begun their great works of canalisation. Doubtless most of the monuments
erected near the river, such as the slabs of stone paving the great avenue of
sphinxes at Kurnuk, the colossal statues of Memnon, and even a block bearing a comparatively recent Greek inscription, are now found buried to some depth below the surface. But this is due not so much to change of level as to subsidence, such huge masses naturally sinking gradually in the alluvial soil of the riverain plains. In the same way the erratic boulders in Switzerland and the colonnades of the
Roman temples have sunk more and more below the surrounding surface. The
Nilometer discovered by Girard in Elephantine Island is perhaps one of those monuments whose foundations have thus given way. Hence although the present high-water mark may exceed the old measurement by 8 or 9 feet, it does not follow that the bed of the river and its banks have been raised to that extent. Such a phenomenon could not be reconciled with the drying up of the old bed east of Asuan, which has now been abandoned by the stream.
Volume and Periodical Rising op the Nile.
The yearly overflow of the Nile, which renews all nature, and which was celebrated by the Egyptians as the resurrection of a god, is of such regular occurrence that it was formerly compared with the revolutions of the heavenly orbs. How could the riverain populations refrain from worshipping this stream, "Creator of wheat and giver of barley," a stream but for which " the gods would fall prostrate and all men perish"? "Hail, Nile!" sang the priests of old, "Hail, thou that comest to give life to Egypt!" According to its periodical return all things were and still are regulated—field operations, town work, civil and religious feasts. But at present it is easier to prepare for the rising waters, which are announced from Khartum thirty or forty days beforehand. They begin to appear nearly always on June 10th, at first "green" with vegetable refuse from the great lagoons of the upper basin. But the rise is very slight till about the middle of July, when the stream becomes suddenly swollen by the "red" waters from the Abyssinian highlands. Towards the end of August the Nile is nearly full, but continues to increase slightly till October 7th, when it usually reaches its culminating point. After this date the subsidence sets in and continues very gradually till the return of the floods the following June.
During the three months of high water the Nile sends seawards a liquid mass equal to about three-fourths of the whole annual discharge, or 3,150 billions cubic feet out of a total of 4,200 billions. High-water mark naturally diminishes down stream, falling from about 56 feet at Asuan to 24 or 25 at Cairo. Relying on some of the old texts, especially a much-disputed passage in Herodotus, some writers suppose that the level of the floods has been considerably modified since the first centuries of Egyptian history, although sufficient data are lacking to determine the point with certainty. In any case the mean elevation has undergone no change since the end of the eighteenth century of the new era. The careful measurements taken at that time have since been maintained, and they are
