I02 GLACIERS OP THE CANADIAN ROCKIES AND SELKIRKS. 



poses of measurement. When the middle stream stood at this lower level, the two 

 built a series of three or four latero-temiinal moraines which curve gently down 

 the valley from the lower ends of the laterals. The inner tei-minal of the middle 

 stream has the appearance of age, compared with the others lying just east, and 

 is being covered slowly with low shrubs and evergreens- From this difference in 

 age one would infer that the ridges of the series, lying to the east, had been built 

 by the eastern stream alone. The nose of the middle stream, especially upon its 

 eastern side, rests largely upon bedrock, more or less strewn with rock fragments. 

 The rock here, as elsewhere about the glacier, consists of quartzite and schist, 

 plucked and glaciated. Along its left side, back as far as it has become sepa- 

 rated from its neighbor, it has built a sharp-crested, lateral moraine, which 

 in the lower half is double, curving gently down the bouldery slope. The inner 

 slope is steep, the outer long and more gentle. The boulders are rounded and 

 bruised but only occasionally well glaciated. The double western nose is similar 

 to the middle, in that it is steep, perched high up on the slope, has bedrock 

 exposed upon its eastern side, while upon the left it has built a short, sharp 

 lateral extending up to the nev^. In front of the western and middle streams 

 there has been uncovered a steep slope of bouldery ground moraine so recently 

 that trees have not been able yet to get anything more than a start. 



5. Crevasses. 



Owing to the irregularities in its bed, the steep slopes, and the apparent thin- 

 ness of the ice, the Asulkan streams are badly crevassed and faulted. The ndve 

 fields of the western and middle streams cannot be traversed with any degree 

 of safety, while that of the eastern calls for the greatest skill in locating the 

 snow-covered death-traps (plate xli). The crevasses in the ndve portions are 

 mainly of the transverse type, caused by the rapid movement of the ice over 

 an in-egular, steep slope. They stand approximately at right angles to the 

 direction of motion and furnish a clue as to the general movement of various 

 portions of the nevd field. Just below the neve line the eastern stream en- 

 counters, in its central portion, an obstruction by which the ice is shattered in every 

 direction, but mainly transversely (plate xxxix, figure i). The descent is not 

 rapid enough to constitute a cascade and the blocks, at first angular, become 

 sharpened by melting into seracs but retain their vertical position until melted 

 away at the base of the slope. The development of these seracs is well shown in 

 plate XLii, figvire i. The ice exposed portion, or dissipator, of this stream shows 

 numerous marginal crevasses along either side of its course, those upon the 

 eastern side, in the lower portion, extending beyond the central axis. Those 

 upon the western side are not so strongly developed. It is upon the middle 

 stream that the dirt band crevasses occur figured in connection with the discus- 

 sion of this subject (plate xvii, figure i). The slope, however, is too steejD for 

 their formation and ^reservation. 



