Mr Nash on the Geology of Egypt. 43 



At Cairo, as has already been stated, the limestone ridges 

 diverge, leaving the Delta-shaped plain, through which flow the 

 two principal arms of the Nile, as well as several other minor 

 branches. The space included between the Rosetta and Da- 

 mietta branches is at its widest about 200 miles, and this is the 

 extent of the alluvial formation of Egypt. There are, however, 

 considerable alluvial deposits along the course of the river and 

 in the plain of Fayoum. This alluvium has been deposited 

 over a considerable extent of country, now covered over by the 

 ever encroaching sands of the desert, conveyed by the pernicious 

 west wind, which the ancient Egyptians so figuratively pour- 

 trayed under the symbol of the destroying Typhon. All these 

 alluvial formations derive their origin from the waters of the 

 Nile, which, when swollen by the tropical rains of Nubia and 

 Abyssinia, bring down with them vast quantities of mud and 

 soil. There has been considerable dispute as to whether the 

 entire Delta owes its existence to the waters of the Nile ; be this 

 as it may, there can be no doubt that the alluvium annually de- 

 posited is very considerable, and that the surface, at least of the 

 soil below Cairo, is covered by this deposit. In fact, throughout 

 all Upper and Middle Egypt, from Assouan to near Cairo, the 

 bed of the Nile is, after the periodical rains in Nubia, little else 

 than the bed of a torrent, with here and there an inconsiderable 

 expansion : such as the plain of Thebes. Its waters rush down 

 to empty themselves into the Mediterranean with great velocity, 

 and the alluvial matter which they hold suspended, must natu- 

 rally be precipitated, when these waters are spread out into the 

 wide expanse of level ground below Cairo. Bruce has sta- 

 ted that the waters of the Nile contain but a very small quan- 

 tity of earthy matter ; but even long after the inundation has 

 subsided, it is necessary to allow this water to stand for a con- 

 siderable time in your water-skin before drinking it, in order to 

 allow the mud which it contains to precipitate. But, if the gra- 

 dual efforts of the river have added a few leagues to the soil of 

 Egypt, it is no less certain that in other parts Egypt has 

 yielded up a portion of her territory to the encroachments of 

 the ocean, much of what was formerly a fertile plain, being 

 now converted into salt-lakes. 



