FORBES, JAarss principal of the united college in the university of St. Andrews, a grandson of sir W. Forbes, the banker, was b. at Colinton, near Edinburgh, April 20, 1809. He 'studied in the university of Edinburgh from 1825 until 1830, when he was admitted to the Scottish bar. On the death of sir John Leslie (q.v.), he was appointed, in 1833, to the chair of natural philosophy in the university of Edinburgh, after a contest in which, among other competitors, he was opposed by Dr. (afterwards sh- David) Brewster and Mr. Galloway. In 1842, the institute of France enrolled him among its corresponding members. He was, besides, a member of numerous other scientific societies at home and abroad, received the royal and the Rumford medals from the royal society of London, and two Keith medals from the royal society of Edinburgh, and was u.e.t. of Oxford. In 1860, F. resigned his chair in Edinburgh, to become principal of the united collep in the university of St. Andrews. Among his contribu tions to science are—the polarization of radiant heat by the tourmaline, and also by reflection (1836), and its circular polarization—discoveries forming some of the strongest proofs of the identity of calorific and luminous rays; the unequal polarization of heat from different sources (1844); the refrangibility of heat; the depolarization of heat; etc. This whole series of experimental results is of a very high order of importance.
Ile is, however, best known to the world in general by his researches on the motion of glaciers. See Travels in the Alps (1843); Norway and its Glaciers (1853); Tour of Mont Blanc and Monte Rosa (1835); and Occasional Papers on the Theoril of Glaciers (1859). He was undoubtedly the first to establish the great fact, that glacier ice moves in its channel like a viscous fluid, the middle moving faster than the sides, and the upper portions faster-than the lower. See GLACIERS. In meteorology, F., among other things, improved Wollaston's application of the thermometer to the determination of heights, and verified with great care Fourier's theoretical results concerning the temperature of theground at different depths and in different kinds of aril and rock. F. also contri buted numerous valuable papers to the Transactions -of the Royal Societies of London and Edinburgh, to the Edinburgh Philosophical Journal, and other periodicals. He died Dec. 31, 1838. His Life and Letters, edited by principal Shairp of St. Andrews, prof. Tait of Edinburgh, and Mr. Adams Reilly, the Alpine traveler, was published in London, 1873.