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 æolipiles, 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.
Fourthly, that this action is perform'd with so great a violence, and does so minutely act, and rapidly agitate the smallest parts of the combustible matter, that it produces in the diaphanous medium of the Air, the action or pulse of light, which what it is, I have else-where already shewn.
Fifthly, that the dissolution of sulphureous bodies is made by a substance inherent, and mixt with the Air, that is like, if not the very same, with that which is fixt in Salt-peter, which by multitudes of Experiments that may be made with Saltpeter, will, I think, most evidently be demonstrated.
Sixthly, that in this dissolution of bodies by the Air, a certain part is united and mixt, or dissolv'd and turn'd into the Air, and made to fly up and down with it in the same manner as a metalline or other body dissolved into any menstruums, does follow the motions and progresses of that menstruum till it be precipitated.
Seventhly, That as there is one part that is dissoluble by the Air, so are there other parts with which the parts of the Air mixing and uniting, do make a Coagulum, or precipitation, as one may call it, which causes it to be separated from the Air, but this precipitate is so light, and in so small and rarify'd or porous clusters, that it is very volatil, and is easily carry'd up by the motion of the Air, though afterwards, when the heat and
