near the beginning of the 44th Experiment, of the seeming Blackness of
those Bodies that are overcharg'd with the Corpuscles of such Colours, as
Red, or Blew, or Green, &c. And as by several Metals and other Minerals we
can give various Colours to Glass, so on the other side, by the differing
Colours that Mineral Oars, or other Mineral Powders being melted with Glass
disclose in it, a good Conjecture may be oftentimes made of the Metall or
known Mineral, that the Oar propos'd, either holds, or is most of kin to.
And this easie way of examining Oars, may be in some cases of good use, and
is not ill deliver'd by _Glauber_, to whom I shall at present refer you,
for a more particular account of it: unless your Curiosity command also
what I have observ'd about these matters; only I must here advertise you,
that great circumspection is requisite to keep this way from proving
fallacious, upon the account of the variations of Colour that may be
produc'd by the differing proportions that may be us'd betwixt the Oar and
the Glass, by the Richness or Poorness of the Oar it self, by the Degree of
Fire, and (especially) by the Length of Time, during which the matter is
kept in fusion; as you will easily gather from what you will quickly meet
with in the following Annotation upon this present 48th Experiment.

_Annotation IV._

There is another way and differing enough from those already mention'd, by
which Metalls may be brought to exhibit adventitious Colours: For by This,
the Metall do's not so much impart a Colour to another Body, as receive a
Colour from it, or rather both Bodies do by the new Texture resulting from
their mistion produce a new Colour. I will not insist to this purpose upon
the Examples afforded us by yellow Orpiment, and common Sea Salt, from
which, sublim'd together, Chymists unanimously affirm their White or
Crystalline Arsenick to be made: But 'tis not unworthy our noting, That
though Yellow Orpiment be acknowledg'd to be the Copiousest by far of the