natural. The lodestone, q. V. ; a variety of magnetite or magnetic oxide of iron, exhibiting permanent magnetism, attracting iron, and possessing northand south poles. Magnet, Neutral Line of. A line at right angles to the magnetic axis of a magnet, q. V. , andnearly or quite at the centre, so situated with reference to the poleson either end that it marks the locus of no polarity. It has been calledthe equator of the magnet. It is defined by the intersection of theplane of no magnetism with the surface of the bar. Synonym--Magnetic Equator. Magnet, Normal. A bar or compound bar magnet, magnetized to such an extent that thecurves of the lines of force run into each other in the middle, is thustermed by Jamin. Magneto. Abbreviation for Magneto-electric Generator. (See Magneto-electricGenerator. ) Magneto Call Bell. A call operated by current from a magneto-electric generator. It is verygenerally used in telephone systems. 362 STANDARD ELECTRICAL DICTIONARY. Magneto-electric. Adj. Relating to induced electric effects due to the cutting of true magneticlines of force by, or equivalent action of or upon a conductor. Theseeffects are identical with electro-magnetic effects and are onlydistinguished from them by the field being due to a permanent magnetinstead of an electromagnet. Magneto-electric Brake. A device for bringing to rest an oscillating galvanometer needle. Itconsists essentially of a coil in circuit with a key and with thegalvanometer. On opening the circuit an inverse current is establishedby induction, tending to bring the needle to rest. Magneto-electric Generator. A current generator operating by maintaining a potential difference atits terminals, by reactions in a field of force, which field isestablished by a permanent magnet. The cut, Fig. 230, shows the general principle of construction of adirect current generator. The armature is rotated between the poles of apermanent magnet. Any of the regular types of dynamo armature can beused. From its commutator the current is taken by brushes. Fig. 230. MAGNETO-ELECTRIC GENERATOR. Fig. 231. MAGNETO-ELECTRIC GENERATOR. 363 STANDARD ELECTRICAL DICTIONARY. The cut, Fig. 231, shows an alternating current machine. In it a pair ofbobbins, wound in series, and both either right-handed or left-handed, are rotated between permanent magnet poles. The current may be taken offby two brushes bearing on two collecting rings on the axis of thebobbins, the ends of the wire being connected thereto. Or if a shockingcurrent is desired, one of the brushes or springs may strike a series ofpins forming virtually a broken or interrupted collecting ring. Thisgives a current for medical purposes. Synonyms--Magneto-dynamo--Magneto-electric Machine. Magnetograph. An apparatus for recording variations in magnetic elements. One typeincludes a magnetic needle to which a concave mirror is attached. Thelight ray from the mirror is reflected upon sensitized paper where itsmovements are photographically reproduced. The movements of the spot aredue to the movements of the needle and act as the record of the same. Magneto-Inductor. An instrument for use with a ballistic galvanometer to reproduce adefinite current impulse. Two magnets are fastened together in onestraight line, the north poles almost touching. This is mounted at theend of a rod like a pendulum, the axis of the magnets transverse to therod. The magnets are carried by a frame and oscillate at the end of therod, back and forth within a fixed coil, which is one-half the lengthof the double magnet. A bob is attached to the bottom of the frame bywhich the whole can be swung. As the magnets are of fixed value, theirtime of oscillation constant, and the coil fixed in size, the apparatusprovides a means of getting a definite instantaneous current ofidentical value whenever needed. Fig. 232. MAGNETO-INDUCTOR. 364 STANDARD ELECTRICAL DICTIONARY. Magnetometer. (a) A reflecting galvanometer, with heavy magnetic needle, dampened by acopper frame. It was devised by Weber. (b) An apparatus for measuring the intensity of magnetic force. It mayconsist of a magnet suspended by bifilar or by torsion suspension. Areflecting mirror and scale as in the reflecting galvanometer may beused to act as indicator of its motions. It is used in investigations ofthe intensity of the earth's field. If the motions of the spot of light are received on a moving strip ofsensitized paper and are thereby reproduced photographically, theinstrument is self-recording. Such an apparatus is used in the KewObservatory, Eng. , for recording the terrestrial magnetic elements. Magnetometry. The determination of the magnetic moment of a magnet. It involves the determination by experiment of--( a) the product of themagnetic moment, M, of the magnet by the horizontal component, H, of theearth's magnetism; (b) the quotient of M divided by H. Knowing these twoquantities, M is given by the formula M = SquareRoot( )M * H) * (M/H) )and if desired H is given by the formula H = SquareRoot( (M*H) / (M/H)). M*H is determined by the method of vibrations. A very long, thin magnetsuspended by a torsion filament is caused to oscillate, and its periodis determined. Calling such period T and the moment of inertia of themagnet I, we have the formula T= 2* PI * SquareRoot( I / (H*M) ) (a), whence H*M is calculated, I of course being known or separatelydetermined. Fig. 233 END-ON METHOD. Fig. 234. BROADSIDE METHOD. M/H is determined by the End-on deflection method, or the Broadsidedeflection method. In both cases the deflection of a compass needle bythe magnet in question is the basis of the work. In the end-on method AB is the magnet under examination; DE the compassneedle; a the angle of deflection; d the distance between C and themiddle of AB, which should be considerable compared with the length ofDE; 2l, the length of AB. We then have the formula tan a = (M/H) * (2d / (d^2 - l^2)^2), which if 2l is small compared to d reduces to tan a = M/Hd 3 (b), which gives M/H, a and d being known. 365 STANDARD ELECTRICAL DICTIONARY. In the broadside method the line d is the magnetic meridian, and thediagram shows the relative positions. We then have the formula tan a = (M/H) / (d2 + l2)^1. 5;which if 1 is relatively small reduces to tan a = M/(H * d3 )(C. ) [Transcriber's note: The image of the above paragraphs is included here. ] a and c or a and b can be combined giving M and H in C. G. S. Measurement. Magnetometer, Differential. An apparatus, invented by Eickemeyer, for testing the magnetic qualitiesof different samples of iron. It is very similar in construction andprinciple to the magnetic bridge, q. V. Magneto-motive Force. The force producing a magnetic field or forcing lines of force around amagnetic circuit. It is usually applied only to electro-magnets and isexpressible in turns of the wire winding multiplied by amperes ofcurrent, or in ampere-turns. Magnet Operation. A term in surgery; the use of the electro-magnet or permanent magnet forremoving particles of iron from the eye. Magnetoscope. An apparatus for detecting the presence of magnetism, without measuringits intensity. A simple magneto-scope consists of a magnetized bit ofwatch-spring suspended in a vertical glass tube by a fine filament. Abit of unmagnetized soft iron wire may be used in the same way. Thefirst has the advantage of indicating polarity; the latter merely showsmagnetic attraction. A cork may be used as base of the instrument. Fig. 235. MAGNETOSCOPE. 366 STANDARD ELECTRICAL DICTIONARY. Magnet, Permanent. A bar of steel charged with residual magnetism. Steel possesses highcoercive force in virtue of which when once magnetized it retains partof the magnetization. Permanent magnets are generally straight bars or U shaped; they aretermed bar magnets, magnetic needles, horseshoe magnets, machine magnetsand otherwise, according to their shape or uses. Magnet Pole. The part of a magnet showing strongest polarity; the part which attractsiron the most powerfully, and acts as the starting point for lines offorce. Magnet Poles, Secondary. Magnet poles are often not situated at the ends. Owing to inequality ofthe material or other causes they may occupy intermediate positions onthe magnet. Such poles are called secondary poles. Magnet Pole, Unit. A unit magnet pole is one which exerts unit force on another unit poleplaced at unit distance from it. Unit force is the dyne; unit distanceis one centimeter. Magnet, Portative Power of. The power of sustaining a weight by attraction of its armature possessedby a magnet. In general terms the adherence of the armature of a magnetto the pole varies with the square of the number of lines of force whichpass through the point of contact. Hence an increased adherence of thearmature to a horseshoe electro-magnet is sometimes obtained bydiminishing the area of contact of one pole which concentrates the linesof force. Steel magnets were frequently made with rounded ends toincrease the portative power. Magnet, Simple. A magnet made of one piece of metal, or at least magnetized as such; thereverse of a compound magnet, which is magnetized piece by piece andthen fastened together. Magnet, Solenoidal. A magnet which is so uniformly magnetized and is so long in proportionto its other dimensions that it virtually establishes two magneticpoles, one at either end. It is a long thin bar so magnetized that allits molecules would, considered as magnets, be absolutely equal. (Daniell. ) It acts like a solenoid, except that it is longer inproportion than the solenoid generally is constructed. Magnet, Sucking. A magnet coil with movable or loose axial bar of soft iron. The whole is usually mounted vertically. When a strong enough current ispassed the bar is drawn up into the coil as if by suction, whence thename. 367 STANDARD ELECTRICAL DICTIONARY. Magnet, Unipolar. No such thing as a unipolar magnet is possible. The name is given topoised or suspended magnets, one of whose poles lies in the axis ofsuspension. It is obvious that such a magnet will act, as far as itsdirective tendency and rotatory movements are concerned, as if it hadonly one pole. As shown in the cut, the pole s in both magnets lies inthe axis of suspension or directly under the filament by which they aresuspended, while the other pole n is the active pole in causing rotationor directive tendency; c c are counterweights or counterpoises. Fig. 236. UNIPOLAR MAGNETS. Magnetophone. An apparatus for producing a loud sound, involving the principles of thetelephone. A rapidly alternating or make and break current beingproduced by any means and being transmitted through the telephone givesa loud note of pitch dependent on the current producing it. Sometimes aperforated metallic disc is rotated in a magnetic field, and producesthe requisite type of current. Magnus' Law. A law of thermo-electricity. In a homogeneous circuit, however, thetemperature varies from point to point; there is no current. Whatever potential differences may be established by the variations intemperature it is evident that they must counteract each other andreduce to zero. Mains, Electric. The larger conductors in a system of electric light or powerdistribution. Make. V. To complete a circuit, as by closing a switch. Make and Break Current. A current which is continually broken or interrupted and started again. It is applied only where the "makes" and "breaks" succeed each otherwith great rapidity, as in the action of an induction coil or polechanger, etc. It has had considerable importance in litigation affectingthe Bell telephone patents, the courts holding that the original Bellpatent (No. 174, 465, of 1876, ) covered the undulating current, for thetransmission of speech. Many efforts have been made by litigants toprove that specific telephones have transmitted articulate speech by themake and break current, but without success. If this could have beenproved the assumption is that the courts would have sustained the use ofsuch device as not infringing upon the claims of the Bell patent. Malapterurus. A fish, sometimes called the thunder fish, an inhabitant of Africanrivers, occurring in the Nile and Senegal. It possesses considerableelectric power, similar to that of the gymnotus and torpedo, althoughinferior in amount. 368 STANDARD ELECTRICAL DICTIONARY. Fig. 237. MALAPTERURUS. Man-hole. The cistern-like depression in the ground for giving access to the endsof tubes in electric conduits. (See Conduit, Electric Subway. ) Marked End or Pole. The north pole or north seeking pole of a magnet, so called because itis usually marked with a notch or scratch by the maker. The south poleis called the unmarked end. Mass. The quantity of matter in a body. The C. G. S. Unit of mass is thequantity of matter in a gram. While weight varies with latitude andother circumstances, mass is invariable. The unit of mass is also defined as the quantity of matter which in abalance will counterpoise a standard mass, the gram or pound. As thegram is intended to be the mass of one cubic centimeter of water at3. 09º C. (39º F. ), the C. G. S. Unit of mass is really 1. 000013 gram. As a primary unit its dimensions are indicated by M. Mass, Electric. A term for quantity of electricity. The unit mass is such a quantity asat unit distance will act with unit force. Matter, Electric. The imaginary substance constituting electricity; a conception usedpurely as a matter of convenience. [Transcriber's note: The electron was discovered five years after thispublication. ] Matter, Radiant. Matter in the ultra-gaseous or so-called fourth state. In the gaseousstate the molecules of a gas are in perpetual kinetic motion, collidingactually or virtually with each other, rebounding from such approach, and striking also the walls of the containing vessel. But except forthese deflections, which are of enormous frequency, the paths of themolecules would be perfectly straight. In the radiant state matter exists in so high a vacuum that collisionsof the molecules rarely occur, and the molecules simply beat back andforth in straight lines from side to side of the containing vessel. A layer of gas in this condition is termed a Crookes' layer, from Prof. William Crookes, who discovered and investigated these phenomena. 369 STANDARD ELECTRICAL DICTIONARY. Luminous streams of the molecules are produced by electric highpotential discharges between electrodes. The course of the discharge isnormal, in general terms, to the surfaces of the electrodes, and reachesfrom one to the other in a curve or straight line, as the case may be. These luminous streams are deflected by a magnetic field; if brought toa focus can heat refractory material in that focus to a full white heat, and can develop phosphorescence. The latter is termed electricphosphorescence. A great variety of experiments have been devised toillustrate the phenomena of radiant matter. The vacuum is generallyproduced in a hermetically sealed glass vessel into which the electrodesare sealed, and which contain the phosphorescent substances or otheressentials for the experiments. The vessels are termed Crookes' Tubes. [Transcriber's note: Crookes reported on "radiant matter" in 1879. It isactually electrons, but he failed to distinguish them from ordinaryatoms. Thompson properly described electrons in 1897. ] Matteueci's Experiment. An experiment for showing the inductive effect of the discharge of aLeyden jar. Two glass plates are supported on standards in a verticalposition. Flat coils of wire are wound or coiled and secured to onesurface of each plate. One plate has much finer and longer wire than theother. Metal handles are connected to the ends of the coarser wire coil. The plates are placed with their coils facing each other. A Leyden jaris discharged through the coarser coil, while the handles are grasped bya person. The shock of the discharge is felt by him. Matting, Electric Floor. Matting or floor covering underlaid with burglar alarm contacts, soarranged as to be closed by anyone walking on the matting. The contactsare connected to a burglar alarm system. The object is to provide analarm if a burglar enters a house, in case he should enter a door orwindow without sounding the bell. The latter can be done by cutting outthe window or part of the door instead of opening it. Maxwell's Theory of Light. A theory of light. It is due to J. Clerk Maxwell. It supposes the phenomena of electric induction to be due to the ether, q. V. It supposes the condition of the ether when conveying light to bethe same as if exposed to the induction of rapidly alternating currentsor discharges (in this case synonymous). It therefore is anelectro-magnetic effect if the theory is correct. An electric stress such as one due to the induction of anelectrostatically charged body is not a wave-creating element or factor, but is a simple stress. But let this stress be stopped and renewed andat once it appears as a wave-forming agency. This stoppage and renewal represents evidently a discharge succeeded bya charge, or if repeated is equivalent to an intermittent current or analternating one. 370 STANDARD ELECTRICAL DICTIONARY. Again the electrostatic stress kept constant may by being carriedthrough space carry with it a wave, just as a moving projectile carriesa wave of air in advance of itself. Admitting this much the following consequences follow: Since in non-conductors the displacement produces a restitution force, which varies as the displacement which is requisite or is a criterionfor the propagation of waves, while in conductors no such force ismanifested and the electric energy appears as heat, it follows thatlight vibrations are not possible in conductors, becauseelectro-magnetic waves do not exist in them when they are in circuit, and conductors should be opaque, while the reverse is true fornon-conductors. (Daniell. ) This is carried out often enough to make a striking evidence in favor ofMaxwell's theory. The velocity of propagation of an electro-magnetic disturbance in anon-conductor should be equal to that of light. This constant is provedby mathematical considerations, to be approximately the same as theratio of the electrostatic to the electromagnetic unit of intensity orquantity. This ratio is 3E10 (30, 000, 000, 000), which is almost exactlythe velocity of light. It also follows from what has been said that if an electrostaticallycharged body were whirled around a galvanometer needle at the rate of3E10 revolutions per second it should affect it like a circulatingcurrent. This rate of rotation cannot be attained, but Rowland has mademanifest the effect of a rotating statically charged body upon amagnetic needle. The above is the merest outline of Maxwell's theory. The fulldevelopment must be studied in his own and succeeding works. Mayer's Floating Magnets. An experiment due to Prof. Mayer. A number of sewing needles aremagnetized and thrust into bits of cork, almost all the way through, with their like poles projecting. They are floated in a basin of waterand take, under the effects of attraction and repulsion, when approachedby a magnet pole, regular geometric positions, marking out the positionsof angles of polygons. Measurements. The determination of the value of quantities; determination of thefactor by which the unitary value must be multiplied to produce thequantity under examination. Such are the measurement of the voltage of agalvanic battery, or of the ohms of resistance of a conductor. Electricity has been termed the science of measurement. Meg or Mega. A prefix, meaning one million times. A megohm is one million ohms; amegerg is one million ergs; a megadyne is one million dynes. 371 STANDARD ELECTRICAL DICTIONARY. Fig. 238. MAYER'S FLOATING MAGNETS. Mercury. A metal; one of the elements; symbol, Hg; atomic weight, 200 ;equivalent, 200 or 100; valency, 1 and 2. It is a conductor of electricity. The following data are 0º C. (32º F. ) Relative Resistance, 62. 73 Specific Resistance, 94. 32 microhms. Resistance of a wire, (a) 1 foot long, weighing 1 grain, 18. 51 ohms. (b) 1 foot long, 1/1000 inch thick, 572. 3 " (c) 1 meter long, weighing 1 gram, 12. 91 " (d) I meter long, 1 millimeter thick 1. 211 " Resistance of a 1 inch cube, 37. 15 microhms. Percentage increase of resistance per degree C. 1. 8° F. At about 20° C. (68° F. ), . 72 per cent. Electro-chemical equivalent (Hydrogen = . 0105), 2. 10 mgs. 1. 05 " 372 STANDARD ELECTRICAL DICTIONARY. Mercury Cup. A cup of iron, wood or some material that does not amalgamate or isunattacked by mercury, which is filled with mercury and made anelectrode of a circuit. By dipping the other terminal of the circuitinto the mercury a very good contact is obtained. It is well to coverthe mercury with alcohol. The cup may be filled so that the mercuryrises in a meniscus or semi-globule above its edges. For some purposes this form is useful, as for contacts with the end of aswinging wire or pendulum, because in such cases the contact can be madewithout the contact point entering the cup. The point swings through theprojecting meniscus without touching the edges of the cup. A mercury cupand contact constitute a mercury break. Meridian, Astronomical. The great circle passing through the north and south poles of thecelestial sphere. It lies in a plane with the corresponding geographicalor terrestrial meridian. Meridian, Geographic. The true north and south meridian; the approximate great circle formedby the intersection of a plane passing through north and south poles ofthe earth with the earth's surface. 373 STANDARD ELECTRICAL DICTIONARY. Fig. 239. SCHALLENBERG'S ALTERNATING CURRENT METER. Meter, Alternating Current. A meter for measuring alternating current, as supplied to consumers, from an alternating current system. Like most commercial meters its onlyfunction is the measurement of quantity; the potential difference ismaintained at a constant figure by the generating plant. The cut shows the Schallenberg meter. It is simply an alternatingcurrent motor (see Motor, Alternating Current), with air vanes mountedon its spindle. A main coil passes all the current. Within this is asecond coil complete in itself, and not touching or connecting with theother. The latter is built up of copper rings. Within the two coils, andconcentric with both is a disc of copper carried by a vertical spindle. The same spindle carries air vanes, and is free to rotate. As it does soit moves the indicating machinery. The current in the outer coil induces one in the inner coil. Owing tolag, the current in the inner one differs in phase from that in theouter one, and a rotatory field is produced. The copper disc acquiresinduced polarity, and rotates with speed which normally would be inproportion to the square of the current. But the object of the meter isto register the current only. The air vanes effect this. The resistanceof the air to their motion causes the rate of rotation to vary directlyas the speed. Meter Bridge. A form of Wheatstone's bridge in which one lateral pair of arms isrepresented by a straight wire. The other pair comprise a knownresistance, and the resistance to be determined. The galvanometer isconnected on one side between the known and unknown resistance. On theother side its connection is moved back and forth along the straightwire until the balance is secured and the galvanometer reads zero. The relative lengths of wire intercepted between the two ends thereofand the movable galvanometer connection are proportional to theresistance of these parts and give the necessary data with the one knownresistance for determining the unknown resistance. 374 STANDARD ELECTRICAL DICTIONARY. In the original meter bridge the wire was one meter long, whence itsname, and was stretched straight. In more recent examples the wirevaries in length and in one form is bent into a circle or spiral, so asto make the instrument more compact. The contact is not a sliding one, but is adjusted by trial. The contactpiece is slid along, but not touching the wire, and from time to time ispressed down against the wire. This prevents wear of the wire. The wiremay be made of platinum or of platinum-iridium alloy. The latter isvery hard and not easily worn out. Sometimes, as shown in the cut, three parallel wires are stretched alongthe baseboard of the instrument, and arranged so that a single wire, twowires or three wires in series can be used for the proportional sides ofthe bridge, thus making it a two-meter or three-meter bridge as desired. On the other hand some are made of restricted length, as a half orquarter meter only. Fig. 240. METER BRIDGE. In the cut J K is the wire, traversed by the contact key. By moving thecontact C back and forth in the slot it can be brought over any of thethree divisions of the wire. H is the handle for depressing the key. Sis a flat spring, carrying the contact piece and holding it up from thewires, except when pressed downwards. As shown in the cut, it is in usefor calibrating a voltmeter V, by Poggendorff's method, G being thegalvanometer and r1 and r2 being resistances. Synonyms--Slide Bridge--Slide Balance. Meter Candle. A unit of illuminating power; the light given by one standard candle ata distance of one meter. The ordinary units of illuminating power arealtogether relative; this one is definite. 375 STANDARD ELECTRICAL DICTIONARY. Meter, Chemical Electric. A current meter in which the current is determined by the amount ofchemical decomposition which it can effect. In the Edison meter thesolution is one of zinc sulphate. Two electrodes of zinc are immersed init, and a fractional part of the current is passed through it. The gainin weight of one electrode and the loss in the other are proportional tothe current. Both electrodes are weighed periodically, one acting ascheck upon the other. Meter, Current. An instrument for measuring the quantity of electricity in current formsupplied to consumers. It may be of various types. The general principleinvolved is that in commercial installations for incandescent light andpower supply a fixed potential is usually maintained, the multiple arcsystem being employed. Hence all that is requisite is to measure thecoulombs or the ampere-hours to know what quantity of energy has beensupplied. Meter, Electro-magnetic. A current meter in which the current is measured by its electro-magneticeffects. Meter-millimeter. A unit of resistance. (See Resistance, Meter-millimeter. ) Meter, Thermal Electric. A current meter in which the current is measured by the heat it impartsto a conductor. In one meter a very light helix of mica is poisedhorizontally over a conductor, and the whole is enclosed in a case. Asthe wire is heated it causes an ascending current of air which rotatesthe vane, and the latter moves delicate clockwork which moves indicatinghands. The hotter the wire the more rapidly the air ascends, andconsequently the speed of the vane is proportional to the current, because the heat of the conductor is proportional thereto. Meter, Time Electric. An electric meter which measures the length of time during which currentis used. It assumes a constant current and potential. It is virtually aclock, which is turned on when the current passes, and is turned offwith the current. Meter, Watt. A combined current and potential meter. It is constructed on the generallines of a Siemens' Electro Dynamometer. If in it one coil is made ofcoarse wire and is placed in series with the current conductor, and ifthe other is wound with fine wire and is connected as a shunt from pointto point whose potential difference is to be determined, the instrumentbecomes a watt meter. Synonym--Energy Meter. Methven Standard or Screen. A standard of illuminating power. It is the light emitted by athree-inch Argand gas flame through a rectangular aperture in a silverplate carried by a screen. The aperture is of such size and so fardistant from the flame as to permit the passage of exactly two candlesilluminating power. Fig. 241. METHVEN SCREEN 376 STANDARD ELECTRICAL DICTIONARY. Mho. A unit of conductance, not in very general use. It is the reciprocal ofthe ohm. Thus a resistance of ten ohms is a conductance of one-tenthmho. Mica. A natural mineral, a silicate of several oxides; muscovite. It is usedas an insulator and dielectric. Its resistance per centimeter cube afterseveral minutes electrification at 20º C. (68º F. ) is 8. 4E13 ohms(Ayrton). Its specific inductive capacity is 5, air being taken at 1. Mica, Moulded. An insulating material, whose body is made of mica pulverized andcemented together with heat and pressure and some suitable cement. Shellac is often used as the cement. Micro. A prefix meaning "one-millionth of;" a micro-farad is one-millionth of afarad. Micrometer. An instrument for measuring small distances or small differences. Itgenerally is based upon an accurate screw which may have a worm wheelfor head, actuated by a worm or helix with graduated head, so thatexceedingly small advances of the screw may be produced. The pitch ofthe screw being known its actual advance is known. Micrometer, Arc. A micrometer for measuring the distance between voltaic arc electrodes. Micron. A unit of length. It is one-millionth of a meter or fourone-hundred-thousandths of an inch. 377 STANDARD ELECTRICAL DICTIONARY. Microphone. An apparatus which includes a contact of variable resistance; suchresistance can be varied in amount by slight vibrations, such as thoseproduced by sound waves. The apparatus in use forms part of a circuitincluding a telephone and current generator. As the contact is variedthe resistance of the circuit and consequently the current intensitychanges and sounds are emitted by the telephone corresponding to suchchanges. If the microphone is spoken to, the telephone will emitcorresponding sounds, reproducing the voice. It has been found in practice that carbon gives the best microphonecontact. One of the simplest and earliest forms is shown in the cut. Ashort rod or pencil of carbon, A, such as used in batteries, issharpened at the ends and rests loosely in a vertical position betweentwo blocks of carbon, C C, in each of which a hole is drilled to receiveone of the points. The blocks are carried on a standard and base D. Theblocks are connected with two terminals x, y, of a circuit, including atelephone and battery. There are two contacts to be disturbed. If delicately adjusted a fly walking over the base-board will disturbthe contacts enough to produce sounds in the telephone. These sounds arepossibly not due only to sound waves, but in part to absolute mechanicaldisturbances. The various forms of telephone transmitter are generally microphones. Fig. 242. MICROPHONE. Microphone Relay. A combined microphone and telephone. A microphone is placed close to thediaphragm of a telephone. The slight sound waves emitted by thetelephone affect the microphone and are repeated in its circuit. Themicrophone circuit includes a local battery and telephone. Microtasimeter. An apparatus for indicating minute changes in temperature or atmosphericmoisture. 378 STANDARD ELECTRICAL DICTIONARY. A button of compressed lampblack is placed in series with a battery andgalvanometer. A strip of some substance, affected in its length eitherby heat or by moisture, is held pressing against the button. A slightchange in length of the strip varies the resistance of the button andhence affects the galvanometer. In this way exceedingly slight changesin heat or moisture may be indicated. For heat indications vulcanite may be used. The heat of the hand heldnear it is enough to affect the galvanometer. For moisture a slip ofgelatine is used. The moisture of a damp slip of paper two or threeinches distant is sufficient to affect the galvanometer. In the cut, Fig. 2, shows the general distribution of the apparatus incircuit with a battery and galvanometer. C is the base of the apparatus, from which the standard, B, with adjusting screw, H, rises. The strip ofvulcanite is held between I and G. Within D is the carbon button (F inFig. 3) pressed between G and E; A is a standard to carry the parts lastdescribed. In Fig. I it is shown as part of a Wheatstone bridge, a, band c being resistance coils; l the tasimeter, and g the galvanometer. If a balance is secured, any variation in the resistance of thetasimeter will disturb the galvanometer. Synonym--Tasimeter. Fig. 243. MICROTASIMETER. 379 STANDARD ELECTRICAL DICTIONARY. Mil. A unit of length; one-thousandth part of a lineal inch. It is equal to. 025399 millimeter;. 000083 foot;. 001000 inch. Mil, Circular. A unit of area; employed in designating the cross-sectional area ofwires and other circular conductors. It is equal to . 78540 square mil; . 000507 square millimeter; 7. 8E-7 (. 00000078) square inch. If the diameter of a wire is given in mils, the square of its diametergives its cross-sectional area in circular mils. Mil-foot. A unit of resistance. (See Resistance, Mil-foot, Unit of). Mil, Square. A unit of area; one-millionth of a square inch. It is equal to . 000645 square millimeter; 1. 2733 circular mil; . 000001 square inch. Milli. A prefix; one-thousandth. Thus a milligram is one-thousandth of a gram;a millimeter is one thousandth of a meter. Milligram. A unit of weight ; one-thousandth of a gram, q. V. It is equal to . 015432 grain; . 000032 troy ounce. Millimeter. A unit of length; one-thousandth of a meter. It is equal to 39. 37079 mils; . 03937 inch; . 00109 yard. 380 STANDARD ELECTRICAL DICTIONARY. Milli-oerstedt. A proposed but not adopted unit of current; one-thousandth of anoerstedt. It is equal to one-thousandth of an ampere. [Transcriber's note: oersted: 1. CGS unit of magnetic intensity, equalto the magnetic pole of unit strength when undergoing a force of onedyne in a vacuum. 2. Formerly, the unit of magnetic reluctance equal tothe reluctance of a centimeter cube of vacuum between parallelsurfaces. ] mm. Contraction for millimeters. Molar. Referring to phenomena of mass as gravitation. Mechanicsgenerally treats of molar laws and phenomena. [Transcriber's note: Molar, or mole, often refers to a quantity of asubstance containing an Avagadro number (6. 02E23) of molecules--a weightequal to the atomic weight of the molecule. For example, a mole ofhydrogen (H2) is 2. 015 grams; sodium chloride (NaCl) is 58. 443 grams. ] Molar Attraction. The attraction of mass for mass; gravitation. Synonyms--MassAttraction--Gravitation. Molecular Affinity. The attraction of molecules for each other as seen in the formation ofdouble salts, the combining of water of crystallization with a salt, andin other cases; a phase of affinity belonging to chemistry, althoughoutside of true atomic attraction. Molecular Attraction. The attraction of molecules; physical affinity. Cohesion, the attractionof similar molecules for each other, and adhesion, that of dissimilarmolecules, are examples. This should be distinguished from molecularaffinity, a phase of chemical force. Molecular Bombardment. When a gas contained in a vessel is brought to a sufficient state ofrarefaction the molecules cease to be subject to the laws of diffusion, but move back and forth in straight lines from side to side of thevessel. Their courses can be affected by electric discharge, which cancause them to all impinge upon one of the electrodes, the positive one, producing luminous effects. The path, if referred to the negativeelectrode, tends to be normal to its surface, so that the resultant pathmay be curved, as the stream of molecules go to the positive electrode. The fanciful name of molecular bombardment is given to the phenomenon, the luminous effect being attributed to the impinging of the moleculesagainst the positive electrode as they are projected from the positive. The course of the molecules is comparable to the stream of carbonparticles from the positive to the negative electrode in an arc lamp. (See Matter, Radiant. ) Molecular Chain. The theoretical rows of molecules supposed to extend from anode tocathode in an electrolytic cell (see Cell, Electric--Grothüss'Hypothesis) are called molecular chains. 381 STANDARD ELECTRICAL DICTIONARY. Molecular Rigidity. The tendency of the molecules of a mass to retain their position in amass in resistance to polarizing or depolarizing force, the first beingthe effect of a magnetic field. It is the theoretical cause of coerciveforce, q. V. , and of residual magnetism. (See Magnetism, Residual. ) Molecule. The smallest particle of matter that can exist alone. It is made up ofatoms, but an atom can never exist alone, but only, with one or twopossible exceptions, combined with one or more other atoms as amolecule. The molecules under present conditions are not in constantcontact with each other, but are perpetually vibrating through paths, insolids probably in defined paths, in liquids and gases in perpetuallynew paths. The molecules collide with each other and rebound. Thismotion is the kinetic motion termed heat. At the absolute zero--minus273. 72° C. (-460. 7° F. ) the molecules would be in contact and quiescent. In the gaseous state the molecules of most substances occupy the samevolume; those of a few elements occupy one-half and of others twice thenormal volume. The mean free path of the molecule of hydrogen is about1/20, 000 mm. (1/508, 000 inch) (Maxwell) or twice this length (Crookes), the collisions in hydrogen are about 17, 750 millions per second; thediameter is about 8/10, 000, 000 mm. (8/254, 000, 000 inch) ; A particle ofmatter 1/4, 000 mm. (1/102, 000 inch) contains, it is supposed, about40, 000 molecules. The results of different authorities vary so widely asto deprive the subject of much of its interest. A Sprengel pump, such asused for exhausting Geissler tubes, or incandescent lamp bulbs, mayleave only one hundred-millionth (1/100, 000, 000, ) of an atmospherepresent, giving the molecules a capability of an average free path ofvibration 33 feet long. Moment. When a force is applied so as to tend to produce rotation around apoint, the product of the force by the shortest distance from the pointof rotation to the extension of the line of the force. Such distance isthe perpendicular to the extension of the line through the point ofrotation. Mordey Effect. A phenomenon observed in dynamo armatures. At full loads the hysteresisdecreases. The effect is thus expressed by S. P. Thompson. "When anarmature core is rotated in a strong magnetic field, the magnetizationof the iron is being continually carried through a cycle, but in amanner quite different from that in which it is carried when themagnetizing force is periodically reversed, as in the core of atransformer. Mordey has found the losses by hysteresis to be somewhatsmaller in the former case than in the latter. " Morse Receiver. The receiving instrument formerly universally used in the Morse system. It is now but little employed, the sounder having displaced it. Severaltypes were invented. It consists of machinery which carries a reel of paper ribbon arrangedto be fed over a roller by clockwork. A pencil, inking roller, orembossing stylus (for the latter the roller must have a groove) iscarried by an arm with restricted range of vibration just over the paperand roller. The armature of an electro-magnet is attached to the arm. When the magnet is excited the armature is attracted and the markingdevice is pressed on the paper. If the clockwork is in operation themarker will make a line as long as the armature is attracted. Whenreleased no mark will be produced. In this way the dots and dashes ofthe Morse code are made on a ribbon of paper. As an inking arrangement a small roller is carried by the end of thevibrating arm. The embosser, or dry point stylus, was very extensivelyused. The clockwork was generally driven by descending weights. Synonym--Morse Recorder. 382 STANDARD ELECTRICAL DICTIONARY. Mortar, Electric. An electric toy which may have various modifications. In the cut awooden mortar with recess to receive a ball is shown. Two wires enterthe base but do not touch. On placing the ball in position and passing aspark from a Leyden jar across the interval between the wires, the heatand disturbance are enough to project the ball. Gunpowder may be used, the discharge being passed through a wet string to prolong the spark. Fig. 244. ELECTRIC MORTAR. Motor, Compound or Compound Wound. A motor which has two windings on the field magnets, one in parallelwith that on the armature, the other in series therewith, exactly as ina compound dynamo. (See Dynamo, Compound. ) Motor, Differential. A differentially wound motor; with a compound wound field, whose seriescoil and shunt coil are wound in opposition to each other. It isvirtually a compound wound dynamo. (See Dynamo, Compound Wound. ) Motor, Electric. A machine or apparatus for converting electric energy into mechanicalkinetic energy. The electric energy is generally of the dynamic orcurrent type, that is to say, of comparatively low potential andcontinuous or virtually continuous flow. Some electrostatic motors have, however, been made, and an influence machine can often be operated as astatic motor. Electric motors of the current type may be divided into twoclasses--direct current and alternating current motors. Direct current motors are generally based on the same lines ofconstruction as dynamos. One of the great discoveries in modernelectricity was that if a current is passed through a dynamo, thearmature will rotate. This fact constitutes the principle of thereversibility of the dynamo. 383 STANDARD ELECTRICAL DICTIONARY. Motors built on the dynamo model may be series wound, shunt wound, orcompound wound, or of the magneto type, in the latter case having afixed field irrespective of any current sent through them. The field maybe produced by an electro-magnet separately excited and unaffected bythe current sent through the motor. A current passed through a magneto or motor with separately excitedfield will turn it in the direction opposite to that required to producethe same current from it were it worked as a generator. A current passed through a series wound motor acts exactly as above. Both these facts follow from Lenz's law, q. V. A current passed through a shunt wound motor acts oppositely to theabove. The direction of rotation is the same as that required to producea current of the same direction. This is because the field being inparallel with the armature the motor current goes through the magnetcoils in the direction the reverse of that of the current produced inthe armature when it is used as a dynamo. Hence this also carries outLenz's law. The compound wound motor acts one way or the other according as itsshunt or series winding preponderates. The two may exactly balance eachother, when there will be no motion at all. The series connections of acompound wound dynamo should therefore be reversed, making both seriesand shunt work in unison, if the dynamo is to be used as a motor. The general principles of the electric motor of the dynamo, orcontinuous rotation type, can only be outlined here. The current passingthrough the field magnets polarizes them and creates a field. Enteringthe armature by the brushes and commutators it polarizes its core, butin such a way that the north pole is away from the south pole of thefield magnet, and the same for the south pole. Hence the armaturerotates. As it does this the brushes connect with other commutatorsections, and the poles of the armature are shifted back. This actioncontinues indefinitely. Another class of motors is of the reciprocating type. These are now verylittle used. (See Motor, Reciprocating. ) One valuable feature of continuous rotation electric motors is the factthat they absorb energy, to a great extent proportional in amount to thework they have to do. The rotation of the armature in the field of themotor involves the cutting of lines of force by its coils. Thisgenerates an electro-motive force contrary in direction to thatproducing the actuating current. The more rapid the rotation the greateris this counter-electro-motive force. The motor armature naturallyrevolves faster with diminished resistance to the motion of thearmature. This increases the counter-electromotive force, so that lessenergy is absorbed. When the motor is called on to do work, the armaturerotates more slowly, and the counter-electro-motive force diminishes, sothat the machine absorbs more energy. (See Jacobi's Law. ) 384 STANDARD ELECTRICAL DICTIONARY. Motor Electro-motive Force. The counter-electro-motive force of a motor. (F. J. Sprague. ) A motor rotates in virtue of the pull of the field magnet upon the polesof the core of its armature. In responding to this pull the windings ofthe armature cuts lines of force and hence generates acounter-electro-motive force, for which the above term was suggested. Motor-Generator. A combined motor and generator used to lower the potential difference ina portion of a circuit, e. G. , that part within a building. A motor-generator is a dynamo whose armature carries two commutators, with two separate windings, one of fine wire of many turns, the other ofcoarse wire of few turns. If the potential of the system is to belowered, the main current is passed through the fine winding. Thiscauses the armature to turn motor-fashion, and a potential difference isgenerated by the rotation of the large coils in the field. Thispotential difference is comparatively low and by properly proportioningthe windings may be lowered to as great a degree as required. The same apparatus may be inverted so as to raise potential difference. It acts for continuous current systems as the induction coil transformerdoes for alternating current systems. Synonym--Continuous Current Transformer. Motor, Multiphase. A motor driven by multiphase currents. It is arranged in general termsfor distribution of the multi phase currents in coils symmetricallyarranged around the circle of the field. These coils are wound on coresof soft iron. A rotating field is thus produced, and a permanent magnetor a polarized armature pivoted in such a field will rotate with thefield, its poles following the poles of the rotatory field. The cut, Fig. 245, illustrates the principles of action of a four phasecurrent motor, connected to a four phase current dynamo or generator. The generator is shown on the left hand of the cut and the motor on theright hand. In the generator the armature N S is supposed to be turnedby power in the direction shown by the arrow. Each one of the pair ofcoils is wound in the reverse sense of the one opposite to it, and thetwo are connected in series with each other, and with a correspondingpair in the motor. The connection can be readily traced by the letters AA', a a' for one set of coils and B B' b b' for the other set. 385 STANDARD ELECTRICAL DICTIONARY. For each rotation of the armature two currents, each in oppositedirection, are produced in A A', and the same is the case for B B'. These currents which have an absolutely constant relation of phase, andwhich it will be seen alternate four times for each rotation of thearmature, regulate the polarity of the field of the motor. The resultantof their action is to keep the poles of the field magnet of the motorconstantly traveling around its circle. Hence the armature N S of themotor, seen on the right hand of the cut, tends to travel around alsoits north and south poles, following the south and north poles of therotatory field respectively. Fig. 245. FOUR-PHASE CURRENT GENERATOR AND MOTOR. It is not essential that the armature should be a magnet or polarized. Any mass of soft iron will by induction be polarized and will berotated, although not necessarily synchronously, with the rotatoryfield. Any mass of copper, such as a disc or cylinder, will haveFoucault currents induced in it and will also rotate. The onlycomponents of such currents which are useful in driving the motor arethose which are at right angles to the lines of force and to thedirection of motion. A very good type of armature based on theseconsiderations is a core of soft iron wound with insulated copper wirein one or more closed coils; and so wound as to develop the currents ofproper direction. Such an armature is used in the Tesla alternating current motor. Anefficiency of 85 per cent. Has been attained with some of the Teslamotors. Motor, Prime. A machine used for producing mechanical motion against resistance. Itmay operate by converting heat or any other form of kinetic or potentialenergy into mechanical energy of the moving type. A steam-engine and awater-wheel are examples of prime motors. Motor, Reciprocating. The early type of motor depending upon reciprocating motion, such as themotion of a coil in a solenoid. These were based upon the lines of asteam engine, and have been abandoned except for special purposes wherereciprocating motion is especially required, as in the case of rockdrills. 386 STANDARD ELECTRICAL DICTIONARY. Fig. 246. RICORDON'S RECIPROCATING MOTOR. In the cut, B is an electro-magnet; A is an armature; E a pole piece. The current enters by the springs, b b, and by commutation is suppliedand cut off alternately, thus maintaining a reciprocating movement ofthe armature and rotation of the fly-wheel. Synonym--Pulsating Motor. Motor, Series. A motor whose winding on the armature is in series with the winding onthe field. It is similar to a series dynamo. (See Dynamo, Series. ) Motor, Shunt. A motor whose winding on the armature is in parallel with the winding onthe field magnets. It is similar to a shunt wound dynamo. (See Dynamo, Shunt. ) Fig. 247. MULTIPLE ARC CONNECTION. Multiple. A term expressing connection of electric apparatus such as batterycouples, or lamps in parallel with each other. In the ordinaryincandescent lamp circuits the lamps are connected in multiple. Synonym--Multiple Arc. 387 STANDARD ELECTRICAL DICTIONARY. Multiple Arc Box. A resistance box arranged so that the coils may be plugged in multipleinstead of in series. Such can be used as a rheostat, as the resistancecan be very gradually changed by putting the coils one by one intoparallel with each other. Thus by adding in parallel with a 10 ohm coila 10, 000 ohm coil the resistance is decreased to 9. 999001 ohms, and thusthe resistance can be very slowly changed without sudden stops or abruptchanges. [Transcriber's note: The correct value is 9. 99001] Multiple Series. Arrangements of electric apparatus in a circuit in a number of series, which minor series are then arranged in parallel. The term may be usedas a noun, as "arranged in multiple-series, " or as an adjective, as "amultiple-series circuit. " Fig. 248. MULTIPLE SERIES CONNECTION. Multiple Switch Board. A switch board on whose face connecting spring jacks or other devicesare repeated for the same circuits, so that different operators haveeach the entire set of connections repeated on the section of the boardimmediately in front of and within their reach. This multiplication ofthe same set of connections, giving one complete set to each operator, gives the title "multiple" to the type of switch board in question. Thetypical multiple switch board used in telephone exchanges is the bestexample of this construction. The calling annunciators of thesubscribers are distributed along the bottom of the board extending itsfull length. To each operator a given number is assigned, all withinreach of the right or left hand. This gives five or six feet length ofboard to each, and an operator only responds to those subscribers withinhis range. But anyone of his subscribers may want to connect with any ofthe others in the entire central station. Accordingly in front of eachoperator spring jacks are arranged, one for each of the entire set ofsubscribers connected in that office. The operator connects as requiredany of the calling subscribers, who are comparatively few, to any one ofthe large number served by the central station. Thus the entire set ofsubscribers' spring jacks are multiplied over and over again so as togive one set to each operator. 388 STANDARD ELECTRICAL DICTIONARY. Multiple Wire Method for Working Electro-magnets. A method for suppressing sparking in working electro-magnetsintermittently. The magnet core is wound with a number (from four totwenty) of separate layers of fine wire. A separate wire is taken foreach layer and all are wound in the same direction, from one end to theother of the space or bobbin without returning. The ends are then joinedso as to bring all the wires in parallel. The effect of this is that asthe coils vary in diameter the time constants of each is different fromthat of the others, the coefficient of self-induction being less, andthe resistance being greater for the coils farthest from the centralaxis. Thus the extra currents run differently in the different coils, and only a comparatively small spark can be produced owing to thedivision of forces thus brought about. Fig. 249. DIAGRAM ILLUSTRATING MULTIPLE WIRE WORKING. Multiplex Telegraphy. Any system of telegraphy transmitting more than four messagessimultaneously over a single wire. Properly it should apply to alltransmitting more than one, but conventionally has the above restrictedmeaning, distinguishing it from duplex and quadruplex telegraphy. Multiplying Power of a Shunt. When a resistance is placed in parallel with a galvanometer on a circuitthe following relation obtains. Let s and g equal the resistances of theshunt and galvanometer respectively, S and G the currents in amperespassing through them, V the potential difference between their commonterminals, and A the whole current in amperes. Then we have A = ( (s + g ) / s ) * Gand ( (s + g ) / s ) is termed the multiplying power of the shunt, as itis the factor by which the current passing through the galvanometer mustbe multiplied by to produce the total current. Muscular Pile. A species of voltaic battery, often termed Matteueci's pile, made up ofalternate pieces of muscle cut longitudinally and transverselyrespectively. The different pieces represent the elements of a battery, and their difference of potential is naturally possessed by the pieces. Myria. A prefix; one million times. Thus myriavolt means one million volts. [Transcriber's note: Contemporary usage is mega, as in megavolt. ] 389 STANDARD ELECTRICAL DICTIONARY. N. (a) Symbol for north pole or north-seeking pole of a magnet. (b) Symbol for the number of lines of force in a magnetic circuit. Nairne's Electrical Machine. The cylinder electrical machine, q. V. Napierian Logarithms. A series of logarithms the base of whose system is 2. 72818. They arealso called hyperbolic logarithms. Nascent State. An element just separating from a combination possesses at that timehigher affinities than after separation, and can effect more powerfulchemical changes. It is sometimes attributed to a differential time of existence in theatomic modification, before the freed atoms have united to formmolecules. Natural Currents. A term for earth currents. (See Current, Earth. ) Needle. (a) A term applied to a bar magnet poised horizontally upon a verticalpoint, or suspended in a horizontal position by a filament. Thus themagnet in a mariner's compass, which may be a substantial bar magnet, iscalled a magnetic needle. (b) An indicator in general shape like the hand of a clock. (SecAnnunciator, Needle- Telegraph, Needle. ) Needle of Oscillation. The magnetic needle poised horizontally, and used for measuring theintensity of the earth's magnetic field, or of an artificial magneticfield, by the method of oscillations. The intensities of the field isinversely as the square of the number of oscillations performed in agiven time. Needle, Telegraphic. The index in needle telegraphy (see Telegraph, Needle), whose motionsindicate the characters it is desired to transmit. Negative Charge. One of the two kinds of electric charges. The other is the positive. By the double fluid hypothesis this is assumed to be a charge of aparticular kind of electricity--negative electricity. By the single fluid hypothesis it is supposed to be caused by theabsence of part of the normal electricity of a surface. The reverse isheld by some theorists. The subject is so purely theoretical that neither of the two hypothesesis accepted as final. [Transcriber's note: Current is a wire is the motion of negativeelectrons. Current in a electrolyte is the motion of positive ions andnegative ions. Current in a plasma is the motion of electrons andpositive ions. ] 390 STANDARD ELECTRICAL DICTIONARY. Negative Electricity. The kind of electricity with which a piece of amber is charged byfriction with flannel; resinous electricity. (See Electrostatic Series. ) In a galvanic battery the surface of the zinc plate is charged withnegative electricity. According to the single fluid theory negative electrification consistsin a deficiency of electricity. [Transcriber's note: Negative electrification is an excess ofelectrons. ] Negative Element. In a voltaic cell the plate not dissolved by the solution; the one whichis positively charged; the copper, platinum, or carbon plate in theusual type of battery. The current is assumed to flow from negative element to positive element(the zinc plate) through the wire or other external conductor. Nerve Currents. Currents of electricity obtained from nerves. They are much more feeblethan those obtained from muscle, but are produced in the same generalways. Network. Conductors in parallel and crossing each other, with connections at thejunctions. The term is sometimes so loosely applied as to include parallelconductors. Neutral Line of Commutator. The diameter of a commutator which connects its Neutral Points, q. V. ;sometimes termed the diameter of commutation; the diameter approximatelyat right angles with the lines of force. The commutator brushes areapplied at the extremities of this diameter. Neutral Point of a Commutator. The points of a commutator at which no lines of force are cut; thepoints at the extremities of a diameter which, except for the lag, wouldbe at right angles to the lines of force; the points at which thebrushes touch the commutator. Neutral Point, Thermo-electric. A temperature marking a point of no thermo-electric difference ofpotential. If the junctions of a thermo-electric couple are attemperatures, one a little over and the other an equal amount under theneutral point, no current will be developed. At the neutral point thethermo-electric polarities are reversed. Differences of temperatureabove it give currents of reverse direction to those given bycorresponding differences below it. For an iron-copper couple theneutral point is 274. 5° C. (526° F. ) Synonym--Neutral Temperature. Neutral Relay Armature. An unpolarizable armature for use with a relay; an armature of soft ironor iron wire; as distinguished from a polarized armature. 391 STANDARD ELECTRICAL DICTIONARY. Neutral Wire. The central wire in the three wire system, q. V. , of electricdistribution; the wire connected to a point between the two dynamos, orotherwise to the central point of the current generator. Fig. 250. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE. Neutral Wire Ampere Meter. An ampere meter connected in the circuit of the neutral wire todetermine the current passing through it. Such determination is for thepurpose of ascertaining how much more work is being done by one of thelateral leads than by the other. Synonym--Balance Ampere Meter. N. H. P. Symbol or contraction for "nominal horse power. " This is a basis forrating the size of an engine. Nickel. A metal; one of the elements; atomic weight, 58. 8 ; equivalent, 29. 4;valency, 2; specific gravity, 8. 8. It is a conductor of electricity. Relative resistance, annealed (Silver = 1), 8. 285 Specific Resistance, 12. 47 microhms. Resistance of a wire (a) 1 foot long, weighing 1 grain, 15. 206 ohms. (b) 1 foot long, 1/1000 inch thick, 74. 963 " (c) 1 meter long, weighing 1 gram, 1. 060 " (d) 1 meter long, 1 millimeter thick, . 1587 " Resistance of a 1-inch cube, 4. 907 microhms. Electro-chemical equivalent, (Hydrogen = . 0105) . 3087 mgs. It is strongly paramagnetic, but loses this quality at 350º C. (662º F. ) It is important as a constituent of German silver, an alloy much usedfor resistance coils. Nickel, Bath. A bath for the electro-deposition of nickel. A great manyformulae have been given. Metallic nickel is dissolved in 1 vol. Sulphuric acid mixed with 2 vols. Water. Neutralize with ammonia, andadd of ammonium sulphate one-half the weight of metallic nickeloriginally used; 135 parts of nickel will be enough for a bath of 10, 000parts. 392 STANDARD ELECTRICAL DICTIONARY. Other formulae are as follows: Double nickel-ammonium sulphate, 4 parts. Ammonium carbonate, 3 " Water 100 " Nickel sulphate, nitrate or chloride, 1 " Sodium bisulphate, 1 " Water, 20 " Nickel anodes are used in the bath to maintain the strength. Too muchcare cannot be exercised in the absolute cleanliness of the articles tobe plated. A too alkaline bath gives a disagreeable yellow color to thedeposit; too acid a bath gives badly adhering deposits. Night Bell. An alarm bell in a telegraph office, which bell is connected at night togive a loud signal to attract the operator's attention. It is used intelephone exchanges and is connected so as to ring as long as asubscriber remains unanswered after calling. Nobili's Rings. When a dilute solution of copper acetate is placed on a bright silverplate and a strip of zinc is touched to the silver beneath the copper, aseries of rings of copper are formed by electrolysis around the zinc. These are Nobili's rings. If for the copper acetate a solution of lead oxide in potassium hydratesolution is substituted, and if the polished plate which may be Germansilver is connected to the positive electrode of a battery, and aplatinum wire connected to the negative pole is immersed in the liquid, it determines the formation of beautiful iridescent rings of leadbinoxide. The platinum wire is sometimes sealed in glass so that onlyits point projects. The colors are due to interference of light, the layers of lead oxidebeing extremely thin. The lead binoxide is formed by secondary reaction. Metallic lead isfirst deposited on the negative pole. The oxygen which goes to thepositive pole formed by the polished plate produces lead binoxide whichis deposited there in rings. The reaction is comparable to that of astorage battery. Synonyms--Metallochromes--Electric Rings. Nodular Deposit. A deposit obtained in electroplating, characterized by irregularthickness; due to too low density of current. Non-conductor. A material that does not conduct electricity except with greatdifficulty; a substance of very high resistance. Synonym--Insulator--Dielectric. North Pole. (a) The north-seeking pole of a magnet; the pole of a magnet which tendsto point to the north, and whence lines of force are assumed to issue ontheir course to the other pole of the magnet. (b) The North Pole of the earth. Treating the earth as a magnet, andaccepting the above nomenclature the north pole should be termed thesouth pole. (See Austral Pole--Boreal Pole. ) 393 STANDARD ELECTRICAL DICTIONARY. North-seeking Pole. The pole of a magnet which tends to point to the north; the north poleof a magnet. Null Method. Any method of obtaining measurements or comparisons, in which themeasurement is correct when the deflection of the galvanometer or otherindicator is zero, nought or null. The Wheatstone Bridge (see Bridge, Wheatstone) is an example of a null method. Two obvious advantages attach to null methods in electric galvanometerwork. One is that an uncalibrated galvanometer can be employed. Theother is that a galvanometer of any high degree of sensitiveness can beemployed, there being no restriction as to its fineness of winding orhighness of resistance. "Upper case Omega Graphic". (Greek capital" Omega") symbol for megohm. [Transcriber's note: Now used for ohms. ] "Lower case Omega Graphic". (Greek omega) symbol for ohm. [Transcriber's note: Now used for angular velocity, 2*PI*frequency. ] Occlusion. An absorption of gases by metals. Palladium will, if used as thehydrogen evolving electrode in decomposing water, absorb 980 times itsvolume of hydrogen, which is said to be occluded. The metal may also beheated in hydrogen and allowed to cool therein, when occlusion occurs. Platinum will occlude 4 times its volume of hydrogen; iron, 4. 15 timesits volume of carbon-monoxide; silver, 7 times its volume of oxygen. Metals with occluded gases may serve as elements in a galvanic couple. (See Gas Battery. ) A metal expands in occluding a gas. In the storage battery it is believed that occlusion plays a part, hydrogen and oxygen being respectively absorbed by the two sets ofplates, and acting as they do in Groves' gas battery. Oerstedt. Name proposed for the unit of current strength, but not adopted. Theampere is the accepted name. 394 STANDARD ELECTRICAL DICTIONARY. Oerstedt's Discovery. Oerstedt discovered in 1820 that a magnetic needle tended to placeitself at right angles to a current of electricity. This fundamentalexperiment is the basis of the galvanometer. Fig. 251. OERSTEDT'S DISCOVERY. Ohm. The practical unit of resistance; 1E9 C. G. S. Electro-magnetic units. The legal ohm is the resistance of a mercury column 1 square millimeterin cross-sectional area and 106 centimeters in length. There has beenconsiderable confusion, owing to inaccuracy in early determinations, inthe valuation of the ohm. In this work the legal ohm is used. Thedifferent ohms will be found defined in their place. Resistance units ofvarious names may also be consulted. The following table gives the relative values of the different ohms. Length of Mercury Board of Column in True B. A. Trade Legal Centimetre. Ohm. Ohm. Ohm. Ohm. True Ohm, 106. 24 1. 1. 0128 . 9994 1. 0022B. A. Ohm, 104. 9 . 9874 1. . 9868 . 9889Board of Trade Ohm 106. 3 1. 00050 1. 0133 1. 1. 0028Legal Ohm, 106. 0 . 9977 1. 0112 . 9971 1. Ohmage. The Resistance of a circuit expressed in ohms. Ohm, B. A. The British Association unit of resistance; the resistance of a columnof mercury 1 square millimeter in cross sectional area and 104. 9centimeters long; the B. A. Unit of Resistance. Ohm, Board of Trade. The approximate ohm as recommended by the British Board of Trade on theadvice of a committee (Sir W. Thomson, Dr. J. Hopkinson, Lord Rayleighand others). It is the resistance of a mercury column one squaremillimeter in section, and 106. 3 centimeters long at 0º C. (32º F. ) Synonym--New Ohm. 395 STANDARD ELECTRICAL DICTIONARY. Ohmic Resistance. True resistance as distinguished from spurious resistance, orcounter-electro-motive force. Ohm, Legal. The practical unit of resistance. The resistance of a column of mercuryone square millimeter in cross-sectional area and 106 centimetres longat 0º C. (32º F. ) The ohm used previously to 1884 is the B. A. Unit ofResistance, q. V. One legal ohm = 1. 0112 B. A. Units, and I B. A. Unit = 0. 9889 legal ohm. The resistance of a copper wire 1 foot long and 1/1000 inch in diameteris about 10 ohms. The resistance of 1 mile of iron wire 1/3 inch indiameter is about 10 ohms. Synonym--Congress Ohm. 396 STANDARD ELECTRICAL DICTIONARY. Fig. 252. THEORY OF OHMMETER. Fig. 253. OHMMETER. Ohmmeter. An instrument for measuring directly the resistance of a conductor or ofany part of a circuit through which a strong current is passing. It isthe invention of Prof. W. E. Ayrton. It contains two fixed coils at right angles to each other acting on thesame needle of soft iron. One coil is of thick wire and is placed inseries with the resistance to be measured. The other is of very thinwire and is placed in parallel with the same resistance. One wire actsby the total current, the other by the potential difference between theends of the resistance. The action on the soft iron needle is due to theratio of potential difference to total currents, or to the resistanceitself. By properly designing and proportioning the coils the angulardeflections of the needle are made proportional to the resistance. In use the thick wire may be kept permanently in circuit. On connectingthe binding posts of the thin wire coil to any two parts of the circuitits resistance is at once given by the deflection of the needle. When no current is passing the needle rests in any position. A currentin the thick coil brings it to zero. A current simultaneously passingthrough the thin high resistance coil brings about the deflection. The instrument is a commercial rather than a scientific one. Ohm's Law. The fundamental law expressing the relations between current, electro-motive force and resistance in an active electric circuit. Itmay be expressed thus: (a) The current strength is equal to the electro-motive force divided bythe resistance. (b) The electro-motive force is equal to the current strength multipliedby the resistance. (c) The resistance is equal to the electro-motive force divided by thecurrent strength. All these are different forms of the same statement. Algebraically the law is usually expressed thus, (a) C = E/R. It mayalso be expressed thus: (b) E = C*R and (c) R= E/C, in which R denotesresistance, C denotes current strength, and E denotes electro-motiveforce. Ohm, True. The true ohm is the resistance of a column of mercury 1 squaremillimeter in cross-sectional area, and 106. 24 centimeters long. (SeeOhm. ) Synonym-Rayleigh Ohm. Oil Insulation. Oil insulation has received several applications in electrical work. Ithas been proposed for use in underground conduits. These it was proposedto fill with oil after the insertion of the conductors, the latterproperly wrapped with cotton or other covering. For induction coils ithas been very successfully used. Its principal utility depends on thefact that it is liquid, so that if pierced by a spark it at once closesagain. A solid insulator if pierced is permanently injured. It is alsoused in telegraph insulators (see Insulator, Liquid) to prevent surfaceleakage. 397 STANDARD ELECTRICAL DICTIONARY. Olefiant Gas. A compound gas; C2H4; composed of carbon, 24; hydrogen, 4; molecularweight, 28; specific gravity, . 981. It is a dielectric of about the resistance of air. Its specificinductive capacity at atmospheric pressure is 1. 