rossed lines, so completely
and evenly that it shall look like a square patch of grey silk or cloth,
cut out and laid on the white paper, as at _b_. Cover it quickly, first
with straightish lines, in any direction you like, not troubling
yourself to draw them much closer or neater than those in the square
_a_. Let them quite dry before retouching them. (If you draw three or
four squares side by side, you may always be going on with one while the
others are drying). Then cover these lines with others in a different
direction, and let those dry; then in another direction still, and let
those dry. Always wait long enough to run no risk of blotting, and then
draw the lines as quickly as you can. Each ought to be laid on as
swiftly as the dash of the pen of a good writer; but if you try to reach
this great speed at first you will go over the edge of the square, which
is a fault in this exercise. Yet it is better to do so now and then than
to draw the lines very slowly; for if you do, the pen leaves a little
dot of ink at the end of each line, and these dots spoil your work. So
draw each line quickly, stopping always as nearly as you can at the edge
of the square. The ends of lines which go over the edge are afterwards
to be removed with the penknife, but not till you have done the whole
work, otherwise you roughen the paper, and the next line that goes over
the edge makes a blot.

When you have gone over the whole three or four times, you will find
some parts of the square look darker than other parts. Now try to make
the lighter parts as dark as the rest, so that the whole may be of equal
depth or darkness. You will find, on examining the work, that where it
looks darkest the lines are closest, or there are some much darker
lines, than elsewhere; therefore you must put in other lines, or little
scratches and dots, _between_ the lines in the paler parts; and where
there are very conspicuous dark lines, scratch them out lightly with the
penknife, for the eye must not be attracted by any line in particular.
The more carefully and delicately you fill in the little gaps and holes
the better; you will get on faster by doing two or three squares
perfectly than a great many badly. As the tint gets closer and begins to
look even, work with very little ink in your pen, so as hardly to make
any mark on the paper; and at last, where it is too dark, use the edge
of your penknife very lightly, and for some time, to wear it softly into
an