Figure of their Parts an Aptness to Coalition, as we see in the making
of many Plaisters, Oyntments, &c. And in such Metalline Mixtures as
that made by Melting together two parts of clean Brass with one of
pure Copper, of which some Ingenious Trades-men cast such curious
Patterns (for Gold and Silver Works) as I have sometimes taken great
Pleasure to Look upon. Sometimes the Bodies mingled by the Fire are
Differing enough as to Fixidity and Volatility, and yet are so
combin'd by the first Operation of the Fire, that it self does scarce
afterwards Separate them, but only Pulverize them; whereof an Instance
is afforded us by the Common Preparation of _Mercurius Dulcis_, where
the Saline Particles of the Vitriol, Sea Salt, and sometimes Nitre,
Employ'd to make the Sublimate, do so unite themselves with the
Mercurial Particles made use of, first to Make Sublimate, and then to
Dulcifie it, that the Saline and Metalline Parts arise together in
many successive Sublimations, as if they all made but one Body. And
sometimes too the Fire does not only not Sever the Differing Elements
of a Body, but Combine them so firmly, that Nature her self does very
seldom, if ever, make Unions less Dissoluble. For the Fire meeting
with some Bodies exceedingly and almost equally Fixt, instead of
making a Separation, makes an Union so strict, that it self, alone, is
unable to Dissolve it; As we see, when an Alcalizate Salt and the
Terrestrial Residue of the Ashes are Incorporated with pure Sand, and
by Vitrification made one permanent Body, (I mean the course or
greenish sort of Glass) that mocks the greatest Violence of the Fire,
which though able to Marry the Ingredients of it, yet is not able to
Divorce them. I can shew you some pieces of Glass which I saw flow
down from an Earthen Crucible purposely Expos'd for a good while, with
Silver in it, to a very vehement Fire. And some that deal much in the
Fusion of Metals Informe me, that the melting of a great part of a
Crucible into Glass is no great Wonder in their Furnaces. I remember,
I have Observ'd too in the Melting of great Quantities of Iron out of
the Oar, by the Help of store of Charcoal (for they Affirm that
Sea-Coal will not yield a Flame strong enough) that by the prodigious
Vehemence of the Fire, Excited by vast Bellows (made to play by great
Wheels turn'd about by Water) part of the Materials Expos'd to it was,
instead of being Analyz'd, Colliquated, and turn'd into a Dark, Solid
and very Ponderous Glass, and that in such Quantity, that in some
places I have seen the very High-wayes, neer such Iron-works, mended
with Heaps of such Lumps of Glasse, instead of Stones and Gravel. And
I have also Observ'd, that some kind of Fire-stone it Self, having
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