BELT ON PRODUCTION OF LAKES BY ICE ACTION. 73 



in British North America, great holes are gradually worn during 

 winter in the sleigh tracks, commencing at first with slight depres- 

 sions in the hardened snow, and increased by the passage of every 

 sleigh, until the holes become so deep as greatly to inconvenience 

 travellers ; but here again the action is very different from the 

 -jSteady continuous flow of glacier ice, the scooping out power de- 

 pending on the sudden descent of the sleighs into the hollows, 

 which, in the case of glaciers would be filled with ice. 



Sir Charles Lyell considers that the great lake basins of Swit- 

 zerland have not been scooped out, but that they are all due to 

 unequal movements of upheaval and subsidence during the great 

 oscillations of level since the commencement of the glacial period.* 

 But whether or not this theory is sufficient to explain the formation 

 of the great lakes of Switzerland and Italy, it does not apply to 

 those of British North America, nor of northern Europe, where we 

 have lakes of all sizes, increasing in number as we proceed north- 

 ward, and found everywhere along with and evidently part of the 

 glaciation of the land. It does not explain this palpable connection 

 of rock basins with glacial action, and in seeking for another solu- 

 tion we naturally turn our attention, first of all, to that agent whose 

 power has been so conspicuously displayed in the erosion of the 

 deep valleys and fiords of glaciated countries. 



These considerations have lead me to endeavour to solve the 

 main difficulty in accepting Professor Ramsay's theory, viz. : the 

 immense depths of some of the basins ; and I think it may be 

 shown that even if the ice were dammed up at moderate depths, it 

 would still possess great grinding powers, which would be augmented 

 instead of being diminished by increased depth. In the first place 

 I must draw attention to a feature of all glaciers, the streams that 

 issue from beneath them. In Switzerland, from the bottom of 

 every glacier, rushes a torrent densely charged with mud. It is 

 the same with the great glaciers of the Himalayas — the Ganges, the 

 Pindur, the Kuphinee and the Thlonok, rise from beneath glaciers. 

 The flow of water diminishes in winter, but never entirely ceases in 

 glaciers of the first class. In Greenland, Dr. Rink says, that "in 

 some places mighty springs are seen to come forth from under the 

 outer edge of the ice, pouring out clayey water in continued quan- 



* Antiquity of Man, p. 316. 



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