TItAXSACTlONS OF SECTION C. 561 



times, and a like succession of life-forms followed the final disappearance of f^lacial 

 conditions. A study of the organic remains met with in any particular deposit 

 will not necessarily, therefore, enable us to assign these to their proper horizon. 

 The geographical position of the deposit, and its relation to Pleistocene accumu- 

 lations elsewhere must clearly be taken into account. Already, however, much 

 has been done in this direction, and it is probable that ere long we shall be able to 

 arrive at a fair knowledge of the various modifications which tlie Pleistocene floras 

 and faunas experienced during that protracted period of climatic changes of which 

 I have been speaking. We shall even possibly learn how often the arctic, steppe-, 

 prairie-, and forest-faunas, as they have been defined by "Wold rich, re])laced each 

 other. Even now some approximation to this better knowledge has been made. 

 Dr. Pohlig,' for example, has compared the remains of the Pleistocene faunas 

 obtained at many different places in Europe, and has presented us with a classifi- 

 cation which, although confessedly incomplete, yet serves to show tlie direction in 

 which wo must look for further advances in this department of inquiry. 



During the last twenty years the evidence of interglacial conditions both in 

 Europe and America has so increased that geologists generally no longer doubt 

 that the Pleistocene period was characterised by great changes of climate. The 

 occurrence at many different localities on the Continent of beds of lignite and 

 fresh-water alluvia, containing remains of Pleistocene mammalia, intercalated 

 between separate and distinct boulder-clays, has left us no alternative. The 

 interglacial beds of the Alpine lands of Central Europe arc paralleled by similar 

 deposits in Britain, Scandinavia, Germany, and Fiance. But opinions differ as to 

 the number of glacial aud interglacial epochs — many holding that we have evidence 

 of only two cold stages and one general interglacial stage. This, as I havesairl, is 

 the view entertained by most geologists who are at work on the glacial accumu- 

 lations of Scanfiiiiavia aud North Germany. On the other hand. Dr. Penck and 

 others, from a study of the drifts of the German Alpine lands, believe that they 

 have met with evidence of three distinct epoclis of glaciation, and two epochs of 

 interglacial conditions. In France, while some observers are of opinion that there 

 have been only two epochs of general glaciation, others, as, for example, M. Tardy, 

 find what they consider to be evidence of several such epochs. Others again, as M. 

 Falsan, do not believe iu the existence of any interglacial stages, although they 

 readily admit that there were great advances and retreats of the ice during the 

 Glacial period. M. Falsan, in short, believes in oscillations, but is of opinion that 

 these were not so extensive as others have maintained. It is therefore simply a 

 question of degree, and whether we speak of oscillations or of epochs, we must 

 needs admit the fact that throughout all the glaciated tracts of Europe, fossiliferous 

 deposits occur intercalated among glacial accumulations. The successive advance 

 aud retreat of the ice, therefore, was not a local phenomenon, but characterised all 

 the glaciated areas. And the evidence shows that the oscillations referred to were 

 on a gigantic scale. 



The relation borne to the glacial accumulations by the old river alluvia which 

 contain relics of palneolithic man early attracted attention. From the fact that 

 these alluvia in some places overlie glacial deposits, the general opinion (still held 

 by some) was that paleolithic man must needs be of postglacial age. But since 

 we have learned that all boulder-clay does not belong to one and the same geo- 

 logical horizon — that, in short, there have been at least two, and probably more, 

 epochs of glaciation — it is obvious that the mere occurrence of glacial deposits 

 underneath palaeolithic gravels does not prove these latter to be postglacial. All 

 that we are entitled in such a case to say is simply that the implement-bearing 

 beds are younger than the glacial accumulations upon which they rest. Their 

 horizon must be determined by first ascertaining the relative position in the glacial 

 series of the underlying deposits. Now, it is a remarkable fact that the boulder- 

 clays which underlie such old alluvia belong, without exception, to the earlier 



' Pohlig: Sifzunflsh. d. Nicderrlirinisclien Gesrlhchaft :u Bonn, 1884; Zeitschr. 

 d. drvtsoh. genlng. Oes., 1887, p. 798. For a very full account of the diluvial 

 European and Nortlicm Asiatic mammalian faunas by Woldfich, see Mem. de VAcad. 

 des Sciences de St. PHertbovrg, vii* S6r., t. xxxv., 1887. 



1889. 