000722 (Boltzman. ) Synonym--Ethene; heavy carburetted hydrogen. [Transcriber's note: Also called ethylene. A primary use is polyethyleneplastic. ] Open. Adj. An electric circuit is said to be open when it is cut or broken so thatno current can pass through it. The term may be recollected by thinkingof a switch; when open no current can pass through it. The sameadjective is applied to magnetic circuits, an air gap implying an opencircuit. Open Circuit Oscillation. An oscillation of current in open circuit so that a spark dischargeaccompanies it. It is produced by electric resonance in a simple circleor loop of wire with ends placed near together but not touching, if thecircuit is of such size that its period of oscillation corresponds withthat of the inducing discharge. (See Resonance, Electric. ) Its perioddepends entirely on the self-induction of the circuit. Ordinate. In a system of plane co-ordinates (see Co-ordinates), the distance ofany point from the axis of abscissas measured parallel to the axis ofordinates. Ordinates, Axis of. The vertical axis in a system of co-ordinates, q. V. Synonym--Axis of Y. Organ, Electric. An organ in which the air blast is admitted or excluded from thedifferent pipes by electric mechanism. The outlines of the system are a series of contacts worked by the keysand stops, which cause, when operated by the organist, a current to passthrough electro-magnets, opening the valves of the different pipes. Thusthe manual may be at any distance from the organ, and a number of organsmay be worked upon the same manual. As many as five in a singlecathedral are thus connected to a manual in the chancel. Orientation of a Magnetic Needle. The acquirement by a magnetic needle of its position of rest, with itsmagnetic axis in the magnetic meridian. Origin of Co-ordinates. In a system of linear co-ordinates the point of intersection of theaxes; the point whose co-ordinates are both zero. 398 STANDARD ELECTRICAL DICTIONARY. Oscillating Needle. A small light bar magnet suspended by a filament and employed indetermining the intensity of a magnetic field by the oscillations itcompletes in a given time after a given disturbance. Oscillations, Electric. In static electricity the sudden and very rapid alternations in thedischarge of a static condenser. This discharge of the disruptive orderseems a single one, but is really composed of a number of dischargesalternating in direction and producing electro-magnetic ether waves, probably identical with light waves except that they are longer and farless rapid. Oscillatory Electro-motive Force. Electro-motive force rapidly changing in sense or in direction, so thatit presents an oscillatory character. The alternating current and thetelephone current as used in practice are actuated by this type ofelectro-motive force. Osmose, Electric. When two liquids are separated by a porous diaphragm, and a strongcurrent of electricity is passed through from the liquid on one side, through the diaphragm, to the liquid on the other side, the liquid onthe side towards which the current is passing rises in level. Theprocess is termed electric osmose. When a liquid is forced through adiaphragm a current is produced; in other words electric osmose isreversible. The current thus produced is termed a diaphragm current. Oscillation, Electric. The phase of discharge of a static condenser in one direction. It isusually followed by a discharge in the opposite direction constituting asecond oscillation, and so on, so that a great number of exceedinglyshort oscillations are comprised. Thus, in the discharge of the Leydenjar a large number of oscillations of current back and forth areproduced, the current alternating like the swings of a pendulum. These oscillations are supposed to affect the ether, producing waves init identical with light waves, except that we have not been able yet toproduce them short enough to affect the visual organs. The waves thusproduced can be reflected or refracted; some substances are transparentfor them and others opaque. There is a possibility that man may yetsucceed in producing electric oscillations of sufficient frequency tobring about the direct production of light. Oscillatory Displacement. Hypothetical displacement currents of rapidly alternating directionproduced in the oscillatory discharge of a Leyden jar or staticcondenser. Oscillatory Induction. Induction produced by sympathetic action of an oscillatory discharge orby electric resonance. (See Oscillations, Electric--Resonance, Electric--Resonator, Electric. ) 399 STANDARD ELECTRICAL DICTIONARY. Outlet. The part of an electrolier or electric light fixture out of which thewires are led for attachment of an incandescent light socket. Output. The rate of energy delivered or of work done by a machine. In the caseof a current generator it is the volt-coulombs per given second, orbetter the volt-amperes delivered at its outer circuit terminals. Output, Magnetic. The analogue in a magnetic circuit of the output of an electric circuit. It is the product of the magnetizing force by the induced magnetism. Output, Unit of. As a unit of output of a dynamo Prof. Sylvanus P. Thompson has proposed1, 000 watts, or one kilowatt. This unit is now frequently used. Tocompletely define the dynamo, however, the amperage or the voltage mustalso be given, as a 10 kilowatt--110 volt machine, or a 10 kilowatt--99ampere machine. [Transcriber's note: 10 kilowatt at 110 volts is 91 amperes. ] Over-Compounding. A proportioning of the series and shunt windings of a compound dynamo, so that the voltage of the terminals rises with the load or outputenough to allow for the drop in mains, thus maintaining the potentialfor full load at distant points in a district. It is carried out by anincrease of ampere-turns in the series winding. Overload. In an electric motor a mechanical load put upon it so great as toprevent economical working. One effect of such a load is to make thearmature run so slowly as to unduly reduce the counter-electro-motiveforce and hence to permit so much current to pass through the coils asto heat them, perhaps injuriously. In this case the production of heatimplies the waste of energy. Overtype Dynamo or Motor. A dynamo or motor whose armature is placed above or in the upper part ofthe field magnets, the yoke piece of the magnets being in or restingupon the base of the machine. Ozone. An allotropic form of oxygen. It possesses much more energetic chemicalproperties than oxygen. It is supposed to contain three atoms of oxygenin its molecule, represented thus: O / \ O---O It is produced by electric discharges and it is its peculiar odor whichis noticed about an electric machine, and sometimes in a thunderstormnear the path of a lightning flash. In the electrolysis of water some ozone may be produced, thusdiminishing the volume of the oxygen or of the mixed gases given off. This is a source of inaccuracy in a gas voltameter. 400 STANDARD ELECTRICAL DICTIONARY. Pacinotti's Inductor. The Pacinotti or Gramme Ring. (See Pacinotti's Ring. ) Pacinotti's Ring. A ring of iron wire wound with coils of insulated wire at right anglesto its circular axis, and used as the armature of a dynamo or motor. Anumber of connections are taken from the coils to a central commutator. Fig. 254. PACINOTTI'S MACHINE, WITH RING ARMATURE. If such a ring with its coils is rotated in a field, current can betaken from points of the commutator on a line at right angles to thelines of force entering the ring. The ring was discovered in 1862 by Pacinotti, and later wasindependently discovered by Gramme. It is often known as the Grammering. Pacinotti Teeth. Projections on a cylindrical or drum armature, between which in thegrooves formed thereby, the wire is wound. The teeth being of iron tendto diminish the reluctance or magnetic resistance of the interpolarspace, or interval between the poles of the field magnet. Synonym--Pacinotti Projections. Paillard Alloys. Non-magnetic palladium alloys, invented by Paillard, ofSwitzerland, used in anti-magnetic watches. The following are given asthe compositions of several such alloys: I. II. Palladium, 60 to 75 parts 50 to 75 partsCopper, I5 to 25 " 20 to 30 "Iron. 1 to 5 " 5 to 20 " 401 STANDARD ELECTRICAL DICTIONARY. The following are more complex: I. II. Palladium, 65 to 75 parts 45 to 50 partsCopper, 15 to 25 " 15 to 25 "Nickel, 1 to 5 " 2 to 5 "Silver, 3 to 10 " 20 to 25 "Gold, 1 to 2-1/2 " 2 to 5 "Platinum, 1/2 to 2 " 2 to 5 "Steel, 1 to 5 " 2 to 5 " These alloys are used for balance springs, as well as for the balancewheels and escapement parts of watches. The elasticity of recentlyproduced springs has been found to be very satisfactory. Page Effect. The sounds produced by magnetizing and demagnetizing a bar of iron orsteel; the magnetic tick. The sounds are strong enough to produce atelephonic effect. (See Magnetic Tick. ) Palladium. A metal of the platinum series. It has the highest power of occlusion, q. V. , of all metals. It is the characteristic ingredient of non-magneticwatch alloys. Palladium used as an electrode in the electrolysis of water will occlude936 volumes of hydrogen, and the hydrogen-palladium alloy will exceed insize the original electrode. Fig. 255. LUMINOUS PANE. Pane, Luminous. A pane of glass, one side of which has pasted to it a long zigzag stripof tinfoil. A design is made by cutting through the strip. Ondischarging a Leyden jar or an electric machine through the strip sparksappear where the tinfoil is severed, thus producing the design in aluminous effect. Many variations can be employed in their construction. 402 STANDARD ELECTRICAL DICTIONARY. Pantelegraphy. A system of telegraphy for transmitting designs, maps, drawing, and thelike by telegraphy. (See Telegraphy, Facsimile. ) Paper Filaments. Filaments of carbon for incandescent lamps made from paper. This is one of the earliest materials practically used. The paper is cutout of proper shape, and is carbonized in a close vessel, while embeddedin powdered charcoal or some other form of carbon to absolutely cut offaccess of air. It is then placed in the lamp chamber and flashed orsubjected to the regular treatment. Parabola. A curve; one of the conic sections. It is approximately represented by asmall arc of a circle, but if extended becomes rapidly deeper than ahalf circle. If, from a point within called the focus, lines are drawn to the curveand then other lines are drawn from these points parallel to the axis, the angles of incidence will he equal to the angles of reflection asreferred to tangents at the points where the lines touch the curve. [Transcriber's note; The general equation of a parabola is A*x^2 + B*x*y + C*y^2 + D*x + E*y + F = 0such that B^2 = 4*A*C, all of the coefficients are real, and A and C arenot zero. A parabola positioned at the origin and symmetrical on the yaxis is simplified to y = a*x^2 ] Parabolic Reflector. A reflector for a light, a paraboloid or surface of revolution whosesection is a parabola. A light placed at its focus has its raysreflected parallel to each other. Examples of parabolic reflectors are seen in electric search lights andin locomotive head-lights. They are employed in electric search lights. The arc light must be of such construction as to maintain its ignitedpoints always at the same point, the focus of the paraboloid. Paraffine. V. To coat or saturate with paraffine wax. Paper may be paraffined bydipping in the wax, or by being sprinkled with fragments of wax, subsequently melted in with a hot iron or otherwise. The tops of batterycarbons are often paraffined to prevent the acid from rising in thepores by capillary attraction and rusting the connections. 403 STANDARD ELECTRICAL DICTIONARY. Paraffine Wax. A hydro-carbon composed principally of mixtures of the higher members ofthe paraffine series C n H2 n + 2. It is made from cannel coal, coaltar, or petroleum by distillation. It is an insulator. Its resistance at46° C. (114. 8° F. ) per centimeter cube is 3. 4E16 ohms, or about thehighest resistance known. Its specific inductive capacity (for milky wax) is 2. 47 (Schiller). Forclear wax it is given as follows by different authorities: 1. 92 Ayrton. 1. 96 Wüllner. 1. 977 Gibson & Barclay. 2. 32 Baltzmann. It is extensively used in condensers and other electric apparatus as adielectric and insulator. Paragrêles. Protectors against hail; lightning rods used to guard fields againsthail; of little or no real utility. Parallax. The apparent change in position of an object when looked at from twopoints of view. By looking at an object a few feet distant first withone eye and then with the other, the shifting in apparent position isseen. In reading the position of an indicator or needle over a scale parallaxintroduces an error unless the eye is held vertically over the needle. By making the dial of looking- glass and holding the eye so that thereflection of its pupil is bisected by the needle this verticality isensured. Parallel. (a) In the nomenclature of electric circuits two or more conductorsleading from one point to another, are said to be in parallel. (b) When two or more conductors connect two main leads of comparativelylarge size and low resistance they are said to be in parallel or inmultiple arc. This order is easiest pictured as the rungs of a ladder inparallel connecting its two sides representing the main leads. It may be used as a noun as "arranged in parallel, " or as an adjectiveas "a parallel circuit, " the opposite of series, q. V. Paramagnetic. Adj. Possessing paramagnetic properties; tending to occupy a position withthe longer axis parallel to the lines of force of a magnetic field;having magnetism; attracted by a magnet. "If a homogeneous isotropic substance is placed in a magnetic field itbecomes magnetized at every point in the direction of the magneticintensity at that point, and with an intensity of magnetizationproportional to the magnetic intensity. When the positive direction ofthe induced magnetization is the same as that of the magnetic intensitythe substance is called Magnetic or Paramagnetic; when it is opposite, the substance is called Diamagnetic. " (Emtage. ) A paramagnetic substance has high permeability or multiplying power forlines of force, hence in a magnetic field a bar of iron, etc. , is inunstable equilibrium unless its longer axis is parallel with the linesof force in order to reduce as much as possible the reluctance of thecircuit. 404 STANDARD ELECTRICAL DICTIONARY. Iron is the most paramagnetic of all substances. Other paramagneticmetals are: Nickel, cobalt, manganese, platinum, cerium, osmium, palladium. Diamagnetic metals are bismuth, antimony, zinc, tin, mercury, lead, silver, copper, gold, arsenic. Bismuth is the most diamagnetic ofall metals. Of gases oxygen is most paramagnetic. Becquerel calculated that a cubicyard of oxygen condensed would act on a magnetic needle as powerfully as5. 5 grains of metallic iron. Liquefied oxygen will adhere to the polesof a magnet. Changes of temperature and of other conditions may affect a body'smagnetism. Thus hot oxygen is diamagnetic, and a substance paramagneticin a vacuum may be diamagnetic in air. Of liquids, solutions of iron or cobalt are paramagnetic; water, blood, milk, alcohol, ether, oil of turpentine and most saline solutions arediamagnetic. Paramagnetism. (a) The science or study of paramagnetic substances and phenomena. (b) The magnetic property of a paramagnetic substance; that of beingattracted by a magnet, and of arranging itself with its longer axisparallel with the lines of force of a magnetic field. Parchmentizing. If cellulose is treated with a mixture of two parts of sulphuric acidand one part of water perfectly cold, it becomes like parchment. Itshould at once be washed with water, and then with ammonia and water. The Swan incandescent light fibres are made of parchmentized cottonthread, which is afterward carbonized. Partial Earth. A fault in a conductor caused by imperfect connection with the earth, where insulation from the earth is desired. Passive State. A state of a substance in virtue of which it is unattacked by a solventwhich ordinarily would dissolve or attack it. Iron in strong nitric acidis unattacked or assumes the passive state. This particular case issupposed to be due to a coating of magnetic oxide, so that there wouldbe properly speaking no question of a passive state, but only one ofsuperficial protection. The existence of a true passive state of any substance is very doubtful. P. D. Abbreviation for potential difference or difference of potential, or forelectro-motive force. 405 STANDARD ELECTRICAL DICTIONARY. Peltier Effect. The thermal effect produced by the passage of a current through thejunction of two unlike conductors. Such junction is generally the seatof thermo-electric effects, and a current is generally produced byheating such a junction. If an independent current is passed in the samedirection as that of the thermoelectric current, it cools the junction, and warms it if passed in the other direction. In general terms, referring to thermo-electric couples, if passed through them it tends tocool the hot and heat the cool junction. The phenomenon does not occurin zinc-copper junctions. Peltier's Cross. A bar of bismuth and a bar of antimony soldered centre to centre atright angles, being notched or halved there to receive or to set intoeach other. It is used to demonstrate the Peltier effect, q. V. To onepair of ends are connected the terminals of a battery circuit; to theother pair are connected the terminals of a galvanometer. The galvanometer by its deflections in one and then in the otherdirection indicates that the junction is heated when the current passesfrom antimony to bismuth and vice versa. It thus illustrates the heatingand cooling of a thermo-electric junction by a current of electricity. The current from the battery by the Peltier effect either heats or coolsthe junction, as the case may be. This heating or cooling them producesa thermo-electric current in the galvanometer circuit. The battery hasno direct influence on the galvanometer. Pendant Cord. A double conductor or pair of conductors, insulated from each other andcovered with a worsted, silk, or cotton covering and used to suspendincandescent lamps and at the same time to conduct the current to them. It is also used for other similar service, such as acting as conductorsfor small motors. Often each conductor is composed of a number of thinwires laid together. This gives flexibility to the cord. Synonym--Flexible Cord. Pendulum, Electric. (a) A pendulum operated by the intermittent action of an electro-magnet, whose circuit is opened and closed by the pendulum itself. A point atthe lower end of the pendulum swinging through a globule of mercury mayclose and open the circuit. Various other methods of accomplishing thesame end are employed .. (b) A pith ball suspended by a thread from an insulating stand. It isused to show the attraction exercised by a piece of sealing wax or othersubstance excited by rubbing. 406 STANDARD ELECTRICAL DICTIONARY. Pen, Electric. A stylus for producing a series of perforations in paper, so that thepaper may act as a stencil for the reproduction of a great number ofcopies of the original matter. Various kinds of electric pens have beeninvented. One kind, invented by Edison, consists of a handle carrying anelectric motor actuating a needle, which is driven in and out of theother end of the handle with high rapidity. It is used by being heldvertically on the paper with the needle end downward, and is moved so asto describe perforated letters or designs. The paper is then used as astencil with an ink roller to reproduce the writing or design adlibitum. A simpler kind dispenses with the motor and depends on theperforations produced by the electric spark. As shown in the cut thestylus is one terminal of an induction coil circuit. The support onwhich the paper rests is the other terminal and must be a conductor. Inuse the induction coil is started, and the stylus is moved over thepaper; a series of sparks pass through the paper from stylus to thesupporting tablet, perforating the paper and producing a stencil to beused for reproduction. Fig. 256. ELECTRIC PEN. Pentane Standard, Harcourt's. A standard of illuminating power; in it the combustible substance is agas made by mixing one cubic foot of air with three cubic inches ofliquid pentane, measured at 60° F. Or, if measured as gases, 20 volumesof air to 7 of pentane. It is burned at the rate of 0. 5 cubic foot perhour from a cylindrical tube one inch in diameter, closed at the top bya disc 0. 5 inch thick with a hole 0. 25 inch in diameter, through whichthe gas issues. It gives a flame 2. 5 inches high. The pentane used is the distillate of petroleum which boils at 50° C. (122° F. ) ; it has a specific gravity at 15° C. (60° F. ) of from 0. 628to 0. 631. It is almost pure pentane (C5H12). As long as the rate of consumption is between 0. 48 and 0. 52 cubic footper hour the flame gives practically the same light. 407 STANDARD ELECTRICAL DICTIONARY. Perforator. An apparatus used in automatic high speed telegraphy for perforatingstrips of paper. These are then used by drawing between a roller andcontact spring for making and breaking the telegraphic circuit for theproduction of a record, such as the Morse record, at the distantreceiving station. The perforated strip has different classes of holes punched in it torepresent dots or dashes. It is fed by machinery very rapidly, so thatthe message is transmitted with the highest speed. Several operators maysimultaneously prepare the paper strips, and thus in conjunction withits rapid feeding in the transmitter, far surpass the time of ordinarydirect transmission. Fig. 257. PERFORATOR FOR WHEATSTONE'S AUTOMATIC TELEGRAPH. Perforators may be entirely mechanical but are sometimes pneumatic, compressed air being used to operate them. The holes they make are ondifferent levels of the paper strip, as shown in the cut. Period. The time required for the completion of one complete element of periodicmotion. This may be a complete alternation (See Alternation, Complete)of an alternating current, or of an oscillatory discharge. Periodicity. The rate of succession of alternations or of other fixed phases; therate of recurrence of phenomena. 408 STANDARD ELECTRICAL DICTIONARY. Permanency. In electric current conductors the property of possessing conductivityunaffected by lapse of time. Generally the permanency of conductors isvery high. In some cases a slow annealing takes place which causes agradual change with the lapse of time. Annealed German silver wire hasbeen found to increase in conductivity at about . 02 per cent. In a year. (Matthiessen. ) Wire, whether annealed or not, is left in a strainedcondition after the drawing operations, and such a change is consonantwith this fact. The figure only applies to the samples tested byMatthiessen. Permanent State. In a telegraph line or other current conductor, the condition when auniform current strength obtains over the whole line. When a current isstarted it advances through the line with a sort of wave front graduallyincreasing in strength. At the further end some time may elapse beforeit attains its full intensity. When its does the permanent stateprevails. Until then the variable state, q. V. , exists in the line. Permeameter. An apparatus for determining the permeability of samples of iron. Itconsists of a large slotted block of iron. A coil is placed within theslot. A hole is drilled through one end, and a rod of the iron to betested is passed through this hole and through the coil to the bottom ofthe slot. The lower end of the rod must be accurately faced off. Thecurrent is turned on, upon which the rod adheres to the bottom of theslot. The force required to detach it is determined with a springbalance. The permeation through its face is proportional to the squareof the force required. Fig. 258. PERMEAMETER. Permeance. The multiplying or the conducting power for magnetic lines of forcepossessed by a given mass of material. It varies with the shape and sizeof the substance as well as with the inducing force. It is distinguishedfrom permeability, as the latter is a specific quality proper to thematerial, and expressed as such; the permeance is the permeability asaffected by size and shape of the object as well as by its material. 409 STANDARD ELECTRICAL DICTIONARY. Pflüger's Law. A law of electro-therapeutics. It states that stimulation of a nerve isonly produced by successive appearance of the kathelectrotonic state, and disappearance of the anelectrotonic state. Phantom Wires. The extra transmission circuits obtained in multiplex telegraph systems. A single line arranged for four separate simultaneous transmissions byquadruplex apparatus is said to establish three phantom wires. Phase. In wave motion, oscillating motion, simple harmonic motion, or similarperiodic phenomena, the interval of time passed from the time the movingparticle moved through the middle point of its course to the instantwhen the phase is to be stated. Pherope. An apparatus for the electric transmission of pictures. (See Telephote. ) [Transcriber's note: Precursor of the contemporary Fax and scanner. ] Philosopher's Egg. An ellipsoidal vessel mounted with its long axis vertical and with twovertical electrodes, the upper one sliding, and arranged to be attachedto an air pump. A discharge through it when the air is exhausted takesthe general shape of an egg. Phonautograph. An apparatus for registering the vibrations of a stylus, which ismounted on a diaphragm and is acted on by sound waves. It is virtually a resonating chamber, over one of whose ends a parchmentdiaphragm is stretched. To the centre of the parchment a needle orstylus is attached. A cylinder covered with soot is rotated in contactwith the point of the stylus. As the chamber is spoken into thediaphragm and stylus vibrate and the vibrations are marked on thecylinder. It is of some electric interest in connection with telephony. Phone. Colloquial abbreviation for telephone. Phonic Wheel. A form of small motor of very simple construction. It consists of atoothed wheel of soft iron. A bar electro-magnet is fixed with one polefacing the teeth of the wheel. By a tuning fork make and break asuccession of impulses of rapid frequency and short duration are sentthrough the magnet. The teeth act as armatures and are successivelyattracted by the magnet. The regulated speed is one tooth for eachimpulse, but it may rotate at one-half the speed, giving two teeth foreach impulse, or at certain other sub-multiples of its regular speed. Itis the invention of Paul Lecour. 410 STANDARD ELECTRICAL DICTIONARY. Phonograph. An apparatus for reproducing articulate speech. It is not electric, except as it may be driven by electricity. It consists of a cylinder of wax-like material which is rotated andmoved slowly, longitudinally, screw fashion, at an even speed. A glassdiaphragm carrying a needle point is supported with the point barelytouching the wax. If the diaphragm is agitated, as by being spokenagainst, the needle is driven back and forwards cutting a broken line orgroove following the direction of the thread of a screw in the wax, thedepth of which line or groove continually varies. This imprints the message. If the needle is set back and the cylinder isrotated so as to carry the needle point over the line thus impressed, the varying depth throws the needle and diaphragm into motion and thesound is reproduced. The cylinder is rotated often by an electric motor, with a centrifugalgovernor. [Transcriber's note; Due to T. A. Edison, 1877, fifteen years beforethis book. ] Phonozenograph. An apparatus for indicating the direction of the point where a sound isproduced. It operates by a microphone and telephone in conjunction witha Wheatstone bridge to determine the locality. Phosphorescence. The emission of light rays by a substance not heated, but whoseluminosity is due to the persistence of luminous vibration after lighthas fallen upon it. A phosphorescent body, after exposure to light, is luminous itself. Phosphorescence may be induced by rubbing or friction, by heat, bymolecular bombardment, as in Crookes' tubes, and by static discharge ofelectricity, as well as by simple exposure to light. Another form of phosphorescence may be due to slow chemical combustion. This is the cause of the luminosity of phosphorous. Phosphorous, Electrical Reduction of. Phosphorous is reduced from bone phosphate by the heat of the electricarc. The phosphate mixed with charcoal is exposed to the heat of thevoltaic are, and reduction of the phosphorous with its volatilization atonce ensues. The phosphorous as it volatilizes is condensed andcollected. Photo-electricity. The development of electrical properties by exposure to light. Crystalsof fluor spar are electrified not only by heat (see Pyro-electricity)but also by exposure to sunlight or to the light of the voltaic arc. [Transcribers note: Although first observed in 1839 by Becquerel, itwas not explained until 1905 by Albert Einstein with the introduction ofphotons. ] Photo-electric Microscope. A projection, solar or magic-lantern microscope worked by the electriclight. Photo-electro-motive Force. Electro-motive force produced in a substance by the action of light. 411 STANDARD ELECTRICAL DICTIONARY. Photometer. An apparatus for measuring the intensity of light emitted by a givenlamp or other source of illuminating power. They may be classified intoseveral types. Calorimetric or Heat Photometers act by measuring relatively the heatproduced by the ether waves (so-called radiant heat) emitted by thesource. The accuracy of the instrument is increased by passing the raysthrough an alum solution. A thermopile, or an air thermometer, may beused to receive the rays. Chemical Photometers. In these the light falls upon sensitizedphotographic paper. The depth of coloration is used as the index ofilluminating power. Direct Visual Photometers. These include Rumford's Shadow Photometer, Bunsen's Bar Photometer, and Wheatstone's Bead Photometer, in which thelight is estimated by direct visual comparison of its effects. Optical Photometers. These include Polarization Photometers, in whichthe light is polarized; Dispersion Photometers, in which a diverginglens is placed in the path of the rays of light so as to reduce theilluminating power in more rapid ratio than that of the square of thedistance. Selenium Photometers, in which the variations in resistance of seleniumas light of varying intensity falls upon it is used as the indicator ofthe intensity of the light. Jet Photometers, for gas only, in which the height of a flame undergiven conditions, or the conditions requisite to maintain a flame ofgiven height, is used to indicate the illuminating power. The subject of photometers has acquired more importance than ever inview of the extensive introduction of the electric light. (See Candle, Standard--Carcel--Violé's Standard--and Photometers of various kinds. ) Photometer, Actinic. A photometer whose registrations are produced by the action of the lightbeing tested upon sensitized paper or plates, such as used inphotography. Some efforts at self-registering photometers have beenbased on actinic registration of the height of a flame of the gas to betested. Photometer, Bar. A photometer in which the two lights to be compared are fixed at oropposite to the ends of a bar or scale of known length, generally 60 or100 inches. The bar is divided by the rule of the inverse square of thedistances, so that if a screen is placed on any part of the bar where itreceives an equal amount of light from both sources, the figure on thebar will indicate the relative illuminating power of the larger lamp orlight in terms of the smaller. The divisions of the bar are laid out onthe principle that the illuminating power of the two sources of lightwill vary inversely with the square of their distance from the screen. 412 STANDARD ELECTRICAL DICTIONARY. The screen used is sometimes the Bunsen disc. This is a disc of paperwith a spot of paraffine wax in the centre melted thoroughly into thepaper or with a ring of paraffine wax surrounding the untouched centre. When this disc is equally illuminated on both sides the spot is nearlyinvisible. Inequality of illumination brings it out more visibly. Sometimes a Leeson disc is used. This consists of three pieces of paper, two thin ones between which a thicker piece, out of which a star is cut, is laid. When equally illuminated on both sides the star appears equallybright on both sides. The bar photometer is the standard form. A candle or pair of candles maybe burned at one end and an incandescent lamp at the other, or a gasflame may first be rated by candles and used as a standard. Synonyms--Bunsen's Photometer--Translucent Disc Photometer. Fig. 259. BAR PHOTOMETER. Photometer. Calorimetric. A photometer in which the radiant energy, so called radiant heat, isused as the measurer of the light. In one type a differential air thermometer is used, one of whose bulbsis blackened. On exposing this bulb to a source of light it will becomeheated, and if lights of the same character are used the heating will bein proportion to their illuminating power quite closely. The heating isshown by the movements of the index. By careful calibration theinstrument may be made quite reliable. Photometer, Dispersion. A photometer in which the rays from one of the lights under comparisonare made more divergent by a concave lens. In this way a strong light, such as all arc lamp can be photometered more readily than where onlythe natural divergence of the beam exists. The law of the variation ofthe intensity of light with the square of the distance is abrogated fora law of more rapid variation by the use of a concave lens. The diagram, Fig. 260, illustrates the principle. E represents apowerful light, an arc light, to be tested. Its distance from the screenis e. Its light goes through the concave lens L and is dispersed asshown over an area A1, instead of the much smaller area A, which thesame rays would otherwise cover. Calling l the distance of the lens fromthe screen, f its focus, and c the distance of the standard candle fromthe screen when the shadows are of equal intensity, we have theproportion. Illuminating power of lamps: ditto of standard candle:: (l (e-l) + fe)2 : (c f)2 413 STANDARD ELECTRICAL DICTIONARY. Fig. 260. DIAGRAM OF PRINCIPLE OF THE DISPERSION PHOTOMETER. The cut, Fig. 261, gives a perspective view of Ayrton's DispersionPhotometer. C is the standard candle, L the concave lens, R the rod forproducing the two shadows on the screen S. Fig. 261. AYRTON'S DISPERSION PHOTOMETER. The mirror M is fixed at an angle of 45° with the stem on which itrotates. The light of the arc lamp is received by the mirror and isreflected through the lens. The candle holder slides along a graduatedbar C, and at D is an index plate to show the angle at which the spindlecarrying the mirror is set. 414 STANDARD ELECTRICAL DICTIONARY. Dr. J. Hopkinson in his dispersion photometer uses a double convex lens. This gives a focal image of the arc-lamp between the lens and screen, whence the rays diverge very rapidly, thus giving the desired dispersioneffect. It is principally for arc lamps that dispersion photometers are used. Photometer, Shadow. A photometer in which the relative intensity of the two lights isestimated by the intensity or strength of shadows of the same objectwhich they respectively cast. Fig. 262. RUMFORD'S SHADOW PHOTOMETER. Fig. 263. RUMFORD'S SHADOW PHOTOMETER ARRANGED FOR TESTINGINCANDESCENT LAMPS. 415 STANDARD ELECTRICAL DICTIONARY. A rod is supported in a vertical position. Back of it is a screen ofwhite paper. The two lights to be compared are arranged in front of therod and at a little distance from each other. They are shifted aboutuntil the two shadows appear of equal darkness. The relative intensityof the lights varies inversely with the square of their distances fromthe shadows cast respectively by them on the screen. The cut, Fig. 262, shows the simplest type of the shadow photometer. Inthe cut, Fig. 263, a shadow photometer for testing incandescent lamps isshown. In it E is the lamp under trial supported by a clamp H. A is anampere meter in circuit with the lamp, and V is a voltmeter. A candle Ccan be moved along a graduated scale G G. R is the vertical rod, and Sis the screen on which the shadows fall. Photophore. An instrument for medical examination of the cavities of the body. Itincludes an incandescent lamp mounted in a tube with a concave mirrorand convex lens. Photo-voltaic Effect. The change in resistance of some substances effected by light. Selenium, of all substances, is most susceptible to this effect. (See Selenium. ) Piano, Electric. A piano whose manual or key-board operates to close electric circuits, whereby electro-magnets are caused to operate to drive the hammersagainst the strings. Pickle. An acid solution for cleaning metal surfaces before electro-plating, galvanizing or other deposition of metal upon them. Picture, Electric. A picture produced by passing a strong discharge through a piece of goldleaf clamped or firmly pressed upon a sheet of paper. The gold leaf iscut out of the desired shape, or else a stencil of paper overlays it. The discharge dissipates the gold, and produces a purple coloredreproduction of the design upon the paper. The design is due to thedeposition of an exceedingly thin film of metallic gold. Synonym--Electric Portrait. Pile. A galvanic or voltaic battery. It is sometimes restricted to a number ofvoltaic couples connected. It should be only applied to batteries withsuperimposed plates and no containing vessel such as the Dry Pile, q. V. , or Volta's Pile, q. V. Pilot Transformer. In alternating current distribution a small transformer placed at anypart of the system and connected to a voltmeter in the central station, to indicate the potential difference of the leads. Pilot Wires. Wires brought from distant parts of electric light or power mains, andleading to voltmeters at the central station, so that the potential ofdistant parts of the system can be watched. The wires can be very small, as they have but little current to transmit. 416 STANDARD ELECTRICAL DICTIONARY. Pistol, Electric. An experimental apparatus for exhibiting the power of electricincandescence or of the electric spark. A tube is mounted with a handlelike a pistol. A plug is provided to screw in and out of its side. Theplug carries two wires connected on its inner side by a fine platinumwire, or else disconnected but with their ends brought near together toact as terminals for the production of a spark. To use it the tube isfilled with a mixture of air and gas, the latter either hydrogen, hydro-carbon or other combustible gas. The tube when full is corked. Thewire is heated to incandescence by a current, or a spark is passed froma Leyden jar or other source of electrostatic excitation. The mixture, if properly proportioned, explodes and expels the cork violently. Fig. 264. ELECTRIC PISTOL. Pith. A light and soft cellular tissue forming the central core of exogenoustrees and plants. In the older parts of the tree the woody tissue oftenencroaches in and partly obliterates it. For electrical pith-balls, the pith of the elder, of corn, or, best ofall, of sun-flower stems is used. Pith-balls. Ball made of pith. They are used in the construction of electroscopesand for other experiments in static electricity. They are cut out with a sharp knife and their shape may be improved bygentle rolling in the hand or between the fingers. Pivot Suspension. Suspension poising or supporting of an object on a sharp pivot. This isused for the needle in the ordinary compass. A cavity or inverted cup, which may be made of agate, is attached to the middle of the needlewhich has a hole for its reception. The centre of gravity of the needlecomes below the bottom of the cup. Pivot suspension is not perfect, as it has considerable friction. Thereis no restitution force, as with torsion filaments. 417 STANDARD ELECTRICAL DICTIONARY. Plant. The apparatus for commercial manufacturing or technical works. Anelectric lighting plant includes the boilers, engines and dynamos forproducing the current, and the electric mains and subsidiary apparatus. Plant Electricity. Electricity manifested by plant life. By means of a galvanometerpotential differences are found to exist in different parts of trees orfruits. The roots and interior portions are negative, and the flowers, smaller branches and fruit are positive. In some cases a contraction of the tissue of plants can be produced byan electric current. The sensitive plant and others exhibit thisphenomenon, exactly analogous to the action of muscular tissue. Plate, Arrester. In a lightning arrester the plate connected to the circuit. Sometimesboth plates are designated arrester plates. Plate Condenser. A static condenser having a flat plate of glass for dielectric. (SeeEpinus' Condenser. ) Plate Electrical Machine. A frictional electric machine, in which a circular plate of glass isexcited by friction with the cushions. It is the most recent type offrictional machine and has superseded the old cylinder machines. In itsturn it is superseded by influence machines, really plate machines, butnot so termed in practice. Plate, Ground. In a lightning arrester, the plate connected to the earth. Plate, Negative. In a voltaic battery, either primary or secondary, the plate which isunattacked by the oxygen or negative radical or element of the fluid. Itcorresponds to the carbon plate in the ordinary voltaic battery, and isthe one charged with positive electricity. Plate, Positive. In a voltaic battery, either primary or secondary, the plate which isdissolved or attacked by the oxygen or negative radical or element ofthe fluid. It is the plate corresponding to the zinc plate in theordinary voltaic battery, and is the one charged with negativeelectricity. Plating Balance. A balance or scales to which articles in an electroplater's bath aresuspended. A weight exceeding by a known amount that of the article asimmersed overbalances the article. When the plating is being depositedas soon as it exceeds the excess of weight of the counterpoise thebalance tips, the article descends a little, the electric circuit isbroken and the plating ceases. Thus the plating is automatically stoppedwhen a predetermined amount of metal is deposited. 418 STANDARD ELECTRICAL DICTIONARY. Plating Bath. A vessel of solution for the deposition of metal by electrolysis as usedin electro-plating. Plating, Electro-. The deposition of metal by electrolysis so as to coat the conductingsurface of objects therewith. The full details of the many processes arevery lengthy and cannot be given here. The general principle includes a battery or source of electric current. The object to be plated is connected to the negative terminal and isimmersed in the solution. Thus with a battery the object is inelectrical connection with the zinc plate. To the other terminal ametallic plate is connected. The object and the plate termed the anodebeing introduced into a suitable bath, the metal whose solution is inthe bath is deposited upon the surface of the object. The bath is a solution of the metal in some form that will lend itselfto the electrolytic action. The anode is often a plate of the metal ofthe bath, so that it dissolves as fast as metal is deposited on theobject, thus keeping up the strength of the solution. The objects to be plated must be scrupulously clean, and great care mustbe taken to keep the bath uncontaminated. When the object has a non-conducting surface, it is made conducting bybeing brushed over with plumbago q. V. In addition iron dust is sometimesdusted over it. This acts by precipitating the metal of the bathdirectly and thus giving a conducting basis for the metal to deposit on. To avoid getting iron in a bath the object may be dipped in coppersulphate solution. This precipitates copper in place of the iron andleaves the article in good shape for silver or other plating. Electro-plating, if made thick enough, gives a reverse of the articlewhen separated therefrom. A direct copy can be got by a second plating, on the first plating after separation, or a wax impression can beemployed. Under the different metals, formulae for the baths will be found. (Seealso Quicking--Steeling--Plating Balance. ) Platinoid. An alloy of copper, nickel, zinc in the proportions of German silverwith 1 or 2 per cent of tungsten. It is used for resistances. It has aspecific resistance (or resistance per centimeter cube) of about 34microhms. Its percentage variation in resistance per degree C. (1. 8° F. )is only about . 021 per cent. , or less than half that of German silver. This is its most valuable feature. 419 STANDARD ELECTRICAL DICTIONARY. Platinum. A metal; one of the elements; symbol, Pt; atomic weight, 197. 4;equivalent, 49. 35; valency, 4; specific gravity, 21. 5. It is a conductor of electricity. The following data refer to the annealed metal at 0° C. (32° F. ) Relative Resistance (Silver annealed = 1), 6. 022 Specific Resistance, 9. 057 microhms. Resistance of a wire, (a) 1 foot long, weighing 1 grain, 2. 779 ohms. (b) 1 foot long, 1/1000 inch thick, 54. 49 " (c) 1 meter long, weighing 1 gram, 1. 938 " (d) 1 meter long, 1 millimeter thick, . 1153 "Resistance of a 1 inch cube, 3. 565Electro-chemical equivalent (Hydrogen = . 0105), 0. 5181. The coefficient of expansion by heat is almost the same as that ofglass. It can be passed through holes in glass and the latter can bemelted about it so as to hermetically seal its place of passage throughthe glass. It is used in incandescent lamps for leading-in wires andother similar uses. Platinum Black. Finely divided platinum. It is made by boiling a solution of platinicchloride with excess of sodium carbonate and a quantity of sugar, untilthe precipitate is perfectly black and the supernatant liquid iscolorless. It seems to possess a great power of occluding oxygen gas. When heated to redness it becomes spongy platinum. The negative platesof a Smee battery are coated with platinum black. Platinum-silver Alloy. An alloy of 1 part platinum and 2 parts silver, used for resistance coils. Relative Resistance (silver annealed = 1 ), 16. 21 microhms. Specific Resistance at 0°C. (32° F. ), 24. 39 Resistance of a wire, (a) 1 foot long, weighing 1 grain, 4. 197 ohms. (b) 1 foot long, 1/1000 inch diameter, 146. 70 " (c) 1 meter long weighing 1 gram, 2. 924 " (d) 1 meter long, 1 millimeter diameter, 0. 3106 " Resistance of a 1 inch cube, 9. 603 microhms. Percentage Variation per degree C. (1. 8° F. ) at about 20° C. (68° F. ), 0. 031 per cent. Synonym--Platinum Alloy. Platinum Sponge. Finely divided platinum obtained by igniting platinum black, q. V. , andalso by igniting salts of platinum. It has considerable power ofcondensing or occluding oxygen. It will, if in good condition, set fireto a jet of hydrogen impinging upon it. Plow. Contact arms projecting downwards from the motors, trucks, or bodies ofelectric street cars, which enter the underground conduit through theslot and carry contact pieces or brushes, to take the current fordriving the motors from the leads within the conduit. 420 STANDARD ELECTRICAL DICTIONARY. Plücker Tubes. A special form of Geissler tube designed for the production ofstratification and for observing the effects produced in the spacesurrounding the negative electrode. Plug. (a) A piece of metal with a handle and a somewhat tapered end, used tomake connections by insertions between two plates or blocks of metalslightly separated and with grooves to receive it. (b) A plug or wedge with two metallic faces, insulated from each otherwith a separate wire connected to each one. It is used in spring-jacksq. V. , to introduce a loop in a circuit. Synonym--Wedge. Plug. V. To connect by inserting a plug, as in a resistance box. Fig. 265. PLUGS FOR RESISTANCE COIL BOX. Fig. 266. PLUG SWITCH. Plug, Double. A spring-jack plug or wedge with two pairs of insulated faces, onebehind the other, so as to simultaneously introduce two loops into acircuit. Plug, Grid. A piece or mass of lead oxide, inserted into the holes in the leadplates of storage batteries. The holes are often dovetailed or of unevensection to better retain the plugs. Plug Infinity. In a box-bridge or resistance box, a plug whose removal from between twodisconnected discs opens the circuit. All the other discs are connectedby resistance coils of various resistance. Plug Switch. A switch composed of two contact blocks, not touching each other andbrought into electrical connection by the insertion of a metallic plug. The latter is usually provided with an insulating handle, and a seat isreamed out for it in the two faces of the contact blocks. 421 STANDARD ELECTRICAL DICTIONARY. Plumbago. Soft lustrous graphite, a native form of carbon; sometimes chemicallypurified. It is used in electro-plating to give a conducting surface tonon-conducting objects, such as wax moulds. The surface, after coatingwith plumbago, is sometimes dusted over with iron dust, whichprecipitates the metal of the bath and starts the plating. It issometimes plated with copper, silver or gold, and is then termedcoppered, silvered, or gilt plumbago. It is gilded by moistening withetherial solution of gold chloride and exposing to the air, and dryingand igniting. Plunger. A movable core which is used in connection with a so-called solenoidcoil, to be drawn in when the coil is excited. (See Coil and Plunger. ) Fig. 267 COIL AND PLUNGER WITH SCALES TO SHOW ATTRACTION. P. O. Abbreviation for Post Office, q. V. Poggendorf's Solution. An acid depolarizing and exciting fluid for zinc-carbon batteries. Thefollowing is its formula: Water, 100 parts; potassium bichromate, 12parts; concentrated sulphuric acid, 25 parts. All parts by weight. Usecold. Point, Neutral. (a) On a commutator of a dynamo the points at the ends of the diameterof commutation, or where the brushes rest upon the surface of thecommutator, are termed neutral points. At these points there is nogeneration of potential, they marking the union of currents of oppositedirection flowing from the two sides of the armature into the brushes. (b) In electro-therapeutics, a place in the intra-polar region of anerve so situated with reference to the kathode and electrode as appliedin treatment, that its condition is unaffected. Synonym--Indifferent Point. (c) In a magnet the point of no attraction, situated between the twopoles, at about an equal distance from each, so as to mark the centre ofa magnet of even distribution of polarity. (d) In thermo-electricity the point of temperature where thethermo-electric powers of two metals are zero; in a diagram the pointwhere the lines representing their thermo-electric relations cross eachother; if the metals are arranged in a thermo-electric couple, one endat a temperature a given amount above, the other at a temperature thesame amount below the neutral point, no current or potential differencewill be produced. 422 STANDARD ELECTRICAL DICTIONARY. Point, Null. A nodal point in electrical resonators; a point where in a system ofwaves or oscillations, there is rest, the zero of motion being theresultant of oppositely directed and equal forces. In electricalresonators it is to be sought for in a point symmetrically situated, with reference to the spark gap, or in a pair of points, which pair issymmetrically placed. The null point in resonators is found by connecting a lead from one ofthe secondary terminals of an induction coil to different parts of theresonator. The null point is one where the connection does not give riseto any sparks between the micrometer knobs or spark gap, or where thesparks are of diminished size. The whole is exactly comparable to loops and nodes in a vibrating stringor in a Chladni plate as described in treatises on sound and acoustics. (See Resonance, Electrical--Resonator, Electrical. ) Synonym--Nodal Point. Point Poles. Magnet poles that are virtually points, or of no magnitude. A long thinmagnet with little leakage except close to the ends may be supposed tohave point poles within itself a short distance back from the ends. Points, Consequent. In a magnet with consequent poles, the points where such poles aresituated. Points, Corresponding. In bound electrostatic charges the points of equal charges of oppositepotentials; the points at opposite extremities of electrostatic lines offorce. This definition implies that the bound charges shall be on equalfacing areas of conductors, as otherwise the spread or concentration ofthe lines of force would necessitate the use of areas of sizeproportionate to the spreading or concentrating of the lines of force. At the same time it may figuratively be applied to these cases, thepenetration of the surface by a single line of force including the areafixed by its relation to the surrounding lines. Points, Isoelectric. In electro-therapeutics, points of equal potential in a circuit. 423 STANDARD ELECTRICAL DICTIONARY. Points of Derivation. The point where a single conductor branches into two or more conductors, operating or acting in parallel with each other. Polar Angle. The angle subtended by one of the faces of the pole pieces of the field-magnet of a dynamo or motor. The centre of the circle of the angle liesin the axis of the armature. Synonym--Angle of Polar Span. Polar Extension. An addition made of iron to the poles of magnets. Various forms havebeen experimented with. The pole pieces of dynamo field magnets arepolar extensions. Synonyms--Pole Piece--Polar Tips. Polarity, Diamagnetic. The induced polarity of diamagnetic substances; it is the reverse ofparamagnetic polarity, or of the polarity of iron. A bar of diamagneticmaterial held parallel with the lines of force in a magnetic field has alike pole induced in the end nearest a given pole of the field magnet, and vice versa. This theory accounts for the repulsion by a magnet of adiamagnetic substance. The existence of this polarity is rather anassumption. It originated with Faraday. Polarity, Paramagnetic. The induced polarity of paramagnetic substances, such as iron, nickel, or cobalt. When such a substance is brought into a magnetic field the part nearesta specific pole of a magnet acquires polarity opposite to that of suchpole and is thereby attracted. Another way of expressing it, in which the existence of a pole in ornear to the field is not implied, is founded on the conventionaldirection of lines of force. Where these enter the substance a southpole is formed and where they emerge a north pole is formed. Such polarity tends always to be established in the direction ofgreatest length, if the body is free to rotate. 424 STANDARD ELECTRICAL DICTIONARY. Polarization. (a) The depriving of a voltaic cell of its proper electro-motive force. Polarization may be due to various causes. The solution may becomeexhausted, as in a Smee battery, when the acid is saturated with zincand thus a species of polarization follows. But the best definition ofpolarization restricts it to the development of counter-electro-motiveforce in the battery by the accumulation of hydrogen on the negative(carbon or copper) plate. To overcome this difficulty many methods areemployed. Oxidizing solutions or solids are used, such as solution ofchromic acid or powdered manganese dioxide, as in the Bunsen andLeclanché batteries respectively; a roughened surface of platinum blackis used, as in the Smee battery; air is blown through the solution tocarry off the hydrogen, or the plates themselves are moved about in thesolution. (b) Imparting magnetization to a bar of iron or steel, thus making apermanent magnet, is the polarization of the steel of which it is made. Polarization may be permanent, as in steel, or only temporary, as insoft iron. (c) The strain upon a dielectric when it separates two oppositelycharged surfaces. The secondary discharge of a Leyden jar, and itsalteration in volume testify to the strain put upon it by charging. (d) The alteration of arrangement of the molecules of an electrolyte bya decomposing current. All the molecules are supposed to be arrangedwith like ends pointing in the same direction, positive ends facing thepositively-charged plate and negative ends the negatively-charged one. (e) The production of counter-electro-motive force in a secondarybattery, or in any combination capable of acting as the seat of suchcounter-electro-motive force. (See Battery, Secondary--Battery, Gas. )The same can be found often in organized cellular tissue such as that ofmuscles, nerves, or of plants. If a current is passed through this inone direction, it often establishes a polarization or potentialdifference that is susceptible of giving a return current in theopposite direction when the charging battery is replaced by a conductor. Polarization Capacity. A voltaic cell in use becomes polarized by its negative plateaccumulating hydrogen, or other cause. This gradually gives the plate apositive value, or goes to set up a counter-electro-motive force. Thequantity of electricity required to produce the polarization of abattery is termed its Polarization Capacity or Capacity of Polarization. Polarization of the Medium. The dielectric polarization, q. V. , of a dielectric, implying thearrangement of its molecules in chains or filaments; a term due toFaraday. He illustrated it by placing filaments of silk in spirits ofturpentine, and introduced into the liquid two conductors. Onelectrifying one and grounding (or connecting to earth) the other one, the silk filaments arranged themselves in a chain or string connectingthe points of the conductors. Polar Region. That part of the surface of a magnet whence the internal magnetic linesemerge into the air. (S. P. Thompson. ) As such lines may emerge fromvirtually all parts of its surface, the polar regions are indefiniteareas, and are properly restricted to the parts whence the lines emergein greatest quantity. Polar Span. A proportion of the circle which represents the transverse section ofthe armature space between the pole pieces of the field magnet in adynamo or motor; it is the proportion which is filled by the faces ofthe pole pieces. 425 STANDARD ELECTRICAL DICTIONARY. Pole, Analogous. The end of a crystal of a pyroelectric substance, such as tourmaline, which end when heated become positively electrified. On reduction oftemperature the reverse effect obtains. Pole, Antilogous. The end of a crystal of a pyroelectric substance, such as tourmaline, which end, while increasing in temperature, becomes negativelyelectrified. During reduction of its temperature the reverse effectobtains. Pole Changer. (a) An automatic oscillating or vibrating switch or contact-breakerwhich in each movement reverses the direction of a current from abattery or other source of current of fixed direction, as such currentgoes through a conductor. (b) A switch moved by hand which for each movement effects the aboveresult. Pole, Negative. (a) In a magnet the south pole; the pole into which the lines of forceare assumed to enter from the air or outer circuit. (b) In a current generator the pole or terminal into which the currentis assumed to flow from the external circuit. It is the negativelycharged terminal and in the ordinary voltaic battery is the terminalconnected to the zinc or positive plate. Pole Pieces. The terminations of the cores of field or other electro-magnets, or ofpermanent magnets. These terminations are variously shaped, sometimesbeing quite large compared to the core proper of the magnet. They are calculated so as to produce a proper distribution of anddirection of the lines of force from pole to pole. As a general rule theactive field should be of uniform strength and the pole pieces may be ofcontour calculated to attain this end. Pole, Positive. (a) In a magnet the north pole; the pole from which lines of force areassumed to emerge into the air. (b) In a current generator the pole or terminal whence the current isassumed to issue into the outer circuit. It is the positively chargedterminal, and in the ordinary voltaic battery is the terminal connectedto the copper or carbon plate, termed the negative plate. Poles. (a) The terminals of an open electric circuit, at which therenecessarily exists a potential difference, produced by the generator orsource of electro-motive force in the circuit. (b) The terminals of an open magnetic circuit; the ends of a magnetizedmass of steel, iron or other paramagnetic substance. (c) The ends in general of any body or mass which show electric ormagnetic properties more developed than those of the central sections ofthe body. 426 STANDARD ELECTRICAL DICTIONARY. Pole, Salient. In dynamo and motor field magnets, salient poles are those projectingfrom the base or main body of the field magnet, as distinguished fromconsequent poles formed by coils wound on the main body itself. Fig. 268. SALIENT POLES OF FIELD MAGNET. Poles, Compensating. A device for avoiding the cross-magnetizing effect on the commutatorcore due to the lead of the brushes. It consists in maintaining a smallbar electro-magnet perpendicularly between the pole pieces. Thiscompensates the cross-magnetizing effect. Poles of Intensity. The locus of highest magnetic force on the earth's surface. One suchpole is in Siberia, another is about lat. 52° N. , long. 92° W. [Transcriber's note: 52° N. , long. 92° W is about 250 miles Northeast ofWinnipeg. ] Poles of Verticity. The magnetic poles of the earth. (See Magnetic Poles. ) Pole Tips. The extreme ends of the expanded poles of a field magnet. In somemachines some of the pole tips are made of cast iron, to alter thedistribution of the lines of force and resulting magnetic pull upon thearmatures. This is done to take off the weight of the armature from itsbearings. Pole, Traveling. A term applied to the poles produced in the action of a rotatory field, whose poles constantly rotate around the circle of the field. (SeeField, Rotatory. ) 417 STANDARD ELECTRICAL DICTIONARY. Porous Cup. A cup of pipe clay, unglazed earthenware or other equivalent materialused in voltaic cells to keep two liquids separate and yet to permitelectrolysis and electrolytic conduction. They are necessarily only an expedient, as their porous nature permitsconsiderable diffusion, and were they not porous electrolytic actionwould be impossible. Synonym--Porous Cell. Porret's Phenomenon. In electro-physiology, an increase in the diameter of a nerve producedby the positive pole of a voltaic circuit, when placed in contact withthe tissue and near to the nerve in question, the other pole beingconnected to a more or less remote part of the body. Portelectric Railroad. A railroad worked by solenoidal attraction, the car forming the core ofthe solenoids. It includes a series of solenoids or hollow coils ofcopper wire distributed all along the road and inclosing withinthemselves the track. On this a cylindrical car with pointed ends moveson wheels. Current is supplied to the solenoid in advance of the car, and attracts it. As it advances it breaks the contacts of the attractingsolenoid and turns the current into the one next in advance. Thisoperation is repeated as the car advances. The solenoids are placed close together, each including in the trialtrack 630 turns of No. 14 copper wire. The car was of wrought iron, 12feet long, 10 inches in diameter and weighing 500 lbs. It was proposedto employ the system for transportation of mail matter and similar uses. Position Finder. An instrument for determining the position of objects which are to befired at from forts. It is designed for use from forts situated on thewater. Fiske's position finder may be thus generally described. On a chart thechannel is divided into squares, and the position finder determines thesquare in which a vessel lies. For each square the direction andelevation of the guns is calculated beforehand. The enemy can thereforebe continuously located and fired at, although from smoke or other causethe object may be quite invisible to the gunner. It comprises two telescopes situated at distant extremities of as long abase line as is obtainable. These telescopes are kept directed upon theobject by two observers simultaneously. The observers are in constanttelephonic communication. As each telescope moves, it carries a contactover an arc of conducting material. Below each telescope is an arm alsomoving over an arc of conducting material. These arcs enter into aWheatstone bridge and are so connected that when the arm and the distanttelescope are at the same angle or parallel a balance is obtained. Thuseach observer has the power of establishing a balance. A chart isprovided for each of them, and over it the arm connected with thedistant telescope and an arm or indicator attached to the telescope atthat station move so that as long as both telescopes point at the objectand each observer maintains the electric balance, the intersection ofthe arms shows the position on the chart. The Position Finder is a simplification and amplification of the RangeFinder, q. V. In practice the observers may be placed far from theforts, and may telephone their observations thereto. It has been foundaccurate within one-third of one per cent. 428 STANDARD ELECTRICAL DICTIONARY. Positive Direction. The direction which lines of force are assumed to take in the air orouter circuit from a positive to a negative region. It applies toelectrostatic, to magnetic and to electro-magnetic lines of force. Positive Electricity. The kind of electricity with which a piece of glass is charged whenrubbed with silk; vitreous electricity. In a galvanic cell the surface of the copper or carbon plate is chargedwith positive electricity. (See Electrostatic Series. ) According to the single fluid theory positive electrification consistsin a surplus of electricity. [Transcriber's note: "Positive electricity" is a deficiency of electrons. ] Post Office. Adj. Many pieces of electric apparatus of English manufacture are thusqualified, indicating that they are of the pattern of the apparatus usedby the British Post Office in its telegraph department. Potential. Potential in general may be treated as an attribute of a point in space, and may express the potential energy which a unit mass would have ifplaced at that point. This conception of potential is that of a property attributable to apoint in space, such that if a unit mass were placed there the forcesacting upon it would supply the force factor of energy, while the bodywould supply the mass factor. This property is expressible in units, which produce, if the supposed mass is a unit mass, units of work orenergy, but potential itself is neither. Thus taking gravitation, a pound mass on the surface of the earth(assuming it to be a sphere of 4, 000 miles radius) would require theexpenditure of 21, 120, 000 foot pounds to remove it to an infinitedistance against gravity. The potential of a point in space upon thesurface of the earth is therefore negative and is represented by-21, 120, 000*32. 2 foot poundals (32. 2 = acceleration of gravity). (SeePoundal. ) In practice and conventionally all points on the earth'ssurface are taken as of zero potential. [Transcriber's note; 21, 120, 000 foot pounds is about 8 KWh. ] 429 STANDARD ELECTRICAL DICTIONARY. Potential, Absolute. The absolute electrical potential at a point possesses a numerical valueand measures the tendency which the existing electric forces would haveto drive an electrified particle away from or prevent its approach tothe point, if such a particle, one unit in quantity, were brought up toor were situated at that point. It is numerically equal to the number ofergs of work which must be done to bring a positive unit of electricityfrom a region where there is absolutely no electric force up to thepoint in question. (Daniell. ) Two suppositions are included in this. Theregion where there is an electric force has to be and only can be at aninfinite distance from all electrified bodies. The moving of theparticle must take place without any effect upon the distribution ofelectricity on other particles. Potential, Constant. Unchanging potential or potential difference. The ordinary system of incandescent lighting is a constant potentialsystem, an unvarying potential difference being maintained between thetwo leads, and the current varying according to requirements. Potential Difference, Electric. If of any two points the absolute potentials are determined, thedifference between such two expresses the potential difference. Numerically it expresses the quantity of work which must be done toremove a unit of electricity from one to the other against electricrepulsion, or the energy which would be accumulated in moving it theother way. A positively charged particle is driven towards the point of lowerpotential. A negatively charged body is driven in the reverse direction. Potential Difference, Electro-motive. A difference of potential in a circuit, or in part of a circuit, whichdifference produces or is capable of producing a current, or is due tothe flow of such current. It may be expressed as the fall in potential or the electro-motive forceincluded between any two points on a circuit. The current in an activecircuit is due to the total electro-motive force in the circuit. This isdistributed through the circuit in proportion to the resistance of itsparts. Owing to the distribution of electro-motive force throughout acircuit including the generator, the terminals of a generator on closedcircuit may show a difference of potential far lower than theelectro-motive force of the generator on closed circuit. Hence potentialdifference in such a case has been termed available electro-motiveforce. Potential, Electric Absolute. The mathematical expression of a property of a point in space, measuringthe tendency which existing electric forces would have to drive anelectrified unit particle away from or prevent its approach to the pointin question, according to whether the point was situated at or was at adistance from the point in question. Potential is not the power of doing work, although, as it is expressedalways with reference to a unit body, it is numerically equal to thenumber of ergs of work which must be done in order to bring a positiveunit of electricity from a region where there is no electricforce--which is a region at an infinite distance from all electrifiedbodies--up to the point in question. This includes the assumption thatthere is no alteration in the general distribution of electricity onneighboring bodies. (Daniell. ) In practice the earth is arbitrarily taken as of zero electric potential. 430 STANDARD ELECTRICAL DICTIONARY. Potential, Fall of. The change in potential between any two points on an active circuit. Thechange in potential due to the maintenance of a current through aconductor. The fall in potential multiplied by the current gives work or energyunits. The fall of potential in a circuit and its subsequent raising by theaction of the generator is illustrated by the diagram of a helix. In itthe potential fall in the outer circuit is shown by the descent of thehelix. This represents at once the outer circuit and the fall ofpotential in it. The vertical axis represents the portion of the circuitwithin the battery or generator in which the potential by the action ofthe generator is again raised to its original height. In a circuit of even resistance the potential falls evenly throughoutit. A mechanical illustration of the relation of fall of potential tocurrent is shown in the cut Fig. 269. A vertical wire is supposed to befixed at its upper end and a lever arm and cord at its lower end, withweight and pulley imparts a torsional strain to it. The dials andindexes show a uniform twisting corresponding to fall of potential. Foreach unit of length there is a definite loss of twisting, correspondingto fall of potential in a unit of length of a conductor of uniformresistance. The total twisting represents the total potentialdifference. The weight sustained by the twisting represents the currentmaintained by the potential difference. For a shorter wire less twistingwould be needed to sustain the weight, as in a shorter piece of theconductor less potential difference would be needed to maintain the samecurrent. Fig. 269. MECHANICAL ILLUSTRATION OF FALL OF POTENTIAL AND CURRENTSTRENGTH. 