THE

 HURRICANE GUIDE:

 BEING

 AN ATTEMPT TO CONNECT THE

 ROTATORY GALE OR REVOLVING STORM

 WITH

 ATMOSPHERIC WAVES. 

 INCLUDING INSTRUCTIONS FOR OBSERVING THE PHÆNOMENA OF THE WAVES AND STORMS;

 WITH

 PRACTICAL DIRECTIONS FOR AVOIDING THE CENTRES OF THE LATTER. 

 BY

 WILLIAM RADCLIFF BIRT. 

 LONDON: JOHN MURRAY, ALBEMARLE STREET. _PUBLISHER TO THE ADMIRALTY. _ 1850. 

 PRINTED BY W. CLOWES AND SONS, STAMFORD STREET. 

PREFACE. 

In introducing the following pages to the notice of the Public, it isthe Author's wish to exhibit in as clear a light as our presentresearches on the subjects treated of will allow, the connexion betweenone of the most terrific phænomena with which our globe is visited, anda phænomenon which, although but little known, appears to be intimatelyconnected with revolving storms. How far he has succeeded, either inthis particular object or in endeavouring to render the essentialphænomena of storms familiar to the seaman, is left for the Public todetermine. Should any advantage be found to result from the study of theAtmospheric Waves, as explained and recommended in this little work, orthe seaman be induced by its perusal to attend more closely to theobservations of those instruments that are calculated to warn him of hisdanger, an object will be attained strikingly illustrative of theBaconian aphorism, "Knowledge is Power. "

 _Bethnal Green_, April 19, 1849. 

 CONTENTS. 

 PAGE

 CHAP. I. --PHÆNOMENA OF REVOLVING STORMS 7

 " II. --PHÆNOMENA OF ATMOSPHERIC WAVES 13

 " III. --OBSERVATIONS 18

 SECT. I. --Instruments 19

 " II. --Times of Observation 28

 " III. --Localities for Additional Observations 31

 " IV. --Storms, Hurricanes, and Typhoons 43

 " V. --Seasons for Extra Observations 48

 " IV. --PRACTICAL DIRECTIONS FOR AVOIDING THE CENTRES OF STORMS 52

NOTICE. 

In the pocket accompanying this work are two rings of stiff cardboard, on which will be found all the information contained in figures 1 and 2. When they are laid flatly upon a chart, the continuity of the lines onthe chart is not materially interfered with, while the idea of a body ofair rotating in the direction indicated by the arrows is conspicuouslypresented to the mind. These rings are more particularly referred to onpage 52. 

THE

HURRICANE GUIDE. 

CHAPTER I. 

PHÆNOMENA OF REVOLVING STORMS. 

It is the object of the following pages to exhibit, so far asobservation may enable us, and in as brief a manner as possible, theconnexion, if any, that exists between those terrific meteorologicalphænomena known as "revolving storms, " and those more extensive andoccult but not less important phænomena, "atmospheric waves. "

To the great body of our seamen, whether in her Majesty's or themercantile service, the subject can present none other than the mostinteresting features. The laws that govern the transmission of largebodies of air from one part of the oceanic surface to another, either ina state of rapid rotation or presenting a more or less rectilinealdirection, must at all times form an important matter of inquiry, andbear very materially on the successful prosecution of the occupation ofthe voyager. 

In order to place the subjects above alluded to in such a point of viewthat the connexion between them may be readily seen, it will beimportant to notice the principal phænomena presented by each. Withoutgoing over the ground so well occupied by those able writers on thesubject of storms--Redfield, Reid, Piddington, and Thom--it will bequite sufficient for our present purpose simply to notice the essentialphænomena of revolving storms as manifested by the barometer and vane. The usual indications of a storm in connexion with these instruments arethe _falling_ of the barometer and the _freshening_ of the wind, and itis generally considered that a _rapid_ fall of the mercury in thehurricane regions invariably precedes the setting in of a storm. 

There are three classes of phænomena that present themselves to anobserver, according as he is situated _on_ the line or axis oftranslation, or _in_ either the right or left hand semicircle of thestorm. These will be rendered very apparent by a little attention to theannexed engraving, fig. 1. 

[Illustration: Compass rose]

In this figure the arrow-head is supposed to be directed true north, andthe hurricane--as is the case in the American storms north of the 30thparallel--to be moving towards the N. E. On the line N. E. --S. W. If theship take the hurricane with the wind S. E. , --the letters within the twolarger circles indicating _the direction of the wind in the storm_according to the rotation as shown by the circle of arrow-heads, andwhich it is to be particularly noted is in the northern hemisphere_contrary to the direction in which the hands of a watch move_: in thesouthern hemisphere the rotation is reversed--the only phænomenapresented by the storm are as follows:--The wind continues to blow fromthe S. E. , increasing considerably in force with the barometer falling toa very great extent until the centre of the storm reaches the ship, whenthe fury of the winds is hushed, and a lull or calm takes place, generally for about half an hour, after which the wind springs up mostlywith increased violence, but from the opposite quarter N. W. , thebarometer begins to rise, and as the storm passes off, the force of thewind abates. 

The point to which we wish particularly to direct attention in connexionwith this exposition of the phænomena attending the transmission of astorm is this:--If the observer so place himself at the commencementthat the wind passes _from his left hand towards his right_, his facewill be directed towards the centre of the storm; and the windundergoing no change in direction, but only in force, will acquaint himwith this important fact that the _centre_ is not only gradually butsurely approaching him: in other words, in the case before us, when hefinds the wind from the S. E. , and he places himself with his face to theS. W. He is looking towards the centre, and the wind rushes past him_from his left to his right hand_. Now the connexion of the barometerwith this phase of the storm is _falling with the wind from left toright, the observer facing the centre while the first half istransiting_. [1] During the latter half these conditions are reversed, the observer still keeping his position, his face directed to the S. W. , the barometer _rises_ with a N. W. Wind, which rushes past him _from hisright to his left hand_ with a decreasing force. We have therefore _arising barometer with the wind from right to left during the latter halfof the storm, the observer having his back to the centre_. 

The above _general_ enunciations of the barometric and anemonalphænomena of a rotating storm hold good with regard to the _northern_hemisphere, whatever may be the direction in which the hurricanesadvance. This may be placed in a clearer light, as well as the remainingclasses of phænomena shown, by consulting the following tables, constructed for the basin of the Northern Atlantic, and comparing themwith fig. 1. In this basin, with lower latitudes than 25°, the usualpaths of the hurricanes are towards the north-west, in higher latitudesthan 30° towards the north-east. The tables exhibit the veering of thewind with the movements of the barometer, according as the ship issituated in the right or left hand semicircle of the hurricane. It musthere be understood that the right and left hand semicircles aredetermined by the observer so placing himself that his face is directedtowards the quarter to which the hurricane is advancing. 

LOWER LATITUDES. 

NORTHERN HEMISPHERE. 

 Axis line, wind N. E. , barometer falling, first half of storm. Axis line, wind S. W. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind E. N. E. , E. , E. S. E. , S. E. , barometer falling, storm increasing. Wind S. S. W. , S. , S. S. E. , S. E. , barometer rising, storm passing off. 

LEFT-HAND SEMICIRCLE. 

 Wind N. N. E. , N. , N. N. W. , N. W. , barometer falling, storm increasing. Wind W. S. W. , W. , W. N. W. , N. W. , barometer rising, storm passing off. 

HIGHER LATITUDES. 

NORTHERN HEMISPHERE. [2]

 Axis line, wind S. E. , barometer falling, first half of storm. Axis line, wind N. W. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind S. S. E. , S. , S. S. W. , S. W. , barometer falling, storm increasing. Wind W. N. W. , W. , W. S. W. , S. W. , barometer rising, storm passing off. 

LEFT-HAND SEMICIRCLE. 

 Wind E. S. E. , E. , E. N. E. , N. E. , barometer falling, storm increasing. Wind N. N. W. , N. , N. N. E. , N. E. , barometer rising, storm passing off. 

N. B. The directions of the hurricane winds are so arranged as to showthe points of commencement and termination. Thus in the lower latitudesa storm commencing at E. N. E. Passes off at S. S. W. After the wind hasveered E. , E. S. E. , S. E. , S. S. E. , and S. , being in the order of theletters in the upper line and contrary to their order in the lower. Onecommencing at E. S. E. Passes off at S. S. E. Right-hand semicircle. In thehigher latitudes a ship taking the storm at E. N. E. Will be in theleft-hand semicircle, and the hurricane will pass off at N. N. E. Thesechanges are rendered very apparent by moving the hurricane circle in thedirection in which the storm is expected to proceed. 

Fig. 2 represents the whirl and hurricane winds in the south. 

[Illustration: Fig. 2]

CHAPTER II. 

PHÆNOMENA OF ATMOSPHERIC WAVES. 

Professor Dove of Berlin has suggested that in the temperate zones thecompensating currents of the atmosphere necessary to preserve itsequilibrium may be arranged as parallel currents on the _surface_, andnot superposed as in or near the torrid zone. His views may be thusenunciated:--That in the parallels of central Europe the N. E. Currentflowing towards the equator to feed the ascending column of heated airis not compensated by a current in the upper regions of the atmosphereflowing from the S. W. As in the border of the torrid zone, but there arealso S. W. Currents on each side the N. E. , which to the various countriesover which they pass appear as surface-winds, the winds in fact beingdisposed in alternate beds or layers, S. W. , N. E. , as in fig. 3. 

[Illustration: Fig. 3. ]

The Professor also suggests that these parallel and oppositely directedwinds are shifting, _i. E. _ they gradually change their position with alateral motion in the direction of the large arrow cutting themtransversely. 

In the course of the author's researches on atmospheric waves he had anopportunity of testing the correctness of Professor Dove's suggestion, and in addition ascertained that there existed another set of oppositelydirected winds at right angles to those supposed to exist by theProfessor. These currents were N. W. And S. E. With a lateral motiontowards the N. E. He also carefully discussed the barometric phænomenawith relation to both these sets of currents, and arrived at thefollowing conclusions. The details will be found in the author's thirdreport, presented to the British Association for the Advancement ofScience (Reports, 1846, pp. 132 to 162). During the period underexamination the author found the barometer generally to rise with N. E. And N. W. Winds, and fall with S. W. And S. E. Winds, and that thephænomena might be thus illustrated:--Let the strata _a a a' a', b' b' bb_, fig. 3, represent two parallel aërial currents or winds, _a a a' a'_from S. W. Or S. E. , and _b' b' b b_ from N. E. Or N. W. And conceive themboth to advance from the N. W. In the first instance and from the S. W. Inthe second, in the direction of the large arrow. Now conceive thebarometer to commence rising just as the edge _b b_ passes any line ofcountry, and to continue rising until the edge _b' b'_ arrives at thatline, when the maximum is attained. It will be remarked that this riseis coincident with a N. E. Or N. W. Wind. The wind now changes and thebarometer begins to fall, and continues falling until the edge _a a_coincides with the line of country on which _b b_ first impinged. During this process we have all the phænomena exhibited by anatmospheric wave: when the edge _b b_ passes a line of country thebarometer is at a _minimum_, and this minimum has been termed the_anterior trough_. During the period the stratum _b' b' b b_ transits, the barometer rises, and this rise has been called the _anterior slope_. When the conterminous edges of the strata _a' a' b' b'_ pass, abarometric _maximum_ extends along the line of country formerly occupiedby the anterior trough, and this maximum has been designated the_crest_. During the transit of the stratum _a' a' a a_ the barometer_falls_, and this fall has been characterised as the _posterior slope_;and when the edge _a a_ occupies the place of _b b_, the descent of themercurial column is completed, another _minimum_ extends in thedirection of the former, and this minimum has been termed the _posteriortrough_. 

