f the Best wayes that is Practis'd for the
Refining of Gold,) yet it requires both Watchfulness and Skill, to give it
such a Degree of Fire as will serve to Restore it to its Lustre, without
giving it such a One, as may bring it to Fusion, to which the Minuteness of
the _Corpuseles_ it consists of makes the Powder very apt. And this brings
into my Mind, that having taken a Flat and Bright piece of Gold, that was
Refin'd by a Curious and Skilfull Person on purpose to Trye to what height
of Purity Gold could be brought by Art, I found that this very piece, as
Glorious as it look'd, being rubb'd a little upon a piece of fine clean
Linnen, did sully it with a kind of Black; and the like I have observ'd in
Refin'd Silver, which I therefore mention, because I formerly suspected
that the Impurity of the Metall might have been the only Cause of what I
have divers times obferv'd in wearing Silver-hilted Swords, Namely, that
where they rubb'd upon my Clothes, if they were of a Light-Colour'd Cloath,
the Affriction would quickly Black them; and Congruously hereunto I have
found Pens Blackt almost all over, when I had a while carri'd them about me
in a Silver Ink-case. To which I shall only add, that whereas in these
several Instances of Denigration, the Metalls are worn off, or otherwise
Reduc'd into very Minute Parts, that Circumstance may prove not Unworthy
your Notice.

_EXPERIMENT X._

That a Solution of Silver does Dye Hair of a Black Colour, is a Known
Experiment, which some persons more Curious than Dextrous, have so
Unluckily made upon themselves as to make their Friends very Merry. And I
remember that the other day, I made my self some Sport by an Improvement of
this Observation, for having dissolv'd some Pure Silver in _Aqua Fortis_,
and Evaporated the _Menstruum ad siccitatem_, as they speak, I caus'd a
Quantity of fair Water to be pour'd upon the _Calx_ two or three several
times, and to be at each Evaporated, till the _Calx_ was very Drye, and all
the Greenish Blewness that is wont to appear in Common Crystals of Silver,
was quite carry'd away. Then I made those I meant to Deceive, Moisten some
part of their Skin with their own Spittle, and slightly Rub the moistned
parts with a little of this Prepar'd Silver, Whereupon they Admir'd to see,
that a Snow-white Body laid upon the White Skin should presently produce a
deep Blackness, as if the stains had been made with Ink, especially
considering that this Blackness could