REPORT ON THE PRIMARY TRIANGULATION OF 1877 AND 1878. 



By a. D. Wilson. 



In the spring of 1877, lia\ing completed the work in Colorado the 

 previous season, it was determined that the survey should be carried 

 north into Wyoming. The belt of country lying along and including 

 the Union Pacific Eailroad had been surveyed and mapped by the 

 '•'- Geological Exploration of the Fortieth Parallel" under Clarence King. 

 Therefore the work was commenced at the northern line of this belt at 

 Fort Steele, and thence carried north and west, including rectangles Nos. 

 45, 56, and 57, included between longitudes 107° and lli^°, and from lati- 

 tudes 41° 45' to 44° 15'. 



Three topographical parties were sent out ; to each was assigned a 

 rectangle. Mr. Chittenden was given rectangle No. 57, which he nearly 

 completed ; Mr. Gannett had No. 56, who completed his section ; while 

 Mr. Bechler had No. 45. This rectangle included so much high and diffi- 

 cult country, and Mr. Bechler being compelled to leave the field earlier 

 than he would have done on account of the Indian troubles, he did not 

 finish more than half of this section. 



The parties were all fitted out at Cheyenne, Wyo., and then shipped 

 along the railroad to the most convenient points to their work ; my party 

 stopping at Eawlins, Mr. Chittenden's at Salt Well, Mr. Gannett's at 

 Green Kiver, while Mr. Bechler's weut through to Ogden. The primary 

 triangulation was, as usual, placed in my charge. Arriving at Eawlins 

 Springs May 31, I established my camp about two miles out of town, at 

 Cherokee Springs. After reconnoitering the country in the vicinity of 

 Eawlins, I selected -a i)lace west of the town, between Separation and 

 Cherokee Peaks, as the most favorable spot on which to measure a base- 

 line from which to start this work. Although the ground was not all 

 that I could have desired, it was the best that could be found in the 

 vicinity, nor was there as much room as I wanted ; but owing to the 

 favorable conditions it offered for connecting with the mountain i)eaks, 

 I selected it in preference to any other that I could find. 



MEASUREMENT OF THE EAWLINS BASE-LINE. 



The central portion of the line as selected lay along a "tangent" of 

 the railroad, and the remainder extended over a sage-brush flat where 

 there was considerable brush ; and the ground being full of small hum- 

 mocks, I determined to measure the portion lying along the centre of 

 the track, which was about one mile in length, and to expand by means 

 of signals placed so as to form nearly equilateral triangles, and in this 

 manner extend the base either way as far as the conditions of the surface 

 would allow. 



The line was measured along the centre of the track with a fifty-foot 

 Stackpole compensated steel tape \ this tape was compared with a Ches- 



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