It will be readily seen that the lateral passage of the N. W. And S. E. Currents towards the N. E. Presents precisely the same barometric andanemonal phænomena as the rotatory storms when moving in the samedirection. If the observer, when the barometer is at a _maximum_ with aN. W. Wind, place himself in the same position with regard to thelaterally advancing current as he did with regard to the advancingstorm, _i. E. _ with his face _towards_ the quarter from which it isadvancing--S. W. , he will find that with a _falling barometer and S. E. Wind the current passes him from the left to the right hand_; but if ata barometric _minimum_ he place himself in the same position with hisface directed to the quarter from which the N. W. Current is advancinglaterally, also S. W. , he will find that with a rising barometer _andN. W. Wind the current passes him from right to left_. Now the twoclasses of phænomena are identical, and it would not be difficult toshow that, had we an instance of a rotatory storm in the northernhemisphere moving from N. W. To S. E. , it would present precisely the samephænomena as to the direction of currents passing from left to right andfrom right to left with falling and rising barometers, increase anddecrease in the force of the wind, &c. , as the oppositely directedaërial currents do which pass over western central Europe. 

In the absence of direct evidence of the production of a revolving stormfrom the crossing of two large waves, as suggested by Sir John Herschel, although it is not difficult to obtain such evidence, especially fromthe surface of the ocean, the identity of the two classes of phænomenaexhibited by the storms and waves as above explained amounts to a strongpresumption that there is a close connexion between them, and that amore minute investigation of the phænomena of atmospheric waves isgreatly calculated to throw considerable light on the laws that governthe storm paths in both hemispheres. The localities in which theseatmospheric movements, the waves, have been hitherto studied, have beenconfined to the northern and central parts of Europe--the west ofIreland, Alten in the north of Europe, Lougan near the Sea of Azov, andGeneva, being the angular points of the included area. It will beremarked that the greatest portion of this area is _inland_, but thereis one important feature which the study of the barometer has brought tolight, and which is by no means devoid of significance, viz. That theoscillations are much greater in the neighbourhood of _water_, and thisappears to indicate that the junction lines of land and water form byfar the most important portions of the globe in which to study both thephænomena of storms and waves. It is also very desirable that ourknowledge of these phænomena should, with immediate reference to thesurface of the ocean, be increased, and in this respect captains andmasters of vessels may render essential service by observing andrecording the state of the barometer, and direction and force of thewind, several times in the course of the day and night;[3] and when itis considered that the immediate object in view is one in which themariner is personally interested, and one in which, it may be, his ownsafety is concerned, it is hoped that the keeping of a meteorologicalregister having especial reference to the indications of the barometer, and force and direction of the wind, will not be felt as irksome, butrather will be found an interesting occupation, the instruments standingin the place of faithful monitors, directing when and where to avoiddanger, and the record furnishing important data whereby the knowledgeof general laws may be arrived at, having an essential bearing on theinterests of the service at large. 

CHAPTER III. 

OBSERVATIONS. 

In sketching out a system of observation having especial reference toatmospheric waves and rotatory storms, regard has been had--_first_, tothe instruments that should be used, the observations to be made withthem, the corrections to be applied to such observations, and the formof registry most suitable for recording the results: _second_, to thetimes of observation: _third_, to the more important localities thatshould be submitted to additional observation: _fourth_, to peculiarphænomena requiring extraordinary observations for their elucidation:and _fifth_, to particular seasons, when the instruments should bewatched with more than ordinary care. 

The more important objects of observation having especial reference toatmospheric waves are those points which have been termed _crests_ and_troughs_. These are simply the _highest_ and _lowest_ readings of thebarometer, usually designated _maxima_ and _minima_, and should for theobject in view receive particular attention. Whenever there is reason tobelieve that the barometer is approaching either a _maximum_ or_minimum_, additional observations should be resorted to, so as tosecure as nearly as possible _the precise time_ as reckoned at the ship, with her position, of its occurrence, as well as the altitude of themercurial column at that time and place. By means of such observationsas these on board several ships scattered over the surfaces of our greatoceans, much valuable information may be accumulated of a charactercapable of throwing considerable light on the _direction_ in which thelines of barometric maxima and minima stretch, and also a tolerablyaccurate notion may be formed of their progress, both as regardsdirection and rate. In immediate connexion with such observationsparticular attention should be paid to the direction of the windaccording to the season. 

SECTION I. --INSTRUMENTS. 

_Description and Position of Instruments. _--The principal instrumentrequisite in these observations is the barometer, which should be of themarine construction, and as nearly alike as possible to those furnishedto the Antarctic expedition which sailed under the command of Sir JamesClark Ross. These instruments were similar to the ordinary portablebarometers, and differed from them only in the mode of their suspensionand the necessary contraction of the tubes to prevent oscillation fromthe motion of the ship. The barometer on shipboard should be suspendedon a gimbal frame, which ought not to swing too freely, but rather so asto deaden oscillations by some degree of friction. To the upper portionof the tube in this construction of instrument light is alike accessibleeither in front or behind, and the vernier is furnished with a back andfront edge, both being in precisely the same plane, nearly embracing thetube, and sliding up and down it by the motion of rack-work; by thegraduation of the scale and vernier the altitude of the mercury can beread off to ·002 inch. 

When the barometer is placed in the ship, its position should be as nearmidships as possible, out of the reach of sunshine, but in a good lightfor reading, and in a situation in which it will be but little liable tosudden gusts of wind and changes of temperature. Great care should betaken to ascertain the exact height of its cistern above the water-line, and in order to facilitate night observations every possible arrangementshould be made for placing behind it a light screened by white paper. 

_Observations. _--The first thing to be done is the reading off andrecording the temperature indicated by the thermometer that in thisconstruction of instrument dips into the mercury in the cistern. SirJohn Herschel has suggested that "the bulb of the thermometer should beso situated as to afford the best chance of its indicating the exactmean of the whole barometric column, that is to say, fifteen inchesabove the cistern enclosed within the case of the barometer, nearly incontact with its tube, and with a stem so long as to be read off at theupper level. "

Previous to making an observation with the barometer the instrumentshould be slightly tapped to free the mercury from any adhesion to theglass; any violent oscillation should, however, be carefully avoided. The vernier should then be adjusted to the upper surface of the mercuryin the tube; for this purpose its back and front edges should be made tocoincide, that is, the eye should be placed in exactly the same planewhich passes through the edges; they should then be brought carefullydown until they form a tangent with the curve produced by the convexsurface of the mercury and the light is _just_ excluded from betweenthem and the point of contact. It is desirable in making this adjustmentthat the eye should be assisted by a magnifying-glass. The reading ofthe scale should then be taken and entered in the column appropriated toit in the proper form. If the instrument have no tubular or double-edgedindex, the eye should be placed carefully at the level of the uppersurface of the mercury and the index of the vernier brought gently downto the same level so as apparently just to touch the surface, great carebeing taken that the eye index and surface of the mercury are all in thesame plane. 

Each observation of the barometer should be accompanied by anobservation of the direction of the wind, which should be noted in theusual manner in which it is observed at sea. In connexion with the_direction_ the _force_ of the wind should be recorded in accordancewith the following scale, contrived by Admiral Sir Francis Beaufort:--

 0. Calm 1. Light air or just sufficient to give steerage way. 2. Light breeze { or that in which a well- } 1 to 2 knots. 3. Gentle breeze { conditioned man of war, } 3 to 4 knots. 4. Moderate breeze { with all sail set, and } 5 to 6 knots. { clean full, would go in } { smooth water, from } 5. Fresh breeze } { Royals, &c. 6. Strong breeze } { Single-reefed top-sails } { and top-gallant } or that in which such a { sails. 7. Moderate gale } ship could just carry in { Double-reefed } chase full and by { topsails, jib, &c. 8. Fresh gale } { Triple-reefed } { topsails, &c. 9. Strong gale } { Close-reefed top-sails } { and courses. 

 10. Whole gale or that with which she could scarcely bear close-reefed main topsail and reefed foresail. 11. Storm or that which reduces her to storm staysails. 12. Hurricane or that which no canvas could withstand. 

_Corrections. _--As soon after the observations have been made ascircumstances will permit, the reading of the barometer should be_corrected_ for the relation existing between the capacities of the tubeand cistern (if its construction be such as to require that correction), and for the capillary action of the tube; and then _reduced_ to thestandard temperature of 32° Fahr. , and to the sea-level, if onshipboard. For the first correction the _neutral point_ should be markedupon each instrument. It is that particular height which, in itsconstruction, has been actually measured from the surface of the mercuryin the cistern, and indicated by the scale. In general the mercury willstand either above or below the neutral point; if _above_, a portion ofthe mercury must have left the cistern, and consequently must have_lowered_ the surface in the cistern: in this case the altitude asmeasured by the scale will be _too short--vice versâ_, if below. Therelation of the capacities of the tube and cistern should beexperimentally ascertained, and marked upon the instrument by the maker. Suppose the capacity to be 1/50, marked thus on the instrument, "_Capacity 1/50:_" this indicates that for every inch of variation ofthe mercury in the tube, that in the cistern will vary contrariwise1/50th of an inch. When the mercury in the tube is _above_ the neutralpoint, the difference between it and the neutral point is to be reducedin the proportion expressed by the "capacity" (in the case supposed, divided by 50), and the quotient _added_ to the observed height; if_below, subtracted_ from it. In barometers furnished with a fiducialpoint for adjusting the lower level, this correction is superfluous, andmust not be applied. 

The second correction required is for the capillary action of the tube, the effect of which is always to depress the mercury in the tube by acertain quantity inversely proportioned to the diameter of the tube. This quantity should be experimentally determined during theconstruction of the instrument, and its amount marked upon it by themaker, and is always to be _added_ to the height of the mercurialcolumn, previously corrected as before. For the convenience of those whomay have barometers, the capillary action of which has not beendetermined, a table of corrections for tubes of different diameters isplaced in the Appendix, Table I. 

The next correction, and in some respects the most important of all, isthat due to the temperature of the mercury in the barometer tube at thetime of observation, and to the expansion of the scale. Table II. Of theAppendix gives for every degree of the thermometer and every half-inchof the barometer, the proper quantity to be added or subtracted for thereduction of the observed height to the standard temperature of themercury at 32° Fahr. 

After these the index correction should be applied. This is the amountof difference between the particular instrument and the readings of theRoyal Society's flint-glass barometer when properly corrected, and isgenerally known as the _zero_. It is impossible to pay too muchattention to the determination of this point. For this purpose, whenpracticable, the instrument should be immediately compared with theRoyal Society's standard, and the difference of the readings of bothinstruments, when corrected as above, carefully noted and preserved. Where, however, this is impracticable, the comparison should be effectedby means either of some other standard previously so compared, or of anintermediate portable barometer, the zero point of which has been _welldetermined_. Suspend the portable barometer as near as convenient to theship's barometer, and after at least an hour's quiet exposure, take asmany readings of both instruments as may be necessary to reduce theprobable error of the mean of the differences below 0. 001 inch. Underthese circumstances the mean difference of all the readings will be the_relative_ zero or index error, whence, if that of the intermediatebarometer be known, that of the other may be found. As such comparisonswill always be made when the vessel is in port, sufficient time can beallowed for making the requisite number of observations: hourly readingswould perhaps be best, and they would have the advantage of forming partof the system when in operation, and might be accordingly used as such. 

