THE ELEMENTS OF DRAWING. [lettek i.
darkness, or power of dark relief from white — some
more, some less; and how this pitch or power of each
may be represented by equivalent values of grey, you
will soon be able to arrive shrewdly at an approxima-
tion by a glance of the eye, without any measuring
scale at all.
You must now go on, again with the pen, drawing
patterns, and any shapes of shade that you think
pretty, as veinings in marble or tortoiseshell, spots
in surfaces of shells, &c, as tenderly as you can, in
the darknesses that correspond to their colours; and
when you find you can do this successfully, it is
time to begin rounding.
Gfo out into your garden, or into the road, and
pick up the first round or oval stone you can find,
not very white, nor very dark; and the smoother it
is the better, only it must not shine. Draw your
table near the window, and put the stone, which I