: implying, secondly,
a determined depth of projection, which it shall rarely reach, and never
exceed: and implying, finally, the production of the whole piece with
the least possible labor of chisel and loss of stone.

166. And these, which are the first, are very nearly the last
constructive laws of sculpture. You will be surprised to find how much
they include, and how much of minor propriety in treatment their
observance involves.

In a very interesting essay on the architecture of the Parthenon, by
the Professor of Architecture of the Ecole Polytechnique, M. Emile
Boutmy, you will find it noticed that the Greeks do not usually weaken,
by carving, the constructive masses of their building; but put their
chief sculpture in the empty spaces between the triglyphs, or beneath
the roof. This is true; but in so doing, they merely build their panel
instead of carving it; they accept, no less than the Goths, the laws of
recess and limitation, as being vital to the safety and dignity of their
design; and their noblest recumbent statues are, constructively, the
fillings of the acute extremity of a panel in the form of an obtusely
summited triangle.

167. In gradual descent from that severest type, you will find that an
immense quantity of sculpture of all times and styles may be generally
embraced under the notion of a mass hewn out of, or, at least, placed
in, a panel or recess, deepening, it may be, into a niche; the sculpture
being always designed with reference to its position in such recess:
and, therefore, to the effect of the building out of which the recess is
hewn.

But, for the sake of simplifying our inquiry, I will at first suppose no
surrounding protective ledge to exist, and that the area of stone we
have to deal with is simply a flat slab, extant from a flat surface
depressed all round it.

168. A _flat_ slab, observe. The flatness of surface is essential to the
problem of bas-relief. The lateral limit of the panel may, or may not,
be required; but the vertical limit of surface _must_ be expressed; and
the art of bas-relief is to give the effect of true form on that
condition. For observe, if nothing more were needed than to make first a
cast of a solid form, then cut it in half, and apply the half of it to
the flat surface;--if, for instance, to carve a bas-relief of an apple,
all I had to do was to cut my sculpture of the whole apple in half, and
pin it to the wall, any ordinarily trained sculptor, or e