Chap. CCII.—Of those Parts in Shadows which appear the darkest at a Distance.
The neck, or any other part which is raised straight upwards, and has a projection over it, will be darker than the perpendicular front of that projection; and this projecting part will be lighter, in proportion as it presents a larger surface to the light.
For instance, the recess A receives no light from any part of the sky G K, but B begins to receive the light from the part of the sky H K, and C from G K; and the point D receives the whole of F K. Therefore the chest will be as light as the forehead, nose, and chin. But what I have particularly to recommend, in regard to faces, is, that you observe well those different qualities of shades which are lost at different distances (while there remain only the first and principal spots or strokes of shades, such as those of the sockets of the eyes, and other similar recesses, which are always dark), and at last the whole face becomes obscured; because the greatest lights (being small in proportion to the demi-tints) are lost. The quality, therefore, and quantity of the principal lights and shades are by means of great distance blended together into a general half-tint; and this is the reason why trees and other objects are found to be in appearance darker at some distance than they are in reality, when nearer to the eye. But then the air, which interposes between the objects and the eye, will render them light again by tinging them with azure, rather in the shades than in the lights; for the lights will preserve the truth of the different colours much longer.