482 REPORT UNITED STATES GEOLOGICAL SURVEY. 



In 1871 and 1872, Dr. Hayden's survey mapped, also in a rougli way, 

 it must be confessed, the whole western slope of the rang^e, from the 

 south line of the Park to the north end of the range, ascending no less 

 than six of the dominant peaks, and crossing the range in two places, 

 at the heads of Soda Butte and Slough Creeks. Again, I have been 

 unable to find a reference to this range wherein Dr. Hayden speaks of 

 it as anything else than the "Yellowstone Range," and this name recurs 

 in his reports repeatedly. In one place he speaks of it as being repre- 

 sented on old maps as the Snowy or Heart Mountains. The fact that on 

 a map of Yellowstone Lake the name Yellowstone is applied to a range 

 south of the lake is due to an error of the draughtsman solely. And, 

 in passing, I may remark that the range in question has an existence, 

 Captain Jones to the contrary notwithstanding, if a mass of country 

 2,300 feet above the lake and 10,000 feet above the sea has any claims 

 to the name of mountains. 



Throughout its whole extent this range is extremely rugged. That 

 portion of it lying within the Park is almost entirely volcanic, only a 

 small portion of it near the north line being of granite. It occupies a 

 great breadth, and its peaks range nearly up to 12,000 feet in height. 

 The highest peak yet measured is Index Peak, which stands 4 or 5 

 miles east of the Park, and has an elevation of 11,702 feet. There are 

 probably many higher peaks, as the great bulk of the range has not yet 

 been explored. 



The first large stream entering the Park from these mountains is Hell- 

 Eoaring Eiver, which flows into the Yellowstone in the third canon. It 

 comes from the granite portion of the range north of the Park, cutting 

 a tremendous gorge through it. Reaching a low plateau at the base 

 of the mountains, it changes its course from south to nearly northwest, 

 flowing nearly parallel to the Yellowstone for several miles before fall- 

 ing into it. In the bend of the stream stands a high, sharp, conical 

 peak of granite, a well-known landmark in this region, known as Hell- 

 Roaring Mountain. 



The next stream draining Yellowstonewards is Slough Creek, a large 

 branch of the East Fork. At its head a low divide leads over to the 

 head of the Rosebud. ISText in order is Soda Butte Creek, a second 

 very large branch of the East Fork. At its head easy passes lead over 

 to the heads of the Rosebud and Clark's Fork of the Yellowstone. 

 About the heads of this stream the mountains become extremely rugged. 

 They are made up of volcanic conglomerate disposed in beds or strata, 

 which have been eroded in such a way as to leave cliffs of various 

 heights, from a few feet only, to thousands of feet. The profiles of the 

 peaks show a succession of steps, of varying magnitudes and relations 

 between the rise and the tread. In this group, and just without the 

 boundary of the Park, are Index and Pilot Peaks, two of the best known 

 landmarks in the region. At their base is the Clark's Fork mining dis- 

 trict, at the head of the stream of that name. 



South of Soda Butte Creek for a few miles the mountain-forms are 

 less pronounced. Two large eastern branches of the East Fork flow in 

 from a region of smooth, easy, timbered slopes; but at the extreme 

 head of the East Fork the mountains again show themselves in all their 

 original ruggedness. A near view of this portion of the range is sur- 

 passingly grand. The material upon which nature has here worked, 

 volcanic conglomerate, is not such as produces spires and pinnacles of 

 the Gothic order, but mainly great, broad masses with precipitous sides 

 and flat summits. 



The extremest southern branches of the East Fork head as far to the 



