TRACTS: CONTAINING I …

TRACTS: CONTAINING

  • I. SUSPICIONS about some Hidden Qualities of the AIR; with an Appendix touching CELESTIAL MAGNETS, and some other Particulars.
  • II. ANIMADVERSIONS upon Mr. Hobbes's PROBLEMATA De VACUO.
  • III. A DISCOURSE of the CAUSE of Attraction by SUCTION.

By the Honourable ROBERT BOYLE, Esq Fellow of the ROYAL SOCIETY.

LONDON, Printed by W.G. and are to be Sold by M. Pitt, at the Angel against the Little North Door of St. Paul's Church. 1674.

Preface.

AMong other Papers that I design'd to contribute to­wards the Natural Hi­story of the Air, I began some years ago to set down a Collection of some new or less heeded Obser­vations and Experiments relating to the Causes and Effects of Changes in the Air, which I re­ferr'd to several Heads, as to the Airs Heat, Coldness, Moisture, Driness, Diaphaneity, Opacity, Consistence, several Saltnesses and other Titles; the last of which was [Page] of the Occult Qualities of the Air, supposing there be any such. And though afterwards I was, by Sick­ness and other Impediments, di­verted from proceeding in that Collection, and induc'd to lay aside some of the Observations I had provided, and imploy in other Treatises such as were proper to them; yet as to the Title that con­tain'd Suspicions about some Hidden Qualities of the Air, the possibility, if not likelihood, that either the Matters of fact, or the Intimations delivered in them, might afford hints not useless to the S [...]gacious and Inquisitive, per­swaded me to let it escape the Fate of its Companions, though possi­bly, if I had more consulted my own Reputation, I should least of all have suffer'd this Title to ap­pear, [Page] there being none of the rest, that was not less conjectural. But it being thought unfit, that any thing should perish, that related to so considerable and uncommon a Subject, as that of this Title, I was content to cast the collected Experiments into the following Essay for the Reasons express'd at the beginning and close of the in­suing Paper. Which, 'twas hop'd, may be the better understood, and less liable to have its Design mi­staken, by being usher'd in by this Advertisement about the occasion of it.

ERRATA.

IN the first Tract, pag. 41. l. 4. read Halicarnasseus.

In the Tract of the Cause of Suction, p. 14. l. 4. r. 33½ for 36½.

SVSPICIONS ABOUT Some Hidden QUALITIES in the AIR.

BEsides the four first Qua­lities of the Air, (Heat, Cold, Dryness and Moi­sture) that are known even to the Vulgar; and those more unobvious, that Philoso­phers and Chymists have discovered, such as Gravity, Springiness, the power of Refracting the beams of Light; &c. I have often suspected, that there may be in the Air some yet more latent Qualities or Powers dif­fering enough from all these, and principally due to the Substantial Parts or Ingredients, whereof it con­sists. [Page 2] And to this conjecture I have been led, partly (though not only or perhaps chiefly) by considering the Constitution of that Air we live and breath in, which, to avoid ambigui­ties, I elsewhere call Atmospherical Air. For this is not, as many imagine, a Simple and Elementary Body, but a confus [...]d Aggregate of Effluviums from such differing Bodies, that, though they all agree in constituting, by their minuteness and various mo­tions, one great mass of Fluid matter, yet perhaps there is scarce a more he­terogeneous Body in the world.

And as by Air I understand not (as the Peripateticks are wont to do) a meer Elementary Body; so, when I speak of the Qualities of the Air, I would not be thought to mean such naked and abstracted Beings (as the Schools often tell us of,) but such as they call Qualities in concreto, name­ly Corpuscles indued with Quali­ties, or capable of producing them in the Subjects they invade and a­bound in.

[Page 3]I have elsewhere shewn it to be highly probable, that, In a Paper a­boue Subter­raneal Steams. be­sides those vapours and ex­halations which by the Heat of the Sun are elevated into the Air, and there afford matter to some Meteors, as Clouds, Rain, Parhe­lions and Rainbow [...]; there are, at least at some times, and in some pla­ces, store of Effluviums emitted from the Subterraneal parts of the Terre­strial Globe; and 'tis no less probable, (from what I have there and else­where deliver'd,) that in the Subter­raneal Regions there are many Bodies, some fluid and some consistent, which, though of an operative nature, and like upon occasion to emit steams, sel­dom or never appear upon the surface of the Earth, so that many of them have not so much as names assigned them even by the Mineralists. Now a­mong this multitude and variety of Bodies, that lye buried out of our sight, who can tell but that there may be some, if not many, of a nature very differing from those we are hi­therto [Page 4] familiarly acquainted with; and that, as divers wonderful and peculiar operations of the Loadstone, (though a Mineral many Ages ago fa­mous among Philosophers and Phy­sitians,) were not discovered 'till of later Ages, wherein its nobler Virtues have been disclosed; so there may be other Subterraneous Bodies, that are indowed with considerable powers, which to us are yet unknown, and would, if they were known, be found very differing from those of the Fossiles we are wont to deal with?

I also further consider, that, (as I have elsewhere endeavoured to make it probable) the Sun and Planets (to say nothing of the Fixt Stars) may have influences here below distinct from their Heat and Light. On which Supposition it seems not absurd to me to suspect, that the Subtil, but Cor­poreal, Emanations even of these Bo­dies may (sometimes at least) reach to our Air, and mingle with those of our Globe in that great receptacle or rendevouz of Celestial and Ter­restrial [Page 5] Effluviums, the Atmosphere. And if this suspition be not ground­less, the very small knowledge we have of the structure and constitution of Globes so many thousands or hun­dred of thousands of miles remote from us, and the great ignorance we must be in of the nature of the par­ticular Bodies that may be presum'd to be contain'd in those Globes, (as Minerals and other Bodies are in the Earth,) which in many things ap­pear of kin to those that we inhabit, (as with excellent Telescopes I have often with attention and pleasure ob­served, particularly in the Moon,) this great imperfection, I say, of our knowledge may keep it from being unreasonable to imagine, that some, if not many, of those Bodies and their effluxions may be of a nature quite differing from those we take no­tice of here about us, and conse­quently may operate after a very diffe­ring and peculiar manner.

And though the chief of the He­teroclite Effluviums, that indow the [Page 6] Air with hidden Qualities, may pro­bably proceed from beneath the sur­face of the Earth, and from the Ce­lestial Bodies; yet I would not deny but that, especially at some times and in some places, the Air may derive multitudes of efficacious particles from its own operations, acting as a fluid Substance upon that vast number and variety of Bodies that are imme­diately expos'd to it. For, though by reason of its great thinness, and of its being in its usual state devoid both of tast and smell, it seems whol­ly unfit to be a Menstruum; yet I am not sure but it may have a dissol­ving, or at least a consuming, power on many Bodies, especially such as are peculiarly dispos'd to admit its ope­rations.

For I consider, that the Air has a great advantage by the vast Quantity of it, that may come to work in pro­portion to the Bodies that are expos'd to it: And I have long thought, that, in divers cases, the Quantity of a Menstruum may much more conside­rably [Page 7] compensate its want of strength, than Chymists are commonly aware of, (as there may be occasion else­where to exemplifie.) And there are liquors, which pass for insipid, (and are therefore thought to be altoge­ther unfit to be Solvents,) which, though they have their active parts too thinly dispersed to be able pre­sently to make sensible Impressions upon our Organs of Tasting, yet are not quite destitute of Corpuscles fit to act as a Solvent; especially if they have time enough to make with the other parts of the Fluid such nu­merous and various motions, as must bring, now some of them, and then others, to hit against the Body ex­pos'd to them. Which may be illu­strated by the Rust like to Verdigrease, which we have observ'd in Copper that has been long expos'd to the Air, whose saline particles, little by little, do in tract of time fasten themselves in such numbers to the surface of the Metal as to corrode it, and produce that efflorescence colour'd like Verdi­grease, [Page 8] which you know is a facti­tious Body, wont to be made of the same Metal, corroded by the sharp Corpuscles of Vineger, or of the Husks of Grapes: Besides, that by the power, which Mercury has to dissolve Gold and Silver, it appears, that it is not always necessary for the making a Fluid fit to be a Dissolvent, that it should affect the Tast. And as to those Bodies, on which the Ae­rial Menstruum can, though but slow­ly, work, the greatest quantity of it may bring it this advantage, that, whereas even the strongest Men­struums, if they bear no great propor­tion in bulk to the Bodies they are to work on, are easily glutted, and be­ing unable to take up any more, are fain to leave the rest of the Body un­dissolved, our Aerial Menstruum bears so vast a proportion to the Bodies ex­pos'd to it, that when one portion of it has impregnated it self as much as 'tis able, there may still come fresh and fresh to work further on the re­maining part of the expos'd Body.

[Page 9]Besides the Saline and Sulphureous particles, that, at least in some pla­ces, may (as I have elsewhere shewn) impregnate the Air, and give it a greater affinity to Chymical Men­struums more strictly so called; I am not averse from thinking, that the Air, meerly as a fluid Body, that consists of Corpuscles of differing sizes and so­lidities restlesly and very variously moved, may upon the account of these Corpuscles be still resolving, or preying upon, the particles of the Bodies that are expos'd to their action. For, many of those Aerial Corpu­scles, some hitting and some rubbing themselves every minute against those particles of expos'd Bodies that chance to lye in their way, may well, by those numerous occursions and affri­ctions, strike off and carry along with them now some and then others of those particles; as you see it hap­pens in water, which, as soft and fluid as it is, wears out such hard and solid Bodies as Stones themselves, if it often enough meet them in its [Page 10] passage, according to the known saying,

Gutta cavat Lapidem non vi, sed saepe cadendo.

And though the Aerial Corpuscles be very minute, and the Bodies expos'd to them oftentimes large and see­mingly solid; yet this needs not make you reject our supposition, because 'tis not upon the whole Body at once, that, according to us, the Aerial Corpuscles endeavour to work, but upon the Superficial particles, which may often be more minute than those Corpuscles; as you will the more ea­sily believe, if you first observe with a good Microscope, how many ex­tant particles may be met with on the surface of Bodies, that to the naked Eye seem very smooth, and even of those that are polish'd by Art with Tripoly or Puttee; and then consider, that one of these protuberancies, be­ing yet manifestly visible, may well be presum'd to consist of a multitude [Page 11] of lesser particles, divers of which may very well be as minute as those Aerial Corpuscles, that successively hit against them, and endeavour to carry them along with themselves. And this may be illustrated by a fami­liar instance. For, if you take a lump of Loaf Sugar, or even of a much so­lider and harder Body, Sal Gemmae, and cast it into common water, though this liquor be insipid, and the motions of its corpuscles but very languid; yet these corpuscles are ca­pable to loosen and carry off the su­perficial particles of Sugar or Salt, that chance to lye in their way, and fresh corpuscles of water still suc­ceeding to work upon the remaining particles of the expos'd Body that stand in their way, the whole lump is by little and little dissolved, and ceases to appear to the Eye a thing di­stinct from the liquor.

Some things that have occurr'd to me have made me suspect, that 'tis not impossible, but that some Bodies may receive a disposition to Volatility, [Page 12] and consequently to pass into the Air by the action either of the Sun-beams, in the form of the Sun-beams, or of some substance that once issued out of the Sun and reach'd unto our Air. For, there may be certain Bo­dies for the most part in the form of liquors, which, though they pass off from some peculiarly dispos'd Bo­dies, may during their stay or con­tact produce in them a great and strange aptness to be volatiliz'd. In favour of which conjecture, I might here alledge both the effects, which the Paracelsians and Helmontians ascribe to the Alkahest of volatilizing even fixt and ponderous Bodies barely by being often abstracted from them, and some other things, which I shall now leave unmention'd, because you may find them in my Notes about Vo­latility and Fixity.

But, whatever become of this Con­jecture, 'tis consonant to Experience, that, either upon the above-recited accounts, or also some others, those parts of the Atmosphere, which, in [Page 13] a stricter sense, may be call'd the Air, are, at least in some places, so in­termixt with particles of differing kinds, that among that great num­ber of various sorts of them, 'tis very likely that there should be some kinds of an un-common and an un­observed nature. And I could coun­tenance what has been said by the wasting of Odorous Bodies, and espe­cially Camphire, and by representing, that I have observed some solid Bodies actually cold, when their superficial parts were newly taken off, to emit, though invisibly, such copious steams into the Air, as to grow continually and manifestly lighter upon the bal­lance, so as to suffer a notable decre­ment of weight in a minute of an hour. But the mention I make of such things in an other paper, dis­swades me from insisting on them here, where 'twill be seasonable to resume the discourse, which the men­tion of the Dissolving power, that may be guess'd to be in the Air, has for some pages interrupted, and to tell [Page 14] you, that those propounded, before I enter'd upon the digression, are the two main Consideration à priori (as they speak) whereon I have groun­ded my surmize, which being pro­pos'd but as a Suspicion, I presume it will not be expected, that the Argu­ments à posteriori, which I shall bring to countenance it, should be more than Conjectures, much less that they should be Demonstrations. And there­fore I shall venture to lay before you some few Phaenomena, which seem to be at least as probably referable to some latent Quality in the Air, as to any other cause I yet know. Upon which score such Phaenomena may be allowed to be pleaded in favour of our Suspicion, 'till some other certain cause of them shall be satisfactorily assign'd.

Having premis'd thus much to keep you from looking for stronger proofs than I think my task obliges me to give; the first Phaenomenon, I shall propose, shall be the appearing or growth of some Salts in certain [Page 15] Bodies, which we observ'd to afford them either not at all, or at least nothing near in such plenty, or so soon, unless they be expos'd to the Air. Of such a Phaenomenon as this, that is not so much as mention'd by Vulgar Philosophers, and very rarely, if at all, to be met with in the La­boratories of Chymists, you will not, I suppose, wonder, that I do not present you many Examples, and some few I am able to name. For I remember, that suspecting a solid Marchasite, hard as stone, to be fit to be made an instance for my pur­pose, I caus'd it to be broken, that the internal more shining parts might be expos'd to the Air; but, though this were done in a room, where a good fire was usually kept, so that the Marchasite was not only shelter'd from the rain, but kept in a dry Air, yet after a while I discover'd upon the glistering parts an efflorescence of a vitriolate nature.

And afterwards meeting with a ponderous and dark colour'd Mineral, [Page 16] and which, at the first breaking, discover'd to the Eye no appearance of any Salt, nor so much as any shi­ning Marchasitical particles, we found nevertheless, that a good quantity of these hard and heavy Bodies, being kept expos'd to the Air, even in a room that preserved them from the rain, though probably they had lain many ages intire in the hill, wherein they were found under ground; yet in not many months, by the opera­tion of the Air upon them, they were, in great part, crumbled to powder exceeding rich in Copperas. Nay, I remember, that having for Curio­sities sake, laid up some of these stones in a room, where I constantly kept fire, and in the drawer of a Ca­binet, which I did not often take out to give them fresh Air, some, if not most of them, were notwithstanding [...]over'd with a copious efflorescence, which by its conspicuous colour be­tween blew and green, by its taste, and by its fitness to make in a trice an inky mixture with infusion of [Page 17] galls, sufficiently manifested it self to be Vitriol; whose growth by the help of the contact of the Air is the more considerable, because it is not a meer Acid Salt, but abounds in Sulphureous and Combustible parts, which I have divers times been able, by Methods elsewhere mentioned, actually to separate or obtain from common Vitriol without the addition of any combustible body, and some­times without any additament at all. It was also uncommon, that our blackish Minerals requir'd no longer time, nor no rain, to make them af­ford their Vitriolate Efflorescences: For I remember, I kept many of those Marchasites, both glittering ones and others, of which they make and sell great quantities of Vitriol at Deptford, without perceiving in them a change that came any thing near to what I have recited. And I observ'd those, whose trade it is to make Vitriol, to be often obliged to let their Vitriol-stones, as they call them, lye half a year, or even eighteen months, or [Page 18] two years exposed, not only to the open Air, but to the Rain and Sun, to be able to obtain from them their Vitriolate parts.

That also the Earth or Ore of Al­lum, being robb'd of its Salt, will in tract of time recover it by being expos'd to the Air, we are assur'd by the experienc'd Agricola, where, having deliver'd the way of making Allum, he subjoins this Advertise­ment: Terra Aluminosa, quae in castel­lis diluta, postquam effluxit, superfuit egesta et coacervata quotidie, rursus ma­gis & magis fit aluminosa, non aliter atque terra ex qua halinitrum fuit con­fectum, suo succo plenior fit; quare de­nuo in Castella conjicitur & aquae affu­sae ea percolantur.

I have likewise observ'd, as you also perchance have done, that some kind of Lime in old walls and moist places has gain'd in length of time a copious efflorescence, very much of a Nitrous Nature; as I was convinc'd by having obtain'd Salt-peter from it by barely dissolving it in common [Page 19] water, and evaporating the filtrated Solution: And that in calcin'd Vi­triol, whose saline parts have been driven away by the violence of the fire, particles of fresh Salt may be found after it has lain a competent time in the Air, I shall e're long have occasion to inform you.

But in the mean time, (to deal in­genuously with you,) I shall freely confess to you, that, though these and the like observations have satis­fied Learned men, without having been call'd in question, and conse­quently have, at least, probability enough to ground our Suspicion upon; yet I, that am more concern'd for the Discovery of a Truth than the Reputation of a Paradox, propose the Argument drawn from the foregoing Observations, but as a Probationer. For it yet seems to me somewhat doubtful, whether the Salts, that ap­pear in the forementioned cases, are really produc'd by the operation of the Air working as an Agent, or also concurring as an Ingredient; or whe­ther [Page 20] these saline substances be not the production of some internal thing that is analagous to a Seminal Prin­ciple, which makes in these bodies a kind of maturation of some parts, which being once ripen'd, and per­haps assisted by the moisture of the Air, disclose themselves in the form of saline Concretions; as in the fe­culent or Tartareous parts of many Wines there will in tract of time be generated or produc'd store of Cor­puscles of a saline nature, that pro­duce the acid taste we find in Tartar, especially that of Rhenish wine. It may also be suspected, that the for­merly mention'd Salts found in Mar­chasites, in Nitrous and Aluminous Earths, &c. are made by the saline particles of the like nature, that among multitudes of other kinds swim in the Air, and are attracted by the congenerous particles, that yet remain in the Terrestrial bodies, that are, as it were, the wombs of such Minerals, (as I have elsewhere shewn, that Spirit of Nitre will, with fixt [Page 21] Nitre and some other Alkalys, com­pose Salt-peter;) or else, that these Aerial Salts, if I may so call them, assisted by the moisture of the Air, do soften and open, and almost cor­rode or dissolve the more Terrestrial Substance of these wombs, and there­by sollicit out and somewhat extri­cate the latent Saline particles, and, by their union with them, compose those Emerging bodies that resemble Vitriol, Allum, &c.

But not only to suggest these scru­ples, as if I had a mind they should but trouble you, and keep you irre­solute, I shall propound something towards the removal of them; name­ly, that a convenient quantity of Nitrous Earth, or that other of those Substances, which you would exa­mine, be kept in a close vessel to which the Air has not access, for at least as long time as has been obser­ved to be sufficient to impregnate the like substance, or rather a portion of the same parcel that was chosen to be included: For, if the body, that [Page 22] was kept close, have either gain'd no Salt at all, or very much less in pro­portion to its bulk than that which was kept expos'd, we may thence estimate, what is to be ascribed to the Air in the production of Nitre or other saline Concretions. And, be­cause I have observed none of these bodies, that would so soon, and so manifestly, even to the eye, disclose a saline substance, as the blackish Vitriol-Ore, I lately told you I kept in a drawer of my Cabinet; I judg'd that a very fit subject, wherewith to try, what maturation or time, when the Air was secluded, would perform towards the deciding of our Diffi­culty: And accordingly having ta­ken some fragments of it, which we had carefully freed from the adhering Vitriolate efflorescence, by whose plenty we were assured that it was very well dispos'd to be wrought on by the Air, we put of these frag­ments of differing sizes into two con­veniently shap'd glasses, which be­ing Hermetically sealed were ordered [Page 23] to be carried away, and kept in fit places; by which means 'twas ex­pected, that, even without opening the glasses, we should be able easily to see by the chang'd colour of the superficial parts, whether any Vitrio­late efflorescence were produced; but, through the negligence or mistake of those, to whom the care was recom­mended, the experiment was never brought to an issue; and though I afterwards got more of the Mineral, and made a second tryal of the same, I have not yet been inform'd of the event.

But, Sir, though, 'till the success of some such tryal be known, I dare not too confidently pronounce about the Production or Regeneration of Salts in bodies that have been robb'd of them, and ascribe it wholly to the Air; yet, when I consider the several and great effects of the Air upon divers other bodies, I think it not rash to conjecture in the mean time, that the operations of the Air may have a considerable share in these [Page 24] Phaenomena, and so that there may be latent Qualities in the Air, in the sense I declar'd above, where I told you, that, when I speak of these Qualities, I look upon them in Con­creto, (as they phrase it,) together with the Substances or [...]orporeal efflu­via they reside in: And of these Ae­rial Qualities, taken in this sense, I shall now proceed to mention some other Instances.

The Difficulty we find of keeping Flame and Fire alive, though but for a little time, without Air, makes me some times prone to suspect, that there may be dispers'd through the rest of the Atmosphere some odd sub­stance, either of a Solar, or Astral, or some other exotic, nature, on whose account the Air is so necessary to the subsistence of Flame; which Necessity I have found to be greater, and less dependent upon the manifest Attributes of the Air, than Natu­ralists seem to have observed. For I have found by tryals purposely made, that a small flame of a Lamp, though [Page 25] fed perhaps with a subtil thin Oyl, would in a large capacious glass-Re­ceiver expire, for want of Air, [...]in a far less time than one would be [...]eve. And it will not much lessen the diffi­culty to alledge, that either the gross fuliginous Smoak did in a close Ves­sel stifle the flame, or that the pres­sure of the Air is requisite to impel up the aliment into the wieck: For, to obviate these objections, I have in a large Receiver imploy'd a very small wieck with such rectified Spirit of Wine, as would in the free Air burn totally away; and yet, when a very small Lamp, furnished (as I was saying) with a very slender wieck, was made to burn, and, fill'd with this liquor, was put lighted into a large Receiver, that little flame, though it emitted no visible smoak at all, would usually expire within a­bout one minute of an hour, and, not seldom, in a less time; and this, though the wieck was not so much as sing'd by the flame: Nor indeed is a wieck necessary for the experi­ment, [Page 26] since highly rectified Spirit of Wine will in the free Air flame away well without it. And indeed it seems to [...]erve our wonder, what that should be in the Air, which inabling it to keep flame alive, does yet, by being consum'd or deprav'd, so sud­denly render the Air unfit to make flame subsist. And it seems by the sudden wasting or spoiling of this fine Subject, whatever it be, that the bulk of it is but very small in proportion to the Air it impregnates with its virtue. For after the ex­tinction of the flame, the Air in the Receiver was not visibly alter'd, and, for ought I could perceive by the ways of judging I had then at hand, the Air retain'd either All, or at least far the greatest part of its Ela­sticity, which I take to be its most genuine and distinguishing property.

And this undestroy'd springyness of the Air seems to make the necessity of fresh Air to the Life of hot Ani­mals, (few of which, as far as I can guess after many tryals, would [Page 27] be able to live two minutes of an hour, if they were totally and all at once deprived of Air,) suggest a great suspicion of some vital substance, if I may so call it, diffus'd through the Air, whether it be a volatile Nitre, or (rather) some yet anony­mous substance, Sydereal or Subter­raneal, but not improbably of kin to that, which I lately noted to be so necessary to the maintenance of o­ther flames.

I know not, whether you will think it pertinent to our present Discourse, that I observe to you, that by keeping putrifying bodies in glasses, which by Hermes his seal were secur'd from the contact of the external Air, I have not been able to produce any Insect or other living Creature, though sometimes I have kept Animal Substances and even Blood so included for many months, and one or two of them for a longer time; and though also these Substan­ces had a manifest change made in their consistence whilst they remain'd seal'd up.

[Page 28]On this occasion I shall add an odd Observation, that I met with in a little Dissertation de admirandis Hun­gariae aquis, written by an Anony­mous, but Ingenious, Nobleman of that Countrey, where, speaking of the native Salt that abounds in their Regions, he says, that in the chief Mine (by them call'd Desiensis) of Transylvania, there was, a few years before he writ, a great Oak like a huge beam dug out of the middle of the Salt; but, though it was so hard, that it would not easily be wrought upon by Iron-tools, yet being ex­pos'd to the Air out of the Mine, it became so rotten, as he expresses it, that in four days it was easie to be broken and crumbled between ones fingers. And of that corruptive or dissolutive Power of the Air near those Mines, the same Author men­tions other Instances.

Having found an Antimonial Pre­paration to procure Vomits, in a case where I did not at all expect it, I was afterwards curious to inquire [Page 29] of some Physitians and Chymists, that were of my Acquaintance, whe­ther they had not taken notice, that Antimonium Diaphoreticum, which, as its name imports, is wont to work by sweat or transpiration, would not become vomitive, if 'twere not kept from the Air? To which one Phy­sitian, that was a Learned Man, as­sur'd me, it would, as he had found by particular tryals: And the like answer has been given me by more than one. And I find, that the ex­perienc'd Zwelfer himself does some­where give a caution against letting the Air have access to these Anti­monial Medicines, lest it should ren­der them, as he says it will, in tract of time, not only Emetic, but dispos'd to produce heart-burnings, (as they call them,) faintings, and other bad Symptoms. And I learnt by inquiry from a very Ingenious Doctor of Physic, that, having carefully pre­par'd Antimonium Diaphoreticum, he gave many doses of it whilst it was fresh and kept stopt in a glass (without [Page 30] finding that in any Patient it procur'd so much as one vomit,) but having kept a parcel of the self same Remedy for a pretty while in a glass only co­ver'd loosely with a paper, the Me­dicine, vitiated by the Air, proved emetic (strongly enough) to those, who neither by Constitution, or foulness of stomach, or on any other discernable account, were more than others that had taken it disposed to vomit. By which Observations, and from what I formerly told you of the Salt-peter obtainable from Quick-lime, a Man partial to the Air would be made forward to tell you, that this looks, as if either there were in the Air a substance dispos'd to be assimi­lated by all kinds of bodies, or that the Air is so vast and rich a Rende­vouz of innumerable seminal Cor­puscles and other Analogous parti­cles, that almost any body long ex­pos'd to it may there meet with par­ticles of kin to it, and fit to repair its wrongs and losses, and restore it to its natural Condition. But with­out [Page 31] taking any further notice of this odd surmize, I will proceed to mention two or three other Phaenomena of Na­ture, that seem to favour the Suspi­cion, that there may be Secret Qua­lities in the Air in reference to some bodies.

The ingenious Monsieur de Roche­fort, in the handsom account he gives of the Apple or Fruit of the Tree Iunipa, whose juice is imploy'd by the Indians to black their skins, that they may look the more terrible to their Enemies, observes, that, though the stain, or, as he speaks, the Tin­cture of this Fruit cannot be wash'd out with Soap, yet within nine or ten days it will vanish of it self; which would make one suspect, that there may be in the Air some secret powerful substance, that makes it a Menstruum of more efficacy than Soap it self to obliterate stains. I re­member, I have seen this Fruit, but not whilst it was succulent enough to have a tryal made with it; which I was therefore troubled at, because [Page 32] the Author does not clearly express, whether this disappearing of the tin­cture happens indifferently to the bo­dies it chances to stain, or only is observed on the skins of Men. For, as in the former Case 'twill afford an instance pertinent to our present pur­pose; so in the latter I should suspect, that the vanishing of the tincture may be due not so much to the ope­ration of the Air upon it, as to the sweat and exhalations of a human body, which abounding with vola­tile Salt, may either destroy or carry off with them the colour'd particles they meet with in their passage.

I have sometimes, not altogether without wonder, observ'd the excel­lency of the better sort of Damasco-steel, (for I speak not of all that goes under that name,) in comparison of ordinary steel. And, besides what I have elsewhere taken notice of con­cerning it, there is one Phaenomenon, which though I am not sure it belongs to the latent Qualities of the Air, yet because it may well do so, and I [Page 33] am unwilling it should be lost, I will here tell you, that having inquired of an eminent and experienc'd Arti­ficer, (whom I long since imployed in some difficult Experiments,) about the properties of Damasco-steel, this honest and sober Man averr'd to me, that when he made Instruments of it, and gave them the true temper, which is somewhat differing from that of other Steel, he generally ob­served, that though, when Rasors or other Instruments made of it were newly forged, they would be some­times no whit better, and sometimes less good, than those made of other Steel; yet when they had been kept a year or two or three in the Air, though nothing else were done to im­prove them, they would be found much to surpass other Instruments of the same kind, and what themselves were before; in so much; that some of them have been laid aside at first, as no way answering the great expe­ctation conceived of them, which after two or three years were found [Page 34] to surpass it; of which also I am now making a tryal. I have several times made a substance that consists chiefly of a Metalline body, and is of a tex­ture close enough to lye for many hours undissolv'd in a Corrosive Men­struum; and yet this substance, that was fixt enough to endure the being melted by the Fire without losing its colour, would, when I had pur­posely expos'd it to the Air, be dis­coloured in a very short time, and have its superficial parts turned al­most black.

And this brings into my mind that very pretty Observation, that has been newly made in Italy by an inge­nious Man, who took notice, that, if after the opening of a Vein the blood be kept 'till it be concreted, and have excluded the superficial se­rum, though the lower part be usu­ally of a dark and blackish colour in comparison of the superficial parts, and therefore be counted far more feculent; yet, if the lump or clott of blood be broken, and the internal [Page 35] and dark coloured parts of the blood be expos'd to the Air, it will after a time (for 'tis not said how long) be so wrought on by the contact of the Air, that the superficial part of the blood will appear as florid as the lately mention'd upper part (suppos'd to be, as it were, the flower of the blood,) did seem before. And this Observation I found to hold in the blood of some Beasts, whereon I tryed it, in which I found it to succeed in much fewer minutes, than the Italian Virtuoso's Experiment on Human blood would make me expect.

