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 height, 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, Sukkot, and Dar-el-Mahass, where the river flows over granite and other plutonic rocks; gneiss, mica-schist, and other hard rocks, which Russegger considers to be metamorphic. But between Semne and the head of the second cataract at Wadi-Halfa, there is not a continuous rapid stream; for Hoskins says, that about two miles above that cataract, the river has a width of a third of a mile, and, when he passed it the water was scarcely ruffled.[60] Footnote 60: Travels in Ethiopia, p. 272. From the rapid of Hannek to Abu Hammed, the distance is 329 English miles, and the difference of altitude is 246 English feet. We have thus an average fall in that distance of 9·00 inches in a mile. Thus, in the 776 miles between Abu Hammed and Philæ, we have an average fall of the Nile Of 9·00 inches in a mile, for a distance of 329 miles. Of 13·12 ......... ......... 236 ... Of 5·30 ......... ......... 96 ... Of 12·00 ......... ......... 115 ... _Of the Breadth, Depth, and Velocity of the Nile, in Nubia._