214 GEOLOGICAL SURVEY OF THE TERRITORIES. 



mica. The quartzite and slate are both very much changed, and are each 

 about 60 feet in thickness. The slate weathers on the surface a rusty-bro wu 

 color. The dip is south 55° east ; angle of inclination, 50°. I am at a 

 loss as to the position of these beds. They are fragments that have 

 been caught and lifted up, but they are so changed and too few in num- 

 ber to say anything definite of them. They could not be traced to the 

 southward, and our time was too limited to try and follow them to the 

 northward. The mountain itself is composed of a fine-grained granite 

 of a gray color, and, I take it, is eruptive. In it are seams of a dark- 

 green porphyritic rock, in which the matrix is very compact, the crystals 

 being a white feldspar. The mountain lias been called Crater Mountain, a 

 name derived from its peculiar crater-like shaiDC. Ascending the eastern 

 side on a slope of about 30° over a mass of shingle like dSbris, on reaching 

 the summit we are on the edge of a crater-like depression, tlie walls being 

 perfect, except on the southern side. It is not, however, a true crater, 

 the shape being the result, in all probability, of erosion, due partly, per- 

 haps, to past glacial action. This form is common in the mountains on 

 the west side of the park and in the Sawatch Eange on the west side 

 of the Arkansas. In the latter we have abundant evidence of former 

 glacial action in the moraines, which, as we shall see further on, are 

 found along all the streams. Besides the depression below the main 

 peak there are three others, two facing the south and one looking toward 

 the north. Between Tarryall Creek and Michigan Creek are high hills 

 or mountains comiDOsed of a porphyritic volcanic rock, approaching the 

 character of a phonolytic trachyte. The summits of these hills are 

 rounded, and their slopes are covered with slab-like masses, which, on 

 the surface, weather to a rusty color, and ring under the blows of the 

 hammer. Following the edge of these hills around to the town of Ham- 

 ilton, on Tarryall Creek, and then going up stream a short distance 

 above the town, an outcrop of quartzite appears, dipping a few degrees- 

 to the south of east under the volcanic (*?) rock. At this point is an 

 abrupt turn in the coarse of the creek. Until it reaches this place it 

 follows the strike of the quartzite, but here breaks through them at 

 right angles. Beneath the quartzite is a soft grayish-white sandstone, 

 and in the banks of the creek are exposures of red sandstone. 

 The quartzite and gray sandstones are, doubtless, Cretaceous ^STo. 

 1, and a continuation of beds farther southward, between Trout 

 Creek and Crooked Creek. They are in line with them, and the 

 strike corresponds precisely. The red sandstones are Triassic, and have 

 £t dip of about 5°. They form the bed-rock upon which the auriferous 

 gravel rests. This gravel is about 10 feet thick, and has yielded a great 

 deal of gold. The mines in this vicinity are treated of in Dr. Endlich'S 

 report. About five miles west of Hamilton is the mountain called Silver 

 Heels, having an elevation of 13,731 feet. We ascended it, and on the 

 eastern slope I made a partial section of it, as follows : 



Section No. 8. 



1. The summit of the peak is made up of an eruptive rock resembling 



that in the hills above Hamilton. This, with a few layers of 

 coarse micaceous sandstone, sometimes conglomeritic, extends 

 for about 1,500 feet. The slope here is very small, only about 

 5°, and the beds are so covered with debris that it is impossible 

 to define them. 



2. Metamorphosed sandstone and volcanic rock. The sandstone con- 



tains rather large rounded pebbles. The volcanic rock is beneath 



