-8 On the Arabian Frontier of Egypt. 



that 15 feet of the alluvial soil have been dug through vv^ith- 

 out reaching the bottom ; — because either all this, or more, 

 or only a part of it, may be of submarine formation like the 

 Delta ; and unless we could determine the precise period when 

 the Mediten-anean retired ; and had also an opportunity of 

 subjecting the contents of the deposits to geological scrutiny, 

 it would be fruitless to stop to conjecture how fiir the hollow 

 between the two rocky plateaus that form the sides of the 

 valley may have been filled up while yet under the sea ; — and 

 how much the raising of its surface may be due to the sub- 

 sequent depositions of such a lake as the Nile Avould form 

 there, if the sea had retired before the hollow was filled up. 

 And such a conjecture would be quite useless to the present 

 inquiry, wliich requires nothing more than the undeniable 

 physical fact, attested by the present form of the land as de- 

 lineated in the section, that, whereas the water-line dis- 

 tinctly shews that the Nile must have run through the val- 

 ley, and would do so still if it were allowed to have its own 

 way ; — nevertheless, the land-line as distinctly shews, that 

 when it ceased to flow in and thi'ough the valley, it had not 

 done so long enough to fill up the entire hollow. For, consider- 

 ing the present depth of this hollow, compared with the 

 height of the swell that terminates it, Ave must see that, had 

 the river that flowed through it, been allowed to flow on, it 

 must have continued open naturally, until its deposits had 

 brought up its whole bed along the valley to the level of the 

 obstacle. It must at last have made for itself an even and 

 shallow bed with an insensible slope towards the sea, like 

 that of the defunct Pelusiac. The form of the valley alone 

 compels us to conclude, that, if the river has ceased to flow 

 tliere, it cannot have ceased from a natural stoppage, but 

 must have been inttjrcepted abruptly, whether by art or by 

 accident, at a time when the level of its course was only 

 sufiiciently raised and equalized to make its channel along 

 the valley merely a little wider and deeper in parts than an 

 ordinary Delta channel ; so as even to form in two or three 

 places, considerable pools, not to say lakes, but of no very 

 great depth. 



In addition to these considerations, we shall find other rea- 



