Fifthly, in its _dissolubleness_; for putting some drops of distill’d _Vinegar_ upon the Stone, I found it presently to yield very many Bubbles, just like those which may be observ’d in spirit of _Vinegar_ when it corrodes _corals_, though perhaps many of those small Bubbles might proceed from some small parcels of Air which were driven out of the pores of this _petrify’d_ substance by the insinuating liquid _menstruum_. Sixthly, in its _rigidness_, and _friability_, being not at all flexible but brittle like a Flint, insomuch that I could with one knock of a Hammer break off a piece of it, and with a few more, reduce that into a pretty fine powder. Seventhly, it seem’d also very differing from Wood to the _touch_, _feeling_ more cold then Wood usually does, and much like other close stones and Minerals. The Reasons of all which _Phænomena_ seem to be, That _petrify’d_ Wood having lain in some place where it was well soak’d with _petrifying_ water (that is, such a water as is well _impregnated_ with stony and earthy particles) did by degrees separate, either by straining and _filtration_, or perhaps, by _precipitation_, _cohesion_ or _coagulation_, abundance of stony particles from the permeating water, which stony particles, being by means of the fluid _vehicle_ convey’d, not onely into the _Microscopical_ pores, and so perfectly stopping them up, but also into the pores or _interstitia_, which may, perhaps, be even in the texture or _Schematisme_ of that part of the Wood, which, through the _Microscope_, appears most solid, do thereby so augment the weight of the Wood, as to make it above three times heavier then water, and perhaps, six times as heavie as it was when Wood. Next, they thereby so lock up and fetter the parts of the Wood, that the fire cannot easily make them flie away, but the action of the fire upon them is onely able to _Char_ those parts, as it were, like a piece of Wood, if it be clos’d very fast up in Clay, and kept a good while red-hot in the fire, will by the heat of the fire be charr’d and not consum’d, which may, perhaps, also be somewhat of the cause, why the _petrify’d_ substance appear’d of 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.