may be easily deduc'd from the Preparation of that Powder, which by reason
of its Colour and of the Metall 'tis made of is by Chymists call'd, _Crocus
Martis per se_. And that _Mercury_ made by the stress of Fire, may be
turn'd into a Red Powder, which Chymists call Precipitate _per se_, I
elsewhere more particularly declare.

_Annotation I._

It is not unworthy the Admonishing you, (_Pyrophilus_,) and it agrees very
well with our Conjectures about the dependence of the change of a Body's
Colour upon that of its Texture, that the same Metall may by the successive
operation of the fire receive divers Adventitious Colours, as is evident in
Lead, which before it come to so deep a Colour as that of _Minium_, may
pass through divers others.

_Annotation II_.

Not only the _Calces_, but the Glasses of Metalls, Vitrify'd _per se_, may
be of Colours differing from the Natural or Obvious Colour of the Metall;
as I have observ'd in the Glass of Lead, made by long exposing Crude Lead
to a violent fire, and what I have observ'd about the Glass or Slagg of
Copper, (of which I can show you some of an odd kind of Texture,) may be
elsewhere more conveniently related. I have likewise seen a piece of very
Dark Glass, which an Ingenious Artificer that show'd it me profess'd
himself to have made of Silver alone by an extreme _Violence_ (which seems
to be no more than is needfull) of the fire.

_Annotation III_.

Minerals also by the Action of the Fire may be brought to afford Colours