SECTIONAL TRANSACTIONS.— H. 385 



equatorial belt of low pressure ^\hich receives tlie trade winds. Hence, there are 

 several meteorological reasons for correlating pluvial with glacial periods ; we may go 

 further and say that the glaciation of high mountains within the tropics was probably 

 due more to increased precipitation than to lower temperature. 



The three interglacials represented in Penck and Briickner's Alpine scheme do not 

 seem all to have had equal importance. It is generally supposed that the second, the 

 Mindel-Riss, was several times longer than the first and third, and Dr. Simpson believes 

 that its character was entirely difl'erent. At least it is reasonable to assume that 

 where fewer than four glaciations were developed the reduction was in some cases 

 caused by the merging of either the Giinz and Miudel, or the Riss and Wiirm, or both. 

 Investigation of ' pluviated ' regions generally shows only two pluvial periods of 

 I'leistocene age, and I think that the best correlation that can be made on meteorological 

 grounds at present is to equate the first plu^^al with the Giinz and Mindel, the second 

 with the Riss and Wiirm. 



Prof. G. B. Baebour, speaking about northern China, said that the apparent 

 Pleistocene sequence there was two periods of aridity with accumulation of loess 

 separated by a period of relatively moist conditions. Prof. Barbour thought the loess 

 periods could be correlated broadly with the main glacial periods. 



Mr. L. S. Camivoade said that the N.E. monsoon of the Coromandel coast and 

 Eastern Ghats could not at any time have been much heavier than now. There seems 

 to have been one long major pluvial period in the Pleistocene along the east coast of 

 India with formation of laterite, which demands an alternation of moist and dry 

 seasons, both warm. The decay of laterite began at a very remote period archaeo- 

 logically and apparently it was only then that man appeared. 



Prof. A. E. Douglass gave an illustrated account of the method of investigating 

 tree-rings as a key to past climatic changes. At present we cannot date rings beyond 

 a fairly recent period, but opportunities should be taken for foUovsing possible 

 extensions of this method into remoter periods. 



The Chairsian in summing up said that there would be general agreement with both 

 Prof. Gregory and Prof. SoUas that one could go seriously astray in trying to make 

 correlations too detailed, while one could also miss the major truths by timidity in 

 refusing hypotheses of correlation altogether because of difficulties about details 

 which were likely to be regional peculiarities. 



It was interesting to note the -widespread tendency to identify an earlier and a 

 later ice age separated by a long interglacial period, and themselves subdivided into 

 episodes. Prof. Solch's statement that continental opinion was generally in favour 

 of identifying the Hotting breccia as belonging to the Mindel-Riss interglacial was 

 important because, if this opinion maintains itself, it suggests the need for a large 

 modification of the clever and interesting theory of Simpson. Prof. Solch's reminder 

 of the trend of continental opinion towards the acceptance of the idea of an uplift 

 of about 500 m. in one of the later phases of the Pleistocene Ice Age was also useful, 

 as the importance of orographical changes had been rather overlooked in some 

 recent discussions. If orographical changes of this magnitude did occur, it was 

 probable that some estimates of time involved in glacial phases would need serious 

 revision. 



The general agreement of Miss Gardner, Mr. Leakey and Mr. Armstrong concerning 

 two major pluvial periods in Africa with a relatively dry period in between was 

 interesting, even if Dr. Sandford could not agree, as it illustrated the same trend of 

 opinion as that found among European workers. It also reinforced the a priori 

 correlations of glacials and pluvials. 



The evidence from China and India was also most interesting, as it suggested a 

 scheme dovetailing with that of two major glacial periods and one interglacial. 



There were endless difficulties still to be met, but the discussion showed a wide- 

 spread movement towards a broad agreement, and the exchange of views would, it 

 was hoped, help field observers to notice relevant points in the course of their work. 



Mr. E. J. Wayland's communication on Pleistocene Pluvial Periods in Uganda, 

 referred to above, is summarised as follows : — 



The word pluviation must l)e given either absolute or relative significance, and 

 the same applies to the term pluvial period. In order usefully to limit the application 

 of the latter term, it is here given geological connotation and defined as a period of 



1930 c; C 



