376 ~ SECTIONAL TRANSACTIONS.— H. 



episodes. This is precisely what Leakey has established on geological evidence in 

 Kenya. In Uganda, Wayland has similarly established two major pluvials and the 

 same can be demonstrated in Rhodesia and British Bechuanaland, where the 

 associated cultural evidence I obtained in 1929 supports and confirms Leakey's 

 evidence in Kenya. 



The African pluvials are preceded and followed by periods of intense desiccation 

 which no doubt compelled great human migrations. If the meteorological hypothesis 

 of the relation of glacials to pluvials is accepted, it follows, from the cultural evidence 

 set out in the chart, that the African representatives of these cultures ante-date those 

 of Europe. The desiccation of the unglaciated regions, which set in when the ice 

 retreated from the glaciated areas, provided the impetus which swept the waves of 

 migration northwards and, with them, the Aurignacian culture into Europe. 



Prof. J. W. Gregory, F.R.S., gave the following account of The Correlation of 

 Pluvial Periods and the German Drifts. 



On the discovery in 1893 of the glaciers of Mount Kenya and of their former 

 extension more than 5,000 ft. below their present level, I inferred from the widespread 

 range of the subalpine flora and fauna of Equatorial Africa, on Kilima Njaro, Kenya, 

 Ruwenzori, in Abyssinia and the Cameroons, and from the presence of the drowned 

 canyon off the Congo, that the climate had formerly been colder and wetter owing to 

 a high pressure area and a greater elevation of the area. The date of the greater 

 glaciation of Mt. Kenya was concluded as ' approximately contemporaneous with 

 that of Europe,' and that the glaciation of Europe ' forced the cyclone-track along 

 the Mediterranean farther south, and thereby gave Equatorial Africa a moister and 

 colder climate.' The glaciation was naturally accompanied by an increased and 

 more widespread rainfall, of which direct evidence was given by various lake deposits 

 in the equatorial part of the Rift Valley. 



The Kenyan glaciation and the deposits of Lake Suess and other extinct lakes 

 indicated pluvial periods approximately contemporaneous with the glaciation of 

 N.W. Europe ; and as these lakes were regarded as having occurred at different dates 

 they indicate more than one wet period. 



The correlation of the variations in the extent of the glaciers and in the amount 

 of the rainfall in Equatorial Africa with those in N.W. Europe raises questions of 

 interest to anthropology, geology and meteorology. That major variations in the 

 European climate would have affected that of Northern Africa is obvious ; and in 

 1914 I adopted the view that the pluvial period of Palestine and C3Tenaica was due 

 to the southward diversion of the low pressure systems by the European ice-sheets ; 

 and those countries may serve as the link for the correlation of the climatic variations 

 of Central Europe and Central Africa. 



The possibility of the precise correlation of variations in rainfall in E. Africa and 

 the British Isles depends on whether the changes in the European glaciation were 

 sj'nchronous. Some direct evidence and the extreme uncertainty in the correlation 

 of European glaciations, interglacial periods, and dry periods marked by beds of 

 loess, suggest that the glaciations waxed and waned independently at different 

 centres. 



Prof. Boswell points out that even in the British Isles different areas were glaciated 

 at different times and that the suggested correlations of the British and the Alpine 

 glaciations are doubtful. If the increase in the glaciers of Britain and the Alps had 

 been synchronous, the corresponding variations in N. Germany should have been 

 also simultaneous. But the efforts to correlate the German and Alpine glaciations 

 have so far been unsuccessful. Dr. C. Gagel states : ' I hold it impossible, with our 

 present knowledge, to extend the Penck-Briickner classification to N. Germany ' ; 

 and his conclusion is still valid. Obermaier remarks the different conclusions based 

 on the N. Germany and Alpine deposits. Wohlstedt correlated the Baltic End- 

 moraines with the Wurm, but declined to make any more detailed correlation with 

 the Alpine succession. 



The difficulty in the correlation of glacial deposits even in a country of exceptionally 

 uniform character is shown by the uncertainty in the classification of the major 

 divisions of the N. German drifts. It is still uncertain how many times that country 

 was glaciated. Thus, E. Geinitz, the champion of ' mono-Glazialismus,' believes in 

 one glaciation with ten stages of retreat. Beyer (1927) advocates two glaciations ; 

 K. Beurlen (1927), three glaciations ; W. Wolff, three or four ; Van Werveke, adopts 

 three for Magdeburg district, but says there was an older one elsewhere and that there 