It is not only desirable that the zero point of the barometer should bewell determined in the first instance; it should also be carefullyverified on every opportunity which presents itself; and in everyinstance, previous to sailing, it should be re-compared with thestandard on shore by the intervention of a portable barometer, and noopportunity should be lost of comparing it on the voyage by means ofsuch an intermediate instrument with the standard barometers at St. Helena, the Cape of Good Hope, Bombay, Madras, Paramatta, Van Diemen'sIsland, and with any other instruments likely to be referred to asstandards, or employed in research elsewhere. Any vessel having aportable barometer on board, the zero of which has been well determined, would do well, on touching at any of the ports above named, to takecomparative readings with the standards at those ports, and record thedifferences between the standard, the portable, and the ship barometers. By such means the zero of one standard may be transported over the wholeworld, and those of others compared with it ascertained. To do so, however, with perfect effect, will require that the utmost care shouldbe taken of the portable barometer; it should be guarded as much aspossible from all accident, and should be kept safely in the "portable"state when not immediately used for comparison. To transport awell-authenticated zero from place to place is by no means a point oftrifling importance. Neither should it be executed hurriedly nornegligently. Some of the greatest questions in meteorology depend on itsdue execution, and the objects for which these instructions have beenprepared will be greatly advanced by the zero points of all barometersbeing referred to one common standard. Upon the arrival of the vessel inEngland, at the termination of the voyage, the ship's barometer shouldbe again compared with the same standard with which it was comparedprevious to sailing; and should any difference be found, it should bemost carefully recorded. 

The correction for the height of the cistern _above_ or _below_ thewater-line is _additive_ in the former case, _subtractive_ in thelatter. Its amount may be taken, nearly enough, by allowing 0·001 in. Ofthe barometer for each foot of difference of level. 

An example of the application of these several corrections issubjoined:--

 | _Attached Therm_. 54°·3. |_Data for the correction of | | | the Instrument_. | +---------------------------------------+-------------------------------+ |Barometer reading. 29·409 |Neutral point 30·123 | |Corr. For capacity - ·017 |Capacity 1/42 | | |Capillary action + ·032 | +---------------------------------------| | | 29·392 |Zero to Royal Society + ·036 | |Corr. For capillarity + ·032 |Corr. For altitude above | | | water-line + ·004 | +---------------------------------------| | | 29·424 | | |Corr. For temperature - ·068 | | +---------------------------------------| | | 29·356 | | |Corr. For zero and water-line + ·040 | | +---------------------------------------| | |Aggregate = pressure at | | | sea-level 29·396 | | +---------------------------------------+-------------------------------+

It would greatly facilitate the comparison of the barometricobservations by projecting them in curves when all the propercorrections have been applied. This may be accomplished by a muchsmaller expenditure of time than may at first be supposed. A paper ofengraved squares on which the observations of twelve days may be laiddown on double the natural scale, would be very suitable for thepurpose. [4] The projection of each day's observations would occupy but ashort time; and should circumstances on any occasion prevent theexecution of it, when the ship was becalmed or leisure otherwiseafforded, it would form an interesting and useful occupation, and serveto beguile some of the tedium often experienced at such intervals. 

_Registers. _--For the particular object in view the register need not bevery extensive. One kept in the annexed form will be amply sufficient. It should, however, be borne in mind that none but _uncorrected_observations should find admission; in point of fact it should bestrictly a register of phænomena as _observed_, and on no accountwhatever should any entry be made from recollection, or any attempt madeto fill up a blank by the apparent course of the numbers before andafter. The headings of the columns will, it is hoped, be sufficientlyexplicit. It is desirable in practice that the column for remarks shouldembrace an entire page opposite the other entries, in order thatoccasional observations, as well as several other circumstancescontinually coming under review in the course of keeping a journal, mayfind entry. 

METEOROLOGICAL REGISTER kept on board ______ during her voyage from ______ to ______ by ______. 

 +---------+----+------+-------+------+------------------+--------+----------+ | | | | | | Wind. | | | | | | | | Att. |-----------+------| | | | Date. |Lat. | Long. | Barom. | Ther. | Direction. |Force. | Remarks| Observer. | |---------|----|------|-------|------|-----------|------|--------|----------| | |h. M. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +---+-----+----+------+-------+------+-----------+------+--------+----------+

The only difference between the above form and one for the reception of_corrected_ readings will be the dispensing with the column for theattached thermometer, and placing under the word Barom. "corrected. "

II. --TIMES OF OBSERVATION. 

There can be no question that the greatest amount of information, theaccuracy of the data supplied, and in fact every meteorological elementnecessary to increase our knowledge of atmospheric waves, may be bestobtained by an uninterrupted series of _hourly_ observations made onboard vessels from their leaving England until their safe arrival againat the close of their respective voyages; but from a variety ofcircumstances--the nature of the service in which the vessels may beemployed, particular states of the weather, &c. --such a course ofunremitting labour cannot be expected; it is therefore necessary to fixon some stated hours at which the instruments before particularizedshould be regularly observed throughout the voyage, and theirindications faithfully recorded. The hours of 3 A. M. , 9 A. M. , 3 P. M. , and 9 P. M. , are now so generally known as _meteorological hours_, thatnothing should justify a departure from them; and it is the moreessential that these hours should be adopted in the present inquiry, because the series of observations made at intervals terminated by thesehours can the more readily be used in connexion with those madecontemporaneously on land, and will also serve to carry oninvestigations previously instituted, and which have receivedconsiderable illustration by means of observations at the regularmeteorological hours; we therefore recommend their general adoption inall observations conducted at sea. 

It is intended in the sequel to call attention to particular parts ofthe earth's surface where it is desirable that additional observationsshould be made, in order to furnish data of a more accurate character, and to mark more distinctly barometric changes than the four dailyreadings are capable of effecting. The best means of accomplishing thisfor the object in view appears to be the division of the interval of sixhours into two equal portions, and to make the necessary observationseight times in the course of twenty-four hours. In the particularlocalities to which allusion has been made we recommend the following asthe hours of observation:--

A. M. 3, 6, 9, noon. P. M. 3, 6, 9, midnight. 

In other localities besides those hereafter to be mentioned, whenopportunities serve, readings at these hours would greatly enhance thevalue of the four daily readings. 

There are, however, portions of the surface of our planet, and probablyalso phænomena that occur in its atmosphere, which require still closerattention than the eight daily readings. One such portion would appearto exist off the western coast of Africa, and we recommend the adoptionof _hourly_ readings while sailing to the westward of this junction ofaqueous and terrestrial surface; more attention will be directed to thispoint as we proceed. There are also phænomena the localities of whichmay be undetermined, and the times of their occurrence unknown, but soimportant a relation do they bear to the subject of our inquiries, thatthey demand the closest attention. They will be more particularlydescribed under the head of accumulations of pressure preceding andsucceeding storms, and minute directions given for the hourlyobservations of the necessary instruments. In the mean time we may hereremark that hourly observations under the circumstances above alluded toare the more important when we consider that the barometer, theinstrument employed in observing these moving atmospheric masses, isitself in motion. The ship may meet the accumulation of pressure andsail through it transversely; or she may sail along it, the course ofthe vessel being parallel to the line marking the highest pressure, theridge or crest of the wave; or the ship may make any angle with thisline: but whatever the circumstances may be under which she passesthrough or along with such an accumulation of pressure, it should everbe borne in mind that her position on the earth's surface is scarcelyever the same at any one observation as it was at the preceding, thebarometer in the interval has changed _its_ position as well as the lineof maximum pressure, the rate of progress of which it is desirable toobserve. It will, therefore, be at once apparent that in order to obtainthe most accurate data on this head hourly observations areindispensable. To these readings should of course be appended the placesof the ship from hour to hour, especially if she alter her course much. 

There is another point to which we wish to call attention in immediateconnexion with hourly readings--it is the observation of the instrumentson the days fixed for that purpose: they were originally suggested bySir John Herschel, whose directions should be strictly attended to: theyare as follows:--

The days fixed upon for these observations are the 21st of March, the21st of June, the 21st of September, and the 21st of December, beingthose, or immediately adjoining to those of the equinoxes andsolstices, in which the _solar influence_ is either stationary or in astate of most rapid variation. _But should any one of those 21st daysfall on a Sunday, then it will be understood that the observations areto be deferred till the next day, the 22nd. _ The series of observationson board each vessel should commence at 6 o'clock A. M. Of the appointeddays, and terminate at 6 A. M. Of the days following, according to theusual reckoning of time adopted in the daily observations. 

In addition to the twenty-five hourly readings at the solstices andequinoxes as above recommended, it would be desirable to continue theobservations until a complete elevation and depression of the barometerhad been observed at these seasons. This plan is adopted at the RoyalObservatory, Greenwich, and would be attended with this advantage wereit generally so--the progress of the elevation and depression would bemore readily traced and their velocities more accurately determined thanfrom the four or eight daily readings. 

III. --LOCALITIES FOR ADDITIONAL OBSERVATIONS. 

In sketching out a system of barometric observation having especialreference to the acquisition of data from which the _barometriccharacter_ of certain large areas of the surface of the globe may bedetermined--inasmuch as such areas are distinguished from each other, onthe one hand by consisting of extensive spaces of the oceanic surfaceunbroken, or scarcely broken, by land; on the other by the proximity ofsuch oceanic surface to large masses of land, and these massespresenting two essentially different features, the one consisting ofland particularly characterized as continental, the other as insular, regard has been accordingly had to such distribution of land and water. 

As these instructions have especial reference to observations at sea, observations on land have not been alluded to; but in order that thedata accumulated may possess that value which is essential for carryingon the inquiry in reference to atmospheric waves with success, provisionis made to mark out more distinctly the barometric effects of thejunction of large masses of land and water. It is well known that theoceanic surface, and even the smaller surfaces of inland seas, producedecided inflexions of the isothermal lines. They exercise an importantinfluence on temperature. It has also been shown that the neighbourhoodof water has a very considerable influence in increasing theoscillations of the mercurial column in the barometer, and in the greatsystems of European undulations it is well known that these oscillationsincrease especially towards the north-west. The converse of this, however, has not yet been subjected to observation; there has been nosystematic co-operation of observers for the purpose of determining thebarometric affections of large masses of water, such as the centralportion of the basin of the northern Atlantic, the portion of oceanicsurface between the Cape of Good Hope and Cape Horn, the Indian andSouthern oceans, and the vast basin of the Pacific. Nor are we yetacquainted with the character of the oscillations, whether increasing ordecreasing, as we recede from the central portions of the oceanicsurfaces we have mentioned towards the land which forms their eastern, western, or northern boundaries. This influence of the junction line ofland and water, so far as it is yet known, has been kept in view inframing these instructions, and, as it appears so prominently in Europe, it is hoped the additional observations between the four daily readingsto which probably many observers may habitually restrict themselves, making on certain occasions and in particular localities a series ofobservations at intervals of three hours, will not be considered toofrequent when the great importance of the problem to be solved is fullyapprehended. It need scarcely be said that the value of theseobservations at three-hourly intervals will be greatly increased by thenumber of observers co-operating in them. Upon such an extensive systemof co-operation a large space on the earth's surface, possessingpeculiarities which distinguish it from others extremely unlike it intheir general character, or assimilate it to such as possess with itmany features in common, is marked out below for particular observation, occupying more than two-thirds of a zone in the northern hemisphere, having a breadth of 40°, and including every possible variety ofterrestrial and aqueous surface, from the burning sands of the greatAfrican desert, situated about the centre, to the narrow strip of landconnecting the two Americas on the one side, and the chain of islandsconnecting China and Hindostan with Australia on the other. On each sideof the African continent we have spaces of open sea between 30° and 40°west longitude north of the equator, and between 60° and 80° eastlongitude, in or to the south of the equator, admirably suited forcontrasting the barometric affections, as manifested in these spaces ofopen water, with those occurring in situations where the influence ofthe terrestrial surface comes into more active operation. 

