476 Revieics — BeadnelVs Egyptian Oasis. 



The highest and earliest beach or shore-line has an ascent of about 

 a foot per mile toward the north-north-east ; the lower and later shores 

 ascend less ; and the lowest shore, marked by beaches only 60 to 70 feet 

 above Lake Winnipeg, are almost perfectlj' horizontal. It is thus 

 known that the land was being uplifted differentially while Lake 

 Agassiz existed, and that the uplift was nearly completed before the 

 ice-sheet was wholly melted away. 



The chief cause of the uplift is thought to be the unburdening of 

 the land by the removal of the vast weight of the ice-sheet, this part 

 of the earth- crust being restored to equilibrium or isostasy by an 

 inflow of the plastic magma at a great depth within the earth, which 

 took place during the time of departure of the ice. 



Measures of the shore erosion and beach accumulation indicate that 

 the duration of Lake Agassiz was only about 1000 years; and from 

 the rate of recession of the Falls of St. Anthony, forming the gorge 

 of the Mississippi River between Fort Snelling and Minneapolis, the 

 length of the Post-Glacial period is estimated to be between 6000 and 

 10,000 years. 



I. — An Egyptian Oasis: an account of the Oasis of Khaega in the 

 Libyan Dksert, with special keference to its History, Physical 

 Geography, and Water-Supply. By H. J. Llewellyn Beadnell, 

 F.G.S., etc. 8vo; pp. xiv, 248, with 28 pictorial plates and 

 4 maps and sections. London : John Murray, 1909. Price 

 10s. 6c(. net. 



AYERY interesting account of the "Flowing Wells and Sub- 

 Surface Water in Kharga Oasis", accompanied by map, section, 

 and view of one of the wells, was contributed by Mr. Beadnell to the 

 Geological Magazine for February and March of last year. The 

 author has now published in full his researches on the history and 

 physical features of this extensive and remarkable oasis. 



The oases of the Libyan Desert appear to have been inhabited from 

 early prehistoric times, as flint implements of Palaeolithic type occur 

 on the margins of the plateaus that border the oases, and also within 

 the depressions. Although at Kharga no natural outflow of water 

 now occurs on the floor of the oasis, the author considers it probable 

 that in those early times there may have been some natural springs, 

 which escaped through fissures and attracted attention. Many ancient 

 wells 120 metres in depth continue to flow now, though for the most 

 part the yield has diminished. It is not known when the flowing 

 wells were first made, but it has been ascertained that during their 

 occupation of the country the Romans largely developed the water- 

 supply, cutting underground tunnels of great length in solid rock with 

 numerous air-shafts in the ' surface-water sandstone '. 



As the author dealt with the geological structure of the region in 

 the article before mentioned, we need not further refer to this part of 

 the subject. With regard to the origin of the oasis, he finds no 

 evidence of fluviatile erosion, nor of local subsidence. Tectonic 



