On the agriculture of the Assyrians a very few remarks will be offered. It has been already explained that the extent of cultivation depended entirely on the conveyance of water. There is good reason to believe that the Assyrians found a way to spread water over almost the whole of their territory. Either by the system of _kanats_ or subterranean aqueducts, which has prevailed in the East from very early times, or by an elaborate network of canals, the fertilizing fluid was conveyed to nearly every part of Mesopotamia, which shows by its innumerable mounds, in regions which are now deserts, how large a population it was made to sustain under the wise management of the great Assyrians monarchs. Huge dams seem to have been thrown across the Tigris in various places, one of which (the Afrui) still remains, seriously impeding the navigation. It is formed of large masses of squared stones, united together by cramps of iron. Such artificial barriers were intended, not (as Strabo believed) for the protection of the towns upon the river from a hostile fleet, but to raise the level of the stream, in order that its water might flow off into canals on one bank or the other, whence they could be spread by means of minor channels over large tracts of territory. The canals themselves have in most cases been gradually filled up. In one instance, however, owing either to the peculiar nature of the soil or to some unexplained cause, we are still able to trace the course of an Assyrian work of this class and to observe the manner and principles of its construction. [Illustration: PLATE 134]