GLACIAL EEOSION. 97 



glacier movements of from forty to seventy feet a day. In these cases the glaciers are 

 moving into the sea, and the new clement of partial flotation or sliding, vrhich does not 

 belong to land glaciers is here introduced. The great velocity of these glaciers is far 

 beyond any observed ability of ice to flow as plastic bodies ; consequently, one is led to 

 conclude that, under partial flotation, stones may be held firmly as graving tools by glaciers. 



Hereby we are able to explain the occurrence, in many Alpine valleys, of a greater 

 glaciation than we see in progress to-day, as being due to glaciers rapidly advancing into 

 fjords, during a period of partial submergence. 



The appeal to the greater magnitude of the glaciers, as producing effects not now 

 seen as the result of those of the present day, seems to be begging the question, for the 

 action of thicker glaciers differs from that of thinner in amount rather than in kind ; for 

 increased pressure, raising the temperature, increases the plasticity of the ice, as it is 

 seldom if ever lower than freezing point. Consequently it seems improbable that stones 

 should be held more firmly in glaciers of thousands of feet in thickness than in those of 

 hundreds of feet. In addition, the friction between the stones held in the ice, and the 

 surface of the subjacent rock, is proportionally increased by the greater weight of the 

 glacier. 



Over the vast area of action, the work of floating or sea-ice, in some forms, is enormous. 

 On the northern side of Hudson Strait, Dr. John Rae,' who had very extensive arctic 

 experiences, found that snow drifting over precipices into the sea resulted in the forma- 

 tion of bergs, sometimes a hundred feet thick, filled with the loose rock debris of the 

 coast, and having the form of the shore where formed. Most of them break loose and 

 drift away to melt or become stranded elsewhere. 



Greely describes the great momentum with which the floe-bergs come together. By 

 their meeting, the ice is crushed and raised up into ridges fifty or sixty feet high. 



One cannot read carefully the results of the British Arctic Expedition of 1875-6, without 

 being impressed with the erosive power of drifting ice, moving with a velocity never 

 acquired by glaciers. Floe-bergs are pushed upon a shelving sea-bottom, until the ice has 

 risen from twenty to sixty feet, after their first stranding in perhaps only from eight to 

 twelve fathoms of water, although weighing tens of thousands of tons. ^ 



As the grounded floe-bergs are forced up the shelving sea-bottoms, ridges of earth 

 and stones are pushed up in front of them. Floe-bergs which have been toppled over, 

 thus showing their original bottoms, and also names of pushed-up coast ice are found to be 

 grooved and to contain angular stones with their exposed surfaces scratched and polished. 

 As the movement is greater than the velocity of glaciers flowing about obstacles, it is 

 only natural to expect that the enclosed stones should be held firmly as graving tools, or 

 be wrenched out owing to the brittleness of the ice under such great stress. 



In describing the ice action on the coast of Labrador, Prof H. Y. Hind, says, that the 

 " pan-ice " (from five to twelve feet thick) is polishing the surfaces and sides of the rocky 

 coast, and producing boulder clay. He says : " When the pans are pressed on the coast 

 by winds, they accommodate themselves to all the sinuosities of the shore line, and being 

 pushed by the unfailing arctic current, which brings down a constant supply of floe ice, 



' In Canadian Journal, Toronto, 1S59. 



^ British Arctic Expedition of 1875-76, Sir Georges Nares. 



Sec. iv, 1887. 13. 