431 STANDARD ELECTRICAL DICTIONARY. Fig. 270. ILLUSTRATION OF THE FALL AND REDEVELOPMENT OF POTENTIAL IN ANELECTRIC CIRCUIT. The fall of potential in a circuit in portions of it is proportional tothe resistance of the portions in question. This is shown in thediagram. The narrow lines indicate high and the broad lines lowresistance. The fall in different portions is shown as proportional tothe resistance of each portion. Fig. 271. DIAGRAM OF FALL OF POTENTIAL IN A CONDUCTOR OF UNEVENRESISTANCE. Potential, Magnetic. The magnetic potential at any point of a magnetic field expresses thework which would be done by the magnetic forces of the field on apositive unit of magnetism as it moves from that point to an infinitedistance therefrom. The converse applies to a negative unit. It is the exact analogue of absolute electric potential. The potential at any point due to a positive pole m at a distance r ism/r;. That due to a negative pole - m at a distance r' is equal to-m/r';. That due to both is equal to m/r - m/r' or m(1/r - 1/r'). Like electric potential and potential in general, magnetic potentialwhile numerically expressing work or energy is neither, although oftendefined as such. 432 STANDARD ELECTRICAL DICTIONARY. Potential, Negative. The reverse of positive potential. (See Potential, Positive. ) Potential, Positive. In general the higher potential. Taking the assumed direction of linesof force, they are assumed to be directed or to move from regions ofpositive to regions of negative potential. The copper or carbon plate ofa voltaic battery is at positive potential compared to the zinc plate. Potential, Unit of Electric. The arbitrary or conventional potential--or briefly, the potential of apoint in an electric field of force--is, numerically, the number of ergsof work necessary to bring a unit of electricity up to the point inquestion from a region of nominal zero potential--i. E. , from thesurface of the earth. (Daniell. ) This would give the erg as the unit ofpotential. Potential, Zero. The potential of the earth is arbitrarily taken as the zero of electricpotential. The theoretical zero is the potential of a point infinitely distant fromall electrified bodies. Fig. 272. DIAGRAM OF POTENTIOMETER CONNECTIONS. Potentiometer. An arrangement somewhat similar to the Wheatstone Bridge for determiningpotential difference, or the electro-motive force of a battery. Ingeneral principle connection is made so that the cell under trial wouldsend a current in one direction through the galvanometer. Anotherbattery is connected, and in shunt with its circuit the battery undertrial and its galvanometer are connected, but so that its current is inopposition. By a graduated wire, like that of a meter bridge, thepotential of the main battery shunt can be varied until no currentpasses. This gives the outline of the method only. 433 STANDARD ELECTRICAL DICTIONARY. In the cut A B is the graduated potentiometer wire through which acurrent is passed in the direction of the arrow. E is the battery undertrial, placed in opposition to the other current, with a galvanometernext it. Under the conditions shown, if the galvanometer showed nodeflection, the E. M. F. Of the battery would be to the E. M. F. Betweenthe ends of the potentiometer wire, 1 . . . . . 10, as 1. 5 the distancebetween the points of connection, A and D of the battery circuit, is to10, the full length of the potentiometer wire. Poundal. The British unit of force; the force which acting on a mass of one poundfor one second produces an acceleration of one foot. [Transcriber's note: The force which acting on a mass of one poundproduces an acceleration of ONE FOOT PER SECOND PER SECOND. ] Power. Activity;the rate of activity, of doing work, or of expending energy. Thepractical unit of electric power is the volt-ampere or watt, equal to1E7 ergs per second. The kilowatt, one thousand watts or volt-amperes, is a frequently adopted unit. Power, Electric. As energy is the capacity for doing work, electric energy is representedby electricity in motion against a resistance. This possesses a speciesof inertia, which gives it a species of kinetic energy. To produce suchmotion, electro- motive force is required. The product of E. M. F. Byquantity is therefore electric energy. (See Energy, Electric. ) Generally the rate of energy or power is used. Its dimensions are ( ( (M^. 5)*(L^. 5) ) / T ) * ( ( (M^. 5) *(L^1. 5) )/( T^2) ) (intensity or current rate) * (electro-motive force or potential) = (M * (L^2) ) / (T^3), which are the dimensions of rate of work or activity. The practical unitof electric rate of energy or activity is the volt-ampere or watt. ByOhm's law, q. V. , we have C = E/R (C = current; E = potential differenceor electro-motive force; R = resistance. ) The watt by definition = C*E. By substitution from Ohm's formula we deduce for it the followingvalues: ((C^2) * R) and ((E^2) /R). From these three expressions therelations of electric energy to E. M. F. , Resistance, and Current can bededuced. Power of Periodic Current. The rate of energy in a circuit carrying a periodic current. In such acircuit the electro-motive force travels in advance of the current itproduces on the circuit. Consequently at phases or intervals where, owing to the alternations of the current, the current is at zero, theelectro-motive force may be quite high. At any time the energy rate isthe product of the electro-motive force by the amperage. To obtain thepower or average rate of energy, the product of the maximumelectro-motive force and maximum current must be divided by two andmultiplied by the cosine of the angle of lag, which is the angleexpressing the difference of phase. [Transcriber's note; The voltage phase will lead if the load isinductive. The current phase will lead if the load is capacitive. Capacitors or inductors may be introduced into power lines to correctthe phase offset introduced by customer loads. ] 434 STANDARD ELECTRICAL DICTIONARY. Pressel. A press-button often contained in a pear-shaped handle, arranged forattachment to the end of a flexible conductor, so as to hang thereby. Bypressing the button a bell may be rung, or a distant lamp may belighted. Pressure. Force or stress exerted directly against any surface. Its dimensions areforce/area or ((M*L)/(T^2)) / (L^2) = M/(L* (T^2)). Pressure, Electric. Electro-motive force or potential difference; voltage. An expression ofmetaphorical nature, as the term is not accurate. Pressure, Electrification by. A crystal of Iceland spar (calcium carbonate) pressed between thefingers becomes positively electrified and remains so for some time. Other minerals act in a similar way. Dissimilar substances pressedtogether and suddenly separated carry off opposite charges. This isreally contact action, not pressure action. Primary. A term used to designate the inducing coil in an induction coil ortransformer; it is probably an abbreviation for primary coil. Primary Battery. A voltaic cell or battery generating electric energy by directconsumption of material, and not regenerated by an electrolytic process. The ordinary voltaic cell or galvanic battery is a primary battery. Prime. Vb. To impart the first charge to one of the armatures of a Holtz or otherinfluence machine. Fig. 273. PRIME CONDUCTOR AND PROOF PLANE. 435 STANDARD ELECTRICAL DICTIONARY. Prime Conductor. A metal or metal coated sphere or cylinder or other solid with roundedends mounted on insulating supports and used to collect electricity asgenerated by a frictional electric machine. According to whether the prime conductor or the cushions are groundedpositive or negative electricity is taken from the ungrounded part. Generally the cushions are grounded, and the prime conductor yieldspositive electricity. Probe, Electric. A surgeon's probe, designed to indicate by the closing of an electriccircuit the presence of a bullet or metallic body in the body of apatient. Two insulated wires are carried to the end where their ends are exposed, still insulated from each other. In probing a wound for a bullet if thetwo ends touch it the circuit is closed and a bell rings. If a bone istouched no such effect is produced. The wires are in circuit with anelectric bell and battery. Projecting Power of a Magnet. The power of projecting its lines of force straight out from the poles. This is really a matter of magnetic power, rather than of shape of themagnet. In electromagnets the custom was followed by making them long toget this effect. Such length was really useful in the regard of gettingroom for a sufficient number of ampere turns. 436 STANDARD ELECTRICAL DICTIONARY. Fig. 274. PRONY BRAKE. Prony Brake. A device for measuring the power applied to a rotating shaft. Itconsists of a clamping device to be applied more or less rigidly to theshaft or to a pulley upon it. To the clamp is attached a lever carryinga weight. The cut shows a simple arrangement, the shaft A carries apulley B to which the clamp B1 B2 is applied. The nuts C1 C2 are usedfor adjustment. A weight is placed in the pan E attached to the end of the lever D. Theweight and clamp are so adjusted that the lever shall stand horizontallyas shown by the index E. If we call r the radius of the pulley and F thefriction between its surface and the clamp, it is evident that r F, themoment of resistance to the motion of the pulley, is equal to the weightmultiplied by its lever arm or to W*R, where W indicates the weight andR the distance of its point of application from the centre of the pulleyor r*F = R*W. The work represented by this friction is equal to thedistance traveled by the surface of the wheel multiplied by thefrictional resistance, or is 2*PI*r*n*F, in which n is the number ofturns per minute. But this is equal to 2*PI*R*W. These data being known, the power is directly calculated therefrom in terms of weight and feetper minute. Proof-plane. A small conductor, usually disc shaped, carried at the end of aninsulating handle. It is used to collect electricity by contact, fromobjects electrostatically charged. The charge it has received is thenmeasured (see Torsion Balance) or otherwise tested. (See PrimeConductor. ) Proof-sphere. A small sphere, coated with gold-leaf or other conductor, and mounted onan insulated handle. It is used instead of a proof-plane, for testingbodies whose curvature is small. Fig. 275. BOX BRIDGE. 437 STANDARD ELECTRICAL DICTIONARY. Proportionate Arms. In general terms the arms of a Wheatstone bridgewhose proportion has to be known to complete the measurement. There is adifferent system of naming them. Some designate by this title the twoarms in parallel with each other branching at and running from one endof the bridge to the two galvanometer connections. In the cut of the BoxBridge, A C and A B are the proportionate arms. The third arm is thentermed the Rheostat arm. (Stewart & Gee. ) Others treat as proportionate arms the two side members of the bridge inparallel with the unknown resistance and third or rheostat arm. Synonym--Ratio Arms. Prostration, Electric. Too great exposure to the voltaic arc in its more powerful forms causessymptoms resembling those of sunstroke. The skin is sometimes affectedto such a degree as to come off after a few days. The throat, foreheadand face suffer pains and the eyes are irritated. These effects onlyfollow exposure to very intense sources of light, or for very longtimes. [Transcriber's note: Arcs emit ultraviolet rays. ] Protector, Comb. A lightning arrester, q. V. , comprising two toothed plates nearlytouching each other. Protector, Electric. A protective device for guarding the human body against destructive orinjurious electric shocks. In one system, Delany's, the wrists andankles are encircled by conducting bands which by wires running alongthe arms, back and legs are connected. A discharge it is assumedreceived by the hands will thus be short circuited around the body andits vital organs. India rubber gloves and shoe soles have also beensuggested; the gloves are still used to some extent. Pull. A switch for closing a circuit when pulled. It is used instead of a pushbutton, q. V. , in exposed situations, as its contacts are betterprotected than those of the ordinary push button. Pump, Geissler. A form of mercurial air pump. It is used for exhausting Geissler tubes, incandescent lamp bulbs and similar purposes. Referring to the cut, A is a reservoir of mercury with flexible tube Cconnected to a tube at its bottom, and raised and lowered by a windlassb, the cord from which passes over a pulley a. When raised the mercurytends to enter the chamber B, through the tube T. An arrangement ofstopcocks surmounts this chamber, which arrangement is shown on a largerscale in the three figures X, Y and Z. To fill the bulb B, the cocks areset in the position Z; n is a two way cock and while it permits theescape of air below, it cuts off the tube, rising vertically from it. This tube, d in the full figure connects with a vessel o, pressure gaugep, and tube c, the latter connecting with the object to be exhausted. The bulb B being filled, the cock m is closed, giving the position Y andthe vessel A is lowered until it is over 30 inches below B. 438 STANDARD ELECTRICAL DICTIONARY. This establishes a Torricellian vacuum in B. The cock n is now turned, giving the position X, when air is at once exhausted from the vesselconnected to C. This process is repeated until full exhaustion isobtained. In practice the first exhaustion is often effected by amechanical pump. By closing the cock on the outlet tube c but little airneed ever find its way to the chambers o and B. Fig. 276. GEISSLER AIR PUMP. 439 STANDARD ELECTRICAL DICTIONARY. Pumping. In incandescent lamps a periodical recurring change in intensity due tobad running of the dynamos, or in arc lamps to bad feeding of thecarbons. Fig. 277. SPRENGEL AIR PUMP. Pump, Sprengel. A form of mercurial air pump. A simple form is shown in the cut. Mercuryis caused to flow from the funnel A, through c d to a vessel B. A sideconnection x leads to the vessel R to be exhausted. As the mercurypasses x it breaks into short columns, and carries air down betweenthem, in this way exhausting the vessel R. In practice it is morecomplicated. It is said to give a better vacuum than the Sprengel pump, but to be slower in action. 440 STANDARD ELECTRICAL DICTIONARY. Pump, Swinburne. A form of mechanical air pump for exhausting incandescent lamp bulbs. Referring to the cut, A is a bulb on the upper part of a tube G; above Aare two other bulbs C and D. From the upper end a tube runs to the bulbE. Through the cock L, and tube F connection is made with a mechanicalair pump. The tube H leads to a drying chamber I, and by the tube Jconnects with the lamp bulbs or other objects to be exhausted. The tubeG enters the bottle B through an airtight stopper, through which asecond tube with stopcock K passes. In use a vacuum is produced by themechanical pumps, exhausting the lamp bulbs to a half inch and drawingup the mercury in G. The bent neck in the bulb E, acts with the bulb asa trap to exclude mercury from F. When the mechanical pumps haveproduced a vacuum equal to one half inch of mercury, the cock L isclosed and K is opened, and air at high pressure enters. This forces themercury up to the vessel D, half filling it. The high pressure is nowremoved and the mercury descends. The valve in D closes it as themercury falls to the level G. Further air from the lamps enters A, andby repetition of the ascent of the mercury, is expelled, through D. Themercury is again lowered, producing a further exhaustion, and theprocess is repeated as often as necessary. Fig. 278. SWINBURNE'S AIR PUMP. Push-Button. A switch for closing a circuit by means of pressure applied to a button. The button is provided with a spring, so that when pushed in andreleased it springs back. Thus the circuit is closed only as long as thebutton is pressed. The electric connection may be made by pressingtogether two flat springs, each connected to one of the wires, or by thestem of the button going between two springs, not in contact, forcingthem a little apart to secure good contact, and thereby bridging overthe space between them. 441 STANDARD ELECTRICAL DICTIONARY. Pyro-electricity. A phenomenon by which certain minerals when warmed acquire electricalproperties. (Ganot. ) The mineral tourmaline exhibits it strongly. It wasoriginally observed in this mineral which was found to first attract andthen to repel hot ashes. The phenomenon lasts while any change of temperature within certainlimits is taking place. In the case of tourmaline the range is fromabout 10º C. (50º F. ) to 150º C. (302º F. ) Above or below this range itshows no electrification. The effect of a changing of temperature is to develop poles, onepositive and the other negative. As the temperature rises one end ispositive and the other negative; as the temperature becomes constant thepolarity disappears; as the temperature falls the poles are reversed. If a piece of tourmaline excited by pyro-electricity is broken, itsbroken ends develop new poles exactly like a magnet when broken. The following minerals are pyro-electric: Boracite, topaz, prehnite, zinc silicate, scolezite, axenite. The following compound substances arealso so: Cane sugar, sodium- ammonium racemate and potassium tartrate. The list might be greatly extended. The phenomenon can be illustrated by sifting through a cotton sieve uponthe excited crystal, a mixture of red lead and flowers of sulphur. Bythe friction of the sifting these become oppositely electrified; thesulphur adheres to the positively electrified end, and the red lead tothe negatively electrified end. (See Analogous Pole-Antilogous Pole. ) Pyromagnetic Motor. A motor driven by the alternation of attraction and release of anarmature or other moving part, as such part or a section of it isrendered more or less paramagnetic by heat. Thus imagine a cylinder of nickel at the end of a suspension rod, somounted that it can swing like a pendulum. A magnet pole is placed toone side to which it is attracted. A flame is placed so as to heat itwhen in contact with the magnet pole. This destroys its paramagnetismand it swings away from the magnet and out of the flame. It cools, becomes paramagnetic, and as it swings back is reattracted, to be againreleased as it gets hot enough. This constitutes a simple motor. A rotary motor may be made on the same lines. Nickel is particularlyavailable as losing its paramagnetic property easily. 442 STANDARD ELECTRICAL DICTIONARY. Various motors have been constructed on this principle, but none haveattained any practical importance. Owing to the low temperature at whichit loses its paramagnetic properties nickel is the best metal forparamagnetic motors. In Edison's motor, between the pole pieces of an electro-magnet acylinder made up of a bundle of nickel tubes is mounted, so as to befree to rotate. A screen is placed so as to close or obstruct the tubesfarthest from the poles. On passing hot air or products of combustion ofa fire or gas flame through the tubes, the unscreened ones are heatedmost and lose their paramagnetism. The screened tubes are then attractedand the armature rotates, bringing other tubes under the screen, whichis stationary. Then the attracted tubes are heated while the otherscool, and a continuous rotation is the result. Fig. 279. EDISON'S PYROMAGNETIC MOTOR. Pyromagnetic Generator. A current generator producing electric energy directly from thermalenergy by pyromagnetism. Edison's pyromagnetic generator has eight electro-magnets, lying oneight radii of a circle, their poles facing inward and their yokesvertical. Only two are shown in the cut. On a horizontal iron disc aremounted eight vertical rolls of corrugated nickel representingarmatures. On each armature a coil of wire, insulated from the nickel byasbestus is wound. The coils are all in series, and have eightconnections with a commutator as in a drum armature. There are two maindivisions to the commutator. Each connects with an insulated collectingring, and the commutator and collecting rings are mounted on a spindlerotated by power. Below the circle of vertical coils is a horizontalscreen, mounted on the spindle and rotating with it. A source of heat, or a coal stove is directly below the machine and itshot products of combustion pass up through the coils, some of which arescreened by the rotating screen. The effect is that the coils aresubjecting to induction owing to the change in permeability of thenickel cores, according as they are heated, or as they cool when thescreen is interposed. The two commutator segments are in constantrelation to the screen, and current is collected therefrom and by thecollecting rings is taken to the outside circuit. 443 STANDARD ELECTRICAL DICTIONARY. Pyromagnetism. The development of new magnetic properties or alteration of magneticsensibility in a body by heat. Nickel and iron are much affected asregards their paramagnetic power by rise of temperature. Fig. 280. PYROMAGNETIC GENERATOR. Pyrometer, Siemens' Electric. An instrument for measuring high temperatures by the variations inelectric resistance in a platinum wire exposed to the heat which is tobe measured. Q. Symbol for electric quantity. Quad. (a) A contraction for quadrant, used as the unit of inductance; the henry. (b) A contraction for quadruplex in telegraphy. [Transcriber's note: A modern use of "quad" is a unit of energy equal to1E15 (one quadrillion) BTU, or 1. 055E18 joules. Global energyproduction in 2004 was 446 quad. ] Quadrant. A length equal to an approximate earth quadrant, equal to 1E9centimeters. It has been used as the name for the unit of inductance, the henry, q. V. Synonym--Standard Quadrant. 444 STANDARD ELECTRICAL DICTIONARY. Quadrant, Legal. The accepted length of the quadrant of the earth, 9. 978E8 instead of 1E9centimeters; or to 9, 978 kilometers instead of 10, 000 kilometers. Quadrature. Waves or periodic motions the angle of lag of one of which, withreference to one in advance of it, is 90°, are said to be in quadraturewith each other. [Transcriber's note: If the voltage and current of a power line are inquadrature, the power factor is zero (cos(90°) = 0) and no real poweris delivered to the load. ] Qualitative. Involving the determination only of the presence or absence of asubstance or condition, without regard to quantity. Thus a compass heldnear a wire might determine qualitatively whether a current was passingthrough the wire, but would not be sufficient to determine its quantity. (See Quantitative. ) Quality of Sound. The distinguishing characteristic of a sound other than its pitch; thetimbre. It is due to the presence with the main or fundamental sound of otherminor sounds called overtones, the fundamental note prevailing and theother ones being superimposed upon it. The human voice is very rich inovertones; the telephone reproduces these, thus giving the personalpeculiarities of every voice. Synonym--Timbre. Quantitative. Involving the determination of quantities. Thus a simple test wouldindicate that a current was passing through a wire. This would be aqualitative test. If by proper apparatus the exact intensity of thecurrent was determined, it would be a quantitative determination. (SeeQualitative. ) Quantity. This term is used to express arrangements of electrical connections forgiving the largest quantity of current, as a quantity armature, meaningone wound for low resistance. A battery is connected in quantity when the cells are all in parallel. It is the arrangement giving the largest current through a very smallexternal resistance. The term is now virtually obsolete (Daniell); "in surface, " "inparallel, " or "in multiple arc" is used. Quantity, Electric. Electricity may be measured as if it were a compressible gas, bydetermining the potential it produces when stored in a definedrecipient. In this way the conception of a species of quantity isreached. It is also measured as the quantity of current passed by aconductor. Thus a body whose surface is more or less highly charged withelectricity, is said to hold a greater or less quantity of electricity. It may be defined in electrostatic or electro-magnetic terms. (SeeQuantity, Electrostatic--Quantity, Electro-magnetic. ) 445 STANDARD ELECTRICAL DICTIONARY. Quantity. Electro-magnetic. Quantity is determined electro-magnetically by themeasurement of current intensity for a second of time: its dimensionsare therefore given by multiplying intensity or current strength bytime. The dimensions of intensity are ( (M^. 5) * (L^. 5) ) / Ttherefore the dimensions of electro-magnetic quantity are ( ( (M^. 5) * (L^. 5) ) / T ) * T = ( (M^. 5) * (L^. 5) ) Quantity, Electro-magnetic, Practical Unit of. The quantity of electricity passed by a unit current in unit time; thequantity passed by one ampere in one second; the coulomb. It is equal to 3E9 electrostatic absolute units of quantity and to 0. 1of the electro- magnetic absolute unit of quantity. One coulomb is represented by the deposit of . 00111815 gram, or . 017253 grain of silver, . 00032959 gram, or . 005804 grain of copper, . 0003392 gram, or . 005232 grain of zinc. If water is decomposed by a current each coulomb is represented by thecubic centimeters of the mixed gases (hydrogen and oxygen) given by thefollowing formula. ( 0. 1738 * 76 * (273 + Cº ) ) / ( h * 273 )in which Cº is the temperature of the mixed gases in degree centigradeand h is thepressure in centimeters of mercury column; or by ( 0. 01058 * 30 (491 + Fº - 32) ) / (h * 491 )for degrees Fahrenheit and inches of barometer. [Transcriber's note: 6. 24150962915265E18 electrons is one coulomb. ] Quantity, Electrostatic. Quantity is determined electro-statically by the repulsion a charge ofgiven quantity exercises upon an identical charge at a known distance. The force evidently varies with the product of the two quantities, andby the law of radiant forces also inversely with the square of thedistance. The dimensions given by these considerations is Q * Q/(L*L). This is the force of repulsion. The dimensions of a force are(M * L) /(T^2). Equating these two expressions we have: (Q^2)/(L^2) = (M*L)/(T^2) or Q = ((M^. 5)*(L^1. 5)) / Twhich are the dimensions of electrostatic quantity. Quantity, Meter. An electric meter for determining the quantity of electricity whichpasses through it, expressible in coulombs or ampere hours. Allcommercial meters are quantity meters. 446 STANDARD ELECTRICAL DICTIONARY. Quartz. A mineral, silica, SiO2. It has recently been used by C. V. Boys andsince by others in the making of filaments for torsion suspensions. Themineral is melted, while attached to an arrow or other projectile. It istouched to another piece of quartz or some substance to which it adheresand the arrow is fired off from the bow. A very fine filament ofsurpassingly good qualities for galvanometer suspension filaments isproduced. As a dielectric it is remarkable in possessing but one-ninth theresidual capacity of glass. Quicking. The amalgamating of a surface of a metallic object before silverplating. It secures better adhesion of the deposit. It is executed bydipping the article into a solution of a salt of mercury. A solution ofmercuric nitrate 1 part, in water 100 parts, both by weight, is used. R. (a) Abbreviation and symbol for Reamur, as 10º R. , meaning 10º by theReamur thermometer. (See Reamur Scale. ) (b) Symbol for resistance, as in the expression of Ohm's Law C=E/R. (rho, Greek r) Symbol for specific resistance. Racing of Motors. The rapid acceleration of speed of a motor when the load upon it isremoved. It is quickly checked by counter-electro-motive force. (SeeMotor, Electric. ) Radian. The angle whose arc is equal in length to the radius; the unit angle. Radiant Energy. Energy, generally existing in the luminiferous ether, kinetic andexercised in wave transmission, and rendered sensible by conversion ofits energy into some other form of energy, such as thermal energy. If the ether waves are sufficiently short and not too short, theydirectly affect the optic nerve and are known as light waves; they maybe so short as to be inappreciable by the eye, yet possess the power ofdetermining chemical change, when they are known as actinic waves; theymay be also so long as to be inappreciable by the eye, when they may beheat-producing waves, or obscure waves. Other forms of energy may be radiant, as sound energy dispersed by theair, and gravitational energy, whose connection with the ether has notyet been demonstrated. Radiation. The traveling or motion of ether waves through space. [Transcriber's note: The modern term corresponding to this definition isphotons. The modern concept of radiation also includes particles--neutrons, protons, alpha (helium) and beta (electrons) rays and otherexotic items. ] Radicals. A portion of a molecule, possessing a free bond and hence free tocombine directly. A radical never can exist alone, but is onlyhypothetical. An atom is a simple radical, an unsaturated group of atomsis a compound radical. 447 STANDARD ELECTRICAL DICTIONARY. Radiometer. An instrument consisting of four vanes poised on an axis so as to befree to rotate, and contained in a sealed glass vessel almost perfectlyexhausted. The vanes of mica are blackened on one side. On exposure to light or a source of heat (ether waves) the vanes rotate. The rotation is due to the beating back and forth of air molecules fromthe surface of the vanes to the inner surface of the glass globe. Radiometer, Electric. A radiometer in which the motion of the molecules of air necessary forrotation of the vane is produced by electrification and not by heating. Radio-micrometer. An instrument for detecting radiant energy of heat or light form. Itconsists of a minute thermopile with its terminals connected by a wire, the whole suspended between the poles of a magnet. A minute quantity ofheat produces a current in the thermopile circuit, which, reacted on bythe field, produces a deflection. A convex mirror reflecting light isattached so as to move with the thermopile. The instrument is ofextraordinary sensitiveness. It responds to . 5E-6 of a degree Centigradeor about 1E-6 degree Fahrenheit. Radiophony. The production of sound by intermittent action of a beam of light upon abody. With possibly a few exceptions all matter may produce sound byradiophouy. Range Finder. An apparatus for use on shipboard to determine the distance of anothership or object. It is designed for ships of war, to give the range offire, so as to set the guns at the proper elevation. The generalprinciple involved is the use of the length of the ship if possible, ifnot of its width, as a base line. Two telescopes are trained upon theobject and kept trained continuously thereon. The following describesthe Fiske range finder. The range finder comprises two fairly powerful telescopes, each mountedon a standard, which can be rotated round a vertical axis, correspondingwith the center of the large disc shown in the engraving. One-half ofthe edge of this disc is graduated to 900 on either side of a zeropoint, and below the graduation is fixed a length of platinum silverwire. This wire only extends to a distance of 81. 10 on either side ofzero, and is intended to form two arms of a Wheatstone bridge. Thesliding contact is carried by the same arm as the telescope standards, so that it moves with the telescope. The two instruments are mounted ata known distance apart on the ship, as shown diagrammatically in thecut. Here A and B are the centers of the two discs, C and D the armscarrying the telescopes, and E and F the platinum silver wires. Supposethe object is at T, such that A B T is a right angle, thenAT=AB/sin(ATB). 448 STANDARD ELECTRICAL DICTIONARY. If the two sectors are coupled up as shown, with a battery, h, and agalvanometer, by the wires, a b and c d, then since the arm, e, on beingaligned on the object takes the position c1 while d remains at zero, theWheatstone bridge formed by these segments and their connections will beout of balance, and a current will flow through the galvanometer, whichmay be so graduated as to give the range by direct reading, since thecurrent through it will increase with the angle A T B. Fig. 281. RANGE FINDER. In general, however, the angle A B T will not be a right angle, but someother angle. In this case AT = AB / sin(A T B) * sin( A B T), and henceit will only be necessary to multiply the range reading on thegalvanometer by the sine of the angle A B T, which can be read directlyby the observer at B. This multiplication is not difficult, but bysuitably arranging his electrical appliances Lieutenant Fiske hassucceeded in getting rid of it, so that the reading of the galvanometeralways gives the range by direct reading, no matter what the angle at Bmay be. To explain this, consider the two telescopes shown in the cut inthe positions C and D; the whole current then has a certain resistance. 449 STANDARD ELECTRICAL DICTIONARY. Next suppose them, still remaining parallel, in the positions C1 and D1. The total resistance of the circuit is now less than before, and henceif C1, one of the telescopes, is moved out of parallel to the other, through a certain angle, the current through the galvanometer will begreater than if it were moved through an equal angle out of a parallelwhen the telescopes were in the positions C and D. The range indicatedis, therefore, decreased, and by properly proportioning the variousparts it is found that the range can always be read direct from thegalvanometer, or in other words the multiplication of A B/sin( A T B )by sin( A B T ) is to all intents and purposes performed automatically. There is, it is true, a slight theoretical error; but by using a smallstorage battery and making the contents carefully it is said to beinappreciable. Each telescope is fitted with a telephone receiver andtransmitter, so that both observers can without difficulty decide onwhat point to align their telescopes. It will be seen that it isnecessary that the lines of sight of two telescopes should be parallelwhen the galvanometer indicates no current. It has been proposed toaccomplish this by sighting both telescopes on a star near the horizon, which being practically an infinite distance away insures theparallelism of the lines of sight. Rate Governor. An apparatus for securing a fixed rate of vibration of a vibrating reed. It is applied in simultaneous telegraphy and telephoning over one wire. The principle is that of the regular make and break mechanism, with thefeature that the contact is maintained during exactly one-half of theswing of the reed. The contact exists during the farthest half of theswing of the reed away from the attracting pole. Fig. 282. LANGDON DAVIRS' RATE GOVERNOR. In the left hand figure of the cut, K is the key for closing thecircuit. A is the base for attachment of the reed. V is thecontact-spring limited in its play to the right by the screw S. C is theactuating magnet. By tracing the movements of the reed, shown on anexaggerated scale in the three right hand figures, it will be seen thatthe reed is in electric contact with the spring during about one-halfits movement. The time of this connection is adjustable by the screw S. Synonym--Langdon Davies' Rate Governor or Phonophone. 450 STANDARD ELECTRICAL DICTIONARY. Ray, Electric. Raia torpedo. The torpedo, a fish having the same power of giving electric shocks asthat possessed by the electric eel, q. V. (See also Animal Electricity. ) Fig. 283. TORPEDO OR ELECTRIC RAY Reaction of Dynamo, Field and Armature. A principle of the dynamo current generator, discovered by Soren Hjorthof Denmark. When the armature is first rotated it moves in a field due to theresidual magnetism of the field magnet core. This field is very weak, and a slight current only is produced. This passing in part or in wholethrough the field magnet cores slightly strengthens the field, whoseincreased strength reacts on the armature increasing its current, whichagain strengthens the field. In this way the current very soon reachesits full strength as due to its speed of rotation. The operation is sometimes termed building up. Sometimes, when there is but a trace of residual magnetism, it is veryhard to start a dynamo. Reading Telescope. A telescope for reading the deflections of a reflecting galvanometer. A long horizontal scale is mounted at a distance from the galvanometerand directly below or above the centre of the scale a telescope ismounted. The telescope is so directed that the mirror of thegalvanometer is in its field of view, and the relative positions ofmirror, scale and telescope are such that the image of the scale in thegalvanometer mirror is seen by the observer looking through thetelescope. Under these conditions it is obvious that the graduation of the scalereflected by the mirror corresponds to the deflection of thegalvanometer needle. The scale may be straight or curved, with the galvanometer in the lattercase, at its centre of curvature. Reamur Scale. A thermometer scale in use in some countries of Continental Europe. Thetemperature of melting ice is 0°; the temperature of condensing steamis 80°; the degrees are all equal in length. For conversion tocentigrade degrees multiply degrees Reamur by 5/4. For conversion toFahrenheit degrees multiply by 9/4 and add 32 if above 0° R. , and ifbelow subtract 32. Its symbol is R. , as 10° R. 451 STANDARD ELECTRICAL DICTIONARY. Recalescence. A phenomenon occurring during the cooling of a mass of steel, when itsuddenly emits heat and grows more luminous for an instant. It is aphase of latent heat, and marks apparently the transition from anon-magnetizable to a magnetiz able condition. Receiver. In telephony and telegraphy, an instrument for receiving a message asdistinguished from one used for sending or transmitting one. Thus the Bell telephone applied to the ear is a receiver, while themicrophone which is spoken into or against is the transmitter. Receiver, Harmonic. A receiver including an electro-magnet whose armature is an elasticsteel reed, vibrating to a particular note. Such a reed responds to aseries of impulses succeeding each other with the exact frequency of itsown natural vibrations, and does not respond to any other rapid seriesof impulses. (See Telegraph Harmonic. ) Reciprocal. The reciprocal of a number is the quotient obtained by dividing one bythe number. Thus the reciprocal of 8 is 1/8. Applied to fractions the above operation is carried out by simplyinverting the fraction. Thus the reciprocal of 3/4 is 4/3 or 1-1/3. Record, Telephone. Attempts have been made to produce a record from the vibrations of atelephone disc, which could be interpreted by phonograph or otherwise. Fig. 284. MORSE RECORDER OR EMBOSSER. 452 STANDARD ELECTRICAL DICTIONARY. Recorder, Morse. A telegraphic receiving apparatus for recording on a strip of paper thedots and lines forming Morse characters as received over a telegraphline. Its general features are as follows: A riband or strip of paper is drawn over a roller which is slightlyindented around its centre. A stylus or blunt point carried by avibrating arm nearly touches the paper. The arm normally is motionlessand makes no mark on the paper. An armature is carried by the arm and anelectro-magnet faces the armature. When a current is passed through themagnet the armature is attracted and the stylus is forced against thepaper, depressing it into the groove, thus producing a mark. When thecurrent ceases the stylus is drawn back by a spring. Fig. 285. INKING ROLLER MECHANISM OF MORSE RECORDER. In some instruments a small inking roller takes the place of the stylus, and the roller is smooth. The cut, Fig. 285, shows the plan view of theink-roller mechanism. J is the roller, L is the ink well, Cl is the armby which it is raised or lowered by the electro-magnet, as in theembosser. S S is the frame of the instrument, and B the arbor to whichthe arm carrying the armature is secured, projecting to the right. Aspring is arranged to rub against the edge of the inking roller andremove the ink from it. The paper is fed through the apparatus by clockwork. At the present daysound reading has almost entirely replaced the sight reading of therecorder. Recorder, Siphon. A recording apparatus in which the inked marks are made on a strip ofpaper, the ink being supplied by a siphon terminating in a capillaryorifice. In the cut N S represents the poles of a powerful electro-magnet. Arectangular coil bb of wire is suspended between the coils. A stationaryiron core a intensifies the field. The suspension wire f f 1 has itstension adjusted at h. This wire acts as conductor for the current. 453 STANDARD ELECTRICAL DICTIONARY. The current is sent in one or the other direction or is cut off inpractice to produce the desired oscillations of the coil b b. A glasssiphon n l works upon a vertical axis l. One end l is immersed in an inkwell m. Its longer end n touches a riband of paper o o. The thread kattached to one side of the coil pulls the siphon back and forthaccording to the direction of current going through the electro-magnetcores. A spiral spring adjusted by a hand-screw controls the siphon. Inoperation the siphon is drawn back and forth producing a zigzag line. The upward marks represent dots, the downward ones dashes. Thus theTelegraphic Code can be transmitted on it. To cause the ink to issueproperly, electrification by a static machine has been used, when thestylus does not actually touch the paper, but the ink is ejected in aseries of dots. Fig. 286. SIPHON RECORDER. Reducteur for Ammeter. A resistance arranged as a shunt to diminish the total current passingthrough an ammeter. It is analogous to a galvanometer shunt. (SeeMultiplying Power of Shunt. ) Reducteur for Voltmeter. A resistance coil connected in series with a Voltmeter to diminish thecurrent passing through it. Its resistance being known in terms of theresistance of the voltmeter it increases the range of the instrument sothat its readings may cover double or more than double their normalrange. Reduction of Ores, Electric. Treatment of ores by the electric furnace (see Furnace, Electric. ) Theore mixed with carbon and flux is melted by the combined arc andincandescent effects of the current and the metal separates. In anothertype the metal is brought into a fusible compound which is electrolyzedwhile fused in a crucible. Finally processes in which a solution of asalt of the metal is obtained, from which the metal is obtained byelectrolysis, may be included. Aluminum is the metal to whose extractionthe first described processes are applied. 454 STANDARD ELECTRICAL DICTIONARY. Refraction, Electric Double. Double refraction induced in some materials by the action of either anelectrostatic, magnetic or an electro-magnetic field. The intensity or degree of refracting power is proportional to thesquare of the strength of field. Refreshing Action. In electro-therapeutics the restoration of strength or of nerve force bythe use of voltaic alternatives, q. V. Region, Extra-polar. In electro-therapeutics the area or region of the body remote from thetherapeutic electrode. Region, Polar. In electro-therapeutics the area or region of the body near thetherapeutic electrode. Register, Electric. There are various kinds of electric registers, for registering themovements of watchmen and other service. Contact or press buttons may bedistributed through a factory. Each one is connected so that when thecircuit is closed thereby a mark is produced by the depression of apencil upon a sheet or disc of paper by electro-magnetic mechanism. Thepaper is moved by clockwork, and is graduated into hours. For eachpush-button a special mark may be made on the paper. The watchman isrequired to press the button at specified times. This indicates hismovements on the paper, and acts as a time detector to show whether hehas been attending to his duty. Register, Telegraphic. A term often applied to telegraph recorders, instruments for producingon paper the characters of the Morse or other alphabet. Regulation, Constant Current. The regulation of a dynamo so that it shall give a constant currentagainst any resistance in the outer circuits, within practical limits. It is carried out in direct current machines generally by independentregulators embodying a controlling coil with plunger or some equivalentelectro-magnetic device inserted in the main circuit and necessarily oflow resistance. In some regulators the work of moving the regulator isexecuted mechanically, but under electrical control; in others theentire work is done by the current. A typical regulator or governor (Golden's) of the first class comprisestwo driven friction wheels between which is a driving friction wheel, which can engage with one driven wheel only at once. It is brought intoengagement with one or the other by a solenoid and plunger. 455 STANDARD ELECTRICAL DICTIONARY. As it touches one wheel it turns it in one direction. This moves asliding contact in one direction so as to increase a resistance. Thiscorresponds to a motion of the plunger in one direction. As the drivingwheel moves in the opposite direction by a reverse action it diminishesthe resistance. Thus the increase and decrease of resistance correspondto opposite movements of the solenoid plunger, and consequently toopposite variations in the current. The whole is so adjusted that thevariations in resistance maintain a constant amperage. The resistance isin the exciting circuit of the dynamo. In Brush's regulator, which is purely mechanical, a series dynamo ismade to give a constant current by introducing across the field magnetsa shunt of variable resistance, whose resistance is changed by anelectro-magnet, whose coils are in circuit with the main current. Carbonresistance discs are used which the electro-magnet by its attraction forits armature, presses with varying intensity. This alters theresistance, decreasing it as the current increases and the reverse. Asthe connection is in shunt this action goes to maintain a constantcurrent. Regulation, Constant Potential. The regulation of constant potential dynamos is executed on the samelines as that of constant current dynamos. If done by a controllingcoil, it must for constant potential regulation be wound with fine wireand connected as a shunt for some part of the machine. Regulation of Dynamos. The regulation of dynamos so that they shall maintain a constantpotential difference in the leads of their circuit for multiple arcsystems or shall deliver a constant current in series systems. Hence twodifferent systems of regulation are required, (a) constant potentialregulation--(b) constant current regulation. The first named is by farthe more important, as it concerns multiple arc lighting, which is thesystem universally used for incandescent lighting. S. P. Thompson thus summarizes the methods of governing or regulatingdynamos. Premising that alteration of the magnetic flux is the almostuniversal way of control, it can be done in two ways; first, by varyingthe excitation or ampere turns of the field, and second by varying thereluctance of the magnetic circuit. The excitation or magnetic flux maybe varied (a) by hand, with the aid of rheostats and commutators in the excitingcircuit; (b) automatically, by governors, taking the place of the hand; (c) by compound windings. The magnetic circuit may have its reluctancecaused to vary in several ways; (d) by moving the pole pieces nearer to or further from the armature; (e) by opening or closing some gap in the magnetic circuit (field-magnetcore); (f) by drawing the armature endways from between the pole pieces; (g) by shunting some of the magnetic lines away from the armature by amagnetic shunt. The latter magnetic circuit methods d, e, f, and g, have never met withmuch success except on small machines or motors. Method e is adopted inthe Edison motor, the yoke being withdrawn or brought nearer the coresof the coils. (See Regulation, Constant Current-Regulation, constantPotential. ) 456 STANDARD ELECTRICAL DICTIONARY. Reguline. Adj. Having the characteristics of a piece of metal, being flexible, adherent, continuous, and coherent. Applied to electrolytic deposits. Relative. Indicating the relation between two or more things without reference toabsolute value of any one of them. Thus one lamp may be of relativelydouble resistance compared to another, but this states nothing of theresistance in ohms of either lamp. Relay. A receiving instrument which moves in accordance with impulses ofcurrents received, and in so moving opens and closes a local circuit, which circuit may include as powerful a battery as required ordesirable, while the relay may be on the other hand so delicate as towork with a very weak current. Fig. 287. RELAY. The typical relay includes an electro-magnet and armature. To the latteran arm is attached and the lower end of the arm works in pivots. As thearmature is attracted the arm swings towards the magnet. When thecurrent is cut off, the armature and arm are drawn back by a spring. When the arm swings towards the magnet its upper end touching a contactscrew closes the local circuit. When it swings back it comes in contactwith a second screw, with insulated point, and opens the circuit as itleaves the first named screw. One terminal connects with the arm through the pivots and frame. Theother connects with the contact screw through the frame carrying it. Synonym--Relay Magnet. 457 STANDARD ELECTRICAL DICTIONARY. Relay Bells. Bells connected by relay connection to a main line for acoustictelegraphy. A stroke on one bell indicates a dot and on the other adash. The system is now nearly extinct. Relay, Box-sounding. A relay which is surrounded by or mounted on a resonator or wooden boxof such proportions and size as to reinforce the sound. This enables arelay to act as a sounder, its weak sounds being virtually magnified soas to be audible. Relay Connection. A connection used in telegraphy, including a local battery, with a shortcircuit normally open, but closed by a switch and a sounder or otherappliance. The latter is made very sensitive so as to be worked by afeeble current, and is connected to the main line. A very slight currentcloses the switch and the local battery comes into operation to work asounder, etc. When the current ceases on the main line the switch opensand throws the local battery out of action. The switch is termed arelay, q. V. A long main line may thus produce strong effects at distantstations, the intensity of action depending on the local battery. Fig. 288. RELAY OR LOCAL CIRCUIT. Relay, Differential. A relay containing two coils wound differentially, and of the samenumber of turns and resistance. If two equal currents pass through thecoils they counteract each other and no action takes place. If there isa difference in the currents the relay acts as one coil preponderates. The coils may be wound for uneven currents with different resistance andnumber of turns. Relay, Microphone. A relay connection applied to a telephone circuit. It consists of amicrophone mounted in front of the diaphragm of a telephone receiver. Incircuit with the microphone is a battery and second telephone receiver. The microphone is supposed to intensify the sounds of the firsttelephone. 458 STANDARD ELECTRICAL DICTIONARY. Relay, Polarized. A relay whose armature is of steel, and polarized or permanentlymagnetized, or in which a permanent magnet is used as the basis for theelectro-magnets. In the relay shown in the cut the coils shown aremounted on cores carried on the end of a powerful bent permanent magnet. Thus when no current passes their upper poles are both of the same sign, and the horizontally vibrating tongue is held by the magnetic attractionagainst one or the other pole piece. If a current is sent through theelectro-magnet it gives opposite polarity to the two polar extensions. As the end of the vibrating tongue is of polarity determined by thepermanent magnet it is attracted to one pole and repelled from theother. On cessation of current it remains attached by the permanentmagnetism. If now a current is sent in the opposite direction the twopoles again acquire opposite polarity, the reverse of the former, andthe tongue flies across to the opposite side. On cessation of current itremains attached as before by the permanent magnetism. In its movements to and fro the relay tongue opens and closes a contact, so as to work a sounder or other apparatus. The polarized relay is ofhigh sensibility, and requires little or no change of adjustment. Fig. 288. POLARIZED RELAY Reluctance. In a magnetic circuit or portion thereof, the resistance offered to theflow of lines of force. The magnetic circuit as has already been statedis treated like an electric circuit, and in it reluctance occupies theplace of resistance in the electric circuit. It is the reciprocal ofpermeance. S. P. Thompson expresses the law thus: Total number of magnetic lines = (magneto-motive force) / (magneticreluctance) Synonyms--Magnetic Reluctance-Magnetic Resistance. Reluctance, Unit of. The reluctance of a circuit through which unit magnetizing power(magneto-motive force) can produce a unit of induction or one line offorce. This value is very high; the reluctance of ordinary magneticcircuits ranges from 1E-5 to 1E-8 unit of reluctance. Reluctivity. Specific reluctance; the reluctance of a cube of material whose edgemeasures one centimeter in length. It is a quality bearing the samerelation to reluctance that permeability does to permeance. It is defined as the reciprocal of magnetic permeability. (Kenelly. ) Ifplotted as a curve for different values of the magnetizing force it isfound to be nearly a straight line, a linear function of the magnetizingforce, H with the equation a + b H. Reluctivity is the property of asubstance; reluctance is the property of a circuit. 459 STANDARD ELECTRICAL DICTIONARY. Remanence. The residual magnetism left after magnetic induction, expressed in linesof force per square centimeter. Repeater. In telegraphy an instrument for repeating the signals through a secondline. It is virtually a relay which is operated by the sender, and whichin turn operates the rest of the main line, being situated itself atabout the middle point of the distance covered. In the simpler forms ofrepeater two relays are used, one for transmission in one direction theother for transmission in the other. An attendant switches one or theother in as required. Thus a common relay is virtually a repeater for its local circuit. Ifsuch a relay is placed half way down a line, and if the line beyond itis connected as its local, it becomes a repeater. Some forms of repeaters are automatic, and repeat both ways without theneed of an attendant. It is the practice to somewhat prolong the signals sent through arepeater. Replenisher, Sir William Thomson's. A static accumulating influence machine contained in Thomson's quadrantelectrometer and used to change the quadrants. The cut shows thehorizontal section and construction of the apparatus. It contains two gilt brass inductors A B, and two eccentric sectors orcarriers, C, D, which are mounted on an ebonite spindle, which is spunaround by the fingers. The springs s s1 connect each with its inductor;the springs S S1 connect only each other, and touch the sectors as theyturn around. One of the inductors may be always assumed to be of slightly higherpotential than that of the other one. When the carriers are in contactwith the springs S S1 they are each charged by induction withelectricity opposite in sign to that of the nearest quadrant. As theyleave the springs S S1 in their rotation, they next touch the springs ss1, but of the recently opposite inductor. They share each a portion ofits charge with the inductors building up their charges. The action isrepeated over and over again as they rotate. Fig. 290. THOMSON'S REPLENISHER. 460 STANDARD ELECTRICAL DICTIONARY. Reservoir, Common. A term applied to the earth, because all electrified bodies dischargeinto it if connected thereto. Fig. 289. DIAGRAM OF THOMSON'S REPLENISHER. Residual Atmosphere. The air left in a receiver after exhaustion by an air pump. Thequantity, where good air pumps are used, is very minute. Residue, Electric. The residual charge of a condenser. (See Charge, Residual. ) Resin. (a) The product obtained by non-destructive distillation of the juice ofthe pitch pine. It is the solid residue left after the turpentine hasbeen evaporated or distilled. It is a mixture of abietic acid C44 H64 O5and pinic acid C20 H30 O2. It is an insulator; its specific inductivecapacity is 2. 55. (Baltzmann. ) Synonyms--Colophony--Rosin. (b) The name is also generally applied to similar substances obtainedfrom the sap of other trees; thus shellac is a resin. The resins are afamily of vegetable products; the solid portions of the sap of certaintrees. Common resin, lac, dragons blood, are examples. They are alldielectrics and sources of resinous or negative electricity when rubbedwith cotton, flannel, or silk. (See Electrostatic Series. ) 461 STANDARD ELECTRICAL DICTIONARY. Resinous Electricity. Negative electricity; the electricity produced upon the surface of aresinous body by rubbing it; such a body is shellac or sealing wax;flannel and other substances may be used as the rubbing material. (SeeElectrostatic Series. ) Resistance. (a) The quality of an electric conductor, in virtue of which it opposesthe passage of an electric current, causing the disappearance ofelectro-motive force if a current passes through it, and convertingelectric energy into heat energy in the passage of a current through it. If a current passes through a conductor of uniform resistance there is auniform fall of potential all along its length. If of uneven resistancethe fall in potential varies with the resistance. (See Potential, Fallof. ) The fall of potential is thus expressed by Daniell. "In a conductor, saya wire, along which a current is steadily and uniformly passing, thereis no internal accumulation of electricity, no density of internaldistribution; there is, on the other hand, an unequally distributedcharge of electricity on the surface of the wire, which results in apotential diminishing within the wire from one end of the wire to theother. " Resistance varies inversely with the cross section of a cylindrical orprismatic conductor, in general with the average cross-section of anyconductor, and in the same sense directly with its true or average orvirtual length. It varies for different substances, and for differentconditions as of temperature and pressure for the same substance. A riseof temperature in metals increases the resistance, in some badconductors a rise of temperature decreases the resistance. 462 STANDARD ELECTRICAL DICTIONARY. Approximately, with the exception of iron and mercury, the resistance ofa metallic conductor varies with the absolute temperature. This is veryroughly approximate. Except for resistance energy would not be expended in maintaining acurrent through a circuit. The resistance of a conductor may be supposedto have its seat and cause in the jumps from molecule to molecule, whichthe current has to take in going through it. If so a current confined toa molecule would, if once started, persist because there would be noresistance in a molecule. Hence on this theory the Ampérian currents(see Magnetism, Ampere's Theory of) would require no energy for theirmaintenance and Ampére's theory would become a possible truth. When metals melt their resistance suddenly increases. Light rays falling on some substances, notably selenium, q. V. , vary theresistance. Longitudinal stretching of a conductor decreases it, it increases withlongitudinal compression, and increases in iron and diminishes in tinand zinc when a transverse stress tends to widen the conductor. (b) The term resistance is used to express any object or conductor usedin circuit to develop resistance. [Transcriber's note: At room temperatures, the thermal motion of ions inthe conductor's crystal lattice scatters the electrons of the current. Imperfections of the lattice contribute slightly. At low temperaturessuperconductivity (zero resistance) can occur because an energy gapbetween the electrons and the crystal lattice prevents any interaction. At the time of this book, none of this was known. "Jumps from moleculeto molecule" is a good guess. ] Resistance, Apparent. Impedance; the virtual resistance of a circuit including the spuriousresistance due to counter-electromotive force. It may be made up of trueresistance and partly of an inductive reaction, as it represents the netfactor, the entire obstruction to the passage of a current, and notmerely a superadded resistance or counter-electro-motive force. Synonym--Impedance. [Transcriber's note: Impedance can also have a component due tocapacitance. ] Resistance, Asymmetrical. Resistance which varies in amount in different directions through aconductor. It implies a compound or composite conductor such as thehuman system. The presence of counter-electro-motive force in differentparts of a conductor may bring about asymmetrical resistance. Resistance, B. A. Unit of. The British Association Ohm. (See Ohm, B. A. ) 463 STANDARD ELECTRICAL DICTIONARY. Resistance Box. A box filled with resistance coils. The coils are connected in series sothat a circuit including any given number has their aggregate resistanceadded to its own. The terminals of consecutive coils are connected toshort blocks of brass which are secured to the top of the box, lyingflatwise upon it, nearly but not quite in contact with each other. Plugsof brass are supplied which can go in between pairs of blocks, whichhave a pair of grooves reamed out to receive them. Such plugs shortcircuit the coil below them when in position. The cut shows how suchcoils are connected and the use of plugs to short circuit them. Thediagram shows the top of a Wheatstone bridge, q. V. , resistance box withconnections for determining resistances. Fig. 291. RESISTANCE BOX. Resistance Box, Sliding. A resistance box whose coils are set in a circle. Two metal arms withhandles are pivoted at the centre of the circle and by moving themaround they make and break contacts so as to throw the coils in and outof circuit. The object is to permit an operator to adjust resistancewithout looking at the box--an essential in duplex telegraphy. Resistance, Breguet Unit of. The same in origin as the Digney Unit. (See Resistance, Digney Unit of. ) It is equal to 9. 652 Legal Ohms. Resistance, Carbon. A resistance, a substitute for a resistance coil; it is made of carbon, and is of various construction. In the Brush dynamo regulator a set offour vertical piles of plates of retort carbon, q. V. , is used as aresistance, whose resistance is made to vary by changing the pressure. This pressure automatically increases as the current strength increases, thus reducing the resistance. 464 STANDARD ELECTRICAL DICTIONARY. Resistance Coil, Standard. A standard or resistance issued by the Electric Standard Committee ofGreat Britain. The cut shows the standard ohm. It is formed either ofGerman silver, or of an alloy of silver, 66. 6 per cent. And platinum, 33. 4 per cent. The wire is insulated and doubled before winding asdescribed before. (See Coil, Resistance. ) The two ends of the wire aresoldered, each one to a heavy copper wire or rod r. The whole coil isenclosed in a brass case, and is enclosed with paraffine melted in at A. A place for a thermometer is provided at t. By immersing the lower partof the case B in water of different degrees of heat any desiredtemperature can be attained. Fig. 292. STANDARD OHM COIL. Resistance, Combined. The actual resistance of several parallel conductors starting from thesame point and ending at the same point. If the individual resistance bea b c d .. And the combined resistance be x then we havex = 1 / (( 1/a) + (1/b) + (1/c) + (1/d) + …) Synonym--Joint Resistance. Resistance, Critical. In a series wound dynamo the resistance of the outer circuit above whichthe machine will refuse to excite itself. Resistance, Dielectric. The mechanical resistance of a dielectric to the tendency to perforationor to the strains due to electrification. This is a phase of mechanicalresistance, and is distinct from the electrical or ohmic resistance ofthe same substance. Resistance, Digney Unit of. The resistance of an iron wire, 1 kilometer long, 4 millimetersdiameter, temperature unknown. It is equal to 9. 163 legal ohms. Resistance, Electrolytic. The resistance of an electrolyte to the passage of a current decomposingit. It is almost entirely due to electrolysis and is added to bycounter- electro-motive force, yet it is not treated specifically assuch, but as an actual resistance. When a current of a circuit of toolow voltage to decompose an electrolyte is caused by way of immersedterminals to pass through an electrolyte the resistance appears veryhigh and sometimes almost infinite. If the voltage is increased untilthe electrolyte is decomposed the resistance suddenly drops, and whatshould be termed electrolytic resistance, far lower than the trueresistance, appears. 465 STANDARD ELECTRICAL DICTIONARY. Resistance, English Absolute or Foot-Second Unit of. A unit based on the foot and second. It is equal to (( foot / second ) *1E7), being based on these dimensions. It is equal to 0. 30140 legal ohm. Resistance, Equivalent. A resistance equivalent to other resistances, which may includecounter-electro-motive force. Resistance, Essential. The resistance of the generator in an electric circuit; the same asinternal resistance. Resistance, External. In an electric circuit the resistance of the circuit outside of thegenerator, or battery. Synonym--Non-essential Resistance. Fig. 293. RESISTANCE FRAME. Resistance Frame. An open frame filled with resistance coils of iron, or German silverwire. It is used as a resistance for dynamos and the larger or workingclass of plant. The coils are sometimes connected so that by a switchmoving over a row of studs one or more can be thrown into seriesaccording to the stud the switch is in contact with. Resistance, German Mile Unit of. The resistance of 8, 238 yards of iron wire 1/6 inch in diameter. It isequal to 56. 81 legal ohms. 466 STANDARD ELECTRICAL DICTIONARY. Resistance, Hittorf's. A high resistance, often a megohm, composed of Hittorf's solution, q. V. It is contained in a vertical glass tube near whose upper and lower endsare electrodes of metallic cadmium attached to platinum wires. Thecadmium is melted in glass tubes, the platinum wire is inserted into themelted metal and the tube is broken after all is solid. The resistanceshould show no polarization current. Fig. 294. HITTORF'S RESISTANCE Resistance, Inductive. A resistance in which self-induction is present; such as a coil ofinsulated wire wound around an iron core. Resistance, Insulation. The resistance of the insulation of an insulated conductor. It is statedin ohms per mile. It is determined by immersing a section of the line inwater and measuring the resistance between its conductor and the water. The section must be of known length, and its ends must both be above theliquid. Resistance, Internal. The resistance of a battery, or generator in an electric circuit asdistinguished from the resistance of the rest of the circuit, or theexternal resistance. Synonym--Essential Resistance. Resistance, Jacobi's Unit of. The resistance of a certain copper wire 25 feet long and weighing 345grains. It is equal to 0. 6296 legal ohm. Resistance, Matthiessen's Meter-gram Standard. The resistance of a pure hard drawn copper wire of such diameter thatone meter of it weighs one gram. It is equal to . 1434 Legal Ohms at 0ºC. (32º F. ) Resistance, Matthiessen's Unit of. The resistance of a standard mile of pure annealed copper wire 1/16 inchdiameter, at a temperature of 15. 5º C. (60º F. ). It is equal to 13. 44 legal ohms. 467 STANDARD ELECTRICAL DICTIONARY. Resistance, Meter-millimeter Unit of. The resistance of a wire of copper one meter long and one squaremillimeter in section. It is equal to . 02057 ohms at 0º C. (32º F. ) Theterm may also be applied to the resistance of similar sized wire ofother metals. Resistance, Mil-foot Unit of. The resistance of a foot of copper wire one-thousandth of an inch indiameter. It is equal to 9. 831 ohms at 0º C. (32º F. ) The term may alsobe applied to the resistance of similar sized wire of other metals. Resistance, Non-essential. The resistance of the portion of an electric circuit not within thegenerator; the same as external resistance. Synonym--External Resistance. Resistance, Non-inductive. A resistance with comparatively little or negligible self-induction. Resistance of Human Body. The resistance of the human body is largely a matter of perfection ofthe contacts between its surface and the electrodes. It has beenasserted that it is affected by disease. From 350 to 8, 000 ohms havebeen determined as resistances, but so much depends on the contacts thatlittle value attaches to the results. Resistance, Ohmic. True resistance measured in ohms as distinguished fromcounter-electro-motive force, q. V. The latter is called often spuriousresistance. Synonym--True Resistance. [Transcriber's note: "True" vs. "spurious" are interesting terms, considering that today we define impedance as a combination of "real"resistance and "imaginary" capacitive and inductive reactance. ] Resistance, Reduced. The resistance of a conductor reduced to ohms, or to equivalent lengthsof a column of mercury, 1 square millimeter in cross area. Resistance, Siemen's Unit of. The resistance of a column of mercury 1 meter long and 1 squaremillimeter cross-sectional area at 0º C. (32º F. ) It is equal to . 