ective should be only a matter of
observation and of the study of relations of color and value. There
are no rules. The effect depends on greater or less density of
atmosphere. Near objects are seen through a thin stratum of air, and
farther objects through a thicker one. All you have to do to express
it is to recognize the relative tones of color. Paint the colors as
they are, as you see them in nature, and you need have no trouble with
aerial perspective.

But though I say "this is all you have to do," don't imagine that I
mean that it is always easy, or that it can be done without thought
and study. You will have to use all your powers of perception if you
wish to do good work in this direction. Especially on clear days, or
in those climates where the air is so rare that objects at great
distances seem near, you will find that atmospheric perspective is
simply another name for close values. And close values, you remember,
are the most subtle of relations of light and shade and color.

The only rule for aerial perspective is to use your eyes, and do
nothing without a previous careful study of nature.

=Linear Perspective.=--For most kinds of painting, a technical
knowledge of linear perspective is not necessary, although every
painter should understand the general principles of it. In most cases
all the exactness needed can be obtained by comparing all lines
carefully with the pencil or brush handle held horizontally or
vertically, and studying the angle any line makes with it. Apply to
all objects in perspective the same observation that you do in any
other kind of drawing, and you will have little trouble, as long as
you are drawing from an object before you. But if you go into
perspective at all, go into it thoroughly. A little perspective is a
dangerous thing, and more likely to mix you up by suggesting all sorts
of half-understood things than to be of any real help.

There are some kinds of subjects, however, which require a complete
knowledge of all the rules and processes of perspective. Whenever you
have to construct a picture from details stated but not seen; when you
have a complicated architectural interior or exterior; when figures
are to be placed at certain distances or in definite positions, and
they are too numerous or the conditions are otherwise such that you
cannot pose your models for this purpose; then you may have to make
most elaborate perspective plans, and lay out your picture with great