And therefore, what ever is by some, who have written of it, and particularly by _Francisco Stelluto_, wrote a Treatise in _Italian_ of that Subject, which was Printed at _Rome_, 1637, affirm’d that it is a certain kind of Clay or Earth, which in tract of time is turn’d into Wood; I rather suspect the quite contrary, that it was at first certain great Trees of Fir or Pine, which by some Earthquake, or other casualty, came to be buried under the Earth, and was there, after a long time’s residence (according to the several natures of the encompassing adjacent parts) either rotted and turn’d into a kind of Clay, or _petrify’d_ and turn’d into a kind of Stone, or else had its pores fill’d with certain Mineral juices, which being stay’d in them, and in tract of time coagulated, appear’d, upon cleaving out, like small Metalline Wires, or else from some flames or scorching forms that are the occasion oftentimes, and usually accompany Earthquakes, might be blasted and turn’d into Coal, or else from certain _subterraneous_ fires which are affirm’d by that Authour to abound much about those parts (namely, in a Province of _Italy_, call’d _Umbria_, now the _Dutchie_ of _Spoletto_, in the Territory of _Todi_, anciently call’d _Tudor_; and between the two Villages of _Collesecco_ and _Rosaro_ not far distant from the high-way leading to _Rome_, where it is found in greater quantity then elsewhere) are by reason of their being encompassed with Earth, and so kept close from the dissolving Air, charr’d and converted into Coal. It would be too long a work to describe the several kinds of pores which I met withall, and by this means discovered in several other Vegetable bodies; nor is it my present design to expatiate upon Instances of the same kind, but rather to give a Specimen of as many kinds as I have had opportunity as yet of observing, reserving the prosecution and enlarging on particulars till a more fit opportunity; and in prosecution of this design, I shall here add: * * * * * Observ. XVII. _Of _Petrify’d wood_, and other _Petrify’d bodies_._ 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_.