The Mountaineer 19 



except the snow-covered area, just mentioned, above the 

 summit of the cliffs encircling its amphitheater. The 

 gathering ground of the glacier has been decreased by 

 the extension of the amphitheater until it is but a fifth 

 or a tenth of its original extent. This glacier is still 

 enlarging its amphitheater, and if the process does 

 not check itself by decreasing the area on which snow 

 for the supply of the glacier accumulates, will cause 

 such a recession of the cliffs at its head that the central 

 dome of the mountain will become broken. 



The wall of rock rising above the head of the glacier 

 is about 4,000 feet high. On this vast precipice little 

 snow accumulates, but on its summit there is a verti- 

 cal cliff of stratified neve snow about 200 feet high. 

 [This wall of rock is called Willis Wall. See Plates 17 

 and 25.] At the outlet of the ampitheater the snow, 

 still having the characteristics of a neve, is much crev- 

 assed, especially where it passes over bosses* of rock 

 on the floor below. The glacier descends a moderately 

 steep slope on leaving the amphitheater, flows for a 

 mile and a half with a very gentle grade, and then goes 

 over the edge of a precipice and descends a steep slope 

 to its end. The alternate breaks, and level reaches re- 

 sembling a great stairway are not a novel feature, as 

 is well known, but a characteristic of many alpine gla- 

 ciers, and indicate similar features of the rock surface 

 beneath. A glacier cuts back its beds from one ice fall 

 to another, in much the same way that a cascade of 

 a stream recedes. [Plate 17 shows Carbon Glacier and 

 its much crevassed condition on leaving its cirque or 

 amphitheater.] 



Opposite Andesite Cliff, Carbon Glacier is about 

 half a mile broad, but it soon increases to nearly a mile 

 in width, and maintains this increase all the way to 

 the brink of the steep descent, a mile and a half below. 



Down-stream, the glacier is progressively more and 



• A boss is a protruding mass of harder rock In the glacier bed. 



