230 REPORT UNITED STATES GEOLOGICAL SURVEY. 
which the stream plunges, the schistose ledges curve over in an anti- 
clinal, on the east flank of which the inclination is 30°, + —. In the vi- 
emity a well marked porphyry dike appears on the north side of the 
stream, and may be traced at intervals to the ESE. and WNW., 
along its line of strike, a distance of a few miles. The dike is perhaps 
100 feet across, and has a slight southerly inclination from the vertical ; 
to the east Mr. Perry reports it divided into three distinct branches, 
holding the same general course. In texture and lithology it’ varies 
from coarse mottled to dark green chloritic hue, weathering dark rusty, 
like trap. Its appearance is exactly similar to the dikes occurring in Mt. 
Hayden and Mt. Moran in the Téton range. 
On the summit of the range between the above-mentioned tributary 
of Green River and Campbell’s Fork of Wind River, knobby outliers of 
feldspathic granitoid gneiss rise above the plateau that here forms the 
summit. The rock weathers in blocks, recalling the granite knobs on 
the summit of the Laramie Range in the vicinity of Sherman Station, on 
the Union Pacific Railway. The gneiss, which is traversed by quartz 
veins, is represented by many varieties, including chloritic talcose and 
mica schists, the latter sometimes garnetiferous. The quartz veins have 
every appearance of segregated origin, resembling auriferous lodes ; 
but the gravel deposits of the west side streams revealed no gold. 
South of Green River Cafion the west flank of the mountain appears to 
be largely made up of a coarse feldspathic granitoid rock, the relations 
of which to the gneissic ledges was not ascertained; but judging from 
the evidence afforded by the erratic materials composing the great 
morainic ridges along this mountain foot the latter ledges must occur 
in the interior of the range. 
All along the east side of the Wind River Range, wherever we pene- 
trated to the Archean area, these rocks were found to be composed of 
gneissic and various schistose rocks, including hornblende, upon which 
the upraised Paleozoic formations rest, forming a more or less well- 
marked outer mountain ridge with escarped face towards the main sum- 
mitcrest. Union Peak, the most northerly eminence of the range, nearly 
11,600 feet altitude, is made up of beautifully laminated and much con- 
torted gray, rusty-weathered gneissic ledges, including hornblende and 
mica schists, Showing a generai westerly inclination at variable angles. 
On the northeast shoulder of the mountain, a short distance from the 
summit, feldspathic granite appears in characteristic blocky exposures, 
identical with the knobs previously mentioned occurring in the plateau 
summit 6 miles to the SSH. Perhaps a couple of hundred yards 
south (2) of the peak a well marked granite dike, 30 yards in width, 
crosses a high shoulder of the mountain, strike about east-west, and 
dipping southwards at an angle of 45°, + —, which is inclosed between 
gray gneissic walls, similar to that forming the summit. The dike con- 
sists of flesh-colored feldspar with segregations of mica and quartz, the 
latter sometimes replacing the silvery mica as pseudomorphs. Five 
miles to the north, in the vicinity of the trail over Union Pass, low, 
rugged exposures of feld-spathic granite outcrop, forming the most 
northerly observed exhibitions of the nucleal rocks of the range. 
In the upper mountain basin of Warm Water Creek, above the cafion 
at Clarke’s Camp, placer mines have been recently worked. At the time 
of our visit the mines were temporarily abandoned, nor could definite 
information be gained as to the character and richness of the deposits. 
From time to time considerable prospecting has been performed in this 
vicinity, test-pits having been carried high up on the summit of the 
pass. Mr. Charles Blackburn, who accompanied the party, describes 
