Chap. CCLXXVIII.—Of the Colour of Lights and Reflexes.
When two lights strike upon an opake body, they can vary only in two ways; either they are equal in strength, or they are not. If they be equal, they may still vary in two other ways, that is, by the equality or inequality of their brightness; they will be equal, if their distance be the same; and unequal, if it be otherwise. The object placed at an equal distance, between two equal lights, in point both of colour and brightness, may still be enlightened by them in two different ways, either equally on each side, or unequally. It will be equally enlightened by them, when the space which remains round the lights shall be equal in colour, in degree of shade, and in brightness. It will be unequally enlightened by them when the spaces happen to be of different degrees of darkness.
Chap. CCLXXIX.—Why reflected Colours seldom partake of the Colour of the Body where they meet.
It happens very seldom that the reflexes are of the same colour with the body from which they proceed, or with that upon which they meet. To exemplify this, let the convex body D F G E be of a yellow colour, and the body B C, which reflects its colour on it, blue; the part of the convex surface which is struck by that reflected light, will take a green tinge, being B C, acted on by the natural light of the air, or the sun.
Chap. CCLXXX.—The Reflexes of Flesh Colours.
The lights upon the flesh colours, which are reflected by the light striking upon another flesh-coloured body, are redder and more lively than any other part of the human figure; and that happens according to the third proposition of the second book [67], which says, the surface of any opake body participates of the colour of the object which reflects the light, in proportion as it is near to or remote from it, and also in proportion to the size of it; because, being large, it prevents the variety of colours in smaller objects round it, from interfering with, and discomposing the principal colour, which is nearer. Nevertheless it does not prevent its participating more of the colour of a small object near it, than of a large one more remote. See the sixth proposition[68] of perspective, which says, that large objects may be situated at such a distance as to appear less than small ones that are near.