f her dress by a linear limit,
which he follows with his pen just as decisively. Here, therefore, is
your first great law. Wherever you see one space of color
distinguished from another by a sharp limit, you are to draw that
limit firmly; and that is your outline.

23. Also, observe that as your representing this limit by a dark line
is a conventionalism, and just as much a conventionalism when the line
is subtle as when it is thick, the great masters accept and declare
that conventionalism with perfect frankness, and use bold and decisive
outline, if any.

Also, observe, that though, when you are master of your art, you may
modify your outline by making it dark in some parts, light in others,
and even sometimes thick and sometimes slender, a scientifically
accurate outline is perfectly equal throughout; and in your first
practice I wish you to use always a pen with a blunt point, which will
make no hair stroke under any conditions. So that using black ink and
only one movement of the pen, not returning to thicken your line, you
shall either have your line there, or not there; and that you may not
be able to gradate or change it, in any way or degree whatsoever.

24. Now the first question respecting it is: what place is your thick
line to have with respect to the limit which it represents--outside
of it, or inside, or over it? Theoretically, it is to be over it; the
true limit falling all the way along the center of your thick line.
The contest of Apelles with Protogenes consisted in striking this true
limit within each other's lines, more and more finely. And you may
always consider your pen line as representing the first incision for
sculpture, the true limit being the sharp center of the incision.

But, practically, when you are outlining a light object defined
against a dark one, the line must go outside of it; and when a dark
object against a light one, inside of it.

In this drawing of Holbein's, the hand being seen against the light,
the outline goes inside the contour of the fingers.

25. Secondly. And this is of great importance. It will happen
constantly that forms are entirely distinct from each other and
separated by true limits, which are yet invisible, or nearly so, to
the eye. I place, for instance, one of these eggs in front of the
other, and probably to most of you the separation in the light is
indiscernible. Is it then to be outlined? In practically combining
outline with accomplished light an