Grade Profile in Alpine Glacial Erosion. 277 



exceptional opening gave rise. With the aid of all hands 

 from camp^ therefore, a descent and direct observation 

 was undertaken. The schrund opened to the wall, and 

 then continued, with rock on one side, for twenty or 

 thirty feet deeper. The total depth was estimated to be 

 one hundred and fifty feet. At bottom, the width between 

 walls ranged from five to ten feet. The floor, so far as 

 followed, — perhaps one hundred feet, — was approxi- 

 mately level, though made up of fallen masses of rock 

 and ice. Observation was conducted with the aid of a 

 sputtering candle, in a rain from the dripping walls. 

 This water seemed to result from local melting; there 

 was no stream entering at the surface. The rock of the 

 wall face was much riven, though undecayed. Disrupted 

 masses were in all stages of dislodgment. Some were 

 to be seen incorporated in the glacier wall at its foot. 

 Open seams in the rock-wall were partly filled with films 

 or plates of ice, thinned by melting, and removable. 

 Icicles of great size w^ere abundant, and the rock frag- 

 ments of the floor were ice-coated. To venture an infer- 

 ence from a single observation at a single point, the 

 bergschrund foot is a line of frost-weathering, relatively 

 vigorous, because freezing and thawing, there, alternate 

 at short intervals, as compared with the annual intervals 

 outside ; and of quarrying, because the glacier acts as the 

 efficient agent of removal. I have failed of opportunity 

 to repeat and extend these early observations, and the 

 hypothesis in explanation is slightly supported ; but inde- 

 pendently of explanation, the fact of sapping and reces- 

 sion in this summit region seems to be unmistakably 

 attested by the sharply delimited plateaus, their connect- 

 ing thin aretes, and the rude platform from which they 



