,..., BOZEMAH TO 15UTTE. 367 



ceous age. These ( Irei aceous beds on the right (north) are faulted down 

 a-ainst very somber-colored beds of Algonkian age. Tlie hills on the 

 | n't (south) are of Carboniferous, Jnra, Trias, and Cretaceous. At the 

 Upper end of the valley the Cretaceous is faulted down against the 

 Carboniferous, and the fault line is crossed by the road as it enters a 

 third canyon, which is mainly in Carboniferous. 



On the south side of this canyon placer-mining operations are carried 

 on- the Hume which conducts water for washing the gravels can be 

 traced on the side of the hills for many miles, cutting through the 

 rocks by tunnels in several places. A second fault line is crossed a 

 short time before the canyon is left, by which Carboniferous rocks are 

 brought down against the Algonkian. The somber greenish beds of 

 the latter are well shown on the right just before the Boulder river is 

 crossed. Beyond, the road is located on a broad island in the Jeffer- 

 son river, after leaving which tin 1 valley of Big Pipestone creek is fol- 

 lowed. I Cere Pliocene lake beds rest upon granitic and eruptive rocks. 

 As the road is followed a short distance above Pipestone springs it leaves 

 the lake beds and comes out on a body of eruptive rock (porphyrite?) in 

 which there arc several cuts. This rock is in contact with the granite 

 which occupies all the country in the vicinity of Homestake tunnel. 

 From the tunnel to Butte everything is granitic. 



[By 8. i\ Emmons.] 



'Hie granite hills form the divide or watershed between streams 

 flowing into the Atlantic Ocean on the one side and the Pacific Ocean on 

 tlic other. The age of these granites is not definitely known, but they 

 are of eruptive origin and probably pre Paleozoic. Having left behind 

 the various valleys tributary to the Missouri river, the railroad now 

 descends into the valley of Silverbow creek, which is one of the 

 southeastern sources of Clarkes Fork of the Columbia river. 



The interior portion of Montana was early discovered to contain the 

 precious metals; rich placer gravels, from which great quantities of 

 gold have been washed out, abounding in its valleys. They are still 

 worked here and there, but their greatest production was in the decade 

 L860-1870. In the last two decades deep-mining has been steadily 

 increasing, and lias developed many famous mines, such as the Granite 

 Mountain, 1 >niinluimnond, and others, which have paid millions in divi- 

 dends to their fortunate owners. 



Butte City,'"' the most important mining center of Montana, had a 

 population in L89Q of 10,723, an increase of 218 per cent over that of 

 1880. Actual mining upon the silver and copper lodes which constitute 

 its present wealth may be said to have commenced in 1875, though gold 

 had been extracted from the placer sands of the neighboring valleys 



