Notices of Memoirs — H. J. L. Beadnell — Gcologij of Egypt. 27 



land in late Tertiary times, denudation must have gone on con- 

 tinuously over the whole surface of the country. 



" The most important denuding agent at the present day in the 

 Libyan desert is wind-borne sand, the erosive action of which is 

 very powerful and at once apparent to eveiy traveller in these 

 regions ; but in the past there may have been, and probably were, 

 other eroding agencies as well at work on the surface of this part of 

 North Africa. Imagine, then, the general planing down of the 

 country little by little through a long interval of time, until the 

 anticlinal ridge of Cretaceous beds was reached, with its attendant 

 soft sandstones and claj's. As soon as the latter were exposed the 

 action of denudation would have rapidly quickened, chiefly by the 

 breaking up of the constituents of these beds by changes of tempera- 

 ture, rains and frosts, and the removal of the resulting sand and 

 dust by wind. In this way must these wonderful depressions have 

 been formed. 



" Generalizing, then, we may say that where there have been 

 extensive deposits of soft beds, and these have become exposed b}^ 

 the action of denudation, there large depressions have been cut out. 

 The existence of soft Cenomanian sandstones and clays is thus the 

 primary cause of the existence of the depression of Baharia, the soft 

 Esna shales have played a similar role in that of Farafra, while, 

 again, Dakhla is cut out in a thick series of soft beds of Danian age. 

 The other oases and depressions probably owe their existence largely 

 to the same cause." 



Farafra and Dakhla Oasis. — In Farafra the author's chief additions 

 to our knowledge were rather geographical than geological, although 

 some evidence is brought forward to show that the very fossiliferous 

 clays on the road between Farafra and Dakhla are somewhat younger 

 than the age assigned to them by Zittel. 



In Dakhla oasis thick and extensive highly phosphatic bone-beds 

 of considerable commercial value were discovered. 



Fayum. — It was in this province that there existed, some 2,000 

 years before Herodotus, the celebrated Lake Moeris, the exact site 

 of which has led to so much discussion. The author shows that 

 the geological evidence, in the shape of clays with numerous fresh- 

 water shells and fish-remains, of the same species as those at present 

 inhabiting the existing lake, proves that the ancient lake occupied 

 the lowest part of the depression, i.e. that now occupied by the Birket 

 el Qurun and a considerable area of the low surrounding country. 

 His position, in fact, closely agrees with that assigned to the lake by 

 Major Brown, who bases his conclusions chiefly on considerations 

 of level. 



An extensive series of fluvio-marine beds, with intercalated sheets 

 of basalt near the top, is shown to overlie the Upper Mokattam 

 formation throughout the north part of the Fayum. This series is- 

 provisionally regarded as Oligocene. At the top come the silicified, 

 wood- bearing sandstones, which stretch northwards across the desert 

 to beyond the latitude of Cairo. 



Within the Fayum depression, high up on the slopes or summits- 



