John Playfair
John Playfair – Portrait by Henry Raeburn
Born	(1748-03-10)10 March 1748 Angus
Died	20 July 1819(1819-07-20) (aged 71)

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 summarised the work of James Hutton. It was through this book that Hutton's principle of uniformitarianism first reached a wide audience. The idea was later taken up by Charles Lyell and Charles Darwin. Playfair is also remembered for his proposal of an alternative to Euclid's parallel postulate.

• 1802: Illustrations of the Huttonian theory of the Earth.
• 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).

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