THOMSON, Sir WILLIAM, one of the few very great living mathematicians and natural philosophers, was b. in June, 1824. His father was prof. of mathematics in the uniyer gity of Glasgow. Thomson graduated in 1845, as second wrangler and first Smith's Prizeman at Cambridge, where he was shortly afterward elected to a fellowship in St. Peter's college; and became prof. of natural philosophy in the university of Glasgow in 1846. This appointment lie still holds. While still an undergraduate, he published oeveral valuable papers. He was for some time editor of the Cambridge Mathematical journal, and some of his most brilliant discoveries have appeared in its pages. He has also contributed to the Comptes Rendus, the transactions and proceedings of the royal societies of London and Edinburgh, and various other journals. All his numerous writ ings have the stamp of originality in a marked degree. In the mathematical theories of elasticity, vortex-motion, heat, electricity, and magnetism, he has made remarkable dis coveries; among which we need merely mention the dissipation of energy, the beautiful idea of electric images, and the complete solution of the problem of telegraphing through a submarine cable. Popularly, he is best known by his association with the Atlantic
cable, a gigantic idea, which, but for his investigntions, might, perhaps, not have been realized, or even attempted. On its successful completion, in 1866, lie was knighted. He has invented several excellent and useful instruments for various electrical purposes —such as electrometers and galvanometers; instruments for the determination of electric units in absolute measure, etc. He is a remarkable instance of the combination of the very highest powers of reasoning with the practical skill of the mathematician and en gineer. In conjunction with prof. Tait, he published in 1867 the first volume of an extensive Treatise on Natural Philosophy; and his Papers on Electrostatics and Magnetism (a splendid monument of his genius) were collected and reprinted in 1872.
His elder brother, JAMES, prof. of civil engineering in Glasgow, has made various improvements iu the construction of turbines and other engines (see WATER-POWER); but is best known by his splendid discovery that the freezing-point of water is lowered by pressure; and the glacier-theory lie has founded upon it. See HEAT, ICE, REGELA