The rest of the defences at Khorsabad were of an inferior character.  The wall of the town had a width of about forty-five feet, and its basement, to the height of three feet, was constructed of stone; but the blocks were neither so large, nor were they hewn with the same care, as those of the palace platform. [PLATE LVII., Fig. 3.] The angles, indeed, were of squared stone; but even there the blocks measured no more than three feet in length and a foot in height:  the rest of the masonry consisted of small polygonal stones, merely smoothed on their outer face, and roughly fitting together in a manner recalling the Cyclopian walls of Greece and Italy.  They were not united by any cement.  Above the stone basement was a massive structure of crude brick, without any facing either of burnt brick or of stone.

The third kind of masonry at Khorsabad was found outside the main wall, and may have formed either part of the lining of the moat or a portion of a tower, which may have projected in advance of the wall at this point. [PLATE LVIII., Fig. 1.] It was entirely of stone.  The lowest 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 width which any such arch has been hitherto found to span is about fifteen feet.