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LXXII. On a saline Substance from Mount Vesuvius. By 
James Smiruson, Esq. F.R.S,* 
I, has very long appeared to me, that when the earth is 
considered with attention, innumerable circumstances are 
perceived, which cannot but lead to the belief, that it has 
once been in a state of general conflagration. The existence 
in the skies of planetary bodies, which seem to be actually 
burning, and the appearances of original fire discernible on 
our globe, I have conceived to be mutually corroborative 
of each other; and ‘at the time when no answers could he 
given to the most essential objections to the hypothesis, the 
‘mass of facts in favour of it fully justified, I thought, the, 
inference that our habitation is an extinct comet or sun, 
The mighty difficulties which formerly assailed this opi- 
nion, great modern discoveries bave dissipated. Acquainted 
now, that the bases of alkalies and earths are metals, emi- 
nently oxidable, we are no longer embarrassed either for 
the pabulum of the inflammation, or to account for the 
products of it. 
In the primitive strata, we behold the result of the com- 
‘bustion. In them we see the oxide collected on the surface 
of the calcining mass, first melted hy the heat, then by its 
ancrease arresting further combination, and extinguishing 
the fires which had generated it, and in fine become solid 
and crystallized over te metallic ball. 
Every thing tells that a large body of combusvble matter 
still remains inclosed within this stony envelope, and of 
which volcanic eruptions are partial and small accensions, 
Under this point of view, an high interest attaches itself 
to volcanoes, and their ejections. They cease to be local 
phenomena; they become principal elements in the history 
of our globe ; they connect its present with its former con- 
dition ; and we have good grounds for supposing, that in 
their flames are to be read its future destinies. 
In support of the igneous origin, here attributed to the 
primitive strata, I will observe, that not only no crystal 
ambedded in them, such as quartz, garnet, tourmaline, &c. 
has ever been seer inclosing drops of water; but that none 
of the materials of these strata contain water in any state. 
a. The present saline substance was sent to me from 
Naples to Florence, where I was, in May 1794, with a re- 
guest to ascertain its nature, The general examination 
which I then made of it, showed it to be principally what 
* From the Philosophical Transactions for 1818, part ii. 
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