The course of the ancient canals was generally straight: but that rule was not strictly observed, and enormous curves were often described in order to avoid even slight irregularities of surface.

Dikes thrown up from the foot of the cliffs to the banks of the Nile divided the plain at intervals into a series of artificial basins, where the overflow formed back-waters at the time of inundation.

These dikes are generally earth-works, though they are sometimes constructed of baked brick, as in the province of Girgeh.

Very rarely are they built of hewn stone, like that great dike of Kosheish which was constructed by Mena in primaeval times, in order to divert the course of the Nile from the spot on which he founded Memphis.[7] The network of canals began near Silsilis and extended to the sea-board, without ever losing touch of the river, save at one spot near Beni Suef, where it throws out a branch in the direction of the Fayum.

Here, through a narrow and sinuous gorge, deepened probably by the hand of man, it passes the rocky barrier which divides that low- lying province from the valley of the Nile, and thence expands into a fanlike ramification of innumerable channels.