There should always exist a corresponding feeling between the subject and the manner of treating it.
The student should at least make himself acquainted with the leading principles of every variety of art; because, 'that which would be applicable to one style, would, in some measure, be destructive to another.' It matters nothing how low the branch or particular walk he has chosen; for it will acquire quite another accent from his acquaintance with the higher, whose powers of fascination will in time imperceptibly infuse something of their own dignity into his works.
Something of this infusion has come down from the greatness, the grandeur, and severity of the Roman and Florentine schools, through all varieties they have passed, to the modern. To reach this, however, the mind must habituate itself to become quite 'disdainful of vulgar criticism,' before it can well feel a congenial sympathy with these high latitudes, as well as having to unlearn much it has acquired.
There are many excellencies in painting not at all compatible with each other, and that should never occur together—not even to gratify that fastidious disposition that is dissatisfied with every thing short of perfection: lightness would seem to want solidity, while precision will have dryness and hardness. The excellencies of others frequently corrupt ourselves: just as one coat, however well made, will not adapt itself to two persons, any more than their talents will blend with and lessen our defects.
There is no particular style or branch of art, that the student may be in pursuit of, that does not possess some excellence or other—that is not alone, or at all, perhaps, to be found in the great manner of the Roman or Florentine schools of colour: in composition, breadth and arrangement (particularly of light and shade), and masterly treatment of colour, the Flemish and Dutch, as will our own school, furnish sufficient instances.
Light and shade, colour, novelty, variety, contrast, and even simplicity, all become defects in their excess!—the spirit of the rules by which they are regulated is to be more observed than their literal sense. It will generally be found sufficient to preserve this spirit of their laws alone, to which our ideas may be proportioned and accommodated.
Colour, in my opinion, is as useful in composition as lines: a few colours, scientifically woven together, will form agreeable composition of themselves.
Warm and cold colours, with their gradations and contrasts, lights and shadows with theirs, agreeing with and opposing each other, all struggling together (but that struggle unseen—the art concealed!) to the accomplishment of one object—the sweetness of harmony and union of the whole to one end.