Welton, East Yorkshire. He had no issue. He was the author of a useful compendium, 'Guide to the Explosives Act, 1875,' and wrote many valuable official reports. He collaborated with Sir Boverton Redwood in 'Handbook on Petroleum; with Suggestions on the Construction and Use of Mineral Oil Lamps' (1901 ; 2nd edit. 1906); and ' The Petroleum Lamp, its Choice and Use' (1902).

[Private information; 32nd Annual Report, H.M. Inspectors of Explosives; Rise and Progress of the British Explosives Industry, 1909; Arms and Explosives, March 1908; Annual Register, 1908; The Times, 15 and 18 Feb. 1908.]

**THOMSON**, Sir WILLIAM, first Baron Kelvin of Largs (1824–1907), man of science and inventor, born on 26 June 1824 in College Square East, Belfast, was second son and fourth child of James Thomson (1786-1849) [q. v.], professor of mathematics in the Royal Academical Institution of Belfast, by his wife Margaret, eldest daughter of William Gardiner of Glasgow. The elder brother, James (1822-1892) [q. v.], was professor of engineering, first in Belfast, then in Glasgow. When William was six years old his mother died, and the father himself taught the boys, who never went to school. In 1832, when William was eight, his father moved to Glasgow as professor of mathematics in the university there. In 1834, in his eleventh year, William matriculated in the University of Glasgow. He loved in later life to talk of his student days and of his teachers, William Ramsay, Lushington, Thomas Thomson, Meikleham, and John Pringle Nichol. He early made his mark in mathematics and physical science ; and in 1840 won the university medal for a remarkable essay, 'On the Figure of the Earth.' During his fifth year as a student at Glasgow (1839-40) he received a notable impulse toward physics from the lectures of Nichol and of David Thomson, who temporarily took the classes in natural philosophy during the illness of Meikleham. At the same time he systematically studied the ’Mecanique Analytique' of Lagrange, and the 'Mecanique Celeste' of Laplace, and made the acquaintance — a notable event in his career — of Fourier's ' Theorie Analytique de la Chaleur,' reading it through in a fortnight, and studying it during a three months' visit to Germany. The effect of reading Fourier dominated his whole career. During his last year at Glasgow (1840-1) he communicated to the ’Cambridge Mathematical Journal' (ii. May 1841), under the signature 'P.Q.R.,' an original paper 'On Fourier's Expansions of Functions in Trigonometrical Series,' which was a defence of Fourier's deductions against some strictures of Professor Kelland. The paper is headed 'Frankfort, July 1840, and Glasgow, April 1841.'

He left Glasgow after six years without taking his degree ; and on 6 April 1841 entered as a student at Peterhouse, Cambridge, where he speedily made his mark. An undergraduate of seventeen, he handled methods of difficult integration readily and with mastery, and proved his power in a paper entitled ' The Uniform Motion of Heat in Homogeneous Solid Bodies, and its Connection with the Mathematical Theory of Electricity,' published in the 'Cambridge Mathematical Journal,' vol. iii. 1842. In other papers he announced various important theorems, in some of which he found, however, that he had been anticipated by Sturm, Gauss, and George Green [q. v.], all of them master minds in mathematics. At Cambridge he rowed in the college races of 1844, and won the Colquhoun silver sculls. He also helped to found the Cambridge University Musical Society, and in its first concert, and afterwards in others, played the French horn. His love of good music he retained to the end of his life. He read mathematics with William Hopkins [q. V.]. In January 1845 he came out second wrangler in the mathematical tripos, but he beat the senior wrangler, Stephen Parkinson [q. v.], in the severer test of the competition for Smith's prize.

On leaving Cambridge he visited Faraday's laboratory at the Royal Institution in London. Faraday and Fourier were the chief heroes of his youthful enthusiasm. Then he went to Paris University to work in the laboratory of Regnault with a view to acquiring experimental skill. There he spent four months, and there also he made the acquaintance of Biot, Liouville, Sturm, and Foucault. Returning to Cambridge, he was elected fellow of his college in the autumn of 1845, and became a junior mathematical lecturer and editor of the 'Cambridge Mathematical Journal.'

Thomson at twenty-one years had gained experience in three universities — Glasgow, Cambridge, and Paris — had published a dozen original papers, and had thus established for himself a reputation in mathematical physics. In 1846, at twenty-two, he became professor of natural philosophy in Glasgow on the death of Meikle-