On the other side I have often pre­par'd a Substance, whose effect ap­pears quite contrary to this. For, though this factitious Concrete, whilst kept to the Fire or very care­fully preserved from the Air, be of a red colour almost like the common opacous Bloodstone of the shops; yet, if I broke it, and left the lumps or fragments of it a little while in the Air, it would in a short time (some­times perhaps not amounting to a [Page 36] quarter of an hour) it would, I say, have its superficial parts turn'd of a very dark colour, very little, and sometimes scarce at all, short of blackness.

A very inquisitive Person of my acquaintance, having occasion to make, by Distillation, a Medicine of his own devising, chanc'd to ob­serve this odd property in it, That at that time of the year, if it were kept stopt, it would be coagulated almost like Oyl of Anniseeds in cold weather; yet, if the stopple were taken out, and so access were for a while given to the Air, it would turn to a liquor, and the vessel being again stopt, it would, though more slow­ly, recoagulate. The hints, that I guess'd might be given by such a Phae­nomenon, making me desirous to know something of it more than barely by Relation, I express'd rather a curiosity than a diffidence about it; and the Maker of it telling me, he thought, he had in a small Vial about a spoonful of this Medicine left in a [Page 37] neighbouring Chamber, I desired his leave to consider it my self, which Request being presently complied with, I found it, when he brought it into the Room which I stayed in, not liquid but consistent, though of but a slight and soft contexture. And having taken out the Cork, and set the Vial in a window, which (if I well remember) was open, though the Season, which was Winter, was cold, yet in a little time that I stayed talking with the Chymist, I found, that the so lately coagulated substance was almost all become fluid. And another time, when the Season was less cold, having occasion to be where the Vial was kept well stopt, and casting my Eyes on it, I perceiv'd the included substance to be coagulated much like Oyl of Anniseeds. And this substance having, as the Maker assur'd me, nothing at all of Mineral in it, nor any Chymical Salt, it con­sisting only of two simple bodies, the one of a vegetable and the other of an animal substance, distill'd toge­ther, [Page 38] I scarce doubt but you will think with me, that these contrary operations of the Air, which seems to have a power in some Circumstan­ces to coagulate such a body, and yet to dissolve and make it fluid when fresh and fresh parts are allow'd access to it, may deserve to be further re­flected on, in reference (among other things) to the opportune operations, the inspired Air may have on the consistence and motion of the circu­lating blood, and to the discharge of the fuliginous recrements to be sepa­rated from the blood in its passage through the Lungs.

There are two other Phaenomena that seem favourable to our Suspicion, That there are Anonymous Substances and Qualities in the Air, which ought not to be altogether praeter­mitted on this occasion; though, because to speak fully of them would require far more time than I can now spare, I shall speak of them but suc­cinctly.

The latter of these two Phaenomena [Page 39] is the growth or appearing produ­ction of Metals or Minerals dug out of the Earth, and expos'd to the Air. And this, though it be the last of the two, I mention first, because it seems expedient, lest it should prove too long an interruption to our Dis­course, to postpone the Observations and annex them to the end of this Paper; only intimating to you now, that the caution I formerly interposed about the Regeneration of Salts in Nitrous and other Earths, may, for greater security, be applied, mutatis mutandis, to that production of Me­talline and Mineral bodies we are spea­king of.

The other of the two Phaenomena, I lately promis'd to mention, is affor­ded me by those various and odd Diseases, that at some times and in some places happen to invade and destroy numbers of Beasts, sometimes of one particular kind, and sometimes of another. Of this we have many instances in the Books of approved Authors; both Physitians and others; [Page 40] and I have my self observ'd some no­table Examples of it. But yet I should not mention it as a ground of Suspicion, that there may be, in some times and places, unknown Ef­fluvia and powers in the Air, but that I distinguish these from those Di­seases of Animals, that proceed, as the Rot in Sheep often does, from the exorbitancy of the Seasons, the immoderateness of Cold, Heat, or any other manifest Quality in the Air. And you will easily perceive, that some of these Examples probably argue, that the Subterraneal parts do sometimes (especially after Earth­quakes or unusual cleavings of the ground) send up into the Air peculiar kinds of venomous Exhalations, that produce new and mortal Diseases in Animals of such a species, and not in those of another, and in this or that particular place, and not elsewhere: Of which we have an eminent In­stance in that odd Plague or Murrain of the year 1514, which Fernelius tells us invaded none but Cats. And [Page 41] even in Animals of the same species, sometimes one sort have been incom­parably more obnoxious to the Plague than another; as Dionysius Halicarna­séus mentions a Plague that attack'd none but Maids; whereas the Pe­stilence that raged in the time of Gen­tilis (a fam'd Physitian) kill'd few Women, and scarce any but lusty Men. And so Boterus mentions a great Plague, that assaulted almost only the younger sort of persons, few past thirty years of age being attack'd by it: Which last Observation has been also made by several later Physitians. To which may be added, what Lear­ned Men of that Faculty have noted at several times concerning Plagues, that particularly invaded those of this or that Nation, though confu­sedly mingled with other People; as Cardan speaks of a Plague at Basil, with which only the Switzers, and not the Italians, French, or Germans, were infected. And Iohannes Uten­hovious takes notice of a cruel Plague at Copenhagen, which, though it raged [Page 42] among the Danes, spared both the English, Dutch, and Germans, though they freely enter'd infected houses, and were not careful to shun the sick. In reciting of which Instances I would not be understood, as if I im­puted these effects meerly to noxious Subterraneal fumes; for I am far from denying, that the peculiar Consti­tutions of Mens Bodies are likely to have a great interest in them: But yet it seems less probable, that the pestilent venom diffused through the Air should owe its enormous and fa­tal efficacy to the excess of the ma­nifest Qualities of the Air, than to the peculiar nature of the pestilential poison sent up into the Air from un­der ground, which when it is by dilution or dissipation enervated, or by its progress past beyond the Air we breath in, or render'd ineffectual by subterraneal or other Corpuscles of a contrary Quality, the Plague, which it, as a con-cause, produced, either quite ceases, or degenerates in­to somewhat else. But I have not [Page 43] time to countenance this Conjecture, much less to consider, whether some of those Diseases, that are wont to be call'd new, which either did begin to appear, or at least to be rise, with­in these two or three Centuries, as the Sudor Anglicus in the fifteenth Century, the Scurvy, and the Morbus Hungaricus, the Lues Moraviae, No­vus Morbus Luneburgensis, and some others, in the last Century of all, may be in part caus'd by the exotic steams this Discourse treats of. But this Consideration I willingly resign to Physitians.

And now, if the two foremen­tioned Suspicions, the one about Sub­terraneal, the other about Sydereal, Effluviums, shall prove to be well grounded, they may lead us to other Suspicions and further thoughts about things of no mean Consequence; three of which I shall venture to make mention of in this place.

  • I. For we may hence be awakened to consider, whether divers changes of Temperature and Constitution in [Page 44] the Air, not only as to manifest Qua­lities, but as to the more latent ones, may not sometimes in part, if not chiefly, be derived from the paucity or plenty, and peculiar nature of one or both of these sorts of Esfluviums. And in particular, we find in the most approved Writers such strange Phae­nomena to have several times hap­pen'd in great Plagues and conta­gious Diseases, fomented and com­municated, nay (as many eminent Physitians believed) begun, by some latent pestiferous, or other malig­nant, Diathesis or Constitution of the Air, as have obliged many of the Learned'st of them to have re­course to the immediate operation of the Angels, or of the Power and Wrath of God himself, or at least to some unaccountable influence of the Stars; none of the Solutions of which difficulties seems preferable to what may be gathered from our Con­jecture; since of Physical Agents of which we know nothing so much, as that they are to us invisible and [Page 45] probably of a heteroclite nature, it need be no great wonder, that the operation should also be abstruse, and the effects uncommon. And on this occasion it may be consider'd, that there are clearer inducements to per­swade us, that another Quality of the Atmosphere, its Gravity, may be alter'd by unseen Effluviums, ascending from the Subterraneous Regions of our Globe; and we have often perceived by the Mercurial Ba­roscope the Weight of the Air to be no­tably increased, when we could not perceive in the Air nor surface of Earth any cause to which we could ascribe so notable a change. And this gives me a rise to add, that I have sometimes allowed my self to doubt, whether even the Sun it self may not now and then alter the Gravity of the Atmosphere otherwise than by its Beams or Heat. And I remember, I desired some Virtuosi of my acquaintance to assist me in the inquiry, whether any of the Spots, that appear about the Sun, may not, [Page 46] upon their sudden dissolution, have some of their discuss'd and dispers'd matter thrown off, as far as to our Atmosphere, and that copiously e­nough to produce some sensible alte­rations in it, at least as to Gravity.
  • II. Another thing, that our two foremention'd Suspicions, if allow'd of, will suggest, is, that it may not seem altogether improbable, that some bodies, we are conversant with, may have a peculiar disposition and fitness to be wrought on by, or to be associated with, some of those exotic Effluvia, that are emitted by un­known bodies lodged under ground, or that proceed from this or that Planet. For what we call Sympa­thies and Antipathies, depending in­deed on the peculiar Textures and other Modifications of the bodies, between whom these friendships and hostilities are said to be exercised, I see not why it should be impossible, that there be a Cognation betwixt a body of a congruous or convenient Texture, (especially as to the shape [Page 47] and size of its Pores,) and the Efflu­viums of any other body, whether Subterraneal or Sydereal. We see, that convex Burning-glasses, by vir­tue of their figure and the disposition of their pores, are fitted to be per­vaded by the beams of Light and to refract them, and thereby to kindle combustible matter; and the same beams of the Sun will impart a lucid­ness to the Bolonian stone. And as for Subterraneal bodies, I elsewhere mention two Minerals,
    See the Experiment in the Discourse of the Determinate Nature of Effluvi­ums.
    which being prepa­red, (as I there inti­mate,) the steams of the one, ascending without adventitious Heat and wan­dering through the Air, will not sensibly work on other bodies; but if they meet with that which we pre­pared, they will immediately have an operation on it, whose effect will be both manifest and lasting.
  • III. I now pass on to the other thing, that the two formerly men­tioned Suspicions may suggest, which [Page 48] is, that if they be granted to be well founded, we may be allow'd to con­sider, whether among the bodies we are acquainted with here below, there may not be found some, that may be Receptacles, if not also Attra­ctives, of the Sydereal, and other exotic Effluviums that rove up and down in our Air.

Some of the Mysterious Writers about the Philosophers-stone, speak great things of the excellency of what they call their Philosophical Magnet, which, they seem to say, attracts and (in their phrase) corporifies the Universal Spirit, or (as some speak) the Spirit of the World. But these things being abstrusities, which the Writers of them profess'd to be writ­ten for, and to be understood only by, the Sons of Art; I, who freely ac­knowledge I cannot clearly appre­hend them, shall leave them in their own worth as I found them, and only, for brevity sake, make use of the receiv'd word of a Magnet, which I may do in my own sense, without [Page 49] avowing the receiv'd Doctrine of Attraction. For by such a Magnet, as I here purpose to speak of, I mean not a body that can properly attract our foreign Effluviums; but such an one, as is fitted to detain and join with them, when by virtue of the various motions, that belong to the Air as a Fluid, they happen'd to accost the Magnet. Which may be illustrated by the known way of ma­king Oyl of Tartar (as the Chymists call it) per Deliquium. For, though the Spagyrists and others suppose, that the fiery Salt draws to it the Aqueous Vapours, yet indeed it does but arrest, and imbody with, such of those that wander through the Air, as chance in their passage to ac­cost it.

And, without receding from the Corpuscularian Principles, we may al­low some of the bodies, we speak of, a greater resemblance to Magnets, than what I have been mentioning. For not only such a Magnet may upon the bare account of Adhesion by [Page 50] Iuxta-position or Contact, detain the Effluviums that would glide along it, but these may be the more firmly arrested by a kind of precipitating faculty, that the Magnet may have in reference to such Effluviums; which, if I had time, I could illu­strate by some Instances; nay I dare not deny it to be possible, but that in some Circumstances of time or place one of our Magnets may, as it were, fetch in such steams as would indeed pass near it, but would not otherwise come to touch it. On which occasion I remember, I have in certain cases been able to make some bodies, not all of them Electri­cal, attract (as they speak) without being excited by rubbing, &c. far less light bodies, than the Effluviums we are speaking of.

But this it may suffice to have glanc'd at, it not being here my pur­pose to meddle with the mystical Theories of the Chymists; but ra­ther to intimate, that, without a­dopting or rejecting them, one may [Page 51] discourse like a Naturalist about Mag­nets of Celestial and other Emana­tions, that appear not to have been consider'd, not to say, thought of, either by the Scholastic, or even the Mechanical, Philosophers.

OF CELESTIAL & AERIAL MAGNETS.

IF now, upon what I have gran­ted in the close of the past Dis­course, you should urge the question further, and press me to declare, Whether, as I think it no impossible thing, that Nature should make, so I think it no unpracti­cable or hopeless thing, that Men should find, or Art should prepare, useful Magnets of the exotic Efflu­viums of the lower region of the Earth, or the upper of the World: It would much distress me to give any other answer, than that I think it extreamly difficult, and not abso­lutely impossible; and therefore I would not discourage any curious or [Page 54] industrious Man from attempting to satisfie himself by Experiments, be­cause even a seemingly slight disco­very in a thing of this nature may be of no small use in the investigation of the nature of the Air, especially in some particular places, and of the Correspondency, which, by the in­tervention of the Air, the superficial part of the Terrestrial Globe may have both with the Subterraneal Re­gions of the Earth, and the Celestial ones of the Universe. Some of the things I have tryed or seen relating to this discovery, I must for certain rea­sons leave here unmentioned, and only advertise you, that several bo­dies, which experience has assur'd us do imbibe or retain something from the Air, as some calcin'd Mi­nerals, some Marchasites, some Salts, as well factitious as natural, &c. may be fit to be often exposed to it, and then weighed again, and farther diligently examined, whether that which makes the increment of weight, be a meer imbibed moisture [Page 55] or also somewhat else, and likewise whether it be separable from the body or not, or however have endowed it with any considerably Quality; and if you chance to meet with a good Magnet, you may then vary Ex­periments with it, by exposing it long to the Air in Regions differing much in Climat, or Soil, or both, by exposing it by day only, or by night, at several Seasons of the Year, in several Temperatures of the Air, at several considerable Aspects of the Stars and Planets, by making it more or less frequently part with what it has gain'd from the Air; and in short, by having regard to variety of Cir­cumstances, which your Curiosity and Sagacity may suggest. For, by thus diversifying the Experiment ma­ny ways, you may perhaps, by one or other of them, make some unex­pected and yet important discovery of what Effluviums the Air, in par­ticular places and times, abounds with, or wants, and perchance too, of some correspondency between the [Page 56] Terrestrial and Etherial Globes of the World.

I shall neither be surpriz'd nor quar­rel with you, if you tell me, that these are extravagant thoughts; but if I had been fortunate in preserving all, that Tryal, Observation, or o­ther productions of some Curiosity, I once had for such Inquiries, pro­cur'd me, you would not perhaps think me so very extravagant. But though I must not here make any fur­ther mention of them, and shall only take notice of one body, namely VITRIOL, whether crude, or un­ripe, and (as Chymists speak) embrio­nated, or Spagyrically prepar'd; yet some Phaenomena of these Vitriolate Substances may for the present, I hope, somewhat moderate your cen­sure for my putting you upon Obser­vations that I fear you your self will judge unpromising, and less favou­rable persons than you would think phantastical. And to let you see by a pregnant Instance, that the Air may not only have a Notable opera­tion [Page 57] upon Vitriol, and that, after a strong fire could work no farther on it, but that this operation was con­siderably diversified by Circumstan­ces; I shall begin what I have to al­ledge, with what the experienc'd Zwelfer occasionally observ'd, and relates to usher in a caution about a Chymical Preparation of Vitriol: For, having inform'd his Reader, that the Colcothar, that is made by a strong Distillation, is not corrosive, he de­nies, that, (to use his own words) ‘statim à Distillatione Sal ex eodem, affu­sâ aquâ, elici queat; sed tum prius, (continues he) ubi aliquandiu aeri ex­positum fuerit; tunc enim sal praebet quandoque candidum, quandoque purpu­reum, aspectu pulcherrimum, quod ali­quando in copia acquisivi, & penes me asservo, quandoque etiam Nitrosum.’

Which Testimony of this candid Spagyrist has much the more weight with me, because I find, what he af­firms of the Saltlesness of newly and strongly calcin'd Vitriol to be very agreeable to some of my Experi­ments [Page 58] about Colcothar of blew (v [...]ne­real) Vitriol; which Salt or Mineral (I mean Vitriol) is so odd a Concrete, that I have thought fit more than once to recommend the making Ex­periments about it to several Curi­ous Persons, that had better oppor­tunity to continue them than I, whose residence was not so fixt. And I remember, that one of these, a Per­son industrious and versed in Chy­mical Operations, gave me this ac­count, that not only he had differing kinds of Salts from Colcothar expos'd to the Air for many months, and robb'd at convenient times of what it had acquir'd, but that in tract of time he found it so alter'd, that he obtain'd from it a pretty quantity of true running Mercury.

And now, to resume and conclude what I was saying about Colcothar, there are two or three things I would propose to be observed by you, or any Virtuoso that would assist me in these tryals about this odd Calcina­tum, (for to call it Terrae damnata, were to injure it.)

[Page 59]The first is, to take notice of [...]ome Circumstances that most Observers would overlook; such as (besides the Nature of the Soil) the Temperature of the Air, the Month of the Year, and the Winds, the weight of the Atmosphere, the Spots of the Sun, if any be, the Moons Age, and her Place in the Zodiack, and the princi­pal Aspects of the Planets, and the other chief Stars. For, though it be a boldness to affirm, that any, or per­haps all of these together, will have any interest in the production of the Salt or other Substance, to be made or disclosed in the Colcothar; yet in things new and exorbitant, it may be sometimes rash and peremptory to deny, even such things as cannot, without rashness, be positively asser­ted; and in our case the small trouble of taking notice of Circumstances will be richly paid by the least disco­very made in things so abstruse and considerable. And as we cannot yet knowingly pronounce, so much as negatively, whether the Libration of [Page 60] the Moon and the Motion of the Sun (and perhaps of some of the other Planets) about their own Centers, and con­sequently their obverting several parts of their bodies to us, may have an operation upon our Atmosphere; so, for ought I know, there may be in those vast internal parts of the Earth, whose thin crust only has been here and there dug into by Men, conside­rable Masses of Matter, that may have periodical Revolutions, or Accensi­ons, or Estuations, or Fermentati­ons, or, in short, some other notable Commotions, whose Effluvia and Effects may have operations, yet un­observed, on the Atmosphere and on some particular bodies expos'd to it; though these periods may be perhaps either altogether irregular, or have some kind of regularity differing from what one would expect. As we see, that the Sea has those grand Intu­mescencies, we call Spring-tides, not every day, nor at any constant day of the month or week, but about the Full and New Moon; and these [Page 61] Spring-tides are most notably heigh­ten'd, not every month, but twice a year, at or about the Vernal and Autumnal Equinoxes; which Obser­vations have not been near so antient and known, as the daily Ebbing and Flowing of the Sea. The Etestans of the Antients I shall not now insist on, nor the Observations that I think I elsewhere mention'd of the Elder Inhabitants of the Caribe-Islands, who, when the Europeans first resor­ted thither, were wont to have Hur­ricanes but once in seven years; af­terwards they were molested with them but once in three years; and of late they are troubled with them almost every year. And a Physitian that lived there told me, that he had scarce ever observed them to come but within the compass of two months joyning to one another. In which Instances, and divers others that may be noted of what changes happen'd to great Quantities of Mat­ter, Nature seems to affect some­thing of periodical, but not in a [Page 62] way that appears to us, regular.

One may add on this occasion that memorable passage related by the Learned Varenius of those Hot Springs in Germany, Varenius. Lib. 1. Geo­graph. Vnivers. Therm [...] omnes forè qu [...] novi­mus fiu [...] cess [...]tione f [...]u­unt exceptis Piperini [...] Germania, &c. that he calls Thermae Peperi­nae, of which he af­firms in more than one place, that they have this pecu­liarity, that they annually begin and cease to flow at certain times; the former about the third day of May, and the latter near the middle of September, at which time they are wont to rest till the following Spring. But though, for ought I know, our Geographers Observation will hold in hot Springs; yet it must not be ex­tended to all, at least, if we admit that which is related by the accurate Iohannes de Laet, Amer. Lib. V. cap. 7. (I suppose out of Xi­menes, or the famous Conquerour of Mexico, Cortes,) who tells us, that in the Mexican Province, ‘Xilotepec, Fons celebratur, qui quatuor continuit [Page 63] annis scaturit, deinde quatuor sequentibu [...] deficit, & rursus ad priorem modum erum­pit, &, quod mirabile, pluviis diebus, parciùs, quum sudum est tempus & ari­dum, copiosiùs, exuberat.’

But this is not a place to enlarge upon the grounds of my suspecting, there may be some periodical Mo­tions and Commotions within the Terrestrial Globe; what has been mention'd being only to invite you to take notice of Circumstances in your Observations of Colcothar, some of which may, with the more shew of probability, be kept expos'd for a long time, because that Bars of Win­dows and other erected Irons I have found to acquire in tract of time from the Effluvia of the Earth a settled Magnetism.

The other main thing I would re­commend, is, that notice be taken not only of the kind of Vitriol, the Colcothar is made of; (for I general­ly used blew Danzig Vitriol) as Mar­tial Vitriol, Hungarian Vitriol, Roman Vitriol, &c. to which I have, for [Page 64] Curiosity, added Vitriol made by our selves of the Solution of the more saline parts of Marchasites in water, without the usual additament of Iron, or Copper; but also, to what degree the calcination is made, and how far the calcin'd Matter is freed from the Salt by water. For these Cir­cumstances, at least in some places, may be of moment, and perhaps may afford us good hints of the Con­stitution of the Atmosphere in parti­cular parts, as well as of the best preparation of Colcothar for detain­ing the exotic Effluviums. And I would the rather have Experiments tryed again in other places with Colcothar not calcin'd to the utmost, nor yet so exquisitly edulcorated, but that some saline particles should be left in it for future increase; because I have more than once purposely tryed in vain, that the Caput Mortuum of blew Vitriol, whereof the Oyl and other parts had been driven off with a violent and lasting fire, would not, when fresh, impart any saltness [Page 65] to the water; nor do I think, that out of some ounces purposely edulco­rated I obtained one grain of Salt. And this saltless Colcothar being ex­pos'd, some by me, and some by a Friend that had conveniency in ano­ther place not far off, to the Air, some for many weeks and some for divers months, we did not find it to have manifestly increased in weight, or to have acquired any sensible salt­ness, which, supposing the Vitriol to have nothing extraordinary, gave me the stronger suspicion of some peculiarity in the Air of that part of London, where the Tryals had been made, at least during those times wherein we made them; because not only former experience, made here in England, had assur'd me, that some Colcothars will gain no despicable accession of weight by being expos'd to the Air; but accidentally complai­ning of my lately mention'd disap­pointment to an ingenious Traveller, that had, in divers Countries, been curious to examine their Vitriols, he [Page 66] assured me, that, though he usually dulcified his Colcothar very well, yet within four or five weeks he found it considerably impregnated by the Air 'twas exposed to.

It remains, that I add one intima­tion more about Vitriol, which is, that I have found it to have so great a correspondency with the Air, that it would not be amiss to try, not only Colcothar of differing Vitriols (whether barely made the common way, or without any Metalline ad­dition to the Vitriol Stones or Ore,) but other Preparations of Vitriol too, such as exposing Vitriol, only cal­cin'd to whiteness by the Sun-beams, or further to an higher colour by a gentle Heat, or throughly calcined, and then impregnated with a little of its own Oyl. For such Vitrio­late Substances as these, the Air may work upon, nay even liquid Prepa­rations of Vitriol may be peculiarly affected by the Air, and thereby per­haps be useful to discover the present constitution, or foretel some approa­ching [Page 67] changes of it. Of the use of which conjecture, namely the pecu­liar action of the Air on some Vitrio­late Liquors, I remember I shew'd some Virtuosi a new Instance in an Ex­periment, whereof this was the Sum:

[I elsewhere mention a Composi­tion that I devis'd, to make with Sublimate, Copper, and Spirit of Salt, a Liquor of a Green exceeding love­ly. But in the description of it I mention'd not (having no need to do it there) a circumstance as odd as the liquor it self was grateful. For the Air has so much interest in the production of this green, that when you have made the Solution of the Copper and Mercury with the Spirit of Salt, that Solution will not be green, nor so much as greenish, as long as you keep it stopt in the bolt-head, or such like glass wherein 'tis made. But if you pour it out into a Vial, which, by not being stopt, leaves it expos'd to the Air, it will after a while sooner or later attain that delightful green that so much endears it to the Behol­ders [Page 68] Eye. This appear'd so odd an Experiment to the Virtuosi, to whom I first related it, that those that could not guess by what means I attain'd it, could scarce believe it. But that troubled not me, who, to satisfie my self not only of the Truth of the Experiment, but that 'twas not so contingent as many others, repeated it several times, and found the So­lution, 'till the Air made it florish, to be of a muddy reddish colour quite differing from green. So that I remember, that having once kept some of the liquor in the same glass-egg, wherein the Solution had been made, it look'd like very dirty water, whilst the other part of the same So­lution, having been expos'd to the Air, emulated the colour of an Eme­rald. In which change 'tis remar­kable, that to clarifie this liquor and give it a transparent greeness, I per­ceiv'd not, that any precipitation of foul matter was made to which the alteration could be ascrib'd; and yet to make it the more probable that this [Page 69] change proceeded not from a subsi­dence made of some opacating mat­ter effected by some days rest, I kept some of the Solution seal'd up in a fine Vial several months, without finding it at the end of that time other than a dark or muddy liquor, which, in short time, it ceas'd to be, when, the Hermetic Seal being broken off, the Air was permitted to work upon it. And this I further observ'd in our various Experiments on this li­quor, that, according to the quality of the matter and other Circumstan­ces, the greeness was not attain'd to but at certain periods of time, now and then disclosing it self within two or three days, and sometimes not be­fore nine or ten.]

With how little Confidence of success Tryals, that have the aimes of these I have been speaking of, are to be attempted, not only consi­deration but experience have made me sensible. But yet I would not discourage Mens Curiosity from ven­turing even upon slight probabilities, [Page 70] where the Nobleness of the Subjects and Scope may make even small attainments very desirable. And 'till tryal have been made on occa­sions of great moment, 'tis not easie to be satisfied, that Men have not been wanting to themselves; which I shall only illustrate by proposing, what, I presume, will not need that I should make an application of it. Those adventurous Navigators, that have made Voyages for Discovery in unknown Seas, when they first discern'd something obscure near the Horizon at a great distance off, have often doubted, whether what they had so imperfect a sight of, were a Cloud, or an Island, or a Mountain: But though sometimes it were more likely to be the former, as that which more frequently occurr'd, than the latter; yet they judg'd it advisable to steer towards it, 'till they had a clearer prospect of it: For if it were a deluding Meteor, they would not however sustain so great a loss in that of a little labour, as, in case it were [Page 71] a Country, they would in the loss of what might prove a rich Disco­very: And if they desisted too soon from their Curiosity, they could not rationally satisfie themselves, whether they slighted a Cloud or neglected a Country.

FINIS.
OBSERVATIONS ABOUT T …

OBSERVATIONS ABOUT THE GROVVTH OF METALS in their ORE Exposed to the AIR.

By the Honourable ROBERT BOYLE, Fellow of the Royal Society.

LONDON, Printed by William Godbid, and are to be Sold by Moses Pitt, at the Angel over against the little North Door of St. Paul's Church. 1674.

OBSERVATIONS OF THE GROVVTH OF METALS.

IT is altogether unnecessary to my present purpose, to examin, whether Metals and Minerals, as if they were a kind of subter­raneal Plants, do properly grow as Vegetables do. For this Inquiry be­longs to another place, but not to this, where the reference made in the 39 th page of the foregoing Paper does not oblige me to speak of the Growth of Metals in any other than a lax and popular sense, in which a Metal may be said to grow, if a portion of [Page 2] Matter being assign'd, wherein as yet Men can find either no Metal, as Gold or Tin, or but such a quantity of it; this being expos'd to the Air, will after a time either afford some Metal where there appear'd none before, or a greater proportion of Metal than it had before.

Observations of this kind requi­ring length of time, as well as resi­dence near places abounding with Minerals, I have little or no oppor­tunity to make any of them my self, at least with the wariness, that to me seems due to Observations that I think not easie to be well made. And therefore I must content my self to set down what I have been able to learn by conversing with Mineralists and Travellers, and to add some par­ticulars that I met with in Authors of good Credit.

OBSERVATIONS ABOUT THE Growth of TIN.

AN ancient Owner of Mines, being asked by me, Whether he could, otherwise than upon the Conjectures of vulgar Tradition, prove, that Minerals grow even after the Veins have been dug? Answer'd affirmatively; and being desired to let me know his proofs, he gave me these that follow.

He told me, that not far from his House there was a Tin-Mine, which the old Diggers affirm'd to have been left off, some said eighty, some an hun­dred & twenty years ago, because they had by their washing and vanning se­parated all the Ore from the rest of the Earth, and yet of late years they [Page 4] found it so richly impregnated with Metalline Particles, that it was wrought over again with very good profit, and preferr'd to some other Mines that were actually wrought, and had never been so robb'd. And when I objected, that probably this might proceed from the laziness and unskilfulness of Workmen in those times, who left in the Earth the Tin that was lately separated, and might then have been so; I was answer'd, that 'twas a known thing in the Country, that in those times the Mine-men were more careful and la­borious to separate the Metalline part from the rest of the Ore, than now they are.

He also affirmed to me, that in his own time some Tenants and Neigh­bours of his (imploy'd by him) ha­ving got all the Ore they could out of a great quantity of stuff, dug out of a Tin-Mine, they laid the re­mains in great heaps expos'd to the Air, and within twenty and thirty years after, found them so richly [Page 5] impregnated, that they wrought them over again with good benefit.

