75 



cross-ridge, is the Snow-Mass Range of the Elk Mountain group. Begin- 

 ning in latitude 390 15', longitude lOJo 10' near Sopris Peak, it runs 

 south 450 east 50 miles. In the first thirty miles are five 14,000 ft. 

 peaks. There are parallel, trough-like depressions on either side of 

 this range throughout its entire length — the lioaring and Taylor's Fork 

 Valleys on the east, and those of Eock Creek and East Eiver on the 

 west. 



The western part of the Elk Mountain group has not been surveyed, 

 nor the southern part of the Sangre De Christo and Sa watch ranges. 



These are but notes on a mountain-region, in mnwy respects the most 

 interesting in America, which is at present the field of operations of this 

 Survey. 



Several permanent barometric stations, at high altitudes, have been 

 established ; one at 14,000 feet on Mount Lincoln, and one at Fairplay 

 nearly 10,000 feet, and one at Canon City about 5,000 feet above the sea; 

 while the United States Signal-Service has in this Territory one station 

 at 5,000 feet, one at 6,000 feet, and one at 14,000 feet on Pike's Peak. 

 These are connected by spirit-level lines with the sea, and make, there- 

 fore, admirable bases for the hypsometrical survey of the region, which 

 we are carrying on by mercurial barometer, trigonometric work, and ane- 

 roid observations on minor stations. The important points are measured 

 with one or more mercurial barometers made by James Green. 



The geological and topographical surveys were extended during the 

 summer of 1873 over about 21,000 square miles. These surveys are 

 based on a system of large primary and smaller secondary triangles 

 expanded from measured bases, the whole resting upon lour points along 

 the foot of the mountains, Sherman, Denver, Colorado Springs, and 

 Trinidad, whose latitudes and longitudes have been carefully determined 

 for us by the United States Coast Survey. The positions "of the trigo- 

 nometric stations on the peaks have been deduced from these. 



The maps of these mountains, now in progress, are on a scale of two 

 miles to one inch, and drawn in horizontal contour-lines 200 feet apart. 



In the following tables are given the approximate heights and geo- 

 graphical positiousof some of the principal peaks of the mountain-ranges 

 and points in the valleys of the region surveyed last summer. The final 

 results of our computations will be published in the Annual Eeport of 

 the Survey. 



JAMES T. GAEDNER. 



Approximate elevations and geograpliical positions of prominent points. 



