And the First was of a pretty big Ball fastened on to the end of a small
sliver of Iron, which _Compositum_ seemed to be nothing else but a long
thin chip of Iron, one of whose ends was melted into a small round Globul;
the other end remaining unmelted and irregular, and perfectly Iron.

The Second Instance was not less remarkable then the First; for I found,
when a Spark went out, nothing but a very small thin long sliver of Iron or
Steel, unmelted at either end. So that it seems, that some of these Sparks
are the slivers or chips of the Iron _vitrified_, Others are only the
slivers melted into Balls without vitrification, And the third kind are
only small slivers of the Iron, made red-hot with the violence of the
stroke given on the Steel by the Flint.

He that shall diligently examine the _Phænomena_ of this Experiment, will,
I doubt not, find cause to believe, that the reason I have heretofore given
of it, is the true and genuine cause of it, namely, That _the Spark,
appearing so bright in the falling, is nothing else but a small piece of
the Steel or Flint, but most commonly of the Steel, which by the violence
of the stroke is at the same time sever'd and heat red-hot, and that
sometimes to such a degree, as to make it melt together into a small
Globule of Steel; and sometimes also is that heat 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