1XXX PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. Ixxvi, 



that this state would be brought about by the outrush of cold air 

 resulting from the proximity and gradual approach of the Scandi- 

 navian ice-sheet, since we know that this is the effect of existing 

 ice-sheets in Greenland and the Antarctic. Yet, on the other hand, 

 the remains of huge herbivorous mammals, such as the elephant, 

 hippopotamus, and rhinoceros, are found plentifully in many places 

 in old beaches, cave-deposits, etc., immediately beneath boulder- 

 clay, as well as in ancient river-gravels and other terrestrial deposits 

 apparently dating at different times between the beginning and the 

 end of the glaciation ; which seems to afford proof that there must 

 have been abundant vegetation of some kind in the country during 

 the period. It may be that the valleys and lowlands, where ice-free, 

 carried a seasonal cover of perishable grass and small shrubs, like 

 the tundra and prairies of the present day, though without the 

 massed growth and continuous moisture required to produce peat. 

 But now, I must be content with having stated the problem as 

 it presents itself to me, leaving it to you for consideration. 



To return to my main subject ; we can recognize that the principal 

 effects of the glaciation upon the uplands has been to increase the 

 area of bare rock ; to subdue some of the sharper features ; and to 

 accentuate some of the minor escarpments by removing the products 

 of weathering with which they were encumbered. The general 

 lowering of the surface has probably been less on the ice-covered 

 hills than it would have been if they had been continuously exposed 

 to the direct attack of subaerial weathering ; for it must be re- 

 membered that a thin capping of ice or neve not in active motion 

 will serve as a protection to the platform beneath it. 



In the final shaping of the hills the selective course and localized 

 incidence of the glaciation, particularly in the waning stages, must 

 have been a pronounced factor. The more we learn about the 

 regional ice-sheets of the present clay, the more evident does it 

 become that the old idea of smooth ice-caps of regular gradient, 

 flowing evenly over the land and filling up all the hollows to a 

 general level, is inaccurate in many respects. The striking fact has 

 emerged, that ice-free valleys and lowlands may occur in unexpected 

 places, sometimes insulated, but more often deeply indenting the 

 borders of the land-ice. Such tracts may be dominated by great 

 stretches of moving ice, which carry the discharge of the main ice- 

 cap along definite paths ; and, if a valley or lowland lie aside from 

 the path, and cannot nourish a glacier of its own, it may remain as 



