182 REPORT UNITED STATES GEOLOGICAL SURVEY. 
however, that at the time of our visit gaseous emissions were far less 
noticeable than one would be led to infer was the case fifty years ago 
at the time of Mr. Parker’s observations. 
For a few miles south of the Hoback Caton the main mountain ridge 
presents a sort of double crest, although the eastern and more prominent 
is the main drainage crest, the western one having the relations of huge 
buttress-spurs with outlying eminences but little inferior in height to 
the main ridge. Its structure throughout is that of two parallel folds 
separated by a shallow synclinal trough. The eastern, or Station II 
ridge, presents an abrupt and often escarped wall 500 to 800 feet high, 
facing the Hoback Basin, in which the edges of the westerly dipping 
strata are exposed. These consist chiefly of red and fiesh-colored Trias- 
sic sandstones, capped by leaden shales and drab limestones of the lower 
measures of the Jura. From the foot of the escarpment on the east, a 
rugged wooded belt steeply descends into the parallel valley, in which 
the strata, though much disturbed and complicated, apparently form 
the eastern flank of an anticlinal fold. The above state of things is 
plainly indicated in the vicinity of Station Il, where outlying hog-back 
ridges facing the monoclinal crest are made up of the Triassic red sand- 
stones. dipping steeply to the east. Lower in the slope there are indi- 
cations of a second lower fold, also arched by the Trias, whose east flank 
declines into the synclinal trongh occupied by the parallel valley, and 
which is partially filled with Jurassic deposits. The eastern flank of 
this synclinal is the same as the outer barrier ridge already described. 
The relative position of the folds and their component strata are indi- 
cated in the section diagram across this part. of the ridge. But while 
the above-mentioned structural features may be regarded as normal in 
this part of the east slope of the Hoback Canon ridge, it was undoubtedly 
subject to greater or less local variation, recording the variable action 
of the dynamical forces which uplifted and folded the strata into a 
broad north-south mountain zone. 
. From the Hoback Lasin, looking up the valley of the main stream to- 
wards its sources, a comprehensive view is gained of the eastern wall of 
the ridge extending from Station VI to the south line of the district, 
and which affords a fair knowledge of its geological structure. The 
outlying eastern slope is largely if not entirely enveloped by the Ter- 
tiary deposits of the basin, which a little farther to the south extend 
high up on the mountain ridge. Nothing could more strongly contrast 
with the abrupt, broken mountain declivity than do the long sloping 
benches that here descend the mountain flank, reaching far out into the 
middle of the basin area. Even tothe north, where the Tertiary deposits 
have been much more eroded by the streams, they still retain to no in- 
considerable extent their distinctive bench features. But at a distance 
what may appear to be uninterrupted, smooth slopes, on nearer approach 
generally prove to be high benches, whose almost inaccessible sides are 
scored by the wildest gullies, while the comparative levels above are 
densely clothed with pine and spruce amongst which the fires have 
wrought wide-spread devastation, the interlacing of the fallen tree- 
trunks erecting almost insurmountable barriers to travel. 
As seen trom this pvint of view, the ridge in the neighborhood of 
Station VI shows a broad synclinal or sag in the component strata, 
based upon heavy deposits of red sandstone. The trough of the de- 
pression is filled with variegated chocolate-drab beds, which are separated 
from the “red beds” by an intermediate bufi-colored deposit forming 
escarpments in either flank of the sag, remnants of reddish sandstone 
occulring above the drab beds. The basis rocks of the exposed section 