The localities where three-hourly readings are chiefly desirable may bespecified under the heads of _Northern Atlantic, Southern Atlantic, Indian_ and _Southern Oceans, _ and _Pacific Ocean_. 

_Northern Atlantic. Homeward-bound Voyages. _--The discussion ofobservations made in the United Kingdom and the western border ofcentral Europe, has indicated that off the north-west of Scotland acentre of great barometric disturbance exists. This centre ofdisturbance appears to be considerably removed from the usual tracks ofvessels crossing the Atlantic; nevertheless some light may be thrown onthe barometric phænomena resulting from this disturbance by observationsduring homeward-bound voyages, especially after the vessels have passedthe meridian of 50° west longitude. Voyagers to or from Baffin andHudson bays would do well during the whole of the voyage to read off thebarometer every three hours, as their tracks would approach nearest thecentre of disturbance in question. Before crossing the 50th meridian, the undulations arising from the distribution of land and water in theneighbourhood of these vast inland seas would receive considerableelucidation from the shorter intervals of observation, and after passingthe 50th meridian the extent of undulation, as compared with thatobserved by the more southerly vessels, would be more distinctly markedby the three-hourly series. Surveying vessels stationed on thenorth-western coasts of Ireland and Scotland may contribute mostimportant information on this head by a regular and, as far ascircumstances will allow, an uninterrupted series either of six-hourlyor three-hourly observations. The intervals of observation on boardvessels stationed at the Western Isles, the Orkneys, and the ShetlandIsles, ought not to be longer than _three_ hours, principally on accountof the great extent of oscillation observed in those localities. Vesselsarriving from all parts of the world as they approach the United Kingdomshould observe at shorter intervals than six hours. As a generalinstruction on this head the series of three-hourly observations may becommenced on board vessels from America and the Pacific by the way ofCape Horn on their passing the 20th meridian, such three-hourlyobservations to be continued until the arrival of the vessels in port. Ships by the way of the Cape of Good Hope should commence thethree-hourly series either on leaving or passing the colony, in orderthat the phænomena of the tropical depression hereafter to be noticedmay be well observed. 

_Northern Atlantic. Outward-bound Voyages_. --Vessels sailing to theUnited States, Mexico, and the West Indies, should observe at threehours' interval upon passing the 60th meridian. Observations at thisinterval, on board vessels navigating the Gulf of Mexico and theCaribbean Sea, will be particularly valuable in determining the extentof oscillation as influenced by the masses of land and water in thisportion of the torrid zone, as compared with the oscillation noticed offthe western coast of Africa, hereafter to be referred to. 

_Southern Atlantic. Outward and homeward bound_. --Without doubt the mostinteresting phænomenon, and one that lies at the root of the greatatmospheric movements, especially those proceeding northwards in thenorthern hemisphere and southwards in the southern, is the equatorialdepression first noticed by Von Humboldt and confirmed by many observerssince. We shall find the general expression of this most importantmeteorological fact in the Report of the Committee of Physics andMeteorology, appointed by the Royal Society in 1840, as follows: "Thebarometer, at the level of the sea, does not indicate a mean atmosphericpressure of equal amount in all parts of the earth; but, on thecontrary, the equatorial pressure is uniformly less in its mean amountthan at and beyond the tropics. " Vessels that are outward bound should, upon passing 40° north latitude, commence the series of three-hourlyobservations, with an especial reference to the equatorial depression. These three-hourly observations should be continued until the latitudeof 40° south has been passed: the whole series will then include theminimum of the depression and the two maxima or apices forming itsboundaries. (See Daniell's 'Meteorological Essays, ' 3rd edition. ) Inpassages across the equator, should the ships be delayed by calms, opportunities should be embraced for observing this depression withgreater precision by means of _hourly_ readings; and these readings willnot only be valuable as respects the depression here spoken of, but willgo far to indicate the character of any disturbance that may arise, andpoint out, as nearly as such observations will allow, the precise timewhen such disturbance produced its effects in the neighbourhood of theships. In point of fact they will clearly illustrate the diversion ofthe tendency to rise, spoken of in the Report before alluded to, asresulting in ascending columns and sheets, between which wind flaws, capricious in their direction and intensity, and often amounting tosharp squalls, mark out the course of their feeders and the indraft ofcooler air from a distance to supply their void. Hourly observations, with especial reference to this and the following head of inquiry, should also be made off the western coast of Africa during thehomeward-bound voyage. 

Immediately connected with this part of the outward-bound voyage, hourlyobservations, as often as circumstances will permit, while the ships aresailing from the Madeiras to the equator, will be extremely valuable inelucidating the origin of the great system of south-westerly atmosphericwaves that traverse Europe, and in furnishing data for comparison withthe amount of oscillation and other barometric phænomena in the Gulf ofMexico and the Caribbean Sea, a portion of the torrid zone essentiallydifferent in its configuration and in the relations of its area to landand water, as contra-distinguished to the northern portion of theAfrican continent; and these hourly observations are the more desirableas the vessels may approach the land. They may be discontinued onpassing the equator, and the three-hourly series resumed. 

There are two points in the southern hemisphere, between 80° westlongitude and 30° east longitude, that claim particular attention in abarometric point of view, viz. , Cape Horn and the Cape of Good Hope; thelatter is within the area marked out for the three-hourly observations, and too much attention cannot be paid to the indications of thebarometer as vessels are approaching or leaving the Cape. The northernpart of the South Atlantic Ocean has been termed the _true Pacific Oceanof the world_; and at St. Helena a gale was scarcely ever known; it isalso said to be entirely free from actual storms (Col. Reid's 'Law ofStorms, ' 1st edition, p. 415). It may therefore be expected that thebarometer will present in this locality but a small oscillation, andships in sailing from St. Helena to the Cape will do well to ascertain, by means of the three-hourly observations, the increase of oscillationas they approach the Cape. The same thing will hold good with regard toCape Horn: it appears from previous observation that a permanentbarometric depression exists in this locality, most probably in some wayconnected with the immense depression noticed by Captain Sir James ClarkRoss, towards the Antarctic Circle. The general character of theatmosphere off Cape Horn is also extremely different from its characterat St. Helena. It would therefore be well for vessels sailing into thePacific by Cape Horn, to continue the three-hourly observations untilthe 90th meridian is passed. 

Before quitting the Atlantic Ocean it may be well to notice the marinestations mentioned in my Third Report on Atmospheric Waves, [5] as beingparticularly suitable for testing the views advanced in that report andfor tracing a wave of the south-westerly system from the most westernpoint of Africa to the extreme north of Europe. A series of hourlyobservations off the western coast of Africa has already been suggested. Vessels staying at Cape Verd Islands should not omit to makeobservations at three hours' interval _during the whole of their stay_, and when circumstances will allow, hourly readings. At the Canaries, Madeiras, and the Azores, similar observations should be made. Vesselstouching at Cape Cantin, Tangier, Gibraltar, Cadiz, Lisbon, Oporto, Corunna, and Brest, should also make these observations while they arein the localities of these ports. At the Scilly Isles we have six-hourlyobservations, made under the superintendence of the Honourable theCorporation of the Trinity House. Ships in nearing these islands andmaking the observations already pointed out, will greatly assist indetermining the increase of oscillation proceeding westward from thenodal point of the two great European systems. We have already mentionedthe service surveying vessels employed on the coasts of Ireland andScotland may render, and the remaining portion of the area marked out inthe report may be occupied by vessels navigating the North Sea and thecoast of Norway, as far as Hammerfest. 

In connexion with these observations, having especial reference to theEuropean system of south-westerly atmospheric waves, the Mediterraneanpresents a surface of considerable interest, both as regards theseparticular waves, and the influence its waters exert in modifying thetwo great systems of central Europe. The late Professor Daniell hasshown from the Manheim observations, that small undulations, havingtheir origin on the northern borders of the Mediterranean, havepropagated themselves northward, and in this manner, but in a smallerdegree, the waters of the Mediterranean have contributed to increase theoscillation as well as the larger surface of the northern Atlantic. Inmost of the localities of this great inland sea six-hourly observationsmay suffice for this immediate purpose; but in sailing from Lisbonthrough the Straits of Gibraltar, in the neighbourhood of Sicily andItaly, and in the Grecian Archipelago, we should recommend thethree-hourly series, as marking more distinctly the effects resultingfrom the proximity of land; this remark has especial reference to thepassage through the Straits of Gibraltar, where, if possible, hourlyobservations should be made. 

_The Indian and Southern Oceans. Outward and homeward bound. _--Onsailing from the Cape of Good Hope to the East Indies, China, orAustralia, observations at intervals of three hours should be made untilthe 40th meridian east is passed (homeward-bound vessels should commencethe three-hourly readings on arriving at this meridian). Upon leavingthe 40th meridian the six-hourly observations may be resumed on boardvessels bound for the Indies and China until they arrive at the equator, when the readings should again be made at intervals of three hours, andcontinued until the arrival of the vessels in port. With regard tovessels bound for Australia and New Zealand, the six-hourly readings maybe continued from the 40th to the 100th meridian, and upon the vesselspassing the latter, the three-hourly readings should be commenced andcontinued until the vessels arrive in port. Vessels navigating theArchipelago between China and New Zealand, should make observationsevery three hours, in order that the undulations arising from theconfiguration of the terrestrial and oceanic surfaces may be moredistinctly marked and more advantageously compared with the Gulf ofMexico, the Caribbean Sea, and the northern portion of the Africancontinent. 

_The Pacific Ocean. _--As this ocean presents so vast an aqueous surface, generally speaking observations at intervals of six hours will be amplysufficient to ascertain its leading barometric phænomena. Vessels, however, on approaching the continents of North and South America, orsailing across the equator, should resort to the three-hourly readings, in order to ascertain more distinctly the effect of the neighbourhood ofland on the oscillations of the barometer, as generally observed, overso immense a surface of water in the one case, and the phænomena of theequatorial depression in the other: the same remarks relative to thelatter subject, which we offered under the head of South Atlantic, willequally apply in the present instance. The configuration of the westernshores of North America renders it difficult to determine the preciseboundary where the three-hourly series should commence; the 90thmeridian is recommended for the boundary as regards South America, andfrom this a judgment may be formed as to where the three-hourlyobservations should commence in reference to North America. 

In the previous sketch of the localities for the more importantobservations, it will be seen that within the tropics there are threewhich demand the greatest regard. 

I. The Archipelago between the two Americas, more particularly comprisedwithin the 40th and 120th meridians west longitude, and the equator andthe 40th degree of north latitude. As a general principle we should saythat vessels within this area should observe the barometer every threehours. Its eastern portion includes the lower branches of the stormpaths, and on this account is peculiarly interesting, especially in abarometric point of view. 

II. _The Northern portion of the African Continent, including the Saharaor Great Desert. _--This vast radiating surface must exert considerableinfluence on the waters on each side northern Africa. Vessels sailingwithin the area comprised between 40° west and 70° east, and the equatorand the 40th parallel, should also make observations at intervals ofthree hours. 

