Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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They Are Semi-Diaphanous Octahedrons, Very Brilliant On The
Surface, And Of A Conchoidal Fracture.
These masses, which will one
day perhaps be objects of commerce, are constantly bedewed with
sulphurous acid.
I had the imprudence to wrap up a few, in order to
preserve them, but I soon discovered that the acid had consumed not
only the paper which contained them, but a part also of my
mineralogical journal. The heat of the vapours, which issue from
the crevices of the caldera, is not sufficiently great to combine
the sulphur while in a state of minute division, with the oxygen of
the atmospheric air; and after the experiment I have just cited on
the temperature of the soil, we may presume that the sulphurous
acid is formed at a certain depth,* in cavities to which the
external air has free access. (* An observer, in general very
accurate, M. Breislack, asserts that the muriatic acid always
predominates in the vapours of Vesuvius. This assertion is contrary
to what M. Gay-Lussac and myself observed, before the great
eruption of 1805, and while the lava was issuing from the crater.
The smell of the sulphurous acid, so easy to distinguish, was
perceptible at a great distance; and when the volcano threw out
scoriae, the smell was mingled with that of petroleum.)
The vapours of heated water, which act on the fragments of lava
scattered about on the caldera, reduce certain parts of it to a
state of paste. On examining, after I had reached America, those
earthy and friable masses, I found crystals of sulphate of alumine.
MM.
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