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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



[vol. 47 



floor its motion is the resultant of its own motion and that of the 

 Mitre beneath, so that it delivers its ground morainic material, de- 

 rived from Mt. Lefroy, upon the Aberdeen side of the valley, but 

 near the junction of the Mitre and Victoria (pi. lx ; pi. lxiv, a). 

 When the map is completed it will be possible to determine the 

 relative motion of each member of this double tributary. The strati- 

 fication of the Lefroy may be clearly observed in the crevasses, dipping 

 at angles of 12° to 26 towards Mt. Lefroy. The ground morainic 



Fig. 71. — Avalanche from hanging glacier on Mt. Lefroy. 



material then in the right lateral of the Mitre and Victoria is de- 

 rived from the shoulder of Mt. Lefroy, is avalanched into the valley 

 below (fig. 71 ), incorporated into the newly formed strata, pushed 

 across the surface of the Mitre and dumped upon its eastern edge, 

 some of it arranged in ridges, parallel with the front of the Lefroy 

 as well as the side of the Mitre, where it is slowly delivered to the 

 Victoria. The feature observed from the Devil's Thumb which 

 furnished the key to this rather complicated arrangement was a 

 very sharply defined line which runs lengthwise of this double 

 tributary 1 pi. LXIIl). 