And lastly he assured me, that, in a Work of his own, wherein he had exercis'd his skill and experience, (which is said to be very great) to separate all the particles of the Tin from the Terrestrial substances, that were dug up with it out of the Vein, he caus'd Dams to be made to stop the Earthy Substance, which the Stream washed away from the Ore, giving passage to the water after it had let fall this Substance, which lying in heaps expos'd to the Air, within ten or twelve years, and some­times much less, he examin'd this or that heap, and found it to contain such store of Metalline particles, as invited him to work it again and do it with profit. And yet this Gentle­man was so dexterous at separating the Metalline from the other parts of Tin-Ore, that I could (not without wonder) see what small Corpuscles he would, to satisfie my Curiosity, sever from vast quantities (in propor­tion) [Page 6] of Earthy and other Mineral stuff.

Relations agreeable to these, I re­ceived from another very ingenious Gentleman that was conversant with Tin-Mines, and lived not far from more than one of them.

I was the more solicitous to pro­cure an information about the Growth of this Metal, because the bulk of that, which is us'd in Europe, being found in England, I have met with little or no mention of the Growth of it in Outlandish Writers.

OBSERVATIONS ABOUT THE Growth of LEAD.

AS for the Growth of Lead in the Ore expos'd to the Air, I re­member, I enquir'd about it of a Person of Quality, who had a Patent for di­vers Leaden Mines that were suppos'd to contain Silver, and wrought some of them himself at no small charge, yet not without profit; and, as I remember, he answer'd me, that the Lead-Ore, that had been wrought and laid in heaps, did, in tract of time, grow impregnated with Metal again, and, as experience manifested, be­came worth working a second time. And indeed some Mineralists deliver it as a general Observation, that the Growth and Renascence of Metals is [Page 8] more manifest in Lead than in any other of them. Fessularum mons in Hetruria, says Boccatius Certardus, who delivers it as a most approved Truth, Florentiae Civitati imminens, lapiaes plumbarios habet, qui si excidantur bre­vi temporis spatio novis Incrementis in­staurantur. J. Gerhard. in Decade quae­stionum, pag. m. 22.

Tu subtilius ne quaeras (says Agricola, speaking of the Growth of Mines in general) sed tantummodo refer animum ad cuniculos, & considera, eos adeò in­terdum memoriâ hominum in angustum venisse, ut aliqua sui parte nullum aut admodum difficilem praebeant transitum, cùm eos satis latè agere soleant Fossores, ne transituros impediant. In tales autem angustias sunt adducti propter accretio­nem materiae ex qua lapis est factus.

But whether this increment of Lead is observable in all Mines of that Metal, I was induc'd to doubt by the answer given me by a Gentleman, whose House was seated near several Lead-Mines, and who was himself Owner of one or two, which he yet [Page 9] causes to be wrought: For this Gen­tleman, though a Chymist, assured me, that in the Country where he lives, which is divided by the Sea from that of the Person above-men­tion'd, he never observ'd the Lead-Ore to increase, either out of the Veins or in them; but that in some places, whence Ore had been dug thirty or forty, if not fifty, years be­fore, he perceived not on the sides of the passages, whence the Ore had been dug, that any other had grown in its place, or that the passages, though narrow before, were sensibly straighten'd, much less block'd up.

And indeed, if there were no o­ther Arguments in the cafe, the straightning of the ancient passages in process of time would not con­vince me. For, when I con [...]ider, that the Soils that abound with Me­tals do usually also abound with waters, which are commonly imbi­bed by the neighbouring Earth; and when I consider too, that water is somewhat expanded by being turned [Page 10] into Ice, and that this expansion is made, (as I have often tryed) though slowly, yet with an exceeding great force, by which it often stretches or breaks the Vessels that contain it: When I consider these things, I say, I am apt to suspect, that sometimes the increasing narrowness of the sub­terraneal passages in Mines may pro­ceed from this, that the Soil that in­virons them, if they lye not deep, may have the water, imbibed by them, frozen in sharp Winters. By which glaciation, the moistened portion of the Soil must forcibly endeavour to expand it self, and actually do so in the parts contiguous to the passage, since there it finds no resistance: And though the expansion made in one year or two be but small, and there­fore not observed; yet, in a succes­sion of many Winters, it may by de­grees grow to be very considerable. But this suspicion I suggest not, that I would deny the Growth of Mine­rals, but to recommend this Argu­ment for it to further Consideration. [Page 11] And yet I take this to be a better proof, than what is much relied on by some Writers of Metals, who urge, that in Churches, and other magnificent Buildings, that are Lea­ded over, the Metalline Roofs, in a long tract of years, grow far more ponderous, in so much that often times there is a necessity to remove them, and exchange them for Brass ones. For though this plausible Ar­gument be urged by several Writers, and among them by the Learned Io. Gerhardus, pag. m. 22; yet I fear they proceed upon a Mistake. For ha­ving had some occasion to observe and inquire after this kind of Lead, I soon suspected, that the increment of weight, (which sometimes may indeed be very great) was no clear proof of the real Growth of the Me­tal it self. For in that which I had occasion to consider, the additional weight as well as bulk seem'd to pro­ceed from Acetous or other Saline Corpuscles of the Timber of those Buildings, which by degrees exhaling [Page 14] and corroding that side of the Lead which they fasten'd on, turned i [...] with themselves into a kind of Ce­russe: Which suspicion I shall briefly make probable by noting, 1. That I have found by tryal purposely made, that Woods afford an acid, though not meerly acid, liquor, ca­pable of corroding Lead. 2. That 'tis known, that Lead turned into Cerusse increases notably in weight, some say, (for I had not opportunity to try it) above six or seven in the hundred. 3. That from the Sheets of Lead that have very long cover'd Churches and the like Buildings, there is often obtain'd by scraping a good proportion of white Lead, which I have known much preferr'd by an eminent Artist to common Ce­russe, when a white Pigment was to be employed. And, by the way, Mens finding this Cerusse not on that side of the Lead that is expos'd to the outward Air, (where I scarce ever observed any) but on the inside that regards the Timber and other woodes [Page 13] work, may disabuse those that fan­cied this Cerusse to be a part of the Lead calcin'd by the Beams of the Sun, that strike immediately upon the Metal. And if to this it be added, that by Distillation and otherwise I have found cause to suspect, that Alabaster and White Marble may emit Spirituous parts that will invade Lead; it may be doubted, whether what Galen relates of the great Intu­mescence of Leaden bands or faste­nings, wherewith the Feet of Statues were fasten'd (to their Pedestals,) be a sure Argument of the real Growth of that Metal in the Air.

But I begin to digress, and see­mingly to the prejudice of the parti­cular Scope of this Paper; but yet not to that of one of the main Scopes of all my Physical Writings, the Dis­quisition and Advancement of Truth.

OBSERVATIONS ABOUT THE Growth of IRON.

I Did not find in one of our chief Mines of Iron, that there was any notice taken of the Growth of that Metal; but in another place or two, some that deal in Iron-Ore, infor­med me, that they believe it grows, and may be regenerated; and upon that account one of them set up a Work, contiguous to some Land of mine, to melt over again the re­mainder of Ore that had been already wrought (at a great distance from that place) and had for some Ages lain in heaps exposed to the free Air; but with what success this chargeable Attempt has been made, I am not yet informed.

[Page 15]But of the Growth of Iron in the Island of Ilva or Elva, in the Tyr­rhene Sea, not far from the Coast of Tuscany, not only ancient Authors, as Pliny and Strabo, take special notice, but modern Mineralists of very good credit, as Falopius and Caesalpinus, par­ticularly attest the same thing; of whom the latter speaks thus: Lib. III. Cap. 6. Vena ferri copio­sissima est in Italia; ob eam nobilitata, Ilva; Tyrreni Maris Insula, incredibili copiâ etiam nostris temporibus eam gig­nens: Nam terra; quae eruitur dum vena effoditur, tota procedente temporè in venam convertitur.

And the experienc'd Agricola gives us the like account of a place in his Country, Germany, Agric. de Vet. & Nov. Met. Lib. II. Cap. 15. In Lygiis, says he, ad Sagam oppidum in pratis eruitur ferrum, fossis ad altitudinem bipedaneam actis. Id decennio renatum denuò fodi­tur, non aliter ac Ilvaeferrum.

The Learned Iohan. Gerhardus, out of a Book which he calls Conciones Metallica; I suppose he means the [Page 16] High-Dutch Sermons of Mathesius, (whose Language I understand not) has this notable passage to our present purpose: J. Gerhard. Pro­fessor Tubingen­sis, Decad. Quaest. Physico chymica­rum, pag. m. 18. ‘Relatum mihi est a metallico fossore, ad Ferrarias, quae non longè Ambergâ distant, terram inanem cum ferri Minera erutam, quam vocant den Gummer, mixtam cum recrementis ferri, quae ap­pellater der Sinder, congestam in cu­mulos, instar magni cujusdam valli, soli­bus pluviisque exponi, & decimo quinto anno denuò excoqui, eliquarique ferrum tantae tenacitatis, ut sola laminae inde procudantur.’

OBSERVATIONS ABOUT THE Growth of SILVER.

OF the Growth, as is supposed, of Silver in the form of Trees or Grass or other Vegetables, I have met with some Instances among Mi­neralists, and I have elswhere men­tion'd, that an Acquaintance of mine shew'd me a Stone, wherein he af­firmed the Silver, I saw in it, to have increased since he had it. But for certain Reasons, none of these Relations seem to me very proper to my present purpose; in order to which I shall therefore set down only one Instance, which I lately met with in a French Collection of Voy­ages, publish'd by a Person of great Curiosity and Industry, (from whose [Page 18] Civility I receiv'd the Book.) For there, in an account given by a Gen­tleman of his Country of a late Voy­age he made to Peru, wherein he visited the famous Silver-Mines of Potosi, I found a passage which speaks to this sense: Le meilleur Argent, &c. i.e. Voyage du Sicur au Peru, pag. 15. The best Silver in all the Indies and the purest is that of the Mines of Potosi; the chief have been found in the Mountain of Aranzasse: And, (some Lines being interpos'd) 'tis added, that they draw this Metal even from the Mineral Earths that were in times past thrown aside, when the ground was open, and the Groves and Shafts that are in the Mountains were made; it having been observ'd that in these recrements Metal had been formed afresh since those times, which sufficiently shews the propensity of the Soil to the pro­duction of this Metal; yet 'tis true, that these impregnated Earths yield not so much as the ordinary Ore which is found in Veins betwixt the Rocks.

OBSERVATIONS ABOUT THE Growth of GOLD.

AS for the Growth of Gold, the Enquiries I have yet made a­mong Travellers give me no great satisfaction about it, and though I have spoken with several that have been at the Coast of Guiny, and in Congo, and other Parts of Afric, where much Gold is to be had; yet I could not learn by them, that they, or any Acquaintance of theirs among the Natives, had seen any Mines or Veins of Gold, (which yet divers Authors affirm to be found in more than one Kingdom in Ethiopia, and in some other African Countries.) And having afterwards met with a Lear­ned Traveller, that had carefully vi­sited [Page 20] the famous Gold-Mine of Crem­nitz in Hungary, he answer'd me, That he did not learn from the Mi­ners, whether or no the Ores of Gold &c. did really grow or were rege­nerated in tract of time, by being expos'd to the Air, or upon any other account; but the Grand Over [...]eer, who was Lord of part of the Soil, told him, that he thought the whole Mountain to abound with particles of Gold, and therefore was wont, when the Diggers had almost exhausted the Vein, to cast in store of Earth, and dig up other neighbouring pla­ces, which, being kept there as in a Conservatory, would afterwards af­ford Gold, as the Mine did before.

And, if a late German Professor of Physic do not misinform us, his Coun­try affords us an eminent Instance of the Growth or Regeneration of Gold. Nam Corbachi, Johan. Gerhar­dus in Decade Quastion [...] pag. [...] 19. says he, quae est Civitas westpha [...]iae sub ditione Comitis de I­senborg & Waldeck, Au­ [...]um excoquitur ex cumulis congestis, ita [Page 21] ut [...]ngulis quadrienni [...]s iterum elabore­tur cumulus unus, semper se restaurante natur [...], &c.

POSTSCRIPT.

SInce the setting down of the fore­going Observations, I casually met with a curious Book of Travels, lately made by the very Ingenious Dr. Edward Brown, and finding in pag. 100. a couple of Relations, that seem pertinently referable, the one, to a passage above-cited out of Agri­cola, in the Notes about the Growth of Lead, and the other to the present Title about the) Growth of Gold; I thought fit to annex them in the Learned Authors own words, viz.

1. Some passages in this Mine cut through the Rock, and long [...]isus'd, have grown up again: And I observed the sides of some, which had been formerly wide enough, to carry their Ore through, [Page 22] to approach each other, so as we passed with difficulty. This happens most in moist places; the passages unite n [...]t from the top to the bottom, but from one side to another.

2. The common yellow Earth of the Country near Cremnitz, especially of the Hills towards the West, although not esteem'd Ore, affords some Gold: And in one place, I saw a great part of an Hill digg'd away, which hath been cast into the Works, washed and wrought in the same manner as pounded Ore, with consi­derable profit.

THe foregoing Observations a­bout the Growth of Gold and other Metals are not all that I might, perhaps without being blamed for it, have referr'd to that Title. But all my Papers, wherein other Observations of this kind were set down, are not now at hand, and divers other In­stances, that I have met with among [Page 23] Writers of the Growth of Metals, (taking that expression in the sense I formerly declared) do not seem to me so pertinent in this place, because the improving Ores were not expos'd, nor perchance accessible, to the Air. And even as to the Instances that I have now mention'd, 'till severer Observations have been made, to de­termin whether it be partly the con­tact or the operation of the Air, or some internal disposition, analogous to a Metalline Seed or Ferment, that causes this Metalline Increment, I dare not be positive; though I thought the Interest of the Air in this Effect might make it pardonable, to add on this occasion to the History of Na­ture some particulars, of which the Cause conjecturally proposed may be probable enough to countenance a Suspicion, 'till further Experience have more clearly instructed us.

To what has been said of the Growth of Metals in the Air, I might add some Instances of the [Page 24] Growth of Fossile Salts, and of some other Minerals: But, besides that these belong to the Paper about the Saltnesses of the Air; what has been already said may suffice for the pre­sent occasion.

POSTSCRIPT.

AFter what I writ in the 23 th page of the foregoing Disoourse, ha­ving an opportunity to look again up­on the Marchasite there mention'd to have been Hermetically seal'd up af­ter its surface had been freed from the grains of Vitriolate Salt that adher'd to it, I perceiv'd, that, notwithstan­ding the Glass had been so closely stopp'd, yet there plainly appear'd from the outside of the mass some grains of an Efflorescence, whose colour, between blew and green, ar­gued it to be of a Vitriolate nature. If this be seconded with other trials [Page 25] made with the like success, it may suggest new thoughts about the Growth of Metals and Minerals, espe­cially with reference to the Air.

FINIS.
SOME ADDITIONAL EXPE …

SOME ADDITIONAL EXPERIMENTS Relating to the SUSPICIONS ABOUT THE HIDDEN QUALITIES of the AIR.

By the Honourable ROBERT BOYLE, Fellow of the Royal Society.

LONDON, Printed by William Godbid, and are to be Sold by Moses Pitt, at the Angel over against the little North Door of St. Paul's Church. 1674.

SOME ADDITIONAL EXPERIMENTS Relating to the SUSPICIONS ABOUT THE Hidden Qualities of the AIR.

THe ESSAY about Suspicions of some hidden Qualities of the Air, having been de­tain'd somewhat long at the Press, that it might come abroad accompanied with the other Tracts design'd to attend i [...], whilst I was [Page 2] rumaging among several Papers to look for some other things, I met now and then with an Experiment or Ob­servation, that seem'd to relate to some of the things deliver'd in that Tract; and though they be in themselves of no great moment, I am content to annex them to the rest, because, as in that company they may signifie somewhat, so I am unwilling that any matter of fact, relating to such a Subject, should perish to save the labour of transcribing.

EXPER. I.

Having occasion to dulcifie some Calx of Dantzig-Vitriol, from which the Oil had been a good while before distill'd; water was put upon two large portions of it, that the liqour might be impregnated with the Vitri­olate particles remaining in the Calx; the water put upon one of these por­tions was, soon after it was suffi­ciently [Page 3] impregnated, filtrated and gently abstracted, by which means it afforded many drams of a kind of Salt of Vitriol that seem'd to differ very little from the Vitriol that had been calcin'd: But the water that was put upon the other portion of cal­cin'd Vitriol, was in a wide-mouth'd vessel left in the Air for a month or six weeks; after which time, when it came to be abstracted after the manner formerly recited, it afforded many drams of a Salt that did not then, nor long after, look at all like common Vitriol, or like the other, but shot white almost like Salt-petre, or some other untincted Salt. Whe­ther this Experiment will constantly succeed, and at other Seasons of the Year than that 'twas made in, which was Summer, I had not the oppor­tunity to make a full trial, though I endeavour'd it. But that the Air may have a great stroke in varying the Salts obtainable from cal [...]in'd Vi­triol, seem'd the more probable, be­cause [Page 4] we had some Colcothar that had lain many months, if not some years, in the Air, but in a place shelter'd from the Rain; and having caus'd a lixivium to be made of it, to try what sort or plenty of Saline par­ticles it would yield, we found, when the superfluous moisture was exhaled, that they began to shoot into Salt far more white than Vitriol, and very differing from it in its figure and way of Concretion.

EXPER. II.

We took Colcothar of Venereal Vitriol carefully dulcified, and lea­ving it in my Study in the Month of Ianuary and Fe­bruary, This was made at Oxford. by weighing it carefully before an ounce of it was expos'd to the Air, and after it had continued there some weeks, we found it to have increas'd in weight four grains and about a quarter, be­sides [Page 5] some little dust that stuck to the Glass.

This sight Experiment is here mention'd, that, being compar'd with the next ensuing Trial, it may appear, that the difference of Airs, Seasons, Calces of Vitriol, or other Circum­stances, may produce a notable dispa­rity in the Increment of weight, the exposed Bodies gain in the Air.

EXPER. III.

We put eight ounces of Outlandish Vitriol, calcin'd to a deep redness, into a somewhat broad and flat Metal­line vessel, and set it by upon a shelf, in a Study that was seldom frequen­ted; and at the same time, that we might observe what increment would be gain'd by exposing to the Air a larger superficies of the powder in re­ference to the bulk, we put into another Metalline vessel, smaller than the other, only two ounces of Col­cothar, [Page 6] and set it on the same shelf with the other, this was done at the Vernal Equinox, (the Twelfth of March;) on the twenty fifth of Iune we weigh'd these powders again, and found the eight ounces to have gained one dram and seventeen grains; but the two ounces had ac­quired the same weight within a grain: Then putting them back into their former vessels, we left them in the same place as formerly, 'till the twenty fourth of August; when we found cause to suppose, that the grea­ter parcel of Colcothar had met with some mischance, either by Mice or otherwise; but the lesser parcel weigh'd Twenty six grains heavier than it did in Iune, amounting now to two ounces, one dram, forty two grains, having increased, in less than six months, above an hundred grains, and consequently above a tenth part of its first weight.

No Trial was made to discover what this acquir'd Substance may [Page 7] be, that we might not disturb the intended prosecution of the Experi­ment.

EXPER. IV.

Because in most of the Experi­ments of Substances expos'd to be im­pregnated by the Air, or detain its Saline or other exotic particles, we employed Bodies prepar'd and much alter'd by the previous operation of the Fire; we thought fit to make some Trials with Bodies unchanged by the Fire, and to this purpose we took a Marchasite, which was part­ly of a shining and partly of a darkish colour, and which seem'd well dis­pos'd to afford Vitriol; of this we took several smaller Lumps, that a­mounted to two ounces; these were kept in a room, where they were freely accessible to the Air, which, by reason that the House, that was seated in the Country, stood high, [Page 8] was esteemed to be very pure. After the Marchasites had been kept in this room somewhat less than seven weeks, we weigh'd them again in the same Ballance, and found the two ounces to have gained above twelve grains in weight.

EXPER. V.

The Experiment us'd at the latter end of our Paper, about Celestial and Aerial Magnets, seeming to some Vixtuess very strange, and the way that I employ'd in making that Li­quor, that turns green in the Air, being somewhat troublesome, I re­member I thought fit to try upon the same ground a way of producing the same Phaenomenon more easie and more expeditious. And though per­hap [...] this way will not succeed so con­stantly, nor always so well as the other, yet for its easiness and cheapness it will not probably be unwelcome [Page 9] to those that are desirous to see the odd Phaenomenon.

We took then, more than once, filings of clean crude Copper, and having put on them a convenient quantity of good Spirit of Salt, we suffer'd the Menstruum in Heat (which need not be very great) to work up­on the Metal, which it usually does slowly, and not like Aqua-fortis: When the Liquor had by this ope­ration acquir'd a thick and muddy colour, we decanted it into a clean Glass with a wide mouth, which be­ing left for a competent time in the open Air, the exposed Liquor came to be of a fair green, though it did not appear that any thing was pre­cipitated at the bottom, to make it clear.

EXPER. VI.

Perhaps it may not be impertinent to add, that I once or twice observ'd the fumes of a sharp Liquor to work more quickly or manifestly on a cer­tain Metal sustained in the Air, than did the Menstruum it self that emitted those fumes on those parts of the Metal that it cover'd: And this brings into my mind, that, asking divers Questions of a Chymist that had been in Hungary and other parts, purposely to see the Mines; he an­swer'd me, among other things, that; as to the Ladders and other wooden work imployed in one or more of the deep Hungarian Mines, those that were in the upper part of the Groves any thing near the exter­nal Air, would by the fretting Ex­halations be render'd unserviceable, in not many months, whereas those Ladders and pieces of Timber, &c. that were imployed in the lower part [Page 11] of the Mine, would hold good for two or three times as long.

EXPER. VII.

We took about the bigness of a Nutmeg of a certain soft but con­sistent Body, that we had caus'd to be Chymically prepared, and which in the free Air would continually emit a thick smoak: This being put into a Vial, and placed in a middle sized Receiver in our Engin, conti­nued for some time to afford mani­fest fumes, whilst the exhaustion was making; 'till at length, the Air ha­ving been more and more pump'd out, the visible ascension of fumes out of the Vial quite ceas'd, and the matter having remain'd some time in this state, the smoaking substance was so alter'd, that it would not emit fumes, not only when the Air was let into the Receiver, but not in a pretty while after the Vial was taken [Page 12] out of it, 'till it had been removed to the window, where the Wind blowing-in fresh and fresh Air, it be­gan to smoak as formerly.

The other Phaenomena of this Expe­riment belong not to this place; but there are two, which will not be impertinent here, and the latter of them may deserve a serious Re­flection.

The first of them was, that the Substance hitherto mention'd had been kept in a large Glass, where­into it had been distill'd at least five or six weeks, and yet would smoak very plentifully upon the contact of the Air, and be kept from smoaking, though the Chymical Receiver were stopp'd but with a piece of paper.

The second was, that, when the Vial was put unstopp'd in the Re­ceiver, and the Receiver close luted on, though no exhaustion were made, yet the white fumes did very quickly cease to ascend into the Re­ceiver, as if this Smoak participated [Page 13] of the nature of Flame, and pre­sently glutted the Air, or otherwise made it unfit (and yet without dimi­nution of its gravity) to raise the Bo­dy that should ascend.

FINIS.
ANIMADVERSIONS UPON …

ANIMADVERSIONS UPON M R. HOBBES'S PROBLEMATA DE VACUO.

By the Honourable ROBERT BOYLE, Fellow of the Royal Society.

LONDON, Printed by William Godbid, and are to be Sold by Moses Pitt, at the Angel over against the little North Door of St. Paul's Church. 1674.

PREFACE.

UPON the coming abroad of Mr. Hobbes's Problemata Physica, finding them in the hands of an Ingenious Person, that intended to write a Censure of them, which several Employments private and publick have, it seems; hinder'd him to do; I began, as is usual on such occasions, to turn over the leaves of the Book, to see what particular things it treated of. This I had not long done before I found, by ob­vious passages in the third Chapter, or Dialogue, as well as by the Title, which was Problemata de Vacuo, that I was particularly concern'd in it; upon which I desired the Possessor of the Book, who readily consented, to leave me to examin that Dialogue, on which condition I would leave him to deal with all the rest of the Book. Nor did I look upon the Re­flections I meant to make as repugnant [Page] to the Resolutions I had taken against wri­ting Books of Controversie, since the Ex­plications, Mr. Hobbes gave of his Pro­blems, seem'd to contain but some Varia­tions of, or an Appendix to, his Tract De Natura Aeris, which, being one of the two first pieces that were published against what I had written, was one of those that I had expresly reserv'd my self the liberty to answer. But the Animad­versions I first made upon Mr. Hobbes's Problems De Vacuo, having been casually mislaid e're they were finished; before I had occasion to resume my task, there past time enough to let me perceive, that his Doctrine, which 'twill easily be thought that the Vacuists disapproved, was not much relished by most of the Ple­nists themselves, the modernest Peripa­teticks and the Cartesians; each of them maintaining the Fullness of the World, upon their own grounds, which are differing enough from those of our Author, the natural Indisposition I have to Pole­mical Discourses, easily perswaded me to let alone a Controversie, that did not appear needful: And I had still persisted [Page] in my silence, if Mr. Hobbes had not as 'twere summon'd me to break it by publishing again his Explications, which in my Examen of his Dialogue De Na­tura Aeris I had shewn to be erroneous.

And I did not grow at all more satisfied, to find him so constant as well as stiff an Adversary to interspers'd Vacuities, by comparing what he maintains in his Dia­logue De Vacuo, with some things that he teaches, especially concerning God, the Cause of Motion, and the Imperviousness of Glass, in some other of his Writings that are published in the same Volume with it. For since he asserts that there is a God, and owns Him to be the Creator of the World; and since on the other side the Penetration of Dimensions is confessed to be impossible, and he denies that there is any Vacuum in the Universe; it seems difficult to conceive, how in a World that is already perfectly full of Bodie, a Cor­poreal Deity, such as he maintains in his Append. ad Leviath. cap. 3, can have that access even to the minute parts of the Mundane Matter, that seems requi­site to the Attributes and Operations that [Page] belong to the Deity, in reference to the World. But I leave Divines to con­sider what Influence the conjunction of Mr. Hobbes's two Opinions, the Corpo­reity of the Deity, and the perfect Ple­nitude of the World, may have on Theo­logy. And perhaps I should not in a Phy­sical Discourse have taken any notice of the proposed Difficulty, but that, to pre­vent an Imputation on the Study of Na­tures Works, (as if it taught us rather to degrade than admire their Author,) it seem'd not amiss to hint ( in transitu) that Mr. Hobbes's gross Conception of a Corporeal God, is not only unwarranted by sound Philosophy, but ill befriended even by his own.

My Adversary having propos'd his Pro­blems by way of Dialogue between A. and B; `twill not, I presume, be wonder'd at, that I have given the same form to my Animadversions; which come forth no earlier, because I had divers other Treatises, that I was more concern'd for, to publish before them.

But because it will probably be deman­ded, why on a Tract that is but short, [Page] my Animadversions should take up so much room? It will be requisite, that I here give an account of the bulk of this Treatise.

And first, having found that there was not any one Problem, in whose Ex­plication, as propos'd by Mr. Hobbes, I saw cause to acquiesce, I was induc'd for the Readers ease, and that I might be sure to do my Adversary no wrong, to tran­scribe his whole Dialogue, bating some few Transitions, and other Clauses not needful to be transferr'd hither.

Next, I was not willing to imitate Mr. Hobbes, Credo, De Nat. Aeris, p. 13. (says Mr. Hobbes in his Dialo­gus Physi­cus:) Nam motus hic Restitutionis, Hobbii est, & ab illo primo & solo explicatus in Lib. de Corpore, cap. 21. Art. 1. Sine qua Hypothesi, quantus­cunque labor, ars, sumptus, ad rerum Na­turali [...] invisibiles cau­sas inveniendas adhi­beatur, frustra erit. And speaking of the Gentle­men (to whom it were not here proper for me to give Epith [...]tes) that us'd to meet at Gresham-College, and are known by the Name of the Royal Society, he thus treats them and their way of Inquiring into Nature: Conveniant, studia conserant, Expe­rimenta faciant quan­tum volunt, nisi & Principiis utantur me­is, nihil preficient. A. Fateris ergo ni­hil hactenus à Collegis tuis promotam esse sci­entium Causarum Na­turalium, nisi quod U­nus eorum Machinam [...]nvenerit, quâ motus excitari Aeris possit ta­lis, ut partes Sphaerae simul undiquaque ten­dant ad Centrum, & ut Hypotheses Hobbia­nae, antè quidem satis probabiles, hinc red­dantur probabiliores. B. Nec fateri pu­det; nam est aliquid prodire tenus, si non datur ultra. A. Quid tenus? quorsum autem tantus apparatus & sumptus Machinarum factu dif­ficilium, ut eatenus tan­tum prodiretis quan­tum ante prodierat Hobbius? Cur n [...]n in­de potiùs incepistis ubi ille defiit? Cur Prin­cipiis ab illo positis non estis usi? Cum­que Aristoteles rectè dixit, ignorato mo­tu ignorari Naturam, &c. — Ad Causas autem, propter quas proficere ne paululum quidem potu [...]stis, nec poteri­tis, accedunt etiam a­liae, ut odium Hobbii, &c. who recites in the Dialogue we are considering the same Experiments that he had already mentio­ned in his Tract De Natura Aeris, with­out adding as his own (that I remember) any new one to them. But my unwillingness to tire the Reader with [Page] bare Repetitions of the Arguments I employ'd in my Examen of that Tract, invited me to endeavour to make him some amends for the exercise of his pa­tience by inserting, as occasion was offer'd, five or six new Expe­riments, that will not perhaps be so easily made by every Reader that will be able (now that I have perspicu­ously propos'd them) to understand them.

