You will observe in drawing that among the shadows some are of undistinguishable gradation and form, as is shown in the 3rd [proposition] which says: Rounded surfaces display as many degrees of light and shade as there are varieties of brightness and darkness reflected from the surrounding objects. 238. OF LIGHT AND SHADE. You who draw from nature, look (carefully) at the extent, the degree, and the form of the lights and shadows on each muscle; and in their position lengthwise observe towards which muscle the axis of the central line is directed. 239. An object which is [so brilliantly illuminated as to be] almost as bright as light will be visible at a greater distance, and of larger apparent size than is natural to objects so remote. The effect of light or dark backgrounds on the apparent size of objects (240-250). 240. A shadow will appear dark in proportion to the brilliancy of the light surrounding it and conversely it will be less conspicuous where it is seen against a darker background. 241. OF ORDINARY PERSPECTIVE. An object of equal breadth and colour throughout, seen against a background of various colours will appear unequal in breadth. And if an object of equal breadth throughout, but of various colours, is seen against a background of uniform colour, that object will appear of various breadth. And the more the colours of the background or of the object seen against the ground vary, the greater will the apparent variations in the breadth be though the objects seen against the ground be of equal breadth [throughout]. 242. A dark object seen against a bright background will appear smaller than it is. A light object will look larger when it is seen against a background darker than itself. 243. OF LIGHT. A luminous body when obscured by a dense atmosphere will appear smaller; as may be seen by the moon or sun veiled by mists. OF LIGHT. Of several luminous bodies of equal size and brilliancy and at an equal distance, that will look the largest which is surrounded by the darkest background. OF LIGHT. I find that any luminous body when seen through a dense and thick mist diminishes in proportion to its distance from the eye. Thus it is with the sun by day, as well as the moon and the other eternal lights by night. And when the air is clear, these luminaries appear larger in proportion as they are farther from the eye. 244. That portion of a body of uniform breadth which is against a lighter background will look narrower [than the rest].