Far different would be the aspect of the region were a due use made of that abundant water supply--actually most lavish in the summer time, owing to the melting of the snows which nature has provided in the two great Mesopotamian rivers and their tributaries. So rapid is the fall of the two main streams in their upper course, that by channels derived from them, with the help perhaps of dams thrown across them at certain intervals, the water might be led to almost any part of the intervening country, and a supply kept up during the whole year. Or, even without works of this magnitude, by hydraulic machines of a very simple construction, the life-giving fluid might be raised from the great streams and their affluents in sufficient quantity to maintain a broad belt on either side of the river-courses in perpetual verdure. Anciently, we know that recourse was had to both of these systems. In the tract between the Tigris and the Upper Zab, which is the only part of Assyria that has been minutely examined, are distinct remains of at least one Assyrian canal, wherein much ingenuity and hydraulic skill is exhibited, the work being carried through the more elevated ground by tunnelling, and the canal led for eight miles contrary to the natural course of every stream in the district. Sluices and dams, cut sometimes in the solid rock, regulated the supply of the fluid at different seasons, and enabled the natives to make the most economical application of the great fertilizer. The use of the hand-swipe was also certainly known, since it is mentioned by Herodotus, and even represented upon the sculptures. [PLATE XXV., Fig. 1.] Very probably other more elaborate machines were likewise employed, unless the general prevalency of canals superseded their necessity. It is certain that over wide districts, now dependent for productive power wholly on the spring rains, and consequently quite incapable of sustaining a settled population, there must have been maintained in Assyrian times some effective water-system, whereby regions that at present with difficulty furnish a few months’ subsistence to the wandering Arab tribes, were enabled to supply to scores of populous cities sufficient food for their consumption. [Illustration: PLATE 25]