the smallest pin's head, if one
part of it is not darker than the rest, it is a bad touch; for it is not
merely because the natural fact is so, that your colour should be
gradated; the preciousness and pleasantness of the colour itself depends
more on this than on any other of its qualities, for gradation is to
colours just what curvature is to lines, both being felt to be beautiful
by the pure instinct of every human mind, and both, considered as types,
expressing the law of gradual change and progress in the human soul
itself. What the difference is in mere beauty between a gradated and
ungradated colour, may be seen easily by laying an even tint of
rose-colour on paper, and putting a rose leaf beside it. The victorious
beauty of the rose as compared with other flowers, depends wholly on the
delicacy and quantity of its colour gradations, all other flowers being
either less rich in gradation, not having so many folds of leaf; or less
tender, being patched and veined instead of flushed.

4. But observe, it is not enough in general that colour should be
gradated by being made merely paler or darker at one place than another.
Generally colour _changes_ as it _diminishes_, and is not merely
_darker_ at one spot, but also _purer_ at one spot than anywhere else.
It does not in the least follow that the darkest spot should be the
purest; still less so that the lightest should be the purest. Very often
the two gradations more or less cross each other, one passing in one
direction from paleness to darkness, another in another direction from
purity to dullness, but there will almost always be both of them,
however reconciled; and you must never be satisfied with a piece of
colour until you have got both: that is to say, every piece of blue that
you lay on must be _quite_ blue only at some given spot, nor that a
large spot; and must be gradated from that into less pure blue--greyish
blue, or greenish blue, or purplish blue, over all the rest of the space
it occupies. And this you must do in one of three ways: either, while
the colour is wet, mix it with the colour which is to subdue it, adding
gradually a little more and a little more; or else, when the colour is
quite dry, strike a gradated touch of another colour over it, leaving
only a point of the first tint visible: or else, lay the subduing tints
on in small touches, as in the exercise of tinting the chess-board. Of
each of these methods I have something to tell you separa