204 Br. W. F. Hume — Qeologij of Eastern Sinai. 



a thick series of white sands, which are now cut deeply into by 

 ravines, giving rise to battlements and castellated ridges, sometimes 

 over 100 metres high, forming one of the most striking features on 

 the road from Sinai to Akaba. These are based on a series of 

 variously coloured ferruginous sandstones, forming broad, low, 

 smooth plateaux, themselves resting on a planed-down surface 

 of granite. Unfortunately these sands and sandstones are all 

 unfossiliferous. 



The thicknesses in Jebel Gunnah are as follows : — 



metres. 

 Compact limestones, -with few fossils ... 100 



Striped Cenomanian marls 20 



Sands and sandstones ... 207 



Total thickness ... 327 (over 1,000 feet). 



The most important points noted are: — (1) The Nubian sandstones 

 resting on a planed-down surface of granite; (2) the Cenomanian 

 beds belong to Professor Zittel's ' Africano - Syrian ' series, which 

 since Mr. Beadnell's discovery of these beds in Baharia Oasis are 

 shown to have an enormous extension north of latitude 28° N., 

 while Dr. Schweinfurth has shown them to be of great thickness to 

 the north of the Red Sea Hills ; (3) the dip and present position 

 of the beds show that these strata once extended over the whole of 

 the present igneous mountain region; (4) the Carboniferous sand- 

 stones of Western Sinai are apparently absent. 



Y. The Igneous Eocks of Eastern Sinai. — After a brief 

 general description this portion of the paper lays stress on the 

 importance of dyjfes of every petrographical variety, which, though 

 the youngest members of the igneous series, never pass into the 

 Nubian Sandstone, so that thej'^ are at least Pre-Cretaceous. While 

 generally trending N.N.E. and S.S.W., there is frequently a second 

 system, running practically at right angles to this direction. Though 

 in general aspect resembling the mountains on the opposite side of 

 the Red Sea, the fundamental rocks of the central axis of the 

 peninsula are granitoid gneiss and hornblende-granite, not the red 

 granite which forms many of the main summits in the Eed Sea 

 Hills. The latter is, however, also widely distributed in the 

 peninsula itself. 



Of special interest are beds of andesite, tuff, and agglomerate, 

 which form some of the principal summits, capping the granite and 

 gneiss, while in the Ferani range, etc., this Volcanic series is closely 

 associated with a metamorphic type, varying from spotted slates and 

 slightly foliated mica-schists to dark-green chlorite and hornblende- 

 schists pierced by innumerable dykes of dolerite. Some special 

 points are dealt with in closing, such as the development of gneisses 

 on a magnificent scale in Wadi Um Gerat, the importance of 

 tourmaline-granite in some of the southern summits, the presence 

 of splierulitic felsites forming dykes in many parts of the district, 

 and the probable absence of the basalt recorded near Sherm by 

 Burckhardt. 



