CHAP. I. Concerning Motion, and its Original.

AS an Introduction to what follows, I shall briefly set down some Observations touching Motion of Created Ma­terial Beings; for I shall not in this place meddle with those more Noble [Page 2] Beings of Angelical or Spiritual Na­tures, nor the Humane Soul, which is a Subject of another and higher nature, and not to be measured by those ordinary Rules or Reasons that con­cern Bodies, Matter, and Material Natures.

We may generally find in all Mate­rial Beings the thing called Motion; in some of one kind, in some of ano­ther; some more simple, some more complexed and various; some more conspicuous to sense, as Local Motion; some less conspicuous, as Generation and Alteration; some things are moved by others, some things seem to have the Principle or Original of motion in themselves, which communicates mo­tion to the Subject wherein that Prin­ciple resides, and also to other things by contact of their corporeity or vir­tue. And therefore Aristotle some­where as I remember, calls motion or endeavours of it, to be quasi vita quae­dam quae omnibus inest, quae Natura con­stant.

The primitive Principle or Cause of [Page 3] all Motion is the first Mover, the great and glorious Lord of Nature, from whom, as being so, all Motion is de­rived into created Beings.

1. By way of causality; those cre­ated Beings that seem to have the im­mediate Principle of Motions in them­selves, have that Principle from his Fiat and Institution. And,

2. By way of Concurrence and Con­comitance. There is a perpetual flux from that Fountain of Being that pre­serves and sustains those Principles of Motion which he at first lodged in cre­ated Beings, according to their seve­ral ranks, kinds and natures, and in­stituted Durations; and if this Con­course should withdraw it self but one moment, all the Motion of created Beings would cease and expire.

Matter it self simply considered as such, though it be susceptive of Moti­on (as we daily see) is not the imme­diate principle of Motion in those sub­jects that seem to be self-moving, or primitive Movents of other things, according to that Law of Nature in­stituted [Page 4] by the Soveraign Lord thereof.

And this seems apparent, among other Reasons, by these that follow.

1. Because Matter in it self, and simply considered, seems to be meerly passive, and receptive of active im­pressions from something else: It is true, one portion of Matter once set in Motion, will by contact put another portion of Matter into Motion. But we are not now upon the search of in­termediate Instrumentals of Motion, but upon the search of the Principles of such Motions which seem primi­tively and immediately to be elicited in any Physical Subject.

2. Because Matter simply considered, seems to be one kind of uniform Enti­ty, but diversified by its Forms, Qua­lities and Modifications, as Weight, Colour, Hardness, Softness, &c. The Matter of a piece of Gold, and of a piece of Wood, abstractively consi­dered, seems to be the Materia prima of the Ancients, and of the same nature; and consequently, if Matter simply considered were the immediate active [Page 5] principle of Motion, the Motions of all things would be as simple and uni­form as the Matter it self. But we see by daily experience that there are Mo­tions of several Subjects, which have the immediate principle of their Mo­tion in and from themselves, or some­what within them that obtains vicem Moventis, and are various, differing, differently exerted, and differently ter­minated from the Motions of other Bodies.

Therefore if there be any things in Nature, that have their Principle of Motion in themselves, we must find out if we can, somewhat besides Matter, that is the immediate root or spring of it.

It is true, the great Master in Natu­ral Philosophy, Aristotle, tells us, that whatsoever is moved, is moved by another, which would make one sup­pose that he thought there were no im­mediate self-moving principle in those Beings we call Automata, but only the first Mover; and truly with respect to the Soveraign Cause of all things, [Page 6] that every thing is moved by him that is unmoveable, as I have before shew­ed, cannot be questioned.

But that there are created Beings, that by the powerful and soveraign In­stitution of Almighty God, have an immediate Principle of Motion in and from themselves, is beyond Dispute.

A Brute Beast possibly may be put immediately into Motion by his Ap­petite, and that Appetite excited by the presence of an Object; and here the Object hath (as I may call it) a Moral Principle of Motion exciting the Appetite, moving the Brute to a nearer approach to the Object. But then in the Gressus Brutalis, it is some­what within him that gives the Local Motion it self, namely, the Brutalis Anima.

And the same is evident in the Moti­ons of Augmentation and Conforma­tion of Vegetables, the motions of Ascent and Calefaction in Fire, the Motions of Attraction and Aversation in Magnetical Bodies, and the very Motion of Descent in heavy Bodies; [Page 7] and infinite more instances of Physical Bodies, which have an intrinsick principle of exciting and communica­ting Motion to the Subjects of their in­existence, and to other things: Now touching this internal immediate prin­ciple of Motion, is this Enquiry upon which I am.

