between the two sides, carrying the attention without a break
from one to the other.

The element of mass requires less comment. It appears in
greatest number in those pictures which have little action, i.e. portraits and landscapes, and which are not yet symmetrical,--
in which last case mass is, of course, already balanced. In
fact, it must of necessity exert a certain influence in every
unsymmetrical picture, and so its percentage, even for genre
pictures, is large.

Thus we may regard the elements as both attracting attention to
a certain spot and dispersing it over a field. Those types
which are of a static character (landscapes, altar-pieces)
abound in elements which disperse the attention; those which
are of a dynamic character (genre picture), in those which make
it stable. The ideal composition seems to combine the dynamic
and static elements,--to animate, in short, the whole field of
view, but in a generally bilateral fashion. The elements, in
substitutional symmetry, are then simply means of introducing
variety and action. As a dance in which there are complicated
steps gives the actor and beholder a varied and thus vivified
"balance," and is thus more beautiful than the simple walk, so
a picture composed in substitutional symmetry is more rich in
its suggestions of motor impulse, and thus more beautiful, than
an example of geometrical symmetry.


III

The particular functions of the elements which are substituted