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 to Francis Russell, 5th Duke of Bedford for his Woburn estates. After the death of the duke, Farey in 1802 moved to London, and, after first contemplating emigrating or taking a farm in the country, he settled there as a consulting surveyor and geologist. That he was enabled to take this step was due largely to his acquaintance with the geologist William Smith, who in 1801 had been employed by the duke of Bedford in works of draining and irrigation. The duke, appreciating Smith's knowledge of the strata, commissioned him in 1802 to explore the margin of the chalk-hills south of Woburn in order to determine the true succession of the strata; and he instructed Farey to accompany him. Farey has remarked that Smith was his Master and Instructor in Mineral Surveying, and his subsequent publications show how well he had profited by the teachings he received. In 1805, he succeeded the agriculturist Arthur Young as Secretary of the Smithfield Club. His surveying work took him all over the country and he was in much demand from landowners wishing to improve their estates, or exploit the minerals they held. His work on economic geology then was of importance in the burgeoning Industrial Revolution by locating new resources of coal and metal ores. Work Writings Farey was a prolific writer, and Professor Hugh Torrens (see references