Charcoal, or a Vegetable burnt black, affords an object no less pleasant
than instructive, for if you take a small round Charcoal, and break it
short with your fingers, you may perceive it to break with a very smooth
and sleek surface, almost like the surface of black sealing Wax; this
surface, if it be look’d on with an ordinary _Microscope_, does manifest
abundance of those pores which are also visible to the eye in many kinds of
_Wood_, rang’d round the pith, both a in kind of circular order, and a
radiant one. Of these there are a multitude in the substance of the Coal,
every where almost perforating and drilling it from end to end; by means of
which, be the Coal never so long, you may easily blow through it; and this
you may presently find, by wetting one end of it with Spittle, and blowing
at the other.
But this is not all, for besides those many great and conspicuous irregular
spots or pores, if a better _Microscope_ be made use of, there will appear
an infinite company of exceedingly small, and very regular pores, so thick
and so orderly set, and so close to one another, that they leave very
little room or space between them to be fill’d with a solid body, for the
apparent _interstitia_ or separating sides of these pores seem so thin in
some places, that the texture of a Honey-comb cannot be more porous. Though
this be not every where so, the intercurrent partitions in some places
being very much thicker in proportion to the holes.
Most of these small pores seem’d to be pretty round, and were rang’d in
rows that radiated from the pith to the bark; they all of them seem’d to be
continued open pores, running the whole length of the Stick; and that they
were all perforated, I try’d by breaking off a very thin sliver of the Coal
cross-ways, and then with my _Microscope_, diligently surveying them
against the light, for by that means I was able to see quite through them.
These pores were so exceeding small and thick, that in a line of them, ¹⁄₁₈
part of an Inch long, I found by numbering them no less then 150. small
pores; and therefore in a line of them an Inch long, must be no less then
2700. pores, and in a circular _area_ of an Inch diameter, must be about
5725350. of the like pores; so that a Stick of an Inch Diameter, may
contain no less then seven hundred and twenty five thousand, besides 5
Millions of pores, which would, I doubt not, seem even incredible, were not
every one left to believe his own eyes. Nay, having since examin’d _Cocus,
black and green Ebony, Lignum Vitæ_, &c. I found, that all these Woods have
their pores, abundantly smaller then those of soft light Wood; in so much,
that those of _Guajacum_ seem’d not above an eighth part of the bigness of
the pores of Beech, but then the _Interstitia_ were thicker; so
prodigiously curious are the contrivances, pipes, or sluces by which the
_Succus nutritius_, or Juyce of a Vegetable is convey’d from place to
place.
This _Observation_ seems to afford us the true reason of several
_Phænomena_ of Coals; as
First, why they look black; and for this we need go no further then the
_Scheme_, for certainly, a body that has so many pores in it as this is
discover’d to have, from each of which no light is reflected, must
necessarily look black, especially, when the pores are somewhat bigger in
proportion to the intervals then they are cut in the _Scheme_, black being
nothing else but a privation of Light, or a want of reflection; and
wheresoever this reflecting quality is deficient, there does that part look
black, whether it be from a porousness of the body, as in this Instance, or
in a deadning and dulling quality, such as I have observ’d in the _Scoria_
of Lead, Tin, Silver, Copper, &c.
Next, we may also as plainly see the reason of its shining quality, and
that is from the even breaking off of the stick, the solid _interstitia_
having a regular termination or surface, and having a pretty strong
reflecting quality, the many small reflections become united to the naked
eye, and make a very pretty shining surface.
Thirdly, the reason of its hardness and brittleness seems evident, for
since all the watery or liquid substance that moistn’d and toughn’d those
_Interstitia_ of the more solid parts, are evaporated and remov’d, that
which is left behind becomes of the nature almost of a stone, which will
not at all, or very little, bend without a _divulsion_ or _solution_ of its
_continuity_.
