146 DR. W. P. HUME ON SECULAR OSCILLATION IN EGYPT [Feb. I9II, 



Series of the Middle Eocene : namely, from the base, (a) Nummulites- 

 gizehensis Zone, (0) Gryplicea-pharaonum Zone, and (y) Gisortia 

 Limestone, the last-named being also of far wider extent and 

 importance than had hitherto been suspected. 



VS. In the Upper Moqattam division of the Middle Eocene the 

 Turritdla Beds near the base, and the strata containing Carolia 

 placunoides and Plicatula polymorpha, are of wide range; beds of 

 detrital materials become of much importance ; and nummulites 

 cease to form part of the fauna. 



14. The increasing importance of the detrital materials is shown 

 by the Calcareous Grits, which have a wide extension in the 

 North- Western Desert of Egypt, but differ in character from the 

 mammaliferous beds of the Eayum, which are conspicuous by their 

 brilliant colouring and by their sandy character. Their precise 

 age-relations are uncertain, as they have hitherto not yielded fossil 

 remains of decisive age. 



15. The quartz-chert gravels forming the surface of the highest 

 desert between Baharia and the Eayum are unconformable to the 

 Calcareous Grits, though closely related to them as regards dis- 

 tribution, the suggestion that they are of Oligocene age being based 

 on Dr. Blanckenhorn's analysis of certain freshwater shells obtained 

 in them by Mr. Beadnell. The rounded character of the quartz- 

 and-chert gravel and the presence of fossil wood bear witness, in 

 conjunction with the occurrence of great land-mammals, to the in- 

 coming of continental conditions at the close of the Eocene Period. 



16. This continental phase is accompanied by many indications 

 of volcanic activity, for to this period belong the dolerites of Baharia, 

 various basaltic occurrences in the Western Desert, the Eayum, and 

 at the well-known quarries of Abu Zabel, near Cairo. Interesting 

 examples of a similar nature have been recorded from the Eastern 

 Desert, one of the latest of these being some remarkable intrusions 

 through the Danian and Eocene rocks which I observed at the head 

 of Wadi Urn Hemaiet, near Wadi Qena. 



The Cretaceous Period in Egypt is, therefore, one in the main 

 marked by the gain of sea over land ; during the Eocene, on the 

 contrary, the land appears to have been steadily gaining on the 

 sea, probably concurrently with gentle fold-movements, which 

 account for the minor differences in the nature of the Eocene 

 deposits. At the close of Eocene times, and during the Oligocene 

 Period, the approach of a continental phase is clearly indicated. 



EXPLANATION OF PLATE VI. 



Sketch-map, on the scale of 1 : 6,000,000, showing the extension of the 

 Eocene and Oligocene strata in Egypt. 



Discussion. 



Mr. A. Wade said that, so far as his personal knowledge of the 

 geology of Egypt was concerned, he was in agreement with the 

 conclusions drawn by the Author. The correlation of the almost 



