By an infinite number of materials, I mean colours and shades of all kinds and degrees; some notion of which variety may be formed by supposing a piece of white silk by several dippings gradually dyed to a black; and carrying it in like manner through the prime tints of yellow, red, and blue; and then again, by making the like progress through all the mixtures that are to be made of these three original colours. So that when we survey this infinite and immense variety, it is no wonder, that, let the light or objects be situated or changed how they will, oppositions seldom miss; nor that even every incident of shade should sometimes be so completely disposed as to admit of no further beauty, as to composition; and from whence the artist hath by observation taken his principles of imitation, as in the following respect. [Illustration: Fig. 89] Those objects which are intended most to affect the eye, and come forwardest to the view, must have large, strong, and smart oppositions, like the fore-ground in fig. [89 p. II], and what are designed to be thrown further off, must be made still weaker and weaker, as expressed in figures 86, 92, and 93, which receding in order make a kind of gradation of oppositions; to which, and all the other circumstances already described, both for recession, and beauty, nature hath added what is known by the name of aerial perspective; being that interposition of air, which throws a general soft retiring tint over the whole prospect; to be seen in excess at the rising of a fog. All which again receives still more distinctness, as well as a greater degree of variety, when the sun shines bright, and casts broad shadows of one object upon another; which gives the skilful designer such hints for shewing broad and fine oppositions of shades, as give life and spirit to his performances. [Illustration: Figs. 92 and 93] BREADTH of SHADE is a principle that assists in making distinction more conspicuous; thus fig. [87 p. I], is better distinguish'd by its breadth or quantity of shade, and view'd with more ease and pleasure at any distance, than fig. [88 p. I], which hath many, and these but narrow shades between the folds. And for one of the noblest instances of this, let Windsor-castle be viewed at the rising or setting of the sun. [Illustration: Figs. 87 and 88] Let breadth be introduced how it will, it always gives great repose to the eye; as on the contrary, when lights and shades in a composition are scattered about in little spots, the eye is constantly disturbed, and the mind is uneasy, especially if you are eager to understand every object in the composition, as it is painful to the ear when any one is anxious to know what is said in company, where many are talking at the same time.