Ice-Cliffs on the Kobuk River 117 



masses of detached ice stranded on the adjacent beaches or bars, 

 piles of soft dust ahiiost entirely free from any gritty substance 

 would be left as a monument to mark the spot where the ice had 

 been melted by the summer sun. These small dust heaps are a 

 characteristic feature of the region where the ice-clififs are found 

 and are entirely different in appearance from the gravel and sand 

 heaps deposited in the same way by ice floated down from the upper 

 river. 



" An examination of the tops of the ice-cliffs was very difficult on 

 account of the dense undergrowth and the thick carpet of moss, but 

 on one we discovered a lake about a mile in diameter and situated 

 some 500 yards from the face of the cliff. The water in this lake 

 was fresh and clear, but upon being disturbed became exceedingly 

 turbid, owing to the presence of a large quantity of fine, decayed 

 vegetable matter on the bottom. A piece of the ice melted showed 

 a residuum of fine, impalpable dust, which under a lens proved to 

 be composed mainly of vegetable matter and, while fresh, emitted a 

 very pungent, disagreeable odor. 



" The country in this region is mostly rolling tundra plains, with 

 innumerable small lakes, and streams, all of which are tributary to 

 the larger river. There is no evidence of glacial action whatever, 

 and it is not until the first mountain range is reached, a hundred 

 miles further up-stream, that any rocks in situ are seen. Here and 

 further inland more plainly are to be found beds of trap, which on 

 examination shows to be a pronounced olivine diabase, with such 

 minerals as hornblende, mica, feldspar, augite, etc., present. Other 

 rock forms show unmistakable evidence of the eruptive agencies 

 that have been at work in the formation of the upper river region. 

 The formation of the remarkable ice-cliffs in the lower country is, 

 however, a geological nut which the writer admits his inability to 

 crack." 



