42 GEOLOGICAL SURVEY OF THE TERRITORIES. 



■with sage at this time, but every acre of them could be cultivated by 

 irrigation, and the soil is as fertile as any of the fruitful lands of Salt 

 Lake Valley. The miocene beds of the Bridger Group jut up against the 

 sides of the mountains in a nearly horizontal position. Up among the 

 foot-hills I found the bones of a turtle, the teeth and jaws of a mammal, 

 and an abundance of fresh-water shells, of the genus Planorbis. I am 

 now inclined to think tbat the long high ridges that extend down from the 

 flanks of the mountains between each main stream or its branches, are 

 composed of modern tertiary beds. Still they are so smooth and so 

 thickly grassed over, and covered with groves of pine and aspen, that I 

 could never find a locality where the rocks were exposed, so that I could 

 obtain a connected section. The surface is covered very thickly with 

 rounded boulders of reddish sandstone and quartzite, with some masses 

 of carboniferous limestone. The ascent is very gradual, and the roads 

 excellent, almost to the summits of the range, at least to an elevation 

 of 11,000 feet above the sea. 



Both Smith's and Black's Forks separate into numerous branches, and 

 between each one is a lofty, precipitous ridge, which extends down from 

 near the summit of the mountains in the form of steps or abrupt points. 

 Pheasant Point and Porcupine Point are examples of this kind. It is a 

 curious fact, however, that none of these ridges ever reveal their interior 

 character, being clothed with a dense growth of pine and aspen, or in the 

 open places, on hill or in valley, thickly with grass and a deep soil. For 

 ten miles at least not a trace of the basis rocks could be found in the 

 channels of the streams. Spruce Ridge, between the sources of the Muddy 

 and the valley of Bear River, revealed the fact that there is an immense 

 deposit of drift covering a belt along the flanks of the mountains from 

 ten to twenty miles in width, extending in some places nearly to the 

 crest of the range. The upper portion of this drift is composed of fine 

 arenaceous clays, covered with a deep, rich, vegetable soil. It therefore 

 sustains a luxuriant vegetation up to an elevation of nearly 12,000 feet. 

 The mountain rises in steps, because there are ridges of elevation ; 

 hence, Judge Carter has given this range the appropriate name of 

 " Terrace Mountains." 



Thus we have two kinds of ridges; those of elevation, which are par- 

 allel with the axis, and those of erosion, which are parallel with the 

 valleys of the streams, and radiate from the axis at right angles to the 

 ridges of elevation. The first locality, between Smith's Fork and Black's 

 Fork, that we observed rocks in place was at Photograph ridge; a lofty 

 upheaval of carboniferous limestone, inclining at an angle of 40°. The 

 elevation of the crest was determined by the barometer to be 10,829 feet. 

 This ridge extends across Black's Fork, with a trend about northeast 

 and southwest. From this ridge to the axis of elevation there is a 

 series of sandstone ridges, passing gradually into red and gray quartz- 

 ites. These ridges rise, like steps, to the crest of the range. 



The first ridge is composed of dull, purplish sandstone of various 

 degrees of texture, from a compact sandstone to a pebbly conglomerate. 

 The quantity of broken rocks and debris is wonderful, rising like a wall 

 one hundred to two hundred feet high. Then comes a broad, grassy 

 valley and a second ridge of sandstone, though a portion of this ridge 

 is covered with the drift deposit, so that the sandstones are seen only 

 in the sides of the valleys of Smith's and Black's Forks. The inclination 

 of these sandstones is about 35° northwest. At the foot of the ridge 

 next io the crest of the mountains there is a broad valley like a plateau. 

 This has the appearance of an elegantly prepared lawn, so thickly and 

 evenly is it covered with grass. It is 11,869 feet, and 1,100 feet above the 



