CHAPTER II. 
HOBACK-GREEN RIVER BASIN. 
The region occupied by the principal drainage of Hoback’s River and 
that of Green River after it leaves the Wind River Mountains is here 
considered under one head, since it presents a general uniform depres- 
sion defined on three sides by mountain barriers. But its actual con- 
dition presents some interesting features, especially its hydrography, 
the development of which is due. to the topographical department of the 
survey. 
The basin as such opens to the south so that in ascending Green River 
the entire drainage of the great recess, bounded by the Wyoming Range 
on the west, the Gros Ventre Mountains to the north, and the Wind 
River range on the east, might be readily supposed to be tributary to 
this stream. Near the south line of the district, the Green River Valley 
proper, which here has an altitude of about 7, 500 feet above tide- -water, 
is narrowed to a width of about 20 miles, its western rim resting upon a 
low divide which. curves round with its convexity to the southeast from 
the Wyoming Range north of Lead Creek where the width of the basin 
is au omented about one-third to the eastern extremity of the Gros Ventre 
Mountains. The most depressed point of the divide, which has a length 
of about 30 miles, occurs about midway, where its elevation is something 
less than 8,000 feet. To the northwest les the basin of Hoback’s River. 
The descent in that direction is comparatively rapid, soon reaching the 
general basin-level of 7,000 feet, and thence gradually declining to the 
lowest portion of the basin, 6,325 feet, where the collected waters of the 
Hoback enter the canon through the eastern ridge of the Wyoming 
Range on the way to the Snake. f 
Sufficient has been detailed to draw attention to the leading physical 
features of this basin area as a whole, and the somewhat pronounced 
contrasts presented by its dual drainage system when compared one 
with the other. It may, however, be difficult to comprehend the pro- 
cesses which have maintained the present state of things, to explain the 
causes which have been concerned in originating its system of drainage; 
especially since there exists no natural orographie definition by which 
the waters of the Green might have been held to their present course 
instead of flowing into the more depressed area drained by the Hoback. 
Were the requisite data forthcoming this subject might properly be rele- 
gated to the section reviewing the dynamical geology of the district. 
However, brief allusion to some of the conclusions arrived at in this con- 
nection may be admissible in this place. 
Tn the description of the eastern or Hoback Cation ridge of the Wyo- 
ming Mountains, in a preceding section, occasion was had to notice the 
disturbed condition of :onconformable Tertiary deposits in the immediate 
Vicinity of the folded Mesozoics of that mountain ridge. During the 
brief examinations along the foot of the Wind River Range on the east- 
202 . 
