Of this sort of substance, I observ’d several pieces of very differing
kinds, both for their outward shape, colour, grain, _texture_, hardness,
&c. some being brown and reddish; others gray, like a Hone; others black,
and Flint-like: some soft, like a Slate or Whetstone, others as hard as a
Flint, and as brittle. That which I more particular examin’d, was a piece
about the bigness of a mans hand, which seem’d to have been a part of some
large tree, that by rottenness had been broken off from it before it began
to be _petrify’d_.
And indeed, all that I have yet seen, seem to have been rotten Wood before
the petrifaction was begun; and not long since, examining and viewing a
huge great _Oak_, that seem’d with meer age to be rotten as it stood, I was
very much confirm’d in this opinion; for I found, that the grain, colour,
and shape of the Wood, was exactly like this _petrify’d_ substance; and
with a _Microscope_, I found, that all those _Microscopical_ pores, which
in sappy or firm and sound Wood are fill’d with the natural or innate
juices of those Vegetables, in this they were all empty, like those of
_Vegetables charr’d_; but with this difference, that they seem’d much
larger then I have seen any in _Charcoals_; nay, even then those of Coals
made of great blocks of Timber, which are commonly call’d _Old-coals_.
The reason of which difference may probably be, that the charring of
Vegetables, being an operation quickly perform’d, and whilest the Wood is
sappy, the more solid parts may more easily shrink together, and contract
the pores or _interstitia_ between them, then in the rotten Wood, where
that natural juice seems onely to be wash’d away by _adventitious_ or
unnatural moisture; and so though the natural juice be wasted from between
the firm parts, yet those parts are kept asunder by the _adventitious_
moystures, and so by degrees settled in those postures.
And this I likewise found in the _petrify’d_ Wood, that the pores were
somewhat bigger then those of _Charcoal_, each pore being neer upon half as
bigg again, but they did not bear that disproportion which is exprest in
the tenth _Scheme_, between the small specks or pores in the first Figure
(which representeth the pores of Coal or Wood charr’d) and the black spots
of the second Figure (which represent the like _Microscopical pores_ in the
_petrify’d_ Wood) for these last were drawn by a _Microscope_ that
magnify’d the object above six times more in Diameter then the _Microscope_
by which those pores of Coal were observ’d.
Now, though they were a little bigger, yet did they keep the exact figure
and order of the pores of Coals and of rotten Wood, which last also were
much of the same cize.
The other Observations on this _petrify’d_ substance, that a while since,
by the appointment of the _Royal Society_, I made, and presented to them an
account of, were these that follow, which had the honour done them by the
most accomplish’d Mr. _Evelin_, my highly honoured friend, to be inserted
and published among those excellent Observations wherewith his _Sylva_ is
replenish’d, and would therefore have been here omitted, had not the Figure
of them, as they appear’d through the _Microscope_ been before that
engraven.