ff-ball; it may be knotted like a ship's hawser, or kneaded like
hammered iron, or knit like a Damascus saber, or fused like a glass
bottle, or crystallized like hoar-frost, or veined like a forest leaf:
look at it, and don't try to remember how anybody told you to "do a
stone."

109. As soon as you find that your hand obeys you thoroughly, and that
you can render any form with a firmness and truth approaching that of
Turner's or Duerer's work,[24] you must add a simple but equally careful
light and shade to your pen drawing, so as to make each study as
complete as possible; for which you must prepare yourself thus. Get, if
you have the means, a good impression of one plate of Turner's Liber
Studiorum; if possible, one of the subjects named in the note
below.[25] If you cannot obtain, or even borrow for a little while, any
of these engravings, you must use a photograph instead (how, I will tell
you presently); but, if you can get the Turner, it will be best. You
will see that it is composed of a firm etching in line, with mezzotint
shadow laid over it. You must first copy the etched part of it
accurately; to which end put the print against the window, and trace
slowly with the greatest care every black line; retrace this on smooth
drawing-paper; and, finally, go over the whole with your pen, looking at
the original plate always, so that if you err at all, it may be on the
right side, not making a line which is too curved or too straight
already in the tracing, more curved or more straight, as you go over it.
And in doing this, never work after you are tired, nor to "get the thing
done," for if it is badly done, it will be of no use to you. The true
zeal and patience of a quarter of an hour are better than the sulky and
inattentive labor of a whole day. If you have not made the touches right
at the first going over with the pen, retouch them delicately, with
little ink in your pen, thickening or reinforcing them as they need: you
cannot give too much care to the facsimile. Then keep this etched
outline by you in order to study at your ease the way in which Turner
uses his line as preparatory for the subsequent shadow;[26] it is only
in getting the two separate that you will be able to reason on this.
Next, copy once more, though for the fourth time, any part of this
etching which you like, and put on the light and shade with the brush,
and any brown color that matches that of the plate;[27] working it with
the point of t