James Clerk Maxwell was born in Edinburgh, Scotland, on the 13th of November, 1831. His father, John Clerk, belonged to the old family of Clerks of Penicuik near Edinburgh, and he added Maxwell to his name, on succeeding as a younger son to the estate of Middlebie in Dumfriesshire, which had for generations been the home of a Maxwell. Hence it was customary in Scotland to speak of the subject of our lecture as Clerk-Maxwell; but by the world at large the " Clerk " has been dropped; for instance the magnetic unit recently defined in his honor is not denominated a "Clerk " or a " Clerk-Maxwell," but simply a " Maxwell." His father was by profession an advocate, that is, a lawyer entitled to plead before the Supreme Court of Scotland; his practice had never been large and at the date mentioned he had retired to live on his estate. John Clerk-Maxwell was of a family, many members of which were talented, and not a few eccentric; to the latter class he himself belonged. He took an inTable of Contents Portraits of PhysicistsFrontispiece; PAGE; James Clerk Maxwell (1831-1879) 7; A Lecture delivered March 14, 1902; William John Macquorn Rankine (1820-1872) 22; A Lecture delivered March 18, 1902; Peter Guthrie Tait (1831-1901) 38; A Lecture delivered March 22, 1902; Sir William Thomson, First Lord Kelvin (1824-1907) 55; A Lecture delivered March 25, 1902; Charles Babbage (1791-1871) 71; A Lecture delivered April 21, 1903; William Whewell (1794-1866) 84; A Lecture delivered April 23, 1903; Sir George Gabriel Stokes (1819-1903) 94; A Lecture delivered April 28, 1903; Sir George Biddell Airy (1801-1892) 106; A Lecture delivered April 7, 1904; John Couch Adams (1819-1892) 119; A Lecture delivered April 8, 1904; sir John Frederick William Herschel (1792-1871) 131; A Lecture delivered April 11, 1904; Index 143About the Publisher Forgotten Books is a publisher of his