.,,^,-1 GEOLOGY FEOM ELK MOUNTAINS TO MIDDLE PARK. 73 



face, while the quartzites weathered in rounded forms, the thin layers 

 dropping off concentrically. 



The composition of those rocks would indicate that the gneissic or 

 granite rocks were very largely drawn upon for the materials. The two 

 groups described above will aggregate at this locality about 1,200 or 

 1,500 feet in thickness ; but as we descend the river we can see on the 

 summits of the mountain-ridge a great additional thickness, so that the 

 whole must sum up at least 3,000 or 4,000 feet. The character and 

 texture varies much in different localities, but the description given 

 above will apply to a great thickness of beds which extend over a 

 greater or less area west of the Sawatch range to the Colorado River. 



Our trip down the Eagle JEliver had for its principal object the dis- 

 covery of some way of access to the mountain of the Holy Cross. A 

 little stream joins the Eagle River from the west side, which rises among 

 the group of mountain-peaks of which the Holy Cross is most conspic- 

 uous. The valley of this stream varies from one-eighth to one-fourth of 

 a mile in width, and is about eight or ten miles in length, and so cov- 

 ered with the rounded glaciated forms of granite that it was impossible 

 to ascend it with our pack-trains. We were obliged to descend the 

 river about three miles and then climb the steep mountain-side over a 

 net-work of fallen timber. The obstructions to traveling were very 

 great. We often labored for a day or two to find some path to approach 

 the mountain-peak, and were obliged to cut our way through the fallen 

 timber, and finally succeeded in getting within about five miles of the 

 base of the peak. 



The most remarkable feature of this wonderful region is the proof of 

 a great ancient glacier which must have filled up the valley from mouth 

 to source. The bottom, extending high up on either side, is covered 

 with the rounded granite masses, varying in size from a few feet to sev- 

 eral hundred feet length; so that, looking down upon them from a high 

 point, they resemble a huge flock of sheep, and from this fact they have 

 received from the Alpine geologists of Europe the appellation of 

 "Roches Moutonnes." It is most probable the valley itself has been 

 worn out of the granite mass. The mountains on either side rise to the 

 height of 2,000 to 3,000 feet above the valley, and the glacial markings 

 are visible 1,200 to i,500 feet. The morainal deposits on the northwest 

 side reach a height of 1,200 feet above the stream and form a sort of 

 irregular terrace, which, when cut through by the little side-streams, 

 show that it is made up of gravel and bowlders much worn. In some 

 instances there are ^well-worn cavities in the sides of the mountains, 

 showing ho\\ the running water, in connection with a mass of rock, 

 formed the cavity much as a " pot-hole " is made in our streams at the 

 present time. 



Many of the "sheep-backs" are still covered with a crust like enamel, 

 but usually this has peeled off. There is no doubt that all these rounded 

 granite masses were originally covered with what may be called a glacial 

 crust which has scaled off, so that only remnants remain at the present 

 time. The rounded masses of granite are mostly oblong in form, or lie in 

 parallel lines, as if the little stream had originally occupied a dozen or 

 more channels parallel to each other. 



The amphitheaters on the west side of the mountain are quite numer- 

 ous, at least a half-dozen in number, giving birth to as many streams that 

 flow down the mountain-side. These unite in the valley, and form a 

 good-sized stream, 150 feet wide and 2 feet in depth. 



At the upper end there is a boggy meadow covered with high, coarse 

 grass. This meadow is about one-fourth of a mile in length and about 



