4017022A Treatise on Painting — Why Objects which are high, appear darker at a Distance than those which are low, though the Fog be uniform, and of equal ThicknessJohn Francis RigaudLeonardo da Vinci
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Chap. CCCXIX.—Why Objects which are high, appear darker at a Distance than those which are low, though the Fog be uniform, and of equal Thickness.
Amongst objects situated in a fog, thick air, vapour, smoke, or at a distance, the highest will be the most distinctly seen: and amongst objects equal in height, that placed in the darkest fog, will be most confused and dark. As it happens to the eye H,
looking at A B C, three towers of equal height; it sees the top C as low as R, in two degrees of thickness; and the top B, in one degree only; therefore the top C will appear darker than the top of the tower B.