CHAP. II. A farther Disquisition touching the immediate Cause of Motion.

IN the former Chapter I have sup­posed these two things. 1. That there are some things that have an active self-moving Principle lodged within them. 2. That Matter simply considered, is not that immediate self-moving Principle: It remaines there­fore to be enquired what that Princi­ple is.

The ancient Bi-partition of created Beings was into Substance and Acci­dent. [Page 8] But this seems to me to be too narrow (I am still speaking of created material Existences) and I shall not be ashamed to own Helmont for my In­structer herein, because he speaks with great evidence of Reason.

There seems therefore to be a third kind of Existence or Entity participa­ting in some respect of the nature of both, and yet differing in other re­spects from both; for indeed it is an Entity among created Beings belong­ing to Matter, far more noble than ei­ther of the two former, and is that which giveth Life, Vigor, Activity, and Motion, immediately next under the Lord of Nature, to every self-mo­ving Being.

And this Entity I call Vis, or Virtus activa, superadded to Matter, and gi­ving immediately those Motions to it, that are specifically appropriate to that Vis, or Virtus Activa, and without which, Matter would be stupid, dull, unactive, and alwayes at rest in it self, unless accidentally moved ab extrinseco.

And although those Vires or Virtu­tes [Page 9] activae, the immediate Principles of Motion in such things as are Auto­mata, are various, and infinitely di­versified, yet I shall instance but in few; which nevertheless will be suffi­cient to render my self intelligible in what I say. And those are principal­ly of two sorts; the first of those (the noblest below the humane Soul) are those Vires, or Virtutes Essentiales, that are the principal Constituents of vital or substantial Forms. The second are those which are usually called active qualities, which seem to be of a lower nature and allay than the former.

Under the first of these Ranks, there are different Classes, not only gradually, but essentially more or less perfect than others, viz. first, the Vis sentiens & ani­malis of Animals. 2. The Vis vegetans & vitalis of Vegetables, and possibly of many Minerals. 3. The Vis combustiva & calefactiva of Fire. 4. The Vis attractiva, directiva & communicativa of Magneti­cal Bodies.

These Virtutes or Vires Essentiales even of the noblest sort (I mean below [Page 10] the humane nature) have this prehe­minence above the Matter or Sub­stance whereunto they are united, that they are the immediate, vital, movent principle, that gives a kind of Life or Motion to the Subject wherein they exist, which would otherwise be desti­tute of Life or Motion from it self.

Whether these Vires or Virtutes Es­sentiales are in themselves defectible or not, may be questioned: some have thought that they have certain Termini Temporales of their Existence, and Operations in themselves simply and abstractively considered, and in pro­cess of time languish and finally ex­pire and cease, as the energy of the Spring of a Watch in its evolution, grows languid, and at last utterly ceas­eth from any farther evolution or mo­tion. Others have thought, and with great evidence of Reason, that there is no decay or natural terminati­on of the Vis or Energia Essentialis it self, but only by the decay or defecti­bility, or dissolution of the material Hypostasis to which it is united, or of [Page 11] the Organs which it useth in its opera­tions; which being compounded Bo­dies, are subject to decay and dissoluti­on. And therefore the Philosopher tells us, that if an old man had a young mans eye, he would see as well as in his Youth; for the decay is not in the Visive Faculty, or Vis or Vir­tus Essentialis sentiens; but in the Or­gan, or Subject, or Substratum of its Operation or Inexistence.

But in some respects it is inferiour to Matter, and seems to participate of the nature of Accidents; as for in­stance, It necessarily according to the common Laws of Nature, requires a material Hypostasis or Subject in which it may inexist, and to which it may be united: thus the Vis Sentiens & Ani­malis is immediately united to the Animal Spirits, or the most refined parts of the Animal Nature. The Vis Vegetans Vitalis of Vegetables is immediately united to the Vital Spi­rits and Succus Vitalis of Vegetables. As to Fire, whether the Vis Ignea have a proper Hypostasis of its own to which [Page 12] it is united (as the Vis Sentiens hath) or whether it hath no other Substratum but the Body in which it is, as the Cole or Iron, or as the common Body of the Air it self, through which it is universally diffused, may, I con­fess, be questionable; yet certainly it hath some Hypostasis, to which it is uni­ted, and primitively inexists, and with­out which, it seems it cannot be.