And lastly, since Mr. Hobbes has not been content to mag­nifie [...]mself and his way of treating of Physical matters, but has been pleas'd to speak very slighting­ly of Experimentarian Philosophers (as he [Page] stiles them) in gene­ral, and, which is worse, to disparage the making of elaborate Experiments; I judg'd the thing, he seem'd to aim at, so prejudi­cial to true and use­ful Philosophy, that I thought, it might do some service to the less knowing, and less wary, sort of Readers, if I tryed to make his own Explications ener­vate his Authority, and by a somewhat particular Examen of the Solutions he has given of the Problems I am concern'd in, shew, that 'tis much more easie to un­dervalue a frequent recourse to Experi­ments, than truly to explicate the Phae­nomena of Nature without them. And since our Author, speaking of his Pro­blemata Physica, (which is but a small Book) scruples not to tell His Majesty, to whom he dedicates them, that he has therein comprised (to speak in his own terms) the greatest and most probable [Page] part of his Physical Meditations; and since by the alterations, he has made in what he formerly writ about the Phaeno­mena of my Engine, he seems to have design'd to give it a more advantageous form: I conceive, that by these selected Solutions of his, one may, without doing him the least injustice, make an estimate of his way of discoursing about Natural things. And though I would not interess the credit of Experimentarian Philoso­phers in no considerabler a Paper than this; yet if Mr. Hobbes's Explications and mine be attentively compared, it will not, I hope, by them be found, that the way of Philosophising he employs, is much to be preferr'd before that which he under­values.

ANIMADVERSIONS VPON M R. HOBBES'S Problemata de VACUO.

A.

MAy one, without too bold an inquisitive­ness, ask, what Book you are reading so at­tentively?

B.

You will easily believe you may, when I shall have answer'd you, that 'twas Mr. Hobbes's lately publish'd Tract of Physical Problems, which I was perusing.

A.

What progress have you made in it?

B.

I was finishing the third Dia­logue or Chapter when you came in, [Page 2] and finding my self, though not na­med, yet particularly concern'd, I was perusing it with that attention which it seems you took notice of.

A.

Divers of your Experiments are so expresly mention'd there, that one need not be skill'd in decyphering to perceive that you are interessed in that Chapter, and therefore seeing you have heedfully read it over, pray give me leave to ask your Judgment, both of Mr. Hobbes's Opinion, and his Reasonings about Vacuum.

B.

Concerning his Opinion, I am sorry I cannot now satisfie your Cu­riosity, having long since taken, and ever since kept, a Resolution to de­cline, at least until a time that is not yet come, the declaring my self ei­ther for or against the Plenists. But as to the other part of your Question, which is about Mr. Hobbes's Argu­ments for the absolute Plenitude of the World, I shall not scruple readily to answer, that his Ratiocinations seem to me far short of that cogency, which the noise he would make in [Page 3] the world, and the way wherein he treats both ancient and modern Philo­sophers that dissent from him, may warrant us to expect.

A.

You will allow me the free­dom to tell you, That, to convince me, that your resentment [...] his ex­plicating divers of the Phaenomena of your Pneumatic Engine ot [...]erwise than you have been wont to do, (and perhaps in terms that might well have been more civil,) has h [...] share in dictating this Judgment of yours; the best way will be, that entering for a while into the party of the Vacuists you answer the Arguments he alledges in this Chapter to confute them.

B.

Having always, as you know, forborn to declare my self either way in this Controversie, I shall not tye my self strictly to the Principles and Notions of the Vacuists, nor, though but for a while, oppose my self to those of the Plenists: But so far I shall com­ply with your Commands, as either upon the Doctrine of the Vacuists, or upon other grounds, to consider, whe­ther [Page 4] this Dialogue of Mr. Hobbes have cogently proved his, and the Schools, Assertion, Non dari Vacuum; and whe­ther he has rightly explain'd some Phaenomena of Nature which he un­dertakes to give an account of, and e­specially some produced in our Engin, whereof he takes upon him to render the genuine Causes. And this last in­quiry is that which I chiefly design.

A.

By this I perceive, that if you can make our your own Explications of your Adversaries Problems de Va­cuo, and shew them to be preferable to his, you will think you have done your work, and that 'tis but your secondary scope to shew, that in Mr. Hobbes his way of solving them, he gives the Vacuists an advantage against Him, though not against the Plenists in general.

B.

You do not mistake my mean­ing, and therefore without any fur­ther Preamble, let us now proceed to the particular Phaenomena consider'd by Mr. Hobbes; the first of which is an Experiment proposed by me in the [Page 5] one and thirtieth of the Physico-Me­chanical Experiments concerning the Adhesion of two flat and polish'd Marbles, which I endeavour'd to solve by the pressure of the Air. And this Experiment Mr. Hobbes thinks so con­vincing an one to prove the Plenitude of the World, that, though he tells us he has many cogent Arguments to make it out, yet he mentions but this one, because that, he says, suffices.

A.

The Confidence he thereby expresses of the great force of this Argument does the less move me, because, I remember, that formerly in his Elements of Philosophy he thought it sufficient to employ one Argument to evince the Plenitude of the World, and for that one he pitch'd upon the Vulgar Experiment of a Gardeners Watering-Pot: But, whether he were wrought upon by the Objections made to his Inference from that Phaenome­non in your Examen of his Dialogue De Natura Aeris, or by some other Considerations, I will not pretend to divine. But I plainly perceive, he [Page 6] now prefers the Experiment of the cohering Marbles.

B.

Of which it will not be amiss, though the passage be somewhat long; to read you his whole Discourse out of the Book I have in my hand.

A.

'Tis fit that you, who for my sake are content to take the pains of answering what he says, should be eased of the trouble of reading it, which I will therefore, with your leave, take upon me. His Discourse then about the Marbles is this:

A.

Ad probandam Universi Pleni­tudinem, nullum nostin Argumentum cogens?

B.

Imò multa: Unùm autem sufficit ex eo sumptum, Quod duo corpora plana, si se mutuò secundùm amborum planitiem communem tangant, non facile in in­stante divelli possunt; successivè verò facillimè. Non dico, impossibile esse duo durissima Marmora ita cohaerentia divel­lere, sed difficile; & vim postulare tan­tam, quanta sufficit ad duritiem lapidis superandam. Siquidem verò majore vi ad separationem opus sit quàm illae, quâ [Page 7] moventur separata, id signum est non dari Vacuum.

A.

Assertiones illae demonstratione indigent. Primò autem ostende, quomo­do ex duorum durissimorum corporum, conjunctorum ad superficies exquisite lae­ves, diremptione difficili, sequatur Ple­nitudo Mundi?

B.

Si duo plana, dura, polita Cor­pora (ut Marmora) collocentur unum su­pra alterum, ita ut eorum superficies se mutuò per omnia puncta exactè, quan­tum fieri potest, contingant, illa sine magna difficultate ita divelli non pos­sunt, ut eodem instante per omnia pun­cta dirimantur. Veruntamen Marmora eadem, si communis eorum superficies ad Horizontem erigatur, aut non valde in­clinetur, alterum ab altero facillimè (ut scis) etiam solo pondere dilabentur. Nonne causa hujus rei haec est, Quod labenti Marmori succedit Aer, & reli­ctum locum semper implet?

A.

Certissimé. Quid ergo?

B.

Quando verò eadem uno instante divellere conaris, nonne multo major vis adhibenda est; Quam ob causam?

A.
[Page 8]

Ego, & mecum (puto) omnes cau­sam statuunt, Quod spatium totum inter duo illa Marmora divulsa, simul uno in­stante implere Aer non potest, quanta­cunque celeritate fiat divulsio.

B.

An qui spatia in Aere dari va­cua contendunt, in illo Aere solo dari negant qui Marmora illa conjuncta cir­cumdat?

A.

Minimè, sed ubique interspersa.

B.

Dum ergo illi, qui Marmor unum ab altero revellentes Aerem comprimunt, & per consequens Vacuum exprimunt, Vacuum faciunt locum per revulsionem relictum; nulla ergo separationis erit difficultas, saltem non major quàm est difficultas corpora eadem movendi in Aere postquam separata fuerint. Ita­que quoniam, concesso Vacuo, difficultas Marmora illa dirimendi nulla est, se­quitur per difficultatis experientiam, nullum esse Vacuum.

A.

Recte quidem illud infers. Mun­di autem Plenitudine suppos [...]ta, quomodo demonstrabis possibile omnino esse ut di­vellantur?

B.

Cogita primo Corpus aliquod du­ctile, [Page 9] nec nimis durum, ut ceram, in duas partes distrahi, quae tamen partes [...]on minus exacte in communi plano se mutuo tangunt quàm laevissima Mar­mora. Iaem quo pacto distrahatur cera, consideremus. Nonne perpetuo attenua­tur donec in filum evadat tenuissimum, & omni dato crasso tenuius, & sic tan­dem divellitur? Eodem modo etiam du­rissima columnae in duas partes distra­hetur, si vim tantam adhibeas, quanta sufficit ad resistentiam duritiei superan­dam. Sicut enim in cera partes primo extimae distrahuntur, in quarum locum succedit Aer; ita etiam in Corpore quan­tumlibet duro Aer locum subit partium extimarum, quae primae Vulfionis viribus dirumpuntur. Vis autem quae super at re­sistentiam partium extimarum Duri, fa­cilè superabit resistentiam reliquarum. Nam resistentia prima est à Toto Duro, reliquarum verò semper à Residuo.

A.

Ita quidem videtur consideranti, quàm Corpora quaedam, praesertim verò duris [...]ima, fragilia sint.

Does this Ratiocination [...]eem to you as cogent, as it did to the Proposer of it?

B.
[Page 10]

You will quickly think it does not, and perhaps you will think it should not, if you please to consider with me some of the Reflections that the Reading of it suggested to me.

And first, without declaring for the Vacuists Opinion, I must profess my self unsatisfied with Mr. Hobbes's way of arguing against them: For, where he says, Dum ergo illi qui Mar­mor unum ab altero revellentes Aerem comprimunt & per consequens Vacuum exprimunt, Vacuum faciunt locum per revulsionem relictum; nulla ergo separa­tionis erit difficultas, saltem non major quàm est difficultas corpora eadem mo­vendi in Aere postquam separata fuerint. Itaque quoniam, concesso Vacuo, diffi­cultas Marmora illa dirimendi nulla est, sequitur per difficultatis experientiam, nullum esse Vacuum. Methinks he ex­presses himself but obscurely, and leaves his Readers to ghess, what the word Dum refers to. But that which seems to be his drift in this passage, is, that, since the Vacuists allow inter­spersed Vacuities, not only in the Air [Page 11] that surrounds the conjoyned Mar­bles, but in the rest of the ambient Air, there is no reason, why there should be any difficulty in separating the Marbles, or at least any greater difficulty than in moving the Marbles in that Air after their separation. But, not to consider, whether his Adver­saries will not accuse his phrase of squeezing out a Vacuum as if it were a Body, they will easily answer, that notwithstanding the Vacuities they admit in the ambient Air, a manifest reason may be given in their Hypo­thesis of our finding a difficulty in the Divulsion of the Marbles. For, the Vacuities they admit being but inter­spers'd, and very small, and the Cor­puscles of the Atmosphere being ac­cording to them endow'd with Gra­vity, there leans so many upon the upper surface of the uppermost Mar­ble, that that stone cannot be at once perpendicularly drawn up from the lower Marble contiguous to it, without a force capable to surmount the weight of the Aerial Corpuscles [Page 12] that lean upon it. And this weigh [...] has already so constipated the neigh [...]bouring parts of the ambient Air that he, that would perpendicularl [...] raise the upper Marble from the lower shall need a considerable force to mak [...] the Revulsion, and compel the al [...] ready contiguous parts of the incum [...]bent Air to a subingression into the pores or intervals intercepted be [...]tween them. For the Conatus of him that endeavo [...]rs to remove the uppe [...] Marble, whilst the lower surface o [...] it is [...]enc'd from the pressure of th [...] Atmosphere by the Contact of th [...] lower Marble which suffers no Air to come in between them, is not assisted by the weight or pressure of the At [...]mosphere, which, when the Marble [...] are once separated, pressing as strong [...]ly against the undermost surface o [...] the upper Marble, as the incumben [...] Atmospherical Pillar does against th [...] upper surface of the same Marble [...] the hand that endeavours to raise i [...] in the free Air has no other resistance than that small one of the Marble own weight to surmount.

A.
[Page 13]

But what say you to the Rea­son that Mr. Hobbes, and, as he thinks, all others give of the difficulty of the often mention'd Divulsion, namely, Quod spatium totum inter duo illa Mar­mora divulsa simul uno instante implere Aer non potest, quantacunque celeritate fiat divulsio.

B.

I say, that, for ought I know, the Plenists may give a more plausible account of this Experiment, than Mr. Hobbes has here done; and there­fore abstracting from the two opposite Hypotheses, I shall further say, That the genuine Cause of the Phaenome­non seems to be that which I have already assign'd; and that difficulty of raising the upper stone that ac­companies the Airs not being able to come in all at once, to possess the space left between the surfaces of the two Marbles upon their separation, proceeds from hence, that, 'till that space be fill'd with the Atmospherical Air, the hand of him that would lift up the superiour Marble cannot be fully assisted by the pressure of [Page 14] the Air against the lower surface of that Marble.

A.

This is a Paradox, and there­fore I shall desire to know on what you ground it?

B.

Though I mention it but as a Conjecture propos'd ex abundanti, yet I shall on this occasion counte­nance it with two things; the first, that, since I declare not for the Hypo­thesis of the Plenists as 'tis maintain'd by Mr. Hobbes, I am not bound to al­low, what the common Explication, adopted by my Adversary, supposes; namely, that either Nature abhors a Vacuum (as the Schools would have it,) or that there could be no Divul­sion of the Marbles, unless at the same time the Air were admitted into the room that Divulsion makes for i [...]. And a Vacuist may tell you, that, provided the strength employ'd to draw up the superiour Marble be great enough to surmount the weight of the Aerial Corpuscles accumulated upon it, the divulsion would ensue, though by Divine Omnipotence no [Page 15] Air or other Body should be permitted to fill the room made for it by the divulsion; and that the Air's ru­shing into that space does not neces­sarily accompany, but in order of Nature and time follow upon, a se­paration of the Marbles, the Air that surrounded their contiguous surfaces being by the weight of the collate­rally superiour Air impell'd into the room newly made by the divulsion. But I shall rather countenance what you call my Paradox by an Experi­ment I purposely made in our Pneu­matical Receiver, where having ac­commodated two flat and polish'd Marbles, so that the lower being fixt, the upper might be laid upon it and drawn up again as there should be occasion, I found, that if, when the Receiver was well exhausted, the upper Marble was by a certain con­trivance laid flat upon the lower, they would not then cohere as for­merly, but be with great ease sepa­rated, though it did not by any Phae­nomenon appear, that any Air could [Page 16] come to rush in, to possess the place given it by the recess of the upper Marble, whose very easie avulsion is as [...]asily explicable by our Hyphothesis, since the pressure of that little Air, that remain'd in the Receiver, being too faint to make any at all con [...]ide­rable resistance to the avulsion of the upper Marble, the hand that drew it up had very little more than the single weight of the stone to sur­mount.

A.

An Anti-plenist had expected, that you would have observed, that the difficult separation of the Mar­bles in the open Air does rather prove, that there may be a Vacuum, than that there can be none. For in case the Air can succeed as fast at the sides as the divulsion is made, a Vacuist may demand, whence comes the dif­ficulty of the separation? And if the Air cannot fill the whole room made for it by the separated Marbles at the fame instant they are forc'd asunder, how is a Vacuum avoided for that time, how small soever, that is ne­cessary [Page 17] for the Air to pass from the edges to the middle of the room new­ly made?

B.

What the Plenists will say to your Argument I leave them to con­sider [...] but I presume, they will be able to give a more plausible account of the Phaenomenon we are treating of, than is given by Mr. Hobbes.

A.

What induces you to dislike his Explication of it?

B.

Two things, the one, that I think the Cause he assigns impro­bable; and the other, that I think a­nother, that is better, has been as [...]ign'd already.

And first, whereas Mr. Hobbes re­quires to the Divulsion of the Mar­bles a force great enough to sur­mount the hardness of the stone, this is asserted gratis, which it should not be; since it seems very unlikely, that the weight of so few pounds as will suffice to separate two coherent Marbles of about an Inch, for in­stance, in Diameter, should be able to surmount the hardness of such solid [Page 18] stones as we usually employ in this Experiment. And though it be ge­nerally judg'd more easie to bend, if it may be, or break a broader piece of Marble caeteris paribus, than a much narrower; yet, whereas neither I, nor any else that I know, nor I be­lieve Mr. Hobbes, ever observ'd any difference in the resistance of Mar­bles to separation from the greater or lesser thickness of the stones; I find by constant experience, that, caete­ris paribus, the broadness of the cohe­rent Marbles does exceedingly increase the difficulty of disjoyning them: Insomuch that, whereas not many pounds, as I was saying, would se­parate Marbles of an Inch, or a lesser, Diameter; when I increased their Diameter to about four Inches, if I misremember not, there were several Men that successively try'd to pull them asunder without being able by their utmost force to effect it.

A.

But what say you to the Il­lustration, that Mr. Hobbes, upon the supposition of the Worlds Plenitude, [Page 19] gives of our Phaenomenon by draw­ing asunder the opposite pa [...]s of a piece of Wax?

B.

To me it seems an Instance improper enough. For first, the parts that are to be divided in the Wax are of a soft and yielding consistence, and according to him of a ductile, or, if you please, of a tractile na­ture, and not, as the parts of the coherent Marbles, very solid and hard. Next, the parts of the Wax do not stick together barely by a superficial contact of two smooth Planes, as do the Marbles we are speaking of; but have their parts implicated, and as it were intangled with one another. And therefore they are far from a dis­position to slide off, like the Marbles; from one another, in how commo­dious a posture soever you place them. Besides 'tis manifest, that the Air has opportunity to succeed in the places successively deserted by the re­ceding parts of the attenuated Wax; but 'tis neither manifest, nor as yet well proved by Mr. Hobbes, that the [Page 20] Air does after the same manner suc­ceed between the two Marbles, which, as I lately noted, are not for­ced asunder after such a way, but are, as himself speaks, sever'd in all their points at the same instant.

A.

I know, you forget not what he says of the dividing of a hard Column into two parts by a force sufficient to overcome the resistance of its hardness.

B.

He does not here either affirm, that he, or any he can trust, has seen the thing done; nor does he give us any such account of the way wherein the Pillar is to be broken; whether in an erected, inclined, or horizontal posture; nor describe the particular circumstances that were fit to be mention'd in order to the solution of the Phaenomenon. Where­fore, 'till I be better inform'd of the matter of fact, I can scarce look up­on what Mr. Hobbes says of the Pil­lar, as other than his Conjecture, which now I shall the rather pass by, not only because the case is dif­fering [Page 21] from that of our polish'd Marbles, which are actually distinct Bodies, and only contiguous in one Commissure; but also, because I would hasten to the second reason of my dis­like of Mr. Hobbes's Explication of our Phaenomenon, which is, that a better has been given already, from the pressure of the Atmosphere upon all the superficial parts of the upper Marble save those that touch the Plane of the lower.

A.

You would have put fair for convincing Mr. Hobbes himself, at least would have put him to unusual shifts, if you had succeeded in the attempt you made, among other of your Physico-Mechanical Experi­ments, to disjoyn two coherent Mar­bles, by suspending them horizon­tally in your Pneumatical Receiver, and pumping out the Air that invi­ron'd them; for, from your failing in that attempt, though you ren­dred a not improbable Reason of it, Mr. Hobbes took occasion, in his Dia­logue De Nat [...]a Aeris, to speak in [Page 22] so high a strain as this: ‘Nihil isthic erat quod ageret pondus; Experimento hoc excogitari contra opinionem eorum qui Vacuum asserunt aliud argumentum fortius aut evidentius non potuit. Nam si duorum cohaerentium alterutrum secun­dùm eam viam, in quae jacent ipsae con­tiguae superficies, propulsum [...]sset, facile separarentur, Aere praximo in locum relictum successivè semper influente; sed illa ita divellere, ut simul totum amit­terent contactum, impossibile est, mundo pleno. Oporteret enim aut motum fieri ab uno termino ad alium in instante, aut duo corporae eodem tempore in eodem esse loco: Quorum utrumvis dicere, est absurdum.’

B.

You may remember, that where I relate that Experiment, I express'd a hope, that, when I should be better accommodated than I then was, I might attempt the Tryal with prosperous success, and accordingly afterwards, having got a lesser En­gine than that I used before, where­with the Air might be better pumpt out and longer kept out, I cheerfully repeated the Tryal. To shew then, [Page 23] that when two coherent Marbles are sustained horizontally in the Air, the Cause, why they are not to be forc'd asunder, if they have two or three Inches in Diameter, without the help of a considerable weight, is the pressure I was lately mentio­ning of the ambient Air; I caused two such coherent Marbles to be sus­pended in a large Receiver, with a weight at the lowermost, that might help to keep them steddy; but was very inconsiderable to that which their Cohesion might have su [...]moun­ted; then causing the Air to be pumpt by degrees out of the Recei­ver, for a good while the Marbles stuck close together, because during that time the Air could not be so far pumpt out, but that there remai­ned enough to sustain the small weight that endeavoured their divul­sion: But when the Air was further pumpt out, at length the Spring of the little, but not a little expanded, Air, that remained, being grown too weak to sustain the lower Marble [Page 24] and its small clog, they did, as I expected, drop off.

A.

This will not agree over-well with the confident and triumphant expressions just now recited.

B.

I never envied Mr. Hobbes's forwardness to triumph, and am con­tent, his Conjectures be recommended by the confidence that accompanies them, if mine be by the success that follows them. But to confirm the Explication given by me of our Phae­nomenon, I shall add, that as the last mention'd Tryal, which I had several times occasion to repeat, shews, that the cohesion of our two contiguous Marbles would cease up­on the withdrawing of the pressure of the Atmosphere; so by another Experiment I made, it appears, that the supervening of that pressure suf­ficed to cause that Cohesion. For, in prosecution of one of the lately mentioned Tryals, having found, that when the Receiver was well ex­hausted, two Marbles, though con­siderably broad, being laid upon one [Page 25] another after the requisite manner, their adhesion was, if any at all, so weak, that the uppermost would be easily drawn up from off the other; we laid them again one upon the other, and then letting the external Air flow into the Receiver, we found, according to expectation, that the Marbles now cohered well, and we could not raise the uppermost but accompanied with the lower­most. But I am sensible, I have de­tained you too long upon the single Experiment of the Marbles: And though I hope the stress Mr. Hobbes lays on it will plead my excuse, yet to make your Patience some amends, I shall be the more brief in the other particulars that remain to be con­sider'd in his Dialogue De Vacuo. And 'twill not be difficult for me to keep my promise without injuring my Cause, since almost all these particu­lars being but the same which he has already alledged in his Dialogue De Natur [...] Aeris, and I soon after an­swered in my Examen of that Dia­logue, [Page 26] I shall need but to refer you to the passages where you may find these Allegations examin'd, only sub­joyning here some Reflections upon those few and slight things, that he has added in his Problems De Vacuo.

A.

I may then, I suppose, read to you the next passage to that long one, you have hitherto been conside­ring, and it is this: ‘Ad Vacuum nunc revertor: Quas causas sine suppositione Vacui redditurus es illorum effectuum, qui ostenduntur per Machinam illam quae est in Collegio Greshamensi?’

B.

Machina illa—

B.

Stop here, I beseech you, a little, that, before we go any fur­ther, I may take notice to you of a couple of things that will concern our subsequent Discourse.

Whereof the first is, that it ap­pears by Mr. Hobbes's Dialogue about the Air, that the Explications he there gave of some of the Phaenomena of the Machina Boyliana, were directed partly against the Virtuosi, that have since been honour'd with the Title [Page 27] of the Royal Society, and partly against the Author of that Engine, as if the main thing therein design'd were to prove a Vacuum. And since he now repeats the same explications, I think it necessary to say again, that if he ei­ther takes the Society or me for profess'd Vacuists, he mistakes, and shoots be­side the mark; for, neither they nor I have ever yet declar'd either for or against a Vacuum.

And the other thing I would ob­serve to you, is, that Mr. Hobbes seems not to have rightly understood, or at least not to have sufficiently heeded in what chiefly consists the advantage, which the Vacuists may make of our Engine against him: For, whereas in divers places he is very solicitous to prove, that the cavity of our Pneumatical Receiver is not altogether empty, the Vacuists may tell him, that since he asserts the absolute plenitude of the World, he must, as indeed he does, reject not only great Vacuities, but also those very small and interspers'd [Page 28] ones, that they suppose to be inter­cepted between the solid corpuscles of other bodies, particularly of the Air: So that it would not confute them to prove, that in our Receiver, when most diligently exhausted, there is not one great and absolute Vacuity, or, as they speak, a Vacuum coacervatum, since smaller and disse­minated Vacuities would serve their turn. And therefore they may think their Pretensions highly favour'd, as by several particular effects, so by this general Phaenomenon of our En­gine, that it appears by several Cir­cumstances, that the Common or At­mospherical Air, which, before the pump is set a work, possess'd the whole cavity of our Receiver, far the greatest part is by the inter­vention of the pump made to pass out of the cavity into the open Air, without being able, at least for a little while, to get in again; and yet it does not appear by any thing alledg'd by Mr. Hobbes, that any o­ther body succeeds to fill adequately [Page 29] the places deserted by such a multitude of Aerial corpuscles.

A.

If I ghess aright, by those words, (viz. it appears not by any thing alledg'd by Mr. Hobbes,) you design to intimate, that you would not in general prejudice the Plenists.

B.

Your conjecture was well founded: For I think divers of them, and particularly the Cartesians, who suppose a subtile Matter or AEther fine enough to permeate glass, though our common Air cannot do it, have not near so difficult a task to avoid the Arguments the Vacuifts may draw from our Engine, as Mr. Hobbes, who, without having recourse to the porosity of glass, which indeed is impervious to common Air, strives to solve the Phaenomena, and prove our Receiver to be always perfectly full, and therefore as full at any one time as at any other of common or Atmospherical Air, as far as we can judge of his opinion by the tendency or import of his Explications.

A.

Yet, if I were rightly inform'd [Page 30] of an Experiment of yours, Mr. Hobbes may be thereby reduc'd either to pass over to the Va [...]uist's, or to ac­knowledge some AEtherial or other matter more subtil than Air, and ca­pable of passing through the pores of glass; and therefore, to shew your self impartial between the Vacuists and their Adversaries in this Contro­versie, I hope you will not refuse to gratifie the Plenists by giving your friends a more particular account of the Experiment.

B.

I know which you mean, and remember it very well. For, though I long since devis'd it, yet having but the other day had occasion to peruse the Relation I writ down of one of the best Tryals, I think I can repeat it, almost in the very words, which, if I mistake not, were these:

There was taken a Bubble of thin white glass, about the bigness of a Nutmeg, with a very slender stem, of about four or five Inches long, and of the bigness of a Crows-quill. [Page 31] The end of the Quill being held in the flame of a Lamp blown with a pair of Bellows, was readily and well seal'd up, and presently the globous part of the glass, being held by the stem, was kept turning in the flame, 'till it was red hot and ready to melt; then being a little removed from the flame, as the included Air be­gan to lose of its agitation and spring, the external Air manifestly and con­siderably press'd in one of the sides of the Bubble. But the glass being a­gain, before the cold could crack it, held as before in the flame, the ra­rified Air distended and plump'd up the Bubble; which being the second time remov'd from the flame, was the second time compress'd; and, being the third time brought back to the flame, swell'd as before, and remov'd, was again compress'd, (ei­ther this time or the last by two di­stinct cavities;) 'till at length, having satisfied our selves, that the included Air was capable of being condens'd or dilated without the ingress or [Page 32] egress of Air (properly so called) we held the Bubble so long in the flame, strengthen'd by nimble blasts, that not only it had its sides plump'd up, but a hole violently broken in it by the over-rarified Air, which, together with the former watchful­ness, we imploy'd from time to time to discern if it were any where crackt or perforated, satisfied us that it was till then intire.

A.

I confess, I did not readily conceive before, how you could, (as I was told you had,) make a solid Vessel, wherein there was no danger of the Aires getting in or out, whose cavity should be still possest with the same Air, and yet the Vessel be made by turns bigger and lesser. And, though I presently thought upon a well stopt bladder, yet I well foresaw, that a distrustful Adversary might make some Objections, which are by your way of proceeding obviated, and the Experiment agrees with your Doctrine in shewing, how imper­vious we may well think your thick [Page 33] Pneumatick Receivers are to common Air, since a thin glass Bubble, when its pores were open'd or relax'd by flame, would not give passage to the Springy particles of the Air, though violently agitated; for if those par­ticles could have got out of the pores, they never would have broke the Bubble, as at length a more violent degree of Heat made them do; nor probably would the Compression, that afterwards insued of the Bubble by the ambient Air, be checkt near so soon, if those Springy Corpuscles had not remained within to make the resistance. Methinks, one may hence draw a new proof of what I remem­ber you elsewhere teach, that the Spring of the Air may be much strengthen'd by Heat. For, in our case, the Spring of the Air was there­by inabled to expand the comprest glass, it was imprison'd in, in spite of the resisting pressure of the exter­nal Air; and yet, that this pressure was considerable, appears by this, that the weight of so small a Column [Page 34] of Atmospherical Air, as could bear upon the Bubble, was able to press in the heated glass, in spite of the re­sistance of its tenacity and arched fi­gure.

B.

Yet that which I mainly de­sign'd in this Experiment was, (if I were able) to shew and prove at once, by an Instance not lyable to the ordinary exceptions, the true Nature of Rarefaction and Condensation, at least of the Air. For, to say nothing of the Peripatetick Rarefaction and Condensation, strictly so call'd, which I scruple not to declare, I think to be physically inconceptible or impossi­ble; 'tis plain by our Experiment, that, when the Bubble, after the Glass had been first thrust in towards the Center, was expanded again by heat, the included Air possess'd more room than before, and yet it could perfectly fill no more room than formerly, each Aerial Particle taking up, both before and after the heating of the Bubble, a portion of space adequate to its own bulk; so that in the Cavity of the [Page 35] expanded Bubble we must admit either Vacuities interspers'd between the Corpuscles of the Air, or that some fine Particles of the Flame, or other subtil matter, came in to fill up those Intervals, which matter must have enter'd the Cavity of the Glass at its pores: And afterwards, when the red-hot Bubble was removed from the flame, it is evident, that, since the grosser particles of the Air could not get through the Glass, which they were not able to do, even when vehemently agitated by an ambient Flame, the Compression of the Bub­ble, and the Condensation of the Air, which was necessarily consequent up­on it, could not, supposing the Ple­nitude of the World, be performed without squeezing out some of the subtil matter contained in the cavity of the Bubble, whence it could not issue but at the pores of the Glass. But I will no longer detain you from Mr. Hobbes his Explications of the Machina Boyliana; to the first of which you may now, if you please, advan [...].

