202 THOMAS C. CHAMBERLIN AND ROLLIN T. CHAMBERLIN 



more advance movement of the ice here. The basin on the right 

 has become a glacial valley in an embryonic stage and the work 

 of water erosion seems to form a larger factor. 



Sculpturing of similar sort is illustrated by Fig. 5, from the 

 Swiss Alps. The brow of a long spur descending from the Zwil- 

 linge has been scooped and hollowed in concave fashion by the 

 sapping action of glacier ice. Occurring in the midst of a still 



Fig. 6. — The Glacier des Grandes Jorasses on the Italian side of the chain of 

 Mont Blanc. The ice has sunk its bed into the rocky mountain wall and worked 

 backward as implied by the distinct bench upon which it rests. Photo, by R. T. C. 



strongly glaciated area, this case is interesting for the reason 

 that such sculpturing has been at work here for a comparatively 

 short time only. The rounded rock contours below and to the right 

 of the hollow excavation have at no distant date been scraped and 

 polished by the larger glaciers descending from the peaks above. 

 The ordinary abrasive action of a moving body of ice is here 

 illustrated. But the much smaller mass of snow and ice at the 

 base of the cliff in the hollow appears to have operated in the very 

 different and more potent manner of basal sapping at the schrund 

 line. 