2. Whereas no portion of Matter is lost in Nature, or annihilable but by Omnipotence, those Vires Essentiales are in their individuals extinguished and lost, and no where in Nature up­on the destruction, dissipation or dis­solution of the necessary Hypostasis or Subject of their inexistence: When the Animal Spirits are wholly dissipa­ted or dissolved, the Vis Sentiens of that Animal is lost, and no where: When water is thrown upon the Cole of Fire, the Vis Ignea that was in it, is extinct and nullibi, and (as it seems) doth not facessere in elementum commu­ne Ignis, at least if it have not a spe­cial Hypostasis of its own to which it is [Page 13] united; and when the Magnet is burnt in the Fire, the Vis Magnetica in it is ex­tinct. And the same is to be said of that other more ignoble Principle of Motion hereafter mentioned, viz. Active Qualities.

And this, as I think, gives us a true notion of the Souls of Brutes, the Forms of Vegetables, of Fire, and other substantial Forms below the hu­mane Soul.

If any should ask me what I take the Soul of a brute animal to be, I should say, it consisted of two essen­tial parts; the one, this active Vis, or Virtus Sentiens Animalis, the Root and Fountain of all its motions, of Sensa­tion, Perception, Phantasie, Appe­tition, and Local Motion. And the other is the immediate Hypostasis or Substratum in which this Vis Vitalis Sentiens ▪ primitively inexists, and to which it is primitively united, and by which it communicates it self to the whole Compositum; and these are some select Crasis or Portion of the A­nimal Spirits: For the Animal Na­ture [Page 14] being a more curious piece than inferiour Subsistences, and fuller of variety, therefore there is a more ela­borate and curious method of the union of its Essentials than in others: And next to Animals, there is a more cu­rious method of union and colligation of the Virtus Vitalis of Vegetables to the more pure and subtil vital Spirits, or Latex Vitalis of Vegetables.

But the Vis Ignea and the Vis Mag­netica seem to be immediately united to the whole Fiery or Magnetical Mass: But yet still the activity of both is owing not to the bare Hypo­stasis or Substratum wherein it is lodg­ed, but to that incorporeal force, virtue or energy which acts in it, up­on it and by it.

And upon this accompt Aristotle is to be understood, when in 1. De Ani­ma, he stiles the Souls of Brutes to be incorporeal, and yet in other places calls them substantial, viz. they are im­material and incorporeal with relation to the Vis or Virtus Essentialis activa, which is the regnant and noblest part [Page 15] of them; but they are substantial, and not only so, but material in relation to the prima Hypostasis or Primum Sub­stratum, the Animal Spirits, whereunto this Vis Activa is united, or rather some Nodus or concrement of a refined Substance, which is as it were the root or Focus of these Spirits, that like so many Branches, are derived from it, through the Nerves, and by them communicated to the whole Composi­tum.

And although I do here industri­ously omit the Examination of the Nature of the Humane or Reasonable Soul; yet I cannot omit this special observation of the discrimination of the Humane Soul from the Souls of Brutes, viz. that although the appro­priate faculties of the Sentient or Ani­mal Soul be admitted indefectible in themselves, yet their prima Hypostasis, or immediate subject of their inexist­ence is corruptible, and subject to dis­sipation; but the appropriate powers or faculties of the reasonable Soul, namely, Intellect and Will, are not [Page 16] only indefectible powers, but also the prima Hypostasis or primum Substratum of their inexistence is by the Divine Or­dination an indefectible Substratum; namely a pure, immaterial and incor­ruptible Substance, and the union thereunto indissoluble; whereby it comes to pass that the Humane Soul is immortal, and preserved both in its Essence, Existence, Personality and in duration after the dissolution of the Body. 1. Its Virtus or Vis is in­defectible. 2. The Prima Hypostasis incorruptible. 3. The Union of both indissoluble by natural power.

And thus far concerning the first sort of Active Principles in self-mo­ving Automata.

2. The second sort of motive Principles are Active Qualities, as they are commonly called; which, though possibly some of them may be the same with the former, essentiating Active Forms, yet some may be such as are of a second and more inferiour allay, as pro­ceeding from the primitive forms themselves.

[Page 17]I shall instance in two only. 1. In that of Heat. 2. In that of Gra­vity.

As to the former, it is evident that Heat (not only that which is so to the touch, but is such virtually, as in Vegetables and Minerals) hath a pow­er of exciting Motion both in the Sub­ject of its inexistence, and in other Sub­jects, as appears in the Fermentation of Liquors and other things which are put into motion by that virtual heat that resides in its particles, though not hot to the touch.

Whether Cold be of any positive nature, and so have a positive activi­ty of its own, or whether it be an absence only of heat, either totally, as in summè frigidis, if any such be; or partially, according to the degrees of heat abated or removed, I shall not here dispute; for I only propound some Instances, to render what I write intelligible.

