Page:A Treatise on Painting.djvu/305

 grees of the thin, and three of the thick sort, while D goes through four degrees of the one, and four of the other. This demonstrates, that the gradation of colours is in proportion to their distance from the eye. But this happens only to those colours which are on a level with the eye; as for those which happen to be at unequal elevations, we cannot observe the same rule, because they are in that case situated in different qualities of air, which alter and diminish these colours in various manners.



 

any place where the light diminishes in a gradual proportion till it terminates in total darkness, the colours also will lose themselves and be dissolved in proportion as they recede from the eye.  Rh