370 GEOLOGICAL EXCURSION TO THE KOCKY MOUNTAINS. 



blonde, the Russell process of liariviation, a modification of 6he hypo- 

 sulphite process, h;is recently been introduced. The amalgamation 



mills, in whbh this process is curried on, are the most complicated and 

 expensive of their kind. The Quest here is that of the Bluebird mine, 

 about .'5 miles (5 kin.) west of Butte, which cost over 1300,000 and lias 

 70 stamps, two Stetefeldt shaft furnaces, each 60 feet (18 m.) high, for 



the desulphurizing and chloridi/.ing of the pulverized ore, and a lixivia- 

 tion plant. The copper ores are subjected to preliminary concentration 

 more-dressing works, roasted, and smelted to a rich matte. This matte 

 is sometimes shipped Hast, sometimes reduced to metallic copper here. 

 One Smelter, the Colorado, smelts both copper and silver ores, pro- 

 ducing a matte which has absorbed all the silver. This silver-bearing 

 matte is sent to the great smelting words at Argo near Denver, to be 

 treated by the August ine-Xiervogel process. The salt used for chlo- 

 ridizing is brought by railroad from Great Sail lake. 



From Butte the road runs westward 7 miles along the valley of Silver- 

 bow Creek, passing the Bluebird mill about midway in this distance, 

 and crossing low ridges of recent rhyolite just before reaching Silver- 

 bow station, which lies in a broad valley of Quaternary gravels. The 

 route now follows the line of the T Tab and Northern division of the 

 Union Pacific Railroad southward, traversing a series of low mountain 

 ridges mainly made up of Paleozoic rocks, which form the geological 

 connection between the north and south trending northern extension 

 of the Wasatch mountains, and the northwest trending Hitter Roof 

 mountains. These ranges not only form the continental divide between 

 east and west flowing waters, but represent in a general way the west 

 era limits of the mediterranean ocean of ftfesozoic times. No eeoloari- 

 cal examination has yet been made of the region, so that it is not pos- 

 sible to give exact indications of the age or character of all rock expo- 

 sures along the route. It may, however, be safely inferred that they 

 are mostly of Paleozoic strata and recent eruptive rocks, with a cover- 

 ing of Pleistocene gravels in the larger valleys. 



Before reaching Melrose the road crosses a divide into the valley of 

 a tributary of Jefferson river. 



From Dillon it ascends the valley of Beaver Head creek, one of the 

 main tributaries of this river, for a distance of over 50 miles; it then 

 crosses the continental divide, which is the boundary between Montana 

 and Idaho, on to the waters of the Snake river. 



Beaver canyon, which is a gorge in basaltic lavas, is the point from 

 which a stage line about 100 miles long runs to the Lower Geyser basin 

 in Yellowstone National Park. 46 The road now traverses the north- 

 eastern portion of the Snake Plains and crosses the Snake river at 

 Eagle Hock, from which it follows southward the eastern edge of the 

 Snake River desert. 



