below) has traced around 270 papers by him, quadrupling the number given by the Royal Society's Catalogue of Scientific Papers. He wrote on all manner of subjects, ranging from horticulture, geology, meteorology, metrology, currency decimalisation, music and mathematics to pacifism. He was an important contributor to Rees's Cyclopædia with articles on canals, mineralogy, surveying and a number of the scientific and mathematical basis of sound. 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 the 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 MS 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. Farey's best known work is General View of the Agriculture and Minerals of Derbyshire (3 volumes 1811–17) for the Board of Agriculture. In the first of these volumes (1811) he gave an account of the upper part of the British series of strata, and an exposition of the Carboniferous and other strata of Derbyshire. In this work, and in a paper published in the Philosophical Magazine, vol. 51, 1818, p. 173, on 'Mr Smith's Geological Claims stated', he called attention to the importance of the discoveries of William Smith. Farey sequence As well as being remembered by historians of geology, his name is more widely known by the Farey sequence which he noted as a result of his interest in the mathematics of sound (Philosophical Magazine, vol. 47, 1816, pp. 385–386). Farey died in London. Subsequently, Sophia, his widow, offered his geological collection to the British Museum. The museum rejected the collection, and it was dispersed and broken up. Selected publications John Farey, A General