III. _The great Eastern Archipelago. _--This presents a somewhat similarcharacter to the western; like that, it is the region of terrifichurricanes, and it becomes a most interesting object to determine itsbarometric phænomena; the three-hourly system of observation maytherefore be resorted to within an area comprised between the 70th and140th meridians, and the equator and the 40th degree of north latitude. 

The southern hemisphere also presents three important localities, theprolongations of the three tropical areas. It is unnecessary to enlargeupon these, as ample instructions have been already given. We may, however, remark, with regard to Australia, that three-hourlyobservations should be made within the area comprised between the 100thand 190th meridians east, and the equator and the 50th parallel south, and hourly ones in the immediate neighbourhood of all its coasts. 

IV. --STORMS, HURRICANES, AND TYPHOONS. 

The solution of the question--How far and in what manner are stormsconnected with atmospheric waves?--must be extremely interesting toevery one engaged in either the naval or merchant service. As we have inthe former chapters directed attention to their connexion, our greatobject here will be to endeavour to mark out such a line of observationas appears most capable of throwing light, not only on the mostimportant desiderata as connected with storms, but also their connexionor non-connexion with atmospheric waves. We shall accordinglyarrange this portion of the instructions under the followingheads:--_Desiderata_; _Localities_; _Margins_; _Preceding and SucceedingAccumulations of Pressure. _

_Desiderata. _--The most important desiderata appertaining to the subjectof storms, are certainly their origin and termination. Of these initialand terminal points in the course of great storms we absolutely knownothing, unless _the white appearance of a round form_ observed by Mr. Seymour on board the Judith and Esther, in lat. 17° 19' north and long. 52° 10' west (see Col. Reid's 'Law of Storms, ' 1st edit. P. 65), may beregarded as the commencement of the Antigua hurricane of August 2, 1837. This vessel was the most eastern of those from which observations hadbeen obtained; and it is the absence of contemporaneous observations tothe eastward of the 50th meridian that leaves the question as to theorigin of the West Indian revolving storms unsolved. Not one of Mr. Redfield's storm routes extends eastward of the 50th meridian; this atonce marks out, so far as storms are concerned, the entire spaceincluded between the 20th and 50th meridians, the equator and the 60thparallel, as a most suitable area for observations, under particularcircumstances hereafter to be noticed, with especial reference either tothe commencement or termination of storms, or the prolongation of Mr. Redfield's storm paths. 

_Localities. _--The three principal localities of storms are asfollows:--I. The western portion of the basin of the North Atlantic; II. The China Sea and Bay of Bengal; and III. The Indian Ocean, moreparticularly in the neighbourhood of Mauritius. The first two havealready been marked out as areas for the three-hourly observations; tothe latter, the remark as to extra observations under the head ofDesiderata will apply. 

_Margins. _--Mr. Redfield has shown that on some occasions storms havebeen preceded by an unusual pressure of the atmosphere; the barometerhas stood remarkably _high_, and it has hence been inferred that therehas existed _around_ the gale an accumulation of air forming a margin;barometers placed under this margin indicating a much greater pressurethan the mean of the respective localities. With regard to the WestIndian and American hurricanes--any considerable increase of pressure, especially within the space marked out to the eastward of the 50thmeridian, will demand immediate attention. Upon the barometer ranging_very high_ within this space, three-hourly observations should beimmediately resorted to; and if possible, _hourly_ readings taken, andthis is the more important the nearer the vessel may be to the 50thmeridian. Each observation of the barometer should be accompanied by anobservation of the wind--its direction should be most carefully noted, and the force estimated according to the scale in page 21, or by theanemometer. It would be as well _at the time_ to project the barometricreadings in a curve even of a rough character, that the extent of fallafter the mercury had passed its maximum might be readily discernible bythe eye. A paper ruled in squares, the vertical lines representing thecommencement of hours, and the horizontal tenths of an inch, would bequite sufficient for this purpose. The _force_ of the wind should benoted at, or as near to the time of the passage of the maximum aspossible. During the fall of the mercury particular attention should bepaid to the manner in which the wind changes, should any change beobserved; and should the wind continue blowing steadily in _one_direction, but gradually _increasing_ in force, then such increments offorce should be most carefully noted. During the fall of the barometer, should the changes of the wind and its increasing force indicate theneighbourhood of a revolving storm, (independent of the obvious reasonsfor avoiding the focus of the storm, ) it would contribute as much toincrease our knowledge of these dangerous vortices to keep as near aspossible to their margins as to approach their centres. The recess fromthe centre towards the margin of the storm, will probably be renderedapparent by the _rising_ of the mercury; and so far as the observationsmay be considered valuable for elucidating the connexion of atmosphericwaves with rotatory storms (other motives being balanced), it might bedesirable to keep the ship near the margin--provided she is not carriedbeyond the influence of the winds which characterize the latter half ofthe storm--until the barometer has nearly attained its usual elevation. By this means some notion might be formed of the general direction ofthe line of barometric pressure preceding or succeeding a storm. 

Should a gale be observed commencing without its having been preceded byan unusual elevation of the mercurial column, and consequently noadditional observation have been made; when the force of the wind isnoted in the usual observations at or above 5, then the three-hourlyseries should be resorted to, and the same care taken in noting thedirection, changes, and force of the wind as pointed out in thepreceding paragraph. 

The foregoing remarks relate especially to the central and westernportions of the North Atlantic; they will however equally apply to theremaining localities of storms. Under any circumstances, and in anylocality, a _high_ barometer not less than a low one should demandparticular attention, and if possible, _hourly_ readings taken some timebefore and after the passage of the maximum: this will be referred tomore particularly under the next head. 

_Preceding and Succeeding Accumulations of Pressure. _--Mr. Redfield hasshown in his Memoir of the Cuba Hurricane of October, 1844, that twoassociated storms were immediately preceded by a barometric wave, oraccumulation of pressure, the barometer rising above the usual or annualmean. We have just referred to the importance of _hourly_ observationson occasions of the readings being _high_ as capable of illustrating themarginal phænomena of storms, and in connexion with these accumulationsof pressure in advance of storms we would reiterate the suggestion. These strips of accumulated pressure are doubtless crests of atmosphericwaves rolling forwards. In some cases a ship in its progress may cutthem transversely in a direction at right angles to their _length_, inothers very obliquely; but in all cases, whatever section may be givenby the curve representing the observations, too much attention cannot bebestowed on the barometer, the wet and dry bulb thermometer, thedirection and force of the wind, the state of the sky, and theappearance of the ocean during the ship's passage _through_ such anaccumulation of pressure. When the barometer attains its mean altitude, and is rapidly rising above it in any locality, then _hourly_observations of the instruments and phænomena above noticed should becommenced and continued until after the mercury had attained its highestpoint and had sunk again to its mean state. In such observationsparticular attention should be paid to the direction and force of thewind preceding the barometric maximum--and the same phænomena succeedingit, and particular notice should be taken of the time when, and amountof any change either in the direction or force of the wind. It is bysuch observations as these, carried on with great care and made at everyaccessible portion of the oceanic surface, that we may be able toascertain the continuity of these atmospheric waves, to determinesomewhat respecting their length, to show the character of theirconnexion with the rotatory storm, and to deduce the direction and rateof their progress. 

V. --SEASONS FOR EXTRA OBSERVATIONS. 

In reference to certain desiderata that have presented themselves in thecourse of my researches on this subject (see Report of the BritishAssociation for the Advancement of Science, 1846, p. 163), the _phases_of the larger barometric undulations, and the _types_ of the variousseasons of the year, demand particular attention and call for extraobservations at certain seasons: of these, three only have yet beenascertained--the type for the middle of November--the annual depressionon or about the 28th of November--and the annual elevation on or aboutthe 25th of December. The enunciation of the first is as under: "Thatduring fourteen days in November, more or less equally disposed aboutthe middle of the month, the oscillations of the barometer exhibit aremarkably symmetrical character, that is to say, the fall succeedingthe transit of the maximum or the highest reading is to a great extentsimilar to the preceding rise. This rise and fall is not continuous orunbroken; in some cases it consists of _five_, in others of _three_distinct elevations. The complete rise and fall has been termed thegreat symmetrical barometric wave of November. At its setting in thebarometer is generally low, sometimes below twenty-nine inches. Thisdepression is generally succeeded by _two_ well-marked undulations, varying from one to two days in duration. The central undulation, whichalso forms the apex of the great wave, is of larger extent, occupyingfrom three to five days; when this has passed, two smaller undulationscorresponding to those at the commencement of the wave make theirappearance, and at the close of the last the wave terminates. " With butslight exceptions, the observations of eight successive years haveconfirmed the general correctness of this type. On two occasions thecentral apex has not been the highest, and these deviations, with someof a minor character, form the exceptions alluded to. This type only hasreference to London and the south-eastern parts of England; proceedingwestward, north-westward, and northward, the symmetrical character ofthis type is considerably departed from; each locality possessing itsown type of the barometric movements during November. The desiderata inimmediate connexion with the November movements, as observed in thesouthern and south-eastern parts of England, that present themselves, are--the determination of the types for November, especially its middleportion, as exhibited on the oceanic surface within an area comprisedbetween the 30th and 60th parallels, and the 1st and 40th meridianswest. Vessels sailing within this area may contribute greatly to thedetermination of these types by making observations at intervals ofthree hours from the 1st of November to the 7th or 8th of December. Theentire period of the great symmetrical wave of November will mostprobably be embraced by such a series of observations, as well as theannual depression of the 28th. For the elevation of the 25th of Decemberthe three-hourly observations should be commenced on the 21st, andcontinued until the 3rd or 4th of the succeeding January. 

With respect to the great wave of November, our knowledge of it would bemuch increased by such a series of observations as mentioned above, being made on board surveying and other vessels employed off Scotlandand Ireland; vessels navigating the North Sea; vessels stationed off thecoasts of France, Spain, Portugal, and the northern parts of Africa, andat all our stations in the Mediterranean. In this way the area ofexamination would be greatly enlarged, and the _differences_ of thecurves more fully elucidated; and this extended area of observation isthe more desirable, as there is some reason to believe that the line ofgreatest symmetry _revolves_ around a fixed point, most probably thenodal point of the great European systems. 

It is highly probable that movements of a somewhat similar character, although presenting very different curves, exist in the southernhemisphere. The November wave is more or less associated with storms. Ithas been generally preceded by a high barometer and succeeded by a lowone, and this low state of the barometer has been accompanied by stormyweather. We are therefore prepared to seek for similar phænomena in thesouthern hemisphere, in those localities which present similar states ofweather, and at seasons when such weather predominates. We have alreadymarked out the two capes in the Southern hemisphere for three-hourlyobservations: they must doubtless possess very peculiar barometriccharacters, stretching as they do into the vast area of the SouthernOcean. It is highly probable that the oscillations, especially at someseasons, are very considerable, and vessels visiting them at suchseasons would do well to record with especial care the indications ofthe instruments already alluded to. At present we know but little of thebarometric movements in the Southern hemisphere, and every addition toour knowledge in this respect will open the way to more importantconclusions. 

It has been observed in the south-east of England that the barometer hasgenerally passed a maximum on or about the 3rd of every month, and thishas been so frequently the case as to form the rule rather than theexception. The same fact during a more limited period has been observedat Toronto. With especial reference to this subject the three-hourlyseries of observations may be resorted to in all localities, butespecially north of the 40th parallel in the northern hemisphere. Theyshould be commenced at midnight immediately preceding the 1st andcontinued to midnight succeeding the 5th. 

