518 Notices of Memoirs — Climatic Changes in N.E. Africa. 



if Kinieridgian fossils had been discovered, for the Kimeridgian was 

 not a period of deposition in the Caucasian area but one of earth- 

 movements and folding of strata. It is one of the sharpest distinctions 

 between the stratigraphy of the two slopes of the Caucasus that 

 whereas on the south slope the interruption takes place only after the 

 Sequanian and lasts until the Neocomian, on the north slope on the 

 other hand Tithonian beds are well developed and rest discordantly on 

 Lower Sequanian. 



II. — The Glacial Period and Climatic Changes in North-East 



Africa. 1 



By W. F. Hume, D.Sc, F.K.S.E., and J. I. Craig, M.A., F.R.S.E. 



1. Southerly Shift of the Wind-systems in Glacial Times. — The effect 

 of the seasonal decrease of temperature in the Northern Hemisphere is 

 to cause a seasonal displacement of the system of westerly moist 

 winds southwards by several degrees, and not improbably decrease of 

 temperature below its normal is also associated with a similar dis- 

 placement. It is inferred that the decrease of temperature of the 

 Glacial Period would be correlated with such a displacement of 

 the westerly winds, which now barely touch the north coast of Egypt 

 in the winter, that they would impinge on the loftiest portion of the 

 Bed Sea mountain range. 



Geological and topographical evidence points conclusively to the 

 existence of such a westerly moist current at no very distant period. 

 The current was westerly, for the principal erosion occurred on the 

 western slopes, and this erosion is evidenced by the gravel terraces, 

 which attain a remarkable development near the town of (Jena. 

 These consist of materials which could have come only from the 

 highest portion of the Ped Sea Hills, distant some 40 to 50 miles to the 

 east or north-east. The precipitation was most active where the range 

 is highest, and decreases towards the north where the mouutains 

 are lower. The decrease towards the south is to be attributed more 

 probably to an approach to the southern limit of the moist current. 



Further evidence of such a westerly current is to be found in the 

 existence of calcareous tufas on the border of the eastern scarp of 

 Kharga Oasis and elsewhere, and that the temperature was then 

 several degrees colder is shown by the presence in the tufas of leaf- 

 fragments of Quercus ilex and other plants which do not now flourish 

 south of Corsica and Southern France. 



2. Change in Monsoon Effects during the Glacial Period. — There is 

 evidence of the enormous development of glaciers over Ruwenzori. 

 Mount Kenia, Kilimanjaro, and the Himalayas, during the Glacial 

 Period. The recession of the glaciers in East Africa indicates that the 

 temperature there is now about 10° to 12° E. warmer than during the 

 period of maximum glaciation. 



It is known from the investigations of the Meteorological Depart- 

 ment of India tlntt an increased snowfall on the Himalayas in spring 

 exercises a measurable prejudicial effect on the Indian monsoon at the 



1 Read before Section C (Geology), British Association, Portsmouth, 

 September, 1911. 