A.
[Page 36]

The passage I was going to read, when you interrupted me, was this:

B.

Machina illa eosdem effectus pro­ducit, quos produceret in loco non magno magnus inclusus ventus.

A.

Quomodo ingreditur istuc ventus? Machinam nosti Cylindrion esse cavum, aeneum, in quem protruditur Cylindrus alius solidus ligneus, coriotectus, (quem suctorem dicunt) ita exquisitè congruens, ut ne minimus quidem Aer inter corium & aes intrare (ut putant) possit.

B.

Scio, & quò Suctor facilius in­trudi possit, foramen quoddam est in su­periori parte Cylindri, per quod Aer (qui suctoris ingressum alioqui impedire possit) emittatur. Quod foramen aperire possunt & claudere quoties usus postulat. Est etiam in Cylindri cavi recessu summo datus aditus Aeri in globum concavum Vitreum, quem etiam aditum claviculâ obturare & aperire possunt quoties volunt. Denique in globo vitreo summo relinqui­tur foramen satis amplum, (claviculâ item claudendum & recludendum) ut in illum quae volunt immittere possint, experiendi causâ.

B.
[Page 37]

The imaginary wind to which Mr. Hobbes here ascribes the effects of our Engine, he formerly had recourse to in the 13 th page of his Dialogue, and I have sufficiently answer'd that passage of it in the 45 th and 46 th pa­ges of my Examen, to which I there­fore refer you.

A.

I presume, you did not over­look the comparison Mr. Hobbes an­nexes to what I last read out of his Problems, since he liked the conceit so well, that we meet with it in this place again, though he had formerly printed it in his Dialogue De Natura Aeris. The words (as you see) are these: ‘Tota denique Machina non mul­tum differt, si naturam ejus spectes, à Sclopeto ex Sambuco, quo pueri se de­lectant, imitantes Sclopetos militum, nisi quòd major sit, & majori arte fabricatus, & pluris constet.’

B.

I could scarce, for the reason you give, avoid taking notice of it. And if Mr. Hobbes intended it for a piece of Ralliery, I willingly let it pass, and could easily forgive him a more [Page 38] considerable attempt than this, to be reveng'd on an Engine that has de­stroyed several of his opinions: But, if he seriously meant to make a Phy­sical Comparison, I think he made a very improper one. For, not to urge, that one may well doubt how he knows, that in the inclosed cavity of his Pot-gun, there is a very vehe­ment wind, (since that does not ne­cessarily follow from the compreffion of the included Air:) In Mr. Hobbes's Instrument, the Air, being forcibly comprest, has an endeavour to expand it self, and when it is able to sur­mount the resistance of its prison, that part that is first disjoyn'd is for­cibly thrown outwards; whereas in our Engine it appears by the passage lately cited of our Examen, that the Air is not comprest but expanded in our Receiver, and if an intercourse be open'd, or the Vessel be not strong enough, the outward Air violently rushes in: And if the Receiver chance to break, the fragments of the glass are not thrown outwards, but forced in­wards.

A.
[Page 39]

So that, whether or no Mr. Hobbes could have pitch'd upon a Comparison more suitable to his Intentions, he might easily have im­ployed one more suitable to the Phae­nomena.

B.

I presume, you will judge it the less agreeable to the Phaenomena, if I here subjoyn an Experiment, that possibly you will not dislike; which I devis'd to shew, not only that in our exhausted Receivers there is no such strong endeavour outwards, as most of Mr. Hobbes's Explications of the things that happen in them are built upon, but that the weight of the Atmospherical Air, when 'tis not resisted by the counterpressure of any internal Air, is able to perform what a weight of many pounds would not suffice to do.

A.

I shall the more willingly learn an Experiment to this purpose, be­cause in your Receivers, the rigidity of the glass keeps us from seeing, by any manifest change of its figure, whether, if it could yield without [Page 40] breaking, it would be press'd in, as your Hypothesis requires.

B.

The desires to obviate that very difficulty, for their satisfaction, that had not yet penetrated the grounds of our Hypothesis, made me think of employing, instead of a Receiver of Glass, one of a stiff and tough, but yet somewhat flexible, Metal. And accordingly having pro­vided a new Pewter Porrenger, and whelm'd it upside down upon an Iron plate fasten'd to (the upper end of) our Pneumatical Pump, we carefully fasten'd by Cement the orifice to the plate, and though the inverted Vessel, by reason of its stiffness and thick­ness and the convexity of its super­ficies, were strong enough to have supported a great weight without changing its figure; yet, as soon as by an exsuction or two the remain­ing part of the included Air was brought to such a degree of expan­sion, that its weaken'd Spring was able to afford but little assistance to the tenacity and firmness of the Metal, [Page 41] the weight of the pillar of the in­cumbent Atmosphere (which by rea­son of the breadth of the Vessel was considerably wide also) did presently and notably depress the upper part of the Porringer, both lessening its capacity and changing its figure; so that instead of the Convex surface, the Receiver had before, it came to a Concave one, which new figure was somewhat, though not much, increased by the further withdrawing of the included and already rarified Air. The Experiment succeeded al­so with an other common Porringer of the same Metal. But in such kind of Vessels, made purposely of Iron plates, it will sometimes succeed and sometimes not, according to the Dia­meter of the vessel and the thickness of the plate, which was sometimes strong enough and sometimes too weak to resist the pressure of the in­cumbent Air. And sometimes I found also, that the vessel would be thrust in, not at the top but side-ways, in case that side were the only part that [Page 42] were made too thin to resist the pressure of the Ambient; which Phaenomenon I therefore take notice of, that you may see, that that pow­erful pressure may be exercised late­rally as well as perpendicularly.

Perhaps this Experiment, and that I lately recited of an Hermetically sealed Bubble, by their fitness to dis­prove Mr. Hobbes's Doctrine, may do somewhat towards the letting him see, that he might have spar'd that not over-modest and wary expression, where speaking of the Gentlemen that meet at Gresham-College, (of whom I pretend not to be one of the chief) he is pleased to say, Experimenta fa­ciant quantum volunt, nisi Principiis u­tantur meis nihil proficient. But let us, if you please, pass on to what he further alledges to prove, that the space in the exhausted Receiver, which the Vacuists suppose to be partly empty, is full of Air. ( Video (says A.) si suctor trudatur usque ad fundum Cylindri AEnei, obturenturque for amina, Secuturum esse, dum suctor retrahitur, [Page 43] locum in Cylindro cavo relictum fore va­cuum. Nam ut in locum ejus succedat Aer, est impossible. To which B. an­swers, Credo equidem, suctorem cum Cy­lindri cavi superficie satis arctè cohae­rere ad excludendum stramen & plu­mam, non autem Aerem neque Aquam. Cogita enim, quod non ita accuratè con­gruerent, quin undiquaque interstitium relinqueretur, quantum tenuissimi capilli capax esset. Retracto ergo suctore, tan­tum impelleretur Aeris, quantum viribus illis conveniret quibus Aer propter sucto­ris Retractionem reprimitur, idque sine omni difficultate sensibili. Quanto au­tem interstitium illud minus esset, tan­tum ingrederetur Aer velocius: Vel si contactus sit, sed non per omnia puncta, etiam tunc intrabit Aer, modò suctor ma­ [...]ore vi retrahatur. Postremò, etsi con­ [...]actus ubique exactissimus sit, vi tamen [...]atis auct [...] per cochleam ferream, tum [...]orium cedet, tum ipsum es; atque it a quoque ingredietur Aer. Credin' tu, [...]osfibile esse duas superficies it a exactè [...]omponere, ut has compositas esse suppo­ [...]unt illi; aut corium it a durum esse, [Page 44] ut Aeri, qui Cochleae ope incutitur, nihi omnino cedat? Corium quanquam opti­mum admittit aquam, ut ipse scis, fortè fecisti unquam iter vento & pluvi [...] [...]. Itaque dubitare no [...] potes, quin retractus Suctor tantum A [...] ris in Cylindrum adeoque in ipsum Rec [...] ­piens incutiat, quantum sufficit ad locu [...] semper relictum perfectè implendu [...] Effectus ergo, qui oritur à Retractio [...] suctoris, alius non est quàm ventu [...] ventus (inquam) vehementissimus [...] q [...] ingreditur undiquaque inter Suctoris s [...] perficiem convexan, & Cylindri aen [...] concavam, proceditque (versâ clavicul [...] in cavitatem globl Vitrei, sive (u [...]ocatur Recipientis.

The Substance of this Ratiocin [...] ­tion having been already propos'd [...] Mr. Hobbes in his Dialogue of th [...] Air, the 11 th page, I long since a [...] ­swer'd it in the 30 th and some of th [...] following pages of my Examen; an [...] therefore I shall only now take noti [...] in transitu of some slight whether a [...]ditions or variations, that occur [...] what you have been reading. And [Page 45] first, I see no probability in what he gratis asserts, that so thick a Cylinder of Brass, as made the chief part of the pump of our Engine, should yield to the Sucker, that was mov'd up and down in it, though by the help of an Iron rack; and whereas he adds, that the leather, that surrounds the more solid part of the Sucker, would yield to such a force; it seems, that that compression of the leather should by thrusting the solid parts in­to the pores make the leather rather less than more fit to give passage to the Air; nor would it however fol­low, notwithstanding Mr. Hobbes's Example, that, because a Body ad­mits Water, it must be pervious to Air: For I have several times, by ways elsewhere taught, made Water penetrate the pores of Bladders, and yet Bladders resist the passage of the Air so well, that even when Air in­cluded in them was sufficiently rari­fied by Heat, or by our Engine, it was necessary for the Air to break them before it could get out; which [Page 46] would not have been, if it could have escap'd through their pores. What Mr. Hobbes inculcates here a­gain concerning his ventus vehemen­tissimus, you will find answer'd in the place of my Examen I lately directed you to.

A.

We may then proceed to Mr. Hobbes's next Explication, which he proposes in these terms:

A.

Causam video nunc unius ex Ma­chinae mirabilibus, nimirum cur Suctor, postquam est aliquatenus retractus & de­inde amissus, subitò recurrit ad Cylindri summitatem. Nam Aer, qui vi magna fuit impulsus, rursus per repercussionem ad externa vi eadem revertitur.

B.

Atque hoc quidem Argumenti satis est etiam solum, quòd locus à suctore relictus non est Vacuus. Quid enim aut attrahere aut impellere suctorem potuit ad locum illum unde retractus erat, si Cylindrus fuisset vacuus? Nam ut Aeris pondus aliquod id efficere potuisset, fal­sum esse satis supra demonstravi ab eo quod Aer in Aere gravitare non potest. Nosti etiam, quod cum è recipiente [Page 47] Aerem omnem (ut illi loquuntur) exege­rint, possunt tamen trans vitrum id quod intus fit videre, & sonum, si quis [...]iat, inde audire. Id quod solum, etsi nullum aliud Argumentum esset (sunt autem multa,) ad probandum, nullum esse in Recipiente Vacuum, abundè sufficit.

B.

Here are several things joyn'd together, which the Author had be­fore separately alledg'd in his often-mention'd Dialogue. The first is, the Cause he assigns of the ascension of the Sucker forcibly deprest to the bottom of the exhausted Cylinder, and then let alone by him that pumpt; to which might be added; that this ascension succeeded, when the Sucker was clogg'd with an hundred pound weight. This Explication of Mr. Hobbes you will find examin'd in the 33 th and 39 th, and some ensuing pages of my Discourse. And as to his deny­ing, that the weight or pressure of the Air could drive up the Sucker in that Phaenomenon, because the Air does not weigh in Air, we may see the contrary largely proved in divers [Page 48] places of my Examen, and more par­ticularly and expresly in the four first pages of the third Chapter. And whereas he says in the last place, that the visibility of Bodies included in our Receivers, and the propaga­tion of Sound, (which, by the way, is not to be understood of all Sound that may be heard, though made in the exhausted Receiver,) are alone sufficient Arguments to prove no Va­cuum: I have consider'd that passage in the answer I made to the like alle­gation in the 45 th page of the Exa­men; and shall only observe here, that, since the Vacuists can prove, that much of the Air is pumpt out of the exhausted Receiver, and will pretend, that, notwithstanding many interspers'd Vacuities, there may be in the Receiver corporeal substance enough to transmit Light and stron­ger Sounds, Mr. Hobbes has not per­form'd what he pretended, if he have but barely proved, that there may be Substances capable of conveying Light and Sound in the cavity of our [Page 49] Receiver, since he triumphantly as­serts, Nullum esse in Recipienti Vacuum. But we may leave Mr. Hobbes and his Adversaries to dispute out this point, and go on to the next passage.

A.

Which follows in these words: ‘Ad illud autem, quod si Vesica ali­quatenus inflata in Recipiente includatur, paulo post per exuctionem aeris inflatur ve­hementius & dirumpitur, quid respondes?’

B.

Motus partium Aeris undiquaque concurrentium velocissimus & per concur­sum in spatiis brevissimis numeroque in­finitis gyrationis velocissimae vesicam in locis innumerabilibus simul & vi magna, instar totidem terebrarum, penetrat, praesertim si vesica, antequam immitta­tur, quò magis resistat aliquatenus in­flata fit. Postquam autem Aer penetrans semel ingressus est, facile cogitare potes, quo pacto deinceps vesicam tendet, & tandem rumpet. Verùm si antequam rumpatur, versâ claviculâ, Aer externus admittatur, videbis vesicam propter vehe­mentiam motus temperatam diminutâ tensione rugosiorem. Nam id quoque ob­servatum est. Iam si haec, quam dixi, [Page 50] causa minùs tibi vide atur verisimilis, vide an tu aut alius quicunque imaginari potest, quo pacto vesica distendi & rumpi possit à viribus Vacui, id est, Nihili.

B.

This Explication Mr. Hobbes gave us in the 19 th page of his Dia­logue De Natura Aeris, and you may find it at large confuted in the latter part of the third Chapter of my Exa­men. Nor does, what he here says in the close about the Vires Vacui or Nihili, deserve to detain us, since there is no reason at all, that the Vacuists should ascribe to nothing a power of breaking a Bladder, of whose rupture the Spring of the in­cluded Air supplies them so easily with a sufficient Cause.

After what Mr. Hobbes has said of the breaking of a Bladder, he pro­ceeds to an Experiment which he judges of affinity with it, and his A­cademian having propos'd this Que­stion: ‘Unde fit ut animalia tam cito, ni­mirum spatio quatuor minutorum horae, in recipiente interficiantur?’

[Page 51]For answer to it our Author says:

B.

Nonne animalia sic inclusa in­sugunt in Pulmones Aerem vehementis­simè motum? Quo motu necesse est ut transitus sanguinis ab uno ad alterum cordis ventriculum interceptus, non multò pòst sistatur. Cessatio autem sanguinis, Mors est. Possunt tamen animalia ces­sante sanguine reviviscere, si Aer ex­ternus satis maturè intromittatur, vel ipsa in Aerem temperatum, antequam refrixerit sanguis, extrahantur.

This Explication is not probable enough, to oblige me to add any thing about it to what I have said in the 49 th and the two following pages of my Examen; especially the most vehement motion, ascrib'd to the Air in the Receiver, having been before proved to be an Imaginary thing. You may therefore, if you please, take notice of the next Explication.

‘[Idem Aer (says he) in Recipiente Carbones ardentes extinguit, sed & illi, si, dum satis calidi sunt, eximantur, re­lucebunt. Notissimum est, quòd in fodi­nis Carbonum terreorum (cujus rei ex­perimentum [Page 52] ipse vidi) saepissime è late­ribus foveae ventus quidam undiquaque exit, qui fossores interficit ignemque extinguit, qui tamen reviviscunt si satis cito ad Aerem liberum extrahan­tur.]’

This Comparison which Mr. Hobbes here summarily makes, he more fully display'd in his Dialogue De Natura Aeris, and I consider'd, what he there alledg'd, in the 52 th page and the two next of my Examen. And, though I will not contradict Mr. Hobbes in what he historically asserts in this passage; yet I cannot but somewhat doubt, whether he mingles not his conjecture with the bare matter of fact. For, though I have with some curiosity visited Mines in more places than one, and propos'd Questions to Men that have been conversant in o­ther Mines, both elsewhere and in England (and particularly in Derbysbire where Mr. Hobbes lived long;) yet I could never find, that any such odd and vehement wind, as Mr. Hobbes ascribes the Phaenomenon to, had [Page 53] been by them observed to kill the Diggers, and extinguish well-lighted Coals themselves: And indeed, it seems more likely, that the damp, by its tenacity or some peculiarly ma­lign quality, did the mischief, than a wind, of which I found not any notice taken; especially since we see, what vehement winds Men will be able to endure for a long time, with­out being near-kill'd by them; and that it seems very odd, that a wind, that Mr. Hobbes does not observe to have blown away the Coals, that were let down, should be able (in­stead of kindling them more fiercely) to blow them out.

A.

The last Experiment of your Engine, that your Adversary men­tions in these Problems, is deliver'd in this passage:

A.

Si phialam aqua in Recipiens dimiseris, exucto Aere bullire videbis a­quam. Quid ad hoc Respondebis?

B.

Credo sanè in tanta Aeris moti­tatione saltaturam esse aquam, sed ut calefiat nondum audivi. Sed imagina­bile [Page 54] non est, Saltationem illam à Vacuo nasci posse.

B.

This Phaenomenon he likewise took notice of, and attempted to ex­plicate in his above-mention'd Dia­logue, which gave me occasion in the 46 th and 47 th pages of my Exa­men, to shew how unlikely 'tis, that the vehement motion of the Air should be the cause of it; but he here tells us, that 'tis not imagina­ble, that this dancing of the water (as he is pleas'd to call it) proceeds from a vacuum, nor do I know any Man that ever pretended, that a va­cuum was the efficient cause of it. But the Vacuists perhaps will tell him, that, though the bubbling of the water be not an effect of a vacuum, it may be a proof of it against him; for they will tell him, that it has been formerly proved, that a great part of the Atmospherical Air is by pumping remov'd out of our exhausted Re­ceiver, and consequently can no more, as formerly, press upon the surface of the water. Nor does Mr. Hobbes [Page 55] shew what succeeds in the room of it; and therefore it will be allowable, for them to conclude against him (though not perhaps against the Car­tesians) that there are a great many interspers'd Vacuities left in the Re­ceiver, which are the occasion, though not the proper efficient cause, of the Phaenomenon. For they will say, that the Springy Particles of the yet included Air, having room to unbend themselves in the spaces deserted by the Air that was pumpt out, the Aerial and Springy Corpuscles, that lay conceal'd in the pores of the wa­ter, being now freed from the wonted pressure that kept them coil'd up in the liquor, expanded themselves in­to numerous bubbles, which, be­cause of their comparative lightness, are extruded by the water, and ma­ny of them appear to have risen from the bottom of it. And Mr. Hobbes's vehement wind, to produce the se­veral Circumstances of this Experi­ment, must be a lasting one. For, after the agitation of the Pump has [Page 56] been quite left off, provided the ex­ternal Air be kept from getting in, the bubbles will sometimes continue to rise for an hour after. And that which agrees very well with our Explication and very ill with that of M r Hobbes's, is, that, when by having continued to pump a competent time, the wa­ter has been freed from the Aerial particles that lurk'd in it before, though one continue to pump as lu­stily as he did, yet the water will not at all be cover'd with bubbles as it was, the Air that produc'd them being spent; though, according to Mr. Hobbes's Explication, the wind in the Receiver continuing, the dance of the water should continue too.

A.

I easily ghess, by what you have said already, what you may say of that Epiphonema wherewith Mr. Hobbes (in his 18 th page) concludes the Explications of the Phaenomena of your Engine. [ Spero jam te cer­tum esse, says he, nullum esse Machinae illius Phaenomenon, quo demonstrari potest ullum in Universo locum dari corpore omni vacuum.]

B.
[Page 57]

If you ghess'd aright, you ghess'd that I would say, that as to the Phaenomena of my Engine, my business was to prove, that he had not substituted good Explications of them in the place of mine, which he was pleased to reject. And as for the proving a Vacuum by the Phae­nomena of my Engine, though I de­clar'd that was not the thing inten­ded, yet I shall not wonder, that the Vacuists should think those Phae­nomena give them an advantage a­gainst Mr. Hobbes. For, though in the passage recited by you he speak more cautiously than he is wont to do, yet, by what you may have al­ready observ'd in his Argumentations, the way he takes to solve the Phae­nomena of our Engine, is by con­tending, that our Receiver, when we say it is almost exhausted, is as full as ever (for he will have it per­fectly full,) of common Air; which is a conceit so contrary to I know not how many Phaenomena, that I do not remember I have met with or [Page 58] heard of any Naturalist, whether Vacuist or Plenist, that having read my Physico-Mechanical Experiments and his Dialogue, has embrac'd his opinion.

A.

After what you have said, I will not trouble you with what he subjoyns about Vacuum in general, where having made his Academian say, [ Mundum scis finitum esse, & per Consequens vacuum esse oportere totum illud Spatium quod est extra mundum in­finitum. Quid impedit quo minus va­cuum illud cum Aere mundano permiscea­tur?] He answers: De rebus trans­mundanis nihil scio. For I know, that it concerns not you to take notice of it. But possibly the Vacuists will think, he fathers upon them an Im­propriety they would not be guilty of, making them speak, as if they thought, the ultra-mundan Vacuum were a real Substance that might be brought into this World and mingled with our Air. And since, for ought I know, Mr. Hobbes might have spar'd this passage, if he had not de­sign'd [Page 59] it should introduce the sligh­ting answer he makes to it; I shall add, that by the account Mr. Hobbes has given of several Phaenomena within the World, 'tis possible, that the Vacuists may believe his Profes­sion of knowing nothing of things beyond it.

After the Experimenta Boyliana (as your other Adversary calls them;) Mr. Hobbes proceeds to the Torricel­lian Experiment, of which he thus discourses:

A.

Quid de experimento senses Tor­ricelliano, probante Vacuum per Argen­tum vivum hoc modo: est in seq. figura ad A, pelvis sive aliud vas, & in eo Argentum vivum usque ad B; est au­tem C D tubus vitreus concavus reple­tus quoque Argento vivo. Hunc tubum si digito obturaveris erexerisque in vase A, manumque abstuleris, descendet Ar­gentum vivum à C; verùm non effun­detur totum in pelvim, sed sistetur in di­stantia quadam, puta in D. Nonne ergo necessarium est, ut pars tubi inter C & D sit vacua? Non enim puto negabis [Page 60] quin superficies tubi concava & Argenti vivi convexa se mutuo exquisitissim [...] contingant.

B.

Ego neque nego contactum, nequ [...] vim Consequentiae intelligo.

By which passage it seems that he still persists in the solution of this Experiment, which he gave in his Dialogue De Natura Aeris, and for­merly did, for the main, either pro­pose, or adopt, in his Elements of Philosophy.

B.

This opinion or explication o [...] Mr. Hobbes I have, as far as concern [...] me, consider'd in the 36 th, and some insuing pages, of my Examen, to which it may well suffice me to refer you. But yet let me take notice of what he now alledges:

B.

Si quis (says he) in Argentum vivum, quod in vase est, vesicam im­merserit inflatam, nonne illa amot â man [...] emerget?

A.

Ita certè, etsi esset vesica ferre [...] vel ex materia quacunque praeter Aurum.

B.

Vides igitur ab Aere penetran [...] posse Argentum vivum.

A.
[Page 61]

Etiam, & quidem illâ ipsâ vi quam à pondere accipit Argenti vivi.

I confess this Allegation did a little surprize me: It concern'd Mr. Hobbes to prove, that as much Air, as was displac'd by the descending Mercury, did at the orifice of the Tube, im­mers'd in stagnant Mercury, invisibly ascend to the upper part of the pipe. To prove this he tells us, that a blad­der full of Air being depress'd in Quicksilver, will, when the hand that depress'd it is remov'd, be squeez'd up by the very weight of the Mer­cury, whence it follows, that Air may penetrate Quicksilver. But I know not, who ever deny'd, that Air inviron'd with Quicksilver may thereby be squeez'd upwards; but, since even very small bubbles of Air may be seen to move in their passage through Mercury, I see not, how this Example will at all help the Pro­poser of it. For 'tis by meer acci­dent, that the Air included in the bladder comes to be buoy'd up, be­cause the bladder it self is so; and if [Page 62] it were fill'd with Water instead of Air, or with Stone instead of Water, it would nevertheless emerge, as himself confesses it would do, if it were made of Iron, or of any Matter besides Gold, because all other Bo­dies are lighter in specie than Quick­silver. But since the emersion of the bladder is manifest enough to the sight, I see not how it will serve Mr. Hobbes's turn, who is to prove that the Air gets into the Torricel­lian Tube invisibly; since 'tis plain, that even heedful observation can make our Eyes discover no such tra­jection of the Air; which (to add that inforcement of our Argument) must not only pass unseen through the sustained Quicksilver, but must like­wise unperceivedly dive, in spite of its comparative lightness, beneath the surface of the ponderous stagnant Mercury, to get in at the orifice of the erected Tube. But let us, if you please, hear the rest of his Discourse about this Experiment.

A.

Though it be somewhat pro­lix, [Page 63] yet, according to my custom hi­therto, I will give it you verbatim.

B.

Simul atque Argentum vivum descenderit ad D, altius erit in vase A quàm antè, nimirum plus erit Argenti vivi in vase quàm erat ante descensum, tanto quantum capit pars tubi C, D. Tanto quoque minus erit Aeris extra tu­bum quàm ante erat. Ille autem Aer qui ab Argento vivo loco suo extrusus est, (suppositâ universi plenitudine) quò abire potest nisi ad eum locum, qui in tubo inter C & D à descensu Argenti vivi relin­quebatur? sed quâ, inquies, viâ in il­lum locum successurus est? Quà, nisi per ipsum corpus Argenti vivi Aerem urgen­tis? Sicut enim omne grave liquidum, sae ipsius pondere, Aerem, quem descendendo premit, ascendere cogit (si via alia non detur) per suum ipsius corpus; ita quoque Aerem quem premit ascendendo, (si viae alia non detur) per suum ipsius corpus transire cogit. Manifestum igitur est, suppositâ mundi plenitudine posse Aerem externum ab ipsa gravitate Argenti viv [...] cogi in locum illum inter C & D. Itaque Phaenomenon illud necessitatem vacui non [Page 64] demonstrat. Quoniam autem corpus Ar­genti vivi penetrationi, quae fit ab Aere, non nihil resistit, & ascensioni Argenti vivi in vase A resistit Aer; quando illae duae resistentiae aequales erunt, tunc in tubo sistetur alicubi Argentum vivum; atque ibi est D.

B.

In answer to this Explication I have in my Examen propos'd divers things, which you may there meet with: And indeed his Explication has appear'd so improbable to those that have written of this Experi­ment, that I have not found it em­brac'd by any of them, though, when divers of them oppos'd it, the Phaenomena of our Engine were not yet divulg'd. Not then needlesly to repeat what has been said already, I shall on this occasion only add one Experiment, that I afterwards made, and it was this: Having made the Torricellian Experiment (in a straight Tube) after the ordinary way, we took a little piece of a fine Bladder, and raising the Pipe a little in the stagnant Mercury, but not so high [Page 65] as the surface of it, the piece of Blad­der was dexterously conveyed in the Quicksilver, so as to be applied by ones finger to the immersed orifice of the Pipe, without letting the Air get into the Cavity of it; then the Blad­der was tyed very straight and care­fully to the lower end of the Pipe, whose orifice (as we said) it cover'd before, and then the Pipe being slow­ly lifted out of the stagnant Mer­cury, the impendent Quicksilver ap­pear'd to lean but very lightly upon the Bladder, being so near an exact AEquilibrium with the Atmosperical Air, that, if the Tube were but a very little inclin'd, whereby the gravita­tion of the Quicksilver, being not so perpendicular, came to be some­what lessen'd, the Bladder would immediately be driven into the ori­fice of the Tube, and to the Eye, plac'd without, appear to have ac­quir'd a concave superficies instead of the convex it had before. And when the Tube was re-erected, the Bladder would no longer appear [Page 66] suck'd in, but be again somewhat protuberant. And if, when the Mercury in the Pipe was made to de­scend a little below its station into the stagnant Mercury, if, I say, at that nick of time the piece of Blad­der were nimbly and dexterously ap­ply'd, as before, to the immers'd o­rifice, and fasten'd to the sides of the Pipe, upon the lifting the Instrument out of the stagnant Mercury, the Cylinder of that Liquor being now somewhat short of its due height, was no longer able fully to counter­poise the weight of the Atmosphe­rical Air, which consequently, though the Glass were held in an erected po­sture, would press up the Bladder in­to the orifice of the Pipe, and both make and maintain there a Cavity sensible both to the Touch and the Eye.

A.

What did you mainly drive at in this Experiment?

B.

To satisfie some Ingenious Men, that were more diffident of, than skilful in, Hydrostaticks, that [Page 67] the pressure of the external Air is ca­pable of sustaining a Cylinder of 29 or 30 Inches of Mercury, and upon a small lessening of the gravitation of that ponderous liquor, to press it up higher into the Tube. But a far­ther use may be made of it against Mr. Hobbes's pretention. For, when the Tube is again erected, the Mer­cury will subside as low as at first, and leave as great a space as former­ly was left deserted at the top; into which how the Air should get to fill it, will not appear easie to them, that, like you and me, know by ma­ny tryals, that a Bladder will rather be burst by Air than grant it passage. And if it should be pretended, either that some Air from without had yet got through the Bladder, or that the Air, that they may presume to have been just before included between the Bladder and the Mercury, made its way from the lower part of the In­strument to the upper; 'tis obvious to answer, That 'tis no way likely, that it should pass all along the Cy­linder [Page 68] unseen by us; since, when there are really any Aerial Bubbles, though smaller than Pins heads, they are easily discernible. And in our case, there is no such resistance of the Air to the ascension of the stagnant Mercury, as Mr. Hobbes pretends in the Torricellian Experiment made the usual way.

A.

But, whatever becomes of Mr. Hobbes's Explication of the Phae­nomenon; yet may not one still say, that it affords no advantage to the Vacuists against him?