It is not my design at present, to examine the use and _Mechanisme_ of
these parts of Wood, that being more proper to another Enquiry; but rather
to hint, that from this Experiment we may learn,
First, what is the cause of the blackness of many burnt bodies, which we
may find to be nothing else but this; that the heat of the fire agitating
and rarifying the waterish, transparent, and volatile water that is
contain’d in them, by the continuation of that action, does so totally
expel and drive away all that which before fill’d the pores, and was
dispers’d also through the solid mass of it, and thereby caus’d an
universal kind of transparency, that it not onely leaves all the pores
empty, but all the _Interstitia_ also so dry and _opacous_, and perhaps
also yet further perforated, that that light onely is reflected back which
falls upon the very outward edges of the pores, all they that enter into
the pores of the body, never returning, but being lost in it.
Now, that the Charring or coaling of a body is nothing else, may be easily
believ’d by one that shall consider the means of its production, which may
be done after this, or any such manner. The body to be charr’d or coal’d,
may be put into a _Crucible_, Pot, or any other Vessel that will endure to
be made red-hot in the fire without breaking, and then cover’d over with
Sand, so as no part of it be suffer’d to be open to the Air, then set into
a good fire, and there kept till the Sand has continu’d red hot for a
quarter, half, an hour or two, or more, according to the nature and bigness
of the body to be coal’d or charr’d, then taking it out of the fire, and
letting it stand till it be quite cold, the body may be taken out of the
Sand well charr’d and cleans’d of its waterish parts; but in the taking of
it out, care must be had that the Sand be very neer cold, for else, when it
comes into the free air, it will take fire, and readily burn away.
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 _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 _Salt-peter_, 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 agitation that kept it rarify’d ceases, it easily condenses, and
commixt with other indissoluble parts, it sticks and adheres to the next
bodies it meets withall; and this is a certain _Salt_ that may be extracted
out of _Soot_.
Eighthly, that many indissoluble parts being very apt and prompt to be
rarify’d, and so, whilest they continue in that heat and agitation, are
lighter then the Ambient Air, are thereby thrust and carry’d upwards with
great violence, and by that means carry along with them, not onely that
_Saline concrete_ I mention’d before, but many terrestrial, or indissoluble
and irrarefiable parts, nay, many parts also which are dissoluble, but are
not suffer’d to stay long enough in a sufficient heat to make them prompt
and apt for that action. And therefore we find in _Soot_, not onely a part,
that being continued longer in a competent heat, will be dissolv’d by the
Air, or take fire and burn; but a part also which is fixt, terrestrial, and
irrarefiable.
Ninthly, that as there are these several parts that will rarifie and fly,
or be driven up by the heat, so are there many others, that as they are
indissoluble by the _aerial menstruum_, so are they of such sluggish and
gross parts, that they are not easily rarify’d by heat, and therefore
cannot be rais’d by it; the volatility or fixtness of a body seeming to
consist only in this, that the one is of a texture, or has component parts
that will be easily rarify’d into the form of Air, and the other, that it
has such as will not, without much ado, be brought to such a constitution;
and this is that part which remains behind in a white body call’d Ashes,
which contains a substance, or _Salt_, which Chymists call _Alkali_: what
the particular natures of each of these bodies are, I shall not here
examine, intending it in another place, but shall rather add that this
_Hypothesis_ does so exactly agree with all _Phænomena_, of Fire, and so
genuinely explicate each particular circumstance that I have hitherto
observ’d, that it is more then probable, that this cause which I have
assign’d is the true adequate, real, and onely cause of those _Phænomena_;
And therefore I shall proceed a little further, to shew the nature and use
of the Air.
Tenthly, therefore the dissolving parts of the Air are but few, that is, it
seems of the nature of those _Saline menstruums_, or spirits, that have
very much flegme mixt with the spirits, and therefore a small parcel of it
is quickly glutted, and will dissolve no more; and therefore unless some
fresh part of this _menstruum_ be apply’d to the body to be dissolv’d, the
action ceases, and the body leaves to be dissolv’d and to shine, which is
the Indication of it, though plac’d or kept in the greatest heat; whereas
_Salt-peter_ is a _menstruum_, when melted and red-hot, that abounds more
with those Dissolvent particles, and therefore as a small quantity of it
will dissolve a great sulphureous body, so will the dissolution be very
quick and violent.
