course was formed of small and very irregular polygonal blocks roughly
fitted together; above this came two courses of carefully squared stones
more than a foot long, but less than six inches in width, which were
placed end-wise, one over the other, care being taken that the joints of
the upper tier should never coincide exactly with those of the lower.
Above these was a third course of hewn stones, somewhat smaller than the
others, which were laid in the ordinary manner. Here the construction,
as discovered, terminated; but it was evident, from the _debris_ of hewn
stones at the foot of the wall, that originally the courses had been
continued to a much greater height.

[Illustration: PLATE 58]

In this description of the buildings raised by the Assyrians it has been
noticed more than once that they were not ignorant of the use of the
arch. The old notion that the round arch was a discovery of the Roman,
and the pointed of the Gothic architecture, has gradually faded away
with our ever-increasing knowledge of the actual state of the ancient
world; and antiquarians were not, perhaps, very much surprised to learn,
by the discoveries of Mr. Layard, that the Assyrians knew and used both
kinds of arch in their constructions. Some interest, however, will
probably be felt to attach to the two questions, how they formed their
arches, and to what uses they applied them.

All the Assyrian arches hitherto discovered are of brick. The round
arches are both of the crude and of the kiln-dried material, and are
formed, in each case, of brick made expressly for vaulting, slightly
convex at top and slightly concave at bottom, with one broader and one
narrower end. The arches are of the simplest kind, being exactly
semicircular, and rising from plain perpendicular jambs. The greatest