G. W. Grahham — Wells of North- Eastern Sudan. 271 



there is a depth, of over 110 feet of Valley Fill, and good supplies of 

 water are obtained from it at that depth. The total depth of Fill is 

 not known, but in any case it is a great thickness to find close to the 

 waterslied, at an altitude of 2000 feet, in a valley that slopes down 

 to the sea in about 70 miles. 



There are other wells lower down this valley, and at Salom, where 

 the Port 8udan and Suakin branches of the railway divide, it debouches 

 on to the Maritime Plain which separates the hills from the sea. 



Wells are found under the same conditions in practically all the 

 valleys of the Red Sea Hills, such as Khors, Baraka, and Arbat, while 

 the memoirs of the Egyptian Survey ' show that thej' also exist further 

 north. Dr. Ball ^ has given us an excellent account of these Egyptian 

 wells, from which it would appear that the valleys only differ from 

 those of the Sudan in having a less abundant supply of water, and 

 consequentl)' the wells are not as frequent. 



The Avells of Qura, in the loop of the Nile south of Abu Hamed, 

 are examples of another type belonging to arid regions of crystalline 

 rock. Mr. G. S. Laird Clowes^ describes them as situated in a small 

 valley surrounded by granite hills. They are sunk in hard but fairly 

 porous granite, and he supposes that the presence of water is due to 

 the fact that Qura is the common basin into which several wadis drain, 

 and consequently commands any rainfall that may occur over a large 

 area. Wells of this kind are not comparable with those of the E.ed 

 Sea Hills, as they depend partly on the porous nature of the decomposed 

 rock, and thus resemble those of the areas further south, where the 

 country is covered with Cotton Soil. I have not personally seen any 

 wells of this type, but from accounts they appear to be of frequent 

 occurrence. 



The Maritime Plain, though a distinct area, presents conditions 

 related to those of the Valley Fill. It is about 10 or 15 miles in 

 width, slopes gently seawards, and, like the Valley Fill, is composed 

 of detritus brought down from the hills. Borings have been made and 

 show that these deposits attain a thickness of over 1000 feet. The 

 plain is bounded along the coast by raised and modern coral reefs, 

 broken here and there into harbours at points opposite the mouths of 

 big rock valleys. Its surface is traversed by shallow stream-beds, and 

 storm-water from the hills occasionally passes along them and reaches 

 the sea. Here and among the border hills, as already noted, the 

 rainfall occurs in winter instead of during the summer, as is the case 

 in the rest of the Sudan. The underflow from the Valley Fill must 

 all pass through the gravels of the Maritime Plain, and is increased as 

 it flows towards the sea, not only by the local rainfall, but by the 

 flood-waters fi'om the hills as well. The water is tapped by wells at 

 many places, where small supplies of fairly drinkable water are 

 obtained by the natives. Such wells are found close to the sea in the 

 neighbourhoods of Suakin and Port Sudan. 



' Topography and Geology of the Eastern Desert, Central Portion, p. 251 et seq., 

 analyses, p. 293. Preliminary Report on the Geology of the Eastern Desert between 

 Latttndts 22° and 25° N., pp. 15-16. 



- Cairo Scientific Journal, 1908, vol. ii, p. 237. 



^ Cairo Scientific Juxrual (Survey Notes), 1907, vol. i, p. 350. 

 [To be concluded in our next Ktiiiiber.) 



