As at Askura, one is struck by the labour that has been expended in ensuring a continual supply of water for the gardens. This is done by means of innumerable small canals. On account of the level of the gardens being somewhat higher than that of the river-bed, the water has in almost all cases to be drawn off from the main stream far above the _ksor_ and gardens it is to supply, and this fact is a constant cause of warfare; for when a village is separated from the river by a couple of miles perhaps of canal, on which it entirely depends for its supply, the enemy soon take advantage of the fact and cut off their water, which raises the siege at once, and a sortie has to be made by the defenders. Nor is it only during war, for, more often still, the original commencement of the strife is the fact that some one has drawn off the contents of some one else’s canal, and a feud commences. The water, however, serves a purpose in warfare other than raising sieges by being cut off, for the very opposite policy is often resorted to, and water brought to play upon the soft _tabia_ walls of the _ksar_, a channel being dug right up to the building. Strong as it is to withstand the effects of climate, _tabia_ is like blotting-paper before water, and almost as soon as the walls are reached the building commences to crumble away from the foundations, imperiling the lives of all within, and necessitating a sudden flight, and probably the falling into the hands of the enemy waiting without. In order to prevent their enemies from approaching the _ksor_ and cutting off or turning on the water, both equally disastrous, watch-towers are built along the banks of the canals. The _äudin_, as the natives call them, are usually square towers some 30 to 40 feet in height, and full of loopholes. In case of war they are garrisoned with a handful of men who are supplied with sufficient quantities of water and provisions to stand a siege, and from them a guard can be kept over the canal and its banks, while their position—the summit, as a rule, of mounds—prevents the water being turned on to their foundations. The whole of the Dads valley is sprinkled with these towers, which add a by no means unpicturesque feature to their scenery.