and of the ambient Bodies, whether Air, Water, &c. that not
only in humane Bodies we see that the immoderate or
unseasonable coldness of the Air (especially when it finds
such Bodies overheated) do's very frequently discompose the
_Oeconomie_ of them, and occasion variety of Diseases; but
in the solid and durable Body of Iron it self, in which one
would not expect that suddain Cold should produce any
notable change, it may have so great an operation, that if
you take a Wire, or other slender piece of steel, and having
brought it in the fire to a white heat, You suffer it
afterwards to cool leasurely in the Air, it will when it is
cold be much of the same hardnesse it was of before: Whereas
if as soon as You remove it from the fire, you plunge it
into cold water, it will upon the sudden Refrigeration
acquire a very much greater hardness then it had before;
Nay, and will become manifestly brittle. And that you may
not impute this to any peculiar Quality in the Water, or
other Liquor, or Unctuous matter, wherein such heated steel
is wont to be quenched that it may be temper'd; I know a
very skillful Tradesman, that divers times hardens steel by
suddenly cooling it in a Body that is neither a liquor, nor
so much as moist. A tryal of that Nature I remember I have
seen made. And however by the operation that Water has upon
steel quenched in it, whether upon the Account of its
coldness and moisture, or upon that of any other of its
qualities, it appears, that water is not alwaies so
inefficacious and contemptible a Body, as our Chymists would
have it passe for. And what I have said of the Efficacy of
Cold and Heat, might perhaps be easily enough carried
further by other considerations and experiments; were it not
that having been mention'd only upon the Bye, I must not
insist on it, but proceed to another Subject.
_ERRATA._
Pag. 5. line. 6. read _so qualify'd_, 15. 19. _Ratiocinations_, 25.
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