HAYDEN.] 



GEOLOGY SOUTH PAEK. 41 



extent in pockets, some of which is very rich, yielding |500 to the ton. 

 3Iuch of it is the decomposed carbonate, like the gulch-ores. 



On the east side of Mount Bross is located the Moose mine, which 

 has yielded a large amount of valuable ore. The greater part of the 

 ore is taken from the limestone. Before going further I will state what 

 I believe to be the age of all the limestones and quartzites which seem 

 to cover the highest mountains, and in which most of the valuable 

 mines are found. I think there is no doubt that they belong to the 

 Potsdam group, though I was unable to discover any fossils. Doctor 

 Peale found a few obscure forms which indicated that the group is of 

 the same age as those next to the granites in Utah, which we now know 

 are of that age. In Mosquito Gulch we find the sedimentary beds dip- 

 ping southeast 20^ to 25°, and toward the head of the gulch the schists 

 incline 15° in the same direction. There are most remarkable faults by 

 which the mass of sedimentary beds are dropped down 200 to 400 feet 

 directly, so that the schists jut up against the limestones or quartzites; 

 these faults are very common. The underlying metamorphic rocks are 

 made up in part of quartzitic sandstones, full of rounded pebbles of 

 quartz, which would indicate that they might belong to the Lauren- 

 tian series. The slides in this gulch are a prominent feature. Im- 

 mense masses have slidden down from the sides of the mountain, in 

 some instances a thousand feet or more, forming irregular terraces. 

 The faults are really very remarkable on both sides of the gulch. The 

 slides produce broad depressions near the base of the walls, in which 

 the waters accumulate, forming lakes, and these are the sources of 

 the little streams. The hundreds of gorges which have been carved 

 deep down into the sides of the mountains form channels for the little 

 streams that are fed by the melting of the snows near the crest. All these 

 little streams eventually uniting form the larger streams that traverse 

 the plains. Each one of these little branches starts from one of these 

 small emerald lakes, far up in the amphitheater, near the very water- 

 divide. Thus we can see that the miniature lake is a prominent feature of 

 mountain-scenery, and from the summit of some high mountain-peak 

 hundreds of these little emerald lakes may be seen nestled high up in 

 the very head of the gorges. They are not large, varying from 100 feet 

 in diameter to half a mile or a mile ; seldom more. On the summit 

 between Mosquito, Birdseye, and Evans Gulches, broken masses of the 

 quartzites and trachytes seem to have moved down a considerable 

 distance from their places, and are deposited in the form of windrows, 

 as if there had been glacier movements here. It is undoubtedly due to 

 the combined action of water and ice, so that there was a slow 

 movement of the masses of ice and snow down the slope, and in 

 gradually melting left those singular rows of rock. At the head of 

 Evans Gulch there is a fine exhibition of a dike parallel with the 

 strata in a nearly vertical wall 2,000 feet high. The quartzites and 

 limestones pass beneath 1,000 to 1,500 feet of trachyte. The latter 

 present the appearance of having been elevated with the stratified 

 rocks, and incline in the same direction. The dip of the trachyte is 10°, 

 and the underlying limestones and quartzites about 10° to 15° south- 

 east, then about 1 ,000 to 1,500 feet of the quartzites and limestones. There 

 is here a portion that inclines in an opposite direction^ west, toward 

 the Arkansas, but this is probably caused by the sliding down of the 

 mass. The drainage of Evans and Birdseye Gulches flows into the Ar- 

 kansas. Great masses have fallen down on the sides of the mountain, so 

 that prodigious faults occur everywhere, and the form is that of irregu- 

 lar steps. Although examinations were made here in midsummer, yet 



