180 PIM ON THE ISTHMUS OF SUEZ. [April 11, 1859. 



annually discharged into tlie Mediterranean, and meet an east-going 

 current which carries the mass towards the Bay of Pelusium. The 

 effect of this mud-carrying current would be to silt up any harbour 

 or channel which came in its way. A striking instance of the 

 quantity of mud discharged by the Nile is related in Dr. Clarke's 

 ' Travels.' He says : — 



" July IQth. — This day, being Sunday, we accompanied Captain 

 Culverhouse, H.M.S. Romulus^ to the gun-room, to dine with his 

 officers, according to his weekly custom ; as we were sitting down 

 to dinner the voice of a sailor employed in heaving the lead was 

 suddenly heard calling * half four.' The captain starting up reached 

 the deck in an instant, and almost as quickly putting the ship in 

 stays she went about. Every seaman on board thought she would 

 be stranded. As she came about, the surface of the water exhibited 

 a thick black mud. This extended so widely that the appearance 

 resembled an island, at the same time no land was really visible, 

 not even from the mast-head, nor was there any notice of such a 

 shallow in any chart on board. The fact is (as we learnt afterwards) 

 that a stream of mud, extending for many leagues off the mouths of 

 the Nile, exists in a moveable deposit on the coast of Egypt." 



During the periodical overflow of the Nile, its waters attain in 

 Upper Egypt the height of from 30 to 35 feet ; at Cairo about 23 

 feet ; and in the northern part of the Delta only 4 feet. It begins 

 to rise at Cairo about the beginning of July, increases during 100 

 days till the middle of October, then subsides, and arrives at its 

 lowest point near the end of April. During the period of inunda- 

 tion the current is very powerful, so much so that fresh water may 

 be skimmed off the surface two or three miles at sea. The average 

 force of the current throughout the year may be considered 2^ miles 

 per hour. The minimum discharge has been estimated at 54,000,000 

 cubic feet of water per hour. The amount of alluvium deposit is 

 0-004 inches. At the mouth of both the Damietta and Eosetta 

 branches there is a bar in the form of a horse-shoe, with an average 

 depth of 5 feet water. During high Nile the great velocity of 

 the stream drives this bar some distance to seaward, but, as the 

 strength of the current diminishes, it returns to its original position 

 in the old form. 



The entire supply of sweet water for the whole of Egypt is de- 

 rived from the Nile ; there are wells, it is true, dug in the sands, 

 but the water they contain is generally salt, and even under the 

 most favourable circumstances brackish. 



The stratification of Lower Egypt belongs entirely to the tertiary 

 formation. 



