Leslie, SIR JOHN

Leslie, SIR JOHN, a celebrated natural philosopher, was born at Largo, Fife, 16th April 1766. He studied at St Andrews and Edinburgh universities, and in 1788 became tutor to two young Americans, with whom he proceeded to Virginia and other parts of America, returning to London in 1790. During the next fifteen years he was variously employed in scientific writing or travelling on the continent with pupils, but all the while engaged in experimental research. The fruits of his labours during this period of his career were a translation of Buffon's Natural History of Birds (1793), the invention of a differential thermometer, a hygrometer, and a photometer, and the publication of his important Experimental Inquiry into the Nature and Propagation of Heat (1804). For this latter work the Royal Society awarded Leslie the Rumford medal for scientific research. In 1805 he obtained the chair of Mathematics at Edinburgh, in spite of a good deal of opposition from the clergy, who objected to his approval of Hume's theory of causation. He occupied it for fourteen years, but most of his leisure time was occupied in scientific experiments. In 1810 he invented the process of artificial refrigeration, which has since been put to so many practical uses. In 1819 he was transferred to the chair of Natural Philosophy, where his peculiar talents found their proper sphere. During the next few years he wrote numerous articles and published several works on natural philosophy and mathematics; but his chief claim to the gratitude of the scientific world lies in his useful inventions, such as the pyroscope, atmometer, æthriroscope, and the prominence which he gave to experimental illustration in his university lectures. In 1832 he was created a Knight of the Guelphic Order; on 3d November of the same year he died, at his estate of Coates, in Fife, near his birthplace. See Memoir by Macvey Napier (1838).