B.

Whether or no it do against other Plenists, I shall not now consi­der; but I doubt, the Vacuists will tell Mr. Hobbes, that he is fain in two places of the Explication, we have read, to suppose the Plenitude of the World, that is, to beg the thing in question, which 'tis not to be pre­sum'd they will allow.

A.

But may not Mr. Hobbes say, that 'tis as lawful for him to sup­pose a Plenum, as for them to suppose a Vacuum.

B.
[Page 69]

I think he may justly say so; but 'tis like they will reply, that, in their way of explicating the Tor­ricellian Experiment, they do not suppose a Vacuum as to Air, but prove it. For they shew a great space, that having been just before fill'd with Quicksilver, is now deserted by it, though it appeared not, that any Air succeeded in its room; but rather, that the upper end of the Tube is ei­ther totally or near totally so devoid of Air, that the Quicksilver may without resistance, by barely incli­ning the Tube, be made to fill it to the very top: Whereas Mr. Hobbes is fain to have recourse to that which he knows they deny, the Plenitude of the World, not proving by any sensible Phaenomena, that there did get in through the Quicksilver Air enough to fill the deserted part of the Tube, but only concluding, that so much Air must have got in there, because, the World being full, it could find no room any where else; which the Vacuists will take for no [Page 70] proof at all, and the Cartesians, though Plenists, who admit an Etherial mat­ter capable of passing through the pores of Glass, will, I doubt, look upon but as an improper Explication.

A.

I remember on this occasion another Experiment of yours, that seems unfavourable enough to Mr. Hobbes's Explication, and you will perhaps call it to mind when I tell you, that 'twas made in a bended Pipe almost fill'd with Quicksilver.

B.

To see whether we understand one another, I will briefly describe the Instrument I think you mean. We took a Cylindrical Pipe of Glass, clos'd at the upper end, and of that length, that being dexterously bent at some Inches from the bottom, the shorter legg was made as parallel as we could to the longer: In this Glass we found an expedient, (for 'tis not easie to do,) to make the Torricellian Experiment, the Quicksilver in the shorter legg serving instead of the stagnant Quicksilver in the usual Ba­roscope, and the Quicksilver in the [Page 71] longer legg reaching above that in the shorter about eight or nine and twenty Inches. Then, by another artifice, the shorter legg, into which the Mercury did not rise within an Inch of the top, was so order'd, that it could in a trice be Hermetically seal'd, without disordering the Quick­silver. And this is the Instrument that I ghess you mean.

A.

It is so, and I remember, that it is the same with that, which in the Paradox about Suction you call, whilst the shorter legg remains un­seal'd, a Travelling Baroscope. But when I saw you make the Experi­ment, that legg was Hermetically seal'd, an Inch of Air in its natural or usual consistence being left in the upper part of it, to which Air you outwardly applied a pair of heated Tongs.

B.

Yet that, which I chiefly aim'd at in the Trial, was not the Phaeno­menon I perceive you mean; for, my design was, by breaking the Ice for them, to encourage some, that may [Page 72] have more skill and accommodation than I then had, to make an attempt that I did not find to have been made by any; namely, to reduce the Ex­pansive force of Heat in every way included Air, if not in some other Bodies also, to some kind of measure, and, if 'twere possible, to determin it by weight. And I presumed, that at least the event of my Tryal would much confirm several Explications of mine, by shewing, that Heat is able, as long as it lasts, very considerably to increase the Spring or pressing power of the Air. And in this con­jecture I was not mistaken; for, ha­ving shut up, after the manner new­ly recited, a determinate quantity of uncomprest Air, which, (in the Ex­periment you saw,) was about one Inch; we warily held a pair of hea­ted Tongs near the outside of the Glass, (without making it touch the Instrument, for fear of breaking it,) whereby the Air being agitated was enabled to expand it self to double its former Dimensions, and conse­quently [Page 73] had its Spring so strengthen'd by Heat, that it was able to raise all the Quicksilver in the longer legg, and keep up or sustain a Mercurial Cylinder of about nine and twenty Inches high, when by its expansion it would, if it had not been for the Heat, have lost half the force of its elasticity. But whatever I design in this Experiment, pray tell me, what use you would make of it a­gainst Mr. Hobbes.

A.

I believe, he will find it very difficult to shew, what keeps the Mercury suspended in the longer legg of the Travelling Baroscope, when the shorter legg is unstopt, at which it may run out; since this Instrument may, as I have try'd, be carried to distant places, where it cannot with probability be pretended, that any Air has been displac'd by the fall of the Quicksilver in the longer legg, which perhaps fell long before above a mile off. And when the shorter legg is seal'd, it will be very hard for Mr. Hobbes to shew there the odd [Page 74] motions of the Air, to which he as­cribes the Torricellian Experiment. For, if you warily incline the Instru­ment, the Quicksilver will rise to the top of the longer legg, and imme­diately subside, when the Instrument is again erected, and yet no Air ap­pears to pass through the Quicksilver interpos'd between the ends of the longer and the shorter legg. But that which I would chiefly take notice of in the Experiment, is, that upon the external application of a hot Bo­dy to the shorter legg of the Baros­cope, when 'twas seal'd up, the in­cluded Air was expanded from one Inch to two, and so rais'd the whole Cylinder of Mercury in the longer legg, and, whilst the heat continued undiminished, kept it from subsiding again. For, if the Air were able to get unseen through the body of the Quicksilver, why had it not been much more able, when rarified by Heat, to pass through the Quick­silver, than for want of doing so to raise and sustain so weighty a Cylin­der [Page 75] of Mercury? I shall not stay to in­quire on this occasion, how Mr. Hobbes will, according to his Hypothesis, ex­plicate the rarefaction of the Air to double its former dimensions, and the condensation of it again; espe­cially since, asserting that part of the upper legg, that is unfill'd with the Quicksilver, to be perfectly full of Air, he affirms that, which I doubt he cannot prove, and which may very probably be disproved by the Experiment you mention in the Dis­course about Suction, where you shew, to another purpose, that in a Tra­velling Baroscope, whose shorter legg is seal'd, if the end of the longer legg be open'd, whereby it comes indeed to be fill'd with Air, the pressure of that Air will enable the subjacent Mercury notably to com­press the Air included in the shorter legg.

B.

I leave Mr. Hobbes to consider what you have objected against his Explication of the Torricellian Ex­periment; to which I shall add no­thing, [Page 76] though perhaps I could add much, because I think it may be well spared, and our Conference has la­sted long already.

A.

I will then proceed to the la [...] Experiment recited by Mr. Hobbes in his Problemata de Vacuo.

A.

Si Phialam, collum habent [...] longiusculum, ea [...]démque omni Corpor [...] praeter Aerem vacuam ore sugas, con­tinuoque Phialae os aquae immergas, vi­debis aquam aliquousque ascendere in Phi­alam. Quî fieri hoc potest nisi factum sit Vacuum ab exuctione Aeris, in euj [...] locum possit Aqua illa ascendere?

B.

Concesso Vacuo, oportet quaeda [...] l [...]cae vacua fuisse in illo Aere, etiam qu [...] erat intra Phialam ante suctionem. C [...] ergo non ascendebat Aqua ad ea imple [...] ­da absque suctione? Is qui sagit Phi [...] ­lam, neque in ventrem quicquam, neq [...] in pulmones, neque in os è Phialu ex [...] ­git. Quid ergo agit? Aerum comm [...] ­vet, & in partibus ejus conatum sugen [...] efficit per os exeundi, & non admitten­do, conaetum redeundi. Ab his conati­bus contrariis compo [...]tur circumitio in [...] [Page 77] Phialam, & conatus exeundi quaqua­versum. Itaque Phialae ore aquae im­merso, Aer in subjectam aquam penetrat è Phiala egrediens, & tuntundem aquae in Phialam cogit.

Praeterea vis illa magna suctionis facit, ut sugentis labra c [...]m collo Phialae aliquando arctissimè cohaereant propter contactum exqusitissimum.

B.

As to the first Clause of Mr. Hobbes's account of our Phaeno­menon, the Vacuists will easily an­swer his Question by acknowledging, that there were indeed interspers'd Vacuities in the Air contain'd in the Vial before the suction; but they will add, there was no reason, why the Water should ascend to fill them, be­cause, being a heavy body, it can­not rise of it self, but must be raised by some prevalent weight or pres­sure, which then was wanting. Be­sides, that there being interspers'd Vacuities as well in the rest of the Air that was very near the Water, as in that contained in the Vial, there was no reason, why the Water [Page 78] should ascend to fill the Vacuities of one portion of Air rather than those of another. But when once by su­ction a great many of the Aerial Corpuscles were made to pass out of the Vial, the Spring of the remain­ing Air being weaken'd, whilst the pressure of the ambient Air, which depends upon its constant Gravity, is undiminished, the Spring of the internal becomes unable to resist the weight of the external Air, which is therefore able to impel the inter­pos'd Water with some violence into the Cavity of the Glass, 'till the Air, remaining in that Cavity, being reduced almost to its usual Density, is able by its Spring, and the weight of the Water got up into the Vial, to hinder any more Water from be­ing impell'd up. For, as to what Mr. Hobbes affirms, that, Is qui su­git Phialam neque in ventrem quic­quam, neque in pulmones, neque in as quicquam exugit: How it will agree with what he elsewhere delivers a­bout Suction, I leave him to consider. [Page 79] But I confess, I cannot but wonder at his confidence, that can positive­ly assert a thing so repugnant to the common sentiments of Men of all opinions, without offering any proof for it. But I suppose, they that are by tryal acquainted with Sucking, and have felt the Air come in at their mouths, will prefer their own expe­rience to his authority. And as to what he adds, that the Person that sucks agitates the Air, and turns it within the Vial into a kind of circu­lating wind, that endeavours every where to get out; I wish, he had shewn us by what means a Man that sucks makes this odd Commotion of the Air; especially in such Vials as I use to employ about the Experiment, the orifice of whose neck is sometimes less than a Pins head.

A.

That there may be really Air extracted by Suction out of a Glass, me thinks you might argue from an Experiment I saw you make with a Receiver which was exhausted by your Pump, and consequently by Su­ction. [Page 80] For I remember, when you had counterpois'd it with very good Scales, and afterwards by turning a stop-cock, let in the outward Air, there rush'd in as much Air to fill the space that had been deserted by the Air pump [...] out, as weighed some scruples (consisting of twenty grains a piece) though the Receiver were not of the largest size.

B.

You did well to add that Clause; for, the Magdeburgic Ex­periment, mentioned by the industri­ous Schottus, having been made with a vast Receiver, the readmitted Air amounted to a whole ounce and some drachms. But to return to Mr. Hobbes, I fear not that he will perswade you, that have seen the Experiment he re­cites, that as soon as the neck of the Vial is unstopt under water, the Air, that whirl'd about before, makes a sally out, and forces in as much wa­ter. For, if the orifice be any thing large, you will, instead of feeling an endeavour to thrust away your finger that stopt it, find the pulp of [Page 81] your finger so thrust inward, that a Peripatetick would affirm that he felt it suckt in. And that Intrusion may be the Reason, why the lip of him that sucks is oftentimes strongly fa­sten'd to the orifice of the Vials neck, which Mr. Hobbes ascribes to a most exquisit contact, but without clear­ly telling us, how that extraordina­ry contact is effected. And when your finger is removed, instead of perceiving any Air go out of the Vial through the water, (which, if any such thing happen, you will easily discover by the bubbles,) you shall see the water briskly spring up in a slender stream to the top of the Vial, which it could not do, if the Cavity were already full of Air. And to let you see, that, when the Air does really pass in or out of the Vial im­mers'd under water, 'tis very easie to perceive its motions, if you dip the neck of the Vial in water, and then apply to the globulous part of it either your warm hands or any other competent Heat, the internal [Page 82] Air being rarified; you shall see a por­tion of it, answerable to the degree of Heat you applied, manifestly pass through the water in successive bub­bles, whilst yet you shall not see a­ny water get into the Vial to supply the place deserted by that Air. And if, when you have (as you may do by the help of sucking) fill'd the neck and part of the belly of the Vial with water, you immerse the orifice into stagnant water, and ap­ply warm hands to the globulous part as before, you will find the water in the Vial to be driven out, before any bubbles pass out of the Vial into the surrounding water; which shews, that the Air is not so forward to dive under the water, (and much less un­der so ponderous a liquor as Quick­silver,) as Mr. Hobbes has supposed.

A.

That 'tis the Pressure of the external Air, that (surmounting the Spring of the internal) drives up the water into the Vial we have been speaking of, does, I confess, follow upon your Hypothesis: But an Expe­rimentarian [Page 83] Philosopher, as Mr. Hobbes calls you among others, may possi­bly be furnished with an Experiment to confirm this to the Eye.

B.

You bring into my mind what I once devised to confirm my Hypo­thesis about Suction, but found a while since that I had omitted it in my Discourse about that Subject. And therefore I shall now repeat to you the substance at least of the Me­morial that was written of that Ex­periment, by which the great inte­rest of the weight of the Atmosphe­rical Air in Suction will appear, and in which also some things will oc­cur, that will not well agree with Mr. Hobbes's Explication, and pre­vent some of his Allegations against mine.

A.

Having not yet met with an Experiment of this nature, such an one as you speak of will be welcome to me.

B.

We took a Glass Bubble, whose long stem was both very slender and very Cylindrical; then by applying [Page 84] to the outside of the Ball or globu­lous part a convenient heat, we ex­pell'd so much of the Air, as that, when the end of the pipe was dipt in water, and the inward Air had time to recover its former coolness, the water ascended either to the top of the pipe or very near it. This done, we gently and warily rarified the Air in the Cavity of the Bubble, 'till by its expansion it had driven out almost all the water that had got up into the stem, that so it might attain as near as could be to that degree of heat and measure of expansion, that it had when the water began to rise in it. And we were careful to leave two or three drops of water unex­pell'd at the bottom of the pipe, that we might be sure, that none of the included Air was by this second ra­refaction driven out at the orifice of it; as the depression of the water so low assured us, on the other side, that the included Air wanted nothing considerable of the expansion it had when the water began to ascend into [Page 85] the pipe. Whilst the Air was in this rarified state, we presently removed the little Instrument out of the stag­nant water into stagnant Quicksil­ver, which in a short time began to rise in the pipe. Now, if the ascen­sion of the liquor were the effect of Natures Abhorrence of a Vacuum; or of some internal principle of Motion; or of the Compression and propaga­ted Pulsion of the outward Air by that which had been expell'd; why should not the Mercury haue ascended to the top of the pipe, as the water did before? But de facto it did not ascend half, or perhaps a quarter so far; and if the pipe had been long e­nough, as well as 'twas slender e­nough, I question, whether the Mer­cury would have ascended (in pro­portion to the length of the stem) half so high as it did.

Now of this Experiment, which we tryed more than once, I see not, for the reason lately express'd, how any good account will be given with­out our Hypothesis, but according to That 'tis clear.

A.
[Page 86]

I think I perceive why you say so; for the Ascension of Liquors being an effect of the prevalency of the external Airs pressure against the resistance it meets with in the Ca­vity of the Instrument, and the Quick­silver being bulk for bulk many times heavier than water, the same sur­plusage of pressure that was able to impel up water to the top of the pipe, ought not to be able to impel up the Quicksilver to any thing near that height. And if it be here ob­jected, as it very plausibly may be, that the raised Cylinder of Mercury was much longer than it ought to have been in reference to a Cylinder of Water, the proportion in gravity between those two Liquors (which is almost that of fourteen to one) be­ing considered; I answer, that when the Cylinder of Water reach'd to the pipe, the Air possess'd no more than the Cavity of the globulous part of the Instrument, being very little assisted to dilate it self by so light a Cylin­der as that of Water: But when [Page 87] the Quicksilver came to be impell'd into the Instrument by the weight of the external Air, that ponderous Bo­dy did not stop its ascent as soon as it came to be equiponderant to the formerly expell'd Cylinder of Wa­ter; because, to attain that height, it reached but a little way into the pipe, and left all the rest of the Ca­vity of the pipe to be fill'd with part of that Air, which formerly was all s [...]ut up in the Cavity of the Bubble; by which means the Air, included in the whole Instrument, must needs be in a state of expansion, and there­by have its Spring weakened, and consequently disabled to resist the pressure of the external Air, as much as the same included Air did before, when it was less rarified; on which account, the undiminished weight or pressure of the external Air was able to raise the Quicksilver higher and higher, 'till it had obta [...]ned that height, at which the pressure, com­pounded of the weight of the Mer­curial Cylinder and the Spring of the [Page 88] internal Air (now less rarified than before,) was equivalent to the pres­sure of the Atmosphere or external Air.

B.

You have given the very Ex­plication I was about to propose; wherefore I shall only add, that to confirm this Experiment by a kind of Inversion of it, we drove by heat a little Air out of the Bubble, and dipt the open end of the pipe into Quicksilver, which by this means we made to ascend 'till it had fill'd about a fourth part or less of the pipe, when that was held erected. Then carefully removing it without letting fall any Quicksilver, or let­ting in any Air, we held the orifice of the pipe a little under the surface of a Glass full of Water, and ap­plying a moderate heat to the outside of the Ball, we warily expell'd the Quicksilver, yet leaving a little of it to make it sure that no Air was driven out with it, then suffering the included Air to cool, the exter­nal Air was found able to make the [Page 89] Water not only ascend to the very top of the pipe, and thence spread it self a little into the Cavity of the Ball, but to carry up before it the Quicksilver that had remained unex­pell'd at the bottom of the stem. And if in making the Experiment we had first raised, as we sometimes did, a greater quantity of Quick­silver, and afterwards drove it out, the quantity of Water, that would be impell'd into the Cavity of the pipe and ball, would be accordingly increased.

A.

In this Experiment 'tis mani­fest, that something is driven out of the Cavity of the Glass before the Water or Quicksilver begins to ascend in it: And here also we see not, that the Air can pass through the pores of Quicksilver or Water, but that it drives them on before it, with­out sensibly mixing with them. In this Experiment there appears not at all any Circular Wind, as Mr. Hobbes fancies in the suckt Vial we are dispu­ting of, nor any tendency outwards [Page 90] of the included Air upon the account of such a Wind; but, instead of these things, that the ascension of the Liquors into the Cavity of the pipe depends upon the external Air, pres­sing up the Liquors into that Cavity, may be argu'd by this, that the same weight of the Atmosphere im­pell'd up into the pipe so much more of the lighter Liquor, Water, than of the heavier Liquor, Mercury.

B.

You have said enough on this Experiment; but 'tis not the only I have to oppose to Mr. Hobbes his Ex­plication: For, that there is no need of the sallying of Air out of a Vial, to make the Atmospherical Air press against a Body that closes the orifice of it, when the pressure of the inter­nal Air is much weakened; I have had occasion to shew some Virtuosi, by sucking out, with the help of an In­strument, a considerable portion of the Air contained in a Glass; for ha­ving then, instead of unstopping the orifice under water, nimbly applied a flat Body to it, the external Air press'd [Page 91] that Body so forcibly against it, as to keep it fastened and suspended, though 'twere clogg'd with a weight of ma­ny ounces.

A.

Another Experiment of yours Mr. Hobbes's Explication brings into my mind, by which it appears, that, if there be such a Circular Wind, as he pretends, produced by Suction in the Cavity of the Vial, it must needs be strangely lasting. For I have seen more than once, that, when you have by an Instrument suckt much of the Air out of a Vial, and afterwards carefully closed it, though you kept the slender neck of it stopt a long time, perhaps for some weeks or months, yet when 'twas open'd under water, a considerable quantity of the Liquor would be briskly impell'd up into the neck and belly of the Vial. So that, though I will not be so plea­sant with Mr. Hobbes, as to mind you on this occasion of those Writers of Natural Magick, that teach us to shut up Articulate Sounds in a Vessel, which being transported to a distant [Page 92] place and open'd there, will rende [...] the Words that are committed to it [...] yet I must needs say, that so lasting a Circular Wind, as, according to Mr. Hobbes, your Experiments exhibi­ted, may well deserve our wonder.

B.

Your admiration would per­chance increase, if I should assure you, that having with the Sun-beams produced smoak in one of those well-stopt Vials, this Circular Wind did not at all appear to blow it about, but suffered it to rise, as it would have done if the included Air had been ve­ry calm. And now I shall add but one Experiment more, which will not be liable to some of the things as inva­lid as they are, which Mr. Hobbes has alledged in his account of the Vial, and which will let you see, that the weight of the Atmospherical Air is a very considerable thing; and which may also incline you to think, that, whilst Mr. Hobbes does not admit a sub­tiler Matter than common Air to pass through the Pores of close and solid Bodies, the Air he has recourse to will [Page 93] sometimes come too late to prevent a Vacuum. The Experiment, which was partly accidental, I lately found regi­stred to this sense, if not in these words: [Having, to make some Discovery of the weight of the Air, and for other purposes, caus'd an AEolipile, very light considering its bulk, to be made by a famous Artist, I had occasion to put it so often into the fire for several Tryals, that at length the Copper scal'd off by degrees, and left the Vessel much thin­ner than when it first came out of the Artificers hands; and a good while af­ter, this change in the Instrument be­ing not in my thoughts, I had occasion to imploy it, as formerly, to weigh how many grains it would contain of the Air at such a determinate constitution of the Atmosphere, as was to be met with, where I then chanced to be. For the making this Experiment the more exactly, the Air was by a strong, but warily applied, fire so carefully driven away, that, when clapping a piece of Sealing-wax to the Pin-hole, at which it had been forced out, we hindred any [Page 94] communication betwixt the Cavity of the Instrument and the external Air, we suppos'd the AEolipile to be very well exhausted, and therefore laid it by, that, when it should be grown cold, we might, by opening the orifice with a Pin, again let in the outward Air, and observe the encrease of weight that would thereupon ensue: But the In­strument, that, as I was saying, was grown thin, had been so diligently freed from Air, that the very little that remain'd, and was kept by the War from receiving any assistance from without, being unable by its Spring to assist the AEolipile to support the weight of the ambient Air; this exter­nal fluid did by its weight press against it so strongly, that it compress'd it, and thrust it so considerably inwards, and in more than one place so chang'd its figure, that, when I shew'd it to the Virtuosi that were assembled at Gresham-Colledge, they were pleased to command it of me to be kept in their Reposi­tory, where I presume it is still to be seen.

FINIS.
OF THE CAUSE OF Attr …

OF THE CAUSE OF Attraction BY SUCTION.

By the Honourable ROBERT BOYLE, Fellow of the Royal Society.

LONDON, Printed by William Godbid, and are to be Sold by Moses Pitt, at the Angel over against the little North Door of St. Paul's Church. 1674.

PREFACE.

HAving about twelve years ago summarily exprest and pub­lish'd my Opinion of the Cause of Suction, and a while be­fore or after brought to the Royal Society the Glass Instrument I employ'd to make it out; I desisted for some time to add any thing about a Problem, that I had but occa­sionally handled: Only, because the Instru­ment I mention'd in my Examen of Mr. Hobbes's Opinion, and afterwards us'd at Gresham-College, was difficult enough to be well made, and not to be pro­cur'd ready made, I did for the sake of some Virtuosi, that were curious of such things, devise a slight and easily made Instrument, describ'd in the following Tract, Chap. 4 th, in which the chief Phae­nomena, I shew'd before the Society, were easily producible. But afterwards the mistakes and erroneous Opinions, [Page] that, in Print as well as in Discourse, I met with, even among Learned Men, about Suction, and the Curiosity of an Ingenious Person, engaged me to resume that Subject and treat of it, as if I had never before meddled with it, for the reason intimated in the beginning of the insuing Paper. And finding upon the re­view of my later Animadversions an Mr. Hobbes's Problemata de Vacuo, that some passages of this Tract are re­ferr'd to there; I saw my self thereby little less than engaged to annex that Discourse to those Animadversions. And this I the rather consented to, because it contains some Experiments, that I have not elsewhere met with, which, together with some other parts of that Essay, may, I hope, prove of some use to illustrate and confirm our Doctrine about the Weight and Spring of the Air, and supply the less experienced than ingenious. Friends to our Hypothesis with more grounds of answering the later Objections of some Learned Men, against whose endeavours I perceive it will be useful to employ va­riety of Experiments and other Proofs to [Page] evince the same Truth; that some or other of these may meet with those Ar­guments or evasions with which they strive to elude the force of the rest.

The Title of the following Essay may sufficiently keep the Reader from expecting to find any other kind of Attraction dis­cours'd of, than that which is made by Suction. But yet thus much I shall here intimate in general, that I have found by Trials purposely made, that the Examples of Suction are not the only noted ones of Attraction, that may be reduced to Pulsion.

OF THE CAUSE OF ATTRACTION BY SUCTION.

CHAP. I.

I Might, Sir, save my self some trouble in giving you that ac­count you desire of me about Suction, by referring you to a passage in the Examen, I long since writ, of Mr. Hobbes's Dialogus Physicus de Natura Aeris, if I knew, you had those two Books lying by you. But because I suspect, that my Examen [Page 2] may not be in your hands, since 'tis a most out of Print, and has not for some years been in my own; and be­cause I do not so well remember, after so long a time the particulars that I writ there, about Suction, as I do in general, that the Hypothesis I pro­posed, was very incidentally and briefly discours'd of, upon an occa­sion ministred by a wrong Explication given of Suction by Mr. Hobbes, I shall here decline referring you to what I there writ [...] and proposing to you those thoughts about Suction, that I remember I there pointed at, I shall annex some things to illustrate and confirm them; that would not have been so proper for me to have insisted on in a short and but occa­sional Excursion.

And I should immediately proceed to what you expect from me, but that Suction being generally look'd upon as a kind of Attraction, it will be requisite for me to premise some­thing about Attraction it self. For, besides that the Cause of it, which [Page 3] I here dispute not of, is obscure, the very Nature and Notion of it is wont by Naturalists to be either left un­touch'd, or but very darkly deliver'd, and therefore will not be unfit to be here somewhat explain'd.

How general and ancient soever the common Opinion may be, that Attraction is a kind of Motion quite differing from Pulsion, if not also op­posite to it; yet I confess, I concur in opinion, though not altogether upon the same grounds, with some modern Naturalists, that think At­traction a Species of Pulsion. And at least among inanimate Bodies I have not yet observed any thing, that convinces me, that Attraction cannot be reduced to Pulsion; for, these two seem to me to be but extrinsical deno­minations of the same Local Motion, in which, if a moved Body precede the Movent, or tend to acquire a greater distance from it, we call it Pulsion; and if, upon the score of the Motion, the same Body follow the Mo­vent or approach to it, we call it [Page 4] Attraction. But this difference may consist but in an accidental respect, which does not Physically alter the na­ture of the Motion, but is founded upon the respect, which the Line, wherein the Motion is made, happens to have to the situation of the Mo­vent. And that which seems to me to have been the chief cause of mens mistaking Attraction for a motion op­posite to Pulsion, is, that they have look'd upon both the moving and moved Bodies, in too popular and su­perficial a manner; and consider'd in the Movent rather the situation of the conspicuous and more bulky part of the Animal or other Agent, than the situation of that part of the Animal, or Instrument, that does immediately impress that motion up­on the Mobile.

For those that attentively heed this, may easily take notice, that some part of that Body, or of the Instrument, which by reason of their conjunction in this operation is to be look'd on but as making one with it, is really [Page 5] placed behind some part of the Body to be drawn, and therefore cannot move outwards it self without thru­sting that Body forward. This will be easily understood, if we consider, what happens when a Man draws a Chain after him; for, though his Body do precede the Chain, yet his finger or some other part of the hand, wherewith he draws it, has some part or other that reaches behind the fore part of the first Link, and the hinder part of this Link comes be­hind the anteriour part of the se­cond Link; and so each Link has one of its parts placed behind some part of the Link next after it, 'till you come to the last Link of all. And so, as the finger, that is in the first Link, cannot move forwards but it must thrust on that Link, by this Series of Trusions the whole Chain is moved forwards; and if any other Body be drawn by that Chain, you may per­ceive, that some part of the last Link comes behind some part of that Bo­dy, or of some intervening Body, [Page 6] which, by its cohesion with it, ought in our present case to be consider'd as part of it. And thus Attraction seems to be but a Species of Pulsion, and u­sually belongs to that kind of it, which, for distinctions sake, is cal­led Trusion, by which we understand that kind of Pulsion, wherein the Movent goes along with the moved Body without quitting it whilst the progress lasts; as it happens, when a Gardiner drives his Wheel-barrow before him without letting go his hold of it.

But I must not here dissemble a dif­ficulty, that I foresee may be speci­ously urged against this account of Attraction. For it may be said, that there are Attractions, where it can­not be pretended, that any part of the Attrahent comes behind the At­tracted Body; as in Magnetical and Electrical Attractions, and in that which is made of Water, when 'tis drawn up into Springs and Pumps.

