THOMSON, WILLIAM, first. Baron KEL\IN (1824—). An English mathematician and phys icist, born at Belfast. lie graduated in 1845 from Saint Peter's College, Cambridge, and short ly afterwards was elected to a fellowship. He became professor of natural philosophy in the University of Glasgow in 1846, in which position he continued until 1899. While an undergradu ate he published a paper On the Uniform Motion of Heat in Homogeneous Solid Bodies and Its Connection with the Mathematical Theory of Electricity, which was favorably received by sci entists. Ile was for some time editor of the Cambridge ilathematical Journal and was the first editor of the Cambridge and Dublin Mathe matical Journal which succeeded it, some of his most brilliant discoveries having appeared in these journals. He also contributed to the Comptes Rendus, the Transactions and Proceed ings of the Royal Societies of London and Edin burgh, and various other journals. In the mathe matical theories of elasticity, vortex-motion, heat. electricity, and magnetism, he made remarkable discoveries. Lord Kelvin was the electrical en gineer for the Atlantic cables of 1857-58 and 1S65-66, and made many improvements in sig naling apparatus and theoretical observations of the greatest value. He invented the mirror galvanometer used for cable signaling, and then devised the siphon recorder still in use for re ceiving the signals. Tie also studied the proper ties of t-he cable, and his observation that a limit to the speed of operation would early be reached owing to the effect of the statical capacity has been borne out in a half century of practice. Lord Kelvin acted as engineer for several other cable companies and has invented many pieces of electrical apparatus and methods for measure ment. He also developed an improved form of mariners' compass which is free from the mag netic action of the iron of the ship, and a deep sea sounding apparatus, both of which are in widespread use. Lord Kelvin's work in thermo
dynamics is also of the greatest value. It was he who first appreciated the importance of the doctrine of the cons'ervation of energy as enunci ated by Joule and who developed Carnot's work on heat so that it would harmonize with the new theory then being generally accepted. A paper On an Absolute Thermometric Scale con tains much that is now considered fundamental in thermodynamies. Lord Kelvin's many seien tifie papers. contributed to various scientific jour nals, have been collected in book form as follows, Electrostatics and Magnetism, I vol.; Mathe matical and Physical Papers. 3 vols.; and Popu lar Lectures and Addresses, 3 vols. In conjunc tion with Professor P. G. Tait, Lord Kelvin is the author of A Treatise on YaDoral Philosophy. He received many honors from scientific societies. universities and governments, and is a member of the most important academies and learned organizations of Europe an I America. Lord Kel vin visited America in 1884. and after attend ing the meeting of the British Associa tion in Montreal, be visited Baltimore and delivered a course of lectures before the Johns Hopkins University. published under the title Baltimore Lectures. In 1897 he tended the Toronto meeting of the British Association and visited several of the lead ing universities of the United States. He came once more in 1902. For his work in con nection with the Atlantic cable he was knighted in 1866, and in 1892 he was raised to the peer age. Four years later lie celebrated his jubilee as professor of natural philosophy at Glasgow. Lord Kelvin may he said to represent the highest type of physicist, since he eombines the powers of mathe matical with the inventive faculty and manipulative skill of the experimentalist.