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PBOCEEDINGS OF THE GEOLOGICAL SOCIETY. .Apr. 13,
unconformable to them. Mount Davidson and a part of the second
range or summit of the Sierra are sketched in the background, so
as to show as nearly as possible their position relatively to the
section on the plain. The porphyritic conglomerate probably ex-
tends through the Mount Davidson and Washoe Ranges, but it was
not seen there. The second outcrop to the right of Carson River
would seem, from the section, to sustain the relation of a dyke to
the tilted beds containing the brown coal, but it is merely intended
to indicate their nonconformity. In describing the granite of the
western slope of the Sierra Nevada, near the plains of the Great
Basin, it should have been observed, in addition to the description
of the outcrops of metamorphic rocks near Genoa, that in the pass
to Lake Bigler, a few miles south of Carson, the lower exposures
and ridges of the granite present some remarkable evidences of
former stratification, as seen in the accompanying outline-sketch
(fig. 2). These vertical masses of rock rise from 50 to 150 feet
above the crests of the ridges. This structure is brought out more
clearly by weathering.
III. Hot Springs. — Thermal springs of considerable volume are
numerous in various parts of the Territory

but the most extensive
and interesting are, probably, those known as the Steamboat Springs,
about ten miles north-west of Virginia City, and bordering on
"Washoe Creek.
The position of these springs is marked by columns of steam
rising in a line above a white mound, about a quarter of a mile
long and forty or fifty feet higher than the bed of the creek. Two
or three fissures extend through the centre of the whole length of
the mound, and it is from these, at different points, that jets of
steam ascend. The section (fig. 3) will show the form of the mound
and the relation of the springs to the adjoining rocks.
Fig. 3. — Section across the Steamboat Springs.
Washoe Creek.
C. Granite, G. Gravel. L. Limestone. P. Porphyry.
S. Deposit from the springs.
The direction of the fissures is 15° to 20° N. of W., apparently
following the line of division between compact grey granite, like
that of the Sierra Nevada, and a bed of porphyry

though this could
not be ascertained with any certainty, owing to the thick deposit
produced by the springs and the alluvium beyond. They vary from
three to twelve inches in width, and are vertical

but they are so
irregular and rugged at the sides that they cannot be probed