I know very well what I am about, & that my skies have not been neglected, though they often failed in execution — and often, no doubt, from an over-… - John Constable

He [the artist in general] 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.

I paint by all the daylight we have and that is little enough, less perhaps than you have by much... imagine to yourself how a purl must look through a burnt glass.

Painting is a science and should be pursued as an inquiry into the laws of nature. Why, then, may not a landscape be considered as a branch of natural philosophy, of which pictures are but experiments?