re always similar in the fact of being wholly
free--round as Vasari calls them--of being interfered with by no
complications of shadows like the figures of a high, middle or
bas-relief; hence, as soon as the figures cease to be round, as soon as
they are attached to a back-ground, the whole composition is altered
by the consideration how the different degrees of projection, and the
consequent play of light and shadow, will affect the apparent shape
of the figures. And yet we are still within the domain of sculpture.
How great a difference of form will not result when, instead of the
tintless, tangible projections of stone, we get to the mere semblance
of infinite depth and distance cunningly obtained by light and shade,
colour and perspective, on a flat surface; where the light, instead of
existing variable and confusing outside the work, is within that very
work, inside the picture, combining, graduating every detail, making
form melt gently into form, or stand out in triumphant relief? Thus the
things which can be done in bronze must not be attempted in porphyry,
the group of statues must be conceived differently from the bas-relief;
the picture is different from the statue; for the beauty of form depends
not only on the conception but upon the embodiment: if the material is
violent, the conception is warped; and the same beauty can be obtained
in all the arts only by remembering that those arts are different that,
with the material and modes of handling, must change the conception.

Thus we have seen that the sculptor of the Niobe deliberately refused
to embody his complete mental vision of the scene of massacre; that he
selected among the attitudes and gestures and expressions suggested
to him by this scene, rejected those which were inherently ugly, and
accepted those which were intrinsically beautiful; and that he left out
of his representation of the incidents its principal actors, because he
could not have introduced them without either violating the nature of
the whole composition to which he was bound, or violating the nature of
the material in which he was working, and by so doing sacrificing the
perfection of visible form which, being the only intrinsic quality to
which his art could independently attain, was the one object of his
desires and efforts. Such is the logical conclusion which we have
consciously and perhaps wearisomely obtained from our analysis of the
mode of conception and treatment of the Niobe