r may be, though not larger than 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 color should be
gradated; the preciousness and pleasantness of the color itself depends
more on this than on any other of its qualities, for gradation is to
colors 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 color, may be seen easily by laying an even tint of
rose-color 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 color 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.

169. (4.) But observe, it is not enough in general that color should be
gradated by being made merely paler or darker at one place than another.
Generally color 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 spots 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 color 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,--grayish 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
color is wet, mix with it the color which is to subdue it, adding
gradually a little more and a little more; or else, when the color is
quite dry, strike a gradated touch of another color 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 somethi