CHAPTER IV. 

PRACTICAL DIRECTIONS FOR AVOIDING THE CENTRES OF ROTATINGSTORMS. 

Figures 1 and 2, enlarged and printed on narrow rings of stiffcardboard, are employed for this purpose. The letters outside the thickcircle are intended to distinguish the points of the compass, and in useshould always coincide with those points on the chart. The letterswithin the thick circle indicate the direction of the wind in ahurricane, the whirl being shown by the arrows between the letters. Inthe northern hemisphere the direction of the whirl is always contrary tothat in which the hands of a watch move, and in the southern coincidentthereto. The graduation is intended to assist the mariner inascertaining the bearing of the centre of a storm from his ship. 

_Use. _

At any time when a severe gale or hurricane is expected, the seamanshould at once find the position of his ship on the chart, and placeupon it the graduated point which answers to the direction of the windat the time, taking care that the needle is directed to the north, sothat the exterior letters may point on the chart to the respectivepoints of the compass: this is very essential. This simple process willat once acquaint the seaman with two important facts relative to thecoming hurricane--his position in the storm, and the direction inwhich it is moving. 

_Examples. _

A captain of a ship in latitude 35° 24' N. , longitude 64° 12' W. , boundto the United States, observes the barometer to stand unusually high, say 30·55 inches: shortly after the mercury begins to fall, at firstslowly and steadily; as the glass falls the wind freshens, and isnoticed to blow with increasing force from the S. So as to threaten agale. The position of the ship on the chart is now to be found, and thegraduated point under the letters E. S. Is to be placed thereon, taking care to direct the needle to the north. From these twocircumstances, the falling barometer and the wind blowing from the southwith increasing force, the mariner is aware of this simple fact, that heis situated in the advancing portion of a body of air which isproceeding towards the N. E. ; and if he turn his face to the N. E. He willfind he is on the right of the axis line, or line cutting the advancingbody transversely. The hurricane circle as it lies on the chart revealsto him another important fact, which is, that if he pursue his course hewill sail _towards_ the axis line of the hurricane, and may stand achance of foundering in its centre. To avoid this he has one of twocourses to adopt; either to lay-to on the _starboard tack_, according toCol. Reid's rules (see his 'Law of Storms, ' 1st edit. , pp. 425 to 428), the ship being in the right-hand semicircle of the hurricane, or so toalter his course as to keep without the influence of the storm. In thepresent case the adoption of the latter alternative would involve areversal of his former course; nevertheless it is clear the more hebears to the S. E. The less he will experience the violence of thehurricane: should he heave his ship to, upon moving the hurricane circlefrom the ship's place on the chart towards the N. E. , he will be able tojudge of the changes of the wind he is likely to experience: thus itwill first veer to S. S. W. , the barometer still falling; then to S. W. , the barometer at a minimum--this marks the position of the most violentportion of the storm he may be in, and by keeping the barometer as highas he can by bearing towards the S. E. , the farther he will be from thecentre--the barometer now begins to rise, the wind veering to W. S. W. , and the hurricane finally passes off with the wind at W. It is to beparticularly remarked that in this example the ship is in the _mostdangerous quadrant_, as by scudding she would be driven in advance ofthe track of the storm's centre, which of course would be approachingher. 

Assuming that the hurricane sets in at the ship's place with the wind atS. E. , the proceeding will be altogether different. At first the wind isfair for the prosecution of the voyage, and it is desirable to takeadvantage of this fair wind to avoid as much as possible the track ofthe centre, which passes over the ship's place in this instance, and isalways the most dangerous part of the storm. As the ship is able to makegood distance from this track by bearing towards the N. W. , provided shehas plenty of sea-room, she will experience less of the violence of thehurricane; but as most of the Atlantic storms sweep over the shore, itwill be desirable to lay-to at some point on the _larboard tack_, theship being now in the left-hand semicircle. By moving the circle asbefore directed it will be seen that the veering of the wind is nowE. S. E. , E. , E. N. E. , N. E. , the lowest barometer N. N. E. , N. , and N. N. W. , the ship experiencing more or less of these changes as it is nearer toor farther from the axis line. 

In latitudes lower than 20° N. The Atlantic hurricanes usually movetowards the N. W. Taking the same positions of our ship with regard tothe storms as in the two former examples, if the storm set in with thewind E. The proper proceeding is to bear away for the N. E. , the mostdangerous quadrant of the hurricane having overtaken the ship, theveering of the wind if she is lying-to will be E. , E. S. E. , S. E. , withthe lowest barometer S. S. E. And S. Should the storm set in at N. E. , herposition at the time will be some indication of the distance of thecentre's track from the nearest land, and will greatly assist indetermining the point at which the captain ought to lay-to after takingadvantage of the N. E. Wind, should he be able so to do, to bear awayfrom the centre line, so as to avoid as much as possible the violence ofthe storm. From the proximity of the West Indian Islands to thislocality of the storm-paths, the danger is proportionally increased. 

The above examples have reference only to the lower and upper branchesof the storm paths of the Northern Atlantic in the neighbourhood of theWest Indies and the United States. In latitudes from about 25° to 32°these paths usually _re-curve_, and at some point will move towards thenorth. The veering of the wind will consequently be more or lesscomplicated according as the ship may be nearer to or farther from thecentre. The tables on page 11, combined with the first of thoseimmediately following the next paragraph, will, it is hoped, proveadvantageous in assisting the mariner as to the course to be adopted. Asa general principle we should say it would be best to bear to theeastward, so as not only to avoid the greater fury of the storm, but toget into the S. And S. W. Winds, which give the principal chances ofmaking a westerly course. 

We have in page 44 called attention to the fact that the storm pathstraced by Mr. Redfield do not extend eastward of the 50th meridian. Thisby no means precludes the existence of severe storms and those of arotatory character in the great basin of the Northern Atlantic, especially between the 40th and 50th parallels. A remarkable instancehas come under the author's attention of the wind hauling _apparently_contrary to the usual theory: it may be that the storm route was in adirection not generally observed. We are at the present moment destituteof any information that at all indicates a _reversion_ of the rotationin either hemisphere. The following tables constructed for the northernhemisphere, and for storm routes _not yet ascertained_, may probably beconsulted with advantage on anomalous occasions. 

HURRICANE MOVING FROM SOUTH TO NORTH. 

 Axis line, wind E. , barometer falling, first half of storm. Axis line, wind W. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind E. S. E. , S. E. , S. S. E. , S. , barometer falling, first half of storm. Wind W. S. W. , S. W. , S. S. W. , S. , barometer rising, last half of storm. 

LEFT-HAND SEMICIRCLE. 

 Wind E. N. E. , N. E. , N. N. E. , N. , barometer falling, first half of storm. Wind W. N. W. , N. W. , N. N. W. , N. , barometer rising, last half of storm. 

HURRICANE MOVING FROM NORTH TO SOUTH. 

 Axis line, wind W. , barometer falling, first half of storm. Axis line, wind E. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind W. N. W. , N. W. , N. N. W. , N. , barometer falling, first half of storm. Wind E. N. E. , N. E. , N. N. E. , N. , barometer rising, last half of storm. 

LEFT-HAND SEMICIRCLE. 

 Wind W. S. W. , S. W. , S. S. W. , S. , barometer falling, first half of storm. Wind E. S. E. , S. E. , S. S. E. , S, , barometer rising, last half of storm. 

HURRICANE MOVING PROM WEST TO EAST. 

 Axis line, wind S. , barometer falling, first half of storm. Axis line, wind N. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind S. S. W. , S. W. , W. S. W. , W. , barometer falling, first half of storm. Wind N. N. W. , N. W. , W. N. W. , W. , barometer rising, last half of storm. 

LEFT-HAND SEMICIRCLE. 

 Wind S. S. E. , S. E. , E. S. E. , E. , barometer falling, first half of storm. Wind N. N. E. , N. E. , E. N. E. , E. , barometer rising, last half of storm. 

HURRICANE MOVING FROM NORTH-WEST TO SOUTH-EAST. 

 Axis line, wind S. W. , barometer falling, first half of storm. Axis line, wind N. E. , barometer rising, last half of storm. 

RIGHT-HAND SEMICIRCLE. 

 Wind W. S. W. , W. , W. N. W. , N. W. , barometer falling, first half of storm. Wind N. N. E. , N. , N. N. W. , N. W. , barometer rising, last half of storm. 

LEFT-HAND SEMICIRCLE. 

 Wind S. S. W. , S. , S. S. E. , S. E. , barometer falling, first half of storm. Wind E. N. E. , E. , E. S. E. , S. E. , barometer rising, last half of storm. 

APPENDIX. 

TABLE I. --Correction to be added to Barometers for Capillary Action. 

 +--------------------+---------------------------------+ | | Correction for | | Diameter of Tube. |-----------------+---------------| | | Unboiled Tubes. | Boiled Tubes. | |--------------------|-----------------|---------------| | Inch. | Inch. | Inch. | | 0·60 | 0·004 | 0·002 | | 0·50 | 0·007 | 0·003 | | 0·45 | 0·010 | 0·005 | | 0·40 | 0·014 | 0·007 | | 0·35 | 0·020 | 0·010 | | 0·30 | 0·028 | 0·014 | | 0·25 | 0·040 | 0·020 | | 0·20 | 0·060 | 0·029 | | 0·15 | 0·088 | 0·044 | | 0·10 | 0·142 | 0·070 | +--------------------+-----------------+---------------+

+---------------------------------------------------------------------+|Transcibers note: The following 100 line table has been split into ||two, both vertically and horizontally, so that it can be accommodated||on these pages. |+---------------------------------------------------------------------+

TABLE II. --Correction to be applied to Barometers with _Brass Scales_, extending from the Cistern to the top of the Mercurial Column, to reducethe observation to 32° Fahrenheit. 

