of the angle piers into two quasi-pilasters. At Warka they
appear in the higher part of the facade, above the groups of semi-columns.
They serve to mark out a series of panels, of which only the lower parts
have been preserved. The missing parts of the decoration may easily be
supplied by a little study of the Assyrian remains. The four sides of the
building at Khorsabad, called by M. Place the _Observatory_, are decorated
uniformly in this fashion. The general effect may be gathered from our
restoration of one angle. The architect was not content with decorating his
wall with these grooves alone; he divided it into alternate compartments,
the one salient, the next set back, and upon these compartments he ploughed
the long lines of his decoration. These changes of surface helped greatly
to produce the varied play of light and shadow upon which the architect
depended for relief to the bare masses of his walls. The most ordinary
workmen could be trusted to carry out a decoration that consisted merely in
repeating, at certain measured intervals, as simple a form as can be
imagined, and, in the language of art as in that of rhetoric, there is no
figure more effective in its proper place than repetition.

[Illustration: FIG. 101.--Decoration of one of the harem gates, at
Khorsabad; compiled from Place.]

The necessity for something to break the monotony of the brick
architecture was generally and permanently felt, and in those Parthian and
Sassanide periods in which, as we have said, the traditions of the old
Chaldaean school were continued, we find the panel replaced by wall arcades
in which the arches are divided from each other by tall pilasters. In
general principle and intention the two methods of decoration are
identical.

The Egyptian architect had recourse to the same motive, first, in the tombs
of the Ancient Empire for the decoration of the chamber walls in the
mastabas; secondly, for the relief of great brick surfaces. The resemblance
to the Mesopotamian work is sometimes very great.[313]

We have explained this form by one of the transpositions so frequent in the
history of architecture, namely, a conveyance of motives from carpentry to
brickwork and masonry.[314] In the former the openings left in the skeleton
are gradually filled in, and these additions, by the very nature of their
materials, most frequently take the form of panels. The grooves that define
the panels in brick or stone buildings represent the