been employ'd in Furnaces wherein it was expos'd to very strong and
lasting Fires, has had all its Fixt Parts so Wrought on by the Fire,
as to be Perfectly Vitrifi'd, which I have try'd by Forcing from it
Pretty large Pieces of Perfect and Transparent Glass. And lest You
might think, _Eleutherius_, that the Question'd Definition of Heat may
be Demonstrated, by the Definition which is wont to be given and
Acquiesc'd in, of its contrary Quality, Cold, whose property is taught
to be _tam Homogenea, quam Heterogenea congregare_; Give me leave to
represent to You, that neither is this Definition unquestionable; for
not to Mention the Exceptions, which a _Logician_, as such, may Take
at it, I Consider that the Union of Heterogeneous Bodies which is
Suppos'd to be the Genuine Production of Cold, is not Perform'd by
every Degree of Cold. For we see for Instance that in the Urine of
Healthy Men, when the Liquor has been Suffer'd a while to stand, the
Cold makes a Separation of the Thinner Part from the Grosser, which
Subsides to the Bottom, and Growes Opacous there; whereas if the
Urinal be Warme, these Parts readily Mingle again, and the whole
Liquor becomes Transparent as before. And when, by Glaciation, Wood,
Straw, Dust, Water, &c. are Suppos'd to be United into one Lump of
Ice, the Cold does not Cause any Real Union or Adunation, (if I may so
Speak) of these Bodies, but only Hardening the Aqueous Parts of the
Liquor into Ice, the other Bodies being Accidentally Present in that
Liquor are frozen up in it, but not Really United. And accordingly if
we Expose a Heap of Mony Consisting of Gold, Silver and Copper Coynes,
or any other Bodies of Differing Natures, which are Destitute of
Aqueous Moisture, Capable of Congelation, to never so intense a Cold,
we find not that these Differing Bodies are at all thereby so much as
Compacted, much less United together; and even in Liquors Themselves
we find _Phaenomena_ which Induce us to Question the Definition which
we are examining. If _Paracelsus_ his Authority were to be look't upon
as a Sufficient Proof in matters of this Nature, I might here insist
on that Process of his, whereby he Teaches that the Essence of Wine
may be Sever'd from the Phlegme and Ignoble Part by the Assistance of
Congelation: and because much Weight has been laid upon this Process,
not only by _Paracelsians_, but other Writers, some of whom seem not
to have perus'd it themselves, I shall give You the entire Passage in
the Authors own Words, as I lately found them in the sixth Book of his
_Archidoxis_, an Extract whereof I have yet about me; and it sounds
thus. _De Vino sciendum est, faecem phlegmaque ejus esse Mineram, &
Vini substantiam esse corpus in quo conservatur Essentia, prout auri
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