 ---+------------------------------------------------------------+---- | I N C H E S. | T | -----+-------+------+-------+------+-------+------+--------| T e | | | | | | | | | e m | 24 | 24·5 | 25 | 25·5 | 26 | 26·5 | 27 | 27·5 | m p | | | | | | | | | p ---+------+-------+------+-------+------+-------+------+--------+---- ° | + | + | + | + | + | + | + | + | ° 0 | ·061 | ·063 | ·064 | ·065 | ·067 | ·068 | ·069 | ·071 | 0 1 | ·059 | ·061 | ·062 | ·063 | ·064 | ·065 | ·067 | ·068 | 1 2 | ·057 | ·058 | ·060 | ·061 | ·062 | ·063 | ·064 | ·066 | 2 3 | ·055 | ·056 | ·057 | ·059 | ·060 | ·061 | ·062 | ·063 | 3 4 | ·053 | ·054 | ·055 | ·056 | ·057 | ·058 | ·059 | ·061 | 4 5 | ·051 | ·052 | ·053 | ·054 | ·055 | ·056 | ·057 | ·058 | 5 6 | ·049 | ·050 | ·051 | ·052 | ·053 | ·054 | ·055 | ·056 | 6 7 | ·046 | ·047 | ·048 | ·049 | ·050 | ·051 | ·052 | ·053 | 7 8 | ·044 | ·045 | ·046 | ·047 | ·048 | ·049 | ·050 | ·051 | 8 9 | ·042 | ·043 | ·044 | ·045 | ·046 | ·046 | ·047 | ·048 | 9 10 | ·040 | ·041 | ·042 | ·042 | ·043 | ·044 | ·045 | ·046 | 10 | | | | | | | | | 11 | ·038 | ·039 | ·039 | ·040 | ·041 | ·042 | ·042 | ·043 | 11 12 | ·036 | ·036 | ·037 | ·038 | ·039 | ·039 | ·040 | ·041 | 12 13 | ·033 | ·034 | ·035 | ·036 | ·036 | ·037 | ·038 | ·038 | 13 14 | ·031 | ·032 | ·033 | ·033 | ·034 | ·035 | ·035 | ·036 | 14 15 | ·029 | ·030 | ·030 | ·031 | ·032 | ·032 | ·033 | ·033 | 15 16 | ·027 | ·028 | ·028 | ·029 | ·029 | ·030 | ·030 | ·031 | 16 17 | ·025 | ·025 | ·026 | ·026 | ·027 | ·027 | ·028 | ·028 | 17 18 | ·023 | ·023 | ·024 | ·024 | ·025 | ·025 | ·025 | ·026 | 18 19 | ·021 | ·021 | ·021 | ·022 | ·022 | ·023 | ·023 | ·024 | 19 20 | ·018 | ·019 | ·019 | ·020 | ·020 | ·020 | ·021 | ·021 | 20 | | | | | | | | | 21 | ·016 | ·017 | ·017 | ·017 | ·018 | ·018 | ·018 | ·019 | 21 22 | ·014 | ·014 | ·015 | ·015 | ·015 | ·016 | ·016 | ·016 | 22 23 | ·012 | ·012 | ·012 | ·013 | ·013 | ·013 | ·013 | ·014 | 23 24 | ·010 | ·010 | ·010 | ·010 | ·011 | ·011 | ·011 | ·011 | 24 25 | ·008 | ·008 | ·008 | ·008 | ·008 | ·008 | ·009 | ·009 | 25 26 | ·005 | ·006 | ·006 | ·006 | ·006 | ·006 | ·006 | ·006 | 26 27 | ·003 | ·003 | ·003 | ·003 | ·004 | ·004 | ·004 | ·004 | 27 28 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | 28 | -- | -- | -- | -- | -- | -- | -- | -- | 29 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | 29 30 | ·003 | ·003 | ·003 | ·004 | ·004 | ·004 | ·004 | ·004 | 30 | | | | | | | | | 31 | ·005 | ·006 | ·006 | ·006 | ·006 | ·006 | ·006 | ·006 | 31 32 | ·008 | ·008 | ·008 | ·008 | ·008 | ·008 | ·008 | ·009 | 32 33 | ·010 | ·010 | ·010 | ·010 | ·011 | ·011 | ·011 | ·011 | 33 34 | ·012 | ·012 | ·012 | ·013 | ·013 | ·013 | ·013 | ·014 | 34 35 | ·014 | ·014 | ·015 | ·015 | ·015 | ·015 | ·016 | ·016 | 35 36 | ·016 | ·017 | ·017 | ·017 | ·017 | ·018 | ·018 | ·019 | 36 37 | ·018 | ·019 | ·019 | ·019 | ·020 | ·020 | ·021 | ·021 | 37 38 | ·020 | ·021 | ·021 | ·022 | ·022 | ·023 | ·023 | ·023 | 38 39 | ·023 | ·023 | ·024 | ·024 | ·024 | ·025 | ·025 | ·026 | 39 40 | ·025 | ·025 | ·026 | ·026 | ·027 | ·027 | ·028 | ·028 | 40 | | | | | | | | | 41 | ·027 | ·027 | ·028 | ·029 | ·029 | ·030 | ·030 | ·031 | 41 42 | ·029 | ·030 | ·030 | ·031 | ·031 | ·032 | ·033 | ·033 | 42 43 | ·031 | ·032 | ·032 | ·033 | ·034 | ·034 | ·035 | ·036 | 43 44 | ·033 | ·034 | ·035 | ·035 | ·036 | ·037 | ·037 | ·038 | 44 45 | ·035 | ·036 | ·037 | ·038 | ·038 | ·039 | ·040 | ·041 | 45 46 | ·038 | ·038 | ·039 | ·040 | ·041 | ·042 | ·042 | ·043 | 46 47 | ·040 | ·041 | ·041 | ·042 | ·043 | ·044 | ·045 | ·046 | 47 48 | ·042 | ·043 | ·044 | ·045 | ·045 | ·046 | ·047 | ·048 | 48 49 | ·044 | ·045 | ·046 | ·047 | ·043 | ·049 | ·050 | ·050 | 49 50 | ·046 | ·047 | ·043 | ·049 | ·050 | ·051 | ·052 | ·053 | 50 ---+------+-------+------+-------+------+-------+------+--------+----

 ---+-----------------------------------------------------+---- | I N C H E S. | T |-------+------+-------+------+-------+------+--------| T e | | | | | | | | e m | 28 | 28·5 | 29 | 29·5 | 30 | 30·5 | 31 | m p | | | | | | | | p ---+-------+------+-------+------+-------+------+--------+---- ° | + | + | + | + | + | + | + | ° 0 | ·072 | ·073 | ·074 | ·076 | ·077 | ·078 | ·080 | 0 1 | ·069 | ·071 | ·072 | ·073 | ·074 | ·076 | ·077 | 1 2 | ·067 | ·068 | ·069 | ·070 | ·072 | ·073 | ·074 | 2 3 | ·064 | ·065 | ·067 | ·068 | ·069 | ·070 | ·071 | 3 4 | ·062 | ·063 | ·064 | ·065 | ·066 | ·067 | ·068 | 4 5 | ·039 | ·060 | ·061 | ·062 | ·063 | ·065 | ·066 | 5 6 | ·057 | ·058 | ·059 | ·060 | ·061 | ·062 | ·063 | 6 7 | ·054 | ·055 | ·056 | ·057 | ·058 | ·059 | ·060 | 7 8 | ·052 | ·053 | ·054 | ·054 | ·055 | ·056 | ·057 | 8 9 | ·049 | ·050 | ·051 | ·052 | ·053 | ·054 | ·054 | 9 10 | ·047 | ·047 | ·048 | ·049 | ·050 | ·051 | ·052 | 10 | | | | | | | | 11 | ·044 | ·045 | ·046 | ·046 | ·047 | ·048 | ·049 | 11 12 | ·042 | ·042 | ·043 | ·044 | ·045 | ·045 | ·046 | 12 13 | ·039 | ·040 | ·040 | ·041 | ·042 | ·043 | ·043 | 13 14 | ·037 | ·037 | ·038 | ·038 | ·039 | ·040 | ·040 | 14 15 | ·034 | ·035 | ·035 | ·036 | ·036 | ·037 | ·038 | 15 16 | ·032 | ·032 | ·033 | ·033 | ·034 | ·034 | ·035 | 16 17 | ·029 | ·030 | ·030 | ·031 | ·031 | ·032 | ·032 | 17 18 | ·026 | ·027 | ·027 | ·028 | ·028 | ·029 | ·029 | 18 19 | ·024 | ·024 | ·025 | ·025 | ·026 | ·026 | ·027 | 19 20 | ·021 | ·022 | ·022 | ·023 | ·023 | ·023 | ·024 | 20 | | | | | | | | 21 | ·019 | ·019 | ·020 | ·020 | ·020 | ·021 | ·021 | 21 22 | ·016 | ·017 | ·017 | ·017 | ·018 | ·018 | ·018 | 22 23 | ·014 | ·014 | ·014 | ·015 | ·015 | ·015 | ·015 | 23 24 | ·011 | ·012 | ·012 | ·012 | ·012 | ·012 | ·013 | 24 25 | ·009 | ·009 | ·009 | ·009 | ·009 | ·010 | ·010 | 25 26 | ·006 | ·006 | ·007 | ·007 | ·007 | ·007 | ·007 | 26 27 | ·004 | ·004 | ·004 | ·004 | ·004 | ·004 | ·004 | 27 28 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | 28 | -- | -- | -- | -- | -- | -- | -- | 29 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | ·001 | 29 30 | ·004 | ·004 | ·004 | ·004 | ·004 | ·004 | ·004 | 30 | | | | | | | | 31 | ·006 | ·006 | ·007 | ·007 | ·007 | ·007 | ·007 | 31 32 | ·009 | ·009 | ·009 | ·009 | ·009 | ·010 | ·010 | 32 33 | ·011 | ·012 | ·012 | ·012 | ·012 | ·012 | ·012 | 33 34 | ·014 | ·014 | ·014 | ·015 | ·015 | ·015 | ·015 | 34 35 | ·016 | ·017 | ·017 | ·017 | ·018 | ·018 | ·018 | 35 36 | ·019 | ·019 | ·020 | ·020 | ·020 | ·021 | ·021 | 36 37 | ·021 | ·022 | ·022 | ·022 | ·023 | ·023 | ·024 | 37 38 | ·024 | ·024 | ·025 | ·025 | ·026 | ·026 | ·026 | 38 39 | ·026 | ·027 | ·027 | ·028 | ·028 | ·029 | ·029 | 39 40 | ·029 | ·029 | ·030 | ·030 | ·031 | ·031 | ·032 | 40 | | | | | | | | 41 | ·031 | ·032 | ·033 | ·033 | ·034 | ·034 | ·035 | 41 42 | ·034 | ·034 | ·035 | ·036 | ·036 | ·037 | ·037 | 42 43 | ·036 | ·037 | ·038 | ·038 | ·039 | ·010 | ·040 | 43 44 | ·039 | ·040 | ·040 | ·041 | ·042 | ·042 | ·043 | 44 45 | ·041 | ·042 | ·043 | ·044 | ·044 | ·045 | ·046 | 45 46 | ·044 | ·045 | ·045 | ·046 | ·047 | ·048 | ·049 | 46 47 | ·046 | ·047 | ·048 | ·049 | ·050 | ·051 | ·051 | 47 48 | ·049 | ·050 | ·051 | ·052 | ·052 | ·053 | ·054 | 48 49 | ·031 | ·052 | ·053 | ·054 | ·055 | ·056 | ·057 | 49 50 | ·054 | ·055 | ·056 | ·057 | ·058 | ·059 | ·060 | 50 ---+-------+------+-------+------+-------+------+--------+----

