st. JoHN.] CONTINENTAL WATER-SHED—MT. LEIDY HIGHLANDS. 225 
sive areas in the slopes in the vicinity of Union Pass. Just north, how- 
ever, on the head of Warm Spring Creek and upper drainage flowing to 
the Gros Ventre, they appear in the blufis, showing nearly horizontal 
strata of yellow and brown sandy clays and soft yellow sandstones. 
The ridges separating the drainage are here often overspread by quan- 
tities of water-worn and rounded quartz pebbles, strikingly like the ma- 
terial derived from the degradation of the before-mentioned conglomer- 
ate lower down the Gros Ventre. But the surface is generally envel- 
oped in the morainic débris consisting chiefly of Archean bowlders. Ap- 
proaching Station XX VIII, alow conical eminence rising on the summit 
of the watershed 11 miles to the northwest of Union Peak, attaining 
an altitude of 10,142 feet, the drift material shows constantly-increasing 
accessions of volcanic fragments and chalcedony. The station eminence 
is composed of a brownish-green easily-weathered deposit, intermingled 
with which, at the surface at least, occur quantities of basalt, red to 
brown and dark scoriaceous lavas, drab, brown, and pink trachyte, vol- 
canic conglomerate and green-stained quartz conglomerate, such as oc- 
curs in Togwotee Pass, together with beautiful green volcanic glass and 
chaleedony, and fragments of fossil wood. Indeed, the hill would seem 
to be made up of fragmentary volcanic products of a kind identical with 
the great volcanic deposits in the neighborhood of Togwotee Pass. The 
green-stained basis deposit, also, is like that occurring beneath the great 
voleanic conglomerates at the latter locality, and which, the previous 
season, was found to extend some distance from the summit of the pass 
along the upper course of Wind Liver, where it in turn rested upon 
light buff and drab Tertiary deposits, probably identical with those no- 
ticed above. A few miles to the north of the latter locality the flowed 
lavas connected with the high volcanic plateau that culminates in a low 
dome (the same occupied as Station LI by the Téton division of the sur- 
vey the preceding season), 6 miles south-southeast of Togwotee Pass, 
first appear in situ (No. 17 of the section diagram), and thence round by 
way of that pass the watershed bears a heavy mantle of volcanic rocks. 
The stratigraphical appearance of these deposits in the latter quarter 
were noticed itn the report epon the Téton district, 1877. 
The range of hills separating this basin from Buffalo Fork drainage 
is apparently largely made up of the above-mentioned formations. This 
highland belt was crossed at a point about 10 miles east of Mount 
Leidy, in the vicinity of one of its culminating peaks, Station XXX, 
which has an altitude of 10,338 feet above the sea. ‘The divide is‘ here 
capped by the conglomerate, No. 13, composing several hundred feet 
thickness of the summit strata, and inclined about 8. 12° E., at an angle 
of 10° or less. The conglomerate is here interbedded with hardish, 
gray, dirty-buff weathered sandstone containing fragments of twigs and 
tree trunks. The rock in the high summits weathers in precipitous 
slopes and steep taluses, through which protrude sharp aréte-like but- 
tresses which give to the weather sculpture of these eminences so pecu- 
liar and striking an appearance seen from adistance. East of this point 
the conglomerate is overlaid by the same succession of formations as 
noticed in Gros Ventre River section, 10 miles to the south, with which, 
indeed, these exposures have uninterrupted continuity. At the time of 
our visit the present season (October 11) the country was covered with 
snow; but in the numerous abrupt hillsides the geological formations 
could be readily recognized, and especially so in the case of the great 
interlignitic conglomerate, which rises up into the heights that mark 
the irregular crest of the Mount Leidy highlands. 
The inferior coal-bearing series, composed of softer materials, was not 
15 H 
