Rocks in the Nile Valley^ in Nubia. 135 



fall of the Nile in Lower Egypt, at the lowest water, is little more 

 than one-third of that now stated. At the time of the highest water 

 the surface of the Nile, at Boulak, near Cairo; that is, about 116 

 -miles in a direct line from the coast is only 43*437 English feet 

 above the level of the Mediterranean, and at the time of the lowest 

 water, only 17*33 feet. Thus, in the first case, there is an ave- 

 rage fall of about 500 inches ; in the second, of not more than 1*80 

 inches in a mile.* 



Between Wadi Haifa and Dale, a distance of about 94 miles, six 

 cataracts, or schellals, as they are called in the language of the 

 country, are marked in Russegger's map. And here, it may 

 be as well to notice, that there are no cataracts, in the ordinary 

 sense of the term, on the Nile ; no fall of the river over a pre- 

 cipice ; all the so-called cataracts are rapids, where the river 

 rushes through rocks in its bed ; the rapids varying in their length 

 and degrees of inclination. We have no measurements of their 

 lengths or of their falls, except as regards the first and second cata- 

 racts. The former, according to Russegger, has a fall of about 86 

 English feet in a distance of about 8 miles ; and he describes the latter 

 as extending from 5 to 6 stunden; that is, from 12 to 14J miles, but 

 he does not give the height. Speaking of the schellals above Semne, 

 Russegger says, that all may be passed in boats without difficulty 

 for about six weeks, or two months in the year. This is the case 

 also, at the cataract or rapid of Assuan. But between Wadi-Halfa 

 and Dale, with some inconsiderable spaces of free navigable water, 

 in the ordinary state of the river, there is an almost uninterrupted 

 series of rapids. We have no measurement of the height of Dale 

 above Wadi-Halfa, near to which the second great cataract of the 

 Nile occurs ; but this is the part of the river's course where the fall 

 is greatest, and from Semne to Dale there are about 45 miles of this 

 more rapid fall. 



From Dale to New Dongola, a distance of 35 German, or about 

 168 English miles, only three rapids are marked on Russegger's 

 map — the highest being at Hannek, about 26 English miles below 

 New Dongola. New Dongola being 806 English feet above 

 the sea, and the distance from that place to the rapid of Hannek 

 being 26 miles only, we may with probability estimate the surface 

 of the river at the rapid of Hannek at 780 feet above the sea. Now, 

 Wadi-Halfa being 522 feet, we have a difference of hoight, between 

 these two last-named places, of 258 feet ; and the length of the 

 river's course between them being 236 miles, we have an average 

 fall of 13*12 inches in a mile; that is, in the part of the river's 

 course where nine rapids occur, in the provinces of Batn-el-Hadjar, 



* Russegger, Reisen, Bd. i., 258. 



