Micrographia Part 10

Nor is _Marble_ the only seemingly close stone, which by other kinds of Experiments may be found porous; for I have by this kind of Experiment on divers other stones found much the same effect, and in some, indeed much more notable. Other stones I have found so porous, that with the _Microscope_ I could perceive several small winding holes, much like Worm-holes, as I have noted in some kind of _Purbeck-stone_, by looking on the surface of a piece newly flaw'd off, for if otherwise, the surface has been long expos'd to the Air, or has been sc.r.a.ped with any tool, those small caverns are fill'd with dust, and disappear.

And to confirm this _Conjecture_, yet further, I shall here insert an excellent account, given into the _Royal Society_ by that Eminently Learned Physician, Doctor _G.o.ddard_, of an Experiment, not less instructive then curious and accurate, made by himself on a very hard and seemingly close stone call'd _Oculus Mundi_, as I find it preserv'd in the Records of that Honourable Society.

A small stone of the kind, call'd by some Authours, _Oculus Mundi_, being dry and cloudy, weigh'd 5-209/256 _Grains_.

The same put under water for a night, and somewhat more, became transparent, and the superficies being wiped dry, weighed 6-3/256 _Grains_.

The difference between these two weights, 0-50/256 of a _Grain_.

The same Stone kept out of water one Day and becoming cloudy again weighed, 5-225/256 _Graines_.

Which was more then the first weight, 0-16/256 of a _Grain_.

The same being kept two Days longer weighed, 5-202/256 _Graines_.

Which was less then at first, 0-7/256 a _Grain_.

Being kept dry something longer it did not grow sensibly lighter.

Being put under water for a night and becoming again transparent and wiped dry, the weight was, _6-3/256 Grains_, the same with the first after putting in water, and more then the last weight after keeping of it dry, 0-57/256 of a _Grain_.

Another Stone of the same kind being variegated with milky _white_ and _gray_ like some sorts of _Agates_, while it lay under water, was alwaies invironed with little Bubbles, such as appear in water a little before boyling, next the sides of the Vessel.

There were also some the like Bubbles on the Surface of the water just over it, as if either some exhalations came out of it, or that it did excite some fermentation in the parts of the water contiguous to it.

There was little sensible difference in the transparency of this Stone, before the putting under water, and after: To be sure the milky-_white_ parts continued as before, but more difference in weight then in the former. For whereas before the putting into the water the weight was 18-97/128 _Graines_. After it had lyen in about four and twenty hours the weight was 20-27/128 _Graines_, so the difference was, 1-58/128 _Graines_.

The same Stone was infused in the water scalding hot, and so continued for a while after it was cold, but got no more weight then upon infusing in the cold, neither was there any sensible Difference in the weight both times.

In which Experiment, there are three Observables that seem very manifestly to prove the porousness of these seemingly close bodies: the first is their acquiring a transparency, and losing their whiteness after steeping in water, which will seem the more strongly to argue it, if what I have already said about the making transparent, or clarifying of some bodies, as the white powder of beaten Gla.s.s, and the froth of some glutinous transparent liquor be well consider'd; for thereby it will seem rational to think that this transparency arises from the insinuation of the water (which has much the same refraction with such stony particles, as may be discover'd by Sand view'd with a _Microscope_) into those pores which were formerly repleat with air (that has a very differing refraction, and consequently is very reflective) which seems to be confirm'd by the second Observable, namely, the increase of weight after keeping, and decrease upon drying. And thirdly, seem'd yet more sensibly confirm'd by the mult.i.tude of bubbles in the last Experiment.

We find also most Acid Salts very readily to dissolve and separate the parts of this body one from another; which is yet a further Argument to confirm the porousness of bodies, and will serve as such, to shew that even Gla.s.s also has an abundance of pores in it, since there are several liquors, that with long staying in a Gla.s.s, will so _Corrode_ and eat into it, as at last, to make it pervious to the liquor it contain'd, of which I have seen very many Instances.

Since therefore we find by other proofs, that many of those bodies which we think the most solid ones, and appear so to our sight, have notwithstanding abundance of those grosser kind of pores, which will admit several kinds of liquors into them, why should we not believe that Gla.s.s, and all other transparent bodies abound with them, since we have many other arguments, besides the propagation of light, which seem to argue for it?

And whereas it may be objected, that the propagation of light is no argument that there are those atomical pores in gla.s.s, since there are _Hypotheses_ plausible enough to solve those _Phaenomena_, by supposing the pulse onely to be communicated through the transparent body.

To this I answer, that that _Hypothesis_ which the industrious _Mersennus_ has publish'd about the slower motion of the end of a Ray in a denser _medium_, then in a more rare and thin, seems altogether unsufficient to solve abundance of _Phaenomena_, of which this is not the least considerable, that it is impossible from that supposition, that any colours should be generated from the refraction of the Rays; for since by that _Hypothesis_ the _undulating pulse_ is always carried perpendicular, or at right angles with the Ray or Line of direction, it follows, that the stroke of the pulse of light, after it has been once or twice refracted (through a Prisme, for example) must affect the eye with the same kind of stroke as if it had not been refracted at all. Nor will it be enough for a Defendant of that _Hypothesis_, to say, that perhaps it is because the refractions have made the Rays more weak, for if so, then two refractions in the two parallel sides of a _Quadrangular Prisme_ would produce colours, but we have no such _Phaenomena_ produc'd.

There are several Arguments that I could bring to evince that there are in all transparent bodies such atomical pores. And that there is such a fluid body as I am arguing for, which is the _medium_, or Instrument, by which the pulse of Light is convey'd from the _lucid body_ to the enlightn'd. But that it being a digression from the Observations I was recording, about the Pores of _Kettering Stone_, it would be too much such, if I should protract it too long; and therefore I shall proceed to the next _Observation_.

Observ. XVI. _Of _Charcoal_, or burnt _Vegetables_._

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 mult.i.tude 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 s.p.a.ce between them to be fill'd with a solid body, for the apparent _interst.i.tia_ 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 part.i.tions 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 numbring 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 containe 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 Vitae_, &c. I found, that all these Woods have their pores, abundantly smaller then those of soft light Wood; in so much, that those of _Guajac.u.m_ seem'd not above an eighth part of the bigness of the pores of Beech, but then the _Interst.i.tia_ 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 _Phaenomena_ 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 wheresover 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 _interst.i.tia_ 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 _Interst.i.tia_ 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 ma.s.s of it, and thereby caus'd an universal kind of transparency, that it not onely leaves all the pores empty, but all the _Interst.i.tia_ 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 Gla.s.s, 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 quant.i.ty 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 _interst.i.tia_ 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 encompa.s.ses very many, and cherishes most bodies it encompa.s.ses, 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 mult.i.tudes 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 mult.i.tudes 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 cl.u.s.ters, 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 const.i.tution; 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 _Phaenomena_, of Fire, and so genuinely explicate each particular circ.u.mstance that I have hitherto observ'd, that it is more then probable, that this cause which I have a.s.sign'd is the true adequate, real, and onely cause of those _Phaenomena_; 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 quant.i.ty 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 appet.i.te of uniting with that as its _h.o.m.ogeneal_ 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 encompa.s.sing 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 dissolution 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. .h.i.therto 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 _Phaenomena_ 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 _Phaenomena_ 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 const.i.tution 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 G.o.d 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 a-cross, 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 Fire, to which it is not much unlike in grain also, and several other proprieties.