GEOLOGICAL SUEVEY OF THE TEREITOEIES. 55 



posite side of the river, was found to be 5,925 feet. This splendid group 

 of peaks rises 5,000 feet and upward above the valley of the Yellowstone. 

 This grand range of mountains ends abruptly in the bend of the Yellow- 

 stone, near the entrance of Shield's Eiver, and the basset edges of the 

 limestone strata, high up on the end and inclining to the northwest, show 

 conclusively that, prior to their elevation, they extended uninterruptedly 

 all over this region. The greater portion of the external surface of this 

 range is compact basalt, but the cones or central portions are the gran- 

 itoid rocks, in which the gold is found. Emigrant Gulch extends up 

 into the mountains about eight miles. It is a deep, narrow gorge, with 

 . walls of a green and dark brown quartzite and true gneiss — indeed, the 

 usual variety of metamorphic rocks distinctly stratified, a portion of 

 them with so thin layers as to present a slaty appearance, and all with 

 a somber-brown hue from contact with the igneous rocks. A fine stream 

 of water flows swiftly down over its rocky bed into the Yellowstone. 

 This gulch has been quite celebrated for some years past for its placer 

 mines. It is estinjated that somewhere from 1 100,000 to $150,000 in 

 gold have been taken out since the discovery, in 1864. At one time 

 there was quite a settlement, called Yellowstone City, near the entrance 

 of the gulch, and the walls and chimneys of the houses are still standing. 

 Probably two hundred or three hundred persons were engaged in 

 washing for gold; some very fair lodes have been discovered near the 

 head of the gulch. A large amount of money was expended at one time 

 in sinking a shaft and digging a ditch for the purpose of reaching the 

 "bed-rock." There are several other gulches on either side of Emi- 

 grant Gulch, extending up fifteen or twenty miles to the second caiion, 

 and extending down to the lower or first caiion, all of which have 

 yielded some gold. All these gulches cut through the basalt, deep into 

 the granitoid nucleus, revealing the mineral character as well as the 

 liistory of this range. They are not altogether formed by erosion, but 

 were, of course, marked out during the process of upheaval: and as 

 they have been the central lines of the erosive action of water in the far 

 past, so they have been the reservoirs of the drainage from the snowy 

 summits around, up to the present time. I thus take the positiou that 

 during the upheaval of these mountain ranges, and perhaps since they 

 have reached their present elevation, the aqueous forces were vastly 

 more powerful than at present. The belt of land between the imme- 

 diate base of the mountains and the channel of the Yellowstone varies 

 from three to five miles in width, and is covered thickly with rounded 

 bowlders, varying in size from a small pebble to several &et in diameter. 

 The line of junction of the superficial deposits with the sides of the moun- 

 tain, is such that this line of erosion is not unfrequently five hundred 

 to six hundred feet above the bed of the Yellowstone, and is almost as 

 well defined as a lake terrace. The little streams that flow down from 

 the mountain sides cut sections through this deposit, so that they are 

 revealed quite clearly. The upper portion is composed in part of debris 

 from the mountains, but there is all over the valley a vast deposit of 

 what I can call by no better name than local drift or detritus. In this de- 

 tritus are quite frequently masses of rock or bowlders that have evidently 

 been transported a considerable distance by a force not now in operation 

 in the vicinity. This fact points back to a time when we may suppose 

 that there were vast accumulations of snow and ice all over the valleys, 

 but more especially on the sides and summits of the mountains; and as 

 the temperature became much warmer, this snow and ice melted, pro- 

 ducing rivers and torrents with sufficient force, aided perhaps, by. 

 the masses of ice, to move these immense bowlders from place to platie,. 



