l*letKtoecnr Pujxrs at fli'^WaxJuiK/toii ^Icfi mj^. 241 
classification; l)ut the latter would distinguish the marine de- 
posits as a separate class. 
Prof. T. McKexny Hughes explained the al)undance of 
striated boulders in one part of the glacial deposits and their 
absence in another. If the suppl}' of material ( that is, of rock 
masses projecting above the ice ) ceases at any point, then all the 
boulders will gradually sink through the ice and become glaciated 
at the bottom. He thought it advantageous to distinguish long 
gravel ridges b}' the name osars, and short ridges and knolls as 
kames. He expressed his opinion that the Ice age was a single 
continuous cold period, in England at least, except for slight 
and unimportant oscillations in the extent of the ice-sheet. It 
was probaldy introduced liy a stage of very high land eleva- 
tion. 
Dr. F. Waiinschaffe preferred a chronological classification. 
In northern Germany the ground-moraines of two distinct glacial 
epochs are separated I)}- fossiliferous sand and gravel of inter- ' 
glacial age. 
Prof. H. Credner thought these stratified beds between de- 
posits of till to be merel}- local, indicating some retreat and read- 
vance of the ice-sheet but no interglacial epoch. 
Prof. A. Pavlow urged the need of a more satisfactory defini- 
tion of the Pleistocene period. 
Baron de <tEER recognized two glacial epochs in Sweden, due 
to two great oscillations. These cannot alwaj's 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. Waiinschaffe replied to Prof. Credners assertion that 
there is no proof of an interglacial epoch in northern Grcrmany. 
He thought that the existence of a diluvial fauna between the two 
tills is sufficient proof. 
Prof. Credner replied that no complete skeleton has been 
found, but only single bones which may have been transported 
and deposited with the gravel. 
, Dr. Waiinschaffe again replied that the bones occurring in 
these gravels are proportionately large, when compared with the 
gravels, and therefore cannot well have been transportt'<l from a 
distance. 
Prof. N. S. Shai.kk slated lliat organic (h'pcjsits may occur 
