


"R Proceedings of Scientific Societies. 945 
above the ice) ceases at any point, then all the boulders will gradually 
sink through the ice and become glaciated at the bottom. Prof. 
Hughes also thought that two distinct types of ridges formed of glacial 
material were confused under the names kames, osars, and eskar. He 
also explained that ‘‘ pitted plains °’ as due to an unusual iecrapition 
between the hills or ridges of eskar character. He expressed his opin- 
ion that the Glacial period was a continuous one, in England at least, 
except for slight changes due to unimportant oscillations. 
r. Wahnschaffe advocated the chronological classification, and con- 
sidered such a one possible for the Quaternary deposits of North 
Germany. ‘These deposits begin with pre-Glacial sands and gravels 
containing Paludina diluviana, which is still a living form, and Lztho- 
glyphus naticoides. Above these follows a typical ground moraine, 
which is overlaid by stratified sand and gravel, containing the well- 
known diluvial fauna; and to these again succeeds the upper till, 
considered now as the ground moraine of the second glacial epoch. 
Prof. H. Credner: The occurrence of the sand between two ground 
moraines indicates a retreat. and second advance of the ice sheet. 
Such interpolated sands are in Germany always local, and no proof 
of a real interglacial epoch. The sand layers between the moraines 
are not continuous, but local, and cannot be given the significance 
attributed to them by Wahnschaffe. 
- Prof. Pavlow: In order to secure a satisfactory classification of 
Quaternary deposits, we must.secure a satisfactory definition of Pleis- 
tocene. Prof. Pavlow said he would like to give his own views, but 
would postpone them until such accepted definition had been arrived at. 
Baron de Geer agreed with Wahnschaffe that the chronological 
classification is at least locally possible. He also recognized two glacial 
epochs, due to two great oscillations. These cannot always be 
separated, as, for instance, in Russia. For this reason it is best to 
commence with a genetic classification, since this causes less confusion 
to the field geologist. 
Dr. Wahnschaffe replied to Prof. Credner’s assertion that there is no 
proof of an interglacial period in Northern Germany. He that that , 
the existence of a diluvial fauna between the two tills is sufficient 
roof. 
Prof. Credner replied that no complete skeleton had been found, 
but only single bones which might have been transported and ae 
with the gravel. 
Dr. Wahnschaffe again replied that the bones occurring in these 
_ gravels are proportionately large, when compared with the oes 
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