John Farey

John Farey Sr. (24 September 1766 – 6 January 1826) was an English geologist and writer best known for Farey sequence, a mathematical construct that is named after him.

Biography Youth and early career Farey was born on 24 September 1766 at Woburn in Bedfordshire to John Farey (1728–1798) and his second wife, Rachel (née Wright) (1732–1804), a Wesleyan Methodist. He was educated at Halifax in Yorkshire, and showed such aptitude in mathematics, drawing and surveying, that he was brought under the notice of John Smeaton (1724–1792).

After his education he moved to London, where he had relatives, and worked there for a number of years, during which time he met and married, Sophia Hubert (1770–1830). While in London they had their first child John Farey Jr. They went on to have eight more children, two of whom died in infancy. One of his children, Marianne Farey, was the mother of Sophie Gengembre Anderson, the noted artist.

Land agent in Woburn and consulting surveyor in London In 1792, Farey was appointed surveyor and land agent His Canals article is the largest in the work, being some 210,000 words. He contributed similarly to the Edinburgh Encyclopedia. Various nineteenth-century biographical sources, including the Dictionary of National Biography, claimed wrongly that he wrote the Rees article on Steam. It was actually written by his son John Farey Jr.

He contributed articles on music to periodicals, as well as around 350 articles on the topic for two encyclopaedias. They concerned the mathematical relationship of note values and musical temperament. He devised a notation which allowed a sound to be expressed by the sum of three small values Σ + f + m. He made great use of the researches of Marmaduke Overend (music theorist and organist) (c1730-1790), whose manuscripts were then in the library of the Royal Institution.

In 1809, Farey met William Martin who had published work on Derbyshire fossils, to investigate whether they could create a joint geological map of Derbyshire. Martin however was too ill to meet a second time and he died the following year.

Articles, a selection John Farey, "canals", "mineralogy", "surveying" in: Rees's Cyclopædia

Publications about Farey and his work