tNFLUENCE OF GLACIERS ON THE YUKON. 115 



rugged country, in which the mountains, composed largely of limestone, 

 trend nearly east and west, and are exceedingly sharp and rugged. The 

 river here flows with the strike of the rocks, but yet has only a very limited 

 amount of low land along its border. Near the mouth of Forty-mile creek 

 and for a long distance above, the rocks are a metamorphic schist, which 

 form bold rugged cliffs along the river, and afford some of the finest scenery 

 on the Yukon. 



At the mouth of the Lewes the country is more open ; the hills are bold, 

 with rounded summits, and the characteristics of a glaciated region replace 

 the angular mountain forms so typical of the Lower Yukon country. About 

 Lake Lebarge, especially, the rouuded, flowing outlines of the hills bear 

 unmistakable evidence of intense glaciation. In ascending the Lewes the 

 scenery increases in grandeur until the snow-covered summits of mountains 

 along the southern coast of Alaska come in view. The many lakes of this 

 region add an attractive feature to the scene and enhance the maguificence 

 of the mountains surrounding them. 



THE WATER OF THE YUKON. 



Muddy and Clear Tributaries. — The larger streams tributary to the Yukon 

 and to the Lewes from the south — viz., the Tananah, White, and Tahk-heena 

 rivers — are heavily loaded with silt and have all of the characteristics of 

 glacial streams. All of the tributaries of the Yukon from the north, and also 

 the smaller streams from the south, are clear; but some of them arc dark 

 with organic matter derived from the swamps and moss-covei'ed areas through 

 which they flow. These characteristics of its tributaries indicate at once, 

 and the conclusion is sustaiued by other evidence, that all of the glaciers 

 within the Yukon drainage system are located along its southern border. 



The Yukon below the mouth of the Tananah is intensely muddy, and de- 

 rives a very large part of its sediment from that river. Above the mouth of 

 the Tananah it is still very turbid, and holds this character to where White 

 river empties in its heavily loaded flood. Above that point it is practically 

 a clear stream, but still has a slight milky turbidity, which gives its water a 

 milky or opalescent tint. This slight discoloration is due to sediment con- 

 tributed by the Lewes. At the junction of the Yukon and the Lewes a 

 marked contrast in the color of the two streams is especially noticeable. The 

 Yukon above the junction is clear and dark, while the Lew- is decidedly 

 milky in appearance. This contrast has been noted by Dawson,- who ob- 

 serves : " The water of the Lewes has a blue, slightly opalescent color, much 

 resembling that of the Khone where it issues from the lake of < reneva, while 

 that of the Tes-lin-too [Yukon] is brownish and somewhat turbid." 



* Rep. Yukon District, loc. cit., i>. i 53b. 

 XVI— Bull. Gbol. Soc. Am., Vol. 1, 1889. 



