I. C. Russell — Mt. St. Elias and its Glaciers. 181 



Sometimes this debris is spread out on the ice, and forms 

 level terraces of sand and mud, which become prominent as 

 the glacier wastes away. 



The formation of osars seems fully explained by the subgla- 

 cial drainage of the Malaspina ice sheet. On the north side of 

 the glacier there are many streams which flow into tunnels and 

 carry with them large quantities of gravel, sand and mud; 

 while on its southern and eastern margin many streams emerge 

 from tunnels and bring out large quantities of water- worn debris. 

 The openings of the tunnels on the outer margin of the glacier, 

 are choked with debris, the coarser part of which, as already 

 stated, is deposited as soon as the streams have an opportunity 

 to expand and bifurcate. With the material swept out of the 

 tunnels there is also deposited many large bowlders as well as 

 much small angular debris, contributed by the moraines resting 

 on the margin of the ice. The deposits formed by the streams 

 below the mouth of the tunnels from which they emerge, have 

 the form of low cones, which are being built up rapidly at the 

 apex, and consequently expand at the same time in all direc- 

 tions. In expanding they frequently invade and bury large 

 areas of forested couDtry, as already noticed in the case of the. 

 Tahtse. It is evident that so long as the margin of the Malas- 

 pina glacier remains stationary or retreats, the alluvial cones 

 about its outer margin will continue to grow. This much of 

 the genesis of these accumulations is a matter of observation, 

 and afEords data for judging of the character of the deposits 

 that are being formed in the tunnels through which the glacier 

 is drained. 



The growth of the alluvial cones described above, tends to 

 obstruct the flow of water through the tunnels connecting 

 with them, and must cause the streams to deposit a portion of 

 their load on the bottoms of the channels which they occupy. 

 The water is thus brought in contact with the ice forming 

 the roofs of the tunnels, which is melted away and gives room 

 for a farther increase in the thickness of the subglacial stream- 

 deposits. In the case of a stagnant ice-sheet the accumulation 

 of gravel in the tunnels by which it is drained, would continue 

 to increase until the water finds new channels. In this way 

 deep narrow deposits of cross stratified gravel might be formed 

 within a glacier, which when the ice melted would assume an 

 anticlinal structure, owing to the displacement of the material 

 along its sides. 



In this brief digression, I have not attempted to give a com- 

 plete analysis of the subglacial drainage of the Malaspina 

 glacier ; but simply endeavored . to show that the tunnels 

 through which it is drained, must be occupied in part by 



