5 5 



series of the underlying- sedimentary rocks were first laid down and sub- 

 sequently worn away to different depths, according- to the hardness of 

 their material, previous to the escape of the overflowing lava. The en- 

 tire region, which might appropriately be called the Volcanic Mountains, 

 presents a succession of tall peaks and broken ridges of the most rugged 

 and formidable character. The loftv barren cliffs, with but scanty veae- 

 tation, are covered with perpetual snow, which adds a deeper gloom to 

 the somber nakedness of the rocks. To the northward, on the other hand, 

 not only the igneous rocks, if they ever existed there, but all the sedi- 

 mentary beds, excepting in isolated patches, have been swept away b\ 

 the erosive forces, while the metamorphic rocks have been thrust up- 

 ward forming a region of rugged and lofty mountains composed exclti- 

 sively of feldspathic quartzite and dark-colored gneisses, known as the 

 Hear Tooth Range. Over a large portion of this area the granite rocks are 

 rounded off into those peculiar oval convex prominences which have been 

 called "Sheep-backs/' and smoothly polished by the action of glaciers 

 Fig. 2). All along the north branch of Clark's Fork and northward, 

 including a space of several hundred square miles, the surface consists 

 of those polished sheep-backs of various sizes and heights, in the spaces 

 between which are thousands of small lakes skirted with Abies mbalpina, 

 Picea JEngelmanni, Populiis tremuloides, and a shubbery of Ceanothus 

 velutinuij Potent ilia f met ieosa, and other subalpine species. 



A prominent feature of this region is the Bear Tooth Mountain, an iso- 

 lated peak from which the range takes its name, composed of sediment- 

 ary rocks, which have escaped from the general destruction and remain 

 standing like an island in the midst of an area denuded of everything' 

 dow n to the primordial granite. It has an elevation of 10,050 feet above 

 the sea level, and 1,250 above the surrounding surface. The upper 

 layers are a hard, yellowish- white eherty limestone, with Jurassic fossils, 

 below which is about 250 feet of brick-red sandstone, and then 000 feet 

 of a hard conglomerate limestone, composed of oval, flattened, pebble-like 

 masses cemented together by a greenish material, but presenting a dull 

 gray or drab color on the weathered surface, which lies directly in con- 

 tact with a reddish and whitish streaked bedded sandstone 100 feet* 

 presumably Potsdam, below which is 50 feet .of dark triable gneiss, with 

 masses of biolite and feldspar seams, resting on the underlying granite. 



(Fig- 3). 



From Bear-Tooth Peak eastward to the plains, about 30 miles, is a suc- 

 cession of granite ridges, the highest crest of which is sometimes capped 



by patches of the reddish bedded sandstone supposed to be of Potsdam 



age, witli no trace of any rock of more recent date until we reach the 



precipitous eastern boundary, where the conglomerate limestone, red 



sandstone, &c, again appear, tilted at an angle of 20° beyond the per- 

 pendicular, which gradually subside to their normal position under a 

 surface of lignite beds over the valley of Kocky Creek, as it Bows toward 

 the Yellowstone. The altitude varies from 8,500 to 10,500 feet, with a 



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