st. JOHN.|}] WIND RIVER MOUNTAINS—-METAMORPHIC ROCKS. D4) 
sedimentary rocks locally forms two or more distinct subordinate paral- 
lel ridges whose aggregate makes up an outlying mountain ridge that 
may be traced nearly the entire length of the range. The latter, as seen 
from the valley, forms the prominent orographi¢ feature of the range, 
the high Archzan summit only appearing here and there up through 
the openings formed by the canons of the descending streams; but from 
the higher or inner crests of the sedimentary belt the broken Archean 
basin area is overlooked, terminated by the precipitous eastern wall of 
the culminating summit ridge only a few miles distant. The appearance 
of this lofty mountain barrier is indescribably varied and sublime. The 
stream beds are choked with confused piles of bowlders, and the rock 
surfaces everywhere bear unmistakable evidence of glacial action. The 
basins of all the streams that rise within the Archean area present 
more or less perfect examples of roches moutonues ; indeed the whole 
region s replete in these most interesting and varied phenomena. 
On the west, the summit ridge is flanked by an exceedingly rugged 
elevated Archean plateau or bench several miles in width. Thestreams 
that penetrate to the main crest flowin profound gorges walled by gran- 
ite often many miles in length, as is the case with Fremont’s Creek and 
Green River. The lesser drainage channels, rising in the outer edge of 
the outlying mountain plateau, often head in a cul de sac hemmed in 
between precipitous granite escarpments hundreds of feet in height, 
and flow out through cafions scarcely inferior in the grandeur of their 
scenic surroundings to those eroded by the principal water courses that 
drain the western flank of the range. Throughout nearly its entire 
extent within this district, the western edge of the Alpine plateau pre- 
sents the appearance of a huge terrace escarpment which abruptly 
breaks down to the comparatively low, narrow belt of foot hills that 
slope into the valley of the Green River. Ancient glacial phenomena 
are here met with on a scale of great magnitude. Indeed the proper 
investigation of this branch of the oeolosy of the mountains would 
profitably occupy many months. 
Although little opportunity was presented for the systematic study 
of the central area of the mountains, such observations as were made 
in the northern portion of the range sustain the inference that the nu- 
cleal rocks are largely metar 1orphie. This is clearly the case along the 
west flank in the vicinity of Green River Cation, as also at Union Peak, 
and along the eastern flank, where these rocks are revealed in the mount. 
ain valleys of Little Wind River and the streams of the north, where- 
ever the latter were ascended beyond the limits of the unconformably 
superimposed Paleozoic formations. But with the meager data in hands, 
it would be impossible to attempt to define the lithologic and structural 
features of the rocks of this area, the successful elucidation of which 
would require a liberal allowance of time and facilities such as were be- 
yond our means of supplying. 
Along the mountain course of the tributary four or five miles north of 
Green River the gray banded gneissose ledges, associated with feldspar 
and talcose belts, have a general westernly inclination, the rock present- 
ing locally a brecciated appearance, with angular hor nblendic inelu- 
sions. The feldspar constituents weather into asoft, white earth, which 
may in part account for the milky discoloration of the waters, of the 
Green above the lakes. Ascending this stream to its sources in the 
summit plateau 8 miles south of Union Peak, the same gneissic rocks 
were still prevalent, the glaciated surface bringing out ‘the contorted 
lamination and ramifications of quartz and feldspar veins with which 
the rock is traversed. Just above a narrow rock-hemmed gorge, down 
