THOMSON, JAMES (1822-1892), British physicist and was born in Belfast on Feb. 16, 1822, and, like his younger brother, Lord Kelvin, at an unusually early age began to attend the classes at Glasgow University. He trained for civil engineering but ill-health compelled him to avoid physical exertion. Accordingly, from about 1843, he devoted himself to theoretical work and to mechanical invention. To this period belong his well known researches in thermodynamics (q.v.), which enabled him to predict by the application of Carnot's theorem the variation of the freezing point of a substance with pressure. His results were ex perimentally verified in the physical laboratories of Glasgow uni versity under Lord Kelvin's direction, and were afterwards applied to give the explanation of regelation. In 1861 he extended them in a paper on crystallization and liquefaction as influenced by stresses tending to change of form in the crystals, and in other studies on the change of state he continued Thomas Andrews's work on the continuity of the liquid and gaseous states of matter, con structing a thermodynamic model in three dimensions to show the relations of pressure, volume and temperature for a sub stance like carbonic acid. (See LIQUEFACTION OF GASES.)
In 185o he patented his "vortex water-wheel," and during the next three or four years carried on inquiries into the properties of "whirling fluids," which resulted in improved forms of blowing fans and water-turbines. (See HYDRAULICS.) Settling in Belfast in 1851, he was selected to be the resident engineer to the Belfast water commissioners in 1853, and four years later became pro fessor of civil engineering and surveying in Queen's college, Bel fast. In 1873 he was appointed to the chair of engineering in the university of Glasgow, and retained this position until 1889, when the failure of his eyesight compelled him to resign. He died on May 8, 1892 at Glasgow. His contributions to geological science included studies of the parallel roads of Glen Roy and of the prismatic jointing of basalt, as seen at the Giant's Causeway. In 1876 and later years he studied the origin of windings of rivers.