Therefore in the _Eleventh_ place, it is observable, that, as in other
solutions, if a copious and quick supply of fresh _menstruum_, though but
weak, be poured on, or applied to the dissoluble body, it quickly consumes
it: So this _menstruum_ of the Air, if by Bellows, or any other such
contrivance, it be copiously apply’d to the shining body, is found to
dissolve it as soon, and as violently as the more strong _menstruum_ of
melted _Nitre_.
Therefore twelfthly, it seems reasonable to think that there is no such
thing as an Element of Fire that should attract or draw up the flame, or
towards which the flame should endeavour to ascend out of a desire or
appetite of uniting with that as its _Homogeneal_ primitive and generating
Element; but that that shining transient body which we call _Flame_, is
nothing else but a mixture of Air, and volatil sulphureous parts of
dissoluble or combustible bodies, which are acting upon each other whilst
they ascend, that is, flame seems to be a mixture of Air, and the
combustible volatil parts of any body, which parts the encompassing Air
does dissolve or work upon, which action, as it does intend the heat of the
_aerial_ parts of the dissolvent, so does it thereby further rarifie those
parts that are acting, or that are very neer them, whereby they growing
much lighter then the heavie parts of that _Menstruum_ that are more
remote, are thereby protruded and driven upward; and this may be easily
observ’d also in dissolutions made by any other _menstruum_, especially such
as either create heat or bubbles. Now, this action of the _Menstruum_, or
_Air_, on the dissoluble parts, is made with such violence, or is such,
that it imparts such a motion or pulse to the _diaphanous_ parts of the
Air, as I have elsewhere shewn is requisite to produce light.
This _Hypothesis_ I have endeavoured to raise from an Infinite of
Observations and Experiments, the process of which would be much too long
to be here inserted, and will perhaps another time afford matter copious
enough for a much larger Discourse, the Air being a Subject which (though
all the world has hitherto liv’d and breath’d in, and been unconversant
about) has yet been so little truly examin’d or explain’d, that a diligent
enquirer will be able to find but very little information from what has
been (till of late) written of it: But being once well understood, it will,
I doubt not, inable a man to render an intelligible, nay probable, if not
the true reason of all the _Phænomena_ of Fire, which, as it has been found
by Writers and Philosophers of all Ages a matter of no small difficulty, as
may be sufficiently understood by their strange _Hypotheses_, and
unintelligible Solutions of some few _Phænomena_ of it; so will it prove a
matter of no small concern and use in humane affairs, as I shall elsewhere
endeavour to manifest when I come to shew the use of the Air in
respiration, and for the preservation of the life, nay, for the
conservation and restauration of the health and natural constitution of
mankind as well as all other aereal _animals_, as also the uses of this
principle or propriety of the Air in chymical, mechanical, and other
operations. In this place I have onely time to hint an _Hypothesis_, which,
if God permit me life and opportunity, I may elsewhere prosecute, improve
and publish. In the mean time, before I finish this Discourse, I must not
forget to acquaint the Reader, that having had the liberty granted me of
making some trials on a piece of _Lignum fossile_ shewn to the Royal
Society, by the eminently Ingenious and Learned Physician, Doctor _Ent_,
who receiv’d it for a Present from the famous _Ingenioso Cavalliero de
Pozzi_, it being one of the fairest and best pieces of _Lignum fossile_ he
had seen; Having (I say) taken a small piece of this Wood, and examin’d it,
I found it to burn in the open Air almost like other Wood, and insteed of a
resinous smoak or fume, it yielded a very bituminous one, smelling much of
that kind of sent: But that which I chiefly took notice of, was, that
cutting off a small piece of it, about the bigness of my Thumb, and
charring it in a _Crucible_ with Sand, after the manner I above prescrib’d,
I found it infinitely to abound with the smaller sort of pores, so
extreamly thick, and so regularly perforating the substance of it
long-ways, that breaking it off across, I found it to look very like an
Honey-comb; but as for any of the second, or bigger kind of pores, I could
not find that it had any; so that it seems, whatever were the cause of its
production, it was not without those small kind of pores which we have
onely hitherto found in Vegetable bodies: and comparing them with the pores
which I have found in the Charcoals that I by this means made of several
other kinds of Wood, I find it resemble none so much as those of Firr, to
which it is not much unlike in grain also, and several other proprieties.
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:
* * * * *