12 SMITHSONIAN MISCELLANEOUS COLLECTIONS \'0L. 76 



been sketched in from photographs, giving a graphic picture of the 

 relative importance of the tributaries as sources of ice supply. Com- 

 pared to the size of the ice system, they are small and scanty (pi. 6, 

 figs. I and 2). They do not anywhere pile themselves up into lofty 

 continuous ridges. Their prominence is due chiefly to their lineal 

 distinctness and lack of wide dispersion over the surface of the ice. 



The northerly segment of the basin, beyond the discharge tongue, 

 contributes scantily to it (pi. 7, fig. i). Owing to various causes, but 

 chiefly to a more direct exposure to the sun, melting has exceeded the 

 snow supply and the ice is in an essentially stagnant condition. Three 

 commensal streams occur here : the Niverville and Pangman glaciers, 

 and another without a name which issues from a deep precipitously 

 walled cirque on the north side of Alt. Freshfield. Judging from its 

 position and length, this is the most vigorous of the trio. At the 

 corner where the main tongue issues from the basin, the Niverville 

 and Pangman glaciers, in receding to the higher slopes, have un- 

 covered a portion of the trough floor and a little upland valley filled 

 with rushing streams and bordered with ice tongues. (See pi. 7, 

 fig. 2 and pi. 4, fig. 2.) Thus there has been produced a lateral 

 U-shaped alcove, across the open end of which the main body of ice 

 flows, exposing a section about 75 feet thick and 500 yards wide. Its 

 position has been indicated on the map (fig. 2). 



Such depressions are not uncommon features of valley glaciers. 

 They often give rise to marginal lakelets, as the Marjelen See on the 

 Aletsch Glacier. But this particular one possesses the peculiarity of 

 occasionally being filled by an offshoot from the main ice field in the 

 shape of a secondary tongue. Although at the time of our visit in 

 1922, it was entirely bare of ice, in July, 1918, the Boundary Survey 

 photographs show that it was filled to the brim with shattered ice 

 fragments in the nature of icebergs or seracs. (Note even line of vege- 

 tation at level of main glacier in pi. 7, fig. i. This would seem to be 

 an " ice-line " corresponding to the waterline in the case of a lake.) 

 The accompanying photograph, taken in August, 1913 (pi. 8, fig. i), 

 indicates that not long before an ice invasion had also occurred here, 

 as many wasting pillars of glacier ice were scattered about on the 

 floor of the alcove. Thus, the place appears to serve as a kind of 

 safety valve, which relieves pressure on the constricted dissipator 

 whenever the snow-fall on the mountains to the south and west has 

 accumulated beyond the dissipator's capacity for prompt discharge. 



The writer spent an afternoon visiting the locality and in photo- 

 graphing the ice wall at close quarters. Another secondary tongue 

 seemed to be forming, for the wall had thrown forward several 



