John Playfair (1748–1819) was a Scottish mathematician and geologist best known for his defence of James Hutton's geological theories. He attended the University of St Andrews, completing his theological studies in 1770. In 1785 he was appointed joint Professor of Mathematics at the University of Edinburgh, and in 1805 he was elected Professor of Natural Philosophy. A Fellow of the Royal Society, he was acquainted with continental scientific developments, and was a prolific writer of scientific articles in the Transactions of the Royal Society of Edinburgh and the Edinburgh Review. This four-volume edition of his works was published in 1822. Volume 1 includes a biography of Playfair, and his Illustrations of the Huttonian Theory of the Earth, which did much to popularise Hutton's ideas.