part 21 PROCEEDINGS OF THE aEOLOGlCAL SOCIETY. XCvll 



deposits (such as conglomerates and clays), and then by lagoon 

 formations (gypsum and salt). The earliest of these formations 

 appear to have been of Schlier (Middle Miocene) age. 



(7) Tlie sequence of events from Middle Pliocene times onw^ards 

 is difficult to unravel. The whole region of the Clysmic Gulf 

 became folded and fractured to a remarkable extent, there being 

 certain underlying elements of order discernible. There is strong- 

 faulting at the borders with the igneous hills, and fold-ranges are 

 well marked, these being of asymmetrical anticline type. It is 

 suggested that compression of the area, with uplift of portions of 

 it, offers the best solution for the facts observed. It seems difficult 

 to conceive that dislocation so marked, spread over so wide an area, 

 could arise under rift formation as defined by Prof. J. W. Gregory. 

 It seems equally difficult to ascribe the whole of the surface- 

 differences to erosion alone. It will be readily understood that no 

 simple solution of the problem can be offered on the evidence at 

 present available, especially in view of the fact that no important 

 faulting has been noted on the western borders of the Red Sea. 



(8) The same reserve must be exercised with regard to the very 

 interesting eroded trough-fault vallej^s, which the writer formerly 

 regarded as of rift origin. 



(9) A suggestion is made that the portion of the Nile Valley 

 about lat. 26° N., where faulting is most consj^icuous, may have 

 been initiated by erosion of a sharp anticlinal fold due to the com- 

 pression of almost horizontal strata. Sharp folds exist in the 

 desert east of the Nile, but their origin is at present doubtful. 



Discussion'. 



The President said that it had been customary of late years 

 to devote at least one meeting in the Session to a lecture on some 

 subject of interest to geologists, or to a discussion of one of the 

 larger and more speculative problems of geology. The subject 

 selected for discussion that evening might be briefly defined : there 

 was in Central Africa a well-known surface-feature, for which 

 Prof. J. W. G-regory had popularized the name of the Great 

 Rift Valley; there was also, in Southern Syria, a similar surface- 

 feature, occupied in its northern part by the Jordan Valley, and 

 continued as a surface-depression to the Gulf of Akaba. According 

 to one school of thought, these two surface-features were not only 

 of similar genesis, but formed the extremities of a continuous 

 surface-feature, intimately related in origin to the tectonics of the 

 surface-rocks, called the African Rift Valley, of which the 

 Red Sea was regarded as an integral and important section. 

 According to another school, no such continuit}^ is recognized, and 

 the origin of the Red Sea is attributed to causes other than those 

 which gave rise to the rift-valleys of Africa proper and of Pales- 

 tine. Dr. Hume had had a large personal experience of the 

 geology of the Red-Sea region, and his presence in England 

 afforded a useful opportunity of raising a discussion of this im- 

 portant and interesting problem. 



