488 GEOLOGICAL SURVEY OF THE TERRITORIES. 



and bluffs reaching seven to eight hundred feet above the valley. At 

 the lower end a narrow gate- way leads out to the Rio Grande; and, at 

 the upper end, a beautiful lake occupies the highest part. Just above 

 this, Clear Creek cuts through the ridge on the west side, and flows out 

 through Antelope Park. The whole mass of this basin has, undoubt- 

 edly, fallen in; and, at one time, Antelope Park must have jutted up 

 against the side of the mountain. We made the ascent of the peak 

 from the sink, riding our mules the whole distance, except the first part 

 of the climb, from the sink up to the ridge. On the summit we found 

 the snow about a foot and a half deep. A large bear had left his tracks 

 all over it. We found the slope to the east quite gradual and made the 

 descent on that side instead of going down the way we came up. After 

 camping at a point on the road to the south of Bristol Head, we moved 

 down the Eio Grande. The only place of special interest on the way 

 was Wagon-Wheel Gap, where the river passes for a few hundred yards 

 between two high bluffs, about 300 feet apart. This point has evidently 

 been, in times past, a great battle-ground between the Utes and their 

 enemies of the plains, the Cheyeunes, Arapahoes, &c. Many little 

 heaps of rocks on the south bluff seem to have done service as rifle-pits. 

 The toll-gate for the San Juan road is situated near this place. 



We arrived at Del Norte on October 10. The town contains, several 

 hundred inhabitants, and at the present time does a considerable busi- 

 ness with the San Juan mines. Leaving Del Norte we traveled across 

 San Luis Valley; far behind us we could see a new but apparently 

 greater storm than we had yet passed through gathering around the 

 distant mountains. Crossing over Mosca Pass and down Huerfano 

 Park we reached Pueblo October 18. The next morning we took the 

 cars on the narrow-gauge railway, and in the evening arrived at Den- 

 ver, our point o*f beginning. 



METHODS USED IN DETERMINING THE ELEVATION OF 

 POINTS IN THE DISTRICT. 



All the elevations given in this report depend upon readings of a 

 mercurial barometer. Where a standard barometer, whose elevation is 

 well determined, is within a short distance, this instrument gives a very 

 good determination of elevation. In the past summer, however, it was 

 quite impossible to establish a base barometer in the vicinity of the 

 region surveyed, without great expense. All the readings had to be 

 referred to distant stations. Readings on high peaks were referred to 

 the Signal-Service barometer on Pike's Peak, at an elevation of 14,147 

 feet above the sea, while readings on all points under 12,000 feet were 

 referred to the barometer of the United States Geological Survey at 

 Fairplay, whose elevation is 9,904.5 feet. The first of these is one hun- 

 dred and fift/miles distant in a straight line from the central part of the 

 San Juan country, while the second is one hundred and twenty-five miles 

 distant. These distances are too great to give accurate results with the 

 barometer. At several points in the region we succeeded in getting two 

 readings at the same point at intervals of several days, but finding that 

 the resulting heights, as calculated by reference to those distant bases, did 

 not agree well enough, it was resolved to collect together all the data 

 possible from the field-notes, and see if a fair trigonometric connection 

 between the mountain-peaks could not be established. The result was, 

 under the circumstances, highly satisfactory. It must be remembered, 



