This maybe done also in any close Vessel of Glass, as a Retort, or the like, and the several fluid substances that come over may be receiv’d in a fit Recipient, which will yet further countenance this Hypothesis: And their manner of charring Wood in great quantity comes much to the same thing, namely, an application of a great heat to the body, and preserving it from the free access of the devouring air; this may be easily learn’d from the History of Charring of Coal, most excellently describ’d and publish’d by that most accomplish’d Gentleman, Mr. John Evelin, in the 100, 101, 103, pages of his Sylva, to which I shall therefore refer the curious Reader that desires a full information of it.
Next, we may learn what part of the Wood it is that is the combustible matter, for since we shall find that none, or very little of those fluid substances that are driven over into the Receiver are combustible, and that most of that which is left behind is so, it follows, that the solid interstitia of the Wood are the combustible matter. Further, the reason why uncharr’d Wood burns with a greater flame then that which is charr’d, is as evident, because those waterish or volatil parts issuing out of the fired Wood, every way, not onely shatter and open the body, the better for the fire to enter, but issuing out in vapours or wind, they become like so many little aeolipiles, or Bellows, whereby they blow and agitate the fir’d part, and conduce to the more speedy and violent consumption or dissolution of the body.
Thirdly, from the Experiment of charring of Coals (whereby we see that notwithstanding the great heat, and the duration of it, the solid parts of the Wood remain, whilest they are preserv’d from the free access of the air undissipated) we may learn, that which has not, that I know of, been publish’d or hinted, nay, not so much as thought of, by any; and that in short is this.
First, that the Air in which we live, move, and breath, and which encompasses very many, and cherishes most bodies it encompasses, that this Air is the menstruum, or universal dissolvent of all Sulphureous bodies.
Secondly, that this action it performs not, till the body be first sufficiently heated, as we find requisite also to the dissolution of many other bodies by several other menstruums.
Thirdly, that this action of dissolution, produces or generates a very great heat, and that which we call Fire; and this is common also to many dissolutions of other bodies, made by menstruums, of which I could give multitudes of Instances.