eye when one cannot draw
with the pencil. If observation does not keep step with practice you
will do nothing really good.

_Ingres._

CXXI

As a means of practising this perspective of the variation and loss or
diminution of the proper essence of colours, take at distances, a
hundred braccia apart, objects standing in the landscape, such as trees,
houses, men, and places, and in front of the first tree fix a piece of
glass so that it is quite steady, and then let your eye rest upon it and
trace out a tree upon the glass above the outline of the tree; and
afterwards remove the glass so far to one side that the actual tree
seems almost to touch the one that you have drawn. Then colour your
drawing in such a way that the two are alike in colour and form, and
that if you close one eye both seem painted on the glass and the same
distance away. Then proceed in the same way with a second and a third
tree, at distances of a hundred braccia from each other. And these will
always serve as your standards and teachers when you are at work on
pictures where they can be applied, and they will cause the work to be
successful in its distance. But I find it is a rule that the second is
reduced to four-fifths the size of the first when it is twenty braccia
distant from it.

_Leonardo._

CXXII

The great and golden rule of art, as well as of life, is this: That the
more distinct, sharp, and wiry the bounding line, the more perfect the
work of art.... Great inventors in all ages knew this: Protogenes and
Apelles knew each other by this line; Raphael and Michael Angelo, and
Albert Duerer, are known by this and this alone. The want of this
determinate and bounding form evidences the idea of want in the artist's
mind.

_Blake._

CXXIII

My opinion is that he who knows how to draw well and merely does a foot
or a hand or a neck, can paint everything created in the world; and yet
there are painters who paint everything there is in the world so
impatiently and so much without worth that it would be better not to do
it at all. One recognises the knowledge of a great man in the fear with
which he does a thing the more he understands it; and, on the contrary,
the ignorance of others in the foolhardy daring with which they fill
pictures with what they know nothing about. There may be an excellent
master who has never painted more than a single figure, and without
painting anything more deserves more renown and honour than those