Earth will after some years yield them Salt-Petre again; For which
reason some of the eminent and skillfullest of them keep it in heaps
as a perpetual Mine of Salt Petre; whence it may appear, that the
Seminal Principle of Nitre latent in the Earth does by degrees
Transforme the neighbouring matter into a Nitrous Body; for though I
deny that some Volatile Nitre may by such Earths be attracted (as they
speak) out of the Air, yet that the innermost parts of such great
heaps that lye so remote from the Air should borrow from it all the
Nitre they abound with, is not probable, for other reasons besides the
remoteness of the Air, though I have not the Leasure to mention them.
And I remember, that a person of Great Credit, and well acquainted
with the wayes of making Vitriol, affirm'd to me, that he had
observ'd, that a kind of mineral which abounds in that Salt, being
kept within Doors and not expos'd (as is usual) to the free Air and
Rains, did of it self in no very long time turn into Vitriol, not only
in the outward or superficial, but even in the internal and most
Central parts.
And I also remember, that I met with a certain kind of Merkasite that
lay together in great Quantities under ground, which did, even in my
chamber, in so few hours begin of it self to turne into Vitriol, that
we need not distrust the newly recited narrative. But to return to
what I was saying of Nitre; as Nature made this Salt-Petre out of the
once almost and inodorous Earth it was bred in, and did not find a
very stinking and corrosive Acid Liquor, and a sharp Alcalyzate Salt
to compound it of, though these be the Bodies into which the Fire
dissolves it; so it were not necessary that Nature should make up all
Metals and other Minerals of Pre-existent Salt, and Sulphur, and
Mercury, though such Bodies might by Fire be obtained from it. Which
one consideration duly weigh'd is very considerable in the present
controversy: And to this agree well the Relations of our two German
Chymists; for besides that it cannot be convincingly prov'd, it is not
so much as likely that so languid and moderate a heat as that within
the Mines, should carry up to so great a heat [Errata: height], though
in the forme of fumes, Salt, Sulphur and Mercury; since we find in our
Distillations, that it requires a considerable Degree of Fire to raise
so much as to the height of one foot not only Salt, but even Mercury
it self, in close Vessels. And if it be objected, that it seems by the
stink that is sometimes observ'd when Lightening falls down here
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