2. As to Gravity, or that Principle in heavy bodies that inclines them ab intrinseco, to descend, this seems to be [Page 18] a quality of most tangible bodies that we converse with, if not of all; for some contend that there is no such thing in nature as simple Levity (at least in any thing but Fire) but only some bodies are minus gravia than o­thers, and urged to ascend by the pres­sure or circumpulsion of other bodies more heavy; this is not my business at this time to examine.

This Gravity I take to be a quality intrinsick to heavy bodies at least, in our inferiour System of the world.

Gravitation, which is a kind of se­cond act, may not altogether impro­perly be applied to motions of diffe­rent terminations, because it seems to be only nisus or conatus ad motum, which may have different terminati­ons; viz. upward, or downward, or laterally, and arise from different causes; but Gravity it self, as it im­ports a disposition, propension or in­clination in heavy bodies to descend, is not unfitly stiled a quality, and an in­trinsick quality.

For we may observe in the motions [Page 19] of natural bodies, some are from an extrinsecal cause or accidental; some­times arising from the pressure of other bodies, sometimes from the position of the bodies themselves; as Water will be driven up perpendicularly by a for­cer; as in Water-Engines; it will move collaterally or per declive, by rea­son of its own fluid nature, or by its position upon a declining Plain. But when all Obstacles of that nature are removed, a heavy body, as such, will move by a right Line to the Center, from that inherent quality of gravity, which is intrinsick to it, and puts it into motion; so that I am unjustly blamed for saying Gravity is a quality inclining bodies to descend to the Cen­ter, and yet at the same time saying, that it is not improper to say that things may gravitate upward or late­rally, as well as downward; for when heavy bodies have another terminati­on than downward, it is by reason of some other intervention of some exter­nal cause, or from some other proper­ty in bodies, accompanying their Gra­vity, [Page 20] as Fluidity in Water or Air, which gives them a Nisus ad motum (which is gravitation) of a differing termination from that of bodies pure­ly considered as heavy. But when the motion proceeds simply and solely from that active quality of gravity, its nisus ad motum, which is its gravitation, is simply in linea recta ad centrum, which I often call a central motion or direction: This any fair Remarker might have easily seen, without char­ging the Second Chapter of the Essay with a contradiction, where indeed there is none.

And therefore in this place I cannot chuse but take notice of two extreams in the modern Philosophy: Some are so wholly intent upon vital and pla­stick Principles, that they contend even almost against all Mechanical motions of Bodies, which I shall have occasion hereafter to meet with.

Again, Others are so greatly taken up with the thoughts of Matter and Mechanical Motions, that they whol­ly exterminate any intrinsick Princi­ples [Page 21] of motion, and resolve them whol­ly into Matter and its modifications, and Mechanism and Mechanical moti­ons; and therefore,

1. They suppose that there are no such things as I call Active Forms (at least excepting the Humane Soul, though some venture hard at that also) but that all Active Forms and their Ori­ginals are only various modifications of Matter, as Size, Figure, Position, Texture, &c. This I think is impossi­ble to be true; for though the Modifi­cations of Matter may give variety of accidental or external Forms, natu­rally arising from the texture of Mat­ter, as Figure, Colour, &c. And those various modifications may in relation not only to the powers of the Senti­ent Faculty, but to other Bodies, make various impressions, as we see is done in some tangible effects; as by smooth­ness, roughness, hardness, softness, sharpness, bluntness, and the like: whereby sometimes other bodies are affected; yet they can never arrive to those greater activities which we see [Page 22] in Physical Bodies, as Sense, Life, Pri­mitive Motions of several kinds, nor can be productive of the principles thereof; for the modifications of Mat­ter can never raise it to such an activi­ty, as of it self it is not capable of, but requires the union of some nobler active entity to quicken and actuate it.

2. They suppose that all the most noble motions, as well of Sense as Life in Animals and Vegetables, are nothing else but Mechanism, and not from any intrinsick active principle, which we usually call the sentient and vegetable Soul; nay, some by a vain petulancy have gone so far as to re­solve the noble faculties and motions of the rational Soul, as Intellection, Ratiocination and Memory, into a bare Mechanism, and Modification, and Motion of Particles of Matter, such extravagancies as these need no other confutation but our very Senses, in the observation of the curious pro­perties, instincts, operations and mo­tions of the animal and vegetable souls [Page 23] and faculties, and the unevident and unintelligible explications that these men offer for the support of their Sup­positions; which is not my business here at large to examine.

Now touching the production of these active self-moving Principles, which I call Vires, or Virtutes activae.