9431 legal ohm. Resistance, Specific. The relative resistance of a substance. It is expressed as the actualresistance of a cube of the substance which is one centimeter on eachedge. For metals it is usually expressed in microhms, for liquids inohms. The resistances of a specified length of wire of specified diameter ofdifferent substances is often given, and is really a particular way ofstating specific resistances. Synonym--Specific Conduction Resistance. Resistance, Spurious. The counter-electro-motive force, q. V. , operating to prevent a currentbeing produced of what should be its full strength were the trueresistance and actuating electro-motive force only concerned. Suchcounter-electro-motive force may be treated as a spurious resistance andsuch a value in ohms assigned to it as would correspond to its propereffect. 468 STANDARD ELECTRICAL DICTIONARY. In its effect on opposing a current and in resisting its formation itdiffers from true resistance. The latter in diminishing current strengthabsorbs energy and develops heat; spurious resistance opposes anddiminishes a current without absorption of energy or production of heat. [Transcriber's note: "Spurious resistance" is now called reactance, consisting of capacitive reactance and inductive reactance. Thecombination of reactance and (Ohmic/true) resistance is calledimpedance. The calculation of impedance requires complex algebra, notjust real values used in DC circuit analysis. ] Resistance, Steadying. When arc lamps are connected in parallel or multiple arc a smallresistance coil is sometimes placed in series with each lamp forsteadying purposes. It reduces the percentage of variation of resistancein each lamp, which may be caused by a change in the position of thecarbons. Resistance, Swiss Unit of. A unit constructed by the "Administration Suisse, " based on the samedata as the Breguet and the Digney Units. (See Resistance, Digney Unitof) It is equal to 10. 30 legal ohms. Resistance, Thomson's Unit of. A unit of resistance based on the foot and second. It is equal to 0. 3166 legal ohm. Resistance, Unit. Unit resistance is that of a conductor in which unit current is producedby unit electro-motive force. Resistance, Varley's Unit of. The resistance of a standard mile of a special copper wire 1/16 inchdiameter. It is equal to 25. 33 ohms. Resistance, Weber's Absolute Unit. A metric system unit; (meter / second) * 1E7 It is equal to 0. 9089 legal ohm. Resonance, Electric. A set of phenomena known as the Hertz experiments are grouped under thistitle, which phenomena are incidents of and depend on the propagation ofelectric waves through wires or current conductors, as well as throughthe ether. Ordinarily a wire is only a seat of current, and is in itsnature inconsistent with wave propagation through its mass. Such wavesare virtually confined to the exterior of the wire. The point is thatthe current-producing force is supposed to enter the wire at all pointsfrom without, the current not being produced by an end-push. Hence inrapidly recurring waves which are produced by a rapidly pulsatory oralternating current, no time is afforded for the current-producingforce, in this case the wave-producing force, to penetrate into thesubstance of the wire. In one of his experiments Dr. Hertz surrounded awire by a glass tube chemically silvered. The coating was so thin as tobe translucent. Through this metallic layer a current could be inducedin the wire in its interior. Any mechanical layer of metal took up theinduction itself, and protected the central wire. This gave a clue tothe thickness of metal penetrated by the rapid induced waves used by Dr. Hertz. 469 STANDARD ELECTRICAL DICTIONARY. Fig. 295. ELECTRICAL RESONANCE EXCITER. The method used for the production of rapid oscillations is thefollowing. To the terminals of an induction coil two metal spheres AA1are connected as shown. This apparatus is termed the exciter; in itsdischarge a series of isochronous discharges takes place, alternating indirection. The period of duration T of a single one is given by theformula T= 2* PI * squareRoot( LC ), in which C is the capacity and Lis the self-induction. The spheres may be 30 centimeters (11. 8 inches)in diameter, connected each to conductors 0. 5 centimeter (. 2 inch) indiameter and 40 centimeters (15. 7 inches) long each. For the length ofan undulation the formula gives for this apparatus 4. 8 meters (15. 75feet) as the length of a wave, assuming for them the velocity ofpropagation equal to that of light. The exciter may have 10, 000 timesthe rate of oscillation possessed by the plain induction coil. When this apparatus is worked it produces induced waves in everyneighboring conductor. The resonance effects appear in the size of thespark induced. Thus a wire bent into a circle with its ends nearlytouching will give a spark, but if made of proper electrostaticcapacity, corresponding with the particular waves employed, the sparkwill be very much larger. The ring, with its spark gap is termed aresonator. It is used as an explorer to trace the waves. Waves thus produced are transmitted by stone walls and nonconductors ingeneral. A plate of zinc reflects part and transmits part. The reflectedwaves can be traced by the resonator, their angle of reflection beingequal to their angle of incidence. They can be received by one parabolicreflector, reflected to another and brought to a focus. They can bereflected so as to produce interference or loops and nodes, and theloops and nodes can be traced by the resonator. By a prism of asphaltthey are refracted exactly like light. From all this it is concluded that an additional proof is furnished ofthe identity of light and electro-magnetic waves, and a very strongexperimental proof of Maxwell's theory of light is furnished. Synonym--Hertz's Experiments. 470 STANDARD ELECTRICAL DICTIONARY. Fig. 296. ELECTRICAL RESONATOR. Resonator, Electric. A small open electric circuit, with ends nearly touching. When exposedto electric resonance, or to a sympathetic electric oscillatorydischarge, a spark passes from across the gap. The production of thisspark is altogether a matter of the inductance of the resonator. Thesimplest form is a circle of copper wire with its ends nearly touching. The length of the gap is adjustable by bending. A screw adjustment mayalso be provided. Another form is shown in the cut, Fig. 296. Heresheets of tinfoil are used to regulate the electrostatic capacity, whileat m is shown the finger piece for regulating the size of the spark gapa. Synonym--Spark Micrometer. Resultant. The line indicating the result of the application of two or more forcesto a point. Its direction and length give the elements of direction andintensity. (See Forces, Resolution of Forces, Composition ofComponents. ) Resultant Polarity. The magnetic polarity imparted to a mass of iron acted on by two or moreseparate inducing forces or currents. It appears in dynamos and motors. The final polarity is the resultant of the inducing effect of the fieldmagnet poles and of the windings. Retardation. In telegraphy a retardation of the rate of transmission of signals. Itis due to several causes. (a) The self-induction of the circuit, especially if it includes manyelectro-magnets, produces extra currents (see Currents, Extra. ) Theseare opposed to the main current on closing it and hence retard theaction. They are in the same direction on opening it and hence againretard the action. (b) Every line has a certain static capacity. This is affected by theproximity of the lines to the earth. For each signal electricity has tobe charged upon the line until the line is charged to its end with acertain proportion of the initial density. This charging takes time andhence introduces retardation. (c) The cores of the electro-magnets of the relays or sounders are notinstantly magnetized and demagnetized. This magnetic lag, q. V. , introduces retardation. 471 STANDARD ELECTRICAL DICTIONARY. Retardation of Phase. The fractional lagging behind of waves or alternating currents; bylagging behind a portion of a wave length the corresponding phases, asof full amplitude, are kept back or retarded. The phase of currentintensity may be retarded with reference to the electro-motive force bythe introduction of transformers of high capacity with high resistanceon open secondary circuits. [Transcriber's note: Capacitors are used to correct current phase lag. ] Retentivity. Coercitive or coercive force; by virtue of which steel retains itsmagnetism. It is the more modern name, "coercive force" as a term beingrejected by many. Synonyms--Coercive Force--Coercitive Force. Retort Carbon. Carbon deposited in coal gas retorts from decomposition of thehydrocarbons. It is a very hard, pure form, and is of graphiticmodification. Owing to its great hardness it is little used forelectrical purposes, the molded carbons being easier to make. Thedeposition occurs in the regular gas-making process, and is adisadvantage to the working. Return. A line or conductor which is supposed to carry current back to itsstarting point, after it has traversed a line. It may be a wire or thegrounding of the ends of a line [or] may make the earth act as a return, termed ground- or earth-return. The best distinction of a return is toso term the portion of a circuit on which no apparatus is placed. Reversibility. The principal in virtue of which a device for producing a given form ofenergy can absorb the same and do work. The reversibility of the dynamois its quality in virtue of which it can act as a current generator, thereby converting mechanical energy into electric energy, or if acurrent is passed through it, it rotates, doing work, and therebyconverting electric energy into mechanical energy. The knowledge of thisprinciple can be traced back to Jacobi in 1850. Reversible Bridge. A form of Wheatstone's Bridge adapted for reversal of the positions orinterchange of the proportionate arms, v. , so that the accuracy of thecoils can be tested. Rheochord. An apparatus by means of which variable quantities of wire are throwninto the circuit; a rheostat using wire. (See Rheostat, Wheatstone's. ) Rheometer. A galvanometer. (Obsolete. ) 472 STANDARD ELECTRICAL DICTIONARY. Rheomotor. A source of current; a current generator; a producer of potentialdifference. (Obsolete. ) Rheophore. The portion of an active circuit capable of deflecting a magneticneedle. This properly includes all of the metallic conductor of acircuit. (Obsolete. ) Rheoscope. A galvanoscope; an instrument for qualitatively detecting potentialdifference, fall or rise. (See Galvanoscope. ) Rheostat. An adjustable resistance; an apparatus for changing the resistancewithout opening the circuit. Its action may depend on the introductionof variable lengths of mercury column, of some other liquid, or of wireinto a circuit. (See Rheostat, Wheatstone's. ) Rheostat Arm. The third arm of known resistance in a Wheatstone bridge. (SeeProportionate Arms. ) Rheostatic Machine. An apparatus for increasing potential difference. It consists of anumber of static condensers. They are charged in multiple arc or inparallel, and are discharged in series. Secondary batteries may be usedfor the charging; thus a static effect is produced from a galvanicbattery. Rheostat, Wheatstone's. This apparatus consists of two cylinders, one, A, made of brass, theother, B, of wood, with a spiral groove. At its end is a copper ring a. A fine brass wire has one end attached to this ring. Its other end isfastened at e, and it is wound as shown; n and o are binding screwsconnected, one with the cylinder-ring a, the other with the brasscylinder, A. The current entering at o, traverses the wire on B, asthere the windings are insulated by the grooves, thence it passes to mand by A, whose metal short circuits all the wire on it, to thebinding-post n. The handle, d, is turned one way or the other toregulate the length of the wire through which the current must pass. Oneach cylinder there is a square head, one of which is shown at c, sothat the handle can be shifted from one to the other as required; to Aif the wire is to be wound on that cylinder, to B if the reverse isdesired. Fig. 297. WHEATSTONE'S RHEOSTAT. 473 STANDARD ELECTRICAL DICTIONARY. Rheotome. An automatic circuit breaker, one which rapidly opens and closes acircuit, as in the case of the primary of an induction coil aninterrupter. (Obsolete. ) Rheotrope. A pole changer, current reverser, or commutator, g. , such as thecommutator of an induction coil. (Obsolete. ) Rhigolene. A petroleum product; a hydrocarbon of low boiling point. Its vapor isused in flashing (q. V. ) carbon filaments for incandescent lamps. Rhumbs. In a mariners' compass, the thirty-two points, designated, north, northby east, north north east, etc. (See Compass Mariner's-Compass, Pointsof the. ) Rhumkorff Coil. The induction coil, q. V. Rigidity, Molecular. The tendency of molecules to resist rotation or change of position; theassumed cause of magnetic coercive force, or retentivity. Ring Contact. A contact formed by a terminal clip in the shape of a ring, split or cutat one point so that its ends tend to spring together. The otherterminal is a bar which passes into the cut and is tightly pressed bythe elastic ring. Fig. 298. SWITCH WITH RING CONTACTS. 474 STANDARD ELECTRICAL DICTIONARY. Ring, Faraday. A closed ring of iron used as the core of a transformer or inductioncoil. The term is derived from Faraday's classic experiment with such anapparatus when he produced a spark by induction in a secondary circuit. Roaring. A term applied to the noise sometimes produced in a voltaic arc, whenthe electrodes are close together and a heavy current is passing. Rocker. In a dynamo the movable piece, mounted concentrically with thecommutator, and carrying the rocker-arms and brush-holders. By moving itthe brushes are adjusted for proper lead. Rocker Arms. The arms projecting from a rocker and each carrying one of thebrush-holders. Roget's Spiral. An experimental apparatus for illustrating the mutual attraction ofcurrents going in like direction. A cylindrical helix or spiral of wireis suspended by one end. Its lower end just dips into a mercury cup. Anactive circuit is connected, one terminal to the upper end, the otherterminal to the mercury cup, bringing the apparatus in series into thecircuit. The current as it passes causes the coil to shorten, eachspiral attracting its neighbors. This breaks the circuit by drawing thelower end out of the mercury cup. The current being cut off the coilscease to attract each other, and the end dips into the mercury cupagain. This closes the circuit, the coils again attract each other andthe same sequence follows and is repeated over and over again. A brightspark is produced at each break of the mercury contact. Rotation of Liquids, Electro-dynamic. By passing a current through a liquid, such as dilute sulphuric acid, itrotates if exposed to the induction of a current flowing at right anglesto it. The condition resolves itself into a liquid traversed byhorizontal currents from centre to circumference or vice versa, rotatedby a current passing through a circular conductor below it. 475 STANDARD ELECTRICAL DICTIONARY. Rotation of Liquids, Electro-magnetic. The rotation produced in a liquid carrying centripetal or centrifugalcurrents by an electromagnet. It is practically an intensification ofelectro-dynamic rotation. (See Rotation of Liquids, Electro-dynamic. ) Rubber. In a frictional electric machine the cushion of leather which is pressedagainst the plate as it rotates. S. (a) Symbol for second. (b) Symbol for space, or length; L is preferable. (c) Symbol for south-seeking pole of a magnet. Saddle Bracket. A bracket carried on the top of telegraph poles, carrying an insulatorfor the upper wire. Safety Device. (a) A device to prevent overheating of any portion of a circuit byexcess of current. It generally consists of a slip of fusible metalwhich if the current attains too much strength melts and opens thecircuit. To ensure its breaking a weight is sometimes suspended from thestrip. In one form an insulated German silver wire is wrapped around theend of the fusible strip a number of times and its end is connected toit. The other end of the German silver wire connects with the main lead, so that all the current goes through both in series. If the Germansilver wire becomes heated from excess of current the coil wrappedtightly around the end of the fusible strip melts it and opens thecircuit. (b) Lightning arresters, q. V. , may be cited under this heading. Synonyms--Automatic Cut Out--Safety Fuse, Plug, or Strip. Fig. 299. COCKBURN SAFETY FUSE. Safety Fuse. A strip of metal inserted so as to form part of a circuit and of suchsize that a smaller current [than] would heat the regular wire of thecircuit dangerously, so as to cause a conflagration for instance, wouldmelt the fuse and open the circuit. As it sometimes happens that asafety fuse melts without parting a weight is sometimes hung upon it, soas to break it as it softens. Salt. A salt is a chemical compound containing two atoms of two radicals, . Which saturate each other. One atom or radical is electro-positivereferred to the other, which is electro-negative. By electrolysis saltsare decomposed, the atoms or radicals separating and uniting to form newmolecules. 476 STANDARD ELECTRICAL DICTIONARY. Saturated. Adj. A liquid is saturated with a substance when it has dissolved all that itcan, while an excess is present in the liquid. It is possible, bydissolving some salts in hot water and allowing the solution to coolwithout access of air, to obtain a supersaturated solution. Onintroduction of a crystal of the salt, or often on mere access of air, the solution forms crystals and the liquid left is saturated. Saw, Electric. A platinum coated steel wire mounted and connected to be raised toincandescence for cutting purposes. Schweigger's Multiplier. An old term for the galvanometer as invented by Schweigger soon afterOerstedt's discovery. Scratch Brushes. Brushes for cleaning the surface of articles to be electroplated to givea good metallic surface suitable for deposition. They have often wireinstead of bristles. 477 STANDARD ELECTRICAL DICTIONARY. Fig. 300. WIRE GAUZE ELECTRIC SCREEN. Screen, Electric. A large plate or a hollow case or cage of conducting material connectedwith the earth, and used to protect any body placed within it fromelectrostatic influences. If within a hollow conducting sphere an electrified body is placed, theinner surface of the sphere will be charged with electricity of oppositekind to that of the sphere, and the outer surface with the same kind asthat of the sphere. Thus the sum of the electricities called into actionby induction is zero. The two inner charges are bound to each other. Theinduced charge on the outer surface of the sphere is all that has anyeffect on objects in the outer air. If the outer surface is connected to the earth it becomes discharged, and however highly electrified the body introduced into the sphere andthe inner surface of such sphere may be, they produce no externaleffects, as they are bound one to the other. If the sphere is connected to the earth and an unelectrified object isplaced within it, such object will be perfectly shielded from theeffects of an outer electrostatic field. Perforated tinfoil or wiregauze has just as good a result. A large plate of metal connected to theearth has the same effect. The screen whether plane or hollow simplyretains a bound charge due to the field of force, thereby neutralizingit, and the electricity of the opposite sign escapes to the earth. Thusa true shielding or screening effect is produced. In the cut an experiment is shown in which an electric screen is carriedby a Leyden jar. Pith balls are suspended outside and inside of it. Bythe approach of an electrified body the outer pith balls will diverge, while no effect is produced upon the inner ones. Secondary Actions. In electrolysis the direct products of the electrical decomposition arenot always obtained at the electrodes, but products due to theirreaction on the water and other chemicals may appear. These constitutesecondary actions. Thus if a solution of copper sulphate is electrolyzedwith platinum electrodes, metallic copper appears at one pole andsulphuric acid and oxygen gas at the other. But the products ofelectrolysis by the current are copper (Cu) and sulphion (SO4). Thelatter reacting on water sets free oxygen gas and forms sulphuric acid. The latter is a secondary action. Secondary Generator. (a) An alternating current converter generating a so-called secondarycurrent. (b) A secondary battery, q. V. , may be thus termed. Secondary, Movable. The term movable secondaries has been applied to rings, spheres anddiscs of conducting material, such as copper, whose behavior when nearthe pole of an electro-magnet traversed by an alternating current, havebeen studied by Elihu Thomson. Such masses are subjected to verypeculiar movements and mutual reactions. As the phenomena are due toinduced currents the above term has been applied to the masses in whichthe currents are induced. 478 STANDARD ELECTRICAL DICTIONARY. Secondary Plates, Colors of. In a secondary battery of the lead plate type, the color of the platesis a good indication of the condition of the battery. The negative plateshould be brown or deep-reddish, the other should be slate-colored. Secondary Poles. Poles sometimes found in magnets existing in positions intermediatebetween the end or true poles. Synonym--Consequent Poles. Seebeck Effect. The production of a current by heating the junction of two differentmetals forming part of a circuit, or the thermo-electric production ofcurrent, is stated as the Seebeck effect, having been discovered by thatinvestigator. Selenium. A non-metallic element. It is interesting electrically on account of thechanges its electric resistance undergoes when it is subjected to light. In one set of experiments it was found that diffused light caused theresistance to fall in the ratio of 11 to 9. Full sunlight reduced it toone-half. Of the spectrum colors red was most powerful and the ultra redregion still more strongly affected its resistance. The effect produced by exposure to light is instantaneous, but onremoval to the dark only slowly disappears. A vessel of hot water was found to have no effect, showing that shortether waves are essential to the effect. Selenium Cell. A selenium resistance box. Vitreous selenium is made by keeping ordinaryselenium for some hours at a temperature of about 220º C. (428º F. )after fusing. It is placed in an electric circuit as part of theconductor. Its resistance can then be determined. It decreases in sunlight to aboutone-half its resistance in the dark. The selenium cell is used in the Photophone, q. V. Otherwise it islittle more than a subject of experiment. Selenium Eye. A model eye in which selenium in circuit with a battery and galvanometertakes the place of the retina of the human eye. Self-repulsion. When a body is electrified each molecule repels its neighbor and thecondition in question is thus designated. An electrified soap-bubbleexpands in virtue of self-repulsion. Semi-conductors. Substances which conduct static electricity poorly, but quiteappreciably and beyond the extent of leakage. The following areexamples: Alcohol and ether, powdered glass, flowers of sulphur, drywood, paper, ice at 0º C. (32º F. ) 479 STANDARD ELECTRICAL DICTIONARY. Sensibility. The measure of the effect of a current upon a galvanometer, or anysimilar case. Sensitiveness, Angle of Maximum. Every galvanometer has its angle of maximum sensitiveness, which is theangle of deflection at which a small increment of current will producethe greatest deflection. For every tangent galvanometer 45° is the anglein question. In using a galvanometer for direct reading methods it is anobject to have it work at its angle of maximum sensitiveness. Separately Excited Dynamo. A dynamo-electric machine whose field magnet is excited from an outsidesource, which may be another dynamo or a battery. Alternating currentdynamos are often of this description. Separate Touch. In magnetism a method of inducing magnetism in a steel bar. The oppositepoles of two magnets are applied at the center of the bar to bemagnetized, but without touching each other, and are drawn apart to itsends. They are returned through the air and the process is repeated anumber of times and on both sides of the bar if necessary. Separation of Electricities. Under the double fluid theory of electricity the action ofelectrification in accumulating positive electricity in one conductorand negative on the other of the excited surfaces of two conductors. Separator. India rubber bands or other forms used in batteries to keep the platesfrom touching in the cell; especially applied to secondary batteries, where the plates are so near together as to require separators toprevent short circuiting. Fig. 301. SERIES CONNECTION. Series. (a) Arranged in succession as opposed to parallel. Thus if a set ofbattery jars are arranged with the zinc of one connected to the carbonof the next one for the entire number, it is said to be arranged inseries. When incandescent lamps are arranged in succession so that thecurrent goes through one after the other they are arranged in series. The opposite of parallel, q. V. , or multiple arc, q. V. ; it may be usedas a noun or as an adjective. (b) See Electro-Chemical Series; (c) Thermo-Electric Series (d) Electrostatic Series; (e) Electro-motive Series. Synonym--Cascade Connection (but little used. ) 480 STANDARD ELECTRICAL DICTIONARY. Series-multiple. Arrangement of electric apparatus, in which the parts are grouped insets in parallel and these sets are connected in series. It is used as anoun, as "arranged in series-multiple, " or as an adjective, as "aseries-multiple circuit or system. " Fig. 302. SERIES-MULTIPLE CONNECTION. Service Conductors. In electric distribution the equivalents of service pipes in thedistribution of gas; wires leading from the street mains to the houses, where current is to be supplied. Serving. The wrapping or winding of a cable composed of small size wire, laidclosely and smoothly with a tool called a serving mallet, or servingblock, or by machinery. It serves to protect the cable from wear. Shackle. In telegraph lines a swinging insulator bracket for use where wires makean angle with the pole. A journal box is attached to the pole, like halfof a gate hinge. To this a short iron arm is pivoted so as to be free toswing through a considerable angle. At its end an insulator is carriedto which the wire is attached. The shackle swings into line with thewire, or takes a position for two wires corresponding to the resultantof their directions of pull. Fig. 303. DOUBLE SHACKLE Shadow. Electric. A term applied to a phenomenon of high vacua. If an electric dischargeis maintained in a Crookes' tube the glass opposite the negativeelectrode tends to phosphoresce. A plate of aluminum, used also as thepositive electrode, protects the glass directly behind it so as toproduce the effect of a shadow. Synonym--Molecular Shadow. [Transcriber's note: The effect is due to the "shadowing" of theelectrons streaming past the plate. ] 481 STANDARD ELECTRICAL DICTIONARY. Sheath for Magnet Coils. In 1867 C. E. Varley proposed the use of a copper sheath surrounding amagnet core to diminish self-induction. It has since been used by Brushand others. Sometimes metallic foil is laid between the successive coilsof wire. Synonym--Mutual Induction Protector. Sheath for Transformers. A protective sheath of copper, interposed between the primary andsecondary circuits of an alternating current transformer. It isconnected to the earth. If the primary coil loses its insulation beforeit can leak to the secondary it is grounded. This protects the secondarycircuit from the high electro-motive force of the primary circuit. Shellac. A resin; produced as an exudation upon the branches of certain Asiatictrees, such as the banyan (Ficus religiosa). It is due to punctures inthe bark of the trees in question, which punctures are made by thefemale of the insect coccus ficus or c. Lacca. Commercial shellac contains about 90 per cent. Of resinous material, therest is made up of wax, gluten, coloring matter and other substances. Shellac is soluble in alcohol, and in aqueous solutions of ammoniumchloride, of borax and in strong ammonia solution. Long standing isrequired in the case of the last named solvent. Dilute hydrochloric andacetic acids dissolve it readily; nitric acid slowly; strong sulphuricacid is without action on it. Alkalies dissolve it. In electric work it is used as an insulator and dielectric. Itsalcoholic solution is used to varnish glass plates of influencemachines, for the coils of induction coils and similar purposes. Resistance in ohms per centimeter cube at 28° C. (82. 4 F. )--(Ayrton), 9. 0E15 Specific Inductive Capacity (Wüllner), 2. 95 to 3. 73 The same substance in less pure forms occurs in commerce, as stick lac, lump lac, seed lac, button lac. Shellac Varnish. Solution of shellac in alcohol; methylic alcohol (wood alcohol or woodnaphtha) is often used as solvent. Dr. Muirhead recommends button lac, dissolved in absolute alcohol, andthe top layers decanted. For highest insulation he dissolves the lac inordinary alcohol, precipitates by dropping into water, collects theprecipitate, dries and dissolves in absolute alcohol. Shielded. Adj. An electric measuring instrument of the galvanometer type is shieldedwhen it is so constructed that its indications are not seriouslyaffected by the presence of neighboring magnets or by fields of force. Shielding can be effected by using a very strong permanent magnet toproduce a field within which the magnetic needle moves and which reactsupon it, or by enclosing the instrument in a thick iron box. 482 STANDARD ELECTRICAL DICTIONARY. S. H. M. Symbol or abbreviation for "simple harmonic motion. " Shock, Break. A term in electro-therapeutics; the shock received when an electriccircuit, including the patient in series, is broken or opened. Synonym--Opening Shock. Shock, Electric. The effect upon the animal system of the discharge through it ofelectricity with high potential difference. Pain, nervous shock, violentmuscular contortions accompany it. Of currents, an alternating currentis reputed worse than a direct current; intermediate is the pulsatorycurrent. The voltage is the main element of shock, amperage has also some directinfluence. Shock, Static. A term in electro-therapeutics. The application of static dischargesfrom small condensers or Leyden jars to a patient who is insulated fromthe ground with one electrode applied to the conducting surface on whichhe rests, while the other, a spherical electrode, is brought near thebody so as to produce a disruptive or spark discharge. Short Circuit. A connection between two parts of a circuit, which connection is of lowresistance compared to the intercepted portion. The term is used also asa verb, as "to short circuit a lamp. " Fig. 304. DIAGRAM ILLUSTRATING SHORT CIRCUIT WORKING. Short Circuit Working. A method of working intermittently an electro-magnet so as to avoidsparking. It consists in providing a short circuit in parallel with themagnetic coils. This short circuit is of very low resistance. To throwthe magnet into action the short circuit is opened; to throw it out ofaction the short circuit is closed. The shunt or short circuit must beof negligibly small resistance and inductance. 483 STANDARD ELECTRICAL DICTIONARY. Shovel Electrodes. Large plate electrodes used in a medical bipolar bath. (See Bath, Bipolar. ) Shunt. In a current circuit a connection in parallel with a portion of thecircuit. Thus in a dynamo a special winding for the field may have itsends connected to the bushes, from which the regular external circuitalso starts. The field is then wound in shunt with the armature. In thecase of a galvanometer a resistance coil may be put in parallel with itto prevent too much current going through the galvanometer; thisconnection is a shunt. The word is used as a noun, as "a shunt, " or "a connection or apparatusin shunt with another, " and as an adjective, as "a shunt connection, " oras a verb, as "to shunt a battery. " Shunt Box. A resistance box designed for use as a galvanometer shunt. (See Shunt, Galvanometer. ) The box contains a series of resistance coils which canbe plugged in or out as required. Shunt, Electro-magnetic. In telegraphy a shunt for the receiving relay consisting of the coils ofan electro-magnet. It is placed in parallel with the relay. Its polesare permanently connected by an armature. Thus it has highself-induction. On opening and closing the circuit by the sending key, extra currentsare produced in the shunt. The connections are so arranged that onmaking the circuit the extra current goes through the relay in the samedirection as the principal current, while on breaking the circuit theinduced current goes in the opposite direction. Thus the extra currents accelerate the production and also the cessationof signalling currents, tending to facilitate the operations of sendingdespatches. Shunt, Galvanometer. A resistance placed in parallel with a galvanometer, so as to shortcircuit its coils and prevent enough current passing through it toinjure it. By knowing the resistance of the shunt and of thegalvanometer coils, the proportion of current affecting the galvanometeris known. This gives the requisite factor for calculation. (SeeMultiplying Power of Shunt. ) Shunt Ratio. The coefficient expressing the ratio existing between the current in ashunt and in the apparatus or conductor in parallel with it. (SeeMultiplying Power of/ Shunt. ) Shunt Winding. A dynamo or motor is shunt-wound when the field magnet winding is inshunt or in parallel with the winding of the armature. Shuttle Current. A current alternating in direction; an alternating current. 484 STANDARD ELECTRICAL DICTIONARY. Side-Flash. A bright flashing lateral discharge from a conductor conveying a currentdue to a static discharge. Sighted Position. In an absolute electrometer (see Electrometer, Absolute) the position ofthe balanced arm carrying the movable disc or plate, when the disc andguard plate are in one plane. The cross-hair on the lever-end is thenseen midway between two stops, or some other equivalent position isreached which is discerned by sighting through a magnifying glass ortelescope. Silver. A metal; one of the elements; symbol Ag. ; atomic weight, 108; valency, 1;equivalent, 108; specific gravity, 10. 5. It is a conductor of electricity. Relative resistance, annealed, 1. 0 Specific Resistance, annealed, at 0° C. (32° F. ) 1. 504 microhms. Resistance of a wire at 0° C. (32° F. ), Annealed. Hard Drawn. (a) 1 foot long, weighing 1 grain, . 2190 ohms . 2389 ohms. (b) 1 foot long, 1/1000 inch thick, 9. 048 " 9. 826 " (c) 1 meter long, weighing 1 gram, . 1527 " . 1662 " (d) 1 meter long, 1 millimeter thick, . 01916 " . 02080 " Resistance annealed of a 1-inch cube, at 0° C. (32°F. ) . 5921 microhms. Percentage increase in resistance per degree C. (1. 8 F. ) at about 20° C. (68° F. ), annealed, 0. 377 per cent. Electro-chemical equivalent, (Hydrogen = . 0105) . 1134 mgs. Silver Bath. A solution of a salt of silver for deposition in the electroplatingprocess. The following is a typical formula: Water, 10. 0 parts by weight. Potassium Cyanide, 5 " " Metallic Silver, 2. 5 " " The silver is first dissolved as nitrate and converted into cyanide andadded in that form, or for 2. 5 parts metallic silver we may read: Silver cyanide, 3 parts by weight. While many other formulas have been published the above isrepresentative of the majority. Other solvents for the silver thanpotassium cyanide have been suggested, such as sodium hyposulphite, butthe cyanide solution remains the standard. Silver Stripping Bath. Various baths are used to remove silver from old electroplated articles. Their composition depends upon the base on which the metal is deposited. Silvered iron articles are placed as anodes in a solution of 1 partpotassium cyanide in 20 parts of water. As kathode a silver anode or acopper one lightly oiled may be used. From the latter the silver easilyrubs off. For copper articles a mixture of fuming sulphuric acid andnitric acid (40º Beaumé) may be used. The presence of any water in thismixture will bring about the solution of the copper. Or fuming sulphuricacid may be heated to between 300º and 400º F. , some pinches of drypulverized potassium nitrate may be thrown in and the articles at oncedipped. These methods effect the solution of the silver, leaving thecopper unattacked. 485 STANDARD ELECTRICAL DICTIONARY. Simple Substitution. A method of obtaining a resistance equal to that of a standard. Thestandard is put in circuit with a galvanometer and the deflection isnoted. For the standard another wire is substituted and its lengthaltered until the same deflection is produced. The two resistances arethen evidently identical. The standard can be again substituted toconfirm the result. Sine Curve. If we imagine a point moved back and forth synchronously with apendulum, and if such point made a mark upon paper, it would trace thesame line over and over again. If now the paper were drawn steadilyalong at right angles to the line of motion of the point, then the pointwould trace upon it a line like the profile of a wave. Such line is asine curve. It derives its name from the following construction. Let astraight line be drawn, and laid off in fractions, such as degrees, ofthe perimeter of a circle of given diameter. Then on each division ofthe line let a perpendicular be erected equal in height to the sine ofthe angle of the circle corresponding to that division; then if theextremities of such lines be united by a curve such curve will be a sinecurve. In such a curve the abscissas are proportional to the times, while theordinates are proportional to the sines of angles, which angles arethemselves proportional to the times. The ordinates pass throughpositive and negative values alternately, while the abscissas are alwayspositive. Any number of sine curves can be constructed by varying the diameter ofthe original circle, or by giving to the abscissas a value which is amultiple of the true length of the divisions of circle. If the pendulummethod of construction were used this would be attained by giving agreater or less velocity to the paper as drawn under the pendulum. A species of equation for the curve is given as follows: y = sin( x ) In this x really indicates the arc whose length is x, and referenceshould be made to the value of the radius of the circle from which thecurve is described. It will also be noticed that the equation onlycovers the case in which the true divisions of the circle are laid offon the line. If a multiple of such divisions are used, say n times, or1-n times, then the equation should ready = n sin( x ) or y = sin( x ) / n Synonyms--Curve of Sines--Sinusoidal Curve--Harmonic Curve. 486 STANDARD ELECTRICAL DICTIONARY. Sine Law. The force acting on a body is directly proportional to the sine of theangle of deflection when-- I. The controlling force is constant in magnitude and direction; and II. The deflecting force, although variable in its direction in space, is fixed in direction relatively to the deflecting body. Single Fluid Theory. A theory of electricity. Electricity, as has been said, beingconveniently treated as a fluid or fluids, the single fluid theoryattributes electrical phenomena to the presence or absence of a singlefluid. The fluid repels itself but attracts matter; an excess createspositive, a deficiency, negative electrification; friction, contactaction or other generating cause altering the distribution createspotential difference or electrification. The assumed direction (seeDirection) of the current and of lines of force are based on the singlefluid theory. Like the double fluid theory, q. V. , it is merely aconvenience and not the expression of a truth. (See Fluid, Electric, andDouble Fluid Theory. ) Synonym--Franklin's Theory. Single Fluid Voltaic Cell. A galvanic couple using only a single fluid, such as the Smee or Voltacell. Simple Harmonic Motion. Motion of a point or body back and forth along a line; the motion of apendulum, as regards its successive swings back and forth, is an exampleof harmonic motion. Sinistrotorsal. Adj. The reverse of dextrotorsal, q. V. A helix with left-handed winding, thereverse of an ordinary screw, such as a wood-screw or corkscrew. Skin Effect. A current of very brief duration does not penetrate the mass of aconductor. Alternating currents for this reason are mainly conducted bythe outer layers of a conductor. The above is sometimes called the skineffect. Sled. A contact for electric cars of the conduit system. It is identical withthe plow, q. V. , but is drawn after the cars instead of being pushedalong with them. Slide Meter Bridge. A name for a Slide Bridge one meter long. There are also slide halfmeter and slide quarter meter bridges and others. (See Meter Bridge. ) S. N. Code. Abbreviation for single needle code, the telegraphic alphabet used withthe single needle system. Soaking-in-and-out. A term for the phenomena of the residual electrostatic charge; thegradual acquirement or loss by a condenser of a portion of itselectrostatic charge. 487 STANDARD ELECTRICAL DICTIONARY. Soldering, Electric. (a) Soldering in which the solder is melted by means of electricity;either current incandescence or the voltaic arc may be used. It isidentical in general with electric welding. (See Welding, Electric. ) (b) The deposition by electric plating of a metal over the ends of twoconductors held in contact. This secures them as if by soldering. It isused in connecting the carbon filament of an incandescent lamp with theplatinum wires that pass through the glass. Copper is the metal usuallydeposited. Solenoid. The ideal solenoid is a system of circular currents of uniformdirection, equal, parallel, of equal diameter of circle, and with theircenters lying on the same straight line, which line is perpendicular totheir planes. Fig. 305. EXPERIMENTAL SOLENOID. The simple solenoid as constructed of wire, is a helical coil, ofuniform diameter, so as to represent a cylinder. After completing thecoil one end of the wire is bent back and carried through the centre ofthe coil, bringing thus both ends out at the same end. The object ofdoing this is to cause this straight return member to neutralize thelongitudinal component of the helical turns. This it does approximatelyso as to cause the solenoid for its practical action to correspond withthe ideal solenoid. Instead of carrying one end of the wire through the centre of the coilas just described, both ends may be bent back and brought together atthe centre. A solenoid should always have this neutralization of the longitudinalcomponent of the helices provided for; otherwise it is not a truesolenoid. Solenoids are used in experiments to represent magnets and to study andillustrate their laws. When a current goes through them they acquirepolarity, attract iron, develop lines of force and act in general likemagnets. A solenoid is also defined as a coil of insulated wire whose length isnot small as compared with its diameter. 488 STANDARD ELECTRICAL DICTIONARY. Sonometer, Hughes'. A sound measurer; a modification of a portion of Hughes' inductionbalance, used for testing the delicacy of the ear or for determining therelative intensity of sounds. (See Hughes' Induction Balance. ) It is thearrangement of three coils, two mounted one at each of the ends of agraduated bar, and the third one between them and free to slide back andforth thereon. Sonorescence. The property of producing sounds under the influence of momentary lightradiations rapidly succeeding each other. It is the property utilized inthe photophone, q. V. Fig. 306. MORSE SOUNDER. Sounder. In telegraphy an instrument consisting of an electromagnet with armatureattached to an oscillating bar, the range of whose movements isrestricted by adjusting screws. The armature is drawn away from themagnet by a spring. When a current is sent through the magnet thearmature is drawn towards the poles and produces a sound as the barstrikes a striking piece or second adjusting screw. When the currentceases the bar and armature are drawn back, striking the first mentionedscrew with a distinct sound, the back stroke. The sounder is used to receive Morse and analogous character messages. The forward strokes correspond to the beginnings of the dots or dashesof the code, the back strokes to beginnings of the intervals. Thedistinction between dots and dashes is made by observing the intervalbetween forward and back stroke. Various devices are used to increase the sound. Sometimes a resonancebox is used on which the sounder is mounted. In practice sounders are generally placed on local circuits and areactuated by relays. 489 STANDARD ELECTRICAL DICTIONARY. Sound Reading. The art or method of receiving telegraph messages by ear. It is nowuniversally used by all expert Morse operators. It can only be appliedto telegraph systems producing audible sounds; in some cases, as inneedle telegraphy, it may be quite inapplicable. Space, Clearance. The space between faces of the pole pieces and the surface of thearmature in a dynamo. It is really the air gap, but in calculatingdynamo dimensions the thickness of the insulated copper wire windings ofthe commutator are counted in as part of the air gap, because copper isalmost the same as air in impermeability. Clearance space is amechanical factor; the air gap is an electric or magnetic factor. Synonym--Inter-air Space. Space, Crookes' Dark. In an exhausted tube, through which an electric discharge is caused topass, the space surrounding the negative electrode of the tube. Thisspace is free from any luminous effect, and by contrast with the lightof the discharge appears dark. The vacuum may be made so high that thedark space fills the whole space between the electrodes. It is less fora less vacuum and varies for other factors, such as the temperature ofthe negative electrode from which it originates, the kind of residualgas present, and the quality of the spark. Space, Faraday's Dark. The space in an exhausted tube between the luminous glows about the twoelectrodes. Space, Interferric. A term for the air-gap in a magnetic circuit. It is etymologically morecorrect than air-gap, for the latter is often two-thirds or more filledwith the insulating material and copper wire of the armature windings. (See Space, Clearance. ) Spark Arrester. A screen of wire netting fitting around the carbons of an arc lamp abovethe globe to prevent the escape of sparks from the carbons. Spark Coil. A coil for producing a spark from a source of comparatively lowelectro-motive force. It consists of insulated wire wound round a coreof soft iron, best a bundle of short pieces of wire. Such a coil may beeight inches long and three inches thick, and made of No. 18-20 copperwire, with a core one inch in diameter. On connecting a batterytherewith and opening or closing the circuit, a spark is produced byself-induction, q. V. It is used for lighting gas. 490 STANDARD ELECTRICAL DICTIONARY. Spark, Duration of Electric. Wheatstone determined the duration of the spark given by a Leyden jar as1/24000 second. Feddersen by interposing a tube of water 9 millimeters(. 36 inch) long in its path found that it lasted 14/10000 second, andwith one 180 millimeters (7. 2 inches) long, 188/10000 second. Lucas andCazin for a 5 millimeter (. 2 inch) spark, with different numbers ofLeyden jars, found the following:Number of jars. Duration of Spark. 2 . 000026 second 4 . 000041 " 6 . 000045 " 8 . 000047 " The duration increases with the striking distance, and is independent ofthe diameter of the balls between which it is produced. Spark Gap. The space left between the ends of an electric resonator (see Resonator, Electric) across which the spark springs. Its size may be adjustable bya screw, something like the arrangement of screw calipers. Sparking. In dynamo-electric machines, the production of sparks at the commutatorbetween the brushes and commutator sections. The sparks are often truevoltaic arcs, and in all cases are injurious if in any quantity, wearingout the commutator and brushes. Sparking, Line or Points of Least. In a dynamo or electric motor the diameter of the commutatordetermining, or the points on the commutator marking the position of thebrushes where the sparking is a minimum. Field magnets powerful inproportion to the armature are a preventative cause. The direction ofthe line fixes the angle of lead to be given to the brushes. Sparking, Resistance to. The resistance to disruptive discharge through its substance offered bya dielectric or insulator. It does not depend on its insulatingqualities, but on its rigidity and strength. Spark, Length of. The length of the spark accompanying the disruptive discharge is countedas the distance from one electrode to the other in a straight line. Itis longer for an increased potential difference between the twoelectrodes. If the gas or air between the electrodes is exhausted thelength increases, until the vacuum becomes too high, when the lengthbegins to decrease, and for a perfect vacuum no spark however small canbe produced. The shape of the conductor which is discharged, thematerial of the electrodes, and the direction of the current are allfactors affecting the length of spark producible. 491 STANDARD ELECTRICAL DICTIONARY. Spark Tube. A tube used as a gauge or test to determine when the exhaustion of thevacuum chamber or bulb of an incandescent lamp is sufficiently high. The interior of the tube is connected with the interior of the bulb orchamber of the lamps in process of exhaustion, and hence shares theirdegree of exhaustion. From time to time connections with an inductioncoil are made. When the exhaustion is carried far enough no dischargewill take place through the vacuum. As long as the tube acts like aGeissler tube the exhaustion is not considered perfect. Specific Heat of Electricity. The heat absorbed or given out by a fluid in passing from onetemperature to another depends on its specific heat. In the Peltier andthe Thomson effects. Q. V. , the electric current acts as the producer ofa change of temperature, either an increase or decrease as the case maybe. This suggests an absorption of and giving out of heat which amountof heat corresponding to a current of known amount is determinable, andmay be referred to any unit of quantity such as the coulomb. This orsome equivalent definite quantity of heat it has been proposed (SirWilliam Thomson) to term the Specific Heat of Electricity. Spent Acid. Acid which has become exhausted. In a battery the acid becomes spentfrom combination with zinc. It also loses its depolarizing power, if itis a chromic acid solution or of that type, and then may be said to bespent. Spent Liquor. The liquor of a plating bath which has become exhausted from use, themetal it contained being all or partly deposited. Sphygmograph, Electric. An electric apparatus for recording the beat of the pulse, both asregards its rate and strength. Sphygmophone. An apparatus for examination of the pulse by the microphone andtelephone. Spiders. Core-discs of a dynamo or motor armature are sometimes perforated with alarge central aperture, are fastened together with insulated bolts, andthe whole mass is secured to the shaft by three- or four-armed spiders. These are like rimless wheels, the ends of their arms being secured tothe hollow cylinder constituting the armature core, and a centralaperture in their hub receiving the shaft. 492 STANDARD ELECTRICAL DICTIONARY. Spiral. This term is sometimes used instead of coil, as the primary spiral orsecondary spiral of an induction coil or transformer. Spiral Winding. The winding used on ring armatures. This may diagrammatically berepresented by a spiral carried around the ring shaped core. With twofield poles it gives two collecting points, positive and negative, withfour field poles it gives four collecting points, alternately positiveand negative. Splice Box. A box in which the splices in underground cables and electric lines arecontained. The splicing is generally done in the boxes with the cablesin place. They may be two-way for straight lines, or be four-way for twoside or lateral connections. Spluttering. A term applied to a sound sometimes produced in a voltaic arc, perhapscaused by impure or insufficiently baked electrodes. (Elihu Thomson. ) Spring Control. Control of or giving the restitutive force to the needle of agalvanometer, core of a solenoid ammeter or moving part of any similarinstrument by a spring. As an example see Ammeter, Ayrton's. Fig. 307. SPRING JACKS. Spring Jack. An arrangement for effecting, at one insertion of a species of plug, theopening or breaking of a circuit and for the simultaneous connection tothe terminals formed by the breaking of two terminals of another systemor loop. Thus let a line include in its circuit two springs pressingagainst each other, thereby completing the circuit. If a plug or wedgeof insulating material were inserted between the springs so as to pressthem apart it would break the circuit and the whole would constitute aspring jack cut-out. If each side of the plug had a strip of brass orcopper attached to it, and if the ends of another circuit were connectedto these strips, then the insertion of the plug would throw the new lineinto the circuit of the other line. 493 STANDARD ELECTRICAL DICTIONARY. Spring Jack Cut-out. A cut-out, of the general construction of a spring jack, q. V. , exceptthat a simple insulating plug or wedge is used in place of themetal-faced wedge with its connections of the regular spring jack. Theinsertion of an insulating wedge opens the circuit, which on its removalis closed. The regular spring jack wedge will operate in the same way, if its connections are kept open. Spurious Voltage. The voltage in excess of that developed by a secondary battery which isrequired in the charging process. It is about . 25 volt. Square Wire. Wire whose cross-section is a square. It has been used of iron forbuilding up the cores of armatures for dynamos or motors, for which itis peculiarly suitable, and also of copper as a winding for armatures. Staggering. Adj. When the brushes of a dynamo are set, one a little in advance of theother on the surface of the commutator, they are said to be setstaggering. It is used to get over a break in the armature circuit. State, Electrotonic. A term expressing an abandoned theory. Faraday at one time proposed thetheory that a wire had to be in the electrotonic state to produceelectro-motive force by movement through an electric field. Any suchidea was ultimately abandoned by Faraday. Static Breeze. The electric breeze obtained by the silent discharge of high tensionelectricity. Static Electricity. Electricity at rest or not in the current form ordinarily speaking. Theterm is not very definite and at any rate only expresses a difference indegree, not in kind. The recognition of the difference in degree has nowto a great extent also disappeared. Station, Central. The building or place in which are placed electrical apparatus, steamengines and plant supplying a district with electric energy. Station, Distant. The place at the further end of a telegraph line, as referred to thehome station. Station, Home. The end of a telegraph line where the operators using the expression areworking. 494 STANDARD ELECTRICAL DICTIONARY. Station, Transforming. In alternating current distribution, a building or place where a numberof transformers are worked, so that low potential or secondary circuitsare distributed therefrom. Steel. A compound of iron with carbon. The carbon may range from a fewhundredths of one per cent. Up to two per cent. For magnets, tool steeldrawn to a straw color or a little lower is good. All shaping and filingshould be done before magnetization. Steeling. The deposition of iron on copper plates by electrolysis. Inelectrotyping a thin deposit of iron is thus given the relief platesbefore printing from them. The deposit is very hard and exceedinglythin, so that it does not interfere with the perfection of theimpression in the printing process. As the iron becomes worn it can bedissolved off with hydrochloric acid, which does not dissolve thecopper, and a new deposit can be given it. Thus the plate may last foran indefinite number of impressions. The iron bath may be prepared by immersing in a solution of ammoniumchloride, two plates of iron, connected as anode and kathode in acircuit. One plate dissolves while hydrogen is given off from the other. The solution thus produced is used for a bath. The hardness of the deposit, which is really pure iron, gives the nameof "steeling. " Synonym--Acierage. St. Elmo's Fire. Luminous static discharge effects sometimes seen on objects elevated inthe air. They are especially noticed on ships' masts. The sailors termthem corpusants (holy bodies). They resemble tongues or globes of fire. Step-by-step Telegraphy. A system of telegraphy in which in the receiving instrument a hand ismade to move step-by-step, with an escape movement around a dial. Foreach step there is a letter and the hand is made to stop at one or theother letter until the message is spelled out. (See Dial Telegraph. ) Step-down. Adj. A qualification applied to a converter or transformer in the alternatingcurrent distribution, indicating that it lowers potential difference andincreases current from the secondary. Step-up. Adj. The reverse of step-down; a qualification of a transformer or converterindicating that it raises the potential and decreases the current in thesecondary. Sticking. The adherence, after the current is cut off, of the armature to thepoles of a magnet. In telegraphy it is a cause of annoyance andobstructs the working. It may, in telegraphy, be due to too weak aspring for drawing back the armature, or to imperfect breaking of thecontact by the despatcher's key or by the receiver's relay. 495 STANDARD ELECTRICAL DICTIONARY. Stopping Off. In electroplating the prevention of deposition of the plating metal onany desired portions of the object. It is effected by varnishing theplaces where no coating is desired. An article can be plated withsilver, stopped off in any desired design, and the unvarnished portionsmay then be plated with gold in another bath. Various effects can beproduced by such means. Storage Capacity. A term for the ampere-hours of electricity, which can be taken incurrent form from a storage battery. Storage of Electricity. Properly speaking electricity can only be stored statically or in staticcondensers, such as Leyden jars. The term has been popularly applied tothe charging of secondary or storage batteries, in which there is reallyno such thing as a storage of electricity, but only a decomposition andopposite combination brought about, which leave the battery in acondition to give a current. Storms, Electric. Wide-spread magnetic and electric disturbances, involving thedisturbance of the magnetic elements and other similar phenomena. (SeeMagnetic Storms. ) Strain. The condition of a body when subjected to a stress. Various consequencesmay ensue from strain in the way of disturbance of electric and otherqualities of the body strained. Stratification Tube. A Geissler tube, q. V. , for showing the stratification of the electricdischarge through a high vacuum. The stratifications are greatly intensified by the presence of a littlevapor of turpentine, alcohol, bisulphide of carbon and other substances. Stray Field. In a dynamo or motor the portion of the field whose lines of force arenot cut by the armature windings. Stray Power. The proportion of the energy wasted in driving a dynamo, lost throughfriction and other hurtful resistances. Streamlets, Current. A conception bearing the same relation to an electric current that linesof force do to a field of force; elementary currents. If evenlydistributed the current is of uniform density; if unevenly distributed, as in alternating currents, the current density varies in differentparts of the cross section of the conductor. This evenness or unevennessmay be referred to the number of streamlets per unit of area ofcross-section. [Transcriber's note: Streamlets per unit of area is redundant withcurrent density. ] Stress. Force exercised upon a solid tending to distort it, or to produce astrain. 496 STANDARD ELECTRICAL DICTIONARY. Stress, Dielectric. The condition of a dielectric when maintaining a charge; its twoextremities are in opposite states of polarity, or are under permanentpotential difference. As the two opposite polarities tend to unite acondition of stress is implied in the medium which separates them. Stress, Electro-magnetic. The stress produced upon transparent substances in an electro-magneticfield of force. It is shown in the modified optical properties of glassand similar substances placed between the poles of a strongelectro-magnet. Stress, Electrostatic. The stress produced upon substances in an electrostatic field of force;the exact analogue of electro-magnetic stress, and affecting transparentsubstances in the same general way. Striae, Electric. In Geissler tubes the light produced by the electric discharge is filledwith striae, bright bands alternating with dark spaces; these may betermed electric striae. Striking Distance. The distance that separates two conductors charged with electricity ofdifferent potential, when a spark starts between them. Striking Solution. In silver-plating a bath composed of a weak solution of silvercyanide-with a large proportion of free potassium cyanide. It is usedwith a strong current and a large silver anode. This gives aninstantaneous deposition of metallic silver over the surface of thearticle which goes to insure a perfect coating in the silver bathproper. After a few seconds in the striking solution, the article is atonce removed to the plating bath. Stripping. The removal of electroplating from an object. It may be effected inseveral ways. An object whose plating is to be removed is placed in aplating bath of the solution of the metal with which it is coated. It isconnected as the anode to the positive plate of the battery orcorresponding terminal of the generator. A kathode connected to theother terminal being placed in the bath, the coating is dissolved byelectrolytic action. Sometimes simple treatment with acid is employed. Different stripping baths are described under the heads of the differentmetals. S. U. Symbol or abbreviation for Siemens' Unit of Resistance. (See Resistance, Siemens' Unit of. ) Sub-branch. A branch or lead of wire taken from a branch lead: a term used inelectric distribution. Sub-main. In electric distribution a conductor connected directly to a main; abranch. 497 STANDARD ELECTRICAL DICTIONARY. Subway, Electric. A subterranean system of conduits for electric cables. As generallyconstructed in this country it includes manholes, q. V. , at the streetcorners connected by ducts or pipes. These pipes are large enough tohold a cable. To introduce a cable into a duct, which latter may be twoor three inches in diameter, and from two hundred to six or sevenhundred feet long, a wire or rope is first passed through the duct. Thisis done by a set of short wooden rods with screws at the end so as to bescrewed together. Each rod must be shorter than the diameter of themanhole. A rod is thrust in, another is screwed to it and thrust in, andthus a set of rods is made to extend as far as desired. In pulling themout a rope is attached and drawn through. This rope or a larger one isused in drawing the cable through the duct. A windlass is employed todraw the rope with cable attached through the ducts. Sulphating. In storage battery cells, the formation of a hard white basic leadsulphate, Pb2 S05. Its formation is due to over-exhaustion of the cells. As long as the voltage is not allowed to fall below 1. 90 volts per celllittle of it forms. As it accumulates it is apt to drop off the plateand fall to the bottom, thus weakening the plate possibly, and deprivingit of active material, and clogging up the cell. If it carries a film ofmetallic lead with it, there is danger of short circuiting the cell. The presence of some sodium sulphate in the solution is said to tend toprevent sulphating, or to diminish it. Sulphur Dioxide. A compound gas, S O2; composed of Sulphur, 32 Oxygen, 32 Molecular weight, 64 Specific gravity, 2. 21. It is a dielectric of about the same resistance as air. Its specificinductive capacity at atmospheric pressure is: 1. 0037 (Ayrton). Synonyms--Sulphurous Acid--Sulphurous Acid Gas. Sunstroke, Electric. Exposure to the arc light sometimes produces the effects observed incases of sunstroke. It is said that, in the case of workmen at electricfurnaces, these effects are very noticeable. (See Prostration, Electric. ) [Transcriber's note: Effects are due to ultraviolet light. ] Supersaturated. Adj. A liquid is supersaturated when it has dissolved a substance at atemperature favorable to its solubility and its temperature has beenallowed to change, the liquid being kept free from agitation or accessof air, provided crystallization or precipitation has not taken place. It expresses the state of a liquid when it holds in solution more thanthe normal quantity of any substance soluble in it. Surface. A galvanic battery is arranged in surface when all the positive platesare connected together and all the negative plates are also connected. This makes it equivalent to one large cell, the surface of whose plateswould be equal to the aggregate surface of the plates of the battery. Itis also used as an adjective, as "a surface arrangement of battery. " 498 STANDARD ELECTRICAL DICTIONARY. Surface Density. The relative quantity of an electric charge upon a surface. Surface, Equipotential. A surface over all of which the potential is the same. In a generalsense equipotential surfaces are given by planes or surfaces which cutlines of force at right angles thereto, or which are normal to lines offorce. The conception applies to electrostatic and electro-magneticfields of force, and for current conductors the planes normal to thedirection of the current are equipotential surfaces. The contour of an equipotential surface of a field of force which isdrawn or represented by delineations of its lines of force can beobtained by drawing a line normal thereto. This line will ordinarily bemore or less curved, and will be a locus of identical potentials. An electric equipotential surface may be described as electro-static, electro- magnetic, or magnetic; or may be an equipotential surface of acurrent conductor. Besides these there are mechanical and physicalequipotential surfaces, such as those of gravitation. Surface Leakage. Leakage of current from one part of an insulating material to another bythe film of moisture or dirt on the surface. Suspension. This term is applied to methods of supporting galvanometer needles, balance beams, magnetic compass needles and similar objects which mustbe free to rotate. (See Suspension, Bifilar--Fibre and SpringSuspension--Fibre Suspension--Knife Edge Suspension--PivotSuspension--Suspension, Torsion. ) 308. DIAGRAM OF BIFILAR SUSPENSION. Suspension, Bifilar. Suspension by two vertical parallel fibres, as of a galvanometer needle. The restitution force is gravity, the torsion being comparatively slightand negligible. Leaving torsion out of account the restitution force is(a) proportional to the distance between the threads;. (b) inverselyproportional to their length; (c) proportional to weight of the needleor other object suspended; (d) proportional to the angle ofdisplacement. 499 STANDARD ELECTRICAL DICTIONARY. Assume two masses A and B at the end of a weightless rod, suspended bythe parallel cords a A, b B. Let the rod be rotated through an angletheta. Consider the cord a A. Its lower end is swung through the angletheta, as referred to the center O; the cord is deflected from thevertical by an angle psi, such that a A tang(psi)= O A 2 sin (theta/2). The component of gravitation tending to restore A to A, acting towards Ais equal to m g tan(psi). Its moment around O is equal to (m g tan(psi))* (O A cos(theta/2). The whole moment of the couple is 2 m g tan(psi). 0 A. Cos(theta/2) = 2 m g (O A2/ a A) 2 sin(theta/2). Cos(theta/2) =2mgl(OA2/aA) sin(theta). The moment of the restoring force is thusproportional to the sine of the angle of deflection, and theoscillations of such a system are approximately simple harmonic. (Daniell. ) If the twisting is carried so far as to cause the threads to cross andcome in contact with each other the suspension ceases to be a bifilarsuspension, but assumes the nature of a torsional suspension. [Transcriber's note: This is the image of the first paragraph. ] Swaging, Electric. Mechanical swaging in which the objects to be swaged are heated by anelectric current as in electric welding. S. W. G. Abbreviation for Standard Wire Gauge. Fig. 309. SIMPLE SWITCH. Switch. A device for opening and closing an electric circuit. A simple type is the ordinary telegrapher's switch. A bar of metal ismounted horizontally by a pivot at one end, so as to be free to rotatethrough an arc of a circle. In one position its free end rests upon astud of metal. One terminal of a circuit is attached to its journal, theother to the stud. Resting on the stud it closes the circuit, in otherpositions it opens the circuit. 500 STANDARD ELECTRICAL DICTIONARY. Switch, Automatic. A switch opened and closed by the electric current. It is used forlighting distant incandescent lamps. It includes one or twoelectro-magnets operated by two push buttons. In the usual arrangementone button is black and the other white, for extinguishing and lightingrespectively. When the white button is pushed it causes a current topass through one of the electro-magnets. This attracts its armature, thereby making a contact and throwing the lamps into the lightingcircuit. Then they remain lighted until the black button is pressed. This excites the other magnet, which attracts its armature, breaks thecontact and extinguishes the lights. The object of the automatic switch is to enable distant lamps to belighted without the necessity of carrying the electric leads or wires tothe place whence the lighting is to be done. A very small wire willcarry enough current to operate the magnets, and open circuit batteries, such as Leclanché batteries, may be used as the source of current forthe switch, but generally the lighting current is used for the purpose. A single magnet may do the work. When the lighting button is pressed themagnet is excited, attracts its armature and holds it attracted, untilby pressing the black button the current is turned off from it. In thiscase the lighting current is used to excite the magnet. Switch Board. A board or tablet to which wires are led connecting with cross bars orother switching devices, so as to enable connections among themselves orwith other circuits to be made. Switch, Circuit Changing. A switch whose arm in its swing breaks one contact and swinging overmakes another. It is employed to change the connections of circuits fromone dynamo to another. Synonyms--Changing Switch--Changing Over Switch. Switch, Double Break. A form of switch in which double contact pieces are provided to give abetter contact. One form consists of a hinged bar whose end swings downbetween two pairs of springs. Both pairs are connected to one terminal, and the bar to the other terminal of a circuit. Switch, Double Pole. A heavy switch for central station work, that connects and disconnectstwo leads simultaneously. Switch, Feeder. A heavy switch, often of double contact type, for connecting anddisconnecting feeders from bus bars in central stations. 