Vol. 50.] STRATIGRAPHY OF THE LIBYAN DESERT. 531 



34. On the Stratigraphy and Physiography of the Libyan Desert 

 of Egypt. By Capt. H. G. Lyons, R.E., F.G.S. (Read 

 May 23rd, 1894.) 



[Plate XXI.— Map.] 



Contents. 



Page 



I. General Description 531 



II. The Nubian Sandstone 533 



III. The Cretaceous and Eocene Strata 534 



IV. The Miocene and Pliocene Strata 535 



V. The Anticlinal Folds, and their Relation to the Water-supply 537 



VI. The Erosion of the Nile Valley, etc 541 



VII. The Origin of the Silicified Wood 545 



I. General Description. 



The work of Geheimrath Karl A. von Zittel, 1 as a member of the 

 Rohlfs Expedition of 1874, has furnished us with an accurate 

 geological description of the western oases of Egypt, which we can 

 use as a starting-point for the further exploration of the Libyan 

 Desert to the north and south of them, and his detailed sections and 

 lists of fossils are of invaluable assistance in correlating the strata 

 met with in various parts of this area. 



Still, I cannot find that much has been done since Dr. Zittel's 

 work except by Dr. Schweinfurth, Sir J. W. Dawson, Prof. Hull, 

 Prof. Walther, Prof. Mayer-Eymar, and Mr. E. A. Floyer in the 

 Eayum, the Nile Valley, and various parts of the eastern desert, 

 while the western desert seems to have remained almost unexplored. 



In December 1893 and January 1894, when on a patrol visiting 

 the oases of Kharga and Dakhla, and the desert routes to the south 

 of them, I had opportunities of making a few observations in this 

 portion of the desert which are, I venture to think, of some interest. 



These I have more recently (April 1894) been able to amplify by a 

 ride through the more northern part of this western desert, the 

 route followed being from the pyramids of Giza to Der Macarius, 

 the easternmost monastery in the Wadi Natrun or the Valley of 

 the Natron Lakes ; thence along the valley some 20 miles to Der 

 Baramus, the westernmost of the four Coptic monasteries. Erom 

 this point I turned S.S.AV. and went as directly as possible to the 

 northern end of the Baharia Oasis, thus traversing an area shown 

 as geologically unknown in Dr. Zittel's ~ map. Erom this oasis I 

 returned to the Nile by almost the same road as that traversed by 

 Prof. Ascherson 3 in 1876. 



South of the oases of Kharga and Dakhla, the part of the desert 

 traversed is included between two lines, each about 100 miles long, 

 drawn southward from these oases and following the old trade 



1 ' Palaaoutographica,' vol. xxx. (1883) p. 1. 



2 Ibid. map. 



3 Mitth. geogr. Gesellsch. in Hamburg, 1876-77. 

 Q. J. G. S. No. 200. 2 r 



