The mode in which the walls were constructed seems to have been the following.  Up to a certain height—­fifty feet, according to Xenophon—­they were composed of neatly-hewn blocks of a fossiliferous limestone, smoothed and polished on the outside.  Above this, the material used was sun-dried brick.  The stone masonry was certainly ornamented along its top by a continuous series of battlements or gradines in the same material [PLATE XXXVII., Fig. 2] and it is not unlikely that a similar ornamentation crowned the upper brick structure.  The wall was pierced at irregular intervals by gates, above which rose lofty towers; while towers, probably of lesser elevation, occurred also in the portions of the wall intervening between one gate and another.  A gate in the north-western rampart has been cleared by means of excavation, the form and construction of which will best appear from the annexed ground-plan. [PLATE XXXVII., Fig. 3.] It seems to have consisted of three gateways, whereof the inner and outer were ornamented with colossal human-headed hulls and other figures, while the central one was merely panelled with slabs of alabaster.  Between the gateways were two large chambers, 70 feet long by 23 feet wide, which were thus capable of containing a considerable body of soldiers.  The chambers and gateways are supposed to have been arched over, like the castles’ gates on the bas-reliefs.  The gates themselves have wholly disappeared:  but the debris which filled both the chambers and the passages contained so much charcoal that it is thought they must have been made, not of bronze, like the gates of Babylon, but of wood.  The ground within the gate-way was paved with large slabs of limestone, still bearing the marks of chariot wheels.

The castellated rampart which thus surrounded and guarded Nineveh did not constitute by any means its sole defence.  Outside the stone basement wall lay on every side a water barrier, consisting on the west and south of natural river courses; on the north and east, of artificial channels into which water was conducted from the Khosr-su.  The northern and eastern walls were skirted along their whole length by a broad and deep moat, into which the Khosr-su was made to flow by occupying its natural bed with a strong dam carried across it in the line of the eastern wall, and at the point where the stream now enters the enclosure.  On meeting this obstruction, of which there are still some remains, the waters divided, and while part flowed to the south-east, and reached the Tigris by the ravine immediately to the south of the city, which is a natural water-course, part turned at an acute angle to the north-west, and, washing the remainder of the eastern and the whole of the northern wall, gained the Tigris at the north-west angle of the city, where a second dam kept it at a sufficient height.  Moreover, on the eastern face, which appears to have been regarded as the weakest, a series of outworks were erected for the further defence of