501 STANDARD ELECTRICAL DICTIONARY. Switch, Knife. A switch whose movable arm is a narrow, deep bar of copper or brass, andwhich in making contact is forced in edgeways between two springsconnected to one terminal. The bar is connected to the other terminal. Synonyms--Knife Break Switch--Knife Edge Switch. Switch, Multiple. A switch which in the swing of its bar connects one by one with a numberof contacts so that ultimately the end of its bar is in contact with allat once. It is used to throw lights in and out in succession, and itcan, if the multiple contacts connect with resistances, make themoperate as a rheostat. Switch, Pole Changing. A switch for changing the direction of the current in a circuit. Switch, Reversing. A switch, often of the plug type (see Plug Switch) for changing thedirection of current passing through a galvanometer. Switch, Snap. A switch constructed to give a quick, sharp break. It has a spiralspring interposed between the handle and arm. As the handle is drawnback to open it the spring is first extended, the bar being held by thefriction of the contacts, until the spring suddenly jerks it up, thusbreaking the contact. Switch, Storage Battery Changing. A switch for changing storage battery connections from series tomultiple and back again. Switch, Three Way. A switch, so constructed that by turning its handle connection can bemade from one lead to either of two other leads, and also so thatconnection can be completely cut off. Sympathetic Vibration. The establishment of periodic movement in one body by impulses of thesame period communicated to it from another body in motion. Thus if twotuning forks are of the same pitch and one is sounded the other willbegin to sound by sympathy, the sound waves communicating the necessaryperiodic impulses to it. Sympathetic vibrations are utilized in harmonic telegraphy. (SeeHarmonic Receiver--Telegraph, Harmonic. ) T. Symbol of time. Tailings. (a) In high speed transmission of telegraph signals by the automaticsystem, the definiteness of the signal marks is sometimes interferedwith by retardation. Wrong marks are thus produced called tailings. (b) The prolongation of the current at the distant receiving station ofa telegraph line due to the discharge of the line and to self-induction. Synonyms--Tailing--Tailing Current. 502 STANDARD ELECTRICAL DICTIONARY. Tamidine. Reduced nitro-cellulose. Nitro-cellulose is dissolved in a propersolvent and is obtained by evaporation as a translucent solid mass. Byammonium sulphide or other reagent it is reduced so as to be virtuallycellulose. It is cut into shape for filaments of incandescent lamps, which shapes are carbonized and flashed. Tangent Law. In a galvanometer the tangents of the angles of deflection of the needleare proportional to the deflecting force-- I. When the controlling force is unaltered in absolute magnitude anddirection by the motion of the needle. II. When the deflecting force acts at right angles always to thecontrolling force. These conditions are usually secured by having the actuating coilthrough which the current passes flat and of large diameter compared tothe length of the needle; by using the uniform field of the earth as thecontrol; by having a short needle; by placing the coil with its plane inthe magnetic meridian. For best proportions of tangent galvanometer coils see Bobbins. Fig. 310. GRAPHIC CONSTRUCTION OF TANGENT SCALE. Tangent Scale. An arc of a circle in which the number of graduations in any arcstarting from zero are proportional to the tangent of the anglesubtended by such arc. The system is for use with tangent galvanometers. Thus if for 45° a value of 100 is taken and marked on the scale then forthe arc 26° 33' + a value of 50 should be marked on the scale becausesuch are the relative values of the tangents. Thus the scale instead of being divided into degrees is divided intoarcs of varying length, growing shorter as they are more distant fromthe zero point, of such length that the first division being subtendedby a tangent of length 1, the first and second divisions added or takentogether as one arc are subtended by a tangent of length 2, and so on. In the cut a simple method of graphically laying out a tangent scale isshown. In it C is the centre of the arc, and H the radius running to thezero of the instrument. From C a circle is described and on H a verticalline tangent to the arc is erected. Taking any part of the tangent, asthe length shown ending at D, it is divided into any number of equalparts. Radii of the circle are now drawn whose prolongations passthrough the divisions on the tangent. These radii, where they intersectthe arc of the circle, determine equal divisions of the tangent scale, which, as is evident from the construction, are unequal angulardivisions of the arc. 503 STANDARD ELECTRICAL DICTIONARY. Tanning, Electric. The tanning of hides in the manufacture of leather by the aid ofelectrolysis. A current of electricity is maintained through the tanningvats in which regular tanning liquor is contained. Very extraordinaryclaims are made for the saving of time in the tanning process. What isordinarily a process of several months, and sometimes of a year, is saidto be reduced to one occupying a few days only. The action ofelectrolysis is the one relied on to explain the results. Tapper. The key used in single needle telegraph transmitters. It comprises twoflat springs L, E, each with a handle, normally pressed upward againstone contact bar Z, and when pressed down by the operator making contactagainst a lower bar C when messages are to be transmitted. A doubletapper, such as shown, is used for each instrument. Synonyms--Double Tapper Key--Pedal Key. Fig. 311. TAPPER. Target, Electric. A target registering or indicating electrically upon an annunciator thepoint of impact of each bullet. Taste, Galvanic. The effect produced upon the gustatory nerves by the passage of anelectric current, or by the maintenance of potential difference betweentwo portions of the tongue. It is very simply produced by placing asilver coin above, and a piece of zinc below the tongue, or the reverse, and touching their edges. A sour, peculiar taste is at once perceived. It cannot be due to any measurable quantity of current or ofelectrolytic decomposition, because the couple can do little more thanestablish a potential difference. With a strong current the tastebecomes too strong for comfort, and if on a telegraph line the extracurrents produced by the signaling make the operation of tasting thecurrent a very unpleasant one. It is said that messages have beenreceived in this way, the receiver placing one terminal of the line onhis tongue, and a terminal attached to a grounded wire below it, andthen receiving the Morse characters by taste. 504 STANDARD ELECTRICAL DICTIONARY. Teazer. Originally a fine wire coil wound on the field magnets of a dynamo inshunt with the regular winding to maintain the magnetism. It wasoriginally used in electroplating machines to prevent inversion of themagnetism, but has since developed into a component part of the windingof the compound dynamo. (See Dynamo, Compound. ) Tee, Lead. A lead pipe of T shape used for connecting branches to electric cables. The tee is soldered by wiped joints to the lead sheathings of the cableand branches after the wires have been connected, and the junctionscoated with insulating tape or cement, or both. It is sometimes made in two halves, and is known as a split tee. Tel-autograph. A telegraph for reproducing the hand-writing of the sender at thereceiving end of the line. To save time a special spelling is sometimesused. Teleautograph. The special spelling used with the Tel-Autograph telegraph. Tele-barometer, Electric. A barometer with electric attachment for indicating or recording at adistance the barometric readings. Telegraph, ABC. This term is applied to alphabet telegraphs indicating the message bythe movements of a pointer on a dial marked with the characters to besent. In England the Wheatstone ABC system is much employed. Telegraph, Automatic. A telegraph system based on the operation of the transmitting instrumentby a perforated strip of paper drawn through it. The perforations madeby an apparatus termed a perforator, are so arranged as to givetelegraphic characters of the Morse or International Code in thetransmitting instrument. (See Perforator. ) Bain in the year 1846 was theoriginator of the system. He punched a fillet of paper with dots anddashes, and drew it between two terminals of the line, thus sending overthe line a corresponding series of short and long currents which werereceived by his chemical receiver. (See Chemical Receiver. ) The methodwas not successful. Its modern development, the Wheatstone AutomaticTelegraph, is highly so. The perforated paper by its perforationscontrols the reciprocating movement of two rods, which pass through eachhole in two rows, corresponding to the two rods respectively as theholes come opposite to the ends of the rods. The rods are keptconstantly moving up and down. If unperforated paper is above them theirupward motion is limited. This gives three positions for the rods, (a)both down, (b) one up and the other down, (c) both up. These positionsof the rods work a pole changing key by which dots, spaces, and dashesare transmitted to the receiving instrument, which is an exceedinglydelicate ink-printer. The latter can have its speed adjusted to receivefrom 200 to 450 words per minute. 505 STANDARD ELECTRICAL DICTIONARY. Telegraph, Dial. A telegraph in which as receiver a dial instrument is used. A pointer orindex hand moves around a dial. The dial is marked with letters of thealphabet. The movements of the pointer are controlled by thetransmitting operator at a distant station. He by the same actions movesa pointer on a duplicate instrument before him and the two aresynchronized to give identical indications. Thus a message is spelledout letter by letter on both dials simultaneously. The motions of theindex are generally produced by what is virtually a recoil escapement. The scape wheel is carried by the axle of the index, and a pallet oranchor is vibrated by an electro-magnet whose armature is attached tothe stem of the pallet. As the pallet is vibrated it turns the wheel andindex one tooth for each single movement. There are as many teeth in thewheel as there are characters on the dial. The two instruments being induplicate and synchronized, the pallets move exactly in unison, so thatidentical readings of the dials are given. The pallets may be moved byany kind of make and break mechanism, such as an ordinary telegraph key. The index moves by steps or jerks, so that the system is sometimescalled step-by-step telegraphy. Fig. 312. DIAL TELEGRAPH. In the cut the make and break transmitter is shown at v v, with itshandle and contacts g and t. This mechanism sends impulses of current byF and Z to the receiving magnet l. This attracts and releases itsarmature K from contact into the position indicated by the dotted lines. This works the rocker n on the pin o, and actuates the double or anchorpawl s r, which turns the pallet or scrape wheel m. The system is dropping into disuse, being supplanted by the telephone. Synonym--Step-by-step Telegraph. 506 STANDARD ELECTRICAL DICTIONARY. Telegraph, Double Needle. A telegraph system in which the message is read by the motions of twovertical needles on the face of the instrument in front of the receivingoperator. An identical instrument faces the transmitting operator. Bytwo handles, one for each hand, the needles are caused by electricimpulses to swing to right and to left so as to give a telegraphic code. It has been generally superseded by the single needle telegraph. Telegraph, Duplex. A telegraph capable of transmitting simultaneously two messages over onewire. The methods of effecting it are distinct from those of multiplextelegraphy. This term is used as a distinction from diode multiplextelegraphy, in which the work is done on other principles. There are twosystems of duplex telegraphy, the differential and the bridge systems. Telegraph, Duplex Bridge. A system of duplex telegraphy employing the principle of the Wheatstonebridge. The other or differential system depends on equality ordifference of currents; the bridge method on equality or difference ofpotentials. The cut shows the system known as Steam's Plan. At the ends of the line wire are two cross connections like duplicategalvanometer connections in a Wheatstone bridge, each including areceiving relay. The rest of the connections are self-explanatory. When A depresses his key the current splits at the point indicating thebeginning of the bridge. One portion goes through the line to B and toearth, the other goes to earth at A through the rheostats indicated bythe corrugated lines. On reaching B's end the current divides at the cross-connection and partgoes through the receiving relay shown in the center of thatcross-connection. Thus if A sends to B or B to A it is without effect on the homereceiving instrument. Now suppose that both simultaneously are sendingin opposite directions. If the connections be studied it will be seenthat every movement of the transmitting key will affect the balance ofthe distant or receiving end of the bridge and so its instrument willrecord the signals as they are sent. As shown in the cut the sending keys are on local circuits, and workwhat are known as duplex transmitters. These are instruments which sendline signals without breaking the connection. Fig. 313. STEARN'S PLAN OF DUPLEX BRIDGE TELEGRAPHY. In Stearn's plan condensers are introduced as shown. By this plandifferent receiving instruments can be used. The inventor once worked aMorse instrument at one end of the line, and a Hughes' instrument at theother end. 507 STANDARD ELECTRICAL DICTIONARY. Telegraph, Duplex, Differential. A system of duplex telegraphy employing the differential action of twoexciting or magnetizing coils. The general principles are the following. Suppose that at each of two stations, there is a magnet working as asounder or relay. Each magnet is differentially wound, with two coils ofopposite direction, of identical number of turns. When the sending key at a station A is depressed two exactly equalcurrents go through the magnet in opposite directions. One called thecompensation current goes to the earth at the stations. The other calledthe line current goes through the line, through the line coil of thedistant station E, thereby actuating the relay or sounder armature. The instrument of the sender A is unaffected because he is sendingopposite and equal currents through its two coils. A special resistanceis provided on the compensation circuit for keeping the currents exactlyequal in effect. Nothing the sender at A does affects his owninstrument. Now suppose E desires to telegraph back at the same time that A istelegraphing to his station. He works his key. This does not affect hisown instrument except by sending the equal and opposite currents throughits coils. When his key is depressed and A's key is untouched, he worksA's receiving instrument. 508 STANDARD ELECTRICAL DICTIONARY. When A's key is depressed simultaneously with B's key, the two linecurrents are in opposition and neutralize each other. This throws outthe balance in the instruments and both armatures are attracted by thecompensation currents left free to act by the neutralization of the linecurrents. Fig. 314. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM Suppose that B is sending a dash, and it begins while A's key is raised. The line and compensation currents in B's receiving instrumentneutralize each other and no effect is produced, while A's receivinginstrument begins to register or indicate a dash. Now suppose A startsto send a dash while B's is half over. He depresses his key. This sendsthe two opposite currents through his magnet. His line currentneutralizes B's working current so that the compensation currents inboth receiving instruments hold the armatures attracted for the twodashes. Meanwhile A's dash ends and he releases his key. At once hisline current ceases to neutralize B's line current, his receivinginstrument is actuated now by B's line current, while B's receivinginstrument ceases to be actuated by the compensation current. Two assumptions are made in the above description. The line currents areassumed to be equal in strength and opposite in direction at eachstation. Neither of these is necessary. The line current received at astation is always weaker than the outgoing line current, and it is thepreponderance of the compensation current over the partly neutralizedline current that does the work. As this preponderance is very nearlyequal to the line current received from the distant station, the signalsare actuated by almost the same current, whether it is compensation orline current. 509 STANDARD ELECTRICAL DICTIONARY. Both line currents may coincide in direction. Then when the two keys aredepressed, a line current of double strength goes through both receivinginstruments and both work by preponderance of the double line currentover the compensation current. In other respects the operation is thesame as before described. Fig. 315. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM. Fig. 316. DIFFERENTIAL DUPLEX TELEGRAPH CONNECTIONS. The cut shows a diagram of the operation of one end of the line. R and Rare resistances, E and E are earth contacts, and the two circles showthe magnet of the receiving instrument wound with two coils inopposition. The battery and key are also shown. It also illustrates whathappens if the key of the receiver is in the intermediate positionbreaking contact at both 1 and 2. The sender's line current then goesthrough both coils of the receiving instrument magnet, but this time inseries, and in coincident direction. This actuates the instrument asbefore. Owing to the resistance only half the normal current passes, butthis half goes through twice as many coils or turns as if the receiver'skey was in either of the other two positions. In actual practice there are many refinements. To compensate for thevarying resistance of the line a rheostat or resistance with slidingconnection arm is connected in the compensation circuit so that theresistance can be instantly changed. As the electro-static capacity ofthe line varies sectional condensers are also connected in thecompensation circuits. 510 STANDARD ELECTRICAL DICTIONARY. Telegraph, Facsimile. A telegraph for transmitting facsimiles of drawing or writing. Themethods employed involve the synchronous rotation of two metalliccylinders, one at the transmitting end, the other at the receiving end. On the transmitter the design is drawn with non-conducting ink. A tracerpresses upon the surface of each cylinder and a circuit is completedthrough the two contacts. In operation a sheet of chemically preparedpaper is placed over the surface of the receiving cylinder. The twocylinders are rotated in exact synchronism and the tracers are traversedlongitudinally as the cylinders rotate. Thus a number of makes andbreaks are produced by the transmitting cylinder, and on the receivingcylinder the chemicals in the paper are decomposed, producing marks onthe paper exactly corresponding to those on the transmitting cylinder. Synonyms--Autographic Telegraph--Pantelegraphy. Telegraph, Harmonic Multiplex. A telegraph utilizing sympathetic vibration for the transmission ofseveral messages at once over the same line. It is the invention ofElisha Gray. The transmitting instrument comprises a series of vibratingreeds or tuning-forks, each one of a different note, kept in vibrationeach by its own electro-magnet. Each fork is in its own circuit, and allunite with the main line so as to send over it a make and break currentcontaining as many notes superimposed as there are tuning forks. At theother end of the line there are corresponding tuning forks, each withits own magnet. Each fork at this end picks up its own note from themakes and breaks on the main line, by the principle of sympatheticvibration. To each pair of operators a pair of forks of identical notes areassigned. As many messages can be transmitted simultaneously as thereare pairs of forks or reeds. The movements of a telegraph key in circuit with one of the transmittingreeds sends signals of the Morse alphabet, which are picked out by thetuning fork of identical note at the other end of the line. 511 STANDARD ELECTRICAL DICTIONARY. Telegraph, Hughes'. A printing telegraph in very extensive use in continental Europe. Itsgeneral features are as follows: The instruments at each end of the line are identical. Each includes akeyboard like a piano manual, with a key for each letter or character. On each machine is a type wheel, which has the characters engraved inrelief upon its face. With the wheel a "chariot" as it is termed alsorotates. The type wheels at both stations are synchronized. When a keyis depressed, a pin is thrown up which arrests the chariot, and sends acurrent to the distant station. This current causes a riband of paper tobe pressed up against the face of both type wheels so as to receive theimprint of the character corresponding to the key. The faces of thewheels are inked by an inking roller. Fig. 317. ELECTRO-MAGNET OF HUGHES' PRINTING TELEGRAPH. The most characteristic feature is the fact that the current sent bydepressing a key does not attract an armature, but releases one, whichis then pulled back by a spring. The armature is restored to itsposition by the mechanical operation of the instrument. The magnet usedis a polarized electro-magnet. Coils are carried on the ends of a strongpowerful magnet. The coils are so connected that a current sent throughthem by depressing a key is in opposition to the magnetism of thepermanent magnet so that it tends to release the armature, and inpractice does so. This release permits the printing mechanism to act. The latter is driven by a descending weight, so that very slightelectric currents can actuate the instruments. Synonym--Hughes' Type Printer. Telegraphic Code. (a) The telegraphic alphabet, as of the Morse System. (See Alphabet, Telegraphic. ) (b) A code for use in transmitting messages either secretly, orcomprising several words or short sentences in one word, in order toeconomize in transmission. Such codes are extensively used in commercialcable messages. 512 STANDARD ELECTRICAL DICTIONARY. Telegraph, Magneto-electric. A telegraph in which the current is produced by magneto-electricgenerators. It has been applied to a considerable extent in England. TheWheatstone ABC or dial telegraph is operated by a magneto-generatorturned by hand. In this country the magneto-electric generator by which the calling bellof a telephone is rung is an example. The magneto-electric key (See Key, Magneto-electric) is for use in one kind of magneto-electrictelegraphing. Telegraph, Morse. A telegraph, characterized by the use of a relay, working a localcircuit, which circuit contains a sounder, or recorder for giving dotand dash signals constituting the Morse alphabet. The signals are sentby a telegraph key, which when depressed closes the circuit, and whenreleased opens it. The two underlying conceptions of the Morse Telegraphsystem are the use of the dot and dash alphabet, and the use of thelocal circuit, which circuit includes a receiving instrument, and isworked by a relay, actuating a local battery. It would be difficult toindicate any invention in telegraphy which has had such far-reachingconsequences as the one known as the Morse telegraph. In other places the principal apparatus of the system will be founddescribed. The cut Fig. 318, repeated here gives the general dispositionof a Morse system. (See Circuit, Local. ) Fig. 318. DIAGRAM OF MORSE SYSTEM. 513 STANDARD ELECTRICAL DICTIONARY. The key by which the messages are transmitted is shown in Fig. 319. M isa base plate of brass. A is a brass lever, mounted on an arbor G carriedbetween adjustable set screws D. C is the anvil where contact is made bydepressing the key by the finger piece B of ebonite. E, Fl are adjustingscrews for regulating the vertical play of the lever. H is the switchfor opening or closing the circuit. It is opened for transmission, andclosed for receiving. By screws, L L, with wing nuts, K K, the whole isscrewed down to a table. Fig. 319. MORSE TELEGRAPH KEY. In the United States the simplest disposition of apparatus is generallyused. The main line is kept on closed circuit. In it may be included alarge number of relays at stations all along the line, each with its ownlocal circuit. There may be fifty of such stations. Battery is generallyplaced at each end of the line. Very generally gravity batteries areused, although dynamos now tend to supplant them in important stations. As relays the ordinary relay is used. Its local circuit includes asounder and local battery. The latter is very generally of the gravitytype, but oxide of copper batteries (See Battery, Oxide of Copper) arenow being introduced. At main or central offices, the terminals of thelines reach switch boards, where by spring-jacks and plugs, any desiredcircuits can be looped into the main circuit in series therewith. In European practise the main line is kept on open circuit. Polarizedrelays are used to work the local circuits. The currents for these haveto be alternating in direction. When the line is not in use its ends areconnected to earth at both ends, leaving the battery out of circuit. Each intermediate station has its own main, or line battery for use whenit desires to send a message. In the American system as first described, it will be seen that the main batteries are at most two in number. For the details of the different apparatus, the following definitionsmay be consulted: Embosser, Telegraphic--Recorder, Morse--Relay--RelayConnection--Sounder. 514 STANDARD ELECTRICAL DICTIONARY. Telegraph, Multiplex. A system of telegraphy by which a number of messages can be transmittedin both directions over a single wire. The principles underlying thesystems are the following: Suppose that at the two extremities of a telegraph line two arms arekept in absolute synchronous rotation. Let the arms in their rotation, press upon as many conducting segments as there are to be transmissionsover the line. A transmitting and receiving set of instruments may beconnected to one segment at one end of the line, and another set to thecorresponding segment at the distant station. For each pair of segmentstwo sets can be thus connected. Then if the arm rotates so rapidly thatthe contacts succeed each other rapidly enough each pair of sets ofinstruments can be worked independently of the others. In practice thisrapid succession is effected by having a number of contacts made foreach pair during a single rotation of the arm or equivalent. The multiplex system has been perfected by the use of La Cour's phonicwheel (see Phonic Wheel), and brought into a practical success byPatrick B. Delany, of New York. Two phonic wheels rotate at each end of the line. They are kept insynchronous motion by two vibrating steel reeds of exactly the samefundamental note, and the axle of each wheel carries an arm whose endtrails over the contacts or distributor segments already spoken of. Thereeds are adjusted to vibrate at such speed that the trailer is incontact with each segment about 1/500 second. The number of groups ofsegments required for each working is determined by the retardation ofthe signals owing to the static capacity of the line. To convert therapidly recurring impulses of current into practically a single current, condensers are connected across the coils of the relay. One batteryserves for all the arms. Multiplex telegraphy can effect from two to six simultaneoustransmissions over one wire. For two or four transmissions the methodonly distinguishes it from duplex or quadruplex telegraphy. The termsdiode, triode, tetrode, pentode and hexode working are used to indicaterespectively the simultaneous transmission of two, three, four, five, orsix messages over one wire. It will be seen that the multiplex process really assigns to eachtransmission separate times, but divides these times into such short andquickly recurring intervals that the work is executed as if there wascontinuous contact. In no case is there the popular conception of thesending of several messages actually simultaneously over one wire. Eachsignal in reality has its own time assigned it, divided into shortperiods of high frequency, and only utilizes the line when it is free. 515 STANDARD ELECTRICAL DICTIONARY. Telegraph, Over-house. An English term for telegraph lines led over houses and supported onstandards on the roofs. Telegraph Pole Brackets. Arms for carrying insulators, which arms are attached to telegraph polesor other support. They vary in style; sometimes they are straight barsof wood gained into and bolted or spiked in place; sometimes they are ofiron. Telegraph, Printing. Various telegraphs have been invented for printing in the ordinaryalphabet the messages at the receiving end of the line. Representative instruments of this class are used for transmittingdifferent market and stock reports to business offices from theexchanges. The type faces are carried on the periphery of a printingwheel, which is rotated like the hand of a dial telegraph, and againstwhose face a paper riband is pressed whenever the proper letter comesopposite to it. As each letter is printed the paper moves forward thespace of one letter. Spacing between words is also provided for. In therecent instruments two lines of letters are printed on the paper oneabove the other. In England, and on the continent of Europe, printing instruments havereceived considerable use for ordinary telegraphic work. Hughes' typeprinter and Wheatstone's ABC telegraph meet with extensive use there forordinary transmission. Telegraph, Quadruplex. Duplex telegraphy is the sending of two messages in opposite directionssimultaneously through the same wire. Duplex telegraphy is the sendingof two messages simultaneously in the same direction. The two combinedconstitute quadruplex telegraphy. [SIC] The system was suggested by Stark of Vienna and Bosscha of Leyden in1855; the successful problem was solved by Edison in 1874. The principle is based on the two orders of difference in electriccurrents; they may vary in strength or in direction. Thus we may haveone instrument which works with change of strength of current only, theother with change of direction only. The two can be worked together ifthe direction of the current can be altered without alteration ofstrength, and if strength can be altered without alteration ofdirection. Double current and single current working are so combinedthat one relay works by one system of currents and another relay by theother system. A current is constantly maintained through the line. Therelay operated by change in direction is a simple polarized relay whichworks by change of direction of current. The relay operated by change instrength is the ordinary unpolarized relay. 516 STANDARD ELECTRICAL DICTIONARY. For the following description and the cuts illustrating it we areindebted to Preece and Sivewright. The cut shows the arrangement of theapparatus and connections for terminal offices. "Sufficient table room is provided to seat four clerks. The apparatus isarranged for the two senders to sit together in the centre, the messagesto be forwarded being placed between them. The section on the left ofthe switch Q is known as the 'A' side, that on the right as the 'B' sideof the apparatus. K1 the reversing key, reverses the direction of the current. K2 is asimple key, known as the increment key; it is used simply to increasethe strength of the current. Fig. 320. QUADRUPLEX TELEGRAPH CONNECTIONS. The way in which the keys K1 and K2 combine their action is shown byFig. 321. E1 and E2 are the line batteries, the one having two andone-third (2-1/3) the number of cells of the other, so that if E1 be theelectro-motive force of the smaller, that of the whole combined batterywill be 3. 3 E1. The negative pole of E1 is connected to z and z1 of K1and the positive pole of E2 to a of K2 through a resistance coil s. Awire, called the 'tap' wire, connects the positive pole of E1 and thenegative pole of E2 to b of K2. This wire has in it a resistance coilr2. The springs c and c1 of Kl are connected to the lever L of K2. Now, when both keys are at rest, the negative pole of E1 is to line throughz, and the positive pole of E1 to earth through b of K2 and c of K1; thepositive pole of E2 being insulated at a of K2. 517 STANDARD ELECTRICAL DICTIONARY. There is thus a weak negative current flowing to line. When K1 alone isworked, the current of E1 is reversed. When K2 is worked alone, c of K1is transferred from b to a, and the strength of the negative currentgoing to line is increased through the increase of the electro-motiveforce from E1 to 3. 3 E1 for the whole battery is brought into play. WhenK1 and K2 are depressed together, then the negative pole of E1 goes toearth through Z1; and the positive pole of E2 to line through a of K2and c1 of K1 and a positive current, due to the whole electro-motiveforce 3. 3 E1 goes to line. Hence the effect of working K1 is simply toreverse the current, whatever its strength, while that of K2 is tostrengthen it, whatever its direction. The resistance coil s, of 100° resistance, is called a spark coil, because it prevents the high electro-motive force of the whole batteryfrom damaging the points of contact by sparking or forming an arc acrosswhen signals are sent; and the resistance r2 is made approximately equalto the combined resistance of E2 and the spark coil, so that the totalresistance of the circuit may not be altered by the working of theapparatus. Fig. 321. QUADRUPLEX TELEGRAPH. A1 and B1 (Fig. 320) are the relays which are used to respond to thechanges in the currents sent by the keys K1 and K2 at the distantstation. A, is a simple polarized relay wound differentially, each wire having aresistance of 200 [omega], and so connected up as to respond to the working ofthe reversing key K1 of the distant station. It acts independently ofthe strength of the current, and is therefore not affected by theworking of the increment key K2. It is connected up so as to completethe local circuit of the sounder S1 and the local battery l1 and formsthe receiving portion of the 'A' side. B, is a non-polarized relay also wound differentially, each coil havinga resistance of 200 [omega]. It responds only to an increase in thestrength of the current, and therefore only to the working of theincrement key K2 of the distant station. [Transcriber's note: In current usage upper case omega indicates ohms andlower case omega denotes angular frequency, 2*PI*f. ] 518 STANDARD ELECTRICAL DICTIONARY. The relay spring is so adjusted that the armatures are not actuated bythe weak current sent from E by the key K1. In its normal position this relay completes the circuit of the localbattery through the sounder S. This sounder S, called the uprightingsounder, acts as a relay to a second sounder, S2, called the readingsounder, which is worked by another local battery, l2. Of course, normally, the armature of S is held down and that of S2 is up, but whenthe tongue t moves, as it does when the increment key K2 is depressed soas to send the whole current to line, then the current from l isinterrupted, and the circuit of l2 is completed by the rising of thearmature of S, causing the reading sounder S2 to work. This is the 'B'side. R is a rheostat for balancing the resistance of the line, as used induplex working. C is a condenser used for compensating the static charge of the line. Itis provided with an adjustable retardation coil, R1, to prolong theeffect of the compensating current from the condenser. G is a differential galvanometer, used for testing, and for facilitatingadjustment and balancing. Q is a switch for putting the line to earth, either for balancing, orfor any other purpose. There is on the earth wire leading from Q aresistance coil, r1, equalling approximately the resistance of the wholebattery, 3. 3 E1, and the resistance s. The connections shown in Fig. 321, are for an 'up' office. At a 'down'office it is necessary to reverse the wires on the two lower terminalsof the galvanometer and the two battery wires on the reversing key K1. The keys K1 and K2 are, for repeaters, replaced by transmitters. The adjustment of this apparatus requires great care and great accuracy. Its good working depends essentially on technical skill that can only beacquired by patience and perseverance. Faults in working generally arise from careless adjustments, dirtycontacts, loose connections, battery failures, and the ordinary lineinterruptions, but there are no troubles that are beyond the reach ofordinary skill, and it can be safely said that, within moderatedistances, wherever and whenever duplex working is practicable, thenquadruplex working is so too. " The above is a typical quadruplex bridge system. There is also adifferential system, the full description of which, in addition to whathas been given, is outside of the scope of this work. 519 STANDARD ELECTRICAL DICTIONARY. Telegraph Repeater. An extension of the relay system, adopted for long lines. A repeatingstation comprises in general terms duplicate repeating apparatus. Oneset is connected for messages in one direction, the other for messagesin the opposite direction. The general operation of a repeating set isas follows. The signals as received actuate a relay which by its localcircuit actuates a key, which in ordinary practise would be the sounder, but in the repeater its lever opens and closes a circuit comprising abattery and a further section of the line. Repeaters are placed at intervals along the line. Each repeater repeatsthe signals received for the next section of line with a new battery. Itrepresents an operator who would receive and repeat the message, exceptthat it works automatically. The Indo-European line from London to Teheran, 3, 800 miles long, isworked directly without any hand retransmission, it being carried out byfive repeaters. This gives an average of over 500 miles for eachrepeater. [Transcriber's note: … 650 miles for each repeater. ] Repeaters introduce retardation, and each repeater involves a reductionin the rate of working. Yet in many cases they increase the speed of aline greatly, as its speed is about equal to that of its worst section, which may be far greater than that of the whole line in one. Synonym--Translater. Telegraph Signal. In the telegraph alphabet, a dot, or dash; the signal or effect producedby one closing of the circuit. A dash is equal in length to three dots. The space between signals is equal to one dot; the space between lettersto three dots; and the space between words to six dots. Telegraph, Single Needle. A telegraph system in which the code is transmitted by the movements ofa needle shaped index which oscillates to right and left, the left handdeflection corresponding to dots, the right hand deflection to dashes. The instruments for sending and receiving are combined into one. Theneedles are virtually the indexes of vertical galvanometers. In one formby a tapper key (see Tapper), in another form by a key worked by adrop-handle (the drop handle instrument), currents of oppositedirections are sent down the line. These pass through both instruments, affecting both needles and causing them to swing to right or left, asthe operator moves his key. As galvanometer needle or actuating needle a soft iron needle isemployed, which is polarized by the proximity of two permanent magnets. This avoids danger of reversal of polarity from lightning, a troubleincident to the old system. 520 STANDARD ELECTRICAL DICTIONARY. The cut, Fig. 322, shows a single needle telegraph instrument of thetapper form. The action of the tapper can be understood from the nextcut. Fig. 322. SINGLE NEEDLE TELEGRAPH INSTRUMENT, DOUBLETAPPER FORM. Fig. 323. DOUBLE TAPPER KEY FOR SINGLE NEEDLE TELEGRAPH. C and Z are two strips of metal to which the positive and negative polesof the battery are respectively connected. E and L are two metallicsprings; E is connected to earth, L is connected to the line; at restboth press against Z. If L is depressed so as to touch C, the currentfrom the battery goes to the line by the key L, goes through the coilsof the distant instrument and deflects the needle to one side, and thengoes to the earth. If the key E is depressed, L retaining its normalposition, the direction of the current is reversed, for the other poleof the battery is connected to the earth and the reverse current goingthrough the coils of the distant instrument deflects the galvanometerneedle to the other side. In the drop-handle type an analogous form of commutator worked by asingle handle produces the same effects. 521 STANDARD ELECTRICAL DICTIONARY. Telegraph, Wheatstone, A. B. C. A magneto-electric telegraph of the dial system. An alternating currentmagneto-generator is turned by hand and by depressing keys its currentis admitted to or cut off from the line and receiver's instrument. Themessage is received by a dial instrument working by the escapementmotion described under Telegraph, Dial. Telegraph, Writing. A telegraph in which the message is received in written characters. Thetransmitter includes a stylus which is held in the hand and whose pointbears against the upper end of a vertical rod. The rod is susceptible ofoscillation in all directions, having at its base a spring supportequivalent to a universal joint. The stylus is moved about in the shape of letters. As it does this itthrows a series of resistances in and out of the circuit. At the receiving end of the line the instrument for recording themessage includes two electro-magnets with their cores at right angles toeach other and their faces near together at the point of the angle. Anarmature is supported between the faces and through it a vertical rodcarried by a spring at its bottom rises. These magnets receive currentproportional to the resistances cut in and out by the motions of theother rod at the transmitting end of the line. These resistances arearranged in two series at right angles to each other, one for eachmagnet. Thus the movements of the transmitting stylus and rod arerepeated by the end of the rod in the receiving instrument. A species ofpen is carried at the end of the rod of the receiving instrument, whichmarks the letters upon a riband of paper which is fed beneath it. Telemanometer. Electric. A pressure gauge with electric attachment for indicating or recordingits indications at a distance. It is applicable to steam boilers, so as to give the steam pressure inany desired place. Telemeter, Electric. An apparatus for electrically indicating or recording at a distance theindications of any instrument such as a pressure gauge, barometer orthermometer, or for similar work. The telemanometer applied to a boilercomes into this class of instrument. Telephotography. The transmission of pictures by the electric current, the requisitechanges in the current being effected by the action of light uponselenium. The picture is projected by a magic lantern. Its projection istraversed by a selenium resistance through which the current passes. This is moved systematically over its entire area, thus constituting thetransmitter, and synchronously with the motion of the selenium a contactpoint at the other end of the line moves systematically over a sheet ofchemically prepared paper. The paper, which may be saturated with asolution of potassium ferrocyanide and ammonium nitrate, is stained bythe passage of the current, and by the variation in intensity ofstaining, which variation is due to variations in the current, producedby the effects of the light upon the selenium, the picture isreproduced. 522 STANDARD ELECTRICAL DICTIONARY. Telepherage. An electric transportation system, hitherto only used for the carryingof ore, freight, etc. Its characteristic feature is that the electricconductors, suspended from poles, supply the way on which carriagesprovided with electric motors run. The motors take their currentdirectly from the conductors. There are two conducting lines, running parallel with each other, supported at the opposite ends of transverse brackets on a row ofsupporting poles. At each pole the lines cross over so that right linealternates with left, between consecutive pairs of poles. The cars are suspended from pulleys running on one or the other of theconductors. A train of such cars are connected and the current is takenin near one end and leaves near the other end of the train. Thesecurrent connections are so distant, their distance being regulated bythe length of the train, that they are, for all but an instant at thetime of passing each of the poles, in connection with segments of theline which are of opposite potential. To carry out this principle thedistance between contacts is equal to the distance between poles. Owingto the crossing over of the lines the contacts are in connection asdescribed and thereby the actuating current is caused to go through themotors. Cars running in one direction go on the electric conductors on the oneside, those running in the other direction go on the other conductor. A great many refinements have been introduced, but the system has beenvery little used. Telephone. An instrument for the transmission of articulate speech by the electriccurrent. The current is defined as of the undulatory type. (See Current, Undulatory. ) The cut shows what may be termed the fundamental telephone circuit. Aline wire is shown terminating in ground plates and with a telephone incircuit at each end. The latter consists of a magnet N S with a coil ofinsulated wire H surrounding one end. Facing the pole of the magnet is asoft iron diaphragm D, held in a frame or mouthpiece T. Any change ofcurrent in the line affects the magnetism of the magnet, causing it toattract the diaphragm more or less. The magnet and diaphragm reallyconstitute a little electric motor, the diaphragm vibrating back andforth through an exceedingly short range, for changes in the magneticattraction. The principle of the reversibility of the dynamo applies here. If themagnet is subjected to no change in magnetism, and if the diaphragm ismoved or vibrated in front of its poles, currents will be induced in thewire bobbin which surrounds its end. If two such magnets with bobbinsand diaphragms are arranged as shown, vibrations imparted to onediaphragm will send currents through the line which, affecting themagnetism of the distant magnet, will cause its diaphragm to vibrate inexact accordance with the motions of the first or motor diaphragm. Inthe combination one telephone represents a dynamo, the other a motor. If the vibrations of the diaphragm are imparted by the voice, the voicewith all its modulations will be reproduced by the telephone at thedistant end of the line. 523 STANDARD ELECTRICAL DICTIONARY. Fig. 324. DIAGRAM OF BELL TELEPHONES AND LINE WITH EARTH CONNECTIONS. Fig. 325. SECTION OF BELL TELEPHONE. The above gives the essential features of the Bell telephone. Inpractice the telephone is used only as the receiver. As transmitter amicrophone is employed. To give the current a battery, generally of theopen circuit type, is used, and the current in the line is an induced orsecondary one. The microphone which is talked to, and which is the seat of the currentvariations which reproduce original sound, is termed the transmitter, the telephone in which the sounds are produced at the distant end of theline is termed the receiver. Fig. 325 shows the construction of the Bell telephone in universal usein this country as the receiver. M is a bar magnet, in a case L L. B Bis a bobbin or coil of insulated wire surrounding one end of the magnet. D is the diaphragm of soft iron plate (ferrotype metal), and E is themouthpiece. The terminals of the coil B B connect with the bindingscrews C C. The wire in the coil is No. 36, A. W. G. , and is wound to aresistance of about 80 ohms. 524 STANDARD ELECTRICAL DICTIONARY. As typical transmitter the Blake instrument may be cited. It is a carbonmicrophone. It is shown in section in the cut; a is the mouthpiece and eis a diaphragm of iron plate, although other substances could be used; fis a steel spring, with a platinum contact piece at its end. One endbears against the diaphragm, the other against a carbon block k. Thelatter is carried by a brass block p, and pressure is maintained betweenthese contacts by the spring g and weight of the piece c, which bygravity tends to press all together. The current passes by way of thespring f, carbon button k and spring g through the circuit indicated. A battery is in circuit with these parts. If a telephone is also incircuit, and the transmitter is spoken against, the diaphragm vibratingaffects the resistance of the carbon-platinum contact, without evenbreaking the contact, and the telephone reproduces the sound. The heavypiece of metal C acts by its inertia to prevent breaking of the contact. The position of this piece c, which is carried by the brass plate m, isadjusted by the screw n. Fig. 326. SECTION OF BLAKE TRANSMITTER. In practice the transmitter and battery are usually on a local circuit, which includes the primary of an induction coil. The line and distantreceiving telephone are in circuit with the secondary of the inductioncoil, without any battery. Telephone, Bi-. A pair of telephones carried at the ends of a curved bar or spring sothat they fit the head of a person using them. One telephone is heldagainst each ear without the use of the hands. 525 STANDARD ELECTRICAL DICTIONARY. Telephone, Capillary. A telephone utilizing electro-capillarity for the production oftelephonic effects. The following describes the invention of AntoineBreguet. The point of a glass tube, drawn out at its lower end to a capillaryopening dips vertically into a vessel. This vessel is partly filled withmercury, over which is a layer of dilute sulphuric acid. The end of theimmersed tube dips into the acid, but does not reach the mercury. Oneline contact is with mercury in the tube, the other with the mercury inthe vessel. The arrangement of tube and vessel is duplicated, giving oneset for each end of the line. On introducing a battery in the circuitthe level of the mercury is affected by electro-capillarity. The tubesare closed by plates or diaphragms at their tops, so as to enclose acolumn of air. It is evident that the pressure of this air will dependupon the level of the mercury in the tube, and this depends on theelectro-motive force. On speaking against the diaphragm the sound wavesaffect the air pressure, and consequently the level, enough to causepotential differences which reproduce the sound in the other instrument. Fig. 327. BREGURT'S CAPILLARY TELEPHONE. Telephone, Carbon. A telephone transmitter based on the use of carbon as a material whoseresistance is varied by the degree of pressure brought to bear upon it. Undoubtedly the surface contact between the carbon and the otherconducting material has much to do with the action. Many carbontelephones have been invented. Under Telephone the Blake transmitter isdescribed, which is a carbon telephone transmitter. The Edison carbontransmitter is shown in section in the cut. E is the mouth piece and Dthe diaphragm. I is a carbon disc with adjusting screw V. A platinumplate B B, with ivory button b, is attached to the upper surface of thecarbon disc. C C is an insulating ring. The wire connections shown bringthe disc into circuit. It is connected like a Blake transmitter. It isnow but little used. Fig. 328. SECTION OF EDISON CARBON TRANSMITTER. 526 STANDARD ELECTRICAL DICTIONARY. Telephone, Chemical. A telephone utilizing chemical or electrolytic action in transmitting orreceiving. The electro-motograph is an example of a chemical receiver. (See Electro-motograph. ) Telephone, Electrostatic. A telephone utilizing electrostatic disturbances for reproduction of thevoice. In the cut D and C are highly charged electrophori. Thediaphragms A and B when spoken to affect the potential of theelectrophorus so as to produce current variations which will reproducethe sound. Dolbear and others have invented other forms of transmittersbased on electrostatic action. Receivers have also been constructed. Asimple condenser may be made to reproduce sound by being connected witha powerful telephone current. Fig. 329. DIAGRAM OF EDISON'S ELECTROSTATIC TELEPHONE. Telephone Induction Coil. The induction coil used in telephone circuits for inducing current onthe main line. It is simply a small coil wound with two separatecircuits of insulated wire. In the Edison telephone the primary coil, incircuit with the transmitter, is of No. 18 to 24 wire and of 3 to 4 ohmsresistance. The secondary in circuit with the line and receivinginstrument is of No. 36 wire and of 250 ohms resistance. The Belltelephone induction coil has its primary of No. 18 to 24 wire wound to aresistance of 1/2 ohm, and its secondary of No. 36 wire, and of 80 ohmsresistance. 527 STANDARD ELECTRICAL DICTIONARY. Telephone, Reaction. A form of telephone containing two coils of insulated wire, one of whichis mounted on the disc, and the other on the magnet pole in the usualway. These coils react upon each other so as to strengthen the effect. Telephone, Thermo-electric. A telephone transmitter including a thermo-electric battery, placed incircuit with the line. A plate of vulcanite faces it. When the soundwaves strike the vulcanite they move it backward and forward. Thesemovements, owing to the elasticity of the vulcanite, produce minutechanges of temperature in it, which affecting the thermo-electric pileproduce in the circuit currents, which passing through a Bell telephonecause it to speak. This type of instrument has never been adopted inpractice. Telephote. An apparatus for transmitting pictures electrically, the properties ofselenium being utilized for the purpose. Synonym--Pherope. Teleseme. An annunciator, displaying on a dial the object wanted by the personusing it. It is employed to transmit messages from rooms in a hotel tothe office, or for similar functions. Tele-thermometer. A thermometer with electric attachment for indicating or recording itsindications at a distance. Tempering, Electric. A process of tempering metals by electrically produced heat. The articleis made part of an electric circuit. The current passing through itheats it, thereby tempering it. For wire the process can be madecontinuous. The wire is fed from one roll to another, and if requiredone roll may be immersed in a liquid bath or the wire between the rollsmay be led therein. The current is brought to one roll and goes throughthe wire to the other. As it does this the wire is constantly fed fromone roll to another. The bath may be used as described to cool it afterthe heating. The amount of heating may be regulated by the rate ofmotion of the wire. 528 STANDARD ELECTRICAL DICTIONARY. Ten, Powers of. This adjunct to calculations has become almost indispensable in workingwith units of the C. G. S. System. It consists in using some power of 10as a multiplier which may be called the factor. The number multipliedmay be called the characteristic. The following are the generalprinciples. The power of 10 is shown by an exponent which indicates the number ofciphers in the multiplier. Thus 10^2 indicates 100; 10^3 indicates 1, 000and so on. The exponent, if positive, denotes an integral number, as shown in thepreceding paragraph. The exponent, if negative, denotes the reciprocalof the indicated power of 10. Thus 10^-2 indicates 1/100; 10^-3 indicates1/1000 and so on. The compound numbers based on these are reduced by multiplication ordivision to simple expressions. Thus: 3. 14 X 10^7 = 3. 14 X 10, 000, 000 =31, 400, 000. 3. 14 X 10^-7 = 3. 14/10, 000, 000 or 314/1000000000. Regard mustbe paid to the decimal point as is done here. To add two or more expressions in this notation if the exponents of thefactors are alike in all respects, add the characteristics and preservethe same factor. Thus: (51X 10^6) + (54 X 10^6) = 105 X 10^6. (9. 1 X 10^-9) + (8. 7 X 10^-9) = 17. 8 X 10^-9. To subtract one such expression from another, subtract thecharacteristics and preserve the same factor. Thus: (54 X 10^6) - (51 X 10^6) = 3 X 10^6. If the factors have different exponents of the same sign the factor orfactors of larger exponent must be reduced to the smaller exponent, byfactoring. The characteristic of the expression thus treated ismultiplied by the odd factor. This gives a new expression whosecharacteristic is added to the other, and the factor of smaller exponentis preserved for both, Thus: (5 X 10^7) + (5 X10^9) = (5 X 10^7) + (5 X 100 X 10^7) = 505 X 10^7. The same applies to subtraction. Thus: (5 X 10^9) - (5 X 10^7) = (5 X 100 X 10^7) - (5 X 10^7) = 495 X 10^7. If the factors differ in sign, it is generally best to leave theaddition or subtraction to be simply expressed. However, by followingthe above rule, it can be done. Thus: Add 5 X 10^-2 and 5 X 10^3. 5 X 10^3 = 5 X 10^5 X 10^-2 (5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2 This may be reduced to a fraction 500000/100 = 5000. 05. To multiply add the exponents of the factors, for the new factor, andmultiply the characteristics for a new characteristic. The exponentsmust be added algebraically; that is, if of different signs thenumerically smaller one is subtracted from the other one, and its signis given the new exponent. Thus; (25 X 10^6) X (9 X 10^8) = 225 X 10^14. (29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1 (9 X 10^8) X (98 X 10^2) = 882 X 10^1 529 STANDARD ELECTRICAL DICTIONARY. To divide, subtract (algebraically) the exponent of the divisor fromthat of the dividend for the exponent of the new factor, and divide thecharacteristics one by the other for the new characteristic. Algebraicsubtraction is effected by changing the sign of the subtrahend, subtracting the numerically smaller number from the larger, and givingthe result the sign of the larger number. (Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2. ) Thus; (25 X 10^6) / (5 X 10^8) = 5 X 10^-2 (28 X 10^-8) / (5 X 10^3) = 5. 6 X 10^-11 [Transcriber's note: I have replaced ordinary exponential notation bythe more compact and simpler "programming" representation. The last twoexample would be: 25E6 / 5E8 = 5E-2 28E-8 / 5E3 = 5. 6E-11] Tension. Electro-motive force or potential difference in a current system isoften thus termed. It is to be distinguished from intensity or currentstrength, which word it too greatly resembles. Tension, Electric. (a) The condition an electrified body is brought into byelectrification, when each molecule repels its neighbor. The conditionis described as one of self-repulsion. (b) The voltage or potential difference of a circuit is also thustermed. Terminal. The end of any open electric circuit, or of any electric apparatus; asthe terminals of a circuit, dynamo, or battery. Terminal Pole. In telegraph line construction the last pole of a series; one beyondwhich the line is not carried. Such pole, as the pull of the wires isall in one direction, requires special staying or support. The regularline poles are free from this strain, as the wire pulls in bothdirections. Tetanus, Acoustic. A term in electro-therapeutics. An effect produced on a nerve by veryrapidly alternating induced currents. The currents are produced by aninduction coil with a vibrator giving a musical note. This is a speciesof gauge of proper frequency of alternations. Theatrophone. An apparatus worked by automatic paying machinery by which a telephoneconnection is made with a theatre or opera by the deposition of a coinin a slot. Therm. A unit of heat. It has been proposed by the British Association andamounts to a redefinition of the smaller calorie. It is the amount ofheat required to raise the temperature of one gram of water one degreecentigrade, starting at the temperature of maximum density of water. 530 STANDARD ELECTRICAL DICTIONARY. Thermaesthesiometer. An electro-therapeutic instrument for testing the sensitiveness of thesurface of the body to changes of temperature. Vessels of mercury areprovided with thermometers to indicate their temperature. One vessel issurrounded by an electric conductor wound in a number of turns. Thetemperature is raised by passing a current through this. By successiveapplications of the vessels to the same spot upon the skin the power ofdifferentiating temperatures is determined. Thermo Call. (a) An electric alarm or call bell operated by thermo-electric currents. It may serve as a fire alarm or heat indicator, always bearing in mindthe fact that differential heat is the requisite in a thermo-electriccouple. (b) See Thermo-electric Call. Thermo-chemical Battery. A voltaic battery in which the electro-motive force is generated bychemical action induced by heat. The chemical used generally is sodium nitrate or potassium nitrate. Thepositive plate is carbon. On heating the battery the nitrate attacks thecarbon, burning it and produces potential difference. For negative platesome metal unattacked by the nitrate may be employed. Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY. Thermo-electric Battery or Pile. A number of thermo-electric couples q. V. , connected generally inseries. In Nobili's pile the metals are bismuth and antimony; paper bandscovered with varnish are used to insulate where required. In Becquerel'spile copper sulphide (artificial) and German silver, (90 copper, 10nickel) are the two elements. The artificial copper sulphide is madeinto slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about). Water is used to keep one set of junctions cool, and gas flames to heatthe other set. In Fig. 331, c, d represent the binding screws. Thecouples are mounted on a vertical standard, with adjusting socket andscrew B, so that its lower end can be immersed in cold water, or raisedtherefrom as desired. 531 STANDARD ELECTRICAL DICTIONARY. FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES. Fig. 332 shows one couple of the battery. S is artificial antimonysulphide; M is German silver; m is a protecting plate of German silverto save the sulphide from wasting in the flame. Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES. Clamond's pile has been used in practical work. The negative element isan alloy of antimony, 2 parts, zinc, 1 part. The positive element is tinplate. Mica in some parts, and a paste of soluble glass and asbestus inother parts are used as insulators. They are built up so as to form acylinder within which the fire is maintained. The air is relied on tokeep the outer junctions cool. The temperature does not exceed 200° C. (392° F. ) Sixty such elements have an electro-motive force of 300 volts and aninternal resistance of 1. 5 ohms. Such a battery requires the consumptionof three cubic feet of gas per hour. (See Currents, Thermo-electric. ) 532 STANDARD ELECTRICAL DICTIONARY. Thermo-electric Call. A thermostat arranged to ring a bell or to give some indication when thetemperature rises or falls beyond certain points. It may be a compoundbar of brass and steel fixed at one end and free for the rest of itslength. Its end comes between two adjustable contacts. As thetemperature rises it bends one way (away from the brass side) and, ifhot enough, touching a contact gives one signal. If the temperaturefalls it curves the other way, and if cold enough touches the othercontact, giving another signal. (See Thermostat, Electric. ) Thermo-electric Couple. If two dissimilar conductors form adjacent parts of a closed circuit, and their junction is at a different temperature than that of the restof the circuit, a current will result. Such pair of conductors arecalled a thermo-electric couple. They may be joined in series so as toproduce considerable electro-motive force. (See Thermo-electricity andother titles in thermo-electricity. ) The efficiency of a thermo-electric couple according to the second lawof thermo-dynamics is necessarily low--not over 10 per cent. Thermo-electric Diagram. A diagram indicating the change in potential difference for a fixeddifference of temperature between different metals at differenttemperatures. It is laid out with rectangular co-ordinates. On one axistemperatures are laid off, generally on the axis of abscissas. On theother axis potential differences are marked. Different lines are thendrawn, one for each metal, which show the potential difference, say forone degree centigrade difference of temperature between their junctions, produced at the different temperatures marked on the axis of abscissas. Fig. 333· THERMO-ELECTRIC DIAGRAM, GIVING POTENTIAL DIFFERENCE INC. G. S. UNITS. Thus taking copper and iron we find at the temperature 0° C. (32° F. ) adifference of one degree C. (1. 8° F. ) in their junctions will produce apotential difference of 15. 98 micro volts, while at 274. 5° C. (526. 1°F. ) the lines cross, and zero difference of potential is indicated. Taking the lead line on the same diagram it crosses the iron line alittle above 350° C. (662° F. ), indicating that if one junction isheated slightly above and the other is heated slightly below thistemperature no potential difference will be produced. Lead and copperlines, on the other hand, diverge more and more as the temperaturerises. 533 STANDARD ELECTRICAL DICTIONARY. Thermo-electric Inversion. The thermo-electric relations of two conductors vary at differenttemperatures. Sometimes at a definite point they have no electro-motiveforce and after passing this point the positive plate becomes a negativeone and vice versa. This is inversion, or reversal. (See Thermo-electricDiagram. ) Synonym-- Thermo-electric Reversal. Thermo-electricity. Electric energy, electro-motive force or electrification produced fromheat energy by direct conversion. It is generally produced in a circuitcomposed of two electric conductors of unlike material, which circuitmust possess at least two junctions of the unlike substances. By heatingone of these to a higher temperature than that of the other, or bymaintaining one junction at a different temperature from that of theother a potential difference is created accompanied by an electriccurrent. In many cases differential application of heat to an identical materialwill develop potential difference. This effect, the converse of theThomson effect, is not used to produce currents, as in a closed circuitthe potential differences due to differential heating would neutralizeeach other. Thermo-electric Junction. A junction between two dissimilar conductors, which when heated orcooled so as to establish a differential temperature, as referred to thetemperature of the other junction, produces potential difference and anelectric current. Thermo-electric Pile, Differential. A thermo-electric pile arranged to have opposite faces subjected todifferent sources of heat to determine the identity or difference oftemperature of the two sources of heat. It corresponds in use to adifferential air thermometer. Thermo-electric Power. The coefficient which, multiplying the difference of temperature of theends of a thermo-electric couple, gives the potential difference, expressed in micro-volts. It has always to be assigned to a mean oraverage temperature of the junctions, because the potential differencedue to a fixed difference of temperature between two metals varies withthe average temperature of the two junctions. (See Thermo-electricDiagram. ) For bismuth and antimony at 19. 5° C. (67. 1° F. ) it is 103 microvolts perdegree Centigrade (1. 8° F. ). This means that if one junction is heatedto 19° C. And the other to 20° C. (66. 2° F. And 68. 0° F. ) a potentialdifference of 103 micro-volts will be produced. The potential difference is approximately proportional to the differenceof temperature of the two junctions if such difference is small. Hencefor large differences of potential the thermo-electric power coefficientdoes not apply. As a differential function it is thus deduced by Sir William Thomson, for expressing the E. M. F. In a thermo-electric circuit: If a circuitis formed of two metals with the junctions at indefinitely neartemperatures, t and t + dt, and dE is the E. M. F. Of the circuit, thenthe differential coefficient dE/dt is called the thermo-electric powerof the two metals for the temperature t. 534 STANDARD ELECTRICAL DICTIONARY. Thermo-electric Series. The arrangement of possible thermoelectric elements, q. V. , in a tablein the order of their relative polarity. Bismuth and antimony form acouple in which when their junction is heated the bismuth acts as thepositive or negatively charged element and antimony as the negative orpositively charged. Between these two extremes according to Seebeck theseries runs as follows: Antimony, Silver, Copper, Arsenic, Gold, Platinum, Iron, Molybdenum, Palladium, Steel, Tin, Cobalt, Cadmium, Lead, Nickel, Tungsten, Mercury, Bismuth. Zinc, Manganese, A differential temperature of 1° C. (1. 8° F. ) in a bismuth-antimonycouple maintains a potential difference of 103 micro-volts. Matthiessen gives a different series; it is arranged in two columns; thefirst column has positive coefficients annexed the second has negative. On subtracting the greater one from the lesser, which, if the twoelements are in different columns, of course amounts to adding afterchanging the negative sign, the relative potential difference due to thecombination is obtained. + - Bismuth 25 Gas Coke 0. 1 Cobalt 9 Zinc 0. 2 Potassium 5. 5 Cadmium 0. 3 Nickel 5 Strontium 2. 0 Sodium 3. Arsenic 3. 8 Lead 1. 03 Iron 5. 2 Tin 1 Red Phosphorous 9. 6 Copper 1 Antimony 9. 8 Silver 1 Tellurium 179. 9 Platinum 0. 7 Selenium 290 Thus the relative E. M. F. Of a bismuth-nickel couple, as both are inthe + column, would be 25 - 5 = 20; that of a cobalt-iron couple, onebeing in the + column the other in the - column, would be 9 + 5. 2 =14. 