CRYSTOSPHENES OR BURIED SHEETS OF ICE IN THE 

 TUNDRA OF NORTHERN AMERICA. 



Sheets or layers of clear ice have often been recorded as occur- 

 ring in the alluvial deposits or in the sphagnum swamps of Arctic 

 or sub-Arctic America, and most of the travelers who have made 

 even short visits to the far north have noticed the occurrence of 

 these ice- sheets in small escarpments on the edge of the tundra. I 

 myself observed them in a number of places along the southern 

 edge of the Barren Lands, in the country between the Mackenzie 

 River and Hudson Bay, and drew attention to the fact that some 

 of them, at least, were moving slowly down the gentle slopes on 

 which they were lying. Since coming to the Yukon Territory I have 

 had many opportunities of seeing and examining them in the frozen 

 bogs which cover the bottoms of most of our valleys. 



As the mode of formation and growth of these ice- sheets for a 

 long time appeared to be rather difficult to explain, the following 

 remarks with regard to them may be of interest. 



The Klondyke gold-bearing district, to which my observations 

 have lately been confined, and in which the deductions here set down 

 were drawn, is a part of a great unglaciated belt or tract of country 

 lying near the middle of the Yukon Territory in Canada, between 

 the glaciated region which extends on both sides of the "Chilcat" 

 or Coast Range of mountains to the south and southwest, and the 

 also glaciated region of the Ogilvie or Rocky Mountain range to 

 the north and northeast. It is a country of high, well-rounded hills 

 and deep, though flaring, valleys, in the bottoms of which flow streams 

 with regularly decreasing grades. On one or both sides of these 

 streams are everywhere deposits of alluvial material, varying from 

 ten to a hundred feet in depth, consisting below of coarse sand and 

 gravel, above which are fine sands with peaty and vegetable mate- 

 rial, the uppermost layer, locally known as "muck," usually con- 

 sisting almost exclusively of sphagnum swamp. The streams flow 

 on beds of the coarser alluvial gravel or sand, seldom touching the 

 underlying rocky floor, and are at present confined in relatively 



