150 LEWIS G. WESTGATE AND E. B. BRANSON 
between Beaver Creek, and the Sweetwater River. This is plain 
No. 3, or the Beaver Divide plain. 
This plain is best shown west of Atlantic City and South Pass 
City, where it forms an even plain on the crystalline schists, above 
which monadnocks (Fig. 6), usually of granite, rise abruptly from 
a few score to one or two hundred feet. The plain, much cut away, 
continues west between the Granite Hills and the main range about 
the headwaters of the Sweetwater, where it cuts both the crystallines 
Fic. 6.—View of plain No. 3 and monadnocks, west of South Pass City 
and gravels which had earlier been deposited on an irregularly 
eroded granite surface. This same plain extends east from the 
south end of the range for over thirty miles along the divide between 
the Sweetwater River and Beaver Creek cutting in this area prac- 
tically all the post-crystalline rocks of the region—the inclined 
Paleozoics and Mesozoics, and the horizontal and consolidated 
Tertiaries. In a few places residuals of each of these rocks rise 
above No. 3. 
North from Atlantic City, where Nos. 3 and 4 meet, they differ 
