jection; 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