413 
EFFECTS OF EMBANKING THE NILE. 
Nile water over a great extent of soil it does not now reach. 
We may, then, adopt a mean between the two quantities, and 
we shall probably come near the truth if we assume the con¬ 
venient number of 7,920 square statute miles as the average 
measure of the inundated land during the historical period. 
Taking the deposit on this surface at ten feet, the river sedi¬ 
ment let fall on the soil of Egypt within the last fifty centuries 
would amount to fifteen cubic miles. 
Had the Nile been banked in, like the Po, all this deposit, 
except that contained in the water diverted by canals or other¬ 
wise drawn from the river for irrigation and other purposes, 
would have been carried out to sea.* This would have been 
a considerable quantity; for the Nile holds earth in suspen¬ 
sion even at low water, a much larger proportion during the 
flood, and irrigation must have been carried on during the 
whole year. The precise amount which would have been thus 
distributed over the soil is matter of conjecture, but three 
cubic miles is certainly a liberal estimate. This would leave 
twelve cubic miles as the quantity which embankments would 
have compelled the Nile to transport to the Mediterranean over 
and above what it has actually deposited in that sea. The 
Mediterranean is shoal for some miles out to sea along the 
whole coast of the Delta, and the large bays or lagoons within 
the coast line, which communicate both with the river and the 
sea, have little depth of water. These lagoons the river deposits 
would have filled up, and there would still have been surplus 
earth enough to extend the Delta far into the Mediterranean.! 
* There are many dikes in Egypt, but they are employed in but a very 
few cases to exclude the waters of the inundation. Their office is to retain 
the water received at high Nile into the inclosures formed by them until it 
shall have deposited its sediment or been drawn out for irrigation; and 
they serve also as causeways for interior communication during the floods. 
The Egyptian dikes, therefore, instead of forcing the river, like those of 
the Po, to transport its sediment to the sea, help to retain the slime, which, 
if the flow of the current over the land were not obstructed, might be car¬ 
ried back into the channel, and at last to the Mediterranean. 
t The Mediterranean front of the Delta may be estimated at one hun¬ 
dred and fifty miles in length. Two cubic miles of earth would more than 
