Playfair, JOHN

Playfair, JOHN, mathematician and natural philosopher, was born at Benvie manse, near Dundee, March 10, 1748, and studied at St Andrews. In 1773 he succeeded his father as minister of Liff and Benvie. During his leisure hours he still prosecuted his favourite mathematical and geological studies, and communicated to the Royal Society of London two memoirs, On the Arithmetic of Impossible Quantities and Account of the Lithological Survey of Schiehallion. In 1785 he became joint-professor of Mathematics in Edinburgh University, but exchanged his chair for that of Natural Philosophy in 1805. He became a strenuous supporter of the 'Huttonian theory' in geology, and, after publishing in 1802 his Illustrations of the Huttonian Theory of the Earth (see GEOLOGY, Vol. V. p. 148), he made many journeys for the sake of more extensive observations, particularly in 1815, when he visited France, Switzerland, and Italy. He died at Edinburgh, 19th July 1819. Playfair was during the later part of his life secretary to the Royal Society of Edinburgh. From 1804 he was a contributor to the Edinburgh Review and to the Transactions of the Royal Society of Edinburgh, and wrote many important articles for the Encyclopædia Britannica. His separate works are the Elements of Geometry (1795) and Outlines of Natural Philosophy (1812-16).