330 Reports and Proceedings — 



amount of information, more or less geological. Starting from 

 Kuldja, after a visit to Lake Issik-kul, be crossed the Thian Shau 

 Chain by a glacier pass — the Muz-davan — which is probably from 

 11,000 to 12,000 feet above the sea, and never before had been 

 completely traversed by a European. Thence he made his way 

 to Kashgar and Khotan in Chinese Turkestan, and finally crossed to 

 Leh by the Kilian, Suget, Kai'akoram, and Saser Passes. All these 

 are more than 17,000 feet above the sea-level, the Karakoram being 

 18,550 feet. The chief points of geological interest in the book 

 are accounts of a severe earthquake at Yierny, near the Ala-tau 

 Mountains, and of the geology of Eussian Turkistan, compiled from 

 Eomanovsky and Musliketoff's map, and the descriptions of the 

 high passes over which his journey lay. Unfortunately the exigencies 

 of travel prevented Dr. Lansdell from forming a collection of rock- 

 specimens, but from his own observations, and by availing himself 

 of Eussian writings, he is able to give some notion of the geology, 

 and stil] more of the geography, of Turkestan and the bordering 

 mountain chains. The book, in short, will be a valuable work of 

 reference on districts which, till lately, were practically inaccessible 

 to Europeans. 



I.— May 23rd, 1894.— Dr. Henry Woodward, F.R.S., President, 

 in the Chair. The following communications were read : — 



1. " On the Stratigraphy and Physiography of the Libyan Desert 

 of Egypt." By Captain H. G. Lyons, E.E., F.G.S. 



The Nubian sandstone, wherever seen, rests unconformably on 

 the old rocks called by Sir J. W. Dawson Archsean, and the author 

 finds no case of alteration of sandstone by these rocks, though in 

 one case it is altered by an intrusive dolerite. 



The author considers the Nubian sandstone to be an estuarine 

 deposit which was formed on an area afterwards gradually invaded 

 by the Cretaceous sea. He considers the whole of the sandstone in 

 the region which he has examined to be of Cretaceous age. 



He describes a series of anticlinals, one set running W.N.W. — 

 E.S.E., and the other N. by E. and S. by W. Many springs of the 

 oases seem to occur along these anticlinals, owing to the beds which 

 contain the water being brought nearer to the surface. Historical 

 evidence is discussed which points to the Nile having reached a 

 higher level in Nubia than it does at present, and it is suggested 

 that variations in the level of the river were caused by earth- 

 movement opposing obstructions to the river's flow. 



The sandstone of Jebel Ahmar near Cairo is described, and 

 its occurrence over a wide area of west Cairo is recorded. The 

 author considers its age to be later Miocene. He believes that, 

 with the exception of some erosion after the deposition of the Eocene 

 beds, the greatest erosion, including the cutting out of the Nile 

 Valley, took place in Miocene times, while a certain amount, bringing 

 the area to its present condition, was done in Quaternary times. 