2. Alloys are not always intermediate to their constituents, andsmall amounts of impurities affect the results largely. This may accountfor the discrepancies of different observers. Other compounds could beintroduced into the series. Artificial silver sulphide has been used by Becquerel in athermo-electric battery. 535 STANDARD ELECTRICAL DICTIONARY. Thermo-electric Thermometer. A species of differential thermometer. It consists of twothermo-electric junctions connected in opposition with a galvanometer inthe circuit. Any inequality of temperature in the two ends or junctionsproduces a current shown by the galvanometer. It may be used todetermine the temperature of a distant place, one of the junctions beinglocated there and the other being under control of the operator. If thelatter junction is heated until no current is produced its temperatureis evidently equal to that of the distant couple or junction. Theheating may be done with hot water or mercury, or other melted metal. The temperature of the water, or other substance, gives the temperatureof the distant place. Thermolysis. Decomposition by heat; dissociation. All compound bodies aredecomposable by heat if it is intense enough. Hence at very elevatedtemperatures there can be no combustion. Synonym--Dissociation. Thermometer. An instrument for indicating the intensity of heat. Three scales ofdegrees of heat are used in practise, the Fahrenheit, Réamur, andCentigrade, each of which is described under its own title. (See Zero, Thermometric-Zero, Absolute. ) The ordinary thermometer depends on theexpansion of mercury; in some cases alcohol is used. Besides these thecompound bar principle as used in the thermostat (see Thermostat, Electric) is employed. Thermometer, Electric. (a) A thermometer whose indications are due to the change of resistancein conductors with change of temperature. Two exactly similar resistancecoils maybe electrically balanced against each other. On exposing one toa source of heat, its resistance will change and it will disturb thebalance. The balance is restored by heating the other coil in a vesselof water when the temperature of the water gives the temperature of bothcoils. The coils are enclosed in water-tight metallic cases. Synonym--Electric Resistance Thermometer. (b) A differential thermometer may be made by connecting with a pair ofconductors, two thermo-electric couples in opposition to each other, andincluding a galvanometer in series. On heating the junction of onecouple more than that of the other a current at once goes through thegalvanometer. (c) (See Thermometer, Kinnersley's. ) Synonym--Thermo-electrometer. 536 STANDARD ELECTRICAL DICTIONARY. Fig. 334. KINNERSLEY'S THERMOMETER. Thermometer, Kinnersley's. A thermo-electrometer. A large glass tube is mounted on a standard andcommunicates with a small tube parallel to it. Water is poured in so asto rise in the small tube. Two wires terminating in bulbs enter thelarge tube by its top and bottom. The upper wire can be adjusted bymoving up and down through a stuffing box. On discharging a Leyden jarthrough the space between the knobs on the two wires the water for amoment rises in the small tube. There is little or no accuracy in theinstrument. It is allied to the electric mortar (see Mortar, Electric)as a demonstrative apparatus. Synonyms--Electric Thermometer--Thermo-electrometer. Thermo-multiplier. A thermo-electric battery including a number of couples. The term isgenerally applied to a small battery with its similar junctions facingin one direction and used for repeating Melloni's experiments on radiantenergy, or so-called radiant heat. 537 STANDARD ELECTRICAL DICTIONARY. Thermophone. An apparatus for reproducing sounds telephonically by the agency ofheat; a receiving telephone actuated by heat. Thus a wire may beattached to the centre of a diaphragm and kept in tension therefrom, andthe transmitting telephone current may be caused to pass through it. Thewire changes in temperature and consequently in length with the pulsesof current going through it and vibrates the diaphragm, reproducing thesound. It is to be distinguished from the thermo-electric telephonewhich involves the action of potential difference produced bythermo-electric action. Thermostat, Electric. A thermostat or apparatus, similar to a thermometer in some cases, forclosing an electric circuit when heated. It is used in connection withautomatic fire alarms to give warning of fire. For this use atemperature of 52° C. (125° F. ) is an approved one for setting one at, to complete the circuit. It is also applied to regulation oftemperature, as in incubators. (a) One kind of thermostat consists of a compound bar wound into aspiral and fastened at one end, to which a terminal of a circuit isconnected. The bar may be made of two strips of brass and iron rivetedtogether, and wound into a spiral. When such a bar is submitted tochanges of temperature it bends in different directions, because brassexpands and contracts more under changes of temperature than does iron. A contact point, to which the other terminal is connected, is arrangedto make contact with the spiral at any desired degree of temperature, thus closing an electric circuit and ringing a bell, opening or closinga damper, or doing anything else to notify an attendant or to directlychange the temperature. If the brass forms the outside of the spiral, increase of temperaturemakes the bending of the spiral bring the coils still closer. If thebrass forms the inside, increase of temperature makes the spiral tend tobecome less close. As shown in the cut, the brass should lie along theinside of the spiral. Sometimes a straight compound bar is used, one of whose ends is fastenedand the other is free. As the temperature changes such a bar curves moreor less, its free end moving to and fro. Two contact screws areprovided, one on each side of its free end. If the temperature falls itmakes contact with one of these; if the temperature rises, it makescontact with the other. Thus it may close one of two circuits, one for afall and the other for a rise in temperature. It is well to introduce a third bar between the brass and iron ones, made of some material of intermediate coefficient of expansion. (b) Another kind of thermostat comprises a vessel of air or other gas, which, expanding by heat, actuates a piston or other device and closesan electric circuit. Synonym--Electro-pneumatic Thermostat. (c) Another form utilizes the expansion of mercury. The mercury is madepart of an open electric circuit. As it expands it comes in contact withthe other terminal of the circuit, thus completing it, when the currentgives an alarm or does as is provided for in the apparatus employed. Thermostats may be worked on either open or closed circuits; normallythe circuit may be open as described and may close on rise oftemperature, or it may be normally closed and open as the temperaturerises. Fig. 335. ELECTRIC THERMOSTAT. 538 STANDARD ELECTRICAL DICTIONARY. Thomson Effect. In an unequally heated conductor the differential heating is eitherincreased as in iron, or diminished as in copper by a current. In leadthe phenomenon does not occur. It is termed the Thomson effect. It isintimately related to the Peltier effect. In a thermo-electric couple a heated junction is the source ofelectro-motive force, if heated more than other parts of the circuit. The current in a copper-iron junction flows from the copper to the ironacross the heated junction. A hot section of an iron conductor next to acold section of the same is a source of thermoelectricity, in the sensethat the hot section is negative to the colder. A current passing fromthe hot to the cold iron travels against rising potentials, and coolsthe iron in the cooler parts. As it passes to the hotter parts ittravels against falling potentials and hence heats the iron in theseparts. In this way a current intensifies differential heating in an ironconductor. In copper the reverse obtains. In it the thermo-electric relations ofhot and cold copper are the reverse of those of iron, and a currenttends to bring all parts of a differentially heated copper conductor toan identical temperature. As a current travels in iron from hot to cold it absorbs heat; in coppertraveling from cold to hot it absorbs heat. The convection of heat by a current of electricity in unequally heatediron is negative, for it is opposed to that convection of heat whichwould be brought about by the flow of water through an unequally heatedtube. In copper, on the other hand, the electric convection of heat ispositive. (Daniell. ) The above effects of the electric current upon an unequally heatedconductor are termed the Thomson effects. In iron, at low red heat, theyare reversed and are probably again reversed at higher temperatures. 539 STANDARD ELECTRICAL DICTIONARY. Three Wire System. A system of distribution of electric current for multiple arc orconstant potential service. It is the invention of Thomas A. Edison. It includes three main wires which start from the central station orgenerating plant, and ramify with corresponding reduction in size, everywhere through the district or building to be lighted. As ordinarilycarried out when dynamos are used, the dynamos are arranged in groups oftwo. One lateral lead starts from the negative binding post of onedynamo. The positive terminal of this dynamo connects to the negative ofthe other. Between the two dynamos the central or neutral lead isconnected. The other lateral lead starts from the positive binding postof the second dynamo. The lamps or other appliances are calculated for the potentialdifference of a single dynamo. They are arranged between the neutralwire and the laterals, giving as even a disposition as possible to thetwo laterals. Fig. 336. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE. If evenly arranged and all burning or using current, no current goesthrough the neutral wire. If all the lamps situated on one lateral areon open circuit all the current goes through the neutral wire. In othercases the neutral wire receives the excess of current only. The advantages of the system are that it uses smaller wire than the twowire system for lamps of the same voltage. If lamps of double thevoltage were used the two wire system would be most economical. 540 STANDARD ELECTRICAL DICTIONARY. Four wire and five wire systems have been more or less used, based onidentical considerations, and involving in each case the coupling ofthree or of four dynamos respectively, or else employing a dynamo withspecial armature connections to give the requisite three-fold orfour-fold division of total potential. In the five wire system the totalvoltage is four times that of a single lamp, the lamps are arranged fourin series across the leads and the central wire is the only one that canbe considered a neutral wire. When lamps are burning entirely from threeside-leads they constitute a sort of three wire system by themselves, and their central wire may for the time be a neutral wire. In some of the three wire mains, especially in the larger sizes, theneutral wire is made of much smaller section than that of a lateralconductor, because in extensive districts it is practically impossiblethat the current should be concentrated in the neutral wire. Throw. In a galvanometer the instantaneous deflection of the needle when thecontact or closing of the circuit is instantaneous, or when thedischarge is completed before the needle begins to move. The throw ofthe needle is the datum sought when the ballistic galvanometer is used. Synonym--Elongation. Throw-back Indicator. A drop annunciator, whose shutter or drop is electrically replaced. Thrust-bearings. Bearings to support the end-thrust or push of a shaft. In disc armatureswhere the field-magnets attract the armatures in the direction of theiraxis of rotation, thrust-bearings have to be provided. In ordinarycylinder or drum armatures end-thrust is not applied, as a little endmotion to and fro is considered advantageous as causing more even wearof the commutator surface. Thunder. The violent report which, as we hear it, succeeds the lightning flash instormy weather. It is really produced simultaneously with the lightningand is supposed to arise from disturbance of the air by the discharge. The rolling noise has been attributed to successive reflections betweenclouds and earth, and to series of discharges reaching the ear fromdifferent distances and through air of varying density. The subject isobscure. By timing the interval from lightning flash to the report ofthe thunder an approximate estimate of the distance of the seat ofdischarge can be made. The first sound of the thunder should be timed. An almost concurrence of thunder and lightning indicates immediateproximity of the discharge. [Transcriber's note: The speed of sound at sea level is about 5 secondsper mile. ] Ticker. A colloquial name for a stock or market report automatic printingtelegraph, which prints its quotations and messages on a long tape. 541 STANDARD ELECTRICAL DICTIONARY. Time Constant. (a) When current is first turned into a circuit of considerableself-induction it is resisted rather by the inductance than by theresistance. It is governed by the ratio of resistance and self-inductionand this factor represents the time which it takes for the current toreach a definite fraction of its final strength. This fraction is(2. 7183 - 1)/2. 7183 or 0. 63. 2. 7183 is the base of the Napierian systemof logarithms. Thus if in any circuit we divide the inductance inhenries by the resistance in ohms, the ratio gives the time-constant ofthe circuit, or it expresses the time which it will take for the currentto reach 0. 63 of its final value. (b) In a static condenser the time required for the charge to fall to1/2. 7183th part of its original value. Time Cut-outs. Cut-outs which automatically cut storage batteries out of the chargingcircuit when they are sufficiently charged. Time-fall. In a secondary battery the decrease with use of electromotive forcemaintained by a primary or secondary battery. As the battery becomesspent its voltage falls. The conditions of the fall are represented byits discharging curve. (See Curve, Discharging. ) Time-reaction. A term in electro-therapeutics; the period of time occupied in thepassage of the effects of an electric current from nerve to muscle. Time-rise. In a secondary battery the increase of electromotive force producedduring the charging process. Its rate and conditions are graphicallyshown in the charging curve. (See Curve, Charging. ) Tin. A metal; one of the elements; symbol, Sn; atomic weight, 117. 8;equivalent, 58. 9 and 29. 5; valency, 2 and 4; specific gravity, 7. 3. It is a conductor of electricity. Relative resistance, compressed, (Silver = 1) 8. 784 Specific resistance at 0° C. (32° F. ), 13. 21 microhms. Resistance of a wire at 0° C. (32° F. ), (a) 1 foot long, weighing 1 grain, 1. 380 ohms. (b) 1 foot long, 1/1000 inch thick, 79. 47 " (c) 1 meter long, weighing 1 gram, . 9632 " (d) 1 meter long, 1 millimeter thick, . 1682 " Resistance of a 1 inch cube at 0° C. (32° F. ), 5. 202 microhms. Percentage of variation in resistance per degree C. (1. 8° F. ), at about 20° C. (68° F. ), . 0365 Electro-chemical equivalent (hydrogen = . 0105), . 619 mgs. . 310 " 542 STANDARD ELECTRICAL DICTIONARY. Tinnitus, Telephone. A nervous affection of the ear, of the order of professional cramp; itis attributed to too much use of the telephone. Tin Sounders. A recent addition to the single needle telegraph. (See Telegraph, SingleNeedle. ) It consists of small tin plates, cut and bent, and so fitted inpairs to the instrument, that the needle as deflected strikes one or theother on its right and left hand movements. The sounders can be made togive sufficiently distinctive sounds to make sound-reading, q. V. , possible. Commercial tin plate, which is really tinned iron, seems togive the best results. Fig. 337. TIN SOUNDERS. Tissandier's Solution. A solution for bichromate batteries. It is composed as follows: Water, 100 parts by weight potassium bichromate, 16 parts 66° sulphuric acid, 37 parts. Tongue of Polarized Relay. The German silver extension of the vibrating or oscillating member of apolarized relay, corresponding to the armature of an ordinary relay. Tongue of Polarized Relay, Bias of. In a Siemens' polarized relay the pole pieces are adjustable so thatthey may be brought nearer to or withdrawn from the tongue. One of thepoles is adjusted so as to be nearer the tongue. This one-sidedadjustment is the bias. Its effect is that when the relay is unexcitedthis pole attracts the armature so that it normally is drawn towards it. This ensures the normal contact of the tongue either with the contactpoint, or with the insulated stop piece or adjustment screw. Withoutbias the armature remains in contact with or drawn towards whicheverpole it was last attracted to. In its usual use a bias is given it. Top, Magnetic. A toy illustrating magnetic attraction. It consists of a disc or body oflead or other material, through which a magnetized steel spindle pointedat its lower end is thrust. A number of short pieces of iron wire areused with it. It is spun like an ordinary top upon the point of thespindle and one of the pieces of iron wire is laid by the side of itspoint. As it turns the magnetic adherence causes the piece of wire to becarried along in one direction by the rotation of the spindle, until theend is reached, when it goes over to the other side of the spindle andtravels back again. By using bent pieces of wire of various shapes the most curious effectsare produced. Circles and S shaped pieces give good effects. To increasethe mysterious effect covered iron wire (bonnet wire) may be employed. Fig. 338. MAGNETIC TOP. 543 STANDARD ELECTRICAL DICTIONARY. Torpedo, Electric. (a) A fish, the Raia Torpedo, which possesses the power of givingelectric shocks. (See Ray, Electric. ) (b) An instrument of war; a torpedo whose operations include electricaldischarge or other electric function or factor of operation. Torpedo, Sims-Edison. A torpedo driven by an electric motor, and also steered by electricity. Its motions are all controlled from the shore. The torpedo proper iscarried some distance below the surface of the water by a vesselimmediately above it, from which it is suspended by two rigid bars. Inthe torpedo is a cable reel on which the conducting cable is disposed. An electric motor and controlling gear are also contained within thetorpedo. In its front the explosive is placed. It is driven by a screwpropeller actuated by the electric motor. As it moves it pays out cableso that it has no cable to draw after it through the water, the cablelying stationary in the water behind it. This avoids frictionalresistance to its motion. The maintenance of the torpedo at a properdepth is one of the advantages of the system. 544 STANDARD ELECTRICAL DICTIONARY. Torque. A force tending to produce torsion around an axis. An example is thepulling or turning moment of an armature of an electric motor upon itsshaft. It is often expressed as pounds of pull excited at the end of alever arm one foot long. The expression is due to Prof. James Thompson, then of the University ofGlasgow. "Just as the Newtonian definition of force is that which produces ortends to produce motion (along a line), so torque may be defined as thatwhich produces or tends to produce torsion (around an axis). It isbetter to use a term which treats this action as a single definiteentity than to use terms like 'couple' and 'moment, ' which suggest morecomplex ideas. " (S. P. Thompson. ) A force, acting with radius r gives a torque equal to f X r ; f and rmay be expressed in any units. S. P. Thompson gives the followingequivalents : To reduce dyne-centimeters to gram centimeters, divide by 981 dyne-centimeters to meter-kilograms divide by 981E5 dyne-centimeter, to pound-feet divide by 13. 56E6 pound-feet to meter-kilograms divide by 7. 23 In each of these compound units the first unit is the force and thesecond unit is the radius or lever arm of the torque. Synonyms--Turning Moment--Moment of Couple--Axial Couple--AngularForce--Axial Force. Torsion Balance, Coulomb's. Originally an apparatus in which electrostatic attraction or repulsionis measured against the torsion of a filament, often of silk-worm cocoonfibre. It consists in one form of a cylindrical glass vessel in which alight shellac needle is suspended horizontally by a fibre. This needlecarries at one end a gilded disc or sphere and is suspended by a finewire, or filament. A proof plane, q. V. , is excited by touching it tothe body under trial; it is then inserted in the case. The disc on theneedle is first attracted and then repelled. The position finally takenby the needle is noted. The force of torsion thus produced is determinedby twisting the filament by the torsion head on the top of the apparatusso as to move the needle a certain distance towards the proof plane. Themore the torsion-head has to be turned to carry the needle through aspecified arc the greater is the torsion effected or the greater is therepulsion exerted, The torsional force of a wire is proportional to theangle of torsion; this gives the basis for the measurement. With magnetic needle it is used to measure magnetic repulsion andattraction. The best material for the filament is quartz, but theinstrument is not very much used. Torsion Galvanometer. A galvanometer in which the torsion required to bring the index back tozero, when the current tends to displace it, is made the measure of thecurrent strength or of the electro-motive force. It involves the use ofa torsion head, q. V. , or its equivalent. 545 STANDARD ELECTRICAL DICTIONARY. Torsion Head. The handle and disc from whose undersurface the filament depends towhich the needle or magnet is attached. It is turned to measure thetorsional effect, the edge of the disc being marked or graduated so asto give the angle of deflection required to overcome the effect of thetorque of the needle. Torsion Suspension. Suspension by one or more wires, fibres, or ribands, involving therestitutive force of torsion. Thus fibre suspension, q. V. , is a varietyof torsion suspension. Often a single riband of steel stretched horizontally and secured atboth ends is used, the suspended object, e. G. , a balance beam, beingattached at its own centre to the centre of the stretched riband. Quitesensitive balances are constructed on this principle. It is peculiarlyavailable where an electric current is to be transmitted, as absolutecontact is secured, as in William Thomson's ampere balances. Touch. A term applied to methods of magnetization, as "single touch, " "doubletouch, " or "separate touch, " indicating how the poles of the inducingmagnet or magnets are applied to the bar to be magnetized. Under thetitles of Magnetization the different methods are described. Tourmaline. A mineral; a subsilicate; characterized by the presence of borictrioxide, which replaces aluminum oxide. It is notable for possessingpyro-electric properties. (See Pyro-electricity. ) Tower, Electric. The tower used in the tower system, q. V. , of arc light illumination. Tower System. In electric lighting the system of lighting extended areas by powerfularc lamps placed on high towers, generally of iron or steel frame-work. The lights are thus maintained at a high elevation, giving greateruniformity of illumination than if they were lower, but at the expenseof considerable light which is lost. Sometimes wooden masts are employedinstead of towers. The principle involved is that the intensity of light at any place givenby a source of illumination varies with the square of its distance fromthe place in question. Hence in using strong arc lights it is an objectto have the distances of all parts of the area illuminated at as nearlyuniform distances from the light as possible. An approximation touniformity is secured by placing the lamps at a very high elevation. 546 STANDARD ELECTRICAL DICTIONARY. Transformer. In alternate current lighting the induction coil by which the primarycurrent with high initial electro-motive force is caused to produce asecondary current with low initial electromotive force. A typical transformer consists of a core of thin iron sheets. Theprimary is of comparatively thin wire and often of ten or more times asmany turns as the secondary. The latter is of thicker wire. Where theratio of 10 to 1 as regards number of turns in the primary and secondaryobtains, the initial E. M. F. Of the secondary is one-tenth that of theprimary circuit. The cores are laminated, as described, to avoid the formation ofFoucault currents. The counter-electro-motive force of the transformer when the secondarycircuit is open, prevents any but the slightest current from passingthrough the primary. In proportion as the secondary is closed and itsresistance diminished, as by lighting more lamps in parallel, thecounter-electro-motive force of the transformer falls and more currentpasses through the primary. Fig. 339. FERRANTI'S TRANSFORMER. The economy of the apparatus is in the fact that counter-electromotiveforce reduces current through a conductor without absorbing any energy. A resistance coil cuts down a current, but absorbs energy equal to thecurrent multiplied by the potential difference between the terminals ofthe coil. This electric energy is converted into heat energy and iswasted. But the counter-electromotive force of a transformer is exertedto reduce current without production of heat and with little waste ofenergy. This is one of the advantages of the alternating current systemof distribution of electric energy. The object of a transformer being to secure safety to the person or tolife by the separation of the high potential primary or street circuit, and the low potential house circuit, any contact of the two circuits inthe converter is a source of danger. Special care should be taken toensure absence of leakage, as it is termed. Mica or other insulation issometimes employed to prevent the wires from coming in contact bypiercing or sparking with the core and with each other. 547 STANDARD ELECTRICAL DICTIONARY. Transformer, Commuting. A type of continuous current transformer, resembling a dynamo witharmature and field both stationary, but with revolving commutator, bywhich the magnetic polarity of a double wound armature is made torotate. This secures the desired action, of a change or lowering ofpotential. Transformer, Continuous Alternating. An apparatus for transforming a continuous into an alternating currentor the reverse. The combination of a continuous current dynamo with analternating current one is sometimes employed. It is a form of motordynamo. Another type is a regular dynamo with ordinary commutator and with, inaddition thereto, two, three or four contact rings, connecting to asmany symmetrically disposed points in the winding of the armature. Thiswill give out or receive alternating currents of two, three or fourphases according to the number of collecting rings. One winding servesfor both alternating and continuous currents. Transformer, Continuous Current. A machine of the dynamo type for changing the potential of a circuit. Inone form two armatures are mounted on one shaft in a single field or inseparate fields; one is a motor armature driven by the original current;the other generates the new current. This is a motor dynamo. In 1874Gramme constructed a machine with ring armature with two windings, ofcoarse and fine wire respectively, and with independent commutators. Such dynamo could transform currents up or down. Continuous current transformers have attained an efficiency of 83 percent. At full load, and of 75 per cent. At half load. Owing to thebalancing of the self-inductions of the two windings these machines donot spark. As the driven and driving parts are contained in one rotatingpart their friction is very slight. Transformer, Core. A transformer wound upon an enclosed core, such as the hedgehogtransformer (see Transformer, Hedgehog), or common induction coil. 548 STANDARD ELECTRICAL DICTIONARY. Transformer, Hedgehog. An induction coil transformer whose iron core is composed of a bundle ofiron wires, which after the wire windings are in place have their endsspread out to reduce to some extent the reluctance of the circuit, whichat the best is high, as the air acts as the return circuit. This transformer has a low degree of hysteresis; and its efficiency forvery small loads or for no load is superior to that of the closedmagnetic circuit transformer. Fig. 340. SWINBURNE'S HEDGEHOG TRANSFORMER. Transformer, Multiple. A transformer connected in parallel with others between the two leads ofthe primary circuit. The term refers to the connection only and not toany peculiarity of the transformer itself. Transformer, Oil. A transformer with oil insulation. The advantage of this insulation isthat if pierced it at once closes, so that no permanent injury ensues. It is a self-healing form of insulation. Transformer, Series. Transformers connected in series upon the primary circuits. The term, like "multiple transformers, " only applies to the connection, not to thetransformer. Series transformers are but little used. Transformer, Shell. A transformer with its iron core entirely outside of and enclosing theprimary and secondary winding. It may be made by the use of outer ironwire windings as core. Transformer, Welding. The transformer used for electric welding. (See Welding, Electric. ) Itis a transformer with very long primary and exceedingly short and thicksecondary. It is used with the alternating current in the primary, andproduces in the secondary circuit which includes the bars to be welded avery low potential difference. Owing to the very low resistance of the secondary circuit this lowelectro-motive force produces a very strong current, which develops therequisite heat. The same type of transformer is used for brazing andsimilar purposes. 549 STANDARD ELECTRICAL DICTIONARY. Transmitter. In general electric phraseology, any instrument which produces signalsto be transmitted through a line or circuit is a transmitter. Thus theMorse key in telegraphy or the Blake transmitter in telephony areexamples of such. Transmitter, Carbon. A form of microphone used as a telephone transmitter. (See CarbonTelephone. ) Transposing. A method of laying metallic circuits for telephoning. The wires at shortintervals are crossed so that alternate sections lie on opposite sidesof each other. It is done to avoid induction. Transverse Electro-motive Force. Electro-motive force in a substance in which electric displacement istaking place, produced by a magnetic field. It is sometimes assigned asthe cause of the Hall effect, q. V. Trimmer, Brush. A shears for cutting off evenly and squarely the ends of copper dynamobrushes. The brushes when uneven from wear are removed from the brushholders, and their ends are sheared off in the trimmer. Trolley. A grooved metallic pulley or set of pulleys which runs along an activewire of a circuit, a lead from which trolley goes to earth or connectswith another wire, so that the trolley takes current generally foroperating a street car motor placed upon the circuit leading from it; arolling contact with an electric lead. Trolleys are principally used on electric railroads, and are nowuniversally of the sub-wire system, being at the end of a pole which isinclined backward and forced upward by springs, so as to press thetrolley against the bottom of the wire. Thus the trolley does notincrease the sagging of the wire, but tends to push it up a little inits passage. Trolley, Double. A trolley with two rollers or grooved wheels, placed side by side, andrunning on two parallel leads of wire. It is adapted to systemsemploying through metallic trolley lines with the motors in multiplearc, connecting or across the two leads. Trolley Section. An unbroken or continuous section of trolley wire. Trouvé's Solution. An acid exciting and depolarizing solution for a zinc-carbon battery. Its formula is as follows: Water, 80 parts; pulverized potassiumbichromate, 12 parts; concentrated sulphuric acid, 36 parts; all partsby weight. The pulverized potassium bichromate is added to the water, and the acid is added slowly with constant stirring. As much as 25 partspotassium bichromate may be added to 100 parts of water. The heatingproduced by the acid and water dissolves nearly all the potassium salt. Use cold. 550 STANDARD ELECTRICAL DICTIONARY. True Contact Force. A species of electro-motive force whose existence is supposed to beproved by the Peltier effect. The lowering in temperature of a contactof dissimilar metals is attributed to a force that helps the current onits way if in the direction of thermo-current proper to the junction andopposing it if in the reverse. The true contact force is taken toexplain this phenomenon; thermo-electric force cannot, as there is noheat or cold applied to the junction. Trumpet, Electric. An apparatus consisting of a vibrating tongue, kept in motion byelectricity as in the buzzer, q. V. , placed in the small end of atrumpet-shaped tube. Trunking Switchboard. A telephone switchboard arranged in sections, which sections areconnected by trunk lines, through which trunk lines the desiredconnectionsare made. Trunk Lines. In telephone distribution systems, the lines connecting differentstations, or different sections of a switch-board and used by anyonerequiring such connections; one trunk line answers for a number ofsubscribers. Tube, Electric. A tube of glass around which is pasted a series of tinfoil circles, diamonds, or little squares, or other form of interrupted conductor. Thepieces generally are placed in the line of a spiral. When a staticdischarge of electricity takes place along the conductor a row of brightsparks is produced at the breaks in the conductor. These by reflectionare multiplied apparently, and a beautiful effect of intersecting orcrossing spirals of sparks is presented. The experiment is in line with the luminous pane and lightning jar, andis used merely as a demonstration, or lecture experiment. Synonym--Luminous Tube. Tubular Braid. A braid woven of tissue or worsted, and tubular or hollow. Its object isto provide a covering which can be drawn over joints in covered wires. In making the joint the ends of the wires are necessarily bared, and ashort piece of tubular braid is used for covering them. It is drawn byhand over the joint. Turns. An expression applied to the convolutions of wire in a solenoid, electro-magnet, or other apparatus or construction of that kind. A turnindicates a complete encircling of the core or axis of the object. Thusa wire wound five times around a bar gives five turns. While this is its primary meaning the term if compounded may refer tovirtual turns. Thus an ampere-turn means one ampere passing through oneturn. But ten ampere-turns may mean ten amperes passing through tenturns, five amperes passing through two turns, and so on. This use isanalogous to a dimension of length in a compound word, as foot-pound. [Transcriber's note: "But ten ampere-turns may mean ten amperes passingthrough ONE turn or one ampere through ten turns, and so on. "] There may be a number of kinds of turns qualified by descriptiveadjectives, as series-turns, the turns of wire in a series circuit of acompound dynamo. In the same way there are shunt-turns. If seriesampere-turns or shunt ampere-turns are meant the word ampere should beincluded. 551 STANDARD ELECTRICAL DICTIONARY. Turns, Dead, of a Dynamo. The rotations of a dynamo armature while it is building itself up orexciting itself. The expression is a bad one, as it is likely to beconfounded with the dead turns of armature wire. Turns, Primary Ampere-. The ampere-turns in a primary circuit of an induction coil ortransformer. In an electric welding transformer, or in the transformerused in the alternating current system, where efficiency is an importantelement, the ampere-turns in primary and secondary for an efficiency of100 per cent. Should be equal. In the case of an experimental inductioncoil other considerations outweigh that of mere efficiency. Insulation, including security from piercing, and the production of as long a sparkas possible, are, in these cases, the controlling consideration. [Transcriber's note: A 100 per cent efficient transformer is impossible, but over 99 per cent is common. At room temperature there is always somelost flux, eddy currents and resistive losses. ] Turns, Secondary Ampere-. The ampere-turns on the secondary circuit of an induction coil ortransformer. These depend on the path provided for the current. If ofnegligible inductance, such as a number of incandescent lamps wouldprovide, the ampere-turns should be equal to those of the primary coil. (See Turns, Primary Ampere. ) Typewriter, Electric. A typewriter in which the work of printing or of pressing the type facesagainst the paper, or printing ribbon, is done by electro-magneticattraction. The keys close electric circuits, throwing theelectro-magnetic action into play. This involves the use of electricityfor what is ordinarily only a mechanical process. The strength of theimpression, however, is independent of the touch of the operator. It hasnot come into very extensive use. [Transcriber's note: IBM introduced widely used electric typewriters in1935. ] Ultra-gaseous Matter. Gas so rarefied that its molecules do not collide or very rarely do so. Experiments of very striking nature have been devised by Crookes andothers to illustrate the peculiar phenomena that this matter presents. The general lines of this work are similar to the methods used inGeissler tube experiments, except that the vacua used are very muchhigher. When the vacuum is increased so that but one-millionth of the originalgas is left the radiant state is reached. The molecules in their kineticmovements beat back and forth in straight lines without colliding, orwith very rare collisions. Their motions can be guided and renderedvisible by electrification. A tube or small glass bulb with platinumelectrodes sealed in it, is exhausted to the requisite degree and ishermetically sealed by melting the glass. The electrodes are connectedto the terminals of an induction coil or other source of high tensionelectrification. The molecules which come in contact with a negativelyelectrified pole are repelled from it in directions normal to itssurface. They produce different phosphorescent or luminous effects intheir mutual collisions. Thus if they are made to impinge upon glass, diamond or ruby, intensephosphorescence is produced. A piece of platinum subjected to molecularbombardment is brought to white heat. A movable body can be made to moveunder their effects. Two streams proceeding from one negative pole repeleach other. The stream of molecules can be drawn out of their course bya magnet. The experiments are all done on a small scale in tubes and bulbs, resembling to a certain extent Geissler tubes. [Transcriber's note: These effects are caused by plasma--ionized gas andelectrons. ] 552 STANDARD ELECTRICAL DICTIONARY. Unbuilding. The loss of its charge or excitation by a self-exciting dynamo. It isthe reverse of building-up. The latter indicates the exciting of thefield by the action of the machine itself; the former the spontaneousloss of charge on open circuit or from other cause. Underground Conductor. An electric conductor insulated and placed under the surface of theearth, as distinguished from aerial conductors. Underground Electric Subway. A subway for the enclosing of electric telegraph and other conductorsunder the surface, generally in the line of streets, to do away withtelegraph poles and aerial lines of wire. Many systems have beendevised. The general type includes tubes called ducts in sets, calledconduits, bedded in concrete or otherwise protected. Every two or threehundred feet the sets lead into a cistern-like cavity called a manhole. The insulated wires or cables, generally sheathed with a lead alloy areintroduced into the tubes through the man-holes. A rope is first fedthrough the tube. To do this short rods which screw together aregenerally employed. One by one they are introduced, and each end one isscrewed to the series of rods already in the duct. When the end of theduct is reached the rope is fastened to the last rod, and the rods arethen drawn through, unscrewed one by one and removed, the rope followingthem. By means of the rope a windlass or capstan may be applied to drawthe cable into the duct. At least at every second man-hole the cableshave to be spliced. Each cable may contain a large number of conductors of small size fortelephoning, or a smaller number for electric light and power. Thetendency is now to separate the different classes of wires in importantlines, placing the heavier wires on one side of the street and thetelephone and telegraph wires on the other. This of course necessitatestwo separate conduits. The advantage of underground distribution affects not only theappearance of streets in doing away with unsightly telegraph poles, butit also removes an element of danger at fires. Aerial wires interferegreatly with the handling of ladders at fires, and expose the firemenwho attempt to cut them to danger to their lives from shock. 533 STANDARD ELECTRICAL DICTIONARY. Unidirectional. Adj. Having one direction as a "unidirectional current" or "unidirectionalleak. " The term is descriptive, and applicable to many cases. Uniform. Adj. Unvarying; as a uniform potential difference, uniform current orconductor of uniform resistance per unit of length. The term isdescriptive, and its application and meaning are obvious. Uniform Field of Force. A field of evenly distributed force; one in which the number of lines offorce per unit of area of any equipotential surface is the same. Unipolar. Adj. Strictly speaking this term means having only one pole, and is appliedto magnets, armatures and the like. In its use a solecism is involved, for there is no such condition possible as unipolar magnetism ordistribution of magnetism. An example of its use is shown in unipolarmagnets. (See Magnet, Unipolar. ) Unipolar Armature. An armature of a unipolar dynamo; an armature whose windingscontinuously cut the lines of force about the one pole, and hence whosepolarity is unchanged in its rotation. Unipolar Current Induction. Current induction produced by moving a conductor through a magneticfield of force so that it always cuts the lines in similar relation toitself. Thus it produces a constant current through its own circuit, ifa closed one, and no commutator is required. As this case always inpractice amounts to the cutting of lines of force in the neighborhood ofa single pole the term unipolar is employed to designate the action. The simplest representation of unipolar induction is the rotating of aconductor around the end of a bar magnet, its axis of rotationcorresponding with the axis of the magnet. Unipolar Dynamo. A dynamo in which one part of the conductor slides on or around themagnet, so as always to cut lines of force near the same pole of themagnet. Unit. A directly or indirectly conventional and arbitrary quantity, in termsof which measurements of things with dimensions expressible in thechosen units are executed. Thus for length the c. G. S. Unit is the centimeter; the B. E. Unit isthe foot. 554 STANDARD ELECTRICAL DICTIONARY. Unit, Absolute. A unit based on the three fundamental units of length, mass and time. These units are the centimeter, gram and second. Each one in itself maybe termed a fundamental absolute unit. The system of such units istermed the centimeter-gram-second system. Unit, Angle. A factor or datum in angular velocity, q. V. It is the angle subtendedby a portion of the circumference equal in length to the radius of thecircle. It is equal very nearly to 57. 29578° or 57° 17' 44. 8". Unit, B. A. This term, while logically applicable to any of the British Associationunits, is often restricted to the ohm as formerly defined by the BritishAssociation, the B. A. Unit of Resistance, q. V. Unit, Fundamental. The three units of length, mass and time, the centimeter, gram andsecond, are termed fundamental units. On them is based the absolutesystem of units, and on multiples of them the practical system of units. Unit Jar. A Leyden jar which is used as a unit of measure of charge. It consists of a Leyden jar about 4 inches long and 3/4 inch diameter, with about 6 square inches of its outer and the same of its innersurface coated with tinfoil. It is placed between a source ofelectricity and a larger jar or battery of jars which is to be charged. The inner coating connects with the machine; the outer coating with thejars to be charged. Short conductors terminating in knobs connect withinner and outer coatings, and the knobs are adjusted at any desireddistance apart. By the charging operation the large jar or battery of jars receives acharge by induction, and the charge of the small jar is at first equalto this quantity. After a while a spark passes from knob to knob, discharging the small jar. This indicates the reception by the largejars of the quantity of electricity represented by the charge of thesmall jar. The charging goes on, and for every spark approximately thesame quantity of electricity is received by the larger jars. The sparking distance m is directly proportional to the quantity ofelectricity, and inversely proportional to the area of coated surface, or is proportional to the potential difference of the two coats. This isonly true for short sparking distance, hence for accuracy the knobsshould be adjusted not too far from each other. 555 STANDARD ELECTRICAL DICTIONARY. Unit of Supply. A commercial unit for the sale of electric energy, as definedprovisionally by the English Board of Trade; 1, 000 amperes flowing forone hour under an E. M. F. Of 1 volt; 3, 600, 000 volt-coulombs, or 1, 000watt-hours, are its equivalent. It is equal to 1000/746 = 1. 34 electrichorse power. Synonym--Board of Trade Unit. [Transcriber's note: Now called a kilowatt-hour. ] Units, Circular. A system of units of cross-sectional area, designed especially for usein describing wire conductors. The cross-sectional area of such isuniversally a circle, and the areas of two wires of different sizes varywith the square of their radii or diameters. Hence if the area of acircle of known diameter is determined it may be used as a unit for thedimensions of other circles. Any other circle will have an areaproportioned to the area of the unit circle, as the squares of thediameters are to each other. In practise the commonest circular unit is the circular mil. This is thearea of a circle one mil, 1/1000 inch, in diameter and is equal to. 0000007854 square inch. A wire two mils in diameter has an area of fourcircular mils; one ten mils in diameter has an area of one hundredcircular mils. Thus if the resistance of a given length of wire 1 mil in diameter isstated, the corresponding resistance of the same length of wire of thesame material, but of other diameter, is given by dividing the firstwire's resistance by the square of the diameter in mils of the wire inquestion. As it is a basic unit, most conveniently applied by multiplication, thesmaller units are used; these are the circular mil, and circularmillimeter. Units, Derived. Units derived by compounding or other processes, from the threefundamental units. Such are the units of area, volume, energy and work, momentum and electric units generally. In some cases the dimensions ofthe derived unit may reduce to those of a simple unit as inductancereduces to length, but the unit, as deduced from the fundamental ones, is still a derived unit. Units, Practical. A system of units employed in practical computation. The absolute units, especially in electricity, have been found too large or too small, andthe attempt to make them more convenient has resulted in this system. Itis based on exactly the same considerations as the absolute system ofunits, except that multiples of the original fundamental units oflength, mass, and time have been taken as the base of the new system. These basic units are multiples of the fundamental units. They are thefollowing: The unit of length is 1E9 centimeters; the unit of mass is1E-11 gram; the unit of time remains 1 second. While this has conduced to convenience in giving better sized units, micro- and mega-units and other multiples or fractions have to be used. The following are the principal practical electric units: Electrostatic Electromagnetic C. G. S Units. C. G. S. Units. Intensity-Ampere equal to 3E9 1E-1Quantity-Coulomb " 3E9 1E-1Potential-Volt " (1/3)* E-2 1E8Resistance-Ohm " (1/9)* E-11 1E9Capacity-Farad " 9E11 1E-9 556 STANDARD ELECTRICAL DICTIONARY. Universal Battery System. A term in telegraphy. If several equal and high resistance telegraphiccircuits are connected in parallel with each other from terminal toterminal of a battery of comparatively low resistance each circuit willreceive the same current, and of practically the same strength as ifonly one circuit was connected. This is termed the universal batterysystem. It is a practical corollary of Ohm's law. The battery being ofvery low resistance compared to the lines the joining of several linesin parallel practically diminishes the total resistance of the circuitin proportion to their own number. Thus suppose a battery of ten ohmsresistance and ten volts E. M. F. Is working a single line of onehundred ohms resistance. The total resistance of the circuit is then onehundred and ten ohms. The total current of the circuit, all of which isreceived by the one line is 10/110 = . 09 ampere, or 90 milliamperes. Nowsuppose that a second line of identical resistance is connected to thebattery in parallel with the first. This reduces the external resistanceto fifty ohms, giving a total resistance of the circuit of sixty ohms. The total current of the circuit, all of which is received by the twolines in equal parts, is 10/60 = . 166 amperes. But this is equallydivided between two lines, so that each one receives . 083 ampere or 83milliamperes; practically the same current as that given by the samebattery to the single line. It will be seen that high line resistanceand low battery resistance, relatively speaking, are required for thesystem. For this reason the storage battery is particularly available. The rule is that the resistance of the battery shall be less than thecombined resistance of all the circuits worked by it. Unmarked End. The south-seeking pole of a magnet, so called because the other end, called the marked end, is usually marked with a scratch or notch by themaker, while the south pole is unmarked. V. (a) Symbol for velocity. (b) Symbol or abbreviation for volume. (c) Symbol or abbreviation for volt. 557 STANDARD ELECTRICAL DICTIONARY. V. A. Symbol or abbreviation for voltaic alternatives, q. V. Vacuum. A space destitute of any substance. The great pervading substance is ingeneral sense the atmosphere. It is the gaseous mixture which surroundsand envelopes the earth and its inhabitants. It consists of a simplemixture of oxygen, 1 part, nitrogen, 4 parts, with 4 to 6 volumes ofcarbonic acid gas in 10, 000 volumes of air, or about one cubic inch toone cubic foot. It presses with a force of about 14. 7 lbs. Per squareinch under the influence of the force of gravity. The term vacuum inpractise refers to any space from which air has been removed. It may beproduced chemically. Air may be displaced by carbonic acid gas and thelatter may be absorbed by caustic alkali or other chemical. The air maybe expelled and the space may be filled with steam which is condensed toproduce the vacuum. Of course in all cases the space must be included inan hermetically sealed vessel, such as the bulb of an incandescent lamp. But the universal method of producing a vacuum is by air pumps. Anabsolute vacuum means the entire absence of gas or air, something almostimpossible to produce. A high vacuum is sometimes understood to mean onein which the path of the molecules is equal in length to the diameter ofthe containing vessels, as in Crookes' Radiometer and other apparatusfor illustrating the radiant condition of matter. The air left afterexhaustion is termed residual air or residual atmosphere. [Transcriber's note: Dry air is about . 78 nitrogen, . 21 oxygen, . 01argon, . 00038 carbon dioxide, and trace amounts of other gases. Argonwas suspected by Henry Cavendish in 1785. It was discovered in 1894 byLord Rayleigh and Sir William Ramsay. ] Vacuum, Absolute. A space free of all material substance. It is doubtful whether anabsolute vacuum has ever been produced. Vacuum, High. An approximate vacuum, so nearly perfect that the molecules of theresidual gas in their kinetic motions rarely collide, and beat back andforth between the walls of the containing vessel, or between any solidobject contained in the vessel and the walls of the vessel. The gas insuch a vacuum is in the radiant or ultra-gaseous state. (SeeUltra-gaseous Matter. ) Vacuum, Low. A vacuum inferior to a high vacuum; a vacuum in which the moleculescollide with each other and do not move directly from side to side ofthe containing vessel. Vacuum, Partial. A space partially exhausted of air so as to contain less than an equalvolume of the surrounding atmosphere. It really should come below a lowvacuum, but is often treated as synonymous therewith. Vacuum, Torricellian. The vacuum existing above the mercurial column in a barometer tube. Theprinciple of this vacuum is applied in the Geissler and other air pumps. (See Pump, Geissler--Pump, Sprengel--Pump, Swinburne. ) 558 STANDARD ELECTRICAL DICTIONARY. Valency. The relative power of replacing hydrogen or combining therewithpossessed by different elements; the number of atomic bonds belonging toany element. Thus oxygen has a twofold valency, is bivalent or is adyad, and combines with two atoms of hydrogen because the latter has aunitary atomicity, is monovalent or is a monad. Valve, Electrically Controlled. A valve which is moved by or whose movements are regulated byelectricity. In the block system of railroad signaling the semaphores are worked byweights and pneumatic cylinders and pistons. The valves for admitting orreleasing the compressed air are operated by coil and plunger mechanism. There are many other instances of the control of valves by the electriccurrent. Vapor Globe. A protecting glass globe surrounding an incandescent lamp, when the lampis to be used in an atmosphere of explosive vapor, as in mines orsimilar places; or when in a place where it is exposed to dripping waterwhich would break the hot lamp bulb if it fell upon it. Variable Period. The period of adjustment when a current is started through a conductorof some capacity. It is the period of duration of the variable state, q. V. , in a conductor. As indicated in the next definition in a cable ofhigh electrostatic capacity a variable period of nearly two minutes mayexist. This indicates the retardation in signaling to be anticipated incables and other lines of high capacity. Variable State. When an electric circuit is closed the current starts through theconductor with its full strength from the point of closure, and advanceswith a species of wave front so that some time elapses before it attainsits full strength in the most distant parts of the conductor, owing toits having to charge the conductor to its full capacity at the givenpotential. The state of the line while the current thus varies is calledthe variable state. A long telegraph line when a message is being transmitted may be alwaysin the variable state. The current at the receiving end may never attainits full strength. In the case of such a conductor as the Atlantic cable, 108 seconds wouldbe required for a current to attain 9/10 of its full strength at thedistant end, and but 1/5 second to attain 1/100 of its final value. During the period of increase of current the variable state exists. Variation of the Compass. The declination of the magnetic needle. (See Elements, Magnetic. ) As thedeclination is subject to daily, annual and secular variations, it isunfortunate that this term is synonymous with declination. Thus thevariation of the compass means its declination, while there is also thevariation of the declination and of other elements. The term variationof the compass is more colloquial than the more definite expression"declination, " or "magnetic declination. " 559 STANDARD ELECTRICAL DICTIONARY. Variometer. An apparatus used in determining the relative values of the horizontalcomponent of the earth's magnetic field in different places. Varley's Condenser. A static condenser whose conducting surfaces are platinum electrodesimmersed in dilute sulphuric acid. When the potential difference is1/50th that of a Daniell's cell, two square inches of platinum have acapacity equal to that of an air condenser whose plates have an area of80, 000, 000 square inches, and separated 1/8th of an inch from eachother. As the E. M. F. Increases the capacity also increases. Varley's Resistances. Variable resistances formed of discs of carbonized cloth, q. V. , piledup, and pressed together more or less firmly to vary the resistance asdesired. Varnish. A glossy transparent coating of the nature of paint, applied as aprotective, or ornamental coating to objects. Varnish, Electric. Alcoholic or etherial varnishes are the best for electrical apparatus. They dry quickly and perfectly, and tend to form surfaces unfavorable tothe hygroscopic collection of water. Sealing wax dissolved in alcohol, or shellac dissolved in the same solvent are used for electricalapparatus, although the first is rather a lacquer than a varnish. Etherial solution of gum-copal is used to agglomerate coils of wire. Itis well to bake varnished objects to harden the coating. Varnish, Red. A solution of sealing wax in 90 per cent. Alcohol. It is best made thinand applied in several coats, each coat being allowed to dry perfectlybefore the next is applied. It is often seen on Leyden jars. It is aprotector from surface leakage. Vat. A vessel for chemical or other solutions. A depositing vat is one inwhich a plating solution is worked, for the deposition of electroplateupon articles immersed in the liquid, and electrolyzed by an electriccurrent. Velocity. The rate of motion of a body. It is usually expressed in distancetraversed per second of time. The absolute unit is one centimeter persecond or kine. The foot per second is very largely used also. The dimensions of velocity are length (L) divided by time (T) or L/T. Velocity, Angular. Velocity in a circle defined by the unit angle, or the angle whichsubtends a circular arc equal in length to itself. The radius of thecircle traversed by the moving body does not enter into this definition, as the real velocity of the object is not stated. If its angularvelocity and the radius of the path it travels are given its actualvelocity can be deduced. 560 STANDARD ELECTRICAL DICTIONARY. Velocity of Signaling. The speed of transmission of electric signals is affected by the natureof the line, as regards its static capacity, and by the delicacy of thereceiving instruments, which may need a more or less strong current tobe affected. Thus of an original current one per cent. May suffice tooperate a sensitive instrument. This might give almost the velocity oflight, while if the instrument would only respond to the full currentnearly two minutes (see Variable State) might be required for theproduction of a signal. Velocity Ratio. A term applied to the ratios existing between the electrostatic andelectro-magnetic units. If we take as numerators the dimensions of thedifferent qualities in the electrostatic system, and their dimensions inthe electro-magnetic system as denominators, the fractions thus obtainedreduce to expressions containing only velocity or V in some form. Thusif we divide the dimensions of the electrostatic quantity by thedimensions of electro-magnetic quantity the quotient is simply V orvelocity. A like division for potential, electrostatic andelectro-magnetic gives (1/V), and so on. The value of the velocity ratio is very nearly 3E10 (sometimes given as2. 98E10) centimeters per second. This is almost exactly that of light(2. 9992E10 centimeters per second. ) This is one of the proofs of ClerkMaxwell's magnetic theory of light. (See Maxwell's Theory of Light. ) [Transcriber's note: The SI metre was defined in 1983 such that thespeed of light in a vacuum is exactly 299, 792, 458 metres per second orabout 186, 282. 397 miles per second. ] Ventilation of Armature. In a dynamo or motor ventilation of the armature is often provided forby apertures through it in order to prevent heating. This heating iscaused by Foucault currents. By proper disposition of the interior ofthe armature with properly disposed vanes and orifices an action likethat of a fan blower can be produced, which by creating a current of aircools the machine very efficiently. Verticity, Poles of. Points upon the earth's surface where the horizontal component ofmagnetic force disappears, leaving only the vertical component active. The term is derived from the verticity of the dipping needle when overeither of them. 561 STANDARD ELECTRICAL DICTIONARY. Vibration Period. In electrical resonance the period of a vibration in an electricalresonator. The length of this period indicates the quality of theresonator in responding to electrical oscillations by sympatheticvibration. For conductors of small resistance the period is thuscalculated. Let T be the period of one-half a full vibration; L theabsolute coefficient of self-induction expressed in centimeters or inhenries X 10-9; C the electrostatic capacity of the terminals, alsoexpressed in the same unit; v the velocity of light in centimeters persecond. Then we have the formula T = PI * SquareRoot( L * C ) / v [Transcriber's note: If the inductance is in henries and the capacitancein farads, frequency in hertz = 1/(2 * PI * squareRoot( L * C ) )] Vibration, Sympathetic. A vibration in a cord or other body susceptible of elastic vibrationproduced by the vibrations of exactly the same period in a neighboringvibrating body. Thus if two tuning forks are tuned to precisely the samepitch, and are placed near each other, if one is sounded it will startthe other into vibration by sympathy. In electricity its application is found in electric resonanceexperiments. The resonator has a definite period of electric resonance, and is made to give a spark by the exciter of identical period. This isby what may be called electric sympathetic vibration, and is exactlyanalogous to the action of the tuning forks upon each other. Vibrator, Electro-magnetic. The make and break mechanism used on induction coils, or other similarapparatus in which by alternate attractions by and releases from anelectro-magnet an arm or spring is kept in motion. In most cases thework is done by a single magnet, whose armature is attracted to themagnet, when the latter is excited, but against the action of a springwhich tends to pull it away from the magnet. In its motions a make andbreak action is produced, to give the requisite alternations ofattraction and release. Two electro-magnets may be connected so asalternately to be excited and keep an arm carrying a mutual armature invibration, or the same result may be attained by a polarized relay. Themake and break is illustrated under Bell, Electric--Coil, Induction--Anvil. Villari's Critical Value. Magnetization induced or residual in a wire is diminished on stretching, provided that the magnetization corresponds to an inducing force above acertain critical value, known as above; this being (Sir Wm. Thomson)about 24 times the terrestrial intensity. Below that critical valuetension increases the magnetization of a magnetized wire. The effects oftransverse expansive stress are opposed to those of longitudinalstretching. (Daniell. ) Viole's Standard of Illuminating Power. A standard authorized by the International Congress of 1881. It is thelight given by one square centimeter of platinum, melted, but just atthe point of solidification. It is equal to 20 English standard candlesalmost exactly. It has not been very widely accepted, the tendency among photometristsbeing to adhere to the old standards, carcel or candle. It is obviousthat actual use of the Viole would be very inconvenient and wouldinvolve expensive apparatus, difficult to work with. Synonym--Viole. 562 STANDARD ELECTRICAL DICTIONARY. Vis Viva. The kinetic energy of a body in motion; "mechanical energy. " Vitreous Electricity. Positive electricity; the electricity produced on the surface of glassby rubbing it with silk and other substances. (See ElectrostaticSeries. ) The term "positive electricity" should be allowed to supplant it. It isthe analogue and opposite of resinous electricity. Vitriol, Blue. A colloquial or trade name for copper sulphate (Cu SO4). Vitriol, Green. A colloquial or trade name for ferrous sulphate (Fe SO4). Vitriol, White. A colloquial or trade name for zinc sulphate (Zn SO4). Volt. The practical unit of electro-motive force or potential difference. Itmay be referred to various data. An electro-motive force of one volt will cause a current of one ampereto flow through a resistance of one ohm. A condenser of one farad capacity charged with one coulomb will have arise of potential of one volt. The cutting of 100, 000, 000 lines of force per second by a conductorinduces one volt E. M. F. A Daniell's battery gives an E. M. F. Of 1. 07 volts; about the mostfamiliar approximate standard that can be cited. It is equal to 1/300 absolute electrostatic unit. It is equal to 1E8 absolute electro-magnetic units. [Transcriber's note: The SI definition of a volt: The potentialdifference across a conductor when a current of one ampere dissipatesone watt of power. ] Voltage. Potential difference or electro-motive force expressed in volts; as avoltage of 100 volts. Thus voltage may express the electro-motive forceabsorbed in a conductor, while electro-motive force is a term generallyapplied where it is produced, evolved or present in the object. The termvoltage of a lamp expresses simply the volts required, but does notsuggest the possession of electromotive force. 563 STANDARD ELECTRICAL DICTIONARY. Voltage, Terminal. The voltage or potential difference at the terminals of an electriccurrent generator, such as a dynamo, as distinguished from the totalelectro-motive force of the dynamo or generator. In batteries the distinction is not generally made in practice; thetotal electro-motive force of the battery is made the basis ofcalculations. Voltaic. Adj. This adjective is used to qualify a great many things appertaining to orconnected with current electricity. It is derived from Volta, theinventor of the voltaic battery, and now tends to displace the term"galvanic, " formerly in general use. Voltaic Alternatives. A term used in electro-therapeutics or medical electricity to indicatean alternating battery current. Synonym--Alternative current. Voltaic Effect. The potential difference developed by contact of different conductors. It is the basis of the contact theory, q. V. , of electricity, althoughit may be accepted as the expression for a condition of things by thosewho reject the above theory. This potential difference is slight whenthe conductors are separated, but it is calculated that it would beenormous could the metals be so quickly separated as to hold each itsown charge. Thus if a copper and a zinc plate are assumed to be in contact, really1/20000000 centimeter or 1/50000000 inch apart, they may be treated as apair of condenser plates. Being so near, their density of charge, whichis a strongly bound charge, is enormous. If it were possible to separatethem without permitting any discharge, their potential would rise by theseparation, on the principle of Epinus' condenser, q. V. , to such anextent that they would spark through twenty feet of air. (See Volta'sFundamental Experiment. ) Voltaic Electricity. Electricity of low potential difference and large current intensity;electricity such as produced by a voltaic battery; current or dynamicelectricity as opposed to static electricity. Voltameter. In general an apparatus for determining the quantity of electricitypassing through a conductor by measuring the electrolytic action it canperform. Voltameter, Copper. An apparatus which may be of similar construction with the silvervoltameter (see Voltameter, Silver), but in which a copper anode and asolution of copper sulphate are substituted for the silver anode andsilver nitrate solution. One coulomb corresponds to . 329 milligram or. 005084 grain of copper deposited. It is not accepted as of as high astandard as the silver voltameter. The electrodes should be placed half an inch from each other. Two squareplate electrodes may conveniently be used, and not less than two squareinches on each plate should be the area per ampere of current. 564 STANDARD ELECTRICAL DICTIONARY. Voltameter, Differential, Siemens'. A volume or gas voltameter with duplicate eudiometers and pairs ofelectrodes. It is used for determining the resistance of the platinumconductor used in his pyrometer. A current divides between the twovoltameters; in one branch of the circuit the platinum conductor isplaced, in the other a known resistance. The current strength varyinginversely with the resistance, the resistances of the two conductors areinversely proportional to the gas evolved. Voltameter, Gas. A voltameter whose indications are based on the electrolysis of water, made an electrolyte by the addition of sulphuric acid. The gases evolvedare measured. It may take several forms. In one form it is an apparatus consisting of a single eudiometer orgraduated glass tube with upper end closed and its lower end or mouthopen, collecting the mixture of hydrogen and oxygen. In the form shown in the cut three tubes are connected, the side tubesrepresenting eudiometers. For each side tube there is a platinumelectrode. In this apparatus the oxygen and hydrogen are connected inopposite tubes. A is an open tube filled with dilute sulphuric acid. Byopening the cocks on B and C they can both be completely filled withacid. As shown in the cut, this operation is not yet completed. Thehydrogen alone may in this case be measured. The mixed gas voltameter has only one eudiometer. The exact equivalents are only approximately known. The volume of mixedgases per coulomb is given as . 1738 cubic centimeters (Ayrton); . 172cubic centimeters (Hospitalier); and other values by other authorities. The hydrogen is equal to 1/3 of the mixed gases almost exactly. Synonyms--Volume Voltameter--Sulphuric Acid Voltameter. The gas is measured at 0º (32º F. ) and 76 centimeters, or 30 inchesbarometer. Fig. 341. GAS VOLTAMETER. 