TABLE II. --_Continued_

 ----+------------------------------------------------------------+----- | I N C H E S. | T |------+-------+------+-------+------+-------+------+--------| T e | | | | | | | | | e m | 24 | 24·5 | 25 | 25·5 | 26 | 26·5 | 27 | 27·5 | m p | | | | | | | | | p ----+------+-------+------+-------+------+-------+------+--------+----- ° | + | + | + | + | + | + | + | + | ° 51 | ·048 | ·049 | ·050 | ·051 | ·052 | ·053 | ·054 | ·055 | 51 52 | ·050 | ·052 | ·053 | ·054 | ·055 | ·056 | ·057 | ·058 | 52 53 | ·053 | ·054 | ·055 | ·056 | ·057 | ·058 | ·059 | ·060 | 53 54 | ·055 | ·056 | ·057 | ·053 | ·059 | ·060 | ·062 | ·063 | 54 55 | ·057 | ·058 | ·059 | ·060 | ·062 | ·063 | ·064 | ·065 | 55 56 | ·059 | ·060 | ·061 | ·063 | ·064 | ·065 | ·066 | ·063 | 56 57 | ·061 | ·062 | ·064 | ·065 | ·066 | ·068 | ·069 | ·070 | 57 58 | ·063 | ·065 | ·066 | ·067 | ·069 | ·070 | ·071 | ·073 | 58 59 | ·065 | ·067 | ·068 | ·070 | ·071 | ·072 | ·074 | ·075 | 59 60 | ·068 | ·069 | ·070 | ·072 | ·073 | ·075 | ·076 | ·077 | 60 | | | | | | | | | 61 | ·070 | ·071 | ·073 | ·074 | ·075 | ·077 | ·078 | ·080 | 61 62 | ·072 | ·073 | ·075 | ·076 | ·078 | ·079 | ·081 | ·082 | 62 63 | ·074 | ·076 | ·077 | ·079 | ·080 | ·082 | ·083 | ·085 | 63 64 | ·076 | ·073 | ·079 | ·081 | ·082 | ·084 | ·086 | ·087 | 64 65 | ·078 | ·080 | ·082 | ·083 | ·085 | ·086 | ·088 | ·090 | 65 66 | ·080 | ·082 | ·084 | ·085 | ·087 | ·089 | ·090 | ·092 | 66 67 | ·083 | ·084 | ·086 | ·088 | ·089 | ·091 | ·093 | ·095 | 67 68 | ·085 | ·086 | ·088 | ·090 | ·092 | ·094 | ·095 | ·097 | 68 69 | ·087 | ·089 | ·090 | ·092 | ·094 | ·096 | ·098 | ·100 | 69 70 | ·089 | ·091 | ·093 | ·095 | ·096 | ·098 | ·100 | ·102 | 70 | | | | | | | | | 71 | ·091 | ·093 | ·095 | ·097 | ·099 | ·101 | ·102 | ·104 | 71 72 | ·093 | ·095 | ·097 | ·099 | ·101 | ·103 | ·105 | ·107 | 72 73 | ·095 | ·097 | ·099 | ·101 | ·103 | ·105 | ·107 | ·109 | 73 74 | ·097 | ·099 | ·102 | ·104 | ·106 | ·108 | ·110 | ·112 | 74 75 | ·100 | ·102 | ·104 | ·106 | ·108 | ·110 | ·112 | ·114 | 75 76 | ·102 | ·104 | ·106 | ·108 | ·110 | ·112 | ·114 | ·117 | 76 77 | ·104 | ·106 | ·108 | ·110 | ·112 | ·115 | ·117 | ·119 | 77 78 | ·106 | ·108 | ·110 | ·113 | ·115 | ·117 | ·119 | ·122 | 78 79 | ·108 | ·110 | ·113 | ·115 | ·117 | ·119 | ·122 | ·124 | 79 80 | ·110 | ·113 | ·115 | ·117 | ·119 | ·122 | ·124 | ·126 | 80 | | | | | | | | | 81 | ·112 | ·115 | ·117 | ·119 | ·122 | ·124 | ·126 | ·129 | 81 82 | ·114 | ·117 | ·119 | ·122 | ·124 | ·126 | ·129 | ·131 | 82 83 | ·117 | ·119 | ·121 | ·124 | ·126 | ·129 | ·131 | ·134 | 83 84 | ·119 | ·121 | ·124 | ·126 | ·129 | ·131 | ·134 | ·136 | 84 85 | ·121 | ·123 | ·136 | ·128 | ·131 | ·133 | ·136 | ·139 | 85 86 | ·123 | ·126 | ·128 | ·131 | ·133 | ·136 | ·138 | ·141 | 86 87 | ·125 | ·128 | ·130 | ·133 | ·136 | ·138 | ·141 | ·143 | 87 88 | ·127 | ·130 | ·133 | ·133 | ·138 | ·141 | ·143 | ·146 | 88 89 | ·129 | ·132 | ·135 | ·137 | ·140 | ·143 | ·146 | ·148 | 89 90 | ·131 | ·134 | ·137 | ·140 | ·142 | ·145 | ·148 | ·151 | 90 | | | | | | | | | 91 | ·134 | ·136 | ·139 | ·142 | ·145 | ·148 | ·150 | ·153 | 91 92 | ·136 | ·139 | ·141 | ·144 | ·147 | ·150 | ·153 | ·156 | 92 93 | ·138 | ·141 | ·144 | ·147 | ·149 | ·152 | ·155 | ·158 | 93 94 | ·140 | ·143 | ·146 | ·149 | ·152 | ·155 | ·157 | ·161 | 94 95 | ·142 | ·145 | ·148 | ·151 | ·154 | ·157 | ·160 | ·163 | 95 96 | ·144 | ·147 | ·150 | ·153 | ·156 | ·159 | ·162 | ·165 | 96 97 | ·146 | ·149 | ·152 | ·155 | ·159 | ·162 | ·165 | ·168 | 97 98 | ·148 | ·152 | ·155 | ·158 | ·161 | ·164 | ·167 | ·170 | 98 99 | ·151 | ·154 | ·157 | ·160 | ·163 | ·166 | ·169 | ·173 | 99 100 | ·153 | ·156 | ·159 | ·162 | ·165 | ·169 | ·172 | ·175 | 100 ----+------+-------+------+-------+------+-------+------+--------+-----

 ----+-----------------------------------------------------+----- | I N C H E S. | T |-------+------+-------+------+-------+------+--------| T e | | | | | | | | e m | 28 | 28·5 | 29 | 29·5 | 30 | 30·5 | 31 | m p | | | | | | | | p ----+-------+------+-------+------+-------+------+--------+----- ° | + | + | + | + | + | + | + | ° 51 | ·056 | ·057 | ·058 | ·059 | ·060 | ·061 | ·062 | 51 52 | ·059 | ·060 | ·061 | ·062 | ·063 | ·064 | ·065 | 52 53 | ·061 | ·063 | ·064 | ·065 | ·066 | ·067 | ·068 | 53 54 | ·064 | ·065 | ·066 | ·067 | ·068 | ·070 | ·071 | 54 55 | ·066 | ·068 | ·069 | ·070 | ·071 | ·072 | ·073 | 55 56 | ·069 | ·070 | ·071 | ·073 | ·074 | ·075 | ·076 | 56 57 | ·071 | ·073 | ·074 | ·075 | ·076 | ·078 | ·079 | 57 58 | ·074 | ·075 | ·077 | ·078 | ·079 | ·081 | ·082 | 58 59 | ·076 | ·078 | ·079 | ·080 | ·082 | ·083 | ·085 | 59 60 | ·079 | ·080 | ·082 | ·083 | ·085 | ·086 | ·087 | 60 | | | | | | | | 61 | ·081 | ·083 | ·084 | ·086 | ·087 | ·089 | ·090 | 61 62 | ·084 | ·085 | ·087 | ·088 | ·090 | ·091 | ·093 | 62 63 | ·086 | ·088 | ·089 | ·091 | ·093 | ·094 | ·096 | 63 64 | ·089 | ·090 | ·092 | ·094 | ·095 | ·097 | ·098 | 64 65 | ·091 | ·093 | ·095 | ·096 | ·098 | ·100 | ·101 | 65 66 | ·094 | ·096 | ·097 | ·099 | ·101 | ·102 | ·104 | 66 67 | ·096 | ·098 | ·100 | ·102 | ·103 | ·105 | ·107 | 67 68 | ·099 | ·101 | ·102 | ·104 | ·106 | ·108 | ·109 | 68 69 | ·101 | ·103 | ·105 | ·107 | ·109 | ·110 | ·112 | 69 70 | ·104 | ·106 | ·108 | ·109 | ·111 | ·113 | ·115 | 70 | | | | | | | | 71 | ·106 | ·108 | ·110 | ·112 | ·114 | ·116 | ·118 | 71 72 | ·109 | ·111 | ·113 | ·115 | ·117 | ·119 | ·120 | 72 73 | ·111 | ·113 | ·115 | ·117 | ·119 | ·121 | ·123 | 73 74 | ·114 | ·116 | ·118 | ·120 | ·122 | ·124 | ·126 | 74 75 | ·116 | ·118 | ·120 | ·122 | ·125 | ·127 | ·129 | 75 76 | ·119 | ·121 | ·123 | ·125 | ·127 | ·129 | ·131 | 76 77 | ·121 | ·123 | ·126 | ·128 | ·130 | ·132 | ·134 | 77 78 | ·124 | ·126 | ·128 | ·130 | ·133 | ·135 | ·137 | 78 79 | ·126 | ·128 | ·131 | ·133 | ·135 | ·137 | ·140 | 79 80 | ·129 | ·131 | ·133 | ·136 | ·138 | ·140 | ·143 | 80 | | | | | | | | 81 | ·131 | ·134 | ·136 | ·138 | ·141 | ·143 | ·145 | 81 82 | ·134 | ·136 | ·138 | ·141 | ·143 | ·146 | ·148 | 82 83 | ·136 | ·139 | ·141 | ·143 | ·146 | ·148 | ·151 | 83 84 | ·139 | ·141 | ·144 | ·146 | ·149 | ·151 | ·154 | 84 85 | ·141 | ·144 | ·146 | ·149 | ·151 | ·154 | ·156 | 85 86 | ·144 | ·146 | ·149 | ·151 | ·154 | ·156 | ·159 | 86 87 | ·146 | ·149 | ·151 | ·154 | ·157 | ·159 | ·162 | 87 88 | ·149 | ·151 | ·154 | ·157 | ·159 | ·162 | ·165 | 88 89 | ·151 | ·154 | ·156 | ·159 | ·162 | ·165 | ·167 | 89 90 | ·153 | ·156 | ·159 | ·162 | ·164 | ·167 | ·170 | 90 | | | | | | | | 91 | ·156 | ·159 | ·162 | ·165 | ·167 | ·170 | ·173 | 91 92 | ·158 | ·161 | ·164 | ·167 | ·170 | ·172 | ·175 | 92 93 | ·161 | ·164 | ·167 | ·170 | ·172 | ·175 | ·178 | 93 94 | ·163 | ·166 | ·169 | ·172 | ·175 | ·177 | ·180 | 94 95 | ·166 | ·169 | ·172 | ·175 | ·178 | ·180 | ·183 | 95 96 | ·168 | ·171 | ·174 | ·178 | ·181 | ·183 | ·116 | 96 97 | ·171 | ·174 | ·177 | ·180 | ·183 | ·186 | ·189 | 97 98 | ·173 | ·176 | ·179 | ·183 | ·186 | ·188 | ·191 | 98 99 | ·176 | ·179 | ·182 | ·185 | ·188 | ·191 | ·194 | 99 100 | ·178 | ·181 | ·184 | ·188 | ·191 | ·194 | ·197 | 100 ----+-------+------+-------+------+-------+------+--------+-----

PRINTED BY W. CLOWES AND SONS, STANFORD STREET. FOOTNOTES:

[1] The first half of the storm, _in the case before alluded to_, isthat N. E. Of the line N. W. --S. E. , fig. 1, comprising the easterly andsoutherly winds; and the latter half, that S. W. Of the same line, comprising the northerly and westerly winds. 

[2] This table is also applicable to the hurricanes in the neighbourhoodof Mauritius in the southern hemisphere, where all the phænomena arereversed; the motion of the hurricanes being towards the S. W. , and therotation in the direction of the hands of a watch, the same barometricand anemonal phænomena are experienced as in a hurricane in the northernhemisphere moving towards the N. E. 

[3] By the officer of the watch being charged with this duty, and itsbeing executed under his immediate superintendence, it is apprehendedthat a register may be kept with great regularity. 

[4] These papers may be obtained from Messrs. W. H. Allen and Co. , Booksellers to the Honourable East India Company, No. 7, LeadenhallStreet, London. 

[5] Reports of the British Association for the Advancement of Science, 1846, p. 139.