And that the particles of _Metalline_ colours are transparent, may be
argued yet further from this, that the Crystals, or _Vitriols_ of all
Metals, are transparent, which since they consist of _metalline_ as well as
_saline_ particles, those _metalline_ ones must be transparent, which is
yet further confirm'd from this, that they have for the most part,
_appropriate_ colours; so the _vitriol_ of Gold is Yellow; of Copper, Blue,
and sometimes Green; of Iron, green; of Tinn and Lead, a pale White; of
Silver, a pale Blue, _&._

And next, the _Solution_ of all Metals into _menstruums_ are much the same
with the _Vitriols_, or Crystals. It seems therefore very probable, that
those colours which are made by the _precipitation_ of those particles out
of the _menstruums_ by transparent _precipitating_ liquors should be
transparent also. Thus Gold _precipitates_ with _oyl of Tartar_, or _spirit
of Urine_ into a brown Yellow, Copper with spirit of _Urine_ into a Mucous
blue, which retains its transparency. A solution of sublimate (as the same
Illustrious Authour I lately mention'd shews in his 40. Experiment)
_precipitates_ with oyl of _Tartar_ _per deliquium_, into an Orange
colour'd _precipitate_; nor is it less probable, that the _calcination_ of
those _Vitriols_ by the fire, should have their particles transparent: Thus
_Saccarum Saturni_, or the _Vitriol of Lead_ by _calcination_ becomes a
deep Orange-colour'd _minium_, which is a kind of _precipitation_ by some
Salt which proceeds from the fire; common _Vitriol_ _calcin'd_, yields a
deep Brown Red, etc.

A third Argument, that the particles of Metals are transparent, is, that
being _calcin'd_, and melted with Glass, they tinge the Glass with
transparent colours. Thus the _Calx_ of Silver tinges the Glass on which it
is anneal'd with a lovely Yellow, or Gold colour, &c.