1911 Encyclopædia Britannica/Thomson, James (physicist)

From Wikisource
Jump to navigation Jump to search

THOMSON, JAMES (1822–1892), British physicist and engineer, was born in Belfast on the 16th of February 1822, and, like his younger brother, Lord Kelvin, at an unusually early age began to attend the classes at Glasgow University, where his father had been appointed professor of mathematics in 1832. After his graduation he decided to study civil engineering, and for that purpose became a pupil in several engineering offices and works successively; but ill-health obliged him to leave them all, and he had finally to accept the fact that an occupation involving physical exertion was out of the question. Accordingly, from about 1843, he devoted himself to theoretical work and to mechanical invention. To this period belong his well-known researches in thermodynamics, which enabled him to predict by the application of Carnot's theorem that the temperature of the freezing point of substances which expand on solidifying must be lowered by the application of pressure, the reverse being the case with substances which contract on solidification; and he was able to calculate the amount by which a given pressure lowers the freezing-point of water, a substance which expands on solidification. His results were experimentally verified in the physical laboratories of Glasgow University 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, constructing a thermodynamic model in three dimensions to show the relations of pressure, volume and temperature for a substance like carbonic acid. With regard to his inventions, he devised a clever feathering mechanism for the paddles of steamboats when only a boy of sixteen, and later turned his attention to water engines. In 1850 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 professor of civil engineering and surveying in Queen's College, Belfast. Thence he removed in 1873 to Glasgow as successor to Macquorn Rankine in the chair of engineering in the university, and retained this position until 1889, when the failure of his eyesight compelled him to resign. He died on the 8th of May 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 following years he studied the origin of windings of rivers in alluvial plains and made many experiments with the aid of artificial streams; and the currents of atmospheric circulation afforded him the material for the Bakerian lecture of 1892.