565 STANDARD ELECTRICAL DICTIONARY. If the gas is measured in cubic inches, the temperature in degrees F. , and the barometric height in inches, the following formula may be usedfor reduction to standard pressure and temperature. It is the volumecorresponding to one coulomb. ( . 01058 * 30 * (491 + Fº - 32) ) / (h* 491) For the metric measurements and degrees C. (. 1738 * 76 * (273 + Cº)) / (h X 273) Voltameter, Silver. An apparatus consisting of a platinum vessel containing a solution ofsilver nitrate into which solution a silver anode dips, whose end iswrapped in muslin to prevent the detachment of any particles. When acurrent is passed by connecting one terminal to the dish and the otherto the rod, securing a proper direction of current, silver will bedeposited on the dish and the same amount will be dissolved from therod. The dish is weighed before and after the test. Its increase inweight gives the silver deposited. FIG. 342. SILVER VOLTAMETER. In the cut Ag is the silver anode, Pt is the platinum dish, r is theconducting rod, p is a wooden standard, Cu is a copper plate on whichthe dish rests and which also serves as a conductor and contact surface, b is a muslin cloth to place over the silver plate to prevent detachedparticles falling in the dish; s s' are the binding screws. The weight of silver corresponding to a coulomb is given variously bydifferent authorities. Ayrton and Daniell take 1. 11815 milligrams or. 017253 grain of metallic silver. Other determinations are as follows: 1. 1183 milligrams (Kohlrausch). 1. 124 " (Merscart). The solution of silver nitrate should be from 15 to 30 per cent. Ofstrength. The current should not exceed one ampere per six squareinches; or in other words not more than about 3/1000 grain of silvershould be deposited per second on a square inch area of the dish. Theedge of the silver disc or anode should be about equidistant from theside and bottom of the dish. The latter notes are due to Lord Rayleigh. 566 STANDARD ELECTRICAL DICTIONARY. Voltameter, Weight. A voltameter in which the amount of decomposition is determined byweighing the products, or one of the products of the electrolysis. Thetitles Voltameter, Copper, and Voltameter, Silver, may be cited. Fig. 343. WEIGHT VOLTAMETERS. In the cuts are shown examples of weight gas voltameters. These aretubes light enough to be weighed when charged. Each contains adecomposition cell T, with its platinum electrodes, and charged withdilute sulphuric acid, while t is calcium chloride or other drying agentto collect any water carried off as vapor or as spray by the escapinggases; c are corks placed in position when the weighing is beingexecuted, so as to prevent the calcium chloride from absorbing moisturefrom the air. In use the tubes are weighed. They are then connected to the circuit, after removal of the corks, and the decomposition proceeds. After asufficient time they are removed, the corks put in place, and they areweighed again. The loss gives the water decomposed. The water corresponding to one coulomb is . 09326 milligram . 001430 grain, Ayrton, . 092 " Hospitalier, . 0935 " Daniell. 567 STANDARD ELECTRICAL DICTIONARY. Voltametric Law. The law on which voltameters are based. The amount of chemicaldecomposition produced by an electric current in a given electrolyte isproportional to the quantity of electricity passed through the solution. Fig. 344. VOLTA'S FUNDAMENTAL EXPERIMENT. Volta's Fundamental Experiment. The moistened finger is placed on the upper plate of a condensing orelectrophorous electroscope. The other hand holds a plate of zinc z, soldered to a plate of copper c. The lower plate is touched with thecopper. On removing the cover the gold leaves l diverge and withnegative electricity. Hence zinc is supposed to be positivelyelectrified when in contact with copper. The experiment is used todemonstrate the contact theory of electricity. 568 STANDARD ELECTRICAL DICTIONARY. Volta's Law of Galvanic Action. The electro-motive force between any two metals in an electro-chemicalseries (see Electro-Chemical Series) is equal to the sum of theelectro-motive forces between all the intervening metals. Volta's Law of Thermo-electricity. In a compound circuit, consisting of a number of different metals, allpoints of which are at the same temperature, there is no current. Volt, B. A. The volt based on the B. A. Ohm. It is equal to . 9889 legal volt. Volt, Congress. The volt based upon the congress or legal ohm; the legal volt. Volt-coulomb. The unit of electric work; the watt-second; it is equivalent to 1. 0E7 ergs. . 24068 gram degree C. (calorie) . 737337 foot lbs. , . 00134 horse power seconds. Volt Indicator. A form of easily read voltameter for use in electric light stations andfor similar work. Volt, Legal. The legal volt based upon the legal ohm. It is equal to 1. 00112 B. A. Volt. Voltmeter. An instrument for determining the potential difference of any twopoints. In many cases it is a calibrated galvanometer wound with a coil of highresistance. The object to be attained is that it shall receive only aninsignificant portion of current and that such portion shall suffice toactuate it. If connected in parallel with any portion of a circuit, itshould not noticeably diminish its resistance. The divisions into which ammeters range themselves answer forvoltmeters. In practice the same construction is adopted for both. Thedifferent definitions of ammeters in disclosing the general lines ofthese instruments are in general applicable to voltmeters, except thatthe wire winding of the coils must be of thin wire of great length. Thedefinitions of ammeters may be consulted with the above understandingfor voltmeters. In the use made of voltmeters there is a distinction from ammeters. Anammeter is a current measurer and all the current measured must bepassed through it. But while a voltmeter is in fact a current measurer, it is so graduated and so used that it gives in its readings thedifference of potential existing between two places on a circuit, andwhile measuring the current passing through its own coils, it is bycalibration made to give not the current intensity, but theelectro-motive force producing such current. In use it may be connected to two terminals of an open circuit, when asit only permits an inconsiderable current to pass, it indicates thepotential difference existing between such points on open circuit. Or itmay be connected to any two parts of a closed circuit. Owing to its highresistance, although it is in parallel with the intervening portion ofthe circuit, as it is often connected in practice, it is without anyappreciable effect upon the current. It will then indicate the potentialdifference existing between the two points. 569 STANDARD ELECTRICAL DICTIONARY. Voltmeter, Battery. A voltmeter for use in running batteries. In one form (Wirt's) it isconstructed for a low range of voltage, reading up to two and a halfvolts and having exactly one ohm resistance, thus giving the batterysome work to do. Voltmeter, Cardew. A voltmeter in which the current passing through its conductor heatssuch conductor, causing it to expand. Its expansion is caused to move anindex needle. By calibration the movements of the needle are made tocorrespond to the potential differences producing the actuating currentsthrough it. The magnetic action of the current plays no part in itsoperation. It is the invention of Capt. Cardew, R. E. The construction of the instrument in one of its most recent forms isshown in the cut. On each side of the drum-like case of the instrumentare the binding screws. These connect with the blocks m and n. To thesethe fine wire conductor is connected and is carried down and up over thetwo pulleys seen at the lowest extremity, its centre being attached toc. From c a wire is carried to the drum p, shown on an enlarged scale onthe left of the cut. A second wire from the same drum or pulley connectsto the spring S. The winding of the two wires is shown in the separatefigure of c, where it is seen that they are screwed fast to theperiphery of the little drum, and are virtually continuations of eachother. By the screw A the tension of the spring S is adjusted. On the shaft of the little drum p is a pinion, which works into theteeth of the cog-wheel r. The shaft of r is extended through the dialof the instrument, and carries an index. The dial is marked off forvolts; g g and h h are standards for carrying the pulleys. 570 STANDARD ELECTRICAL DICTIONARY. The action of the instrument is as follows. The current passing throughthe wire heats it. This current by Ohm's law is proportional to theelectro-motive force between the terminals. As it is heated it expandsand as it cools contracts, definite expanding and contractingcorresponding to definite potential differences. As the wire expands andcontracts the block or pin c moves back and forth, thus turning the drump and cogwheel r one way or permitting it to turn the other way underthe pull of the spring S. Fig. 345. CARDEW VOLTMETER. In this construction for a given expansion of the wire the piece c onlymoves one half as much. The advantage of using a wire twice as long aswould be required for the same degree of movement were the fullexpansion utilized is that a very thin wire can be employed. Such a wireheats and cools more readily, and hence the instrument reaches itsreading more quickly or is more deadbeat, if we borrow a phraseologyproperly applicable only to instruments with oscillating indexes. In the most recent instruments about thirteen feet of wire . 0025 inch indiameter, and made of platinum-silver alloy is used. 571 STANDARD ELECTRICAL DICTIONARY. If the potential difference to be measured lies between 30 and 120 voltsthe wire as described suffices. But to extend the range of theinstrument a resistance in series is required. If such resistance isdouble that of the instrument wire, and remains double whether thelatter is hot or cold the readings on the scale will correspond toexactly twice the number of volts. This is brought about in someinstruments by the introduction in series of a duplicate wire, preciselysimilar to the other wire, and like it, carried around pulleys and keptstretched by a spring. [Transcriber's note: If the series resistance is twice that of thevoltmeter, the indicated voltage will be ONE THIRD of the totalvoltage. ] Thus whatever ratio of resistance exists between the two wires cold, itis always the same at any temperature, as they both increase intemperature at exactly the same rate. Tubes are provided to enclose thestretched wires and pulleys, which tubes are blackened. The voltmeter is unaffected by magnetic fields, and, as itsself-induction is very slight, it is much used for alternating currents. The tubes containing the wire may be three feet long. Its disadvantages are thus summarized by Ayrton. It absorbs a good dealof energy; it cannot be constructed for small potential differences, asthe wire cannot be made thicker, as it would make it more sluggish;there is vagueness in the readings near the zero point and sometimesinaccuracy in the upper part of the scale. Volts, Lost. The volts at the terminals of a dynamo at full load fall short of theirvalue on open circuit. The difference of the two values are termed lostvolts. Voltmeter, Electrostatic. A voltmeter based on the lines of the quadrant electrometer. It includestwo sets of quadrants, each oppositely excited by one of the two parts, whose potential difference is to be determined. They attract each otheragainst a controlling force as of gravity. One form has the two sets poised on horizontal axes, bringing the partsso that the flat quadrants move in vertical planes. In another form a number of quadrants are used in each set, the membersof the two sets alternating with each other. One set is fixed, theothers move and carry the index. Vulcanite. Vulcanized india rubber which by high proportion of sulphur and propervulcanization has been made hard. It is sometimes distinguished fromebonite as being comparatively light in color, often a dull red, whileebonite is black. For its electrical properties see Ebonite. Both substances have their defects, in producing surface leakage. Washing with weak ammonia, or with dilute soda solution, followed bydistilled water, is recommended for the surface, if there is any troublewith surface leakage. It may also be rubbed over with melted paraffinewax. 572 STANDARD ELECTRICAL DICTIONARY. W. (a) A symbol or abbreviation for watt. (b) A symbol or abbreviation for work. (c) A symbol or abbreviation for weight. Wall Bracket. A telegraph bracket to be attached to the external walls of buildings towhich wires are attached as they come from the poles to reachconverters, or for direct introduction into a building. Wall Sockets. Sockets for incandescent lamps constructed to be attached to a wall. Ward. Direction in a straight line; a term proposed by Prof. James Thompson. The words "backward" and "forward" indicate its scope. Water. A compound whose molecule consists of two atoms of hydrogen and one atomof oxygen; formula, H2 O. Its specific gravity is 1, it being the base of the system of specificgravities of solids and liquids. If pure, it is almost a non-conductor of electricity. If any impurity ispresent it still presents an exceedingly high, almost immeasurable trueresistance, but becomes by the presence of any impurity an electrolyte. Water Equivalent. In a calorimeter of any kind the weight of water which would be raisedas much as is the calorimeter with its contents by the addition of anygiven amount of heat received by the calorimeter. Waterproof Lamp Globe. An outer globe for incandescent lamps, to protect them from water. Watt. (a) The practical unit of electric activity, rate of work, or rate ofenergy. It is the rate of energy or of work represented by a current ofone ampere urged by one volt electro-motive force; the volt-ampere. It is the analogue in electricity of the horse power in mechanics;approximately, 746 watts represent one electric horse power. Ohm's law, taken as C = E/R, gives as values for current, C and E/R, andfor electro- motive force C R. In these formulas, C represents currentstrength, R represents resistance and E represents electro-motive force. Then a watt being the product of electro-motive force by currentstrength, we get the following values for rate of electric energy, ofwhich the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R. The equivalents of the watt vary a little according to differentauthorities. Ayrton gives the following equivalents: 44. 25 foot poundsper minute--. 7375 foot pounds per second--1/746 horse power. Thesevalues are practically accurate. Hospitalier gives . 7377 foot pounds persecond. Hering gives . 737324 foot pounds per second, and 1000/745941horse power. 573 STANDARD ELECTRICAL DICTIONARY. It is equal to 1E7 ergs per second. Synonym--Volt-ampere. (c) It has been proposed to use the term as the unit of energy, insteadof activity or rate of energy (Sir C. W. Siemens, British Association, 1882); this use has not been adopted and may be regarded as abandoned. [Transcriber's note; Watt is a unit of POWER--energy per unit of time. ] Watt-hour. A unit of electric energy or work; one watt exerted or expended for onehour. It is equivalent to : 866. 448 gram-degrees C. (calories) 2654. 4 foot lbs. 3600 watt-seconds or volt-coulombs. 60 watt-minutes. Watt-minute. A unit of electric energy or work; one watt exerted or expended for oneminute. It is equivalent to 14. 4408 gram-degrees C. (calories), 44. 240 foot pounds, 60 watt seconds or volt-coulombs, 1/60 watt hour. Watts, Apparent. The product in an alternating current dynamo of the virtual amperes bythe virtual volts. To give the true watts this product must bemultiplied by the cosine of the angle of lead or lag. (See Current, Wattless. ) [Transcriber's note: This is now called a volt-amp. The usual usage isKVA, or kilovolt-ampere. ] Watt-second. A unit of electric energy or work. One watt exerted or expended for onesecond. It is equivalent to . 24068 gram degree C. (calorie), . 000955 lb. Degree F. , . 737337 foot lbs. , . 0013406 horse power second (English), . 0013592 horse power second (metric). Synonym--Volt-coulomb. Waves, Electro-magnetic. Ether waves caused by electromagnetic disturbances affecting theluminiferous ether. (See Discharge, Oscillatory--Maxwell's Theory ofLight--Resonance. Electric. ) [Transcriber's note: The Michaelson-Morley experiment (1887) had alreadycalled ether into question, but quantum theory and photons are decadesin the future. ] 574 STANDARD ELECTRICAL DICTIONARY. Weber. (a. ) A name suggested by Clausius and Siemens to denote a magnet pole ofunit strength. This use is abandoned. (b. ) It has been used to designate the unit of quantity--the coulomb. This use is abandoned. (c. ) It has been used to designate the unit of current strength theampere. This use is abandoned. [Transcriber's note: Definition (a) is now used. One weber of magneticflux linked to a circuit of one turn produces an electromotive force of1 volt if it is reduced to zero at a uniform rate in 1 second. ] Weber-meter. An ampere-meter or ammeter. The term is not used since the term "weber, "indicating the ampere or coulomb, has been abandoned. Welding, Electric. Welding metals by heat produced by electricity. The heat may be producedby a current passing through the point of junction (Elihu Thomson) or bythe voltaic arc. (Benardos & Olzewski. ) Fig. 346. ELECTRIC WELDING INDUCTION COIL. The current process is carried out by pressing together the objects tobe united, while holding them in conducting clamps. A heavy current isturned on by way of the clamps and rapidly heats the metals at thejunction, which is of course the point of highest resistance. As themetal softens, it is pressed together, one of the clamps being mountedwith feed motion, flux is dropped on if necessary, and the metal piecesunite. The most remarkable results are thus attained; almost all common metalscan be welded, and different metals can be welded together. Tubes andother shapes can also be united. In many cases the weld is the strongestpart. 575 STANDARD ELECTRICAL DICTIONARY. The alternating current is employed. A special dynamo is sometimes usedto produce it. This dynamo has two windings on the armature. One is offine wire and is in series with the field magnets and excites them. Theother is of copper bars, and connects with the welding apparatus, givinga current of high intensity but actuated by low potential. Where the special dynamo is not used, an induction coil or transformeris used. The primary includes a large number of convolutions ofrelatively fine wire; the secondary may only be one turn of a largecopper bar. The cut shows in diagram an electric welding coil. P is the primary coilof a number of turns of wire; S S is the secondary, a single copper barbent into an almost complete circle. It terminates in clamps D D forholding the bars to be welded. B C, B' C are the bars to be welded. Theyare pressed together by the screw J. The large coil I of iron wiresurrounding the coils represents the iron core. The real apparatus as at present constructed involves manymodifications. The diagram only illustrates the principle of theapparatus. In welding by the voltaic arc the place to be heated is made anelectrode of an arc by connection with one terminal of an electriccircuit. A carbon is connected to the other terminal. An arc is startedby touching and withdrawal of the carbon. The heat may be used forwelding, soldering, brazing, or even for perforating or dividing metalsheets. Welding Transformer. The induction coil or transformer used in electric welding. For itsgeneral principles of construction, see Welding, Electric. Wheatstone's Bridge. A system of connections applied to parallel circuits, includingresistance coils for the purpose of measuring an unknown resistance. Asingle current is made to pass from A through two parallel connectedbranches, joining together again at C. A cross connection B D has agalvanometer or other current indicator in circuit. In any conductorthrough which a current is passing, the fall of potential at givenpoints is proportional to the resistance between such points. Referringto the diagram a given fall of potential exists between A and C. Thefall between A and B is to the fall between A and C as the resistance rbetween A and B is to the resistance r + r' between A and C. The sameapplies to the other branch, with the substitution of the resistances sand S' and the point D for r r' and B. Therefore, if this proportionholds, r : r' : : s : S'. No current will go through B D, and thegalvanometer will be unaffected. Assume s' to be of unknown resistance, the above proportion will give it, if r, r' and s are known, or if theratio of r to r' and the absolute value of s is known. 576 STANDARD ELECTRICAL DICTIONARY. In use the resistances r, r', and s are made to vary as desired. Tomeasure an unknown resistance it is introduced at S', and one of theother resistances is varied until the galvanometer is unaffected. Thenthe resistance of S' is determined by calculation as just explained. Theartificial resistances may be resistance coils, q. V. , or it is enoughto have one unknown resistance at s. Then if the length of wire ABC isaccurately known, the point B can be shifted along it until the balanceis attained. The relative lengths A B, and B C, will then give the ratior : r' needed for the calculation. This assumes the wire ABC to be ofabsolutely uniform resistance. This is the principle of the meter-bridgedescribed below. The use of coils is the more common method and iscarried out by special resistance boxes, with the connections arrangedto carry out the exact principle as explained. The principle ofconstruction and use of a resistance box of the Wheatstone bridge type, as shown in the cut, is described under Box Bridge, q. V. FIG. 347. WHEATSTONE BRIDGE CONNECTIONS. FIG. 348. TOP OF BOX BRIDGE. 577 STANDARD ELECTRICAL DICTIONARY. The next cut shows the sliding form of bridge called the meter bridge, if the slide wire is a meter long or a half- or a quarter-meter bridge, etc. , according to the length of this wire. It is described under MeterBridge, q. V. Many refinements in construction and in proper proportionof resistances for given work apply to these constructions. Synonyms--Electric Balance--Resistance Bridge--Wheatstone's Balance. Fig. 349. METER BRIDGE. Whirl, Electric. (a) A conductor carrying an electric current is surrounded by circularlines of force, which are sometimes termed an electric whirl. (b) The Electric Flyer. (See Flyer, Electric. ) Wimshurst Electric Machine. An influence machine for producing high potential or static electricity. Two circular discs of thin glass are mounted on perforated hubs orbosses of wood or ebonite. Each hub has a groove turned upon it toreceive a cord. Each disc is shellacked. They are mounted on ahorizontal steel spindle so as to face and to be within one-eighth of aninch of each other. On the outside of each disc sixteen or eighteensectors of tinfoil or thin metal are cemented. 578 STANDARD ELECTRICAL DICTIONARY. Two curved brass rods terminating in wire brushes curved into asemi-ellipse just graze the outer surfaces of the plates with theirbrushes. They lie in imaginary planes, passing through the axis of thespindle and at right angles from each other. Four collecting combs are arranged horizontally on insulating supportsto collect electricity from the horizontal diameters of the discs. Theselie at an angle of about 45° with the other equalizing rods. Dischargingrods connect with the collecting combs. The principle of the machine is that one set of sector plates act asinductors for the other set. Its action is not perfectly understood. It works well in damp weather, far surpassing other influence machinesin this respect. On turning the handle a constant succession or streamof sparks is produced between the terminals of the discharging rods. Windage. In a dynamo the real air gap between the armature windings and polepieces is sometimes thus termed. Wind, Electric. The rush of air particles from a point connected to a statically chargedcondenser. Winding, Compound. A method of winding a generator or motor in which a shunt winding isused for the field magnets and in which also a second winding of themagnet is placed in series with the outer circuit. (See Winding, Series--Winding, Shunt. ) Fig. 350. CHARACTERISTIC CURVES OF SHUNT AND SERIES WINDING. The object of compound winding is to make a self-regulating dynamo andthis object is partly attained for a constant speed. The characteristic curves of shunt and series winding are of oppositenatures. The first increases in electro-motive force for resistance inthe outer circuit, the latter decreases under the same conditions. Ifthe windings are so proportioned that these conditions for each one ofthe two windings are equal and opposite, it is evident that thecharacteristic may be a straight line. This, however, it will only be ata single speed of rotation. 579 STANDARD ELECTRICAL DICTIONARY. Winding, Disc. A winding which (S. P. Thompson) may be treated as a drum windingextended radially, the periphery corresponding to the back end of thedrum. The magnet poles are generally placed so as to face the side orsides of the disc. Winding, Lap. A method of winding disc and drum armatures. It consists in lapping backeach lead of wire towards the preceding lead upon the commutator end ofthe armature. Thus taking the letter U as the diagrammaticalrepresentation of a turn of wire in connecting its ends to thecommutator bars they are brought towards each other so as to connectwith contiguous commutator bars. This carries out the principle ofkeeping the two members of the U moving in regions of opposite polarityof field, so that the currents induced in them shall have oppositedirections, thus producing a total current in one sense through the bentwire. Winding, Long Shunt. A system of compound winding for dynamos and motors. The field is woundin series and, in addition thereto, there is a shunt winding connectedacross from terminal to terminal of the machine, and which may beregarded either as a shunt to the outer circuit, or as a shunt to theseries-field and armature winding. (See Winding, Short Shunt. ) Synonyms--Series and Long Shunt Winding. Winding, Multiple. A winding of an electro-magnet, in which separate coils are wound on thecore, so that one or any number may be used as desired in parallel or inseries. For each coil a separate binding post should be provided. Winding, Multipolar. Winding adapted for armatures of multi-polar dynamos or motors. Winding, Series. A method of winding a generator or motor, in which one of thecommutator-brush connections is connected to the field-magnet winding;the other end of the magnet winding connects with the outer circuit. Theother armature-brush connects with the other terminal of the outercircuit. Winding, Series and Separate Coil. A method of automatic regulation applied to alternating current dynamos. Winding, Short Shunt. A method of compound winding for dynamos and motors. The field is woundin series, and in addition thereto there is a shunt winding connectedfrom brush to brush only, thus paralleling the armature. (See Winding, Long Shunt. ) Synonyms--Series and Short Shunt Winding. 580 STANDARD ELECTRICAL DICTIONARY. Winding, Shunt. A method of winding a generator or motor. Each commutator-brush has twoconnections. One set are the terminals of the outer circuit, the otherset are the terminals of the field-magnet windings. In other words, thefield-magnet windings are in shunt or in parallel with the outercircuit. Winding, Shuttle. A method of dynamo or motor-armature winding. A single groove passeslongitudinally around the core and in this the wire is continuouslywound. The system is not now used. The old Siemens' H armatureillustrates the principle. Winding, Wave. A method of winding disc and drum armatures. It consists in advancingthe commutator ends of the U shaped turns progressively, so that as manycommutator bars intervene between any two consecutive commutatorconnections of the wire as there are leads of wire on the drum betweenconsecutive leads of the wire. This is carried out with due regard tothe principle that taking the letter U as the diagrammaticalrepresentation of a turn of wire, its two members must move throughregions of the field of opposite polarity. Wire Finder. A galvanometer or other instrument used for identifying the ends of agiven wire in a cable containing several. Work. When a force acts upon a body and the body moves in the direction of theforce, the force does work. Hence, work is the action of a force throughspace against resistance. It is generally expressed in compound units of length and weight, asfoot-pounds, meaning a pound raised one foot. Work, Electric, Unit of. The volt-coulomb, q. V. , or watt-second, as it is often termed. Working, Diode. In multiplex telegraphy the transmission of two messages, simultaneously, over one wire. (See Telegraphy, Multiple. ) Working, Contraplex. A variety of duplex telegraphy in which the messages are sent fromopposite ends of the line, simultaneously, so as to be transmitted inopposite directions. (See Working, Diplex. ) Working, Diplex. In duplex telegraphy the sending of two independent messages from thesame end of the line in the same direction. 581 STANDARD ELECTRICAL DICTIONARY. Working, Double Curb. A method of working telegraph lines. When a signal is sent the line ischarged. This has to be got rid of, and is an element of retardation. Indouble curb working it is disposed of by sending a momentary currentfirst in the reverse, and then in the same, and finally in the reversedirection. This is found to reduce the charge to a very low point. Working, Hexode. In multiplex telegraphy the transmission of six messages simultaneouslyover one wire. (See Telegraphy, Multiplex. ) Working, Pentode. In multiplex telegraphy the transmission of five messages simultaneouslyover one wire. (See Telegraphy, Multiplex. ) Working, Reverse Current. A method of telegraphy, in which the currents are reversed or alternatedin direction. Working, Single Curb. A simpler form of telegraph signaling than double curb working. Itconsists in sending a reverse current through the line for each signalby reversing the battery connection. Working, Tetrode. In multiplex telegraphy the transmission of four messages simultaneouslyover the same line. (See Telegraphy, Multiplex. ) Working, Triode. In multiplex telegraphy the transmission of three messagessimultaneously over the same wire. (See Telegraphy, Multiplex. ) Work, Unit of. The erg, q. V. It is the same as the unit of energy, of which work isthe corelative, being equal and opposite to the energy expended in doingit. There are many other engineering units of work, as the foot-poundand foot-ton. Yoke. In an electro-magnet, the piece of iron which connects the ends furthestfrom the poles of the two portions of the core on which the wire iswound. Zamboni's Dry Pile. A voltaic pile or battery. It is made of discs of paper, silvered ortinned on one side and sprinkled on the other with binoxide ofmanganese. Sometimes as many as 2, 000 of such couples are piled up in aglass tube and pressed together with two rods which form the terminals. They maintain a high potential difference, but having very highresistance and slight polarization capacity, give exceedingly smallquantities. Zero. (a) The origin of any scale of measurement. (b) An infinitely small quantity or measurement. 582 STANDARD ELECTRICAL DICTIONARY. Zero, Absolute. From several considerations it is believed that at a certain temperaturethe molecules of all bodies would touch each other, their kinetic motionwould cease, and there would be no heat. This temperature is theabsolute zero. It is put at -273° C. (-459° F. ) [Transcriber's note; The modern value is 0° Kelvin, -273. 15° C, or-459. 67° F. The lowest reported temperature observed is 1E-10° K. ] Zero, Potential. Conventionally, the potential of the earth. True zero potential couldonly exist in the surface of a body infinitely distant from otherelectrified bodies. Zero, Thermometric. There are three thermometric zeros. In the Réaumur and centigradescales, it is at the temperature of melting ice; in the Fahrenheitscale, it is 32° F. Below that temperature, or corresponds to -17. 78° C. The third is the absolute zero. (See Zero, Absolute. ) Zinc. A metal; one of the elements; atomic weight, 65. 1;specific gravity, 6. 8 to 7. 2. microhms. Resistance at 0° C. (32° F. ), per centimeter cube, 5. 626Resistance at 0° C. (32° F. ), per inch cube, 2. 215 Relative resistance (silver = 1), 3. 741 ohms. Resistance of a wire, 1 foot long, weighing 1 grain, . 5766 (a) 1 foot long, 1 millimeter diameter, 33. 85 (b) 1 meter long, weighing 1 gram, . 4023 (c) 1 meter long, 1 millimeter diameter, . 07163 Zinc is principally used in electrical work as the positive plate involtaic batteries. Zincode. The terminal connecting with the zinc plate, or its equivalent in anelectric circuit; the negative electrode; the kathode. A term now littleused. Zinc Sender. An apparatus used in telegraphy for sending a momentary reverse currentinto the line after each signal, thus counteracting retardation. Zone, Peripolar. In medical electricity, the region surrounding the polar zone, q. V. Zone, Polar. In medical electricity, the region surrounding the electrode applied tothe human body. 583-624 INDEX. PageA 7Absolute 7Absolute Calibration 97Absolute Electric Potential 429Absolute Electrometer 222Absolute Galvanometer 266Absolute Measurement 8Absolute Potential 428Absolute Temperature 8Absolute Unit 554Absolute Unit Resistance, Weber's 468Absolute Vacuum 557Absolute Zero 581Abscissa 7Abscissas, Axis of 54Absorption, Electric 8A. C. C. 8Acceleration 8Accumulator 8Accumulator, Electrostatic 8Accumulator, Water Dropping 9Acetic Acid Battery 58Acheson Effect 208Acid, Carbonic 108Acid, Chromic, Battery 61Acid, Hydrochloric, Battery 66Acid, Spent 491Acid, Sulphuric 497Acidometer 10Acierage 494Aclinic Line 10Acoustic Telegraphy 10Acoutemeter 10, 53Action, Electrophoric 230Action, Local 331Action, Magne-crystallic 335Action, Refreshing 454Action, Secondary 477Actinic Photometer 411Actinic Rays. 11Actinism 11Actinometer, Electric 11Active Electric Circuit, 123Activity 11Actual Horse Power 290Adapter 11A. D. C. , 11Adherence, Electro-magnetic 11Adherence, Magnetic 338Adjuster, Cord 152Adjustment of Brushes 90Admiralty Rules of Heating 12AEolotropic 34Aerial Cable 95Aerial Conductor 12Affinity 12Affinity, Molecular 380After Current, . 159Agglomerate Leclanché Battery 66Agir Motor 13Agone 13Agonic Line, 13Air 13Air Blast 13Air Condenser 14Air Field 252Air Gaps 15Air Line Wire 15Air Pump, Heated 15Air Pump, Mercurial 16Air Pumps, Short Fall 16Alarm, Burglar 16Alarm, Electric 17Alarm, Fire, Electric Automatic 257Alarm, Fire and Heat 17Alarm, Overflow 18Alarm, Water Level 18Alcohol, Electric Rectification of 18Alignment, 18Allotropy 18Alloy 18Alloy, Platinum 419Alloy, Platinum-Silver 419Alloys, Paillard 400Alphabet, Telegraphic 19Alternating 23Alternating Current 159Alternating Current Arc 23Alternating Current Dynamo 193Alternating Current Generator or Dynamo 24Alternating Current Meter 373Alternating Current System 23Alternating Field 252Alternative Current 563Alternative Path 24Alternatives, Voltaic 563Alternator 24Alternator, Constant Current 24Alternator, Dead Point of an 177Alternation 23Alternation, Complete 23Alternation, Cycle of 175Alum Battery 58Aluminum 24Aluminum Battery 58Amalgam 24Amalgamation 25Amber 25American Twist Joint 309Ammeter 26Ammeter, Ayrton 26Ammeter, Commutator 26Ammeter, Cunynghame's 26Ammeter, Eccentric Iron Disc 27Ammeter, Electro-magnetic 27Ammeter, Gravity 27Ammeter, Magnetic Vane 27Ammeter, Magnifying Spring 28Ammeter, Permanent Magnet 28Ammeter, Reducteur for 453Ammeter, Solenoid 28Ammeter, Spring 28Ammeter, Steel Yard 28Ammunition Hoist, Electric 29Amperage 29Ampere 29Ampere- and Volt-meter Galvanometer 274Ampere Arc 30Ampere Balance 56Ampere Currents 30Ampere Feet 30Ampere-hour 30Amperes, Lost 30Ampêre's Memoria Technica 30Ampere Meters 26, 30Ampere Meter, Balance 391Ampere Meter, Neutral Wire 391Ampere-minute 30Ampere Ring 30Ampere-second 30Ampere's Theory of Magnetism 354Ampere-turns 31Ampere-turns, Primary 31Ampere-turns, Secondary 31, 551Ampere Windings 31Ampérian Currents 165Amplitude of Waves 31Analogous Pole 31, 425Analysis 31Analysis, Electric 32Analysis, Electrolytic 214Analyzer, Electric 32Anelectrics 32Anelectrotonus 32Angle of Declination 32, 177Angle of the Polar Span 32Angle of Inclination or Dip 33Angle of Lag 33-318Angle of Lead 33Angle of Maximum Sensitiveness 479Angle of Polar Span 423Angle, Polar 423Angle, Unit 554Angular Currents 165Angular Currents, Laws of 165Angular Force 544Angular Velocity 32, 559Animal Electricity 33Animal System, Electric Excitability of 247Anion 33Anisotropic 34Annealing, Electric 34Annular Electro-magnet 216Annunciator 34Annunciator Clock 35Annunciator Clock, Electric 127Annunciator Drop 35Annunciator, Gravity Drop 35Annunciator, Needle 35Annunciator, Swinging or Pendulum 35Anodal Diffusion 35Anode 36Anodic Closure Contraction 36Anodic Duration Contraction 36Anodic Opening Contraction 36Anodic Reactions 36Anomalous Magnet 335Anti-induction Conductor 36, 145Anti-magnetic Shield 37Antilogous Pole, 425Antimony 37Anvil 37A. O. C. 38Aperiodic 38Aperiodic Galvanometer 266Apparent Coefficient of Magnetic Induction 346Apparent Resistance 297, 462Apparent Watts 573Arago's Disc 88Arc 39Arc, Ampere 30Arc, Compound. 39Arc, Electric Blow-pipe 84Arc, Metallic 39Arc, Micrometer 39, 376Arc, Multiple 387Arc, Simple 39Arc, Voltaic 39Arc Box, Multiple 387Arc Lamp 319Arc Lamp, Differential 320Arc Lamp, Double Carbon 191Areometer 41Areometer, Bead 41Argyrometry 41Arm 41Armature 41Armature, Bar 42Armature, Bipolar 42Armature Bore 42Armature Chamber 42Armature, Closed Coil 43Armature Coil, or Coils 43Armature Conductors, Lamination of 319Armature Core 43Armature, Cylinder 43Armature, Cylindrical 45Armature, Disc 43Armature, Drum 45Armature Factor 45Armature, Flat Ring 45Armature, Girder 49Armature, H 49Armature, Hinged 45Armature, Hole 45Armature, Intensity 45Armature Interference 45Armature, Load of 46Armature, Multipolar 46Armature, Neutral 46Armature, Neutral Relay 46, 390Armature, Non-polarized 46Armature of Influence Machine 46Armature of Leyden Jar or Static Condenser 46Armature, Open Coil 46Armature, Perforated 45Armature, Pivoted 47Armature Pockets 47Armature, Polarized 47Armature, Pole 47Armature, Quantity 47Armature, Radial 47Armature Reactions 41Armature, Revolving, Page's 47Armature, Ring 48Armature, Rolling 49Armatures, Gyrostatic Action of 288Armature, Shuttle 49Armature, Siemens' Old 49Armature, Spherical 49Armature, Stranded Conductor 49Armature, Unipolar 50, 553Armature, Ventilation of 560Armor of Cable 50Arm, Rheostat 472Arms, Proportionate 436Arms, Ratio 437Arms, Rocker 50-474Arrester, Lightning 328Arrester, Lightning, Counter-electro-motive Force 329Arrester, Lightning, Plates 329Arrester, Lightning, Vacuum. 329Arrester Plate 417Arrester, Spark 489Arrival Curve 168Articulate Speech 50Artificial Carbon 106Artificial Magnet 335Ascending Lightning 330Assymmetrical Resistance 462Astatic 50Astatic Circuit 12Astatic Couple 157Astatic Galvanometer 266Astatic Needle 50Astronomical Meridian, 372Asymptote 51Atmosphere 51Atmosphere, Residual 51, 460Atmospheric Electricity 51Atom 52Atomic Attraction 52Atomic Current 160Atomic Energy 238Atomic Heat 52-285Atomic Weight 53Atomicity 52Attracted Disc Electrometer 223Attraction 53Attraction, Atomic 52Attraction, Magnetic 338Attraction, Molar 380Attraction, Molecular 380Attraction and Repulsion, Electro-dynamic 211Attraction and Repulsion, Electro-magnetic 217Attraction and Repulsion, Electro-static 234Attraction and Repulsion, Electro-static, Coulomb's Law of 155Audiometer 53Aura, Electrical 53Aurora 53Austral Pole 54Autographic Telegraph 510Automatic Circuit Breaker 121Automatic Cut Out 175, 475Automatic Drop 192Automatic Electric Bell 78Automatic Electric Fire Alarm 257Automatic Switch 500Automatic Telegraph 504A. W. G. , 54Axial Couple 514Axial Force 544Axial Magnet 336Axis, Electric 54Axis, Magnetic 338Axis of Abscissas 54Axis of Ordinates 54, 397Axis of X 54Axis of Y 54, 397Ayrton's Ammeter 26Azimuth 54Azimuth Circle 54Azimuth Compass 141Azimuth, Magnetic 338 B 55B. A. 55Back Electro-motive Force of Polarization 156Back Induction 55Back Shock or Stroke of Lightning 55Back Stroke 55Bagration Battery 59Balance 55Balance, Ampere 56Balance Ampere Meter 391Balance, Electric 577Balance, Inductance 293Balance, Plating 417Balance, Slide 374Balance, Thermic 85Balance, Torsion, Coulomb's 544Balance, Wheatstone's 577Balata 56Ballistic Galvanometer 567Balloon Battery 59B. And S. W. G. 56Banked Battery 59Bank of Lamps 323B. A. Ohm 394Barad 56Bar, Armature 42Bar, Bus 94Bar Electro-magnet 217Bar Magnet 336Barometer 56Bar, Omnibus 94Bar Photometer 411Bars, Commutator 56, 140Bath 57Bath, Bipolar Electric 57Bath, Copper 152Bath, Copper Stripping 152Bath, Electric Head 284Bath, Electric Shower 57Bath, Gold 279Bath, Gold Stripping 279Bath, Multipolar Electric 57Bath, Nickel 391Bath, Plating 418Baths, Electro-medical 222Bath, Silver 484Bath, Silver Stripping 484Bath, Stripping 57Bath, Unipolar Electric 57Batten 57-58Battery, Acetic Acid 58Battery, Alum 58Battery, Aluminum 58Battery, Bagration 59Battery, Balloon 59Battery, Banked 59Battery, Bichromate 59Battery, Bunsen 59Battery, Cadmium 60Battery, Callan 60Battery, Camacho's 60Battery, Carré's 60Battery, Cautery 61Battery Cell, Element of a 237Battery, Chloric Acid 61Battery, Chloride of Lime 61Battery, Chromic Acid 61Battery, Closed Circuit 61Battery, Column 61Battery, d'Arsonval's 62Battery, de la Rue . 62Battery, de la Rive's Floating 179Battery, Dry 63Battery, Elements of 63Battery, Faradic 63Battery, Ferric Chloride 63Battery, Fuller's 63Battery, Gas 63Battery, Gas, Grove's 281Battery Gauge 64Battery, Gravity 64Battery, Grenet 65Battery, Grove's 65Battery, Hydrochloric Acid 66Battery, Lalande & Chaperon 69Battery, Lalande-Edison 69Battery, Lead Chloride 66Battery, Lead Sulphate 66Battery, Leclanché 66Battery, Leclanché Agglomerate 66Battery, Local 66, 831Battery, Magnetic 338Battery, Main 66Battery, Marié Davy's 67Battery, Maynooth's 67Battery, Medical 67Battery, Meidinger's 68Battery, Mercury Bichromate 63Battery Mud 68Battery, Multiple Connected 68Battery, Niaudet's 61Battery, Nitric Acid 68Battery of Dynamos 6SBattery of Leyden Jars, 68Battery, Open Circuit 68Battery or Pile, Thermo-electric 530Battery, Oxide of Copper 68Battery, Peroxide of Lead 69Battery, Platinized Carbon 69Battery, Plunge 69Battery, Pneumatic 69Battery, Primary 69, 434Battery, Pulvermacher's Electro-medical 69Battery, Sal Ammoniac 69Battery, Salt, or Sea Salt 69Battery, Sand 70Battery, Secondary 70Battery, Secondary, Planté's 72Battery, Secondary, Real Efficiency of 205Battery, Sir William Thomson's 72Battery, Siemens and Halske's 72Battery, Skrivanow 72Battery, Smee's 73Battery Solutions, Chromic Acid 73 119, 178, 192, 232, 318, 421, 542, 549Battery, Spiral 73Battery, Split 73Battery, Sulphate of Mercury 67Battery System, Universal 556Battery, Thermo-chemical 530Battery, Trough 73Battery, Trouvé's Blotting Paper 73Battery, Tyer's 74Battery, Upward's 75Battery, Varley's 76Battery, Volta's 76Battery, Voltaic or Galvanic 76Battery Voltmeter 569Battery, Water 77Battery, Wollaston 78B. A. Unit, 554B. A. Unit of Resistance 78, 462B. A. Volt 568B. E. 78Bead Areometer 41Becquerel's Laws of Thermo-electricity 78Beaumé Hydrometer 78Bed-piece 78Bell, Automatic Electric 78Bell, Call 78, 98Bell Call 79Bell Call, Extension 248Bell, Circular 79Bell, Differentially Wound 79Bell, Electric 79Bell, Electro-mechanical 80Bell, Indicating 80, 297Bell, Magneto 80Bell, Magneto Call 361Bell, Night 392Bell-shaped Magnet, 336Bells, Relay 80, 457Bell, Trembling 78Bell, Vibrating. 78Belts, Joints in 311Bennett's Electroscope 233Bias 80Bias of Tongue of Polarized Relay 542Bichromate Battery 59Bichromate Mercury Battery 63Bifilar Suspension 498Bifilar Winding 81Binary Compound 81Binding 81Binding Posts or Screws 81Binnacle 81Biology, Electro- 208Bioscopy, Electric 82Bipolar Armature 42Bipolar Electric Bath 57Bisected Coils 132Bismuth 82Bi-telephone 82, 524Black, Platinum 419Blasting, Electric 83Bleaching, Electric 83Block, Branch 87Block, Cross-over 158Block System 83Block Wire 83Blotting Paper Battery, Trouvé's 73Blow-pipe 83Blow-pipe, Electric Arc 84Blue Magnetism 355Bluestone 84Blue Vitriol 562Board, Cross-connecting 157Board, Fuse 263Board, Hanger 284Board, Key 313Board, Multiple Switch 387Board of Trade Ohm 394Board of Trade Unit 555Board, Switch 500Boat, Electric 84Bobbins 84Body Protector 84Bohenberger's Electroscope 233Boiler Feed, Electric 84Boiling 84Boll 85Bolometer 85Bombardment, Molecular 380Bore, Armature 42Boreal Pole 85Bot 85Bound Charge 115Box Bridge 85Box, Cable 95Box, Cooling 151Box, Distributing 190Boxes, Flush 258Box, Fishing 311Box, Fuse 263Boxing the Compass 86Box, Junction 311Box, Multiple Arc 387Box, Resistance 462Box, Resistance, Sliding 463Box Sounding Relay 457Box, Splice 492Bracket, Saddle 475Bracket, Wall 572Braid, Tubular 550Brake, Electro-magnetic 86Brake, Magneto-electric 362Brake, Prony 435Branch 87Branch Block 87Branch Circuit 121Branch Conductor 87Branding, Electric 87Brassing 87Brazing, Electric 87Break 88Break, Circuit Loop 125Break-down Switch 88Breaker, Automatic Circuit 121Breaker, Circuit 121Breaker, Circuit, File 121Breaker, Contact 121, 146Break Induced Current 162Breaking Weight 89Break, Loop 332Break Shock 482Breath Figures, Electric 89Breeze, Electric 89Breeze, Static 493Breguet Unit of Resistance 463Bridge 89Bridge, Box 89Bridge, Inductance 293Bridge, Induction 293Bridge Key 313Bridge, Magnetic 338Bridge, Meter 373Bridge, Resistance 577Bridge, Reversible 472Bridge, Slide 374Bridge, Wheatstone . 575Bridge, Wheatstone, Commercial 36British Association Bridge 89Britannia Joint 309Broadside Method 89Broken Circuit 125Bronzing 89Brush 90Brush, Carbon 90Brush, Collecting 90Brush, Discharge 187Brushes, Adjustment of 90Brushes, Lead of 90Brushes, Negative Lead of 324Brushes, Scratch 476Brush, Faradic 251Brush Holders 91Brush, Pilot 91Brush, Rotating 91Brush, Third 91Brush Trimmer 549Brush, Wire Gauge 92Buckling 92Bug 92Bug Trap 92Bunched Cable 95Bunsen Battery 59Bunsen Disc 92Bunsen's Photometer 412Buoy, Electric 93Burglar Alarm 16Burner, Electric Gas 93Burning 94Bus Bar 94Bus Rod 94Bus Wire 94Butt Joint 310Button, Call 98Button, Press 94Button, Push 93, 98Buzzer 94B. W. G. 94 C 95C. C. 109Cable 95Cable, Aerial 95Cable, Armature of 50Cable, Armor of 50Cable Box 95Cable, Bunched 95Cable, Capacity of 95Cable Clip 97Cable Core 96Cable, Duplex 96Cable, Flat 96Cablegram 96Cable Grip 96Cable Hanger 96Cable Hanger Tongs 97Cable, Suspension Wire of 97Cable Tank 97Cadmium Battery 60Calamine 97Cal Electricity 208Calibration 97Calibration, Absolute 97Calibration, Invariable 97Calibration, Relative 98Call Bell 78, 79, 98Call Bell, Extension 248Call Bell, Magneto 361Call Button 98Call, Thermo 530Call, Thermo-electric 531Callan Battery 60Calling Drop 98Calorie or Calory 98Calorimeter 98Calorimetric Photometer 412Calory or Calorie 98Cam, Listening 330Camacho's Battery 60Candle 99Candle, Concentric 99Candle, Debrun 99Candle, Decimal 99Candle, Electric 99Candle-foot 259Candle, German Standard 99Candle Holder 99Candle, Jablochkoff 100Candle, Jamin 100Candle, Meter 374Candle Power 100Candle Power, Nominal 101Candle Power, Rated 101Candle Power, Spherical 101Candle, Standard 101Candle, Wilde 101Caoutchouc 101Cap, Insulator 306Capacity, Carrying 108Capacity, Dielectric 102Capacity, Electric or Electrostatic 102Capacity, Instantaneous 102Capacity, Magnetic Inductive 346, 349Capillarity, Electro- 209Capillary Electrometer 224Capacity of a Telegraph Conductor 103Capacity of Cable 95Capacity of Polarization of a Voltaic Cell 103Capacity, Polarization 424Capacity, Residual 103Capacity, Specific Inductive 103Capacity, Storage 105, 495Capacity, Unit of 105Capillarity 105Capillary Telephone 525Carbon 106Carbon, Artificial 106Carbon Brush 90Carbon, Concentric 107Carbon, Cored 107Carbon Dioxide 107Carbon Holders 107Carbonic Acid, 108Carbonic Acid Gas 108Carbonization 107Carbonized Cloth 107Carbon, Platinized, Battery 69Carbon Resistance 463Carbon, Retort 471Carbons, Lamp, Flashing of Incandescent 257Carbon, Telephone 525Carbon Transmitter 549Carbon, Volatilization of 108Carburetted Hydrogen, Heavy 397Carcel 108Carcel Gas Jet 108Carcel Lamp 108Card, Compass 142Cardew Voltmeter 569Carré's Battery 60Carrying Capacity 108Cascade 108Cascade, Charging and Discharging Leyden Jars in 108Cascade, Gassiot's 275Case-hardening, Electric 109Cataphoresis 109Catch, Safety 175Cathode, etc. See Kathode 312Caustry, Galvano 109Cautery Battery 61Cautery, Electric 109Cautery, Galvano 109Cautery, Galvano-electric 109Cautery, Galvano-thermal 109Cell, Battery, Element of a 237Cell, Constant 109Cell, Electrolytic 109Cell, Porous 427Cell, Selenium 478Cell, Standard Voltaic 109Cell, Standard Voltaic, Daniells' 109Cell, Standard Voltaic, Latimer Clark's 110Central Station 493Central Station Distribution or Supply 112Centre of Gravity 112Centre of Gyration 112Centre of Oscillation 112Centre of Percussion 112Centrifugal Force 112Centrifugal Governor 113C. G. S. 113Chain, Molecular 380Chamber, Armature 42Chamber of Incandescent Lamp 113Change, Chemical 116Changer, Pole 425Changing Over Switch 500Changing Switch 500Chaperon, Lalande &, Battery 69Characteristic 169Characteristic Curve 113, 168Characteristic Curve, External 171Characteristic Curve of Converter 169Characteristic, Drooping 114Characteristic, External 114Characteristic, Internal 114Characteristics of Sound 114Charge 114Charge and Discharge Key 313Charge, Bound 115Charge Current 160Charge, Density of 115, 180Charge, Dissipation of 115Charge, Distribution of 115Charge, Free 115Charge, Negative 389Charge, Residual 116Charging Curve 170Chatterton's Compound 116Chemical Change 116Chemical Electric Meter 375Chemical, Electro-, Equivalents 244Chemical Element 236Chemical Energy 239Chemical Equivalent 244Chemical, Cautery Galvano 265Chemical Recorder 117Chemical Telephone 526Chemical Equivalent, Thermo- 245Chemistry 118Chemistry, Electro- 209Cheval, Force de 260Chicle 56Chimes, Electric 118Chloric Acid Battery 61Chloride, Ferric, Battery 63Chloride, Lead, Battery 66Chloride of Lime Battery 61Chlorimeter 73Choking Coil 132Chronograph, Electric 118Chromic Acid Battery 61Chromic Acid Battery Solutions 73Chromoscope 119Chutaux's Solution 119Cipher Code 130Circle, Azimuth 54Circle, Delezenne's 133Circle, Galvanic or Voltaic 119Circle, Magic 119Circuit 120Circuit, Astatic 120Circuit, Branch 121Circuit Breaker 121Circuit Breaker, Automatic 121Circuit Breaker, File 121Circuit Breaker, Mercury 121Circuit Breaker, Pendulum 121Circuit Breaker, Tuning-fork 121Circuit, Broken 125Circuit Changing Switch 500Circuit, Closed, Battery 61Circuit, Derivative 123Circuit, Derived 123Circuit, Electrostatic 123Circuit, Electric, Active 123Circuit, External 123Circuit, Grounded 123Circuit, Incomplete 125Circuit Indicator 298Circuit Induction, Open 303Circuit, Leg of 325Circuit, Local 331Circuit, Loop 125Circuit, Loop Break 125Circuit, Magnetic 340Circuit, Magnetic Double 340Circuit, Main 125Circuit, Main Battery 125Circuit, Metallic 125Circuit, Negative Side of 125Circuit, Open 125Circuit, Positive Side of 125Circuit, Recoil 125Circuit, Return 125Circuits, Forked 126Circuit, Short 482Circuit, Shunt 123, 126Circuit, Simple 126Circuits, Parallel 123, 126Circuit, Voltaic 126Circuit Working, Short 482Circular Bell, 79Circular Current, 160Circular, Mil 379Circular Units 126, 555Circumflux 126Clamp 126Clark's Compound 126Cleansing, Fire 257Clearance Space, 489Cleat, Crossing 127Cleats 127Cleavage, Electrification by 127Clip, Cable 97Clock, Annunciator 35Clock, Controlled 127Clock, Controlling 127Clock, Electric Annunciator 127Clock, Electrolytic 128Clock, Master 127Clock, Secondary 127Clock, Self-winding, Electric 128Clockwork Feed 128Cloisons 128Closed Circuit Battery 61Closed Coil Armature 43Closure 128Closure Contraction, Kathodic 312Cloth, Carbonized 107Club-foot Electro-magnet 217Clutch 128Clutch, Electro-magnetic 128Coatings of a Condenser, or Prime Conductor 129Cockburn Fuse 263Code, Cipher 130Code, S. N. 486Code, Telegraphic 130, 511Coefficient 130Coefficient, Apparent, of Magnetic Induction 346Coefficient, Economic 130, 204, 205Coefficient of Electrical Energy 205Coefficient of Expansion 247Coefficient of Induced Magnetization 359, 354Coefficient of Magnetic Induction 346, 349Coefficient of Mutual Induction 301Coefficient of Self-induction 298Coercitive Force 471Coercive Force 471Coercive or Coercitive Force 131Coil and Plunger 131Coil and Coil Plunger 131Coil and Plunger, Differential 132Coil, Armature 43Coil, Choking 132Coil, Earth 133Coil, Electric 133Coil, Exploring 350Coil, Flat 133Coil, Induction 133Coil, Induction, Inverted 136Coil, Induction, Telephone 137Coil. Kicking 132Coil, Magnet 336Coil, Magnetizing 137Coil, Reaction 132Coil, Resistance 137Coil, Resistance, Standard 464Coil, Rhumkorff 138Coil, Ribbon 138Coils, Bisected 132Coils, Compensating 138Coils, Sectioned 138Coils, Henry's 138Coils, Idle 295Coil, Single, Dynamo 202Coil, Spark 489Coil, Sucking 132Collecting Brush 90Collecting Ring 139Collector 139Colombin, 139Colophony 460Colors of Secondary Plates 478Column Battery 61Column, Electric 139Comb 140Combined Resistance 464Comb Protector 437Commercial Efficiency 204Commercial Efficiency of Dynamo 195Commercial Wheatstone Bridge 86Common Reservoir 460Communicator 140Commutation, Diameter of 182Commutator 140Commutator Ammeter 26Commutator Bars 140, 56Commutator, Flats in 140Commutator, High Bars of 289Commutator, Neutral Line of 390Commutator, Neutral Point of 390Commutator of Current Generators and Motors 140Commutators, Bars of 56Commutator Segments 56Commutator, Split Ring 141Commuted Current 160Commuter 140Commuting Transformer 547Compass 141Compass, Azimuth 141Compass, Boxing the 86Compass Card, 142Compass, Declination 142Compass, Inclination 142Compass, Mariners' 142Compass, Points of the 143Compass, Spirit 143Compass, Surveyors 143Compass, Variation of the 32, 558Compensating Coils 138Compensating Magnet 336Compensating Poles 426Compensating Resistance 144Complementary Distribution 144Complete Alternation 23Component 144Components of Earth's Magnetism 356Composition of Forces 260Compound Arc 39Compound, Binary 81Compound, Chatterton's 116Compound, Clark's 126Compound Dynamo 195Compounding, Over- 399Compound Magnet 336Compound or Compound Wound Motor 382Compound Winding 578Concentration of Ores, Magnetic 340Concentrator, Magnetic 340Concentric Candle 99Concentric Carbon 107Condenser 144Condenser, Coatings of a, or Prime Conductor 129Condenser, Epinus' 242Condenser, Plate 417Condenser, Sliding 144Condenser, Varley's 559Condensing Electroscope 233Conductance 144Conductance, Magnetic 340Conduction 144Conduction, Electrolytic 215Conductive Discharge 187Conductivity 144Conductivity, Magnetic 340Conductivity, Specific 145Conductivity, Unit of 145Conductivity, Variable 145Conductor 145Conductor, Anti-induction 145Conductor, Branch 87Conductor, Capacity of a Telegraph 103Conductor, Conical 145Conductor, Imbricated 146Conductor, Interpolar 307Conductor, Leakage 325Conductor, Prime 146, 434Conductors, Equivalent 146Conductors, Lamination of Armature 319Conductors, Service 481Conductor, Underground 552Congress Ohm 395Congress Volt 568Conical Conductor 145Conjugate 146Connect 146Connection, Cross 158Connection, Relay 457Connector 146Consequent Points 422Consequent Poles 146, 478Conservation of Electricity 146Conservation of Energy 239Constant Current 160Constant Current Alternator 24Constant Current Regulation 454Constant, Dielectric 183Constant, Galvanometer 268Constant Potential 429Constant Potential Regulation 455Constant, Time 54lContact Breaker 121, 146Contact, Electric 147Contact Electricity 147Contact Faults 147Contact Key, Double 314Contact Key, Sliding 316Contact Lamp 320Contact, Line of 330Contact Point 147Contact Potential Difference 147Contact Ring 473Contact Spring 148Contact Series 147Contact Theory 148Continuity, Magnetic 340Continuous Alternating Transformer 547Continuous Current 161Continuous Current Transformer 384, 547Contraction, Anodic Closure 36Contraction, Anodic Duration 36Contraction, Anodic Opening 36Contraction, Kathodic Closure 312Contraction, Kathodic Duration 312Contractures 148Contraplex Working 580Control, Electro-magnetic 218Control, Gravity 281Controlled Clock, 127Controlling Clock 127Controlling Field 148Controlling Force 148Controlling Magnet 185, 336Control, Magnetic 341Control, Spring 492Convection, Electric 149Convection, Electrolytic 149, 214Convection of Heat, Electric 149Convective Discharge 187Conversion, Efficiency of 205Converter 149Cooling Box 151Co-ordinates, Origin of 391Co-ordinates, System of 150Copper 151Copper Bath 152Copper Stripping Bath 152Copper Voltameter 563Cord Adjuster 152Cord, Flexible 152Cord, Pendant 405Core 152Core, Armature 43Core, Cable 96Cored Carbon 107Core-discs 152Core-discs, Perforated 154Core-discs, Pierced 152Core-discs, Toothed 154Core, Laminated 154Core, Magnet 336Core Ratio 154Core, Ribbon 154Core, Ring 155Cores, Krizik's 318Core, Stranded 155Core, Tangentially Laminated 155Core Transformer 155Core, Tubular 155Corpusants 155Corresponding Points 422Coulomb 155Coulomb's Law of Electrostatic Attraction and Repulsion 155Coulomb's Law of Magnetic Attraction and Repulsion 338Coulomb's Torsion Balance 544Coulomb, Volt- 568Counter, Electric 156Counter Electro-motive Force 156, 228Counter-electro-motive Force Lightning Arrester 329Counter Inductive Effect 204Couple 156Couple, Astatic 157Couple, Axial 544Couple, Magnetic 341Couple, Moment of 544Couple, Thermo-electric 532Couple, Voltaic or Galvanic 156Coupling 259Coupling of Dynamo 201C. P. 157Crater 157Creep, Diffusion 184Creeping 157Creeping, Magnetic 341Creeping of Magnetism 356Crith 157Critical Current 161Critical Distance of Alternative Path 190Critical Resistance 464Critical Speed 157Critical Value, Villari's 561Crookes' Dark Space 489Cross 157Cross-connecting Board 157Cross Connection 158Cross Induction 298Crossing Cleat 127Crossing Wires 158Cross-magnetizing Effect 158, 298Cross-over Block 158Cross, Peltier's 405Cross Talk 158Crucible, Electric 158Crystallization, Electric 158Cube, Faraday's 249Culture. Electro- 209Cunynghame's Ammeter 26Cup, Mercury 371Cup, Porous 159, 426Current 159Current, After 159Current, Alternating 159Current, Alternating System 23Current, Alternative 563Current Arc, Alternating 23Current, Atomic 160Current, Break Induced 162Current, Charge 160Current, Circular 160Current, Commuted 160Current, Constant 160Current, Continuous 161Current, Continuous, Transformer 384Current, Critical 161Current, Daniel 161Current, U. S. Or Siemens' Unit 161Current, Demarcation 161Current Density 161Current, Derived 164Current, Diacritical 161Current, Diaphragm 161Current, Direct 162Current, Direct Induced 162Current, Direction of 162Current, Displacement 162Current, Extra 162Current, Faradic 162Current, Field of Force of a 255Current, Foucault 163Current, Franklinic 163Current Generator 277Current, Induced 163Current Induction 163Current Induction, Unipolar 553Current Intensity 163Current, Inverse Induced 163Current, Jacobi's Unit of 163Current, Joint 163Current, Linear 164Current, Make and Break 164, 367Current, Make Induced 163Current Meter 164, 375Current Meter, Alternating 373Current, Negative 164Current, Nerve and Muscle 164Current, Opposed 164Current, Partial 164Current, Polarizing 164Current, Positive 164Current, Power of Periodic 433Current, Pulsatory 164Current, Rectified 164Current, Rectilinear 165Current, Redressed 165Current Regulation, Constant 454Current, Reverse Induced 163Current Reverser 165Currents, Ampere 30Currents, Ampérian 165Currents, Angular. 165Currents, Angular, Laws of 165Currents, Earth 166Current, Secondary 166Current, Secretion 166Currents, Eddy 163Currents, Eddy Displacement 162Currents in Parallel Circuits, Independence of 297Current, Sinuous 166Current, Sheet 166Current, Shuttle 483Currents, Local 163Currents, Local 331Currents, Multiphase 166Currents, Natural 166, 389Currents, Nerve 390Currents of Motion 167Currents of Rest 167Currents, Orders of 167Currents, Parasitical 163Currents, Polyphase 167Currents, Rotatory 167Currents, Thermo-electric 167Current Streamlets 495Current, Swelling 167Current, Tailing 501Current, Undulatory 167Current, Unit 167Current, Wattless 168Curve, Arrival 168Curve, Characteristic 113, 168Curve, Characteristic, of Converter 169Curve, Charging 170Curve, Discharging 170Curve, Elastic 206Curve, Electro-motive Force 170Curve, External Characteristic . 171Curve, Harmonic 174, 485Curve, Horse Power 171Curve, Isochasmen 171Curve, Life 171Curve, Load 172Curve, Magnetization 172Curve of Distribution of Potential in Armature 172Curve of Dynamo 173Curve of Saturation of Magnetic Circuit 174Curve of Sines 173, 485Curve of Torque 174Curve, Permeability Temperature 174Curve, Sine 174, 485Curve, Sinusoidal 174, 485Curves, Magnetic 341Cut In 174Cut Out 174Cut Out, Automatic 175, 475Cut Out, Magnetic 175Cut Out, Plug 175Cut Out, Safety 175Cut Out, Spring Jack 493Cut Outs, Time 541Cut Out, Wedge 175Cutting of Lines of Force 175Cycle of Alternation 175Cycle of Magnetization 360Cylinder, Armature 43Cylinder, Electric Machine 333Cylindrical Armature 45Cystoscopy 175 Damper 176Damping 176Damping Magnet 336Daniell's Standard Voltaic Cell 109Dark Space, Faraday's 249D'Arsonval's Battery 62Dash-pot 176Dead Beat 38, 176Dead Beat Discharge 187Dead Earth 176, 203Dead Point of an Alternator 177Dead Turns 177Dead Turns of a Dynamo 551Dead Wire 177Death, Electrical 177Debrun Candle 99Decalescence 177Decay of Magnetism 356Deci 177Decimal Candle 99Declination, Angle of 32-177Declination Compass 142Declination, Magnetic 342Declination Map 309Declination of the Magnetic Needle 178Decomposition 178Decomposition, Electrolytic 178Decrement 178De-energize 178Deflagration 178Deflagrator, Hare's 73Deflecting Field 178Deflection 178Deflection Method 178Deflection of Magnet 337Degeneration, Reaction of 179Degradation of Energy 239Deka 179De la Rive's Floating Battery 179De la Rue Battery 62Delaurier's Solution 179Delezenne's Circle 133Demarcation Current 161Demagnetization 179Density, Current 161Density, Electrical 115Density, Electric Superficial 180Density, Field 252Density, Magnetic 342Density of Charge 115, 180Dental Mallet, Electric 180Deposit, Electrolytic 180Deposit, Nodular 392Depolarization 180Depolarizing Fluid 258Derivation, Points of 180, 423Derivative Circuit 123Derived Circuit 123Derived Current 164Derived Units 555Desk Push 180Detector 180Detector, Lineman's 180Deviation of Discharge 188Deviation, Quadrantal 180Deviation, Semi-circular 181Device, Safety 475Dextrotorsal 181Diacritical 181Diacritical Current 161Diagometer 181Diagnosis, Electro- 181, 210Diagram, Thermo-electric 532Dial Telegraph 505Diamagnetic 181Diamagnetic Polarity 181, 423Diamagnetism 182Diameter of Commutation 182Diapason, Electric 182Diaphragm 182Diaphragm Current 161Dielectric, 182Dielectric Capacity 102Dielectric Constant 183Dielectric, Energy of 183Dielectric Polarization 183Dielectric Resistance 183, 464Dielectric Strain 183Dielectric Strength 183Dielectric Stress 496Differential Arc Lamp 320Differential Coil and Plunger 132Differential Galvanometer 268Differentially Wound Bell, 79Differential Magnetometer 365Differential Motor 382Differential Relay 457Differential Thermo-electric Pile 533Differential Winding Working 183Diffusion 184Diffusion, Anodal . 35Diffusion Creep 184Digney Unit of Resistance 464Dimensions and Theory of Dimensions 184Dimmer 185Diode Working 580Dioxide, Carbon 107Dioxide, Sulphur 497Dip, Magnetic 342, 346Dip of Magnetic Needle 185Dipping 185Dipping Needle 185Direct Current 162Direct Current Dynamo 197Direct Induced Current, . 162Direct Reading Galvanometer 269Directing Magnet 185Direction 185Direction of Current 162Direction, Positive 428Directive Power 187Disc, Arago's 38Disc, Armature 43Disc, Bunsen 92Disc, Dynamo 197Disc, Faraday's 249Discharge and Charge Key 313Discharge, Brush 187Discharge, Conductive 187Discharge, Convective 187Discharge, Dead Beat 187Discharge, Disruptive 187Discharge, Duration of 188Discharge, Glow 187Discharge, Impulsive 188Discharge Key, Kempe's 315Discharge, Lateral 188Discharge of Magnetism 356Discharge, Oscillatory 188Discharger 188Discharger, Henley's Universal 189Discharger, Universal 189Discharger, Universal, Henley's 189Discharge, Silent 187, 189, 206Discharge, Spark 189Discharge, Surging 188Discharging Curve 170Discharging Rod 189Discharging Tongs 189Disconnection 189Discontinuity, Magnetic 342Discovery, Oerstedt's 394Disc Winding 579Dispersion Photometer 412Displacement Current 162Displacement, Electric 188Displacement, Oscillatory 398Disruptive Discharge 187Disruptive Tension 189Dissimulated Electricity 189Dissipation of Charge 115Dissociation 189, 535Distance, Critical, of Alternative Path 190Distance, Explosive 190Distance, Sparking 190Distance, Striking 496Distant Station 493Distillation 190Distortion of Field 252Distributing Box 190Distributing Switches 190Distribution, Complementary 144Distribution, Isolated 309Distribution of Charge 115Distribution of Electric Energy, Systems of 190Distribution of Magnetism, Lamellar, 357Distribution of Magnetism, Solenoidal 358Distribution of Supply, Central Station 112Door Opener, Electric 190Dosage, Galvanic 190Double Break Switch 500Double Carbon Arc Lamp 191Double Contact Key 314Double Curb Working 581Double Fluid Theory 191Double Fluid Voltaic Cell 191Double Magnetic Circuit 340Double Needle Telegraph 506Double Plug 191Double Pole Switch 500Double Tapper Key 314Double Touch, Magnetization by 358Double Trolley 549Double Wedge 191Doubler 191D. P. 191Drag 191Drag of Field 254Dreh-Strom 191Drill, Electric 191Drip Loop 192Driving Horns 192Dronier's Salt 192Drooping Characteristic 114Drop, Annunciator 35Drop, Automatic 192Drop, Calling 98Drum Armature 45Drum, Electric 193Dry Battery 63Dry Pile, Zamboni's 581Dub's Laws 193Duct 193Duplex Bridge Telegraph 506Duplex Cable 96Duplex Differential Telegraph 507Duplex Telegraph, 506Duration Contraction, Kathodic 312Duration of Electric Spark 490Dyad 193Dyeing, Electric 193Dynamic Electricity 193Dynamic, Electro- 211Dynamic Induction, Magnetic 347Dynamo, Alternating Current 193Dynamo, Alternating Current Regulation of 195Dynamos, Battery of 68Dynamo, Commercial Efficiency of 195Dynamo, Compound 195Dynamo, Coupling of 201Dynamo, Curve of 173Dynamo, Dead Turns of a 551Dynamo, Direct Current 197Dynamo, Disc 197Dynamo-electric Machine 197Dynamo, Electroplating 198Dynamo, Equalizing 198Dynamo, Field and Armature Reaction of 450Dynamo, Far Leading 198Dynamo or Magneto-electric Generator, Flashing in a 257Dynamo, Inductor 199Dynamo, Interior Pole 199Dynamo, Iron Clad 200Dynamo, Ironwork Fault of a 308Dynamo, Motor 200Dynamo, Multipolar 200Dynamo, Non-polar 200Dynamo, Open Coil 200Dynamo, Overtype 399Dynamos, Regulation of 455Dynamo, Ring 200Dynamo, Self Exciting 201Dynamo, Separate Circuit 201Dynamo, Separately Excited 201, 479Dynamo, Series 201Dynamo, Shunt 202Dynamo, Single Coil 202Dynamo, Tuning Fork 202Dynamo, Unipolar 202, 553Dynamograph 199Dynamometer 200Dyne 203 Earth 203Earth Coil 133Earth Currents 166Earth, Dead 176, 203Earth, Magnetization by 359Earth, Partial 203, 404Earth Plate 203Earth Return 203Earth's Magnetism, Components of 356Earth, Solid 203Earth, Swinging 203Earth, Total 203Ebonite 203Eccentric Iron Disc Ammeter 27Economic Coefficient 130, 204, 205Eddy Currents 163Eddy Displacement Currents 162Ediswan 204Edison Effect 204Edison-Lalande Battery 69Eel, Electric 204Effect, Acheson 208Effect, Counter-inductive 204Effect, Cross-magnetizing 158, 298Effect, Edison 204Effect, Faraday 249Effect, Ferranti 251Effect, Hall 284Effect, Joule 311Effect, Kerr 235, 312Effect, Mordey 381Effect, Page 401Effect, Peltier 404Effect, Photo-voltaic 415Effect, Seebeck 478Effect, Skin 486Effect, Thomson 538Effect, Voltaic 563Efficiency 204Efficiency, Commercial 204Efficiency, Electrical 205Efficiency, Gross 205Efficiency, Intrinsic 205Efficiency, Net 205Efficiency of Conversion 205Efficiency of Secondary Battery Quantity 205Efficiency of Secondary Battery, Real 205Efflorescence 206Effluvium, Electric 206Egg, Philosopher's 409Elastic Curve 206Elasticity, Electric 206Electrepeter 206Electric, Absolute, Potential 429Electric Absorption 8Electric Actinometer 11Electric Alarm 17Electrical Classification of Elements 237Electrically Controlled Valve 558Electric Ammunition Hoist 29Electric Analysis 32Electric Analyzer 32Electric Annealing 34Electric Annunciator Clock 127Electric Arc Blow-pipe 84Electric Aura 53Electric Automatic Fire Extinguisher 257Electric Axis 54Electric Balance 577Electric Bath, Bipolar 57Electric Bath, Multipolar 57Electric Bath, Unipolar 57Electric Bell 79Electric Bell, Automatic 78Electric Bioscopy 82Electric Blasting 83Electric Bleaching 83Electric Boat 84Electric Boiler Feed 84Electric Branding 87Electric Brazing 87Electric Breath Figures 89Electric Breeze 89Electric Buoy 93Electric Candle 99Electric Case Hardening 109Electric Cautery 109Electric Chimes 118Electric Chronograph 118Electric Circuit, Active 123Electric Clock, Self-winding 128Electric Coil 133Electric Column 139Electric Contact 147Electric Convection 149Electric Convection of Heat 149, 286Electric Counter 156Electric Crucible 158Electric Crystallization 158Electric Death 177Electric Density 115Electric Dental Mallet 180Electric Diapason 182Electric Displacement 189Electric Door Opener 190Electric Double Refraction 454Electric Drill 191Electric Drum 193Electric Dyeing 193Electric Eel 204Electric Efficiency 205Electric Effluvium 206Electric Elasticity 206Electric Endosmose 238Electric Energy 239Electric Energy, Coefficient of 205Electric Energy, Systems of Distribution of 190Electric Engraving 245Electric Entropy 242Electric Etching 245Electric Evaporation 246Electric Excitability of Animal Systems 247Electric Exosmose 247Electric Expansion 247Electric Fire Alarm, Automatic 257Electric Floor Matting 369Electric Fluid 258Electric Fly or Flyer 259Electric Fog 259Electric Furnace 263Electric Fuse 264Electric Gas Burners 93Electric Headlight 285Electric Head Bath 284Electric Heat 285Electric Heater 286Electric Horse Power 290Electric Image 296Electric Incandescence 297Electric Influence 305Electric Insulation 305Electricities, Separation of 479Electricity 206Electricity, Animal 33Electricity, Atmospheric 51Electricity, Cal 208Electricity, Conservation of 146Electricity, Contact 147Electricity, Dissimulated 189Electricity, Dynamic 193Electricity, Frictional 262Electricity, Latent 323Electricity, Negative 389Electricity, Plant 317Electricity, Positive 428Electricity, Specific Heat of 491Electricity, Static 493Electricity, Storage of 495Electricity, Voltaic 563Electricity, Vitreous 562Electric Machine, Plate 417Electric Machine, Wimshurst 577Electric Mains 367Electric Mass 368Electric Matter 368Electric Meter, Chemical 375Electric Meter, Thermal 375Electric Meter, Time 375Electric Mortar 382Electric Motor 382Electric or Electrostatic Capacity 102Electric Organ 397Electric Oscillations 398Electric Osmose 398Electric Pen 405Electric Pendulum 405Electric Piano 415Electric Picture 415Electric Pistol 416Electric Popgun 282Electric Portrait 415Electric Potential Difference 429Electric Potential, Unit of 432Electric Power 433Electric Pressure 434Electric Probe 435Electric Prostration 437Electric Protector 437Electric Radiometer 447Electric Ray 450Electric Rectification of Alcohol 18Electric Reduction of Ores 453Electric Reduction of Phosphorous 410Electric Register 454Electric Residue 116, 460Electricity, Resinous 461Electric Resonance 468Electric Resonator 470Electric Rings 392Electrics 208Electric Saw 476Electric Screen, 476Electric Shadow 480Electric Shock 482Electric Shower Bath 57Electric Soldering 487Electric Spark, Duration of 490Electric Sphygmophone 491Electric Storms 495Electric Striae 496Electric Subway 496Electric Subway, Underground 552Electric Sunstroke 497Electric Superficial Density 180Electric Swaging 499Electric Tele-barometer 504Electric Telemanometer 521Electric Telemeter 521Electric Tempering 527Electric Tension 529Electric Thermometer 535Electric Thermostat 537Electric Torpedo 543Electric Tower 545Electric Transmission of Energy 240Electric Trumpet 550Electric Tube 550Electric Typewriter 551Electric Unit of Work 580Electric Varnish 559Electric Welding 574Electric Whirl 577Electric Wind 578Electrification 208Electrification by Cleavage 127Electrification by Pressure 434Electrified Body, Energy of an . 