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Sierra Club Bulletin. 



But it is evident that here the sapping action at the 

 schrund line was more active than the glacial erosion 

 lower down on the slope, so as to create a sort of shoulder 

 or terrace near that level. Stating the interpretation in 

 another way, the excessive alimentation along the south 

 wall of the glacier was here developing a branch gl? 

 and a tributary cirque. This cirque was eating its way 

 back into the ridge bounding the glacier. On the oppo- 

 site side of the ridge, shown in the lower view, are 

 gentle slopes, largely of preglacial origin, but there are 

 also faintly developed cirques, from which small ice- 

 streams flowed toward the south. 



At still lower levels are many ridges along which 

 Pleistocene glaciers were developed on one side only — 

 the north or northeast side, so far as observed. The 

 south and southwest slopes retain the preglacial facies, 

 and retain also the actual preglacial topography, except 

 for such equable reduction of surface as may have been 

 accomplished by aqueous and atmospheric agencies. The 

 direction of ice movement in such cases was not parallel 

 to the ridge axis, but approximately normal to it. The 

 glacial excavation did not always take the character of a 

 series of cirques, but sometimes produced a continuous 

 cliff, running with moderate undulation parallel to the 

 ridge axis. 



I have no photograph representing this topographic 

 type in its purity. Figure 2 of Plate XLII, exhibiting a 

 ridge of greater altitude, serves to show a somewhat 

 similar cliff, wrought by glacial head-erosion, but imper- 

 fectly divided into cirques, and culminating in a crest 

 from which nonglacial profiles descend in the opposite 

 direction. But the example differs from the type in the 



