358 THE BOTTOM OF THE SEA. 



whole extent of the river's basin. The delta of the 

 Nile, therefore, increases less rapidly than those of 

 the Mississippi and of the Po, and this in spite of 

 the relative smallness of the basin of the last-men- 

 tioned river. 



The ancient Egyptians knew the importance of 

 the alluvial matter carried in suspension by rivers. 

 Herodotus (Book II. chap, x.) cites the opinion of the 

 Egyptian priests, according to whom Lower Egypt 

 is a present from the Nile, which has filled, by the 

 deposition of its mud, an arm of the sea enclosed 

 between Libya and the Arabian mountains. He 

 adds, that if the lead be thrown at the distance 

 of a day's journey from the sea it will come up 

 well covered with mud from a depth of eleven 

 fathoms. Herodotus bases his opinion on the fact 

 that the superficial soil of this country is a blackish 

 mud from Ethiopia, which contrasts with the sand 

 and gravel, the ordinary soil of these countries. 



The Egyptian priests also remarked, in Hero- 

 dotus' time, that under M ris, 900 years before, 

 if the Nile in its annual overflow rose eight bits, 

 it watered the whole of the plain below Memphis, 

 and that it then produced the same effect only when 

 it rose fifteen or sixteen cubits. 



Aristotle speaks of the variation of the seas in 

 his " Treatise on Meteors." *' Egypt," he says, " fur- 



