we purposely made.

4 We took a good quantity of clean Lead, and melted it with a strong Fire,
and then immediately pouring it out into a clean Vessel of a convenient
shape and matter, (we us'd one of Iron, that the great and sudden Heat
might not injure it) and then carefully and nimbly taking off the Scum that
floated on the top, we perceiv'd, as we expected, the smooth and glossie
Surface of the melted matter, to be adorn'd with a very glorious Colour,
which being as Transitory as Delightfull, did almost immediately give place
to another vivid Colour, and that was as quickly succeeded by a third, and
this as it were chas'd away by a fourth, and so these wonderfully vivid
Colours successively appear'd and vanish'd, (yet the same now and then
appearing the second time) till the Metall ceasing to be hot enough to
afford any longer this pleasing Spectacle, the Colours that chanc'd to
adorn the Surface, when the Lead thus began to cool, remain'd upon it; but
were so Superficial, that how little soever we scrap'd off the Surface of
the Lead, we did in such places scrape off all the Colour, and discover
only that which is natural to the Metall it self, which receiving its
adventitious Colours, only when the heat was very Intense, and in that part
which was expos'd to the comparatively very cold Air, (which by other
Experiments seems to abound with subtil Saline parts, perhaps not uncapable
of working upon Lead so dispos'd:) These things I say, together with my
observing that whatever parts of the so strongly melted Lead were expos'd a
while to the Air, turn'd into a kind of Scum or Litharge, how bright and
clean soever they appear'd before, suggested to me some Thoughts or
Ravings, which I have not now time to acquaint You with. One that did not
know me, _Pyrophilus_, would perchance think I endeavour'd to impose upon
You by relating this Experiment, which I have several times try'd, but the
Reason why the _Phaenomena_ mention'd have not been taken notice of, may be,
that unless Lead be brought to a much higher degree of Fusion or Fluidity
than is usual, or than is indeed requisite to make it melt, the _Phaenomena_
I mention'd will scarce at all disclose themselves; And we have also
observ'd that this successive appearing and vanishing of vivid Colours, was
wont to be impair'd or determin'd whilst the Metal expos'd to the Air
remain'd yet hotter than one would readily suspect. And one thing I must
further Note, of which I lea