224 PROFESSOR JAMES GEIKIE, LL.D., D.C.L., F.R.S., ETC., ON 



prised, therefore, that for some time the evidence of climatic 

 changes during the Ice Age should have been received with 

 considerable doubt. That day of doubt, however, has now 

 well-nigh passed, and geologists generally admit that there 

 have been at least two glacial epochs, separated the one 

 from the other by one well-marked interglacial stage. 

 Indeed, as I shall presently point out, strong evidence has 

 been adduced to show that three or even more glacial epochs, 

 with intervening temperate stages, supervened during the 

 Pleistocene period. 



I have said that at least one interglacial epoch is generally 

 admitted by geologists. But I may note here that attempts 

 have often been made to explain away the evidence. It has 

 been again and again suggested, for example, that the inter- 

 glacial beds indicate no more than local retreats and re- 

 advances of ice-sheet and glacier, between the morainic 

 accumulations of which the beds in question appear. This 

 is so very obvious an explanation that it has doubtless occurred 

 to every one who has ever had occasion to give the matter 

 even the slightest consideration. I suppose no one Avho has 

 been fortunate enough to discover an interglacial deposit 

 has not tried first to account for its presence in this easy way. 

 Nor is it improbable that certain beds containing arctic forms 

 of life, and occupying an interglacial position, are to be thus 

 explained. But there remain a large number of cases which 

 refuse to be thus interpreted — interglacial deposits, which, 

 according to those who have studied them on the spot, are 

 eloquent of very considerable climatic changes. Geologists 

 sometimes forget that in every region where glacial accumu- 

 lations are well developed, good observers had recognised an 

 upper and a lower series of " drift deposits," long before the 

 idea of two separate glacial epochs had presented itself. 

 Thus, in North Germany, so clearly is the upper differentiated 

 from the lower " diluvium " that the two series had been noted 

 and mapped as separate accumulations for years before 

 geologists had formulated the theory of successive ice-epochs.* 

 The division of the German " diluvium " into an upper and a 

 lower series is as firmly established as any other well-marked 

 division in historical geology. The stratigraphical evidence 

 has been much strengthened, however, by the discovery 

 between upper and lower boulder-clays of true interglacial 



* Wahnschaffe : Forschunqen zur dentschen Landes- und Volkskunde von 

 Dr. A. Kirchhof. Bd. vi, Heft i. 



