The Mountaineer 17 



on the western and southern sides, would lead to the 

 gathering of the ice into more or less definite streams. 

 Individualized ice streams once established would hold 

 their positions, and by their erosion would sink deeper 

 and deeper into the rocks. From the extremity of each 

 glacier a stream fed by the melting ice would carve 

 a gorge or canyon, leading to rivers on the plain below. 

 As the ice gathered in well-defined streams, melting 

 would be retarded and the glaciers constantly extended 

 farther and farther down the water-cut gorges. In this 

 manner what may be termed primary glaciers would 

 originate from the dividing of the descending neve. As 

 the glaciers deepen their beds they sink into the moun- 

 tain and are more completely sheltered from the sun, 

 thus tending to perpetuate their own existence. Be- 

 tween the primary glaciers there would be portions of 

 the lower slopes of the mountain left in relief by the 

 excavation of the valleys between them. These V- 

 shaped masses pointing up the mountain would form 

 wedges, against which the descending neve would di- 

 vide to form primary glaciers. The Wedge and Little 

 Tahoma are typical examples of such wedges. 



As is well known, the erosive action of a glacier, 

 other conditions being the same, depends on the gradi- 

 ent of its bottom. Judging from the present condition 

 of Mount Rainier and other similar isolated peaks on 

 the Pacific Coast, it appears that the most intense ero- 

 sion occurs in a zone about half a mile broad where 

 the primary glaciers become distinct ice streams. In 

 this zone the glaciers excavate canyons, and thus in- 

 crease the slope of the central mass of the mountain 

 above the extremities of the V-shaped residual masses, 

 on its lower slopes. The heads of these valleys tend 

 to become amphitheaters. The clififs encircling an am- 

 phitheater in which a glacier has its source, gradually 

 recede, owing to the disintegration of the rocks in the 

 great crevasse, termed a bergschrund, which is formed 