I need not tell you, that you know so well, as that partly the Cartesians, [Page 7] and partly other Modern Philoso­phers, have recourse on this occa­sion either to screwed Particles and other Magnetical Emissions, to ex­plicate Phaenomena of this kind. And, according to such Hypotheses, one may say, that many of these Magnetical and Electrical Effluvia come behind some parts of the attracted Bodies, or at least of the little solid Particles, that are as it were the Walls of their [...]ores, or procure some discussion of the Air, that may make it thrust the Moveable towards the Loadstone or Amber, &c. But if there were none of these, nor any other subtil Agents that cause this Motion by a real, though unperceived, Pulsion; I should make a distinction betwixt other At­tractions and these, which I should then stile Attraction by Invisibles. But, whether there be really any such in Nature, and why I scruple to admit things so hard to be concei­ved, may be elsewhere consider'd. And you will, I presume, the free­lier allow me this liberty, if, (since [Page 8] in this place 'tis proper to do it,) I shew you, that in the last of the in­stances I formerly objected (that of the drawing up of Water into the Barrel of a Syringe,) there is no true Attraction of the Liquor made by the external Air. I say then, that by the ascending Rammer, as a part of which I here consider the obtuse end, Plug, or Sucker, there is no Attra­ction made of the contiguous and sub­jacent Water, but only there is room made for it, to rise into, without being expos'd to the pressure of the superiour Air. For, if we suppose the whole Rammer to be by Divine Omnipotence annihilated, and con­sequently uncapable of exercising any Attraction; yet, provided the supe­riour Air were kept off from the Wa­ter by any other way as well as 'twas by the Rammer, the Liquor would as well ascend into the Cavity of the Barrel; since, (as I have else­where abundantly proved,) the sur­face of the Terraqueous Globe being continually press'd on by the incum­bent [Page 9] Air or Atmosphere, the Water must be by that pressure impell'd into any cavity here below, where there is no Air to resist it; as by our Sup­position there is not in the Barrel of our Syringe, when the Rammer, or whatever else was in it, had been annihilated. Which Reasoning may be sufficiently confirm'd by an Expe­riment, whereby I have more than once shewn some curious persons, that, if the external Air, and conse­quently its pressure, be withdrawn from about the Syringe, one may pull up the Sucker as much as he pleases, without drawing up after it the subjacent Water. In short, let us suppose, that a Man standing in an inner room does by his utmost re­sistance keep shut a Door, that is neither lock'd nor latch'd, against another, who with equal force en­deavours to thrust it open? In this case, as if one should forcibly pull away the first Man, it could not be said, that this Man, by his recess from the Door he endeavoured to [Page 10] press outwards, did truely and pro­perly draw in his Antagonist, though upon that recess the coming in of his Antagonist would presently ensue; so it cannot properly be said, that by the ascent of the Rammer, which displaces the superiour Air, either the Rammer it self, or the expelled Air, does properly attract [...] the subjacent Water, though the ingress of that Liquor into the Barrel does there­upon necessarily ensue. And that, as the Comparison supposes, there is a pressure of the superiour Air against the upper part of the Sucker, you may easily perceive, if having well stopt the lower orifice of the Syringe with your finger, you forcibly draw up the Sucker to the top of the Bar­rel. For if then you let go the Ram­mer, you will find it impell'd down­wards by the incumbent Air with a notable force.

CHAP. II.

HAving thus premis'd something in general about the Nature of Attraction, as far as 'tis necessary for my present design; it will be now seasonable to proceed to the conside­ration of that kind of Attraction, that is employed to raise Liquors, and is by a distinct Name called Suction.

About the Cause of this there is great comention between the New Philosophers; as they are stiled, and the Peripateticks. For the Followers of Aristotle, and many Learned Men that in other things dissent from him, ascribe the ascension of Liquors upon Suction to Natures abhorrence of a Vacuum. For, say they, when a Man dips one end of a Straw or Reed into stagnant Water, and sucks at the other end, the Air contain'd in the cavity of the Reed passes into that [Page 12] of his Lungs, and consequently the Reed would be left empty, if no o­ther Body succeeded in the place it deserts; but there are only (that they take notice of,) two Bodies that can succeed, the Air and the (grosser Li­quor) the Water; and the Air can­not do it, because of the interposi­tion of the Water, that denies it ac­cess to the immers'd orifice of th [...] Reed, and therefore it must be the Water it self, which accordingly does ascend to prevent a Vacuum detested by Nature.

But many of the Modern Philoso­phers, and generally all the Corpusc [...] ­larians, look upon this Fuga Vacue as but an imaginary Cause of Suction; though they do it upon very differing grounds. For, the Atomists; tha [...] willingly admit of Vacuities, pro­perly so called, both within and without our World, cannot think that Nature hates or fears a Vacuum, and declines her usual course to pre­vent it: And the Cartesians, though they do, as well as the Peripateticks, [Page 13] deny that that there is a Vacuum, yet since they affirm not only, that there is none in rerum Natura, but that there can be none, because what o­thers call an empty Space having three Dimensions, hath all that they think belonging to the Essence of a Body, they will not grant Nature to be so indiscreet, as to strain her self to prevent the making of a thing that is impossible to be made.

The Peripatetic Opinion about the Cause of Suction, though commonly defended by the Schools, as well Mo­dern as Ancient, supposes in Nature such an abhorrence of a Vacuum, as neither has been well proved, nor does well agree with the lately disco­ver'd Phaenomenon of Suction. For, according to their Hypothesis, Water and other Liquors should ascend upon Suction to any hight to prevent a Va­cuum, which yet is not agreeable to experience. For I have carefully tryed, that by pumping with a Pump far more stanch than those that are usually made, and indeed as well [Page 14] clos'd as we could possibly bring it to be, we could not by all our endeavour [...] raise Water by Suction to above See Cont. of Phys. Mech. Exp. the 15 th Exp. 36 ½ foot. The T [...]r­ricellian Exp t shews, tha [...] the weight of the Air is able to sustain, and some of our Experim ts shew, 'tis able to raise a Mercurial Cylinder e­qual in weight to as high a Cylinder of Water as we were able to raise by pumping. For Mercury being near [...] times as heavy as Water of the sam [...] bulk, if the weight of the Air b [...] equivalent to that of a Mercuri [...] Cylinder of 29 or 30 Inches, it mu [...] be able to counterpoise a Cylinder o [...] Water near fourteen times as long that is, from thirty four to near thirt [...] six foot. And very disagreeable t [...] the common Hypothesis, but conso­nant to ours, is the Experiment th [...] I have more than once tryed, and [...] think elsewhere deliver'd, namely [...] That, if you take a Glass Pipe of a [...]bout three foot long, and, dipping one end of it in Water, suck at the other, the Water will be suddenly [Page 15] made to flow briskly into your mouth: But, if instead of Water you dip the lower end into Quick­silver, though you suck as strongly as ever you can, provided that in this case, as in the former, you hold the Pipe upright, you will never be able to suck up the Quicksilver near so high as your mouth; so that if the Water ascended upon Suction to the top of the same Pipe, because else there would have been a Vacuum left in the cavity of it, why should not we conclude, that, when we have suckt up the Quicksilver as strongly as we can, as much of the upper part of the Tube as is deserted by the Air, and yet not fill'd by the Mercury, ad­mits, in part at least, a Vacuum, (as to Air) of which consequently Na­ture cannot reasonably be suppos'd to have so great and unlimited an abhor­rency, as the Peripateticks and their Adherents presume. Yet I will not determine, whether there be any more than many little Vacuities, or Spaces devoid of Air, in the Cavity; [Page 16] so called, of the Pipe unfill'd by the Mercury; (so that the whole Cavity is not one entire empty Space;) it being sufficient for my purpose, that my Experiment affords a good Argument ad hominem against the Peripateticks, and warrants us to seek for some o­ther Cause than the fuga Vacui, why a much stronger Suction than that, which made Water ascend with ease into the Suckers mouth, will not also raise Quicksilver to the same height or near it.

Those Modern Philosophers that admit not the fuga Vacui to be the Cause of the raising of Liquors in Suction, do generally enough agree in referring it to the action of the Suckers thorax. For, when a Man en­deavours to suck up a Liquor, he does by means of the Muscles enlarge the cavity of his Chest, which he can­not do but at the same time he must thrust away those parts of the ambi­ent Air that were contiguous to his Chest, and the displac'd Air does, according to some Learned Men, [Page 17] (therein, if I mistake not, Followers of Gassendus,) compress the contiguous Air, and that the next to it, and so outwards, 'till the pressure, succes­sively passing from one part of the Air to the other, arrive at the surface of the Liquor; and all other places being as to sense full, the impell'd Air cannot find place but by thrusting the Water into the room made for it in the Pipe by the recess of the Air that pass'd into the Suckers lungs. And they differ'd not much from this Ex­plication, that, without taking in the compression of the ambient Air made by the thorax, refer the Phaeno­menon to the propagated motion or impulse, that is imprest on the Air dis­plac'd by the thorax in its dilatation, and yet unable to move in a World perfectly fill'd, as they suppose ours to be, unless the Liquor be impell'd into as much of the cavity of the Pipe, as fast as 'tis deserted by the Air that is said to be suck'd up. But though I readily confess this Expli­cation to be ingenious, and such as I [Page 18] wonder not they should acquiess in, who are acquainted but with the long known and obvious Phaenomena of Suction; and though I am not sure, but that in the most familiar cases the Causes assign'd by them may contribute to the Effect; yet, preser­ving for Cartesius and Gassendus the respect I willingly pay such great Phi­losophers, I must take the liberty to tell you, that I cannot acquiess in their Theory. For I think, that the Cause of Suction, they assign, is in many cases not necessary, in others, not sufficient. And first, as to the Condensation of the Air by the dila­tation of the Suckers Chest; when I consider the extent of the ambient Air, and how small a compression no greater an expansion than that of the Thorax is like to make, I can scarce think, so slight a condensation of the free Air can have so conside­rable an operation on the surface of the Liquor to be rais'd, as the Hypo­thesis I examin requires: And that this impulse of the Air by a Suckers [Page 19] dilated Thorax, though it be wont to accompany the ascension of the wa­ter procured by Suction, yet is not of absolute necessity to it, will, I pre­sume, be easily granted, if it can be made out, that even a propagated Pulsion, abstracted from any Conden­sation of Air, is not so necessarily the Cause of it, but that the Effect may be produc'd without it. For suppose, that by Divine Omnipotence so much Air as is displac'd by the Thorax were annihilated; yet I see not, why the Ascension of the Liquor should not ensue. For, when a Man begins to suck, there is an AEquilibrium, or ra­ther AEquipollency between the pres­sure, which the Air, contained in the Pipe, (which is shut up with the pressure of the Atmosphere upon it,) has, by virtue of its Spring, upon that part of the surface of the water that is environ'd by the sides of the Pipe, and the pressure which the At­mospherical Air has, by virtue of its weight, upon all the rest of the sur­face of the stagnant water; so that, [Page 20] when by the dilatation of the Suc­kers Thorax, the Air within the ca­vity of the Pipe comes to be rarified, and consequently loose of its Spring, the weight of the external Air conti­nuing in the mean time the same, it must necessarily happen, that the Spring of the internal Air will be too weak to compress any longer the gravitation of the external, and con­sequently, that part of the surface of the stagnant water, that is included in the Pipe, being less press'd upon, than all the other parts of the same surfaces must necessarily give way, where it can least, resist, and conse­quently be impell'd up into the Pipe, where the Air, having had its Spring weakened by expansion, is no lon­ger able to resist, as it did before. This may be illustrated by somewhat varying an Instance already given, and conceiving, that within a Cham­ber three Men thrust all together with their utmost force against a Door, (which we suppose to have neither Bolt nor Latch) to keep it shut, at [Page 21] the same time the three other Men have just equal strength, and imploy their force to thrust it open. For though, whilst their opposite endea­vours are equal, the Door will con­tinue to be kept shut, yet if one of the three Men within the Room should go away, there will need no new force, nor other accession of strength to the three Men, to make them prevail and thrust open the Door against the resistance of those that endeavour'd to keep it shut, who are now but two.

And here (upon the by) you may take notice, that, to raise water in Suction, there is no necessity of any rarified and forcibly stretch'd Rope, as 'twere, of the Air, to draw up the subjacent water into the Pipe, since the bare debilitation of the Spring of the included Air may very well serve the turn. And though, if we should suppose the Air within the Pipe to be quite annihilated, it could not be pretended (since it would not have so much as Existence) that it exer­cises [Page 22] an attractive Power; yet in this case the water would ascend into the Pipe, without the assistance of Natures imaginary Abhorrence of a Vacuum, but by a Mechanical Necessity, plainly arising from this, that there would be a pressure of the incumbent At­mosphere upon the rest of the sur­face of the stagnant water, and no pressure at all upon that part of the surface that is within the Pipe, where consequently there could be no resi­stance made to the ascension of the water, every where else strongly urg'd by the weight of the incum­bent Air.

I shall add on this occasion, that, to shew some inquisitive Men, that the weak resistance within a Vessel, that had but one orifice expos'd to the water, may much more contribute to the ascension of that Liquor into the Vessel, than either the compression or the continued or reflected impulse of the external Air; I thought fit to produce a Phaenomenon, which by the Beholders was without scruple [Page 23] judg'd an Effect of Suction, and yet could not be ascrib'd to the Cause of Suction, assign'd by either of the Sects of Philosophers I dissent from. The Experiment was this: By a way, elsewhere deliver'd, the long neck of a Glass-bubble was seal'd up, and al­most all the Air had been by Heat driven out of the whole cavity of the Bubble or Vial, and then the Glass was laid aside for some hours, or as long as we pleas'd; afterwards the seal'd apex of the neck was bro­ken off under water: I demand now of a Peripatetic, whether the Liquor ought to be suck'd or drawn into the cavity of the Glass, and why? if he says, as questionless he will, that the water would be attracted to hin­der a Vacuum, he would thereby ac­knowledge, that, 'till the Glass was unstopt under water, there was some empty space in it; for, 'till the sealed end was broken off, the water could not get in, and therefore, if the fuga vacui had any thing to do in the ascen­sion, the Liquor must rise, not to [Page 24] prevent an empty space, but to fill one that was made before. Nor does our Experiment much more favour the other Philosophers, I dissent from: For in it there is no dilatation made of the sides of the Glass, as in ordi­nary Suction there is made of the Thorax, but only there is so much Air driven out of the cavity of the Bubble, into whose room since nei­ther common Air nor Water is per­mitted to succeed, it appears not, how the propagated and returning impulse, or the Circle of Motion, as to com­mon Air and Water, does here take place. And then I demand, what becomes of the Air, that has been by heat driven out, and is by the Her­metical Seal kept out of the cavity of the Bubble? If it be said, that it dif­fuses it self into the ambient Air, and mingles with it, that will be granted which I contended for, that so little Air as is usually displac'd in Suction cannot make any conside­rable compression of the free ambient Air; for, what can one Cubic Inch [Page 25] of Air, which is sometimes more than one of our Glasses contains, do, to the condensation so much as of all the Air in the Chamber, when the expell'd Corpuscles are evenly distri­buted among those of the ambient. And how comes this inconsiderable condensation to have so great an ef­fect in every part of the room, as to be able there to impel into the Glass as much water in extent as the whole Air that was driven out of the cavity of it? But if it be said, that the ex­pell'd Air condens'd only the conti­guous or very neighbouring Air, 'tis easie to answer, that 'tis no way probable, that the expell'd Particles of the Air should not by the differing motions of the ambient Air be quick­ly made to mingle with it, but should rather wait (which if it did we some­times made it do for many hours) 'till the Vessels whence 'twas driven out were unstopp'd again. But, though this could probably be pretended, it cannot truly be asserted. For if you carry the seal'd Glass quite out of the [Page 26] room or house, and unstop it at some other place, though two or three miles distant; the ascension of the water will, (as I found by tryal) ne­vertheless insue; in which case I pre­sume, it will not be said, that the Air, that was expell'd out of the Glass, and condens'd the contiguous or near contiguous Air, attended the Bubble in all its motions, and was ready at hand to impel-in the water, as soon as the seal'd apex of the Vial was broken off. But I doubt not, but most of the Embracers of the Opinion I oppose, being Learned and Inge­nuous Persons, if they had been ac­quainted with these and the like Phaenomena, would rather have chan­ged their Opinion about Suction, than have gone about to defend it by such Evasions, which I should not have thought worth proposing, if I had not met with Objections of this na­ture publickly maintain'd by a Lear­ned Writer, on occasion of the Air's rushing into the exhausted Magden­burgic Engine. But as in our Expe­riment [Page 27] these Objections have no place, so in our Hypothesis the Explication is very easie, as will anon be intimated.

CHAP. III.

HAving thus shewn, that the Ascension of Water upon Su­ction may be caus'd otherwise than by the Condensation or the propaga­ted Pulsion of Air contiguous to the Suckers Thorax, and thrust out of place by it; it remains that I shew, (which was one of the two things I chiefly intended,) that there may be Cases wherein the Cause, assign'd in the Hypothesis I am examining, will not have place. But this will be bet­ter understood, if, before I proceed to the proof of it, I propose to you the thoughts, I had many years since, and do still retain, about the Cause of the Ascension of Liquors in Su­ction.

To clear the way to the right un­derstanding [Page 28] of the ensuing Discourse, it will not be amiss here to premise a summary intimation of some things that are suppos'd in our Hypothesis.

We suppose then first, without disputing either the Existence or the nature of Elementary Air, that the Common Air we breath in, and which I often call Atmospherical Air, abounds with Corpuscles not devoid of Weight, and indowed with E­lasticity or Springiness, whereby the lower parts, comprest by the weight of the upper, incessantly en­deavour to expand themselves, by which expansion, and in proportion to it, the Spring of the Air is wea­ken'd, (as other Springs are wont to be) the more they are permitted to stretch themselves.

Next, we suppose, that the Ter­raqueous Globe, being inviron'd with this gravitating and springy Air, has its surface and the Bodies plac'd on it prest by as much of the Atmosphere as either perpendicularly leans on them, or can otherwise come to bear [Page 29] upon them. And this pressure is by the Torricellian and other Experi­ments found to be equivalent to a perpendicularly erected Cylinder of about twenty nine or thirty Inches of Quicksilver, (for the height is diffe­ring, as the gravity of the Atmosphere happens to be various.)

Lastly, we suppose, that, Air be­ing contain'd in a Pipe or other hol­low Body that has but one orifice open to the free Air, if this orifice be Hermetically seal'd, or otherwise (as with the mouth of one that sucks) clos'd, the now included Air, whilst it continues without any farther ex­pansion, will have an elasticity equi­valent to the weight of as much of the outward Air as did before press against it. For, if the weight of the Atmosphere, to which it was then expos'd, had been able to com­press it further, it would have done so, and then the closing of the ori­fice, at which the internal and ex­ternal Air communicated, as it fenc'd the included Air from the pressure [Page 30] of the incumbent, so it hindred the same included Air from expanding it self; so that, as it was shut up with the pressure of the Atmosphere upon it, that is in a state of as great com­pression as the weight of the Atmo­sphere could bring it to, so, being shut up and thereby kept from wea­kening that pressure by expansion, it must retain a Springiness equi­pollent to the pressure 'twas expos'd to before, which (as I just now no­ted) was as great as the weight [...] the incumbent Pillar of the Atmo­sphere could make it. But if, as was said in the first Supposition, the included Air should come to be dila­ted or expanded, the Spring being then unbent, its Spring, like that of other elastical Bodies, would be de­bilitated answerably to that expan­ [...]ion.

To me then it seems, that, spea­king in general, Liquors are upon Suction raised into the cavities of Pipes and other hollow Bodies, when, and so far as, there is a less pressure [Page 31] on the surface of the Liquor in the cavity, than on the surface of the external Liquor that surrounds the Pipe, whether that pressure on those parts of the external Liquor, that are from time to time impell'd up in­to the orifice of the Pipe, proceed from the weight of the Atmosphere, or the propagated compression or im­pulse of some parts of the Air, or the Spring of the Air, or some other Cause, as the pressure of some other Body quite distinct from Air.

Upon the general view of this Hy­pothesis, it seems very consonant to the Mechanical Principles. For, if there be on the differing parts of the surface of a fluid Body unequal pres­sures, 'tis plain, as well by the na­ture of the thing, as by what has been demonstrated by Archimedes, and his Commentators, that the greater force will prevail against the lesser, and that that part of the waters sur­face must give way, where it is least prest. So that that, wherein the Hy­pothesis I venture to propose to you, [Page 32] differs from that which I dissent from, is not, that mine is less Me­chanical; but partly in this, that, whereas the Hypothesis, I question, supposes a necessity of the protrusion or impulse of the Air, mine does not require that supposition, but, being more general, reaches to other ways of procuring the Ascension of Li­quors, without raising them by the impulse of the Air; and partly, and indeed chiefly, in that the Hypothesis, I decline, makes the Cause of the Ascension of Liquors to be only the increased pressure of the Air exter­nal to the pipe; and I chiefly make it to depend upon the diminished pres­sure of the Air within the pipe, on the score of the expansion 'tis brought to by Suction.

To proceed now to some Experi­ments that I made in favour of this Hypothesis, I shall begin with that which follows:

We took a Glass-pipe bended like a Syphon, but so that the shorter legg was as parallel to the longer as we [Page 33] could get it made, and was Herme­tically seal'd at the end: Into this Sy­phon we made a shift (for 'tis not very easie) to convey water, so that the crooked part being held down­wards, the liquor reach'd to the same height in both the leggs, and yet there was about an Inch and half of uncomprest Air shut up in the shorter legg. This little Instrument (for 'twas but about fifteen Inches long) being thus prepar'd, 'tis plain, that accor­ding to the Hypothesis I dissent from, there is no reason, why the water should ascend upon Suction. For, though we should admit, that the external Air were considerably com­prest, or received a notable impulse, when the Suckers chest is enlarged; yet in our case that compression or protrusion will not reach the surface of the water in the shorter legg, be­cause it is there fenc'd from the action of the external Air by the sides of the Glass, and the Hermetical Seal at the top. And yet, if one suck'd strongly at the open orifice in the [Page 34] longer legg, the water in the shorter would be deprest; and that in the longer ascended at one suck about an Inch and half: Of which the reason is clear in our Hypothesis. For, the Spring of the included Air, together with the weight of the water in the shorter legg, and the pressure of the Atmospherical Air, assisted by the weight of the liquor in the longer legg, counter-ballanced one another before the Suction began: But, when afterwards upon Suction the Air in the longer legg came to be dilated and thereby weaken'd, 'twas ren­der'd unable to resist the undimi­nish'd pressure of the Air included in the shorter legg, which consequent­ly expanding it self by vertue of its Elasticity, deprest the contiguous water, and made it proportionably rise in the opposite legg, 'till by the expansion its Spring being more and more weaken'd, it arrived at an equi­pollency with the gravitation or pres­sure of the Atmosphere. Which last clause contains the Reason, why, when [Page 35] the person that suckt had rais'd the water in the longer legg less than three Inches higher by repeated endeavours to suck, and that without once suffe­ring the water to fall back again, he was not able to elevate the water in the longer, so much as three Inches above its first station. And if in the shorter legg there was but an Inch and a quarter of space left for the Air unfill'd by the water, by divers skilfully reiterated acts of Suction he could not raise the liquor in the longer legg above two Inches; be­cause by that time the Air included in the shorter legg had, by expanding it self further and further, proportio­nably weaken'd its Spring, 'till at length it became as rarified, as was the Air in the cavity of the longer legg, and consequently was able to thrust away the water with no more force than the Air in the long legg was able to resist. And by the reci­ted tryal it appear'd, that the rare­faction usually made of Air by Suction is not near so great, as one would [Page 36] expect, problably because by the di­latation of the Lungs the Air, being still shut up, is but moderately rarified, and the Air in the longer legg can by them be brought to no greater de­gree of rarity, than that of the Air within the Chest. For, whereas the included Air in our Instrument was not expanded, by my estimate, at one suck to above the double of its former dimensions, and by divers suc­cessive sucks was expanded but from one Inch and an half to less than four Inches and an half, if the Suction could have been conveniently made with a great and stanch Syringe, the rarefaction of the Air would proba­bly have been far greater; since in our Pneumatick Engin Air may, without heat, and by a kind of Su­ction, be brought to possess many hundreds of times the space it took up before. From this rarefaction of the Air in both the leggs of our In­strument proceeds another Phaenome­non, readily explicable by our Hypo­thesis. For if, when the water was [Page 37] impell'd up as high as the Suction could raise it; the Instrument were taken from th [...] Suckers mouth, the elevated water would with violence return to its wonted station. For, the Air, in both the leggs of the In­strument, having by the Suction loft much of the Spring, and so of its power of pressing; when once the orifice of the longer legg was left open, the Atmospherical Air came again to gravitate upon the water in that legg, and the Air, included in the other legg, having its Spring de­bilitated by the precedent expansion, was not able to hinder the external Air from violently repelling the ele­vated water, 'till the included Air was thrust into the space it possess'd before the Suction; in which space it had Density and Elasticity enough to resist the pressure, that the external Air exercis'd against it through the interpos'd water.

But our Hypothesis about the Cause of Suction would not need to be soli­citously prov'd to you by other ways, [Page 38] if you had seen what I have some­times been able to do in our Pneu­matick Engin. For, there we found by tryals purposely devis'd, and care­fully made, that a good Syringe be­ing so conveyed into our Receiver, that the open orifice of the Pipe or lower part was kept under water, if the Engin were exhausted, though the handle of the Syringe were drawn up, the water would not follow it, which yet it would do if the exter­nal Air were let in again. The Rea­son of which is plain in our Hypothesis. For, the Air, that should have prest upon the surface of the stagnant wa­ter, having been pumpt out, there was nothing to impell up the water into the deserted cavity of the Sy­ringe, as there was when the Recei­ver was fill'd with Air.

CHAP. IV.

BUt because such a conveniency as our Engin, and the apparatus ne­cessary for such Tryals are not easily procurable, I shall endeavour to con­firm our Hypothesis about Suction by subjoining some Experiments, that may be tryed without the help of that Engin, for the making out these three things:

  • I. That a Liquor may be rais'd by Suction, when the pressure of the Air, neither as it has Weight nor Elasticity, is the Cause of the Elevation.
  • II. That the weight of the Atmo­spherical Air is sufficient to raise up Li­quors in Suction.
  • III. That in some cases Suction will not be made, as, according to the Hypo­thesis I dissent from, it should, although there be a dilatation of the Suckers Tho­rax, and no danger of a Vacuum though the Liquor should ascend.

[Page 40]And first, to shew, how much the rising of Liquors in Suction de­pends upon the weight or pressure of the impellent Body, and how little necessity there is, where that pres­sure is not wanting, that, in the place deserted by the Liquor that is suck'd, there should succeed Air or some other visible Body, as the Peri­patetic Schools would have it; to [...]hew this, I say, I thought on the following Experiments. We took a Glass-pipe fit to have the Torricellian Experiment made with it, but a good deal longer than was necessary for that use: This Pipe being Hermeti­cally seal'd at one end, the other end was so bent as to be reflected upwards, and make as it were the shorter legg of the Syphon as parallel as we could to the longer, so that the Tube now was shap'd like an inverted Syphon with leggs of a very unequal length. This Tube, notwithstanding its in­convenient figure, we made a shift, (for 'tis not easily done) to fill with Mercury, when 'twas in an inclin'd [Page 41] posture, and then erecting it, the Mercury subsided in the longer legg, as in the Torricellian Experiment, and attain'd to between two foot and a quarter and two foot and an half a­bove the surface of the Mercury in the shorter legg, which in this In­strument answers to the stagnant Mercury in an ordinary Barometer, from which to distinguish it I have elswhere call'd this Syphon, furnish'd with Mercury, a Travelling Baroscope, because it may be safely carried from place to place. Out of the shorter legg of this Tube we warily took as much Mercury as was thought con­venient for what we had further to do, and this we did by such a way as to hinder any Air from getting in­to the deserted cavity of the longer legg, by which means the Mercurial Cylinder, (estimated as I lately men­tion'd) retain'd the same height above the stagnant Mercury in the shorter: The upper and clos'd part of this Travelling Baroscope you will easily grant to have been free from Common [Page 42] Air, not only for other Reasons that have been given elsewhere, but par­ticularly for this, that, if you gently incline the Instrument, the Quick­silver will ascend to the top of the Tube; which you know it could not do, if the place, formerly deserted by it, were possest by the Air, which by its Spring would hinder the ascen­sion of the Mercury, (as is easie to be tryed.) The Instrument having been thus fitted, I caus'd one of the by­standers to suck at the shorter legg, whereupon (as I expected) there pre­sently ensued an Ascension of four or five Inches of Mercury in that legg, and a proportionable Subsidence of the Mercury in the longer, and yet in this case the raising of the Mer­cury cannot be pretended to proceed from the pressure of the Air. For, the weight of the Atmosphere is fenc'd off by that, which closes the upper end of the longer Tube, and the Spring of the Air has here nothing to do, since, as we have lately shewn, the space deserted by the Mercury is [Page 43] not possest by the included Air, and the pulsion or condensation of the Air, suppos'd by divers modern Philoso­phers to be made by the dilatation of the Suckers Chest, and to press upon the surface of the Liquors that are to be suck'd up, this, I say, cannot here be pretended in regard the sur­face of the Liquor in the longer legg is every way fenc'd from the pressure of the ambient Air. So that it re­mains, that the Cause, which rais'd the Quicksilver in the shorter legg upon the newly recited Suction, was the weight of the collaterally supe­riour Quicksilver in the longer legg, which, being (at the beginning of the Suction) equivalent to the weight of the Atmosphere, there is a plain reason, why the stagnant Mercury in the shorter legg should be rais'd some Inches by Suction; as Mercury stag­nant in an open Vessel will be rais'd by the weight of the Atmosphere, when the Suction is made in the open Air. For, in both cases there is a Pipe, that reaches to the stagnant [Page 44] Mercury, and a competent weight to impel it into that Pipe; when the Air in the cavity of the Pipe has its Spring weaken'd by the dilatation that accompanied Suction.

The Second point formerly pro­pos'd, which is, That the weight of the Air is sufficient to raise Liquors in Suction; may not be ill prov'd by Arguments legitimately drawn from the Torricellian Experiment it self, and much more clearly by the first and fifteenth of our Continued Physico-Me­chanical Experiments. And therefore I shall only here take notice of a Phae­nomenon, that may be exhibited by the Travelling Baroscope, which, though it be much inferiour to the Experi­ments newly referr'd to, may be of some use on the present occasion.

Having then provided an Instru­ment like the Travelling Baroscope, mention'd under the former Head, but whose leggs were not so unequally long, and having in it made the Tor­ricellian Experiment after the manner lately describ'd; we order'd the mat­ter [Page 45] so, that there remain'd in the shorter legg the length of divers In­ches unfill'd with stagnant Mercury. Then I caus'd one, vers'd in what he was to do, so to raise the Quick­silver by Suction to the open orifice of the shorter legg, that, the orifice being seasonably and dexterously clo­sed, the Mercury continued to fill that legg, as long as we thought fit; and then having put a mark to the surface of the Mercury in the longer legg, we unstopp'd the orifice of the shorter; whereupon the Mercury, that before fill'd it, was depress'd, 'till the same Liquor in the longer legg was rais'd five Inches or more above the mark, and continu'd at that height. I said, that the Mercury that had been raised by Suction, was depress'd, rather than that it subsided, because its own weight could not here make it fall, since a Mercurial Cylinder of five Inches was far from being able to raise so tall a Cylinder of Mercury as made a counterpoise in the longer legg; and therefore the depression we spea [...] [Page 46] of, is to be referr'd to the gravitation of the Atmospherical Air upon the surface of the Mercury in the shorter legg: And I see no cause to doubt but that, if we could have procured an Instrument, into whose shorter legg a Mercurial Cylinder of many In­ches higher could have been suck'd up, it would by this contrivance have appear'd, that the pressure of the Atmosphere would easily impel up a far taller Cylinder of Mercury than it did in our recited Expe [...] ­ment.

