3 g6 SCIENCE PROGRESS. 



the line of oases of Upper Egypt, where it ends abruptly 

 in a steep escarpment looking southwards. The belt of 

 comparatively low and fertile country in which the oases lie 

 is made of Cretaceous beds, and stretches in a general 

 W.N.W. direction from a point some distance west of 

 Assuan. South of the oases the ground again begins to 

 rise, and forms a second undulating plateau which extends 

 southwards far beyond the boundary of Egypt. 



The geological structure on the west side of the Nile is 

 very simple. The formations succeed each other in regular 

 order from south to north, and it is clear that there is a 

 general dip towards the north. But this general simplicity 

 is complicated by various minor anticlinal and synclinal 

 folds, which Lyons (16) has attempted to reduce to a 

 system. The evidence in such a region as the Libyan 

 Desert is necessarily incomplete, but he points out that 

 the principal wells occur along certain lines which run 

 approximately from W.N.W. to E.S.E., nearly parallel 

 in fact to the line of the Upper Egyptian oases. He 

 shows, too, that in one case the line coincides, for a part 

 of its course at least, with an anticlinal axis ; and he comes 

 to the conclusion that the other lines also are probably anti- 

 clines. 



He does not find these lines upon the Eocene plateau, 

 where, indeed, there are no wells ; but he believes the 

 Farafra and Baharia oases to be upon an anticlinal axis 

 crossing the others nearly at right angles. 



The physical structure of the Arabian Desert is much 

 more complicated. West of a line joining Suez with Kena 

 there is another plateau of Eocene rocks, which is, however, 

 much more cut up by valleys than the Libyan plateau. 

 The most interesting, geologically, of these valleys is the 

 Wadi Araba, which lies between the Northern and Southern 

 Galalas, and opens into the Gulf of Suez about latitude 

 29 N. 



East of this plateau there is a mountain chain which 

 runs nearly parallel to the Red Sea, and consists of a central 

 core of crystalline and schistose rocks, flanked on each side 

 by Cretaceous and later deposits. 



