1878.] 331 [Niles. 



Alps during the previous summer had led me to the conclusion " that 

 glaciers were not the principal agents in the excavation of valleys." 

 I have since had the opportunity of spending two summers more 

 among those glaciers, and the observations which I made have not 

 only confirmed my previous conclusion, but they have also furnished 

 me additional evidences of the excavating power of sub-glacial 

 streams. This time I was more successful in getting underneath the 

 ice than before, particularly upon the right side of the Great Aletsch 

 Glacier where it passes the cliff near the Bell Alp Hotel. The way 

 glaciers usually move over the ordinary roclies moutonne'es, bridging 

 the hollows between them without conforming to all the inequalities 

 of surface, has been made so well known that additional description 

 is unnecessary here. Under these conditions the glacier does not act 

 upon the lowest surfaces of rock beneath it, and these show by their 

 roughness and irregularity that they were not shaped by its action. 

 It, therefore, becomes evident that in such places some power must 

 have acted or is now at work lower than the surfaces upon which 

 the glacier moves. 



Under the edge of the Great Aletsch Glacier I observed in a few 

 places, that pieces were being broken from the lee edges of the roches 

 moutonnees by the pressure concentrated upon certain stones or 

 boulders which had reached these edges in their progress under the 

 ice, but I was not successful in my search for like phenomena in 

 connection with other glaciers. But this action, even if we could 

 suppose it to be sufficiently common, would serve to break away only 

 the same prominent portions of the rock which the glacier abrades. 



The ice of the glacier, however, is sufficiently plastic to conform to 

 certain kinds of irregularities of surface, and of one of these there 

 are good examples at the above-mentioned locality. There are long, 

 narrow ridges, the trends of which are the same as the strike of the 

 rock and nearly parallel with the direction of the motion of the 

 glacier. A longitudinal section of one of these ridges gave an 

 outline like that of an elongated roche moutonne, while a transverse 

 section showed quite a regularly corrugated surface. These corruga- 

 tions originated in the bedded structure of the rock, the upturned 

 edges having been rounded and smoothed by the action of the 

 glacier. The ice had time enough to conform to these longitudinal 

 furrows and ridges as it flowed over them lengthwise; and in August, 

 1876, as it passed the lee end of a ridge, it preserved the mould of 

 the profile so perfectly that for more than twenty feet the blue arch 

 presented a series of parallel furrows, like the flu tings- of a Doric 



