Geology and Botany of Northern Pacific Railroad. 



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valleys on the north side of the mountains, but is quite different 

 in aspect. The sides generally are smooth and unbroken slopes. 

 1500 feet or more in height, covered with rich grass and pre- 

 senting no rock exposures. The summits of the hills are crowned 

 with evergreens which here and there creep down the ravines, 

 of which they occupy, in preference, the slopes having a north- 

 ern exposure, because here the snow lies deepest and longest, 

 supplying the greatest amount of moisture. The cause of the 

 peculiar topography of the valley of Smith's River is to be found 

 in its geological substructure, for it is cut all the way to Sulphur 

 Springs, in Cambrian rocks, which form a series several thousand 

 feet in thickness. They are mostly argillaceous shales or slates, 

 which break down together and form gentle slopes. 



Sulphur Springs is a well-built, handsome town, of several 

 thousand inhabitants, gathered around hot springs which have 

 a high reputation for their medicinal properties. From Sulphur 

 Springs we crossed the southern extension of the Great Belt 

 Mountains to the valley of the Missouri at Townsend. The 

 range is here altogether composed of the Cambrian (?) slates 

 which form the banks of Smith River, — probably the same series 

 that is cut by the somewhat famous and picturesque Prickly 

 Pear Canon on the west side of the Missouri. In some places 

 these slates are compacted by local metamorphism into masses of 

 considerable hardness, but generally they are rather soft, fine 

 grained argillo-silicious rocks, blue or gray in color, and finely 

 laminated by planes of deposition. Occasionally a harder layer, 

 an inch or two in thickness, is more silicious and rings like 

 novaculite. These rocks have suffered no change which would 

 obliterate fossils, and look as promising as any shales ; but the 

 most careful search failed to detect a single fossil in them, al- 

 though specks of carbonaceous matter were often seen, and some 

 shadowy outlines that suggest sea- weeds. There is little doubt 

 that this is the same formation with that seen beneath the Pots- 

 dam in Little Cottonwood Canon near Salt Lake City, and in 

 the Canon of the Colorado, — a formation considered Cambrian by 

 King, Powell and Walcott, and which has yielded the latter a 

 few fossils, but is universally barren and disappointing. It does 

 not occur between the Potsdam sandstone and the granite in 

 the Belt Mountains, for the same reason that the " Georgia 



