her in shape from those above
described, being formed for special purposes. Of this kind are the
triangular bricks used at the corners of walls, intended to give greater
regularity to the angles than would otherwise be attained; and the
wedge-shaped bricks, formed to be employed in arches, which were known
and used by this primitive people.

The modes of applying these materials to building purposes were various.
Sometimes the crude and the burnt brick were used in alternate layers,
each layer being several feet in thickness; more commonly the crude brick
was used (as already noticed) for the internal parts of the building, and
a facing of burnt brick protected the whole from the weather.
Occasionally the mass of an edifice was composed entirely of crude brick;
but in such cases special precautions had to be taken to secure the
stability of this comparatively frail material. In the first place, at
intervals of four or five feet, a thick layer of reed matting was
interposed along the whole extent of the building, which appears to have
been intended to protect the earthy mass from disintegration, by its
protection beyond the rest of the external surface. The readers of
Herodotus are familiar with this feature, which (according to him)
occurred in the massive walls whereby Babylon was surrounded. If this
was really the case, we may conclude that those walls were not composed
of burnt brick, as he imagined, but of the sun-dried material. Reeds
were never employed in buildings composed of burnt brick, being useless
in such cases; where their impression is found, as not unfrequently
happens, on bricks of this kind, the brick has been laid upon reed
matting when in a soft state, and afterwards submitted to the action of
fire. In edifices of crude brick, the reeds were no doubt of great
service, and have enabled some buildings of the kind to endure to the
present day. They are very strikingly conspicuous where they occur,
since they stripe the whole building with continuous horizontal lines,
having at a distance somewhat the effect of the courses of dark marble in
an Italian structure of the Byzantine period.

Another characteristic of the edifices in which crude brick is thus
largely employed, is the addition externally of solid and massive
buttresses of the burnt material. These buttresses have sometimes a very
considerable projection; they are broad, but not high, extending less
than half way up the walls against wh