Playfair, John (1784–1819) Although a mathematician of distinction in his own right, John Playfair is more famous as the advocate of the views of his friend James Hutton. They were members of the Edinburgh intelligentsia at the end of the eighteenth century and Hutton had published his epoch-making, but difficult,
Theory of the Earth (1795). In it he had propounded the principle of constant change and renewal, later known as uniformitarianism. Two years later Hutton died. This revolutionary book was the foundation to which Playfair, who had visited so many geological localities with Hutton, added illustrative examples and a readable gloss, with immediate success. It was a service not only to his old friend but to science itself. Playfair was perfectly capable of adding observations of his own and was a very competent writer and lecturer.
Illustrations of the Huttonian theory of the Earth influenced, among others, William Smith, W. D. Conybeare, and John Phillips.
Among the important points that Playfair emphasized in
Illustrations are two worth noting. The importance of unconformity in the geological cycle was singled out as an indication of profound change and of the dimension of geological time. Fossils were recognized as of organic origin and, with sedimentary features, as clues to depositional environments. Playfair also introduced many words into use in the geological sense for the first time.
A Scot educated at the University of St Andrews, John Playfair was originally to enter the ministry, but showed such ability in mathematics that he took up that discipline and in 1785 became Professor of Mathematics in the University of Edinburgh. He was also a Fellow of the Royal Society of Edinburgh, and friend of many of its most active Fellows. In 1805 he was created Professor of Natural Philosophy.
D. L. Dineley
