John Playfair

John Playfair - Portrait by Sir Henry Raeburn

John Playfair FRSE, FRS (10 March 1748 – 20 July 1819) was a Scottish scientist and mathematician, and a professor of natural philosophy at the University of Edinburgh. He is perhaps best known for his book Illustrations of the Huttonian Theory of the Earth (1802), which summarized the work of James Hutton. It was through this book that Hutton's principle of uniformitarianism, later taken up by Charles Lyell, first reached a wide audience. Playfair also is remembered for his proposal of an alternative to Euclid's parallel postulate.

Early life

Born at Benvie, Angus, Scotland, where his father was parish minister, Playfair was educated at home until the age of fourteen, when he entered the University of St Andrews. In 1766, when only eighteen, he was a candidate for the chair of mathematics in Marischal College (now part of the University of Aberdeen), and, although he was unsuccessful, his claims were admitted to be high.

Six years later he applied for the chair of natural philosophy in his own university, but again without success, and in 1773 he was offered and accepted the benefice of the united parishes of Liff and Benvie, vacant by the death of his father. Playfair continued, however, his mathematical and physical studies, and in 1782 he resigned his charge in order to become the tutor of Ferguson of Raith. By this arrangement, Playfair was able to be frequently in Edinburgh and to cultivate the literary and scientific society for which it was at that time specially distinguished. In particular, he attended the natural history course of John Walker. Through Nevil Maskelyne, whose acquaintance he had first made in the course of the celebrated Schiehallion experiments in 1774, he also gained access to the scientific circles of London. In 1785 when Dugald Stewart succeeded Ferguson in the Edinburgh chair of moral philosophy, Playfair succeeded the former in that of mathematics.

Mature work

Monument to John Playfair on Calton Hill, Edinburgh

In 1795 Playfair published an alternative, more stringent formulation of Euclid's parallel postulate, which is now called Playfair's axiom; though the axiom bears Playfair's name, he did not create it, but credited others, in particular William Ludlam (1718 - 1788), with the prior use of it.

In 1802, Playfair published his celebrated volume entitled Illustrations of the Huttonian Theory of the Earth. The influence exerted by James Hutton on the development of geology is thought to be largely due to its publication. In 1805 Playfair exchanged the chair of mathematics for that of natural philosophy in succession to John Robison, whom also he succeeded as general secretary to the Royal Society of Edinburgh. He took a prominent part, on the liberal side, in the ecclesiastical controversy that arose in connexion with Sir John Leslie's appointment to the post he had vacated, and published a satirical Letter (1806).

Playfair was an opponent of Gottfried Leibniz's vis viva principle, an early version of the conservation of energy. In 1808, he launched an attack on John Smeaton and William Hyde Wollaston's work championing the theory.

Although a wealthy man, Playfair was buried in an unmarked grave in Old Calton Cemetery, on Waterloo Place in Edinburgh. However, the monument to his memory, on Calton Hill, is visible from the spot.

Family

John's brothers were architect James Playfair and engineer William Playfair. His nephew, William Henry Playfair (1790-1857) was an eminent architect in Scotland. His nephew designed the monument to his memory on Calton Hill.

Honours

• Fellow of the Royal Society of Edinburgh
• Fellow of the Royal Society of London, 1807
• Craters on Mars and the Moon were named in his honor.

Critical bibliography

A four-volume collected edition of Playfair's works, with a memoir by James G. Playfair, appeared at Edinburgh in 1822.

His writings include a number of essays contributed to the Edinburgh Review from 1804 onwards, various papers in the Philosophical Transactions of the Royal Society (including his earliest publication, "On the Arithmetic of Impossible Quantities", 1779, and an "Account of the Lithological Survey of Schehallion", 1811) and in the Transactions of the Royal Society of Edinburgh ("On the Causes which Affect the Accuracy of Barometrical Measurements" and others), the articles "Aepinus" and "Physical Astronomy", and a "Dissertation on the Progress of Mathematical and Physical Science since the Revival of Learning in Europe" in the Encyclopædia Britannica (Supplement to fourth, fifth and sixth editions).

His Elements of Geometry first appeared in 1795 and has passed through many editions; his Outlines of Natural Philosophy (2 vols., 1812-1816) consist of the propositions and formulae which were the basis of his class lectures. Playfair's contributions to pure mathematics were not considerable, his papers "On the Arithmetic of Impossible Quantities" and "On the Causes which Affect the Accuracy of Barometrical Measurements", and his Elements of Geometry, all already referred to, being the most important. His lives of Matthew Stewart, Hutton, and Robison, many of his reviews, and above all his "Dissertation" are of the utmost value.

External links

• Dictionary of Scientific Biography
• O'Connor, John J.; Robertson, Edmund F., "John Playfair", MacTutor History of Mathematics archive, University of St Andrews, http://www-history.mcs.st-andrews.ac.uk/Biographies/Playfair.html .
• Significant Scots: John Playfair
• National Portrait Gallery

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.