REPORT ON THE PRIMARY TRIANGULATION OF COLORADO. 



By a. D. Wilson. 



CHAPTER I. 

 PKIMARY TRIANGULATIOK 



The primary triangulation party for the season of 1876 was com- 

 posed, besides myself, of William H. Holmes, geologist ; W. R. Atkinson 

 and A. L. Eedin, general assistants; Harry Yount and John Stewart, 

 packers, and Spencer Batler as cook. Dr. Hayden accompanied the 

 party for a short time himself. 



The party, outfitting at Cheyenne, marched to Denver ; thence by 

 rail to El Moro, the southern terminus of the Denver aud Rio Grande 

 Railroad. Leaving El Moro on August 18, we made a station the fol- 

 lowing day on Fisher's Peak, a point just south of Trinidad. From 

 this point we marched by way of the valley of the Purgatoire, crossed 

 the Sangre de Cristo Range by Costilla Pass; then, skirting the west 

 foot of the range toward the north, to the foot of Culebra Peak. On 

 the 24th of August we ascended this point, and, having a clear day, 

 I succeeded in taking a good set of observations on the surrounding 

 peaks. Resuming our march the following day, we camped under 

 Blanca Peak; but owing to a heavy rain-storm we were compelled to 

 remain in camp until the morning of the 28th. As I had climbed this 

 peak before, in the prosecution of my topographical work, I knew only 

 too well what was before us ; so we took as early a start as possible. 

 Following up one of the spurs that jut out to the south we were able to 

 ride with but little difficulty to the timber-line, where we were com- 

 pelled to leave our mules. Dividing the instruments, &c., between the 

 different members of the party, we scrambled our way up the debris 

 slope, about 1,800 feet, with but little difficulty, to the first outstanding 

 point. From this point a very narrow, saw-toothed ridge leads to the 

 main peak, which was only about 800 feet above us, but 1^ miles away in 

 a straight line. Taking this ridge, we scrambled along as best we 

 could, and after two and a half hours of hard work we reached the sum- 

 mit of Blanca Peak. (See report of Franklin Rhoda, for 1875, for a 

 more detailed clescription of this mountain and its surroundings.) 



This peak is one of the finest geodetic points in all Colorado, owing 

 to its height, position, and sharp, conical form. After spending some four 

 hours on the top taking the numerous angles that were necessary, we 

 began the descent, which we found less laborious, but, if possible, more 

 dangerous than the ascent. The height of this point was determined 

 by myself, in the following manner : 



Visiting this point, as I did, first in 1875, then in 1876, it gave me an 

 opportunity to take several barometric observations. Each time having 

 two barometers, I compared them before starting up the mountain; 



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