114 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



length of the glacier. It is a matter of much interest to try to connect the 

 crests and troughs of these ice waves with the corresponding wet and dry phases 

 of the precipitation cycles noted above. Since the crest of the wave arrived at 

 the sky-line in 1897-9, just at the close of the dry phase and the beginning of a 

 damp one, the wave must be referred back to the damp phase of the preceding 

 climatic cycle, closing in the late yo's, or early 8o's, so far as we may judge from 

 the observations of Dawson upon the level of the lakes in the western Rockies. 

 This would give the "reservoir lag" of one-quarter of the period, required by 

 Reid's calculations, and an additional 16 or 18 years for the impulse to reach the 

 crest of the rim. The trough resulting from the dry phase closing in 1897 appears 

 to have moved out from the reservoir more promptly, possibly owing to certain 

 local conditions. 



3. PIEDMONT TYPE OF GLACIERS. 



Three representatives of this unusual type of glacier were found, two of which, 

 the Wenkchemna and Asulkan, are here described; the third is the Horseshoe Glacier 

 at the head of Paradise Valley, in the Rockies. This type of glacier is always 

 compound, being made up of a series of glaciers of the common Alpine type, all 

 of coordinate importance, which coalesce laterally but retain their individuality 

 from n6v6 to nose. Since none of them are tributary to any of the others, but 

 independent in all essential respects, they are here referred to as commensal 

 streams, in order to indicate this relationship. These separate streams have 

 temporarily united forces and found strength in the union. In the case of the 

 Wenkchemna it is very probable that very few, if any, of the commensals could 

 exist separately. In its earliest stage of development the piedmont glacier begins 

 as a series of Alpine glaciers, either with or without tributaries, lying in neighbor- 

 ing valleys. With the increase in precipitation the level of the surface of the sepa- 

 rate streams rises until they cover the divides between adjacent streams, or the, at 

 first, separate Alpine glaciers reach out upon the pied-mont and there coalesce 

 laterally. In its senile condition, a stage to be reached sooner or later, the pied- 

 mont glacier returns to its condition of youth and disintegrates into its component 

 streams, as illustrated by the Asulkan of to-day. In the case of the Horseshoe 

 Glacier some sixteen different commensal streams may be recognized, the most 

 western four or five of which have almost completely separated from the 

 others. The glacier has a meager snow-field, the supply for which is ava- 

 lanched from the slopes of Mts. Ringrose (No. 10), Hungabee, Lefroy, and the 

 southern side of the Mitre. Observations upon the Wenkchemna showed that each 

 separate nose may have its own independent behavior and that the movements 

 of the glacier as a whole cannot be known unless data are collected for each 

 component stream. 



4. PARASITIC GLACIER. 



From the hanging glacier upon the eastern shoulder of Mt. Lefroy there is 

 avalanched to the back of the Mitre Glacier quantities of snow and ice, falling 



