238 me. a. wade on the [May 19 1 1, 



7. Some Observations on the Eastebn Desert of Egypt ; ivith 

 Considerations bearing upon the Origin of the British Trias. 

 By Arthur Wade, B.Sc, A.R.C.S., F.G.S. (Bead March 22nd, 

 1911.) 



[Plates XIII-XVI.] 



Contents. 



Page 



1. Introduction 238 



II. The Igneous ' Gravels ' and Pebble-Beds 238 



III. Origin of the Igneous ' Gravels ' 239 



IV. The Sandy 'Gravels' 241 



V . Parallels in Trias and Permian 241 



VI. Distribution of Pebbles 242 



VII. Sands and Marls 244 



VIII. Effects of Wind-blown Sand 248 



IX. Origin of the Sand 250 



X. Salt and Gypsum 251 



XL Comparisons * 259 



XII. Summary and Conclusion 260 



I. Introduction. 



V 



During the past two years j[ have on several occasions visited that 

 part of the Eastern Desert of Egypt which borders the Bed Sea 

 near its junction with the Gulf of Suez. While there I made 

 observations of desert conditions and phenomena which appeared 

 to me to be of interest to the student of the conditions determining 

 the origin of the Triassic rocks of Britain. 



A few years ago the late «T. Lomas l dealt very fully with these 

 conditions, having made some studies of South African and Egyptian 

 deserts, and it is with pleasure that I find myself able to confirm 

 or to supplement several of the conclusions to which he came. 



II. The Igneous ' Gravels ' and Pebble-Beds. 



The western side of the Bed Sea is flanked by a wall of hills 

 running generally in lines parallel with the general trend of the 

 coast. They rise abruptly from a level or gently sloping coast- 

 plain, which varies in width from under 1 to over 10 miles. The 

 hills are composed chiefly of igneous rocks : red and grey granites, 

 dark andesites and purple porphyries, with some tracts of gneiss 

 and schist. 



At the foot of the hills, large mounds of angular debris of the 

 igneous rocks occur, running in tongues from the hills out on to 

 the plain, or forming low foot-hills which run parallel with the 

 main range. 



1 'Desert Conditions & the Origin of the British Trias' Proc. Liverp. 

 Geol. Soc. vol. x, pt. 3 (1906-1907) pp. 172-97. 



