PEALE] GEOLOGY ARKANSAS RIVER. 239 



the park we find on the east several high hills of trachyte. There is a 

 small branch coming in here which seems to form the boundary between 

 the trachyte and the granite. This is a portion of the same eruptive 

 material seen east of the salt-works, of which it is the continuation 

 southward. I shall reserve the consideration of the Arkansas Valley to 

 the next chapter. 



CHAPTEE III. 



ARKANSAS VALLEY — EAGLE RIVER — SAWATCH RANGE. 



The Arkansas River, in our district, has a course a few degrees east 

 of south. On the east side we have the Park range, separating the 

 valley from South Park, while on the west is the Sawatch, or main range 

 of the Rocky Mountains, forming the continental divide. It has here, 

 perhaps, its culmination. The range to the southward of Mount Bowles 

 falls off, as it also does north of the mountain of the Holy Cross, which 

 is the last peak in the range in this direction. Before reaching this 

 point the water-divide sweeps around the head of the Arkansas to the 

 eastward. In the Sawatch range we have first Mount Bowles, rising 

 14,106 feet above sea-level. About twelve miles farther north is Mount 

 Harvard, having an elevation of 14,208 feet. The next high point meas- 

 ured was La Plata Mount, which is eleven miles northeast of Harvard: 

 its height is 14,126 feet. Grizzly Peak, at the head of Lake Creek, is 

 about seven miles from La Plata, and a little north of east from it. Its 

 elevation is 13,786 feet. Six miles east of north from La Plata is Mount 

 Elbert, named in honorof the governor of Colorado: its elevation is 14,150 

 feet. Six miles farther north is Massive Mountain, having an elevation 

 of 14,192. North of Massive Mountain the range is comparatively low 

 until we near the mountain of the Holy Cross, when it rises again. The 

 elevation of the Holy Cross is 13,478 : it is about eighteen miles north 

 of Massive Mountain. Beyond it, the range dies out, and we have Eagle 

 River sweeping around to reach the Grand River. As we have seen in 

 the latter part of the last chapter. Trout Creek flows through granitic 

 rocks, which continue to the valley of the Arkansas and are the pro- 

 longation of those seen west of Buffalo Peaks. The granite is gen- 

 erally coarse and of a reddish color, with seams of white quartz. The 

 bedding is probably the same as we saw at the peaks, that is, to the north- 

 east. The eruptive rock that is seen near the head of the creek extends 

 to the southward and southeast, and will be fully treated of in Dr. End- 

 lich's report. I did not go farther down the Arkansas Valley than oppo- 

 site the mouth of Trout Creek. Here we have a beautiful broad valley, 

 "With streams coming in from either side, and cutting deep terraces in 

 the deposits of drift. There is a gradual slope from either side to the 

 river. The main part of the valley lies on the west side, and it fs here 

 that the terraces are most conspicuous. The valley is park-like, and is 

 about six miles wide : it extends southward into Dr. Endlich's district. 

 I found nothing but drift as far as I had time to examine the deposits. 

 I was unable to determine whether the drift is of glacial origin or not. 

 It is probable, however, that it is, for in the caiions in the range far- 

 ther north we have abundant evidence of glacial action. 



Below the mouth of Trout Creek, Dr. Hayden, in 1869, found Tertiary 

 beds. He refers to them as follows :* " On the west side of the Arkan- 



* Report, 1869, pugo 177. 



