21', at the point where a considerable brook, the Khosr-su, falls into the main stream.

On its west flank flowed the broad and rapid Tigris, the "arrow-stream," as we may translate the word; while north, east, and south, expanded the vast undulating plain which intervenes between the river and the Zagros mountain-range.

Mid-way in this plain, at the distance of from 15 to 18 miles from the city, stood boldly up the Jabel Maklub and Ain Sufra hills, calcareous ridges rising nearly 2000 feet above the level of the Tigris, and forming by far the most prominent objects in the natural landscape.

Inside the Ain Sufra, and parallel to it, ran the small stream of the Gomel, or Ghazir, like a ditch skirting a wall, an additional defence in that quarter.

On the south-east and south, distant about fifteen miles, was the strong and impetuous current of the Upper Zab, completing the natural defences of the position which was excellently chosen to be the site of a great capital.
[Illustration: PLATE 24] South of Nineveh, at the distance of about twenty miles by the direct route and thirty by the course of the Tigris, stood the second city of the empire, Calah, the site of which is marked by the extensive ruins at Nimrud.