Joule, JAMES PRESCOTT, F.R.S., LL.D.

Joule, JAMES PRESCOTT, F.R.S., LL.D., one of the most distinguished experimental philosophers, was born 24th December 1818 at Salford. In his youth he had the good fortune to have for instructor in science the celebrated Dalton; and he soon showed, by constructing for himself electrical machines and other philosophical instruments, the bent of his genius. His earliest notable experiments were made with reference to electro-magnetic engines; from which he passed to quantitative determinations regarding heat, and the transformation of various forms of Energy (q.v.). He is justly entitled to be considered as the experimental founder of the modern theory of conservation of energy—the grandest generalisation ever made in physical science. In 1878 a civil list pension of £200 was conferred upon him. He died 11th October 1889, at Sale, near Manchester. See Nature (October 1882); his collected papers (published by the Physical Society, 1884-87); and the Memoir by Osborne Reynolds (1893).—The name JOULE has been suggested, and to some extent used, for the unit of work in practical electricity. It is the work done in one second by the ampère or unit current flowing through the ohm or unit resistance, and is therefore, according to Joule's Law (see ELECTRICITY), the heat developed in one second in a conductor having that resistance and carrying that current. It is approximately equal to 10,000,000 ergs; so that 'Joule's Equivalent,' defined as the mechanical equivalent of the heat required to raise the temperature of one gramme of water from 0° C. to 1° C., contains to the same approximation 4·16 joules.