32 GEOLOGY 



is shown by the presence of beds of alhivium many feet above 

 the level of the present high Nile : that it has changed its 

 bed and altered its elevation even Avithin the historical 

 period, is evident from marks left by the swollen river on 

 monuments both in Egypt and Nubia. Close to the famous 

 rock temple of Aboo Simbel is a small temple, where at the 

 present time the Nile, when high, washes the door-sill and 

 the legs of a seated figure. At Kom Ombo, twenty-five 

 miles north of Assouan, the old temple is built on a heap of 

 alluvium, which is now being rapidly undermined, while 

 shallows and sandbanks are being formed on the opposite 

 side of the river. At Silsilis the river has changed consider- 

 ably within the historical period, and is stiU encroaching on 

 the left bank. Further north, in a small grotto, the high 

 Nile rises above the threshhold, and washes a set of river-gods 

 up to then- necks. While throughout Egypt the Nile appears 

 to rise higher now than it did formerly, in Ethiopia it has 

 sunk ; for at Semneh, thirty-five miles south of Wady Halfeh, 

 just beneath the eastern temple, there are some early hiero- 

 glyphic inscriptions, recording the rise of the Nile during the 

 reign of Amun-ni-he III., about 2000 b.c, from which we 

 learn that in those days it rose considerably higher at this 

 spot than it does at present. 



The present fall of the Nile below the First Cataract is five 

 inches in the mile, or 300 feet from Assouan to Alexandria ; but 

 it must have been greater formerly, before the formation of the 

 Delta, as the Mediterranean then extended inland as far as 

 Memphis, forming a bay or gulf 100 miles in length ; and 

 the Nile must have been sixty feet lower at that point than it 

 now is, i.e. at the level of the sea. The force of the Nile- 

 current must therefore have been stronger formerly than it 



