# Dictionary of National Biography, 1885-1900/Playfair, John

​PLAYFAIR, JOHN (1748–1819), mathematician and geologist, born at Benvie, near Dundee, on 10 March 1748, was eldest son of James Playfair, minister of Liff and Benvie, by his wife, Margaret Young. William Playfair [q. v.] was his brother. He was educated at home till the age of fourteen, when he was sent to St. Andrews. He graduated in 1765. In 1766, being only eighteen, he contended for the mathematical chair in the Marischal College, Aberdeen, and came out third in the competition. He then completed his theological course at St. Mary's College, and was licensed by the presbytery as a minister in 1770. In 1769 ​he proceeded to Edinburgh, and in 1772 was an unsuccessful candidate for the professorship of natural philosophy at St. Andrews. The same year, owing to the death of his father, the burden of supporting the family devolved upon him, and he applied to Lord Gray, the patron, for his father's livings of Liff and Benvie, into which, however, on account of legal difficulties, he was not inducted till August 1773. He was elected moderator of synod on 20 April 1774. At Liff he remained till 1782, resigning the living in January 1783 in order to undertake the education of Mr. Ferguson of Raith and his brother, Sir Ronald Ferguson. He was in charge of these pupils till 1787.
In 1785 he became joint professor of mathematics with Dr. Adam Ferguson in the university of Edinburgh, and in 1805 exchanged his mathematical chair for the professorship of natural philosophy in the same university. Playfair vigorously defended in 1806 the appointment of Mr. (afterwards Sir) John Leslie [q. v.] as his successor to the mathematical professorship. After the peace of 1815 Playfair made a long tour through France and Switzerland to Italy, principally with the object of studying their geological and mineralogical features.
Playfair died at Edinburgh on 20 July 1819. He was one of the original members of the Royal Society of Edinburgh, of which he became secretary to the physical class in 1789, and subsequently general secretary. The latter post he held till his death. For some years he assisted in the publication of the society's ‘Transactions.’ He was elected a fellow of the Royal Society in 1807.
Playfair's principal mathematical work was his ‘Elements of Geometry,’ 8vo, Edinburgh, 1795, which attained its eleventh edition in 1859; but the work which will always be most prominently associated with his name is the ‘Illustrations of the Huttonian Theory of the Earth,’ 8vo, Edinburgh, 1802, on which he spent five years. This work is a model of purity of diction, simplicity of style, and clearness of explanation. It not only gave popularity to Hutton's theory, but helped to create the modern science of geology.
His other works include:
* ‘Letter to the Author of the Examination of Professor Stewart's Short Statement of Facts relative to the Election of Professor Leslie,’ 8vo, Edinburgh, 1806.
* ‘Outlines of Natural Philosophy,’ 8vo, Edinburgh, 1812 (2nd edit. of vol. ii. in 1816, and 3rd edit. of vol. i. in 1819).
* ‘Dissertation … exhibiting a General View of the Progress of Mathematical and Physical Science since the Revival of Letters in Europe,’ in Supplement to the 4th, 5th, and 6th editions of the ‘Encyclopædia Britannica,’ 4to, Edinburgh, 1824 (reissued in ‘Encyclopædia Britannica,’ 7th edit. 1842, 8th edit. 1853).
He was also author of seventeen papers (including two written conjointly with others) on mathematics, natural philosophy, and geology in the ‘Philosophical Transactions,’ in the ‘Transactions of the Royal Society of Edinburgh,’ and other scientific publications, as well as of a ‘Biographical Account of J. Hutton’ in the ‘Transactions of the Royal Society of Edinburgh.’ A collected edition of his works, in 4 vols., edited by James G. Playfair, was issued in 1822.
Two portraits of Playfair are in the National Portrait Gallery, Edinburgh, one painted by William Nicholson, R.S.A., the other a bust by Sir Francis Chantrey, which was engraved on wood by George Pearson for Sir Alexander Grant's ‘Story of the University of Edinburgh,’ 1884. A small portrait of him is preserved in the rooms of the Geological Society at Burlington House.
[Memoir prefixed to the Works; Watt's Bibl. Brit.; Royal Soc. Cat.; Brit. Mus. Cat.; Hew Scott's Fasti, pt. vi. pp. 710–11; Cockburn's Memorials, 1856, passim.]
B. B. W.