1878. | United States Survey of the Territories, 97 
and mapped in detail by the Survey of the Fortieth Parallel, 
under Clarence King, Esq., it was deemed best to commence at 
the northern line of that work, and continue northward and west- 
ward, taking for the season of 1877 the country from Fort 
Steele, Wyoming Territory, to Ogden, Utah, or, more exactly, 
from longitude 107° to 112°, and northward to the Yellowstone 
Park. ; 
The primary-triangulation party, in charge of Mr. A. D. Wil- 
son, chief topographer of the survey, took the field from Raw- 
lins Springs, W. T. Near this point a base-line was measured 
with great accuracy, from which a net-work of triangles was 
extended over the country to the north and west, locating at 
intervals of from twenty to thirty miles, some prominent peaks 
upon which stone monuments were built, in order that the topog- 
raphers could recognize the points thus fixed for them. Upon 
these points was based the system of secondary triangulation. 
_ From the base at Rawlins, the work was carried northward to 
the Sweetwater mountains, and thence to the Wind River range. 
Upon some of the more prominent peaks of the latter range, such 
as Frémont’s peak, the stations were made with much difficulty, 
owing to the great masses of snow found there during the month 
of June, when the party was working. From this range the 
work was carried across the Green River basin to the mountains 
on the west and north, where several stations were made. The 
work was resumed to the west as far as Fort Hall, Idaho, and 
thence south to the vicinity of Bear lake, where another base, or 
base of verification, was measured; thence south as far as Ogden 
and Evanston, connecting with the triangulation of the Fortieth 
Parallel Survey at these points. From Evanston the party marched 
eastward, making some stations north of the railroad, thus bring- 
ing the work back to the point of beginning, Rawlins Springs, 
where the party was disbanded for the season. 
The area assigned to the Green River division, under the direc- 
tion of Mr. Henry Gannett, was rectangle No. 56, which is limited 
_ on the east and west by the meridians of 109° 30’ and 112°, and 
on the north and south by the parallels of 43° and 41° 45’. This 
= is an area of about 11,000 square miles, lying in parts of Wyo- . 
_ ming, Utah and Idaho. The party took the field at Green River 
city, Wyoming, on June Ist. They first surveyed the drainage of 
Green River basin. For this purpose they travelled ug the Big 
