On 29 June 1844 whilst in France, Ruskin made his only diary reference to the artistic vision of David Cox:
Yesterday a pleasant ride... my father enjoying it, though weak, and the cloudy day which threatened rain showing all the lines of the pass gorgeously in opposed warm brown and deep blue, Cox colour. ( Evans and Whitehouse, Diaries I, p.294)
Four years earlier, writing from Rome to his friend Edward Clayton, Ruskin had discussed Cox along with other artists and their qualities as drawing masters. He told Clayton:
Cox is a much more agreeable artist than De Wint, and a much simpler one than Harding... his sketches breathe of morning air, and his grass would wet your feet through... His mountains are melting with soft shadows, and his clouds at once so clear and so vaporous, so craggy, and so ethereal, that you expect to see them dissolve before you - But with all this he has neither the truth of De Wint nor the science of Harding ( Works, 1.427).
By 1871 when Lectures on Landscape was delivered Ruskin had turned strongly against the work of David Cox:
David Cox and John Constable represent a form of blunt and untrained faculty which is being very frank and simple, apparently powerful, and needing no thought, intelligence or trouble whatever to observe and being wholly disorderly, slovenly and licentious, and therein meeting with instant sympathy from the disorderly public mind now resentful of every trammel and ignorant of every law - these two men, I say, represent in their intensity the qualities adverse to all accurate science or skill in landscape art; their work being the mere blundering of cleaver peasants, and deserving no name whatever in any school of true practice, but consummately mischievous - first, in its easy satisfaction of the painters' own self-complacencies, and then in the pretence of ability which blinds the public to all the virtue of patience and to all the difficulty of precision. ( Works, 22.58-9)