Page 724 - calmining1890

674 REPORT OF THE STATE MINERALOGIST.

quantity of free sulphuric acid seems to be large. Much of the wate
tastes as sour as pretty strong lemonade, while some of the incrustation
are most intensely acid, almost burning the tongue that touches them
There is much of the inky deposit of sulphide of iron in many places
and beautiful bunches of sulphur crystals and acicular crystals of vari
ous salts. The rocks here strike northwest and dip, perhaps, 40 to 5(
degrees northeast.
There is stated to have occurred a year or two ago, at the Witches
Cauldron, an explosion, which sounded like the report of heavy cannon {
and blew out a ton or two of rock, some of the pieces of which still lie
there.
After visiting the Geysers themselves, I traveled a mile and a half 01
more down Pluton Canon to the vicinity of the Indian Spring, and
found a belt of this same solfataric action, extending all the way down
along the north side of the canon. It extends at least two miles below
the Geysers, the same decomposition of the rocks showing how exten-
sive the action has been. Nor is the action yet by any means extinct,
so far as I went; but all along there can be seen here and there, at
intervals, a little steam issuing from crevices, etc., and much of the way
the ground is warm just beneath the surface, but I saw at no point any;
large accumulation of sulphur, although it is stated in Vol. I, Geological
Survey Report, page 94, that "quite extensive deposits of sulphur occur
'
farther down the canon, and are known as the Sulphur Banks.' "
About half a mile below the Geyser Hotel, there is in Pluton Canon
a heavy mass of thin-bedded, jaspery shales whose general strike is
northwesterly and dip northeasterly, but which are very much contorted,
being so bent in one place as to suggest a concentric shelly structure.
The road from the Geysers to Calistoga follows up Pluton Canon for
some four or five miles before it climbs the ridge to the south.
The Little Geysers are about a quarter of a mile away from the road
at the point where it leaves the canon, and are on the opposite or north
side of the bed of the canon.
Near them is a stretch of a quarter of a mile, I think, within which
the rocks high up on the hillsides north of the canon have been thor-
oughly decomposed; and the present springs (which are almost entirely
steam blowers like the Large Geysers, only on a smaller scale) are chiefly
spread over a gentle slope near the bottom of a large canon, which here
widens out somewhat, but are considerably lower than the great mass of
decomposed rocks in the adjacent hillsides.
Between the Geysers and the Little Geysers the belt of solfataric action
is only to be traced by occasional spots of whitish, decomposed rocks,
which are visible from the road. But these are enough to mark its con-
tinuance, as nothing of the kind was elsewhere seen in the adjacent
country.
This action has taken place chiefly on the north side of the bed of
Pluton Canon, but has not been entirely confined to it, as there are a
few spots lower down on the south side, which show more or less of the
results of a similar action.
It will be seen that this curious belt of solfataric action is at least six
or seven miles in length. It would be interesting to know whether there
is any trace of gold in the sulphide of iron which is forming here.
The whole now reminds me strongly, in some respects, of the belt of