Ice-Cliffs on the Kobuk River 115 



a short time on her way north, several tusks and large bones of the 

 mammoth were brought aboard for barter. * * * On August 28. 

 1885, at Schismarefif Inlet, I found the front half of the skull of a 

 mammoth lying on the open tundra, which was not fossilized in the 

 least, being simply a mass of dry bone, firm and light. This is rather 

 remarkable, considering the long extinction of the mammoth and 

 the geologic and climatic changes which have since taken place in 

 North America." 



In the Amer. Geologist, Vol. VI, page 49, I. C. Russell publishes a 

 letter from Lieut. J. C. Cantwell in answer to a request for further 

 information regarding the ice-clififs on Kowak River, Alaska. 



" The river is navigable for a distance of 375 miles. At two 

 points before reaching the headwaters, we encountered gorges where 

 the width of the stream scarcely exceeds twenty yards and where 

 the channel was filled with rough bowlders. 



" Some seventy or eighty miles from the mouth is where we first 

 observed the ice-clifTs mentioned in my official report. At this point 

 the cliffs were from 125-150 feet high, gradually decreasing in 

 height as we noted their recurrence on our way up stream, until 

 they had entirely disappeared when we had reached the foot-hills of 

 the first chain of mountains through which the river flows. The 

 topography of the Kowak Valley in the vicinity of the ice-cliffs is 

 characterized by undulating tundra plains, varied by patches of 

 small spruce timber which, as a general rule, was most abundant 

 along the banks of the stream. For about a mile there is exposed 

 to view a solid mass of ice superposed by a layer of soft earth form- 

 ing a uniform thickness of about six feet. In color the cliffs are 

 dark brown. The ice is not clear and must have been formed from 

 water holding in solution a large quantity of earthy matter. There 

 is no apparent stratification. No gravel was seen. The shore line 

 in front of the cliffs was marked by an accumulation of soft almost 

 impalpable dust piled in heaps to a height of 15 or 20 feet. The 

 dust piles were evidently the result of the melting of the ice during 

 the summer, as the annual spring freshets sweeps everything before 

 them. 



" In the first place the ice is solid without fracture from top to 

 bottom " and again there are numerous high sand and clay cliffs abut- 

 ting on the river in situations exactly similar to those occupied by 



'" The writer dees not believe Mr. Cantwell means to be understood that the 

 cliffs are solid ice from the river level to a height of 150 feet, but that simply 

 the ice deposit itself on top of the clays is solid, i. e., not stratified. His 



photographs support this interpretation. 



