size height or
breadth--not both, or you get the same negative character.

So you may apply this principle more or less exactly to the
composition of a picture. Don't try to express too many things in one
picture, or if you do, let some one be the main thing, and all the
rest be subordinate to it. There is perhaps no law more rigid than the
one which denies success to any attempt to scatter force, effect, and
purpose. One main idea in each picture, and everything subordinated to
lend itself to the strengthening of that.

To a certain extent this will apply to line and mass, though not
absolutely. As a rule, line or mass, one or the other, must be the
main element.

=Leverage.=--I have often thought that much insight into the
principles of balance of masses, and of mass and line, could be gained
by thinking of it analogously to equilibrium in leverage. A small
mass, or a simple line or accent, may be made to balance a very much
greater mass. The greater part of a canvas may be one mass, and be
balanced by quite a small spot. But leverage must come in to help.
Somewhere in the picture will be the point of support, the fulcrum.
And the large mass and the small one will have an obvious relation
with reference to that point. Or the element of apparent density will
come in. The large mass will be the least dense, the small one the
most dense, and the equilibrium is established. For composition is but
the equilibrium of the picture, and equilibrium the picture must have.

There are many rules as to placing of mass and arrangement of line,
but they are all more or less arbitrary and limiting in influence.
Individuality must and will ignore such rules, just because
composition deals chiefly with the abstract qualities rules will not
help. A fine feeling or perception of what is right is the only law,
and the trained eye is the only measure. As in values, so in
composition you must study relations in nature, and results in the
work of the masters, to train your eye to see; and you must sketch and
block in all sorts of combinations with your own hand, to give you
practical experience.

=Scale.=--One point of great importance should be noticed. That is the
effect on the observer of the size of any main mass or object with
reference to the size of the canvas. This is analogous to what is
called _scale_ in architecture.

If the mass or object is justly proportioned to the whole surface of
the canvas, and is treated in accorda