that much
light is reflected from the paper to the dark side of your finger, but
very little is reflected from other things to the paper itself in that
chink under your finger.

57. In general, for this reason, a shadow, or, at any rate, the part of
the shadow nearest the object, is darker than the dark side of the
object. I say in general, because a thousand accidents may interfere to
prevent its being so. Take a little bit of glass, as a wine-glass, or
the ink-bottle, and play it about a little on the side of your hand
farthest from the window; you will presently find you are throwing
gleams of light all over the dark side of your hand, and in some
positions of the glass the reflection from it will annihilate the shadow
altogether, and you will see your hand dark on the white paper. Now a
stupid painter would represent, for instance, a drinking-glass beside
the hand of one of his figures, and because he had been taught by rule
that "shadow was darker than the dark side," he would never think of the
reflection from the glass, but paint a dark gray under the hand, just as
if no glass were there. But a great painter would be sure to think of
the true effect, and paint it; and then comes the stupid critic, and
wonders why the hand is so light on its dark side.

58. Thus it is always dangerous to assert anything as a _rule_ in
matters of art; yet it is useful for you to remember that, in a general
way, a shadow is darker than the dark side of the thing that casts it,
supposing the colors otherwise the same; that is to say, when a white
object casts a shadow on a white surface, or a dark object on a dark
surface: the rule will not hold if the colors are different, the shadow
of a black object on a white surface being, of course, not so dark,
usually, as the black thing casting it. The only way to ascertain the
ultimate truth in such matters is to _look_ for it; but, in the
meantime, you will be helped by noticing that the cracks in the stone
are little ravines, on one side of which the light strikes sharply,
while the other is in shade. This dark side usually casts a little
darker shadow at the bottom of the crack; and the general tone of the
stone surface is not so bright as the light bank of the ravine. And,
therefore, if you get the surface of the object of a uniform tint, more
or less indicative of shade, and then scratch out a white spot or
streak in it of any shape; by putting a dark touch beside this white
one, yo