hen leave the whole to dry; and, as soon
as it is dry, with little color in your brush, so that you can bring it
to a fine point, fill up all the little interstices one by one, so as to
make the whole as even as you can, and fill in the larger gaps with more
color, always trying to let the edges of the first and of the newly
applied color exactly meet, and not lap over each other. When your new
color dries, you will find it in places a little paler than the first.
Retouch it therefore, trying to get the whole to look quite one piece. A
very small bit of color thus filled up with your very best care, and
brought to look as if it had been quite even from the first, will give
you better practice and more skill than a great deal filled in
carelessly; so do it with your best patience, not leaving the most
minute spot of white; and do not fill in the large pieces first and then
go to the small, but quietly and steadily cover in the whole up to a
marked limit; then advance a little farther, and so on; thus always
seeing distinctly what is done and what undone.

EXERCISE X.

65. Lay a coat of the blue, prepared as usual, over a whole square of
paper. Let it dry. Then another coat over four fifths of the square, or
thereabouts, leaving the edge rather irregular than straight, and let it
dry. Then another coat over three fifths; another over two fifths; and
the last over one fifth; so that the square may present the appearance
of gradual increase in darkness in five bands, each darker than the one
beyond it. Then, with the brush rather dry (as in the former exercise,
when filling up the interstices), try, with small touches, like those
used in the pen etching, only a little broader, to add shade delicately
beyond each edge, so as to lead the darker tints into the paler ones
imperceptibly. By touching the paper very lightly, and putting a
multitude of little touches, crossing and recrossing in every direction,
you will gradually be able to work up to the darker tints, outside of
each, so as quite to efface their edges, and unite them tenderly with
the next tint. The whole square, when done, should look evenly shaded
from dark to pale, with no bars, only a crossing texture of touches,
something like chopped straw, over the whole.[13]

66. Next, take your rounded pebble; arrange it in any light and shade
you like; outline it very loosely with the pencil. Put on a wash of
color, prepared _very_ pale, quite flat over all of it, ex