lxx PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. lxxvi, 



boulder-clays 1 ; and the peculiar kind of Spilsby Sandstone common 

 in the drifts of the South-Eastern Midlands. Granting that there 

 are many parts of the land-area where it is evident that the strata 

 have been torn up and mixed with the drift, particularly on the 

 higher and more irregular ground : yet I think it is clear that, on 

 the whole, the lowlands of England gained very much more than 

 they lost from the glaciation ; and that the huge mass of material 

 represented by the drift-sheets bordering the sea-basins is largely 

 an addition to our island from the sea-dredgings of the ice. The 

 surface-features of these drift-sheets reflect the conditions of their 

 accumulation, and help us to grasp the general course of events. 



An essential difference between the carriage of detritus by water 

 and by ice is that the water-borne detritus is moved persistently to 

 lower levels for a resting-place, whereas the ice-borne material (as 

 also the wind-borne) may be carried in mass to levels higher than 

 its source. Though this uplift of the detritus rarely happens in 

 the case of mountain-glaciers descending graded valleys, it. has 

 undoubtedly occurred on a large scale wherever the broad ice-sheets 

 of Pleistocene times filled up the sea-basins and sprawled forward 

 out of them to the bordering land. My long-held opinion that 

 the ice-sheets received the largest part of their accretion of snow, 

 and attained their greatest thickness, in these enclosed basins has 

 been fortified by the observations of the later explorers in the 

 Antarctic and Arctic regions. The conditions of growth of the 

 shelf -ice, of the floating glacier-tongues, and of the Ross Barrier, 

 in the Antarctic, graphically described to this Society a short time 

 ago by Sir Douglas Mawson, 2 and by Mr. Frank Debenham, 3 

 bore directly iipon this- point. So, also in the Arctic, we learn 

 from the beautifully -illustrated reports of the Danish explorers 

 in North-East Greenland, Dr. J. P. Koch & A. Wegener, 4 that, 

 besides the glaciers descending to the sea from the ice-reservoirs of 

 the interior and becoming afloat, there are in some of the fiords, 

 headless floating glaciers, specifically termed ' sikosak ' hj the 



1 See ' The Derived Cephalopoda of the Holderness Drift ' by C. Thompson, 

 Q. J. G. S. vol. Ixix (1913) pp. 169-82. 



2 See ' Discussion on the Antarctic Ice-Cap & its Borders ' Q. J. G. S. 

 vol. lxxv (1919-20) Proc. pp. i-vii. 



:i ' A New Mode of Transportation by Ice, &c.' ibid. pp. 51-76. 



' 1 ' Die Glacialogischen Beobachtung-en der .Danmark -Expedition ' and ' Fea- 

 tures of the Geography of N.E. Greenland ' Meddelelser om Gronland, vol. xlvi 

 (1912-16) Nos. 1 & 2 [chapt. vi]. 



