The sky is the 'source of light' in nature, and governs every thing. Even our common observations on the weather of every day, are suggested by them, but it does not occur to us. Their difficulty in painting both as to composition and execution is very great, because, with all their brilliancy and consequence, they ought not to come forward, or be hardly thought about in a picture... I know very well what I am about, and that my skies have not been neglected, though they have often failed in execution, no doubt, from an over-anxiety about them, which will alone destroy that easy appearance which nature always has in all her movements.