Bodies appear visible at greater distances, in proportion as their Colours are in greater quan tities. Hence we see why Faces disappear even at moderate distances, the greatest share of them being possess'd by Shadows, in comparison of which the Lights are very inconsiderable: Thus, every Face becomes obscure at a shorter distance, as the Shadows bear a greater proportion to the Lights: Further, a Face will become so much the darker as it has more White oppos'd, either before or behind it.