476 Proceedings. 



the Glacial Period. It is tlie fashion of the philosophy of the day to ascribe 

 much of the moulding of our hills and valleys to the denuding power of ice — 

 more in fact than one is inclined to admit. 



Professor Phillips, at a late meeting of the British Association, remarked 

 that one is almost frozen to silence in presence of the vast sheets of ice which 

 some of his friends, followers of Agassiz, believe themselves to have traced 

 over the mountains and vales of a great part of the United Kingdom. He 

 refuses to accept the proposition that these "ice-rubbers" plough out the 

 valleys and lakes, until we possess more knowledge than has yet been attained 

 regarding the resistance offered by ice to a crushing force, seeing that under 

 a column of its own substance 1000 feet high it would not retain its 

 solidity. 



I have alluded to Phillips' opinion, because I see in Geikie's late work 

 that reference is made to the fact that from the foot of glaciers in Greenland 

 streams of water issue and unite to form considerable rivers, one of which, 

 after a course of forty miles, enters the sea with a mouth nearly three-quartei's 

 of a mile in breadth — the water flowing freely at a time when the outside sea 

 was thickly covered with ice. 



This flow of water, Geikie thinks, probably circulates to some extent 



below every glacier, and he accounts for it by the liquefaction of ice from the 



warmth of the underlying soil. I am sure you Avill find a more natural 



solution of this flow of water from glaciers — estimated not less than 3000 



feet thick — in the suggestion first made by Professor James Thomson, and 



subsequently proved by his brother, Professor W. Thomson, that the freezing 



point of water is lowered by the effect of pressure 0'23° Fahr., or about 



a quarter of a degree for each additional atmosphere of pressure. Now, a 



sheet of ice 3000 feet thick is equal to a pressure of eighty-three atmospheres, 



at which pressure it would require a temperature of 19° below freezing 



point to retain the form of ice. In the state of running water below the 



glacier, it might readily, as Geikie states, absorb heat from the underlying 



soil sufficient to retain its liquid form, as the overlying weight gradually 



lessened at the edge of the glacier. In this, too, we have a safe assurance that 



these enormous thicknesses of glaciers can exist only where there is scarcely 



any or no inclination of the land to the sea board, and that no sheets of ice of 



such enormous thickness could possibly exist on the sides of mountains, as 



they would have between them and the mountain side a stratum of water ; 



and, to use a common expression, would come down "on the run." 



And this may well make us hesitate to adopt with Geikie the views of the 

 Swiss glacialists, who, I gather from Geikie's late work, speak of sheets of ice 

 having existed in the great Ice Age not less than 3000 feet thick, overtopping 

 the Jura, and stretched continuously fi-om the Rhino Valley ; and Geikie adds. 



