Vol. 67.] EASIKRN DE8EET OF EGYPT. 239 



The mounds themselves consist of unsorted angular blocks and 

 flakes varying greatly in size, and showing as a rule no signs of 

 stratification where cut through. The rocks of which they are 

 composed arc always similar to those of the igneous range nearest 

 to which they rest. 



The mounds contain very little sand, and such as is present has 

 obviously been introduced by the subsequent action of wind. 

 Measurements taken by means of the aneroid showed that these 

 mounds rose abruptly from the coast-plain just below the 100-foot 

 contour, and that their summits, as a rule, varied in height between 

 120 and 160 feet above sea-level. 



The mounds and ridges of igneous debris flank the eastern 

 slopes of the hills throughout their length; and, when viewed from 

 a distant position, they are seen to be remarkably even in height 

 and to be of the nature of a platform or terrace, broken in places 

 by wadis and gullies (see PI. XIII). 



In dealing with the geology of the Eastern Desert, the late Mr. 

 Barron remarked that 



' the plains east of the Red Sea Hills are largely formed by gravel ridges 

 extending from the mountains, and composed of materials derived from them 

 or from the lower parallel ranges. . . .' ] 



It is a remarkable fact that these ' gravel ' - mounds 2 show their 

 greatest development where the hills are unbroken. Wherever 

 gullies or wadis occur, they are either cut through or else they 

 are entirely absent (loc. cit.). On the south side of the Gulf of 

 Jemsa a large area is covered by mounds of this material, separated 

 from the hills by a narrow sandy depression. 



III. Origin of the Igxeotjs ' Gravels.' 



In the work cited, the Egyptian Government Surveyors say very 

 little with regard to the origin of these mounds of ' gravel' on the 

 eastern side of the lied-Sea Hills, although they express opinions 

 with regard to the igneous ' gravels ' that are found on the 

 western side of those hills and in the Nile Valley, which show 

 important differences and associations/ 5 



The hills are covered with angular fragments of all sizes, 

 produced by the forces of disintegration common to such regions. 4 

 The mounds in question are not, however, of the nature of screes. 

 True screes do occur on the hills, but they were not usually connected 

 intimately with the igneous 'gravels.' As a rule, the 'gravels' 

 are separated from the hills by a narrow depression partly filled 



1 T. Barron & W. F. Hume, ' Topography & Geology of the Eastern Desert of 

 Egypt: Central Portion ' Egypt. Geol. Surv. Rep. 1902, p. 126. 



- The terra 'gravel' has been used very largely, in connexion with these 

 beds, by Egyptian geologists. For that reason 1 have retained it. 

 1 .Barron & W. F.Hume, op. cit. pp. 128-.m 



See J. Walther, ' Daa Gesetz der YVustenbildumx in Gegenwart & Vorzeii ' 

 Berlin, 1900. 



Q. J. G. S. No. 200. E 



