Observe decorum in every thing you represent, that is, fitness of action, dress, and situation, according to the dignity or meanness of the subject to be represented. Be careful that a king, for instance, be grave and majestic in his countenance and dress; that the place be well decorated; and that his attendants, or the by-standers, express reverence and admiration, and appear as noble, in dresses suitable to a royal court.
On the contrary, in the representation of a mean subject, let the figures appear low and despicable; those about them with similar countenances, and actions, denoting base and presumptuous minds, and meanly clad. In short, in both cases, the parts must correspond with the general sentiment of the composition.
The motions of old age should not be similar to those of youth; those of a woman to those of a man; nor should the latter be the same as those of a boy.
Chap. CL.—The Character of Figures in Composition.
In general, the painter ought to introduce very few old men, in the ordinary course of historical subjects, and those few separated from young people; because old people are few, and their habits do not agree with those of youth. Where there is no conformity of custom, there can be no intimacy, and, without it, a company is soon separated. But if the subject require an appearance of gravity, a meeting on important business, as a council, for instance, let there be few young men introduced, for youth willingly avoids such meetings.
Chap. CLI.—The Motion of the Muscles, when the Figures are in natural Positions.
A figure, which does not express by its position the sentiments and passions, by which we suppose it animated, will appear to indicate that its muscles are not obedient to its will, and the painter very deficient in judgment. For that reason, a figure is to shew great eagerness and meaning; and its position is to be so well appropriated to that meaning, that it cannot be mistaken, nor made use of for any other.
Chap. CLII.—A Precept in Painting.
The painter ought to notice those quick motions, which men are apt to make without thinking, when impelled by strong and powerful affections of the mind. He ought to take memorandums of them, and sketch them in his pocket-book, in order to make use of them when they may answer his purpose; and then to put a living model in the same position, to see the quality and aspect of the muscles which are in action.