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latter are sometimes like real ramparts, made of crude brick carefully
cemented; a few, as at Qosheish, have a core of hewn stones, which later
generations have covered with masses of brickwork, and strengthened with
constantly renewed buttresses of earth. They wind across the plain with
many unexpected and apparently aimless turns; on closer examination,
however, it may be seen that this irregularity is not to be attributed
to ignorance or caprice. Experience had taught the Egyptians the art
of picking out, upon the almost imperceptible relief of the soil, the
easiest lines to use against the inundation: of these they have followed
carefully the sinuosities, and if the course of the dykes appears
singular, it is to be ascribed to the natural configuration of the
ground. Subsidiary embankments thrown up between the principal ones,
and parallel to the Nile, separate the higher ground bordering the river
from the low lands on the confines of the valley; they divide the larger
basins into smaller divisions of varying area, in which the irrigation
is regulated by means of special trenches. As long as the Nile
is falling, the dwellers on its banks leave their canals in free
communication with it; but they dam them up towards the end of the
winter, just before the return of the inundation, and do not reopen them
till early in August, when the new flood is at its height. The waters
then flowing in by the trenches are arrested by the nearest transverse
dyke and spread over the fields. When they have stood there long enough
to saturate the ground, the dyke is pierced, and they pour into the next
basin until they are stopped by a second dyke, which in its turn forces
them again to spread out on either side. This operation is renewed from
dyke to dyke, till the valley soon becomes a series of artificial ponds,
ranged one above another, and flowing one into another from Grebel
Silsileh to the apex of the Delta. In autumn, the mouth of each ditch is
dammed up anew, in order to prevent the mass of water from flowing back
into the stream. The transverse dykes, which have been cut in various
places, are also repaired, and the basins become completely landlocked,
separated by narrow causeways. In some places, the water thus imprisoned
is so shallow that it is soon absorbed by the soil; in others, it is so
deep, that after it has been kept in for several weeks, it is necessary
to let it run off into a neighbouring depression, or straight