He [the artist] ought to have 'these powerful organs of expression' — colour and chiaroscuro — entirely at his command, that he may use them in every possible form, as well as that he may do with the most perfect freedom; therefore, whether he wishes to make the subject of a joyous, solemn, or meditative character, by flinging over it the cheerful aspect which the sun bestows, by a proper disposition of shade, or by the appearances that beautify its arising or its setting, a true "General Effect" should never be lost sight of.

Text for the 'Old Sarum', print in 'English Landscape' 1835/36, as quoted in Leslie Parris and Ian Fleming-Williams, Constable (Tate Gallery Publications, London, 1993), p. 380