of _adust_ or _torrifi'd
Sulphur_. But I hope that what we have deliver'd above to countenance the
Opinion we have propos'd about the Cause of Blackness, will so easily
supply you with several Particulars that may be made use of against this
Opinion, that I shall now represent to You but two things concerning it.

And First it seems that the favourers of the Chymicall Theories might have
pitcht upon some more proper term, to express the Efficient of Blackness
than _Sulphur adust_; for we know that _common Sulphur_, not only when
Melted, but even when Sublim'd, does not grow Black by suffering the Action
of the fire, but continues and ascends Yellow, and rather more than less
White, than it was before its being expos'd to the fire. And if it be set
on fire, as when we make that acid Liquor, that Chymists call _Oleum
Sulphuris per campanam_, it affords very little Soot, and indeed the flame
yeelds so little, that it will scarce in any degree Black a sheet of White
Paper, held a pretty while over the flame and smoak of it, which is
observed rather to Whiten than Infect linnen, and which does plainly make
Red Roses grow very Pale, but not at all Black, as far as the Smoak is
permitted to reach the leaves. And I can shew you of a sort of fixt Sulphur
made by an Industrious Laborant of your acquaintance, who assur'd me that
he was wont to keep it for divers weeks together night and day in a naked
and Violent fire, almost like that of the Glass-house, and when, to
satisfie my Curiosity, I made him take out a lump of it, though it were
glowing hot (and yet not melted,) it did not, when I had suffered it to
cool, appear Black, the true Colour of it being a true Red. I know it may
be said, that _Chymists_ in the Opinion above recited mean the _Principle
of Sulphur_, and not _common Sulphur_ which receives its name, not from its
being _all_ perfectly of a Sulphureous Nature, but for that _plenty_ and
_Predominancy_ of the Sulphureous Principle in it. But allowing this, 'tis
easie to reply, that still according to this very Reason, torrifi'd Sulphur
should afford more Blackness, than most other concretes, wherein that
Principle is confess'd to be far less copious. Also when I have expos'd
Camphire to the fire in Close Vessels, as Inflamable, and consequenly
(according to the Chymists) as Sulphureous a Body as it is, I could not by
such a degree of Heat, as brought it to Fusion, and made it Boyl in the
glass, impress any thing of B