Predominancy of this or that Principle in them, but upon that of their
Texture, and especially the Disposition of their superficial parts,
whereby the Light rebounding thence to the Eye is so modifi'd, as by
differing Impressions variously to affect the Organs of Sight. I might
here take notice of the pleasing variety of Colours exhibited by the
Triangular glass, (as 'tis wont to be call'd) and demand, what
addition or decrement of either Salt, Sulphur, or Mercury, befalls the
Body of the Glass by being Prismatically figur'd; and yet 'tis known,
that without that shape it would not affor'd those colours as it does.
But because it may be objected, that these are not real, but apparent
Colours; that I may not lose time in examing the Distinction, I will
alledge against the Chymists, a couple of examples of Real and
Permanent Colours Drawn from Metalline Bodies, and represent, that
without the addition of any extraneous body, Quicksilver may by the
Fire alone, and that in glass Vessels, be depriv'd of its silver-like
Colour, and be turn'd into a Red Body; and from this Red Body without
Addition likewise may be obtain'd a Mercury Bright and Specular as it
was before; So that I have here a lasting Colour Generated and
Destroy'd (as I have seen) at pleasure, without adding or taking away
either Mercury, Salt, or Sulphur; and if you take a clean and slender
piece of harden'd steel, and apply to it the flame of a candle at some
little distance short of the point, You shall not have held the Steel
long in the flame, but You shall perceive divers Colours, as Yellow,
Red and Blew, to appear upon the Surface of the metal, and as it were
run along in chase of one another towards the point; So that the same
body, and that in one and the same part, may not only have a new
colour produc'd in it, but exhibite successively divers Colours within
a minute of an hour, or thereabouts, and any of these Colours may by
Removing the Steel from the Fire, become Permanent, and last many
years. And this Production and Variety of Colours cannot reasonably be
suppos'd to proceed from the Accession of any of the three Principles,
to which of them soever Chymists will be pleas'd to ascribe Colours;
especially considering, that if you but suddenly Refrigerate that
Iron, First made Red hot, it will be harden'd and Colourless again;
and not only by the Flame of a Candle, but by any other equivalent
heat Conveniently appli'd, the like Colours will again be made to
appear and succeed one another, as at the First. But I must not any
further prosecute an Occasional Discourse, though that were not so
Difficult for me to do, as I fear it would be for the Chymists to give
a better Account of the other Qualities, by their Principles, then
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