Thomson, WILLIAM (Lord Kelvin), one of the most brilliant natural philosophers of the 19th century, was born in Belfast in June 1824. At Cambridge he highly distinguished himself as an original thinker even in his undergraduate days. He was second wrangler and first Smith's prizeman of 1845, and shortly after was elected to a fellowship in St Peter's College. In 1846 he became professor of Natural Philosophy in the university of Glasgow, where his father had been professor of mathematics. All his numerous writings have the stamp of originality in a marked degree. Perhaps the most remarkable of his earlier papers, published in 1842, is the one in which he solves by an analogy derived from the conduction of heat important problems in electrostatics. To him also we owe the solution of the problem of the transmission of electric currents in submarine cables. It was in this connection that he first came prominently before the public, for it was largely through his refined researches that the Atlantic cable was so soon a realised idea. On the successful completion of the cable in 1866 he was knighted. In 1892 he was created a peer with the title of Lord Kelvin. As an inventor of accurate and delicate scientific instruments Lord Kelvin is facile princeps. His electrometers of various design—absolute, portable, quadrant, &c.—embody the perfection of mechanical and geometrical adjustment. More recently he has constructed ampere-meters, volt-meters, and watt-meters, suitable alike for the electrical workshop and laboratory. His sounding apparatus and Compass (q.v.) have been adopted by the Admiralty and the principal mercantile lines. In pure science Lord Kelvin has done incomparable work. Specially may be mentioned his thermodynamic researches from 1848 onwards, including the doctrine of the dissipation or degradation of Energy (q.v.); his magnetic and electric discoveries, including general theorems of great value and the beautiful method of electric images, which has proved such a power in all similar investigations; and his work in hydrodynamics, more especially in wave-motion and in vortex-motion. Basing upon the phenomena of gyrostatic motion (see GYROSCOPE) he has imagined a kinetic theory of inertia of high interest; and his dynamical theory of dispersion, and indeed all his views on the nature of the Ether (q.v.) are full of suggestiveness. In 1872 his electrostatic and magnetic papers were reprinted in collected form (2d ed. 1884); and his other papers have been similarly published under the title Mathematical and Physical Papers (vols. i.-iii. 1882-90), besides Popular Lectures (3 vols. 1889-94). He is joint author with Professor Tait of A Treatise on Natural Philosophy (vol. i. 1867; 2d ed. in two parts, 1879), a work which, though never completed, has had an incalculable influence on the progress of physical science. He was president of the British Association (1871), of the Royal Society of London (1890-95), and of the Royal Society of Edinburgh, and is a member of the Institute of France and of the Berlin Academy, and of British, French, Prussian, and other orders. He resigned his professorship after holding it for fifty-three years.
JAMES THOMSON, LL.D., F.R.S., elder brother of Lord Kelvin, succeeded Rankine in 1872 as professor of Engineering in the university of Glasgow. He retired in 1889, and died May 8, 1892. He was an authority on hydraulics, and invented the inward flow vortex turbine. In pure science he is best known as the discoverer of the effect of pressure upon the freezing-point of water. His various papers on elastic fatigue, on under-currents, on trade-winds, and other subjects are all marked by a distinct originality of treatment.