Geology and Mineralogy. 57 
The primary-triangulation party, upon the work of which that 
of all the topographical parties is based, was, as usual, in charge 
of Mr. A. D. Wilson, Chief Topographer. He took the field at 
The area embraces about 28,000 square miles, and within it twenty- 
tant. From these, connections were made at six points with the 
triangulation of the Survey of the 40th parallel. 
In addition there were three other fully equipped divisions for 
topographical and geological work, and another under the direc- 
tion of Dr. C. A. White, for special geological and paleontological 
work. 
The party first surveyed that portion of the district which is 
ohn y j i ) 
sedimentary origin. A comparatively small space is occupied by 
strata of Silurian age; the others range from Carboniferous to 
beds of the Green River and Bridger groups, probably of Eocene 
age. Coal was found to exist in large quantity on Upper Bear 
River and its tributaries, and also on some of the branches of 
Green River, being especially abundant between Twin Creek and 
Ham’s Fork. In the Malade valley, Dr. Peale observed deposits 
that are of later age than the Bridger group, but still, probably of 
Tertiary age, : : 
The Sweetwater division in charge of Mr. G. B. Chittenden, 
* A map showin ri trian ions of this survey has quite recently 
been published. $e te 
