also there possibly may be others that I never took notice of. And to begin with the first sort of Colours, 'tis well enough known to Chymists, that Tin being Calcin'd by fire alone is wont to afford a White _Calx_, and Lead Calcin'd by fire alone affords that most Common Red-Powder we call _Minium:_ Copper also Calcin'd _per se_, by a long or violent fire, is wont to yield (as far as I have had occasion to take notice of it) a very Dark or Blackish Powder; That Iron likewise may by the Action of Reverberated flames be turn'd into a Colour almost like that of Saffron, 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 very differing from their own, as I not long since noted to you about the variously Colour'd Flowers of Antimony, to which we may add the Whitish Grey-Colour of its _Calx_, and the Yellow or Reddish Colour of the Glass, where into that _Calx_ may be flux'd. And I remember, that I elsewhere told you, that Vitriol Calcin'd with a very gentle heat, and afterwards with higher and higher degrees of it, may be made to pass through several Colours before it descends to a Dark Purplish Colour, whereto a strong fire is wont at length to reduce it. But to insist on the Colours produc'd by the Operation of fire upon several Minerals would take up farr more time than I have now to spare. _EXPERIMENT XLVII._