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: diíTolved ftate at the firft, but quickly
precipitates on account of the heat de-
creafing in the open air. The heat
o f the water was not examined with
the thermometer, till fuch time that
the bafon was filled, when it was
neverthelefs found at a hundred degrees,
according to the Swedifli meafure.
It is in all probability much
greater under the earth ; for its running
through cooler channels, and its
fpouting afterwards into the air to a
great height, muft neceflarily very
much diminifli the heat on account o f
the great difperfion.
This quick depofitioii produces both
the opacity and irregular form o f this
ftone, and prevents the particles from
being fo elofely united as might have
been expeéied from the degree o f the
hardnefs o f each, fuppofing the fol-
vent power had diminiftied more gradually.
Mr. Scheele has difcovered the formation
of the flin t ; and I myfelf have
found out, within thefe two years, a
method of obtaining, with the help
of
fome flnor acid, thirteen precipitated
cryftals of the fize o f fmall peas.
This artificial pebble in all experiments,
both in the wet and dry
method, and even in the focus o f a
burning-glafs, in a piece that I fent
to Mr. Macquer, difcovered exactly to
him the fame qualities as the natural
one.
All thefe circumftances, therefore,
prove, that the pebble is a faline
earth, which is compofed o f fluor
acid, and an original fubftance exift-
ing in the w-atry exhalations. It is
not quite iimple ; but however, I have
not been able to confider it as any
other than an elementary earth : indeed
my judgment is, that it cannot
be eompounded from any other principle.
I do not in this place mean a finer
or coarfer powder, by the denomination
o f earth, as is generally underftood
under this appellation ; but I
take the word in a chemical fenfe, to
exprefs a fixed principle, which is
obtained in analyilng any fubftance,
and that cannot be diflblved in boiling
f t