The parts that are near in the fore-ground should be finished in a bold determined manner; but those in the distance must be unfinished, and confused in their outlines.
Chap. CCCX.—Of distant Objects.
That part of any object which is nearest to the luminary from which it receives the light, will be the lightest.
The representation of an object in every degree of distance, loses degrees of its strength; that is, in proportion as the object is more remote from the eye it will be less perceivable through the air in its representation.
Chap. CCCXI.—Of Buildings seen in a thick Air.
That part of a building seen through a thick air, will appear less distinct than another part seen through a thinner air. Therefore the eye, N, looking at the tower A D, will see it more confusedly in the lower degrees, but at the same time lighter; and as it ascends to the other degrees it will appear more distinct, but somewhat darker.