420 Dr. Nils Olof Hoist — The Ice Age in England. 



mixture of salt- and fresh-water deposits, peat and beds of multifarious 

 composition, deposits more or less covered by moraine or frequently 

 covered only by sand, and so forth. And "Wolff migbt have added 

 that from time to time the various deposits now known to be either 

 pre-glacial or locally post-glacial have been made to serve as good 

 proofs of an interglacial epoch. This production of proof has under- 

 gone a continuous and regular development : year after year the old 

 proofs once thought so satisfactory have been found wanting and cast 

 aside to make room for newer and better ones. 



As " the most certain of all the North German interglacial deposits " 

 is at present regarded the Paludina bed, which in Berlin and its 

 environs has been shown to lie between two moraines interpreted as 

 having been deposited during the first and the second glaciations. 

 But this has not always been the case. F. Wahnschaffe, for many 

 years the leading interglacialist of North Germany, expressed himself 

 as follows about the Paludina beds in 1893 ' : '■'■Paludina diluviana 

 had its home in the North German lowlands, before the lower 

 moraine was deposited there, since the large accumulations of shells 

 of both adult and young individuals as well as the condition in which 

 the shells were preserved left no doubt but that the molluscs 

 in the Paludina beds of Berlin occurred in situ ('auf primarer 

 Lagerstatte '). On the other hand, in the moraine it is a derived 

 fossil, and then it was driven for ever (' dauernd ') from its old home." 

 Subsequently, in 1901, the same geologist transferred the Paludina 

 bed from pre-glacial to interglacial deposits, with the absurd 

 consequence that there were no longer any pre-glacial deposits 

 in the whole of the North German lowlands. " The existence of 

 pre-glacial formations," says Wahnschaffe, "is not yet proved, 

 inasmuch as the fossiliferous deposits formerly regarded as pre-glacial 

 are now referred to Interglacial I." 2 But, as is well known, 

 this warmth-loving snail has now withdrawn itself to the lower 

 Danube, to the neighbourhood of the Black Sea. Moreover, it occurs 

 fossil in North Germany together with admittedly pre-glacial 

 Mollusca, and in England it is admittedly pre-glacial, since it there 

 occurs only in the older pre-glacial deposits : in the Neritina locality 

 at Swanscombe as well as that at Clacton-on-Sea. Thus the appearance 

 of the mollusc in England is quite clearly decisive for Wahnschaffe's 

 earlier view, and the first two North German glaciations are changed to 

 a single one. Moreover, Wolff himself in another connexion explains 

 that the oldest glaciation is very problematic (" dem altesten Glazial 

 haftet viel Problematisches zu "). 



Finally, as regards the "younger interglacial formations", which 

 should distinguish the second and third glaciations, Wolff points out 

 as an indisputable fact that, in consequence of their manifold forms 

 and their position on so many different horizons, they cannot be 

 regarded as contemporaneous. They are usually covered only by 

 sand and gravel, no bottom moraine has gone over them, etc. He 



1 F. Wahnschaffe, 1893. " Ergebnisse einer Tiefbohrung in Niederschon- 

 weide bei Berlin " : Zeitsehr. Deutsch. Geol. Ges., Bd. 45, pp. 292-3. 



2 P. Wahnschaffe, 1901. Die Ursachen der Oberflachengestaltung des 

 norddeutschen Flachlandes, 2 Aufl., p. 239, Stuttgart. 



