L16 I. C. RUSSELL URFACE GEOLOGY OF ALASKA. 



The principal Bource of the fine sediment that discolors the Lewes below 

 Lake Lebarge is derived from the Tahk-heena river, which has its source 

 among the glaciers near the Ghilkat pass and joins tin- Lewes just above 

 Lake Lebarge. The extreme fineness of the sedimenl which discolors the 

 waters of Lake L barge and of the streams flowing from it will be appreciated 

 when it is remembered thai although the lake is nearly thirty miles long the 

 water- passing through it are m>t completely cleared by sedimentation. 



The waters of the numerous lakes along the course of the Lewes above 



Lake Lebarge are also i e or Less turbid with silt. Their turbidity 



increas ae approaches the Coast Range, on which are many glaciers, 



and it is evident that the sediment in the lakes and streams is due directly 

 to the abrasion of the rocks by glacial ice. The water- of Lake Lindeman, 

 especially, are densely turbid and have a greenish-white color. The upper 

 portion of Lake Bennett is similarly discolored. As these water.- passdown 

 through lake- Tagish and Marsh they become greatly clarified, but still 

 retain suffici< nl line silt to reveal their glacial origin. 



v ■mi' at in Suspension. — While ascending the lower Yukon five samples 

 of the water of the river, of a liter each, were collected at the localities given 

 below, and the weight of sediment they contained determined. The results 

 of this investigation are as follows : 



Sediment in the Water of the Yukon. 



Locality. Date. < ■ n a liter. 

 Below mouth of j^°\ k f - ™ y S' l889 &«f» 



I Nowikakat.. .__. " Jo, " o. , 83 



ive mouth of f Entrance of Lower Ramparts. " 27, " 0.2754 



theTananah. \ Five miles above Lower fiamparts " 28, " 0.2078 



No determination of the volume of the Yukon was practicable during my 

 journey, but it is expected that Messrs. McGrathand Turner will make such 

 measurements during their descenl of the river in 1890. When the results 

 of their observations are known, the data given above will enable one to form 

 a rough estimate of the amount of material that is being carried in suspension 

 from the land to the sea by Alaska's greal river. 



•LOGICAL Rl NOW BEING MADE Bl THE iTJKON. 



Thi I: in Winter. My experience on the Yukon is limited to a brief 

 summer trip. For information concerning it- behavior in winter I am 

 indebted to many miners and trader-, mid especially to Arthur Harper* 

 who has passed many winter- in central Alaska and the adjacent portion of 

 the North \\> -i Territory. 



Like many norl h\\ ard-llowing river-, the ^ ukon i- closed by ICC firsl at 



