at so very intense, as
further to melt it and vitrifie it; but many times the heat is so gentle,
as to be able to make the sliver only red hot, which notwithstanding
falling upon the tinder_ (that is only a very curious small Coal made of
the small threads of Linnen burnt to coals and char'd) _it easily sets it
on fire_. Nor will any part of this _Hypothesis_ seem strange to him that
considers, First, that either hammering, or filing or otherwise violently
rubbing of Steel, will presently make it so hot as to be able to burn ones
fingers. Next, that the whole force of the stroke is exerted upon that
small part where the Flint and Steel first touch: For the Bodies being each
of them so very hard, the puls cannot be far communicated, that is, the
parts of each can yield but very little, and therefore the violence of the
concussion will be _exerted_ on that piece of Steel which is cut off by the
Flint. Thirdly, that the filings or small parts of Steel are very apt, as
it were, to take fire, and are presently red hot, that is, there seems to
be a very _combustible sulphureous_ Body in Iron or Steel, which the Air
very readily preys upon, as soon as the body is a little violently heated.

And this is obvious in the filings of Steel or Iron cast through the flame
of a Candle; for even by that sudden _transitus_ of the small chips of
Iron, they are heat red hot, and that _combustible sulphureous_ Body is
presently prey'd upon and devoured by the _aereal_ incompassing
_Menstruum_, whose office in this Particular I have shewn in the
Explication of Charcole.

And in prosecution of this Experiment, having taken the filings of Iron and
Steel, and with the point of a Knife cast them through the flame of a
Candle, I observed where some conspicuous shining Particles fell, and
looking on them with my _Microscope_, I found them to be nothing else but
such round Globules, as I formerly found the Sparks struck from the Steel
by a stroke to be, only a little bigger; and shaking together all the
filings that had fallen upon the sheet of Paper underneath and observing
them with the _Microscope_, I found a great number of small Globules, such
as the former, though there were also many of the parts that had remained
untoucht and rough filings or chips of Iron. So that, it seems, Iron does
contain a very _combustible sulphureous_ Body, which is, in all likelihood,
one of the causes of this _Phaenomenon_, and which may be perhaps very much
conce