en
through it. You will be able thus actually to _match_ the colour of the
stone, at any part of it, by tinting the paper beside the circular
opening. And you will find that this opening never looks quite _black_,
but that all the roundings of the stone are given by subdued greys.[208]

You will probably find, also, that some parts of the stone, or of the
paper it lies on, look luminous through the opening, so that the little
circle then tells as a light spot instead of a dark spot. When this is
so, you cannot imitate it, for you have no means of getting light
brighter than white paper: but by holding the paper more sloped towards
the light, you will find that many parts of the stone, which before
looked light through the hole, then look dark through it; and if you can
place the paper in such a position that every part of the stone looks
slightly dark, the little hole will tell always as a spot of shade, and
if your drawing is put in the same light, you can imitate or match every
gradation. You will be amazed to find, under these circumstances, how
slight the differences of tint are, by which, through infinite delicacy
of gradation, Nature can express form.

If any part of your subject will obstinately show itself as a light
through the hole, that part you need not hope to imitate. Leave it
white, you can do no more.

When you have done the best you can to get the general form, proceed to
finish, by imitating the texture and all the cracks and stains of the
stone as closely as you can; and note, in doing this, that cracks or
fissures of any kind, whether between stones in walls, or in the grain
of timber or rocks, or in any of the thousand other conditions they
present, are never expressible by single black lines, or lines of simple
shadow. A crack must always have its complete system of light and shade,
however small its scale. It is in reality a little _ravine_, with a dark
or shady side, and light or sunny side, and, usually, shadow in the
bottom. This is one of the instances in which it may be as well to
understand the reason of the appearance; it is not often so in drawing,
for the aspects of things are so subtle and confused that they cannot in
general be explained; and in the endeavour to explain some, we are sure
to lose sight of others, while the natural overestimate of the
importance of those on which the attention is fixed, causes us to
exaggerate them, so that merely _scientific_ draughtsmen caricature a