i ft
state, the alkali is set free, being probably assisted
in this change by the carbonic acid of the atmosphere,
and being dissolved in, and removed by,
water, is found in considerable abundance.
The silica which is thus deposited is not merely
insoluble in water, but in sulphuric, nitric, or muriatic
acid also, and quite resembles the purer parts of
that which you sent me as deposited at the spring.
The alkali is in such quantity, that when washed
fiom the silica by distilled water, and diluted, until
of the bulk of the water before evaporation, it readily
affects turmeric paper. The original ivater does
not immediately and sensibly affect the test paper,
but if it be heated, in the air at least, it gradually
affects the paper ivhen left in it. All the effects
show that the silica for the timeTieutralizes in part
the alkali, and that the latter shows its jiowers as
the former is by the evaporation gradually separated
from it.
“ The deposits are all essentially siliceous : most
of them have the silica in combination with water
as a hydrate, and it is probable that a little alkali is
contained in them. The red portions are produced
by oxide of iron, derived, I believe, not from oxide
of iron contained originally in the waters of the
Geyser, but from the action of the alkali precipitating
some chalybeated portions of water which it
meets with in its course. I think you said that the
red deposit does not occur at the spring, but at the
place where the waters run into the river.
“ The waters contain, besides silica, &c., sulphate
and muriate, probably of the alkali soda, for there
is no sensible portion of lime present; but these, or
at least the muriate or the chlorine is probably in
a peculiar state of combination, for when nitrate of
silver is added to the original water, i. e. before the
silica is separated from it, it causes but a very
slight precipitate ; and yet the addition of a little
nitric or sulphuric, or even acetic acid, produces an
abundant precipitate of chloride of silver. This is
an effect Avhich we should not expect, and shows
the interference of something for a time, which interference
is removed by the presence of the acids.
The quantity of water was so small, that 1 was not
able to satisfy myself of the exact nature of this
action.
“ The specific gravity of the water is 1000-8.
“ 1 presume th a t the deposition which takes
place from the waters at the spring is quite of the
same nature as that which occurs on the evaporation
of the portion you brought aivay; the water
coming from the earth in its fresh and hot state
fully saturated with silica, and holding more of it
than it can retain when it cools and is exposed to
the air. I should not think it would be an impossible
thing by art to imitate the whole effect.
“ With regard to the surturbrand, 1 have nothing
to say about it which is not well known, and 1 believe
published. The specimens of the deposits 1