ESKAR EXCAVATION IN NOVA SCOTIA. PREST. 39 



others, tell us that on sunny days the surface water from the 

 melting ice disappeared in wide deep cracks in the centre of 

 vast icefields. That these crevasses never became full is 

 ample evidence that the water passed away in the depths of 

 these channels. Even the supposed subglacial streams must 

 be fed thru crevasses from the surface, else where would the 

 water come from? — and if not permanently open, where would 

 the water go? This melting of the surface ice 

 0"^y is a common summer occurrence, and can be the 

 oTwaier ^^b' possible sourc.e of water in the great ice 

 sheets of the glacial age. I doubt if any crevas- 

 ses could close permanently in a latitude where summer 

 melting was possible. This, added to the eroding power of 

 the debris incorporated in the base of the ice sheet, must in 

 ages prove ample for all the results noted. 



We know that frozen or cemented basal drift is and has 

 been ridden over by advancing ice sheets. Such instances 

 have been noted in Dawson's Acadian Geology and numerous 

 other works. We know that frozen or cemented till is often 

 loosened by the percolation of water. Also it must be acknow- 

 ledged that the impact of surface water, descend- 

 Erosionby i^g as Polar explorers saw it, for perhaps 1,000 

 falling water feet, must without doubt be a very effective 

 eroding agent. It may also be doubted whether 

 the lower ice edge in a glacial crevasse is capable of eroding the 

 underlying drift. We know that the frontal edge does so. 

 Knowing this, we cannot doubt at least the moderate erosive 

 power of an ice edge many miles to the rear, where the ice 

 sheet is probably many times thicker and the weight im- 

 mensely greater than at the front. 



Thus even before the cessation of glacial movement the 



churning effects of summer torrents from the glacial surface 



would wear and polish the debris for the grading 



Churning and stratification of a later age. It may be 



effects reasonably concluded that this torrential action 



recurred each summer for many ages before all 



forward movement of the ice sheet stopped. We are a,lso 



compelled to admit that under these known conditions the 



debris in these crevasses must be subject to much greater 



