GLACIER CORNICES. 



In recording observations concerning the glaciers of Green- 

 land, Professor T. C. Chamberlin'' describes a jutting of certain 

 layers of clear ice over dirt-stained layers in the vertical escarp- 

 ment at the lower end of Tuktoo glacier. The projections or 

 cornices referred to overhang from a few inches to ten or even 

 fifteen feet. As to their origin, two hypotheses are discussed; 

 one, to the effect that they are due to a greater rate of motion in 

 the projecting layer of ice than in the layer immediately beneath ; 

 and the other, that the exposed edge of a dirt-stained layer melts 

 back more rapidly than the similarly exposed edge of a stratum 

 of clear ice. Either of these two explanations is considered as 

 being applicable to the observed examples, and a choice between 

 them does not appear to have been practicable. 



While examining the glaciers on the Three Sisters, Oregon, 

 on August i6, 1903, I found jutting layers of neve ice, on the 

 vertical wall of a crevasse which seem to be a counterpart of those 

 described by Chamberlin, a photograph of which is here repro- 

 duced. 



The wall of ice, or rather granular neve, referred to, occurs 

 near the head of a small glacier at the east base of West Sister, 

 and occupies an amphitheater-like depression between West and 

 North Sister. It is the upper or hanging wall of the highest 

 crevasse which intersects the glacier or a BergscJirund, the lower 

 wall of which had in part fallen previous to my visit, so as to 

 leave its companion fully exposed. The wall faces east and is in 

 shadow after midday, when melting ceases on its face. In ref- 

 erence to the stratification of the snow, presence of dirt bands, 

 exposure to the sun, etc., the conditions present are similar to 

 those pertaining to the glaciers of Greenland on the vertical 

 walls of which cornices have been observed. 



The escarpment shown on the accompanying photograph is 



^Bulletin of the Geological Society of America, Vol. VI (1895), PP- 206, 207; Journal 

 OF Geology, Vol. IV (1896), pp. 589-91. 



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