The shadows of bridges can never be seen on the surface of the water, unless it should have lost its transparent and reflecting quality, and become troubled and muddy; because clear water being polished and smooth on its surface, the image of the bridge is formed in it as in a looking-glass, and reflected in all the points situated between the eye and the bridge at equal angles; and even the air is seen under the arches. These circumstances cannot happen when the water is muddy, because it does not reflect the objects any longer, but receives the shadow of the bridge in the same manner as a dusty road would receive it.
Chap. CCCXLI.—How a Painter ought to put in Practice the Perspective of Colours.
To put in practice that perspective which teaches the alteration, the lessening, and even the entire loss of the very essence of colours, you must take some points in the country at the distance of about sixty-five yards[86] from each other; as trees, men, or some other remarkable objects. In regard to the first tree, you will take a glass, and having fixed that well, and also your eye, draw upon it, with the greatest accuracy, the tree you see through it; then put it a little on one side, and compare it closely with the natural one, and colour it, so that in shape and colour it may resemble the original, and that by shutting one eye they may both appear painted, and at the same distance. The same rule may be applied to the second and third tree at the distance you have fixed. These studies will be very useful if managed with judgment, where they may be wanted in the offscape of a picture. I have observed that the second tree is less by four fifths than the first, at the distance of thirteen yards.
Chap. CCCXLII.—Various Precepts in Painting.
The superficies of any opake body participates of the colour of the transparent medium interposed between the eye and such body, in a greater or less degree, in proportion to the density of such medium and the space it occupies.
The outlines of opake bodies will be less apparent in proportion as those bodies are farther distant from the eye.
That part of the opake body will be the most shaded, or lightest, which is nearest to the body that shades it, or gives it light.
The surface of any opake body participates more or less of the colour of that body which gives it light, in proportion as the latter is more or less remote, or more or less strong.
Objects seen between lights and shadows will appear to have greater relievo than those which are placed wholly in the light, or wholly in shadow.