330 THE POPULAR SCIENCE MONTHLY. 



I am afraid, however, that any such modern estimate has not a 

 much surer foundation than the ancient guess. For, in the first place, 

 there are many reasons for believing that the action of the Nile has 

 not been uniform throughout the whole period represented by the 

 deposit of alluvium ; and, in the second place, if it had been, the 

 simple process of division of the total thickness of the alluvium by 

 that of the annual deposit does not by any means necessarily give the 

 age of the whole mass of alluvium in the delta, or, in other words, 

 the time which elapsed during the filling of the delta, as it is some- 

 times supposed to do. 



According to Figari Bey, the deepest, and therefore earliest, al- 

 luvium in the delta contains gravel and even bowlders ; so that, if 

 these are fluviatile beds, which is, perhaps, not quite certain, they in- 

 dicate that, at the time when they were deposited, the current of the 

 Nile in this region was much more powerful than it is now, and, con- 

 sequently, that its annual additions were much more considerable. 



If the flow of the Nile in these ancient times was more rapid, the 

 probabilities are that the volume of its waters was greater, and sundry 

 observations have been adduced as evidence that such was the case. 

 Thus, at Semneh, above the second cataract, Lepsius, many years ago, 

 discovered inscriptions of a Pharaoh of the twelfth dynasty, Amen- 

 emhat III, who reigned between 2,000 and 3,000 b. c, which registered 

 the level of the hio-hest rise of the Nile at that time. And this level 

 is nearly twenty-four feet higher than that of high Nile at the same 

 place now. Another fact has been connected with this. Between 

 the narrow gorge of the Nile at Selsileh and the first cataract, alluvial 

 deposits, containing shells of animals now living in the river, lie on 

 the flanks of the valley, twenty to thirty feet above the point which 

 high Nile reaches at the present day. It has been suggested that, 

 before the Nile cut the gorge, the sandstone bar at Selsileh, as it were, 

 dammed up the Nile, and caused it to stand at a higher level all the 

 way back to Semneh. But, as the late Dr. Leith Adams long ago ar- 

 gued, the sandstone strata of Selsileh could hardly have played the 

 part thus assigned to them. The deposits in question indicate that 

 the supposed barrier at Selsileh was about thirty feet high ; while 

 Semneh is at least one hundred and thirty feet higher than Selsileh. 



The cause of the difference of level of the Nile at Semneh, be- 

 tween the days of Amenemhat and now, is surely rather to be sought 

 in the progressive erosion of the Nubian valley. If four thousand 

 years have elapsed since Amenemhat reigned, the removal of one 

 thirteenth of an inch per annum from the bed of the river will be 

 more than enough to account for its present depression. Considering 

 the extraordinary activity of the denuding forces at work in Nubia, I 

 see nothing improbable in this estimate. But, if it is correct, there is 

 no need to suppose that the Nile conveyed a greater body of water 

 four thousand years ago than it does now. Nor is there anything in 



