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.