GLACIAL EROSION AND TRANSPORTATION. 233 



from the roof and pressing against the stone. In place of push- 

 ing the stone along or flowing around it, the lower layer of ice 

 above the tongue had yielded, and was bent backward as easily 

 and gracefully as if it had been a thin sheet of lead, instead of 

 one of ice a foot thick. 



The insufficiency of glaciers to act as great erosive agents 

 is further shown at Fondalen, where a mass of ice thirty or 

 forty feet thick abuts against a somewhat steep ridge of a rock 

 ten feet or less in height. In place of a stone-shod glacier 

 sliding up and over the barrier, the lower part of the ice 

 appears stationary, or else is moving around the barrier, while 

 the upper strata bend and flow over the lower layers of ice.* 



The whole body of facts concerning a ground moraine 

 speaks in like manner of the limited amount of disturbance, 

 in certain conditions, which is produced by the ice as it 

 moves over loose material. There can be little doubt that, 

 for a breadth of a hundred miles or more on the border of 

 the glacial limit in [North America, the ice advanced over 

 the loose material (which is variously called " bowlder-clay," 

 11 till," and " ground moraine ") without greatly disturbing it 

 as a body. Indeed, this great mass of firmly compacted, 

 unassorted, and glaciated material would seem to have ac- 

 cumulated by degrees — the moving ice, dragging along under 

 it successive strata of the grist which it had ground from the 

 surface of the rocks far to the north, where its action had 

 been more vigorous and long continued. For another strik- 

 ing illustration of the power of ice thus to move for a limited 

 distance over loose material without disturbing it, one has 

 but to refer to the description already given of the buried 

 forest near the southwestern corner of the Muir Glacier, 

 Alaska.f Here large trees in great numbers, which have 

 been preserved for an indefinite period underneath the gla- 

 cier, are now being uncovered, and appear standing upright 



* See " Glacial Erosion in Norway and in High Latitudes," reprinted from 

 "Proceedings of the Royal Society of Canada," 1887; extracted from "Ameri- 

 can Naturalist," vol. xxii, 1888, pp. 218, 221, 223. 



f See p. 65. 



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