f a dark brown colour after it had been burnt.

By this _intrusion_ of the _petrifying_ particles, this substance also
becomes hard and _friable_; for the smaller pores of the Wood being
perfectly wedg'd, and stuft up with those stony particles, the small parts
of the Wood have no places or pores into which they may slide upon bending,
and consequently little or no flexion or yielding at all can be caus'd in
such a substance.

The remaining particles likewise of the Wood among the stony particles, may
keep them from cracking and flying when put into the fire, as they are very
apt to do in a Flint.

Nor is Wood the onely substance that may by this kind of _transmutation_ be
chang'd into stone; for I my self have seen and examin'd very many kinds of
substances, and among very credible Authours, we may meet with Histories of
such _Metamorphoses_ wrought almost on all kind of substances, both
_Vegetable_ and _Animal_, which Histories, it is not my business at
present, either to relate, or _epitomise_, but only to set down some
Observation I lately made on several kind of _petrify'd_ Shels, found about
_Keinsham_, which lies within four or five miles of _Bristol_, which are
commonly call'd _Serpentine-stones._

Examining several of these very curiously figur'd bodies (which are
commonly thought to be Stones form'd by some extraordinary _Plastick
virtue_ _latent_ in the Earth itself) I took notice of these particulars:

First, that these figured bodies, or stones, were of very differing
substances, as to hardness: some of Clay, some Marle, some soft Stone,
almost of the hardness of those soft stones which Masons call Fire-stone,
others as hard as Portland stone, others as hard as Marble, and some as
hard as a Flint or Crystal.

Next, they were of very differing substances as to transparency and colour;
some white, some almost black, some brown, some Metalline, or like
Marchasites; some transparent like white Marble, others like flaw'd
Crystal, some gray, some of divers colours; some radiated like those long
_petrify'd drops_, which are commonly found at the _Peak_, and in other
_subterraneous caverns_, which have a kind of pith in the middle.

Thirdly, that they were very different as to the manner of their outward
figuration; for some of them seem'd to have been the substance that had
fill'd the Shell of some kind of Shel-fish; others, to have been the
substance that had contain'd or enwrapp'd one of those Shels, on bo