That this is no groundless conje­cture may appear probable by the Ex­periment you will presently meet with. For if the gravity of an in­cumbent Pillar of the Atmosphere be able to compress a parcel of inclu­ded Air as much as a Mercurial Cy­linder, equivalent in weight to be­tween thirty and five and thirty foot of water, is able to condense it, it cannot well be denied that the same Atmospherical Cylinder may be able by its weight to raise and counter-ballance [Page 47] eight or nine and twenty Inches of Quicksilver, or an equiva­lent pillar of water in Tubes, where the resistance of these two Liquors to be rais'd and sustain'd by the Air, depends only upon their own unassi­sted gravity.

To confirm our Doctrine of the Gravitation of the Atmosphere upon the surface of the Liquors expos'd to it, I will subjoin an Experiment, that I devis'd to shew, that the incum­bent Air, in its natural or usual state, would compress other Air not rarified, but in the like natural state, as much as a Cylinder of eight or nine and twenty Inches of Mercury would condense or compress it.

In order to the making of this, I must put you in mind of what I have shewn elsewhere at large, See the Authors Defence of the Doctrine touching the Spring and Weight of the Air, against Fr. Li­nus, chap. 5. and shall fur­ther confirm by one of the Experiments that follows the next; namely, that about twenty nine or thirty Inches of Quicksilver [Page 48] will compress Air, that being in its natural or usual state (as to rarity and density) has been shut up in the shor­ter legg of our Travelling or Syphon-like Baroscope, into half the room that included Air possess'd before. This premis'd, I pass on to my Ex­periment, which was this:

We provided a Travelling Baroscope, wherein the Mercury in the longer legg was kept suspended by the coun­terpoise of the Air that gravitated on the surface of the Mercury in the shorter legg, which we had so or­der'd, that it reached not by about two Inches to the top of the shorter legg. Then making a mark at the place where the stagnant Mercury rested, 'twas manifest according to our Hypothesis, that the Air. in the upper part of the shorter legg was in its natural state, or of the same de­gree of density with the outward Air, with which it freely commu­nicated at the open orifice of the shor­ter legg; so that this stagnant Air was equally prest upon by the weight [Page 49] of the collaterally superiour Cylinder of Mercury in the longer legg, and the equivalent weight of a directly in­cumbent pillar of the Atmosphere. Things being in this posture, the upper part of the shorter legg, which had been before purposely drawn out to an almost capillary smallness, was Hermetically seal'd, which, though the Instrument was kept erected, was so nimbly done by reason of the slen­derness of the Pipe, that the inclu­ded Air did not appear to be sensibly heated, though for greater caution we staid a while from proceeding, that, if any rarefaction had been produc'd in the Air, it might have time to lose it again. This done, we open'd the lower end of the lon­ger legg, (which had been so order'd before, that we could easily do it, and without concussion of the Vessel,) by which means the Atmospherical Air, gaining access to the Mercury included in the longer legg, did, as I expected, by its gravitation upon it so compress the Air included in [Page 50] the shorter legg, that, according to the estimate we made with the help of a Ruler, (for by reason of the conical figure of the upper part of the glass we could not take precise measures,) it was thrust into near half the room it took up before, and consequently, according to what I put you lately in mind of, endur'd a compression like that, which a Mer­curial Cylinder of about twenty nine Inches would have given it.

This Experiment, as to the main of it, was for greater caution made the second time with much the like success; and though it had been more easie to measure the Condensation of the Air, if, instead of drawing out and sealing up the shorter legg of the Instrument, we had contented our selves to close it some other way; yet we rather chose to imploy Hermes's Seal, lest, if any other course had been taken, it might be pretended, that some of the included Air, when it began to be comprest, might escape out at the not perfectly and strongly [Page 51] clos'd orifice of the legg wherein 'twas imprison'd.

To make it yet further appear, how much the Ascension of Liquors by Suction depends upon Pressure, rather than upon Natures imaginary Abhor­rence of a Vacuum, or the propagated Pulsion of the Air; I will subjoin an Instance, wherein that presum'd Abhorrence cannot be pretended. The Experiment was thus made:

A Glass-Syphon, like those lately describ'd, with one legg far longer than the other, was Hermetically seal'd at the shorter legg, and then by degrees there was put in, at the orifice of the longer legg, as much Quick­silver as by its weight suffic'd to com­press the Air in the shorter legg into about half the room it possess'd be­fore; so that, according to the Peri­patetick Doctrine, the Air must be in a state of preternatural Condensa­tion, and that to a far greater degree, than (as I have tryed) 'tis usually brought to by Cold, intense enough to freeze water. Then measuring [Page 52] the heighth of the Quicksilver in the longer Tube above the superficies of that in the shorter, we found it not exceed thirty Inches. Now, if Li­quors did rise in Suction ob fugam vacui, there is no reason, why this Quicksilver in the longer part of the Syphon should not easily ascend upon Suction, at least 'till the Air in the shorter legg had regain'd its former Dimensions, since it cannot in this place be pretended, that, if the Mer­cury should ascend, there would be any danger of a Vacuum in the shorter legg of the Tube, in regard that the contiguous included Air is ready at hand to succeed as fast as the Mercury subsides in the shorter legg of the Sy­phon. Nor can it be pretended, that, to fill the place deserted by the Quick­silver, the included Air must suffer a preternatural rarefaction or discen­sion; since 'tis plain in our case, that on the contrary, as long as the Air continues in the state whereto the weight of the Quicksilver has re­duc'd it, it is kept in a violent state [Page 53] of compression; since in the shorter legg it was in its natural state, when the Mercury, poured into the longer legg, did by its weight thrust it in­to about half the room it took up before. And yet, having caus'd se­veral persons, one of them vers'd in sucking, to suck diver's times as strongly as they could, they were neither of them able, not so much as for a minute of an hour, to raise the Mercury in the longer legg, and make it subside in the shorter for more than about an Inch at most. And yet to shew you, that the Experi­ment was not favourably tryed for me, the height of the Mercurial Cy­linder in the longer legg above the surface of that in the shorter legg was, when the Suction was tryed, an Inch or two shorter than thirty Inches, and the comprest Air in the shorter legg was so far from having been by the exsuction expanded be­yond its natural and first dimensions, that it did not, when the contiguous Mercury stood as low as we could [Page 54] make it subside, regain so much as one half of the space it had lost by the precedent Compression, and con­sequently was in a preternatural state of condensation, when it had been freed from that state as far as Suction would do it. Whence it seems evi­dent, that 'twas not ob fugam vacui, that the Quicksilver did upon Suction ascend one Inch; for, upon the same score it ought to have ascended two, or perhaps more Inches, since there was no danger, that by such an ascen­sion any Vacuum should be produc'd or left in the shorter legg of the Sy­phon; whereas, according to our Hypothesis, a clear cause of the Phae­nomenon is assignable. For, before the Suction was begun, there was an AEquilibrium or equipollency be­tween the weight of the superiour Quicksilver in the longer legg, and a Spring of the comprest Air inclu­ded in the shorter legg: But when the Experimentor began to suck, his Chest being widen'd, part of the Air included in the upper part of the [Page 55] longer legg pass'd into it, and that which remain'd had by that expan­sion its pressure so weaken'd, that the Air in the shorter legg, finding no longer the former resistance, was able by its own Spring to expand it self, and consequently to depress the contiguous Mercury in the same shor­ter legg, and raise it as much in the longer.

But here a Hydrostatician, that heed­fully marks this Experiment, may discern a difficulty, that may perhaps somewhat perplex him, and seems to overthrow our Explication of the Phaenomenon. For he may object, that if the comprest Air in the shorter legg had a Spring equipollent to the weight of the Mercury in the longer legg, it appears not, why the Mer­cury should not be suckt up in this Instrument, as well as in the free Air; since, according to me, the pressure of the included Air upon the subjacent Mercury must be equivalent to the weight of the Atmosphere, and yet experience shews, that the [Page 56] weight of the Atmosphere will, upon Suction, raise Quicksilver to the height of several Inches.

To clear this difficulty, and shew, that, though it be considerable, 'tis not at all insuperable, be pleased to consider with me, that I make indeed the Spring of the comprest Air to be equipollent to the Weight of the com­pressing Mercury, and I have a ma­nifest reason to do it; because, if the Spring of the Air were not equipol­lent to that Weight, the Mercury must necessarily compress the Air farther, which 'tis granted de facto not to do. But then I consider, that in our case there ought to be a great deal of difference between the ope­ration of the Spring of the included Air and the Weight of the Atmosphere, after Suction has been once begun. For, the Weight of the Atmosphere, that impels up Mercury and other Li­quors, when the Suction is made in the open Air, continues still the same, but the force or pressure of the inclu­ded Air is equal to the counterpressure [Page 57] of the Mercury no longer than the first moment of the Suction; after which, the force of the imprison'd Air still decreases more and more, since this comprest Air, being fur­ther and further expanded, must needs have its Spring proportionably wea­ken'd; so that it need be no wonder, that the Mercury was not suckt up any more than we have related; for there was nothing to make it ascend to a greater height, than that, at which the debilitated Spring of the (included but) expanded Air was brought to an equipollency with the undiminish'd and indeed somewhat increas'd weight of the Mercurial Cylinder in the longer legg, and the pressure of the Aerial Cylinder in the same legg, lessen'd by the action of him that suck'd. For whereas, when the orifice of this legg stood open, the Mercury was prest on by a Cylin­der of the Atmospherical Air, equiva­lent to about thirty Inches of Quick­silver; by the mouth and action of him that suck'd the Tube was [Page 58] freed from the external Air, and by the dilatation of his Thorax, the neigh­bouring Air, that had a free passage through his wind-pipe to it, was proportionably expanded, and had its Spring and pressure weaken'd: By which means, the comprest Air in the shorter legg of the Syphon was inabled to impel up the Mercury, 'till the lately mention'd Equilibrium or equipollency was attain'd. And I must here take notice, that, as the Quicksilver was rais'd by Suction but a little way, so the Cylinder that was rais'd was a very long one; whereas, when Mercury is suck'd up in the free Air, it is seldom rais'd to half that length; though, as I noted before, the impellent cause, which is the weight of the Atmosphere, continued still the same, whereas in our Syphon, when the Mercury was suck'd up but an Inch, the comprest Air, possessing double the space it did before, had by this expansion al­ready lost a very considerable part of its former Spring and Pressure.

[Page 59]I should here conclude this Dis­course, but that I remember a Phae­nomenon of our Pneumatic Engin, which to divers Learned Men, espe­cially Aristotelians, seem'd so much to argue, that Suction is made either by a Fuga Vacui, or some internal Principle, that divers years ago I thought fit to set down another ac­count of it, and lately meeting with that account among other papers, I shall subjoin it just as I found it, by way of Appendix to the foregoing Tract.

Among the more familiar Phaeno­mena of the Machina Boyliana, (as they now call it,) none leaves so much scruple in the Minds of some sorts of Men, as this, That, when ones fin­ger is laid close upon the orifice of the little Pipe, by which the Air is wont to pass from the Receiver into the exhausted Cylinder, the pulp of the finger is made to enter a good way into the cavity of the Pipe, which doth not happen without a considerable sense of pain in the lower [Page 60] part of the fing [...]r. For most of tho [...] that are strangers to Hydrostatic [...] especially if they be prepossess'd wi [...] the Opinions generally receiv'd bot [...] in the Peripatetick and other School [...] perswade themselves, that they f [...] the newly mention'd and painful pro­tuberance of the pulp of the finger to be effected not by pressure, as [...] would have it, but distinctly by A [...]traction.

To this we are wont to answer That common Air being a Body [...] devoid of weight, the Phenomeno [...] is clearly explicable by the pressu [...] of it: For, when the finger is fir [...] laid upon the orifice of the Pipe, no pain nor swelling is produc'd, because the Air which is in the Pipe presse [...] as well against that part of the fin­ger which covereth the orifice, as the ambient Air doth against the other parts of the same finger. But when by pumping, the Air in the Pipe, or the most part of it, is made to pass out of the Pipe into the exhausted Cylinder, then there is nothing left [Page 61] in the Pipe, whose pressure can any thing near countervail the undimi­nish'd pressure of the external Air on the other parts of the finger; and consequently, that Air thrusts the most yielding and fleshy part of the finger, which is the pulp, into that place where its pressure is unresisted, that is, into the cavity of the Pipe, where this forcible intrusion causeth a pain in those tender parts of the finger.

To give some visible Illustration of what we have been saying, as well as for other purposes, I thought on the following Experiment.

We took a Glass-pipe of a conve­nient length, and open at both ends, whose cavity was near about an Inch in Diameter, (such a determinate breadth being convenient, though not necessary:) To one of the ends of this Pipe we caused to be firmly tyed on a piece of very fine Bladder, that had been ruffled and oyl'd, to make it both very limber and unapt to ad­mit water; and care was taken, that [Page 62] the piece of Bladder tyed on [...]hould be large enough, not only to cover the orifice, but to hang loose some­what beneath it.

This done, we put the cover'd end of the Pipe into a Glass-body (or Cu­curbit) purposely made more than or­dinarily tall, and the Pipe being held in such manner, as that the end of it reach'd almost, but not quite, to the bottom of the Glass-body, we caused water to be poured both into this Vessel and into the Pipe (at its upper orifice, which was left open) that the water might ascend equally enough, both without and within the Pipe. And when the Glass-body was full of water, and the same li­quor was level to it, or a little higher within the Pipe, the Bladder at the lower orifice was kept plump, be­cause the water within the Pipe did by its weight press as forcibly down­wards, as the external water in the large Glass endeavour'd to press it in­wards and upwards.

All this being done, we caus'd [Page 63] part of the water in the Pipe to be [...]aken out of it, (which may be done either by putting in and drawing out a piece of Spunge or of Linnen, or more expeditiously by sucking up part of the water with a smaller Pipe to be immediately after laid aside;) up­on which removal of part of the in­ternal water, that which remained in the Pipe being no longer able, by reason of its want of weight, to press against the inside of the Bladder near as forcibly as it did before, the ex­ternal water, whose weight was not lessen'd, press'd the sides and bottom of the Bladder, whereto it was contiguous, into the cavity of the Pipe, and thrusted it up there­in so strongly, that the distended Bladder made a kind of either Thim­ble or Hemisphere within the Pipe. So that here we have a protube­rance, like that above-mentioned of the finger [...] effected by Pulsion, not Attraction [...] and in a case where there can be no just pretence of having [...]course to Natures Abhorrance of a [Page 64] Vacuum, since, the upper orifice of the Pipe being left wide open, the Air may pass in and out without resi­stance.

The like swelling of the Bladder in the Pipe we could procure without taking out any of the internal li­quor, by thrusting the Pipe deeper into the water; for then the external liquor, having by reason of its in­crease of depth a greater pressure on the outside of the Bladder, than the internal liquor had on the inside of it, the Bladder must yield to the stronger pressure, and consequently be impell'd up.

If the Bladder lying loofe at the lower end of the Pipe, the upper end were carefully clos'd with ones thumb, that the upper Air might not get out until the Experimentor thought fit, and if the thus clos'd Pipe were thrust almost to the bot­tom of the water, the Bladder would not be protuberant inwards, as for­merly; because the included Air by virtue of its Spring, resisted from [Page 65] within the pressure of the external water against the outside of the Blad­der: But if the thumb, that stopp'd the Pipes upper orifice, were re­mov'd, the formerly compress'd Air having liberty to expand it self, and its elasticity being weaken'd there­by, the external water would with suddenness and noise enough, not to be unpleasant to the Spectators, drive up the Bladder into the cavity of the Pipe, and keep it there very protu­berant.

To obviate an Objection, that I foresaw might be brought in by per­sons not well vers'd in Hydrostaticks, I caus'd the Pipe fore-mention'd, or such another, to be so bent near the lower end, as that the orifice of it stood quite on one side, and the parts of the Pipe made an angle as near to a right one as he that blew it could bring it to. This lower o­rifice being fitted with a Bladder, and the Pipe with its contained liquor being thrust under water after the former manner, the lateral pressure [Page 66] of the water forc'd the Bladder into the short and horizontal legg, and made it protuberate there, as it had done when the Pipe was straight.

Lastly, that the Experiment might appear not to be confin'd to one li­quor; instead of Water we put into the unbent Pipe as much red Wine (who [...]e colour would make it con­spicuous) as was requisit to keep the Bladder somewhat swelling outwards, when it was somewhat near the bot­tom of the water; and then 'twas manifest, that, according as we had foreseen, the superficies of the red liquor in the Pipe was a good deal higher than that of the external wa­ter, and if the depth of both liquors were proportionably lessen'd, the dif­ference of height betwixt the two surfaces would indeed, as it ought to happen, decrease, but still the sur­face of the wine would be the higher of the two, because being lighter in specie than the common water, the AEquilibrium between the pressures of the two liquors upon the Bladder [Page 67] would not be maintain'd, unless a greater height of wine compensated its defect of specifick gravity. And if the Pipe was thrust deeper into the water, then the Bladder would be made protuberant inwards, as when the Pipe had water in it. By which it appears, that these Phaeno­mena, without recourse to attraction, may be explicated barely by the Laws of the AEquilibrium of Liquors.

FINIS.
NEW EXPERIMENTS Abou …

NEW EXPERIMENTS About the PRESERVATION OF BODIES IN VACUO BOYLIANO.

By the Honourable ROBERT BOYLE, Fellow of the Royal Society.

LONDON, Printed by William Godbid, and are to be Sold by Moses Pitt, at the Angel over against the little North Door of St. Paul's Church. 1674.

PREFACE.

MY willingness to make the bulk of the Papers a­bout the Hidden Qua­lities of the Air less inconside­rable, by things that were of affi­nity to the Subject, inducing me to tumble over some of my Ad­versaria, I met among them with divers loose Notes, or short Memo­rials of some Experiments I made several years ago (and some of a fresher date) about the Preserva­tion of Bodies by excluding the Air, wherefore I was easily per­swaded to subjoin these to the Ad­ditional [Page] Experiments last recited. For it seems not yet clear, by what manifest Quality the Exclusion of the Air should so much contribute to keep from putrefaction variety of Bodies, that are usually found very much disposed to it. And therefore 'till the Cause of this Preservation be further p [...]ated, it may not be altogether impertinent to mention some Experiments rela­ting to it. And though these be only such as come now to hand, and were most of them set down rather as Notes than Relations, yet being faithfully register'd, and most of them having been made in Vacuo Boyliano (as they call it) they will problably be New, and so per­haps not altogether useless to Na­turalists, who may vary them, and requite me for them, by trying the [Page] same Experiments, I made by the Removal of the Air by the bare Exclusion of adventitious Air. For sometimes through hast I did not, and sometimes for want of conve­niency I could not, try, whether the same Phaenomena would appear, if the same Bodies were shut up with Air in them, provided they were diligently kept from all com­merce with the Air without them.

NEW EXPERIMENTS ABOUT THE Preservation of BODIES IN VACVO BOYLIANO.

EXPER. I.

A Piece of roasted Rabbet, being exactly clos'd up in an exhausted Receiver the Sixth of November, was two months and some few days after ta­ken out without appearing to be corrupted, or sensibly alter'd in Co­lour, Tast, or Smell.

EXPER. II.

A small Glass-Receiver, being half fill'd with pieces of White-bread, (part Crust and part Crumb) was ex­hausted, and secur'd the eleventh of March: The Receiver being open'd the first of April, part of the Bread was shaken out, and appear'd not to have been considerably, if at all sen­sibly impair'd in that time, save that the outside of some pieces of Crumb seem'd to be a little, and but a little, less soft and white than before. There appear'd no drops or the least Dew on the inside of the Glass. The remai­ning Bread was again secur'd soon after,

The eighteenth of April, the Bread was taken out again, and tasted much as it did the last time, the Crust being also soft, and no drops of water appearing on the inside of the Glass.

EXPER. III.

This day (being the ninth of March) I open'd a small exhausted and secur'd Receiver, wherein, [...]bout the ninth of December, that is, about three months ago, we had included some Milk: Upon opening an access to the Air, we found the Milk well colour'd, and turn'd partly into a kind of Whey, and partly into a kind of soft Curd. The tast was not offensive, only a little sowrish like Whey, and the smell was not at all stinking, but somewhat like that of sowrish Milk.

EXPER. IV.

The Violet-leaves, that were put up, and freed and secur'd from Air the fifth of March, being this day open'd, ( April the seventh) appear'd not to have chang'd their shape, or colour, or consistence: For, as for their o­dour, it could not be well judg'd of, because he that included them had, for [Page 4] his own ease, contrary to my express direction, [...]rush'd many of them to­gether in thrusting them down; and by such a violation of their Texture, it's natural for Violets to lose their fragrancy, and acquire an Earthy smell.

EXPER. V.

Having carefully placed some Vio­lets in an exhausted Receiver, of a convenient size and bigness, and se­cur'd it from immediate commerce with the external Air; the Seventh month after we look'd upon them again, and found they were not pu­trified or resolved into any mucila­ginous substance, but kept their shape intire, some of them retaining their colour, but more of them having so lost it, as to look like white Violets.

EXPER. VI.

November the fifth, we conveyed into a conveniently shap'd Recei­ver [Page 5] some ounces of Sheeps-blood, taken from an Animal that had been kill'd that afternoon. And after the exhaustion of the Air, du­ring which, store of bubbles were generated in the Liquor that made it swell notably, the included Blood was kept in a place, (whose warmth we judg'd equal to that of a digestive Furnace) for twenty days; for one or two of the first of which, the Blood seem'd to continue fluid, and of a florid colour, which after­wards degenerated into one that ten­ded more to blackness. On the twen­ty fifth of November we came to let-in the external, and found it to rush into the Receiver, and the Glass con­taining the Blood being held in a lightsom place, the most part of the bottom of it seem'd to be thinly o­verlaid with a coagulated substance of a higher colour than that which swam above it, which yet, though it appeared dark and almost blackish in the Glass whilst it was look'd on in the bulk, yet, if it was shook, those [Page 6] parts of it that fell down along the inside of the Glass, appear'd of a deep but fair colour. But whilst the Blood continued in the Glass, it was sup­pos'd not to stink, since, even when it was poured out, though its smell seem'd to me (whose Organs of Smel­ling are tender) to have I know not what that was offensive, yet to o­thers it seem'd to smell but as the Blood of a newly kill'd Dog.

EXPER. VII.

Some Cream being put up and se­cur'd the seventeenth of March in an exhausted Receiver, did this day ap­pear to be more thick and almost Butter-like at the top (whose super­ficies seem'd rugged) than otherwhere, and afterwards by being well shaken together in the not inconveniently shap'd Glass, was easily enou [...] re­duc'd to Butter, whose Butter-milk, by the judgment of those who were more us'd to deal in it than I, ap­pear'd not differing from ordinary [Page 7] Butter-milk. And I found it had, like that, a grateful sowrness. The Butter was judg'd to be a little sow­rer than ordinary, but was not, as they speak, made.

[In the Entry of this Experiment, Blanks were left for the years; but the Tenour of the words, and De­sign of the Experiment, and other Circumstances, assure me, that the Cream continued a year in the vessel.]

EXPER. VIII.

February the eighteenth we look'd again upon three Vials, that had been exhausted and secur'd the fifteenth of September last, the one of these had in it some slices of roasted Beef, and the other some shivers of white Bread, and the last some thin pieces of Cheese; all which seem'd to be free from pu­trefaction, and look'd much as they did when they were first put up: Wherefore we thought not fi [...] to let the Air into the Receiver, but left them as they were to lengthen the de­sign'd Trial.

EXPER. IX.

February the eighteenth, there was a fourth Vial, wherein about six months before, viz. August the twelfth, had been inclos'd and secur'd some Iuly-flowers and a Rose; and yet these being kept in the same place with the rest, though they seemed a little moist, retained their shape and co­lour, especially the Rose, which look'd fresh enough to seem to have been ga­ther'd but lately.

N. B. That we observed not in any of these four Receivers any great drops, or so much as Dew in the upper parts, viz. those that were situated above the included matter.

EXPER. X.

Iune the fourth we left some Straw­berries in an exhausted Receiver, and coming to look upon them after the beginning of November, we found them to be discolour'd, but not alter'd [Page 9] in shape, nor affording any sign of Corruption by being at all mouldy [...] Wherefore we thought fit to leave them still in the Receiver for further Trial.

EXPER. XI.

May the second, 1669, a piece of roasted Beef, secur'd September the fif­teenth, appear'd to be not at all al­ter'd: As did likewise a piece of Cheese secur'd in another Receiver; and some pieces of a French Rose the same day ( September the fifteenth) se­cur'd in a third.

N. B. The Flowers seal'd up Au­gust the twelfth, 1668, being this day look'd upon, appear'd fresh, and con­sequently did so after having been kept eight months and an half.

EXPER. XII.

There was taken Beer of eight shil­lings a Barrel, of a year old, near a Pint of which, Iune the seventeenth, [Page 10] was put into a conveniently shap'd Glass, and it was afterwards exhau­sted and secur'd from the Air; the most part of the month of August prov'd extraordinarily hot. Towards the latter end there was at several times great Thunder, which made the Beer in our Cellar, and in most of those of the Neighbourhood, turn soure. The first of September, the Beer was open'd, but did not seem to have degenerated into any soureness.

EXPER. XIII.

Being desirous to try, whether the Thunder would have such effect upon Ale exactly stopp'd in Glass-vessels, as it often has on that Liquor in the ordinary wooden Casks; I caus'd some Ale moderately strong to be put into a conveniently shap'd Receiver, and having exhausted the Air and secur'd a Glass-vessel, 'twas put into a quiet, but not cool, place: Last week, which was about six weeks after the Liquor had been inclos'd, [Page 11] there happening some very loud Thunder, and our Beer, though the Cask was kept in a good Cellar, be­ing generally noted to have been turn'd soure after this Thunder; I staid yet a day or two longer, that the operation upon our included Li­quor might be the more certain and manifest; and then permitting an ac­cess to the outward Air, we took out the Ale, and found it to be good drink, and not at all soured.

Compare this with the Wish made in the Essay of the Great Efficacy of Effluviums, chap. 5. pag. 28. that such an Experiment should be tried.

EXPER. XIV.

September the twenty first, 1670, some Blackberries, included in an ex­hausted Receiver, were open'd Iune the twentieth, 1673, and were found free from all mouldiness and ill sent, only there was found some Liquor that was soure, which being taken out the Berries were secur'd again.

[Page 12][ At the same time was another [...] of the same Berries exactly clos'd up i [...] a Receiver, whence the Air was [...] pump'd, to try what difference in the Event would appear by this variation. But, coming in October the eleventh, 1673, to look upon the Glass, we found it crack'd, and the Fruit all cover'd over with a thick mould. Nor was this the only Vessel wherein Trials, made to re­serve Fruits, without any exhaustion of the Air, miscarried.]

October the eleventh, 1674, the sam [...] Berries, being look'd upon, appear'd to have their colour alter'd, and much less black than before, but did not appear putrefied by either loss of shape, or by any stinking smell, nor was the least mouldiness observed to be on them, though they had been kept in the same Receiver above four year.

That Fructus Horarii, especially so tender and juicy ones, should with­out any additament be preserved from putrefaction so many times lon­ger than otherwise they would have [Page 13] lasted, as 'tis more than would be expected, so it may give hopes, that both odd add useful things of this kind may be this way per­formed.

POSTSCRIPT.

THe foregoing Experiments, as the Memorials themselves de­clare, were all of them made in Vacu [...] Boyliano, nor did I intend to set down any other: But meeting among those Memorials with a short account of a couple of Trials made without the help of our Pneumatic Engine, I was induc'd to annex them, because many may make the like, that will not be able to make such as have been hi­therto recited. And these two re­quiring no peculiarly shap'd Vessels, 'tis thought, it may prove of some Oeconomical as well as Physical use, if it be shewn by experience, that Liquors Hermetically-seal'd the or­dinary way in common Bolt-heads may be kept from souring very much beyond their usual time of lasting.

[Page 15] Iune the fourteenth we put a con­venient quantity of good Ale into a Bolt-head, and seal'd it up Hermeti­cally; the next year, on the fifth of Iuly, we broke off the Seal, and found the Liquor very good and without any sensible sowreness. The next day it was seal'd up again and set by for thirteen months, at which time the neck of the Glass being bro­ken, the Ale was found pretty sowre, and therefore the Trial was prose­cuted no farther: So that, though this Liquor would not by this way of Preservation be kept from sowring so long as the Wine, to be men­tion'd in the following Experiment, yet even a small quantity of it was preserved good at the least above a year, which is very much longer than Ale is wont to keep from sowring.

Iune the fourteenth, 1670, in a large Bolt-head was Hermetically seal'd up about a Pint, by guess, o [...] French Claret-wine, which, when we [Page 16] came to look upon, Iuly the fifth, 1671, appear'd very clear and high colour'd, and had deposited store of feces at the bottom of the Glass, but fasten'd no Tartar that we could per­ceive to the sides. Upon the breaking of the seal'd end of the Glass, the By [...]standers thought, that there was an eruption of included Air or steams, and, above the surface of the Wine, there appear'd, to a pretty height, a certain white smoak almost like a mist, and then gradually vanished: The Wine continued well-tasted, and was a little rough upon the tongue, but not at all sowre.

The Bolt-head was seal'd up again Iuly the sixth 1671, and so set by 'till August the fifth 1672, at which time it was open'd again, and then the Wine did still tast very well.

Iune the twenty sixth 1673, the Bolt-head with the same Claret-wine was open'd, and was found very good, and was seal'd up again.

October the eleventh 1674, the same Claret-wine was open'd again, [Page 17] and appear'd of a good colour, not sowre, but seem'd somewhat less spi­rituous than other good Claret-wine, perhaps because of the Cold weather.

This, and the foregoing Trial a­bout the Preservation of Ale, were made in Mr. Oldenburg's House and Presence.

FINIS.

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