By close inspection... you will discover the manner of handling the artifices of contrast, glazing, and other expedients, by which good colorists have raised the value of their tints, and by which nature has been so happily imitated.
He who resolves never to ransack any mind but his own, will be soon reduced, from mere barrenness, to the poorest of all imitations; he will be obliged to imitate himself, and to repeat what he has before often repeated.