241Electrization 208Electro-biology 208Electro-capillarity 209Electro-chemical Equivalents 209, 244Electro-chemical Series 209Electro-chemistry 209Electro-culture 209Electrode 210Electrode, Indifferent 210Electrodes, Erb's Standard of 210Electrodes, Non-polarizable 210Electrodes, Shovel 483Electrode, Therapeutic 210Electro-diagnosis 181, 210Electro-dynamic 211Electro-dynamic Attraction and Repulsion, 211Electro-dynamic Rotation of Liquids 474Electro-dynamometer, Siemens' 212Electro-gilding 277Electro-kinetic 211Electrolier 212Electrolysis 212Electrolysis, Laws of 213Electrolyte 214Electrolytic Analysis 214Electrolytic Cell 109Electrolytic Clock 128Electrolytic Conduction 215Electrolytic Convection 149, 214Electrolytic Deposit 180Electrolytic Iron 308Electrolytic Resistance 464Electro-magnet 215, 337Electro-magnet, Annular 216Electro-magnet, Bar 217Electro-magnet, Club-foot 217Electro-magnet, Hinged 217Electro-magnet, Hughes' 291Electro-magnetic Ammeter 27Electro-magnetic and Magnetic Equipotential Surface 244Electro-magnetic Attraction and Repulsion 217Electro-magnetic Brake 86Electro-magnetic Clutch 128Electro-magnetic Control 218Electro-magnetic Eye 248Electro-magnetic Field of Force 218Electro-magnetic Force 260Electro-magnetic Gun 282Electro-magnetic Induction 218, 299Electro-magnetic Inertia 305Electro-magnetic Induction, Mutual 302Electro-magnetic Interrupter for Tuning Fork 307Electro-magnetic Leakage 219Electro-magnetic Lines of Force 219Electro-magnetic Liquids, Rotation of 475Electro-magnetic Meter 375Electro-magnetic Quantity 445Electro-magnetic Quantity, Practical Unit of 445Electro-magnetic Shunt . 483Electro-magnetic Stress 219, 496Electro-magnetic Theory of Light 219Electro-magnetic Unit of Energy 220Electro-magnetic Vibrator 561Electro-magnetic Waves, 573Electro-magnet, Ironclad 219Electro-magnetism 220Electro-magnet, Joule's 337Electro-magnet, Long Range 220Electro-magnet, One Coil 219Electro-magnet, Plunger 220Electro-magnet, Polarized 220Electro-magnets, Interlocking 221Electro-magnets, Multiple Wire Method of Working 388Electro-magnet, Stopped Coil 221Electro-magnets, Surgical 222Electro-mechanical Bell 80Electro-mechanical Equivalent 244Electro-medical Baths 222Electro-medical Battery, Pulvermacher's 69Electro-metallurgy 222Electrometer 222Electrometer, Absolute 222Electrometer. Attracted Disc 223Electrometer, Capillary 224Electrometer Gauge 226Electrometer, Lane's 226Electrometer, Quadrant 226Electrometer, Thermo- 536Electrometer, Weight 223Electro-motive Force 227Electro-motive Force, Counter- 228Electro-motive Force Curve 170Electro-motive Force, Impressed 297Electro-motive Force, Motor 384Electro-motive Force. Oscillatory 398Electro-motive Force, Transverse 549Electro-motive Force, Unit 228Electro-motive Intensity 228Electro-motive Potential Difference 429Electro-motive Series 228Electro-motograph 229Electro-motor 229Electro-muscular Excitation 229Electro-negative 229Electro-optics 229Electrophoric Action 230Electrophorus 230Electro-physiology 231Electroplating 231, 418Electroplating Dynamo 198Electro-pneumatic Signals 231Electropoion Fluid 232Electro-positive 232Electro-puncture 232Electro-receptive 232Electroscope 232Electroscope, Bennett's 233Electroscope, Bohenberger's 233Electroscope, Condensing 233Electroscope, Gold Leaf 233Electroscope, Pith Ball 234Electrostatic Attraction and Repulsion 234Electrostatic Attraction and Repulsion. Coulomb's Law of 155Electrostatic Circuit 123Electrostatic Equipotential Surface 244Electrostatic Field of Force 254Electrostatic Force 260Electrostatic Induction 302Electrostatic Induction, Coefficient of 234Electrostatic Induction, Mutual 303Electrostatic Lines of Force 234Electrostatic Quantity 445Electrostatic Refraction 235Electrostatics 235Electrostatic Series 235Electrostatic Stress 236, 496Electrostatic Telephone 526Electrostatic Voltmeter 571Electro-thermal Equivalent 245Electro-therapeutics or Therapy 236Electrotonic State 493Electrotonus 236Electrotype 236Element, Chemical 236Element, Galvanic 264Element, Mathematical 237Element, Negative 390Element of a Battery Cell 237Element, Positive 277Elements, Electrical Classification of 237Elements, Magnetic 342Elements of Battery 63Elements, Thermo-electric 237Element, Voltaic 237Elias' Method of Magnetization 360Elongation 237, 540Elongation, Magnetic 344Embosser, Telegraph 237E. M. D. P. 238E. M. F. 238Energy 238Energy, Atomic 238Energy, Chemical 239Energy, Conservation of 239Energy, Degradation of 239Energy, Electric 239Energy, Electrical, Coefficient of 205Energy, Electric Transmission of 240Energy, Electro-magnetic, Unit of 220Energy, Kinetic 241Energy, Mechanical 241Energy Meter 375Energy, Molar 241Energy, Molecular 241Energy of an Electrified Body 241Energy of Dielectric 183Energy of Position 211Energy of Stress 241Energy, Physical 241Energy, Potential, or Static 241Energy, Radiant 446Energy, Thermal 242End-on Method 238End or Pole, Marked 368Endosmose, Electric 238End Play 238End, Unmarked 556English Absolute or Foot Second Unit of Resistance 465Engraving, Electric 245Entropy 242Entropy, Electric 242Epinus Condenser 242E. P. S. 243Equator, Magnetic 344Equator of Magnet 337Equipotential 244Equipotential Surface 498Equipotential Surface, Electrostatic 244Equipotential Surface, Magnetic and Electro-magnetic 244Equalizer 243Equalizer, Feeder 251Equalizing Dynamo 198Equivalent, Chemical 116, 244Equivalent Conductors 146Equivalent, Electro-thermal 245Equivalent, Joule's 311Equivalent Resistance 465Equivalents, Electro-chemical 209, 244Equivalent, Thermo-chemical 245Equivalent, Water 572Equivolt 245Erb's Standard of Electrodes 210Erg 245Erg-ten 245Error, Heating 286Escape 245Essential Resistance 465, 466Etching, Electric 245Ethene 397Ether 246Eudiometer 246Evaporation, Electric 246Ewing's Theory of Magnetism 356Exchange, Telephone 246Excitation, Electro-muscular 229Excitability, Faradic 246Excitability, Galvanic 247Excitability of Animal System, Electric 247Exciter 247Exosmose, Electric 247Expansion, Coefficient of 247Expansion, Electric 247Experiment, Franklin's 261Experiment, Hall's 284Experiment, Kerr's 312Experiment, Matteueci's 369Experiments, Hertz's 470Experiment, Volta's Fundamental 567Experiment with Frog, Galvani's 262Exploder 247Explorer 247Exploring Coil 350Explosive Distance 190Extension Bell Call 248Extension, Polar 423External Characteristic 114External Characteristic Curve 171External Circuit 123External Resistance 465, 467Extinguisher, Automatic Electric Fire 257Extra Current 162Extra-polar Region 454Eye, Electro-magnetic 248Eye, Selenium 478 Facsimile Telegraph 510Factor, Armature 45Fahrenheit Scale 248Fall of Potential 430False Poles, Magnetic 350Farad 248Faraday, Effect 249Faraday's Cube 249Faraday's Dark Space 249, 489Faraday's Disc 249Faraday's Net 250Faraday's Ring 473Faraday's Transformer 250Faraday's Voltameter 250Faradic 250Faradic Battery 63Faradic Brush 251Faradic Current 162Faradic Excitability 246Faradization 251Faradization, Galvano- 265Far Leading Dynamo 198Fault of a Dynamo, Ironwork 308Faults 251Faults, Contact 147Feed Clockwork 128Feeder 251Feeder, Equalizer 251Feeder, Main or Standard 251Feeder, Negative 251Feeder, Neutral 251Feeder, Positive 251Feeder, Switch 500Feet, Ampere 30Ferranti Effect 251Ferric Chloride Battery 63Ferro-magnetic 252Fibre and Spring Suspension 252Fibre Suspension 252Field, Air 252Field, Alternating 252Field and Armature Reaction of Dynamo, 450Field, Controlling 148Field, Deflecting 178Field Density 252Field, Distortion of 252Field, Drag of 254Field, Intensity of a Magnetic 306Field Magnet 337Field of Force . 254Field of Force, Electro-magnetic 218Field of Force, Electrostatic 254Field of Force, Magnetic 344Field of Force of a Current 255Field of Force, Uniform 553Field, Pulsatory 256Field, Rotating 256Field, Stray 256, 495Field, Uniform 256Field, Uniform Magnetic 345Field, Waste 256Figure of Merit 256Figures, Haldat's 284Figures, Lichtenberg's 327Figures, Magnetic 345Filament 256Filament, Magnetic 345Filaments, Paper 402File, Circuit Breaker 121Finder, Position 427Finder, Range 447Finder, Wire 580Fire Alarm, Electric Automatic 257Fire and Heat Alarm 17Fire Extinguisher, Electric Automatic 257Fire Cleansing 257Fire, St. Elmo's 494Fishing Box 311Flashing in a Dynamo or Magneto-Electric Generator 257Flashing of Incandescent Lamp Carbons 257Flashing Over 258Flash, Side 484Flat Cable 96Flat Coil 133Flat Ring Armature 45Flats 258Flats in Commutator 140Flexible Cord 152Floating Battery, De la Rive's 179Floating Magnets, Meyer's 370Floor Matting, Electric 369Floor Push 258Fluid, Depolarizing 258Fluid, Electric 258Fluid, Electropoion 232Fluid, Insulator. 306Fluid, North Magnetic 357Fluids, Magnetic 345Fluid, South Magnetic 356Fluid Theory, Single 486Fluorescence 258Flush Boxes 258Fluviograph 259Flux, Magnetic 345Fly or Flyer, Electric 259Foci Magnetic 259Fog, Electric 259Following Horns 259Foot-candle 259Foot, Mil- 379Foot-pound 259Foot-step 259Force 259Force, Annular 544Force, Axial 544Force, Centrifugal 112Force, Coercive or Coercitive 131-471Force, Controlling 148Force, Counter-electro-motive 156Force de Cheval 260Force, Electro-magnetic 260Force, Electro-motive 227Force, Electro-motive, Transverse 549Force, Electrostatic 260Force, Field of 254Force, Field of, of a Current 255Force, Field of, Electrostatic 254Force, Kapp Line of 312Force, Lines of 330Force, Magnetic 346Force, Magnetic Field of 344Force, Magnetic Lines of 348Force, Magneto-motive 365Force, Motor Electro-motive 384Force of Polarization, Back Electro-motive 156Force, Oscillatory, Electro-motive 398Force, Photo-electro-motive 410Forces, Composition of 260Forces, Parallelogram of 260Forces, Resolution of 261Force, True Contact 549Force, Tubes of 261Force, Unit of 261Forked Circuits 126Fork, Tuning, Dynamo 202Forming 261Formula of Merit 256Foucault Current 163Foundation Ring 261Fourth State of Matter 261Frame 261Frame, Resistance 465Franklinic Current 163Franklin's Experiment 261Franklin's Plate 262Franklin's Theory 262-486Free Charge 115Free Magnetism 356Frequency 262Frequency, High 289Frictional Electricity 262Frictional Electric Machine 333Frictional Heating 262Friction Gear, Magnetic 276Friction, Magnetic 295-346Fringe 262Frog, Galvani's Experiment with 262Frog, Rheoscopic 262Frying 263Fulgurite 263Fuller's Battery 63Fulminating Pane 262Fundamental Unit 554Furnace, Electric 263Fuse Block 175Fuse Board 263Fuse Box 263Fuse, Cockburn 263Fuse, Electric 264Fuse Links 330Fuse, Safety 175-475 Galvanic 264Galvanic Action, Volta's Law of 568Galvanic Dosage 190Galvanic Element 264Galvanic Excitability 247Galvanic or Voltaic Battery 76Galvanic or Voltaic Circle 119Galvanic or Voltaic Couple 156Galvanic Polarization 265Galvani's Experiment with Frog 262Galvanism 265Galvanization 265Galvanization, Labile 265Galvanized Iron 265Galvano-cautery 109Galvano-cautery, Chemical 265Galvano-electric Cautery 109Galvano-faradization 265Galvanometer 265Galvanometer, Absolute 266Galvanometer, Aperiodic 266Galvanometer, Astatic 266Galvanometer, Ballistic 267Galvanometer Constant 268Galvanometer, Differential 268Galvanometer, Direct Reading 269Galvanometer, Marine 269Galvanometer, Mirror 271Galvanometer, Potential 269Galvanometer, Proportional 269Galvanometer, Quantity 269Galvanometer, Reflecting 270Galvanometer, Shunt 271-483Galvanometer, Sine 271Galvanometer, Tangent 272Galvanometer, Torsion 273-544Galvanometer, Upright 274Galvanometer, Vertical 274Galvanometer, Volt and Ampere Meter 274Galvano-plastics 275Galvano-puncture 232-275Galvanoscope 275Galvano-thermal Cautery 100Gap, Spark 490Gas Battery 63Gas Battery, Grove's 281Gas Burner, Electric 93Gas, Carbonic Acid 108Gas, Electrolytic 275Gases, Magnetism of 357Gases, Mixed 275Gas Jet, Carcel 108Gas, Olefiant 397Gassing 275Gassiot s Cascade 275Gastroscope 275Gas Voltameter 564Gauge, Battery 64Gauge, Electrometer 226Gauss 275Gauss' Principle 276Gauss, Tangent Positions of 276Gauze Brush, Wire 92Gear, Magnetic 346Gear, Magnetic Friction 276Geissler Pump 437Geissler Tubes 276Generating Plate 277Generator, Current 277Generator Inductor 199Generator, Magneto-electric 362Generator, Magneto-electric, Flashing in a Dynamo or 257Generator, Motor 384Generator, Pyromagnetic. 442Generators and Motors, Commutator of Current 140Generator, Secondary 277-477Geographic Meridian 372German Mile Unit of Resistance 466German Silver 277German Standard Candle 99Gilding, Electro- 277Gilding Metal 277Gimbals 278Girder Armature 49Glass 278Globe or Globular Lightning 330Glow Discharge 187Gold 278Gold Bath 279Gold Leaf Electroscope 233Gold Stripping Bath 279Governor, Centrifugal 113Governor, Rate 449Graduator 279Gram 280Gram-atom 280Gram-molecule 280Graphite 280Gravitation 280Gravity, Acceleration of 280Gravity Ammeter 27Gravity Battery 64Gravity, Centre of 112Gravity Control 281Gravity Drop Annunciator 35Grease Spot 92Green Vitriol 562Grenet Battery 65Grid 281Grid Plug 420Grip, Cable 96Gross Efficiency 205Ground 281Grounded Circuit 123Ground Plate 417Ground Wire 281Grove's Battery 65Grove's Gas Battery 281Guard Ring 282Guard Tube 282Gun, Electro-magnetic 282Gutta Percha 282Gyration, Centre of 112Gyrostatic Action of Armatures 283 H 283H Armature 49Haarlem Magnet 337Hair, Removal of, by Electrolysis 283Haldat's Figures 284Hall Effect 284Hall Effect, Real 284Hall Effect, Spurious 284Halleyan Lines 308Hall's Experiment 284Halske's and Siemens' Battery 72Hand Hole 190Hanger Board 284Hanger, Cable 96Hanger, Cable, Tongs 97Harcourt's Pentane Standard 406Hare's Deflagrator 73Harmonic 23Harmonic Curve 174, 485Harmonic Motion, Simple 486Harmonic Receiver 284, 451Head Bath, Electric 284Head-light, Electric 285Head, Torsion 544Heat 285Heat and Fire Alarm 17Heat, Atomic 52, 285Heat, Electric 285Heat, Electric, Convection of 149, 286Heat, Irreversible. 286Heat, Mechanical Equivalent of 286Heat, Molecular 286Heat, Specific 286Heat, Specific, of Electricity 288Heat Units 288Heater, Electric 286Heating, Admiralty Rules of 12Heating Error 286Heating, Frictional 262Heating Magnet 286Heavy Carburetted Hydrogen, 397Hecto 288Hedgehog Transformer 548Heliograph 288Helix 288Henley's Universal Discharger 189Henry 288Henry's Coils 138Hermetically Sealed 289Hertz's Experiments 470Heterostatic Method 280Hexode Working 581High Bars of Commutator 289High Frequency 289High Vacuum 557Hinged Armature 45Hinged Electro-magnet 217Hissing 289Hittorf's Resistance 466Hittorf's Solution 289Hoffer's Method of Magnetization 360Hole Armature 45Hole, Hand 190Holders 289Holder, Brush 91Holder, Candle 99Holders, Carbon 107Holophote Lamp 321Holtz's Influence Machine 334Home Station 493Hood 290Horizontal Induction 302Horns 290Horns, Driving 132Horns, Following 259Horns, Leading 324Horns, Trailing 259Horse Power 290Horse Power, Actual 290Horse Power Curve 171Horse Power, Electric 290Horse Power Hour 290Horse Power, Indicated 290Horseshoe Magnet 337Hour, Ampere- 30Hour, Horse Power 290H. P. 290Hughes' Electro-magnet 291Hughes' Induction Balance 291Hughes' Sonometer 488Hughes' Telegraph 511Hughes' Theory of Magnetism 357Hughes' Type Printer 511Human Body, Resistance of 467Hydrochloric Acid Battery 66Hydro-electric 293Hydro-electric Machine 293Hydrogen 294Hydrogen, Carburetted, Heavy 397Hydrometer, Beaumé 78Hygrometer 294Hyperbolic Logarithms 389Hysteresis 295Hysteresis, Magnetic 294Hysteresis, Static 295Hysteresis, Viscous 295, 356 Idioelectrics 295Idiostatic Method 295Idle Coils 295Idle Poles 296Idle Wire 291Igniter 296I. H P. 296Illuminating Power 296Illuminating Power, Spherical 296Illuminating Power, Standard of, Viole's 561Illumination, Unit of 296Image, Electric 296Imbricated Conductor 146Immersion, Simple 185Impedance 297, 462Impedance, Impulsive 297Impedance, Oscillatory 297Impressed Electro-motive Force 297Impulse 297Impulsive Discharge 188Impulsive Impedance 297In-and-out, Soaking 486Incandescence, Electric 297Incandescent Lamp 321Incandescent Lamp Carbons, Flashing of 257Incandescent Lamp, Chamber of 113Incandescent Lamp, Life of 327Incandescent Lamp, Three Filament 322Inclination Compass 142Inclination, Magnetic 346Inclination Map 297Inclination or Dip, Angle of 33Incomplete Circuit 125Increment Key 314Independence of Currents in Parallel Circuits 297India Rubber 102Indicated Horse Power 290Indicating Bell 80, 297Indicator 298Indicator, Circuit 298Indicator, Throw-back 540Indicator, Volt 568Indifferent Electrode 210Indifferent Point 421Induced Current 163Induced Magnetization, Coefficient of 354, 359Inductance 298Inductance Balance 293Inductance Bridge 293Induction, Anti-, Conductor 36Induction, Back 55Induction Balance, Hughes 291Induction, Coefficient of Magnetic 349Induction, Coefficient of Mutual 301Induction, Coefficient of Self- 298Induction Coil 133Induction Coil, Inverted 136Induction Coil, Telephone 137, 526Induction, Cross 298Induction Current 163Induction, Electro-magnetic 218, 299Induction, Electrostatic 302Induction, Electrostatic, Coefficient of 234Induction, Horizontal 302Induction, Lateral 302Induction, Lines of 330Induction, Magnetic 302, 346Induction, Magnetic, Apparent Coefficient of 346Induction, Magnetic, Coefficient of 346Induction, Magnetic Dynamic 347Induction, Magnetic, Self- 352Induction, Magnetic Static 347Induction, Magnetic, Tube of 347Induction, Mutual, Electro-magnetic 302Induction, Mutual, Electrostatic 303Induction, Open Circuit 303Induction, Oscillatory 398Induction Protector, Mutual 481Induction, Self- 303Induction Sheath 303Induction. Unipolar 304Induction, Unit of Self- 304Induction, Vertical 304Inductive Capacity, Magnetic 346, 349Inductive Effect, Counter- 204Inductive Resistance 466Inductophone 304Inductor 305Inductor Dynamo 199Inductor Generator 199Inductor, Magneto- 363Inductor, Pacinotti's 400Inductorium 138Inertia 305Inertia, Electro-magnetic 305Inertia, Magnetic 347Infinity Plug 305, 420Influence, Electric 305Influence Machine 334Influence Machine, Armature of 46Influence Machine, Holtz 334Influence, Magnetic 346Installation 305Instantaneous Capacity 102Insulating Stool 305Insulating Tape 305Insulating Varnish 306Insulation, Electric 305Insulation, Magnetic 347Insulation, Oil 396Insulation Resistance 466Insulator 306Insulator Caps 306Insulator, Fluid 306Insulator, Line or Telegraph 306Intensity 306Intensity Armature 45Intensity Current 163Intensity, Electro-motive 228Intensity, Magnetic 348Intensity of a Magnetic Field 306Intensity of Magnetization 360Intensity, Poles of 426Inter-air Space 489Intercrossing 307Interference, Armature 45Interferric Space 489Interior Pole Dynamo 191Interlocking- Electro-magnets. 229Intermediate Metals, Law of 323Intermittent, 307Internal Characteristic 114Internal Resistance 466lnterpolar Conductor 307Interpolar Region 307Interpolation 307Interrupter, Electro-magnetic, for Tuning Fork 307Intrinsic Efficiency 205Invariable Calibration 97Inverse Induced Current 163Inverse Squares, Law of 323Inversion, Thermo-electric 533Ions 307Iron 308Ironclad Dynamo 200Ironclad Electro-magnet, 219Ironclad Magnet 356Iron Disc Ammeter, Eccentric 27Iron, Electrolytic 308Iron, Galvanized 265Ironwork Fault of a Dynamo 308Irreversible Heat 286Isochasmen Curve 171Isochronism 308Isoclinic Lines 308Isoclinic Map 308Isodynamic Lines 308Isodynamic Map 308Isoelectric Points 422Isogonal Lines 308Isogonic Map 309Isolated Distribution 309Isolated Plant 309Isolated Supply 309Isotropic 309Isthmus Method of Magnetization 360I. W. G. , 309 J 309Jablochkoff Candle 160Jack. Spring- 492Jacketed Magnet 356Jacobi's Law 309Jacobi's Method of Magnetization 360Jacobi's Unit of Current 163Jacobi's Unit of Resistance 466Jamin Candle 100Jar, Leyden 325Jar, Lightning 330Jar, Luminous 332Jars, Leyden, Charging and Discharging 108Jar, Unit 554Jewelry 309Joulad 311Joule 311Joule Effect 311Joule's Electro-magnet 337Joule's Equivalent, 311Joint, American Twist 309Joint, Britannia 309Joint, Butt 310Joint Current 160Joint, Lap 310Joint, Marriage 310Joint, Resistance 464Joints in Belts 311Joint, Sleeve 310Joint, Splayed 311Junction Box 311Junction, Thermo-electric 533 K. 311Kaolin 311Kapp. Line of Force 312Kathelectrotonus 312Kathode 312Kathodic Closure Contraction 312Kathodic Duration Contraction 312K. C. C. 312K. D. C. 312Kempe's Discharge Key 315Keeper 312Kerr Effect 235, 312Kerr's Experiment 312Key 313Key Board 313Key, Bridge 313Key, Double Contact 314Key, Double Tapper 314Key, Charge and Discharge 313Key, Increment 314Key, Kempe's Discharge 315Key, Magneto-electric 315Key, Make and Break 316Key, Plug 316Key, Reversing 316Key, Sliding-contact 316Key, Telegraph 316Kicking Coil 132Kilo 316Kilodyne 316Kilogram 317Kilojoule 317Kilometer 317Kilowatt 317Kine 317Kinnersley's Thermometer 536Kinetics, Electro- 211Kinetic Energy 241Kirchoff's Laws 317Knife Break Switch 501Knife Edge Suspension 317Knife Edge Switch 501Knife Switch 501Knot 317Kohlrausch's Law 317Kookogey's Solution 318Krizik's Cores 318 L 318Lag, Angle of 33, 318Lag, Electric 332Lag, Magnetic 348Lalande & Chaperon Battery 69Lalande-Edison Battery 69Lamellar Distribution of Magnetism 357Laminated 318Laminated Core 154Laminated Core, Tangentially 155Lamination 318Lamination of Armature Conductors 319Lamination of Magnet 361Lamp, Arc 319Lamp, Arc, Double Carbon 191Lamp Carbons, Flashing of Incandescent 257Lamp, Carcel 108Lamp, Contact 320Lamp, Differential Arc 320Lamp Globe, Waterproof 572Lamp, Holophote 321Lamp-hour 321Lamp, Incandescent 321Lamp, Incandescent, Chamber of 113Lamp, Incandescent, Three Filament 322Lamp, Life of Incandescent 327Lamp, Lighthouse 322Lamp, Monophote 321Lamp, Pilot 323Lamp, Polyphote 323Lamp, Semi-Incandescent 323Lamp-socket 323Lamps, Bank of 323Lane's Electrometer 226Langdon Davies' Rate Governor or Phonophone 450Lenz's Law 325Lap Joint 310Lap Winding 570Latent Electricity 323Lateral Discharge 188Lateral Induction 302Latitude, Magnetic 348Law, Jacobi's 309Law, Kohlrausch's 317Law, Lenz's 325Law of Angular Currents 165Law of Electrolysis 213Law of Intermediate Metals 323Law of Inverse Squares 323Law of Magnetic Attraction and Repulsion. Coulomb's 338Law of Successive Temperatures 324Law, Magnus' 367Law, Ohm's 396Law, Pflüger's. 409Law, Right Handed Screw 324Law, Sine 486Laws, Kirchoff's 317Laws of Thermo-electricity, Becquerel's 78Law, Tangent 502Law, Voltametric 567Lead 324Lead, Angle of 33Lead Chloride Battery 66Lead of Brushes 90Lead of Brushes, Negative 324Lead, Peroxide of, Battery 69Lead Sulphate Battery 66Lead Tee 504Leading Horns 324Leading-in Wires 324Leak 324Leakage 324Leakage Conductor 325Leakage, Electro-magnetic 219Leakage, Magnetic. 348Leakage, Surface 498Leclanché Agglomerate Battery 66Leclanché Battery 66Leg of Circuit 325Legal Ohm 395Legal Quadrant 444Legal Volt 568Length of Spark 490Letter Boxes, Electric 325Leyden Jar 325Leyden Jar, Armature of 46Leyden Jars, Battery of 68Leyden Jars, Charging and Discharging 108Leyden Jars, Sir William Thomson's 326Lichtenberg's Figures 327Life Curve 171Life of Incandescent Lamp 327Light, Electro-magnetic, Theory of 219Light, Maxwell's Theory of 369Lighthouse Lamp 322Lightning 327Lightning Arrester 328Lightning Arrester, Counter-electro-motive Force 329Lightning Arrester Plates 329Lightning Arrester, Vacuum 329Lightning, Ascending 330Lightning, Globe or Globular 330Lightning Jar 330Lightning, Back Stroke or Shock of 55Lime, Chloride of, Battery 61Limit, Magnetic 348Limit of Magnetization 361Linear Current 164Lineman's Detector 180Line of Commutator, Neutral 300Line of Contact 330Line of Force, Kapp 312Line of Magnet, Neutral 361Line or Telegraph Insulator 306Lines, Halleyan 308Lines, Isoclinic 308Lines, Isodynamic 308Lines, Isogonal 308Lines, Isogonic 308Lines of Force 330Lines of Force, Cutting of 175Lines of Force, Electro-magnetic 219Lines of Force, Electrostatic 234Lines of Force, Magnetic 348Lines of Induction 330Lines of Slope 330Lines or Points of Least Sparking 490Lines, Trunk 550Links, Fuse 330Liquids, Electro-dynamic Rotation of 474Liquids, Electro-magnetic Rotation of 475Liquor, Spent 491Listening Cam 330Lithanode 331Load 331Load Curve 172Load of Armature 46Local Action 331Local Battery 331Local Circuit 331Local Currents 163, 331Localization 331Locus 331Lodestone 332Logarithm 332Logarithms, Hyperbolic 389Logarithms, Napierian 389Local Battery 66Long Coil Magnet 361Long Range Electro-magnet 220Long Shunt and Series Winding 579Long Shunt Winding 579Loop 332Loop Break 332Loop, Circuit 125Loop, Drip 192Lost Amperes 30Lost Volts 571Low Vacuum 557Luces 332Luminous Jar 332Luminous Pane 401Luminous Tube 550Lux 332 M 332Machine, Cylinder Electric 333Machine, Electric, Wimshurst 577Machine, Frictional Electric 333Machine, Holtz Influence 334Machine, Hydro-electric 293Machine, Influence 334Machine, Nairne's Electrical 389Machine, Plate Electrical 417Machine, Rheostatic 472Machine, Toeppler-Holtz 334Machine, Wimshurst 335Mack 335Magic Circle 119Magne-crystallic Action 335Magnet 335Magnet, Anomalous 335Magnet, Artificial 335Magnet, Axial 336Magnet, Bar 336Magnet, Bell Shaped 336Magnet Coils, Sheath for 481Magnet, Compensating 336Magnet, Compound 336Magnet, Controlling 185, 336Magnet, Damping 336Magnet, Deflection of 337Magnet, Directing 185Magnet, Electro- 215, 337Magnet, Equator of 337Magnet, Field 337Magnet, Haarlem 337Magnet, Heating 286Magnet, Horseshoe 337Magnet, Ironclad 356Magnet, Joule's Electro- 337Magnet-keeper 361Magnet, Lamination of 361Magnet, Long Coil 361Magnet, Natural 361Magnet, Neutral Line of 361Magnet, Normal 361Magnet Operation 365Magnet, Permanent 365Magnet Pole 365Magnet, Portative Power of 366Magnet, Projecting Power of a 435Magnet, Relay 457Magnet, Simple 366Magnet, Solenoidal 366Magnet, Sucking 366Magnet, Unipolar 366Magnet Coil 336Magnet Core 336Magnet Poles, Secondary 366Magnet Pole, Unit 366Magnetic Adherence 338Magnetic and Electro-magnetic Equipotential Surface 244Magnetic Attraction 338Magnetic Attraction and Repulsion, Coulomb's Law of 338Magnetic Axis 338Magnetic Azimuth 338Magnetic Battery 338Magnetic Bridge 338Magnetic Circuit 340Magnetic Circuit, Curve of Saturation of 174Magnetic Concentration of Ores 340Magnetic Concentrator 340Magnetic Continuity 340Magnetic Conductance and Conductivity 340Magnetic Control 341Magnetic Couple 341Magnetic Creeping 341Magnetic Curves 341Magnetic Cut Out 175Magnetic Declination 342Magnetic Density 342Magnetic Dip 342, 346Magnetic Discontinuity 342Magnetic Double Circuit 340Magnetic Eye, Electro- 248Magnetic Elements 342Magnetic Elongation 344Magnetic Equator 344Magnetic False Poles 350Magnetic, Ferro- 252Magnetic Field, Intensity of a 306Magnetic Field of Force 344Magnetic Field, Uniform 345Magnetic Figures 345Magnetic Filament 345Magnetic Fluid, North 357Magnetic Fluids 345Magnetic Flux 345Magnetic Force 346Magnetic Friction 295, 346Magnetic Friction Gear 276Magnetic Fluid, South 356Magnetic Foci 259Magnetic Gear 346Magnetic Hysteresis 294Magnetic Inclination 346Magnetic Induction 302Magnetic Induction, Apparent Coefficient of 346Magnetic Induction, Coefficient of 346-349Magnetic Induction, Dynamic 347Magnetic Induction, Static 347Magnetic Induction, Tube of 347Magnetic Inductive Capacity 349Magnetic Inertia 347Magnetic Influence 346Magnetic Insulation 347Magnetic Intensity 348Magnetic Lag 348Magnetic Latitude 348Magnetic Leakage 348'Magnetic Limit 348Magnetic Lines of Force 348Magnetic Mass 349Magnetic Matter 349Magnetic Memory 349Magnetic Meridian 349Magnetic Moment 349Magnetic Needle 349Magnetic Needle, Declination of the 178Magnetic Needle, Dip of 185Magnetic Needle, Oscillation of a 397Magnetic Output 399Magnetic Parallels 349Magnetic Permeability 349Magnetic Perturbations 350Magnetic Poles 350Magnetic Potential 350, 431Magnetic Proof Piece 350Magnetic Proof Plane 350Magnetic Quantity 350Magnetic Reluctance 351, 458Magnetic Reluctivity 351Magnetic Remanence 358Magnetic Repulsion 338Magnetic Resistance 458Magnetic Retentivity 351Magnetic Rotatory Polarization 351Magnetic Saturation 251Magnetic Screen 351Magnetic Self-induction 352Magnetic Separator 352Magnetic Shell 352Magnetic Shell, Strength of 352Magnetic Shield 353Magnetic Shunt 353Magnetic Storms 353Magnetic Strain 354Magnetic Stress 354Magnetic Susceptibility 254, 359Magnetic Tick 354Magnetic Top 542Magnetic Twist 354Magnetic Vane Ammeter 27Magnetic Variations 354Magnetism, Ampere's Theory of 354Magnetism, Blue 355Magnetism, Components of Earth's 356Magnetism, Creeping of 356Magnetism, Decay of 356Magnetism, Discharge of 356Magnetism, Electro 220Magnetism, Ewing's Theory of 356Magnetism, Free 356Magnetism, Hughes' Theory of 357Magnetism, Lamellar Distribution of 357Magnetism of Gases 357Magnetism, Red 357Magnetism, Residual 358Magnetism, Solenoidal Distribution of 358Magnetism, Sub-permanent 358Magnetism, Terrestrial 358Magnetism, Weber's Theory of 358Magnetization by the Earth 359Magnetization by Double Touch 358Magnetization by Separate Touch 359Magnetization by Single Touch 359Magnetization, Coefficient of Induced 359Magnetization Curve 172Magnetization, Cycle of 360Magnetization, Elias' Method of 360Magnetization, Hoffer's Method of 360Magnetization, Intensity of 360Magnetization, Isthmus Method of 360Magnetization, Jacobi's Method 360Magnetization, Limit of 361Magnetization, Maximum 361Magnetization, Specific 361Magnetization, Surface 356Magnetizing Coil 127Magneto 361Magneto Bell 80Magneto Call Bell 361Magneto-electric 361Magneto-electric Brake 362Magneto-electric Generator 362Magneto-electric Generator, or Dynamo, Flashing in a 257Magneto-electric Key 315Magneto-electric Telegraph 512Magnetograph 363Magneto-inductor 363Magnetometer 363Magnetometer, Differential 365Magnetometry 364Magneto-motive Force 365Magnetophone 367Magnetoscope 365Magnifying Spring Ammeter 28Magnus' Law 367Main Battery 66Main Battery Circuit 125Main Circuit 125Main or Standard Feeder 251Mains, Electric 367Make 367Make and Break Current 164, 367Make and Break Key 316Make-induced Current 163Malapterurus 367Map, Declination 309Map, Inclination 297Map, Isoclinic 308Map, Isodynamic 308Map, Isogonic 309Marié Davy's Battery 67Marine Galvanometer 269Mariner's Compass 142Marked End or Pole 368Marriage Joint 310Mass, Electric 368Mass, Magnetic 349Master Clock 127Mathematical Element 237Matteueci's Experiment 369Matter, Electric 368Matter, Fourth State of 261Matter, Magnetic 349Matter, Radiant 368Matter, Ultra Gaseous 551Matthiessen's Meter-gram Standard Resistance, . 466Matthiessen's Unit of Resistance 466Matting, Electric Floor 369Maximum Magnetization 361Maxwell's Theory of Light 369Mayer's Floating Magnet 370Maynooth's Battery 67Measurement, Absolute 8Measurements 370Mechanical Equivalent of Heat 286Mechanical Energy 241Mechanical Equivalent, Electro- 244Medical Battery 67Medium, Polarization of the 424Meg or Mega 370Meidinger's Battery 68Memoria Technica, Ampére's 30Memory, Magnetic 349Mercury 371Mercury Bichromate, Battery 63Mercury Circuit Breaker 121Mercury Cups 371Mercury, Sulphate of, Battery 67Mercurial Air Pump 16Meridian, Astronomical 372Meridian, Geographic 372Meridian, Magnetic. 349Merit, Figure of 256Merit, Formula of 256Metal, Gilding 277Metallic Arc 39Metallic Circuit 125Metallochromes 392Metallurgy, Electro- 222Metals, Law of Intermediate 323Meter. Alternating Current 373Meter, Ampere and Volt, Galvanometer . 274Meter, Balance Ampere 391Meter Bridge 373Meter Bridge, Slide 486Meter Candle 374Meter, Chemical Electric 375Meter, Current 375Meter, Electro-magnetic 375Meter, Energy 375Meter Gram Standard Resistance, Matthiesen's 466Meter-millimeter 375Meter-millimeter Unit of Resistance 466Meter, Neutral Wire Ampere. 391Meter, Quantity 445Meters. Ampere 39Meter, Thermal-Electric 375Meter, Time Electric 375Meter, Watt 375Method, Broadside 89Method, Deflection 178Method, End on 238Method, Idiostatic 295Method, Multiple Wire 388Method, Null 393Method of Magnetization, Elias' 360Method of Magnetization, Isthmus 360Method of Magnetization, Jacobi's 360Methven Standard or Screen 376Mho, 376Mica 376Mica, Moulded 376Micro 376Micrometer 376Micrometer, Arc 39, 376Micrometer, Spark 470Micron 376Microphone 376Microphone Relay 377, 457Microscope. Photo-electric 410Microtasimeter 377Mil 379Mil, Circular 379Mil-foot 379Mil-foot Unit of Resistance 467Milli 379Milligram 379Millimeter 379Milli-oerstedt 380Mil, Square 379Minute, Ampere- 30Mirror Galvanometer. 271Mixed Gases 275mm. 380Molar 380Molar Energy 241Molecular Affinity 380Molecular Attraction 380Molecular Bombardment 380Molecular Chain 380Molecular Energy 241Molecular Heat 286Molecular Rigidity 380, 473Molecular Shadow 480Molecule 380Moment 381Moment, Magnetic 349Moment of Couple 544Moment, Turning 544Monophote Lamp 321Mordey Effect 381Morse Receiver 381Morse Recorder 451Morse Telegraph 512Mortar, Electric 382Motion, Currents of 167Motograph, Electro- 229Motor. Compound or Compound Wound, . 382Motor, Differential 382Motor, Dynamo 200Motor, Electric 382Motor, Electro- 229Motor, Electro-motive Force 384Motor-generator 384Motor, Multiphase 384Motor, Overtype 399Motor, Prime 385Motor, Pulsating 386Motor, Pyromagnetic 442Motor, Reciprocating 385Motor, Series 386Motor, Shunt 386Moulded Mica 376Moulding 58Movable Secondary 477Mud, Battery 68Multiphase Currents 166Multiphase Motor 384Multiple 386Multiple Arc 387Multiple Arc Box 387Multiple Connected Battery 68Multiple-series 387, 480Multiple Switch 501Multiple Switch Board 387Multiple Transformer 548Multiple Winding 579Multiple Wire Method 388Multiplex Harmonic Telegraph 510Multiplex Telegraph 514Multiplex Telegraphy 388Multiplier, Schweigger's 476Multiplying Power 347, 349Multiplying Power of a Shunt 388Multipolar Armature 46Multipolar Dynamo 200Multipolar Electric Bath 57Multipolar Winding 579Muscular Pile 388Mutual Electro-magnetic Induction 302Mutual Electrostatic Induction 303Mutual Induction, Coefficient of 301Mutual Induction Protector 481Myria 388 Nairne's Electrical Machine 389Napierian Logarithms 389Nascent State 389Natural Currents 166, 389Natural Magnet 361Needle 389Needle Annunciator 35Needle, Astatic 50Needle, Dipping 185Needle, Magnetic 349Needle, Orientation of a Magnetic 397Needle of Oscillation 389Needle Telegraph, Single 519Needle, Telegraphic 389Negative Charge 389Negative Current 164Negative Electricity 389Negative, Electro- 229Negative Element 390Negative Feeder 251Negative Lead of Brushes 324Negative Plate 417Negative Pole 425Negative Potential 432Negative Side of Circuit 125Nerve and Muscle Current 164Nerve Currents 390Net Efficiency 205Net, Faraday's 250Network 390Neutral Armature 46Neutral Feeder 251Neutral Line of Commutator 390Neutral Line of Magnet 361Neutral Point 421Neutral Point of Commutator 390Neutral Point, Thermo-electric 390Neutral Relay Armature 46, 390Neutral Temperature 390Neutral Wire 390Neutral Wire Ampere Meter 391N. H. P. 391Niaudet's Battery 61Nickel 391Nickel Bath 391Night Bell 392Nitric Acid Battery 68Nobili's Rings 392Nodal Point 422Nodular Deposit 392Nominal Candle Power 101Non-conductor 392Non-essential Resistance 465-467Non-inductive Resistance 467Non-polar Dynamo 200Non-polarizable Electrodes 210Non-Polarized Armature 46Normal Magnet 361North Magnetic Fluid 357North Pole 392North Seeking Pole 393Null Method 393Null Point 422 Occlusion 393Oerstedt 394Oerstedt's Discovery 394Oerstedt, Milli- 380Ohm 394Ohmage 394Ohm, B. A. 394Ohm, Board of Trade 394Ohm, Congress 395Ohmic Resistance 394, 467Ohm, Legal 395Ohmmeter 395Ohm, Rayleigh 396Ohm's Law 396Ohm, True 396Oil Insulation 396Oil Transformer 548Old Armature, Siemens' 49Olefiant Gas 397Omnibus Bar 94Omnibus Rod 94Omnibus Wire 94One Coil Electro-magnet 219Open 397Open Circuit 125Open Circuit Battery 68Open Circuit Induction 303Open Circuit Oscillation 397Open Coil Armature 46Open Coil Dynamo 200Opening Shock 482Operation, Magnet 365Opposed Current 164Optics, Electro- 229Orders of Currents 167Ordinate 397Ordinates, Axis of 54, 397Ores, Electric Reduction of 453Ores, Magnetic Concentration of 340Organ, Electric 397Orientation of a Magnetic Needle 397Origin of Co-ordinates 397Oscillation, Centre of 112Oscillation, Electric 398Oscillation, Needle of 389Oscillation, Open Circuit 397Oscillatory 23Oscillatory Discharge 188Oscillatory Displacement 398Oscillatory Electro-motive Force 398Oscillatory Impedance 297Oscillatory Induction 398Osmose, Electric 398Outlet 399Output 399Output, Magnetic 399Output, Unit of 399Over-compounding 399Over, Flashing 258Overflow Alarm 18Over-house Telegraph 515Overload 399Overtype Dynamo or Motor 399Oxide of Copper Battery 68Ozone 399 Pacinotti's Inductor 400Pacinotti's Ring 400Pacinotti Teeth 400Page Effect 401Page's Revolving Armature 47Paillard Alloys 400Palladium 401Pane, Fulminating 262Pane, Luminous 401Pantelegraphy 402, 510Paper Filaments 402Parabola 402Parabolic Reflector 402Paraffine 402Paraffine Wax 402Paragrêles 403Parallax 403Parallel 403Parallel Circuits 123-126Parallelogram of Forces 260Parallels, Magnetic 349Paramagnetic 403Paramagnetism 404Parasitical Currents 163Parchmentizing 404Partial Current 164Partial Earth 203, 404Partial Vacuum 557Passive State 404Path, Alternative 24P. D. 404Peltier's Cross 405Peltier Effect 404Pen, Electric 405Pendant Cord 405Pendulum Circuit Breaker 121Pendulum, Electric 405Pendulum or Swinging Annunciator 35Pentane Standard, Harcourt's 406Pentode Working 581Percussion, Centre of 112Perforated Armature 45Perforated Core Discs 154Perforator 407Period 407Period, Vibration 560Periodic 23Periodic Current, Power of 433Periodicity 262, 408Peripolar Zone 582Permanency 408Permanent Magnet 365Permanent Magnet Ammeter 28Permanent State 408Permeability 346-349Permeability-temperature Curve, 174Permeameter 408Permeance 408Peroxide of Lead Battery 69Perturbations, Magnetic 350Pflüger's Law 409Phantom Wires 409Phase 409Phase, Retardation of 471Phenomenon, Porret's 427Pherope 409, 527Philosopher's Egg 409Phonautograph, 409Phone 409Phonic Wheel 409Phonograph 410Phonophone or Rate Governor, Langdon Davies' 450Phonozenograph 410Phosphorescence 410Phosphorous, Electrical Reduction of 410Photo-electric Microscope 410Photo-electricity 410Photo-electro-motive Force 410Photometer 411Photometer, Actinic 411Photometer, Bar 411Photometer, Bunsen's 412Photometer, Calorimetric 412Photometer, Dispersion 412Photometer, Shadow 414Photometer, Translucent Disc 412Photophore 415Photo-voltaic Effect 415Physical Energy 241Physiology, Electro- 231Piano, Electric 415Pickle 415Picture, Electric 415Piece, Bed 78Piece, Magnetic Proof 350Piece, Pole 423Pierced Core-discs, 152Pile 415Pile, Differential Thermo-electric 533Pile, Muscular 388Pile or Battery, Thermo-electric 530Pilot Brush 91Pilot Lamp 323Pilot Transformer 415Pilot Wires 415Pistol, Electric 416Pith 416Pith Ball Electroscope 234Pith-balls 416Pivoted Armature 47Pivot Suspension 416Plane, Magnetic Proof 350Plant 417Plant Electricity 417Plant, Isolated 309Planté's Secondary Battery, 72Plate, Arrester 417Plate Condenser 417Plate, Earth 203Plate Electrical Machine 417Plate, Franklin's 262Plate, Generating 277Plate, Ground 417Plate, Negative 417Plate, Positive 277, 417Plating Balance 417Plating Bath 418Plating, Electro- 418Platinized Carbon Battery 69Platinoid 418Platinum 419Platinum Alloy 419Platinum Black 419Platinum Silver Alloy 419Platinum Sponge 419Play, End 238Plow 420Plücker Tubes 420Plug 420Plug Cut Out 175Plug, Double 191Plug, Grid 420Plug, Infinity 305, 420Plug Key 316Plug Switch 420Plumbago 421Plunge Battery 69Plunge 421Plunger and Coil 131Plunger and Coil, Differential 132Plunger, Coil and 131Plunger Electro-magnet 220Pneumatic Battery 69Pneumatic Signals, Electro- 231P. O. 421Pockets, Armature 47Poggendorf's Solution 421Point, Contact 147Point, Indifferent 421Point, Neutral 421Point. Nodal 422Point, Null 422Point of Commutator, Neutral 390Point Poles 422Points, Consequent 422Points, Corresponding 422Points, Iso-electric 422Points of Derivation 180, 423Point, Thermo-electric Neutral 390Polar Angle 423Polar Extension 423Polarity, Diamagnetic 181, 423Polarity, Resultant 470Polarization 423Polarization, Back Electro-motive force of 156Polarization Capacity 424Polarization, Dielectric 183Polarization, Galvanic 265Polarization, Magnetic Rotary 351Polarization of the Medium 424Polarized Armature 47Polarized Electro-magnet 220Polarized Relay 458Polarized Relay, Tongue of 542Polarizing Current 164Polar Region 424Polar Span 424Polar Span, Angle of 32, 423Polar Tips 423Polar Zone 582Pole, Analogous 31, 425Pole, Antilogous 425Pole, Armature 47Pole, Austral 54Pole, Boreal 85Pole Brackets, Telegraph 515Pole Changer 425Pole Changing Switch, 501Pole Dynamo, Interior 199Pole, Magnet 366Pole, Negative 425Pole, North 392Pole, North-seeking 393Pole or End, Marked 368Pole Piece 423Pole Pieces 425Pole, Positive 425Pole, Salient 426Pole, Terminal 529Pole Tips 290, 426Pole, Traveling 426Pole, Unit Magnet 366Poles 425Poles, Compensating 426Poles, Consequent 146Poles, Idle 296Poles, Magnetic 350Poles, Magnetic, False 350Poles of Intensity 426Poles of Verticity 426, 560Poles, Point 422Poles, Secondary 478Poles, Secondary Magnet 366Polyphase Currents 167Polyphote Lamp 323Popgun, Electric 282Porous Cell 427Porous Cup 159, 426Porret's Phenomenon 427Portative Power of Magnet 366Portelectric Railroad 427Portrait, Electric 415Position, Energy of 241Position Finder 427Position, Sighted 484Positive Current 164Positive Direction 428Positive Electricity 428Positive Element 277Positive Feeder 251Positive Plate 277, 417Positive Pole 425Positive Potential 432Positive Side of Circuit 125Post Office 428Posts, Binding, or Screws 81Potential 428Potential, Absolute 428Potential, Constant 429Potential Difference, Contact 147Potential Difference, Electric 429Potential Difference, Electro-motive 429Potential, Electric Absolute 429Potential, Fall of 430Potential Galvanometer 269Potential in Armature, Curve of Distribution of 172Potential, Magnetic 350, 431Potential, Negative 432Potential or Static Energy 241Potential, Positive 432Potential Regulation, Constant 455Potential, Unit of Electric 432Potential, Zero 432, 582Potentiometer 432Poundal 433Pound-foot 259Power 438Power, Candle 100Power, Directive 187Power, Electric 433Power, Horse 290Power, Illuminating 296Power, Multiplying 349Power of Magnet, Portative 366Power of Periodic Current 433Powers of Ten 527Power, Stray 495Power, Thermo-electric 533Press Button 94Pressel 434Pressure 434Pressure, Electric 434Pressure, Electrification by 434Primary 434Primary Ampere-turns 31, 551Primary Battery 69, 434Prime 434Prime Conductor 146, 434Prime Conductor, Coatings of a 129Prime Motor 385Principle, Gauss' 276Printing Telegraph 515Probe, Electric 435Projecting Power of a Magnet 435Prony Brake 435Proof Piece, Magnetic 350Proof-plane 436Proof Plane, Magnetic 350Proof-sphere 436Proportional Galvanometer 269Proportionate Arms 436Prostration, Electric 437Protector, Body 84Protector, Comb 437Protector, Electric 437Pull 437Pulsatory Current 164Pulsatory Field 256Pulsating Motor 386Pulvermacher's Electro-medical Battery 69Pump, Geissler 437Pump, Sprengel 439Pump, Swinburne 440Pumping 439Puncture-electro 232Puncture-galvano 232Push Button 93. 98, 440Push, Desk 180Push, Floor 258Pyro-electricity 441Pyromagnetic Generator 442Pyromagnetic Motor 441Pyromagnetism 443Pyrometer, Siemens' Electric 443 Q 443Quad 288, 443Quadrant 288, 443Quadrantal Deviation 180Quadrant, Legal 444Quadrant, Standard 444Quadrature 444Quadruplex Telegraph 515Qualitative 444Quality of Sound 444Quantitative 444Quantity 444Quantity Armature 47Quantity, Electric 444Quantity, Electro-magnetic 445Quantity, Electro-magnetic, Practical Unit of 445Quantity, Electrostatic 445Quantity Galvanometer 269Quantity, Magnetic 350Quantity Meter 445Quartz 445Quicking 446 R 446Racing of Motors 446Radial Armature 47Radian 446Radiant Energy 446Radiant Matter 368Radiation 446Radicals 446Radiometer 447Radiometer, Electric 447Radio-micrometer 447Radiophony 447Railroad, Portelectric 427Range Finder 447Rate Governor 449Rate Governor or Phonophone, Langdon Davies' 450Rated Candle Power 101Ratio Arms 437Ratio, Core 154Ratio, Shunt 483Ratio, Velocity 560Ray, Electric 450Rayleigh Ohm 396Reaction Coil 132Reaction of a Dynamo Field and Armature 450Reaction of Degeneration 179Reactions, Anodic 36Reactions, Armature 47Reaction Telephone 527Reaction Wheel 259Reading Galvanometer, Direct 269Reading, Sound 489Reading Telescope 450Real Efficiency of Secondary Battery 205Real Hall Effect 284Réaumur Scale 450Recalescence 451Receiver 451Receiver, Harmonic 284, 451Receiver, Morse 381Receptive, Electro- 232Recharge 115Reciprocal 451Reciprocating Motor 385Recoil Circuit 125Recorder, Chemical 117Recorder, Morse 451Recorder, Siphon 452Record, Telephone 451Rectification of Alcohol, Electric 18Rectified Current 164Rectilinear Current 165Red Varnish 559Red Magnetism 357Redressed Current 165Reduced Resistance 467Reducteur for Ammeter 453Reducteur for Voltmeter 453Reduction of Ores, Electric 453Reduction of Phosphorous, Electrical 410Reflecting Galvanometer 270Reflector, Parabolic 402Refraction, Electric Double 454Refraction, Electrostatic 235Refreshing Action 454Region, Extra-polar 454Region, Intrapolar 307Region, Polar 424Register, Electric 454Register, Telegraphic 454Regulation, Constant Current 454Regulation, Constant Potential 455Regulation of Alternating Current Dynamo 195Regulation of Dynamos 455Reguline 456Relative 456Relative Calibration 98Relay 456Relay Bell 80Relay Bells 457Relay, Box Sounding 457Relay Connection 457Relay, Differential 457Relay Magnet 457Relay, Microphone 377, 457Relay, Neutral, Armature 390Relay, Polarized 457Reluctance 458Reluctance, Magnetic 351, 458Reluctance, Unit of 438Reluctivity 459Reluctivity, Magnetic 351Remanence 459Remanence, Magnetic 358Removal of Hair by Electrolysis 283Renovate 115Repeater 459Repeater, Telegraph 518Replenisher, Sir Wm. Thomson's 459Repulsion, Magnetic 338Repulsion and Attraction, Electrostatic 234Repulsion and Attraction, Electro-magnetic 217Reservoir, Common 460Residual Atmosphere 460Residual Capacity 103Residual Charge 116Residual Magnetism 358Residue, Electric 116, 460Resin 460Resinous Electricity 461Resistance 461Resistance, Apparent 297, 462Resistance, Assymmetrical 462Resistance Box 462Resistance, B. A. Unit of 462Resistance Box, Sliding 463Resistance, Breguet Unit of 463Resistance Bridge 577Resistance Coil 137Resistance Coil, Standard 464Resistance, Carbon 463Resistance, Combined 464Resistance, Compensating 144Resistance, Critical 464Resistance, Dielectric 183, 464Resistance, Digney Unit of 464Resistance, Electrolytic 464Resistance, English Absolute or Foot-second Unit of 465Resistance, Equivalent 465Resistance, Essential 465Resistance, External 465Resistance Frame 465Resistance, German Mile Unit of 466Resistance, Hittorf's 466Resistance, Inductive 466Resistance, Insulation 466Resistance, Internal 466Resistance, Jacobi's Unit of 466Resistance, Joint 464Resistance, Magnetic 351, 458Resistance, Matthiessen's Meter-gram Standard of 466Resistance, Matthiessen's Unit of 466Resistance, Meter-millimeter Unit of 466Resistance, Mil-foot Unit of 467Resistance, Non-essential 465, 467Resistance, Non-inductive 467Resistance of Human Body 467Resistance, Ohmic 394, 467Resistance, Reduced 467Resistance, Siemens' Unit of 467Resistance, Specific 467Resistance. Specific Conduction 467Resistance, Spurious 467Resistance, Steadying 468Resistance, Swiss Unit of 468Resistance, Thomson's Unit of 468Resistance to Sparking 490Resistance, True 467Resistance, Unit 468Resistance, Unit of, B. A. 78Resistance, Varley's 559Resistance, Varley's Unit of 468Resistance, Virtual 297Resistance, Weber's Absolute Unit 468Resolution of Forces 261Resonator, Electric 468-470Rest, Currents of 167Resultant 470Resultant Polarity 470Retardation 470Retardation of Phase 471Retentivity 471Retentivity, Magnetic 351Retort Carbon 471Return 471Return Circuit 125Return, Earth 203Return Stroke 55Reversal, Thermo-Electric 533Reverse Current Working 581Reverse-induced Current 163Reverser, Current 165Reversibility 471Reversible Bridge 472Reversing Key 316Reversing Switch 501Revivify 115Revolving Armature, Page's 47Rheochord 472Rheometer 472Rheomotor 472Rheophore 472Rheoscope 472Rheoscopic Frog 262Rheostat 472Rheostat Arm 472Rheostatic Machine 472Rheostat, Wheatstone's 472Rheotome 473Rheotrope 473Rhigolene 473Rhumbs 473Rhumkorff Coil 138, 473Ribbon Coil 138Ribbon Core 154Right-handed Screw Law 324Rigidity, Molecular 380, 473Ring, Ampere 30Ring Armature 48Ring. Collecting 139Ring Contact 473Ring Core 155Ring, Dynamo 200Ring, Faraday's 473Ring, Foundation 261Ring, Guard 282Ring, Pacinotti's 400Rings, Electric 392Rings, Nobili's 392Ring, Split, Commutator 141Roaring 474Rocker 474Rocker Arms 50, 474Rod, Bus 94Rod, Discharging 189Rod, Omnibus 94Roget's Spiral 474Rolling Armature 49Rosin 460Rotary Polarization, Magnetic 351Rotating Brush 91Rotating Field 256Rotation of Liquids, Electro-dynamic 474Rotation of Liquids, Electro-magnetic 475Rotatory Currents 167Rubber 102, 475Rubber, India 102 Saddle Bracket 475Safety Catch 175Safety Cut Out 175Safety Device 475Safety Fuse 175, 475Safety Fuse, Plug, or Strip 475Sal Ammoniac Battery 69Salient Pole 426Salt 475Salt, Dronier's 192Salt or Sea-salt Battery 69Sand Battery 90Saturated 476Saturation, Magnetic 351Saw, Electric 476Scale, Fahrenheit 248Scale, Réaumur 450Scale, Tangent 502Schweigger's Multiplier 476Scratch Brushes 476Screen, Electric 476Screen, Magnetic 351Screen, Methven 376Screws or Posts, Binding 81Sealed, Hermetically 289Sea Salt or Salt Battery 69Secohm 288Second, Ampere- 30Secondary Actions 477Secondary Ampere-turns 31, 551Secondary Battery 70Secondary Battery, Efficiency of, Quantity 205Secondary Battery, Planté's 72Secondary Clock 127Secondary Current 166Secondary Generator 277, 477Secondary Magnet Poles 366Secondary, Movable 477Secondary Plates, Colors of 478Secondary Poles 478Secretion Current 166Section Trolley 549Sectioned Coils 138Seebeck Effect 478Segments 56Segments, Commutator 56Selenium 478Selenium Cell 478Selenium Eye 478Self-exciting Dynamo 201Self-induction 303Self-induction, Magnetic 352Self-induction, Unit of 304Self-repulsion 478Self-winding Electric Clock 128Semi-circular Deviation 181Semi-conductors 478Semi-incandescent Lamp 323Sender, Zinc 582Sensibility 479Sensitiveness, Angle of Maximum 479Separate Circuit Dynamo 201Separate Touch 359, 479Separate Touch, Magnetization by 359Separately Excited Dynamo 201, 479Separation of Electricities 479Separator 479Separator, Magnetic 352Series 479Series and Long Shunt Winding 579Series and Separate Coil Winding 579Series and Short Shunt Winding 580Series, Contact 147Series Dynamo 201Series, Electro-chemical 209Series, Electro motive 228Series, Electrostatic 235Series Motor 386Series, Multiple- 387Series-multiple 480Series, Thermo-electric 534Series Transformer 548Series Winding 579Service Conductors 480Serving 480Shackle 480Shadow, Electric 480Shadow, Molecular 480Shadow Photometer 414Sheath for Magnet Coils 481Sheath for Transformers 481Sheath, Induction 303Sheet Current 166Shell, Magnetic 352Shell, Strength of Magnetic 352Shellac 481Shellac Varnish 481Shield, Anti-magnetic 37Shield, Magnetic 351, 353Shielded 481S. H. M. 482Shock, Back, or Stroke of Lightning 55Shock, Break 482Shock, Electric 482Shock, Opening 482Shock, Static 482Short Circuit 482Short Circuit Working 482Short Fall Air Pumps 16Short Shunt Winding 579Shovel Electrodes 483Shower Bath, Electric 57Shunt 483Shunt Box 483Shunt Circuit 123, 126Shunt Dynamo 202Shunt, Electro-magnetic 483Shunt, Galvanometer 271, 483Shunt, Magnetic 353Shunt Motor 386Shunt. Multiplying Power of a 388Shunt Ratio 483Shunt Winding 580Shuttle Armature 49Shuttle Current 483Shuttle Winding 483, 580Side Flash 484Siemens and Halske's Battery 72Siemens' Differential Voltameter 564Siemens' Electro-dynamometer 212Siemens' Old Armature 49Siemens' Unit of Resistance 467Sighted Position 484Signaling, Velocity of 560Signals, Electro-pneumatic 231Signal, Telegraph 519Silent Discharge 187, 189, 206Silver 484Silver Bath 484Silver, German 277Silver Stripping Bath 484Silver Voltameter 565Simple Arc 39Simple Circuit 126Simple Harmonic Motion 486Simple Immersion 185Simple Magnet 366Simple Substitution 485Sims-Edison Torpedo 543Sine Curve 174, 485Sine Galvanometer 271Sine Law 486Sines, Curve of 173, 485Single Coil Dynamo 202Single Curb Working 581Single Fluid Theory 486Single Fluid Voltaic Cell 486Single Needle Telegraph 519Single Touch, Magnetization by 359Sinistrotorsal 486Sinuous Current 166Sinusoidal Curve 174, 485Siphon Recorder 452Sir William Thomson's Battery 72Skin Effect 486Skrivanow Battery 72Sled 486Sleeve, Joint 310Slide, Balance 374Slide Bridge 374Slide Meter Bridge 486Sliding Condenser 144Sliding-contact Key 316Sliding Resistance Box 463Slope, Lines of 330Smee's Battery 73S. N. Code 486Snap Switch 501Soaking-in-and-out 486Socket, Lamp 323Socket, Wall 572Soldering, Electric 487Solenoid 487Solenoid Ammeter 28Solenoidal Distribution of Magnetism 358Solenoidal Magnet 366Solid Earth 203Solutions, Battery, Chromic Acid 73Solution, Chutaux's 119Solution, Delaurier's 179Solution, Hittorf's 289Solution, Kookogey's 318Solution, Poggendorf's 421Solution, Striking 496Solution, Tissandier's 542Solution, Trouvé's 549Sonometer, Hughes' 488Sonorescence 488Sound, Characteristics of 114Sounder 488Sounders, Tin 542Sound, Quality of 444Sound Reading 489South Magnetic Fluid 356Space, Clearance 489Space, Crookes' Dark 489Space, Dark, Faraday's 249, 489Space, Faraday's Dark 249, 489Space, Inter-air 489Space, Interferric 489Span, Polar 424Span, Polar, Angle of the 32Spark Arrester 489Spark Coil 489Spark Discharge 189Spark, Duration of Electric 490Spark Gap 490Spark, Length of 490Spark Micrometer 470Spark Tube 491Sparking 490Sparking Distance 190Sparking, Lines or Points of Least 490Sparking, Resistance to 490Specific Conduction Resistance 467Specific Conductivity 145Specific Heat 286Specific Heat of Electricity 491Specific Inductive Capacity 103Specific Magnetization 361Specific Resistance 467Speech, Articulate 50Speed, Critical 157Spent Acid 491Spent Liquor 491Spherical Armature 49Spherical Candle Power 101Spherical Illuminating Power 296Sphygmophone 491Sphygmophone, Electric 491Spiders 491Spiral 492Spiral Battery 73Spiral, Roget's 474Spiral Winding 492Spirit Compass 143Splayed Joint 311Splice Box 492Split Battery 73Split Ring Commutator 141Spluttering 492Sponge, Platinum 419Spot, Grease 92Sprengel Pump 439Spring Ammeter 28Spring and Fibre Suspension 252Spring-contact 148Spring Control 492Spring Jack Cut-out 493Spurious Hall Effect 284Spurious Resistance 467Spurious Voltage 493Square Mil 379Square Wire 493Squares, Law of Inverse 323St. Elmo's Fire 494Staggering 493Standard Candle 101Standard Candle, German 99Standard, Harcourt's Pentane 406Standard, Methven 376Standard of Illuminating Power, Viole's 561Standard or Main Feeder 251Standard Quadrant 444Standard Resistance Coil 464Standard Voltaic Cell 109Standard Voltaic Cell, Daniell's 109Standard Voltaic Cell, Latimer Clark's. 110State, Electrotonic 493State, Nascent 389State of Matter, Fourth 261State, Passive 404State, Permanent 408Static Breeze 493Static Condenser, Armature of 46Static Electricity 493Static Hysteresis 295Static Induction, Magnetic 347Static Shock 482Station, Central 493Station, Distant 493Station, Home 493Station, Transforming 494Steadying Resistance 468Steel 494Steeling 494Steel Yard Ammeter 28Step-by-step Telegraph 506Step-by-step Telegraphy 494Step-down 494Step, Foot- 259Sticking 494Stool, Insulating 305Stopped Coil Electro-magnets 221Stopping Off 495Storage Battery 70Storage Battery Changing Switch 501Storage Battery, Planté's 72Storage Capacity 105, 495Storage of Electricity 495Storms, Electric 495Storms. Magnetic 353Strain 495Strain, Dielectric 183Strain, Magnetic 354Stranded Conductor Armature 49Stranded Core 155Stray Field 256, 495Stray Power 495Streamlets. Current 495Strength, Dielectric 183Strength of Magnetic Shell 352Stress 495Stress, Dielectric 496Stress, Electro-magnetic 219, 496Stress, Electrostatic 236, 496Stress, Energy of 241Stress, Magnetic 354Striae, Electric 496Striking Distance 496Striking Solution 496Stripping 496Stripping Bath 57Stripping Bath, Gold 279Stripping Bath, Silver 484Stroke, Back 55Stroke or Shock of Lightning, Back 55Stroke, Return 55Sub-branch 496Sub-main 496Sub-permanent Magnetism 358Substitution, Simple 485Subway, Electric 496Successive Temperatures, Law of 324Sucking Coil 182Sucking Magnet 366Sulphate of Lead Battery 66Sulphate of Mercury Battery 67Sulphating 497Sulphur Dioxide 497Sulphuric Acid 497Sulphuric Acid Voltameter 564Sulphurous Acid Gas 497Sunstroke, Electric 497Superficial Density, Electric 180Supersaturated, 497Supply, Isolated 309Surface 497Surface Density 498Surface, Equipotential 498Surface Leakage 498Surface Magnetization 356Surgical Electro-magnet 222Surging Discharge 188Surveyors' Compass 143Susceptibility, Magnetic 354, 359Suspension 498Suspension, Bifilar 498Suspension, Fibre 252Suspension, Knife Edge 317Suspension, Pivot 416Suspension, Spring and Fibre 252Suspension, Torsion 545Suspension Wire of Cable 97Swaging. Electric 499Swelling Current 167S. W. G. 499Swinburne Pump 440Swinging Earth 203Swinging or Pendulum Annunciator 35Swiss Unit of Resistance 468Switch 499Switch, Automatic 500Switch Board 500Switch Board, Multiple 387Switch Board, Trunking 550Switch, Break-down 88Switch, Changing 500Switch, Changing Over 500Switch, Circuit Changing 500Switch, Double Break 500Switch, Double Pole 500Switch Feeder 500Switch, Knife 501Switch, Knife Break 501Switch, Knife Edge 501Switch, Multiple 501Switch, Plug 420Switch, Pole Changing 501Switch, Reversing 501Switch, Snap 501Switch, Storage Battery Changing 501Switch, Three Way 501Switches, Distributing 190Symmer's Theory 191Sympathetic Vibration 501, 561System, Block 83System of Co-ordinates 150System, Tower 545 T 501Tailing Current 501Tailings 501Talk, Cross 158Tamidine 502Tangent Galvanometer 272Tangent Law 502Tangent Positions of, Gauss 276Tangent Scale 502Tangentially Laminated Core 155Tank, Cable 97Tape, Insulating 305Tapper Key, Double 314Teazer 504Technica, Memoria, Ampére's 30Tee, Lead 504Teeth, Pacinotti 400Tel-autograph 504Tele-barometer, Electric 504Telegraph, A. B. C. 504Telegraph, Autographic 510Telegraph, Automatic 504Telegraph, Dial 505Telegraph, Double Needle 506Telegraph, Duplex 506Telegraph, Duplex, Bridge 506Telegraph, Duplex, Differential 507Telegraph Embosser 237Telegraph, Facsimile 510Telegraph, Harmonic Multiplex 510Telegraph. Hughes' 511Telegraph Insulator 306Telegraph Key 316Telegraph, Magneto-electric 512Telegraph, Morse 512Telegraph, Multiplex 514Telegraph, Single Needle 519Telegraph, Overhouse 515Telegraph Pole Brackets 515Telegraph, Printing 515Telegraph, Quadruplex 515Telegraph Repeater 518Telegraph Signal 519Telegraph, Step-by-step 506Telegraph, Wheatstone's, A. B. C. 521Telegraph. Writing 521Telegraphic Alphabet 19Telegraphic Code 130, 511Telegraphic Needle 389Telegraphic Register 454Telegraphy, Multiplex 388Telegraphy, Step-by-step 494Telemanometer, Electric 521Telemeter, Electric 521Telepherage 522Telephone 522Telephone, Bi- 524Telephone, Capillary 525Telephone, Carbon 525Telephone, Chemical 526Telephone, Electrostatic 526Telephone Exchange 246Telephone Induction Coil 137, 526Telephone, Reaction 527Telephone Record 451Telephone, Thermo-electric 527Telephone Tinnitus 542Telephotography 521Telephote 527Telescope, Reading 450Teleseme 527Tele-thermometer 527Terminal 529Terminal Pole 529Terminal Voltage 562Temperature, Absolute 8Temperature, Neutral 390Temperatures, Laws of Successive 324Tempering, Electric 527Temporary Magnetism or Magnetization 357Ten, Powers of 527Tension 529Tension, Disruptive 189Tension, Electric 529Terrestrial Magnetism 358Tetanus, Acoustic 529Tetrode Working 581Theatrophone 529Theory, Contact 148Theory, Double Fluid 191Theory, Franklin's 262Theory of Dimensions 184Theory of Light, Electro-magnetic 219Theory of Light, Maxwell's 369Theory of Magnetism, Ampére's 354Theory of Magnetism, Ewing's 356Theory of Magnetism, Hughes' 357Theory of Magnetism, Weber's 358Theory, Symmer's 191Therapeutic Electrode 210Therapeutics, Electro- 236Therm 529Thermaesthesiometer 530Thermal Electric Meter 375Thermal Equivalent, Electro- 245Thermal Energy 242Thermic Balance 85Thermo Call 530Thermo-chemical Battery 530Thermo-chemical Equivalent 245Thermo-electric Battery or Pile 530Thermo-electric Call 531Thermo-electric Couple 532Thermo-electric Current 167Thermo-electric Diagram 532Thermo-electric Element 237Thermo-electric Inversion 533Thermo-electric Junction 533Thermo-electric Neutral Point 390Thermo-electric Pile, Differential 533Thermo-electric Power 533Thermo-electric Reversal 533Thermo-electric Series 534Thermo-electric Telephone 527Thermo-electric Thermometer 535Thermo-electricity 533Thermo-electricity, Laws of, Becquerel's 78Thermo-electricity, Volta's Law of 568Thermo-electrometer 536Thermolysis 535Thermo-multiplier 536Thermometer 535Thermometer, Electric 535Thermometer, Kinnersley's 536Thermometer, Tele- 527Thermometer, Thermo-electric 535Thermophone 537Thermostat, Electric 537Third Brush 91Thomson Effect 538Thomson's Replenisher, Sir William 459Thomson's Battery, Sir William 72Thomson's Unit of Resistance 468Three Filament Incandescent Lamp 322Three Way Switch 501Three Wire System 539Throw 237, 540Throw-back Indicator 540Thrust Bearings 540Thunder 540Ticker 540Tick, Magnetic 354Timbre 444Time Constant 541Time Cut-outs 541Time Electric Meter 375Time-fall 541Time-reaction 541Time-rise 541Tin 541Tin Sounders 542Tinnitus, Telephone 542Tips, Polar 423Tips, Pole 290, 426Tissandier's Solution 542Toeppler-Holtz Machine 334Tongs, Cable Hanger 97Tongs, Discharging 189Tongue of Polarized Relay 542Tongue of Polarized Relay, Bias of 542Toothed Core-discs 154Top, Magnetic 542Torpedo, Electric 543Torpedo, Sims-Edison 543Torque 543Torque, Curve of 174Torricellian Vacuum 557Torsion Balance, Coulomb's 544Torsion Galvanometer 273, 544Torsion Head 544Torsion Suspension 545Total Earth 203Touch 545Touch, Separate 479Tourmaline 545Tower, Electric 545Tower System 545Trailing Horns 259Transformer 545Transformer, Commuting 547Transformer, Continuous Alternating 547Transformer, Continuous Current 384, 547Transformer, Core 547Transformer, Faraday's 250Transformer, Hedgehog 548Transformer, Multiple 548Transformer, Oil 548Transformer, Pilot 415Transformer, Series 548Transformer. Sheath for 481Transforming Station 494Transformer, Welding 548, 575Translator 519Translucent Disc Photometer 412Transmitter 548Transmitter, Carbon 549Transmission of Energy, Electric 240Transposing 549Transverse Electro-motive Force 549Trap, Bug 92Traveling Pole 426Trembling Bell 78Trolley 549Trolley, Double 549Trolley Section 549Trough Battery 73Trouvé's Blotting Paper Battery 73Trouvé's Solution 549True Contact Force 549True Ohm 396True Resistance 467Trimmer, Brush 549Trumpet, Electric 550Trunk Lines 550Trunking Switch Board 550Tube, Electric 550Tube, Guard 282Tube, Luminous 550Tube of Magnetic Induction 347Tube, Spark 491Tube, Stratification 495Tubes, Geissler 276Tubes of Force 261Tubes, Plücker 420Tubular Braid 550Tubular Core 155Tubular Magnet 356Tuning Fork Circuit Breaker 121Tuning Fork Dynamo 202Tuning Fork, Interrupter for 307Turning Moment 544Turns 550Turns, Ampere- 31Turns, Dead, of a Dynamo 551Turns, Primary Ampere- 551Turns, Secondary Ampere- 551Twist Joint, American 309Twist, Magnetic 354Tyer's Battery 74Typewriter, Electric 551Type Printer, Hughes' 511 Ultra-gaseous Matter 551Unbuilding 552Underground Conductor 552Underground Electric Subway 552Undulatory 23Undulatory Current 167Unidirectional 553Uniform Field 256Uniform Field of Force 553Uniform Magnetic Field 345Unipolar 553Unipolar Armature 50, 553Unipolar Current Induction 553Unipolar Dynamo 202-553Unipolar Electric Bath 57Unipolar Induction 304Unipolar Magnet 366Unit 553Unit, Absolute 554Unit Angle 554Unit. B. A. 554Unit, B. A. , of Resistance 462Unit Current 167Unit Electro-motive Force 228Unit, Fundamental 554Unit Jar 554Unit Magnet Pole 366Unit of Capacity 105Unit of Conductivity 145Unit of Electric Potential 432Unit of Energy, Electro-magnetic 220Unit of Force 261Unit of Illumination 296Unit of Output 399Unit of Reluctance 458Unit of Resistance, B. A. 78Unit of Resistance, Breguet 463Unit of Resistance, Digney 464U nit of Resistance, English Absolute or Foot-second 465Unit of Resistance, German Mile 466Unit of Resistance, Jacobi's 466Unit of Resistance, Meter-millimeter. 466Unit of Resistance, Mil-foot 467Unit of Resistance, Siemens' 467Unit of Resistance, Swiss 468Unit of Resistance, Thomson's 468Unit of Resistance, Varley's 468Unit of Self-induction 304Unit of Supply 554Unit of Work 581Unit Resistance 468Units, Circular 126, 555Units, Derived 555Units, Heat 288Units, Practical 555Universal Battery System 556Universal Discharger 189Unmarked End 556Upright Galvanometer 274Upward's Battery 75 V 556V. A. 557Vacuum 557Vacuum, Absolute 557Vacuum, High 557Vacuum Lightning Arrester 329Vacuum, Low 557Vacuum, Partial 557Vacuum, Torricellian 557Valency 557Valve, Electrically Controlled 558Vapor Globe 558Variable Conductivity 145Variable Period 558Variable State 558Variation of the Compass 32, 558Variations, Magnetic 354Variometer 559Varley's Battery 76Varley's Condenser 559Varley's Resistance 559Varley's Unit of Resistance 468Varnish 559Varnish, Electric 559Varnish, Insulating 306Varnish, Red 559Varnish, Shellac 481Vat 559Velocity 559Velocity, Angular 32, 559Velocity of Signaling 560Velocity Ratio 560Ventilation of Armature 560Vertical Galvanometer 274Vertical Induction 304Verticity, Poles of 426, 560Vibrating Bell 78Vibration Period 560Vibration, Sympathetic 501, 561Vibrator, Electro-magnetic 561Villari's Critical Value 561Viole 562Viole's Standard of Illuminating Power 561Virtual Resistance 297Viscous Hysteresis 295, 356Vis Viva 562Vitreous Electricity 562Vitriol, Blue 562Vitriol, Green 562Vitriol, White 562Volatilization of Carbon 108Volt 562Volt-ampere 573Volt and Ampere Meter Galvanometer 274Volt, B. A. 568Volt, Congress 568Volt, Coulomb 568, 573Volt Indicator 568Volt. Legal 568Voltage 562Voltage, Spurious 493Voltage, Terminal 562Voltaic 563Voltaic Alternatives 563Voltaic Arc 39Voltaic Cell, Daniell's Standard 109Voltaic Cell, Double Fluid 191Voltaic Cell, Capacity of Polarization of a 103Voltaic Cell, Single Fluid 486Voltaic Cell, Standard 109Voltaic Cell, Standard, Latimer Clark's 110Voltaic Circuit 126Voltaic Effect 563Voltaic Electricity 563Voltaic Element 237Voltaic or Galvanic Battery 76Voltaic or Galvanic Circle 119Voltaic or Galvanic Couple 156Voltameter 563Voltameter, Copper 563Voltameter, Differential, Siemens' 564Voltameter, Faraday's 250Voltameter, Gas 564Voltameter, Silver 565Voltameter, Sulphuric Acid 564Voltameter, Volume 564Voltameter, Weight 566Voltametric Law 567Volta's Battery 76Volta's Fundamental Experiments 567Volta's Law of Galvanic Action 568Volta's Law of Thermo-electricity 568Voltmeter 568Voltmeter, Battery 569Voltmeter, Cardew 569Voltmeter, Electrostatic 571Voltmeter, Reducteur for 453Volts, Lost 571Volume Voltameter 564Vulcanite 571 W 572Wall Bracket 572Wall Socket 572Ward 572Waste Field 256Water 572Water Battery 77Water Equivalent 572Water Level Alarm 18Waterproof Lamp Globe 572Wattless Current 168Watt 572Watt-hour 573Watt Meter 375Watt-minute 573Watt-second 573Watts, Apparent 573Wave Winding 580Waves, Amplitude of 31Waves. Electro-magnetic 573Wax, Paraffine 402Weber 574Weber s Absolute Unit Resistance 468Weber-meter 574Weber's Theory of Magnetism 358Wedge Cut-out 175Wedge. Double 191Weight, Atomic 53Weight, Breaking 89Weight Electrometer 223Weight Voltameter 566Welding, Electric 574Welding Transformer 548, 575Wheatstone's A. B. C. Telegraph 521Wheatstone's Balance 577Wheatstone's Bridge 575Wheatstone's Bridge, Commercial 86Wheatstone's Rheostat 472Wheel, Phonic 409Wheel, Reaction 259Whirl, Electric 577White Vitriol 562Wilde Candle 101Wimshurst Electric Machine 335, 577Wimshurst Machine 335, 577Wind, Electric 578Windage 578Windings, Ampere 31Winding, Bifilar 81Winding, Compound 578Winding, Disc 579Winding, Lap 579Winding, Long Shunt 579Winding, Long Shunt and Series 579Winding, Multiple 579Winding, Multipolar 579Winding, Series 579Winding, Series and Separate Coil 579Winding, Series and Short Shunt 580Winding, Short Shunt 579Winding, Shunt 483, 580Winding Shuttle 580Winding, Wave 580Winding Working, Differential 183Wire, Block 83Wire, Bus 94Wire, Dead 177Wire Finder 580Wire Gauze Brush 92Wire, Idle 296Wire, Neutral 390Wire, Omnibus 94Wire, Square 493Wire System, Three 539Wires, Crossing 158Wires, Leading-in 324Wires, Phantom 409Wires, Pilot 415Wollaston Battery 78Work 580Work, Electric, Unit of 580Work, Unit of 581Working, Contraplex 580Working, Diode 580Working, Diplex 580Working, Double Curb 581Working, Hexode 581Working, Pentode 581Working, Reverse Current 581Working, Single Curb 581Working Tetrode 581Writing Telegraph 521 X, Axis of 54 Y, Axis of 54, 397Yoke 581 Zamboni's Dry Pile 581Zero 581Zero, Absolute 581Zero Potential 432, 582Zero, Thermometric 582Zinc 582Zinc Sender 582Zincode 582Zone, Peripolar 582Zone, Polar 582