2C(i Reviews — Geology of S.E. Egypt. 



have undergone. The valley of Glen Tilt, of which an illustration is 

 given in the frontispiece, is a pre-Glacial gorge 1,000 feet deep in 

 places, and of extreme straiglitness owing to erosion along the shatter- 

 belt of a fault. During the period of maximum glaciation, ice-sheets, 

 one from the far west and one that took a westerly or south-westerly 

 direction from the Cairngorm range, became confluent for a time. 

 Valley glaciers were formed later on. The effects of erosion during 

 the Glacial epoch are best seen in the higher glens and corries, and in 

 over-deepened valleys with bordering hanging valleys and waterfalls. 

 A good view is given of a high-level corrie-tarn, Loch Coire an 

 Lochain, which is held, up at an elevation of 3,250 feet by the 

 terminal moraine of the corrie-glacier. 



There is no chapter on economic deposits, but there appear to be 

 none of much importance. Mention is made in the course of the 

 memoir of the honestones and. the cairn<;orras that were formerly 

 worked, also of the peat. It is noted by Mr. Barrow that " a feature 

 of the liynack peat is the great number of roots of fir-trees met with, 

 which are seen protruding from the wasting edges of the peat along 

 the stream banks. In this ground there are three tiers of these fir- 

 roots rising one above the other ; when dried they form a valuable 

 fuel, as they burn like a candle, and in old days were actually 

 used for that purpose". Splinters have similarly been used in 

 Sutherlandshire. 



A bibliographj' forms the concluding pai't of the memoir, and it 

 may be added that the map is clearly colour-printed and in all respects 

 excellent. 



II. — Geology of Egypt. 

 The Geography and Geology' of South-EastkflN Egypt. By J. Ball, 

 Ph.D., D.Sc. Survey Department, Cairo, Egypt. Government 

 Press, Cairo, 1912. 4to ; pp. xii 4- 394, with 27 plates and 

 62 text-illustrations. Price 40 piastres. 



IT rarely happens that circumstances admit of a desert region being 

 accurately mapped and st.udied in detail, since the economic 

 importance of such parts of the world is usually very small. It is 

 therefore fortunate for geologists and geographers that the demand 

 for prospecting and mining licences in the south-eastern desert of 

 Egypt, which arose about eight years ago, led to a survey which 

 otherwise might never have been undertaken. A considerable 

 number of points had to be located with such accuracy that the 

 boundaries of any concessions which might be granted could be 

 defined without the possibility of any ambiguity ; at the same time 

 as good a topographical and a geological survey were required as 

 could be provided under the prevailing conditions. In the course of 

 three winter seasons (1905-S), representing twenty-two months of 

 field-work. Dr. Ball completed this work, and the results are presented 

 in the volume before us. It is a notable contribution to the geology 

 of North Africa, and one which presents many points of interest. 

 All existing maps of the area were on small scales and of very inferior 

 accuracy, so that a new survey covering about 22,000 miles has been 

 carried out, and the i-esults are given in an orographical map on the 



