tree, or between two chimneys, or through the
corner of a pane in the window you like best to sit at, and try to
gradate a little space of white paper as evenly as that is gradated--as
_tenderly_ you cannot gradate it without color, no, nor with color
either; but you may do it as evenly; or, if you get impatient with your
spots and lines of ink, when you look at the beauty of the sky, the
sense you will have gained of that beauty is something to be thankful
for. But you ought not to be impatient with your pen and ink; for all
great painters, however delicate their perception of color, are fond of
the peculiar effect of light which may be got in a pen-and-ink sketch,
and in a wood-cut, by the gleaming of the white paper between the black
lines; and if you cannot gradate well with pure black lines, you will
never gradate well with pale ones. By looking at any common wood-cuts,
in the cheap publications of the day, you may see how gradation is given
to the sky by leaving the lines farther and farther apart; but you must
make your lines as fine as you can, as well as far apart, towards the
light; and do not try to make them long or straight, but let them cross
irregularly in any directions easy to your hand, depending on nothing
but their gradation for your effect. On this point of direction of
lines, however, I shall have to tell you more, presently; in the
meantime, do not trouble yourself about it.

EXERCISE IV.

15. As soon as you find you can gradate tolerably with the pen, take an
H. or HH. pencil, using its point to produce shade, from the darkest
possible to the palest, in exactly the same manner as the pen,
lightening, however, now with india-rubber instead of the penknife. You
will find that all _pale_ tints of shade are thus easily producible with
great precision and tenderness, but that you cannot get the same dark
power as with the pen and ink, and that the surface of the shade is apt
to become glossy and metallic, or dirty-looking, or sandy. Persevere,
however, in trying to bring it to evenness with the fine point, removing
any single speck or line that may be too black, with the _point_ of the
knife: you must not scratch the whole with the knife as you do the ink.
If you find the texture very speckled-looking, lighten it all over with
india-rubber, and recover it again with sharp, and excessively fine
touches of the pencil point, bringing the parts that are too pale to
perfect evenness with the darker spo