The edges of an object placed in front of the pupil of the eye will be less distinct in proportion as they are closer to the eye. This is shown by the edge of the object _n_ placed in front of the pupil _d_; in looking at this edge the pupil also sees all the space _a c_ which is beyond the edge; and the images the eye receives from that space are mingled with the images of the edge, so that one image confuses the other, and this confusion hinders the pupil from distinguishing the edge. 231. The outlines of objects will be least clear when they are nearest to the eye, and therefore remoter outlines will be clearer. Among objects which are smaller than the pupil of the eye those will be less distinct which are nearer to the eye. On indistinctness at great distances (232-234). 232. Objects near to the eye will appear larger than those at a distance. Objects seen with two eyes will appear rounder than if they are seen with only one. Objects seen between light and shadow will show the most relief. 233. OF PAINTING. Our true perception of an object diminishes in proportion as its size is diminished by distance. 234. PERSPECTIVE. Why objects seen at a distance appear large to the eye and in the image on the vertical plane they appear small. PERSPECTIVE. I ask how far away the eye can discern a non-luminous body, as, for instance, a mountain. It will be very plainly visible if the sun is behind it; and could be seen at a greater or less distance according to the sun's place in the sky. [Footnote: The clue to the solution of this problem (lines 1-3) is given in lines 4-6, No. 232. Objects seen with both eyes appear solid since they are seen from two distinct points of sight separated by the distance between the eyes, but this solidity cannot be represented in a flat drawing. Compare No. 535.] The importance of light and shade in the perspective of disappearance (235-239). 235. An opaque body seen in a line in which the light falls will reveal no prominences to the eye. For instance, let _a_ be the solid body and _c_ the light; _c m_ and _c n_ will be the lines of incidence of the light, that is to say the lines which transmit the light to the object _a_. The eye being at the point _b_, I say that since the light _c_ falls on the whole part _m n_ the portions in relief on that side will all be illuminated. Hence the eye placed at _c_ cannot see any light and shade and, not seeing it, every portion will appear of the same tone, therefore the relief in the prominent or rounded parts will not be visible. 236. OF PAINTING. When you represent in your work shadows which you can only discern with difficulty, and of which you cannot distinguish the edges so that you apprehend them confusedly, you must not make them sharp or definite lest your work should have a wooden effect. 237. OF PAINTING.