1. As to their primitive institution and production, there cannot possibly, as I think, be assigned any other than that constitution, institution and communication which they received from the great Creator of all things, and that Law which he annexed and gave them in their first forma­tion.

2. But as to the subsequent and physical production of these active principles, in the common and or­dinary track of Nature, they are various, according to the methods setled by the same Divine Law; such as are Generation, the Irradiation of the Heavens and Heavenly Bo­dies, especially the Sun, the various mixtures of simple and compounded [Page 24] bodies, and therewith of their essen­tial Forms and active Qualities, whereby there arise many times such Forms and Qualities as are some­times called equivocal, anomalous, or of various modifications. But the origination of Forms and Active Qua­lities, is a large Theme, and not in­tended to be prosecuted farther by me in this place.

CHAP. III. Concerning some other more univer­sal or common Causes assigned of Motions, viz. Anima Mundi, Spiritus Naturae, & Principia Hylarchica.

TO solve or give an account of divers motions in Nature, there have been those, that not content with the particular inherent active Principles in particular Subjects, as is mentioned in the former Chapters, have supposed certain more Catho­lick, and indeed nobler Existences, that manage the various Phaenomena in the Universe.

Plato and his School and after him, the Arabian Philosophers, especially Avicen, supposed an intelligent Na­ture subordinate to Almighty God, to preside and manage the Universe; [Page 26] which they call Anima Mundi, as they assign one common intelligent Nature, and depute it to the excita­tion, action and regiment of the hu­mane Soul in his intellective opera­tion, which they call intellectus A­gens.

Others that have assigned several Systemes of the world, each having a special Province, which they stile Vortices, or Systemata, assign a certain common intelligent Nature to be, as it were, the common Soul of every particular Vortex, and thus our Vortex, whose Center they suppose to be the Sun, and the terms of extent to reach the remotest Limits of Saturn, and his Orb hath its Anima vorticis for the re­giment of the Phaenomena and motions within that Vortex.

Others again have substituted ano­ther Principle, not altogether unlike the first; but differing in name, and some qualifications. This they call Principium Hylarchicum, and sometimes Spiritus Naturae, which though they make not an intelligent being, yet [Page 27] they make it plastick, vital, incorpo­real, and possibly sentient; but how­soever accommodated to the regiment of Matter in the best and most order­ly and convenient way; and this I take it, they suppose a subordinate regent principle, somewhat resem­bling the Archeus of Helmont, which is supposed a middle principle, inter­vening between the Souls of Animals and their Body, and an immediate active instrument in its motions and operations.

If by this Principium Hylarchicum, these men would understand the Sove­raign Creator and Lord of the world (as many of the Ancients understood the Anima mundi) who is intimately present with all his Works, and by a continual influx supports them in their being and motions, according to the most wise Laws and Institutions that he hath established for them and fixed in them: Or if by the Spiritus Naturae they understand those active essential Virtues communicated to every created Being by the Glorious [Page 28] God, and that statuminated Law, and Order, and Method, and Oeconomy which he hath given them, and ac­cording to which those active princi­ples which he hath planted in them, do exert and operate; this will be readily agreed to them as most ratio­nal, and in a great measure evident, not only to our Reason, but to our very Sense and Experience, and the Dispute about words, would cease, and be at rest.

But the substitution of such a vica­rious, immaterial, common Principle, to regulate, order, excite and govern Matter, and its motions subordinate to Almighty God, a common Spirit, and different from the particular active principles variously implanted in Physical Bodies, though it be a pleasant supposition, yet it is difficult, if not impossible to evince to any to­lerable satisfaction. Only I must needs say, that as Suppositions of this nature, that are founded upon Notions, are for the most part unaccessible by those common Media whereby things are [Page 29] to be proved to humane understand­ing; so upon the same account they are difficult to be confuted: If any man should tell me that the Moon were a Globe of Water, as he could never prove it, so I could ne­ver disprove it, unless I had such Media of access to that Body, that could to my Sense and Experience confute it; and therefore in such cases the proof must be cast upon the assertor

Yet there seem to be some things that render this Supposition not very credible.

1. That it seems an unnecessary multiplication of beings, whose Of­fices are well enough supplied with­out them; namely, by the energy of the glorious God, and those special active Principles that he hath lodged in almost all created Natures, and those Institutions and Laws that he hath alligated and annexed to the par­ticular Works of his Creation, and the Systemes and Syntaxes of the World.

2. But principally upon a strict ex­amination, [Page 30] it will appear that most of these Phaenomena in nature and motion, are performed by the active principles, residing in particular Subjects, or by the usual and necessary Mechanism of bodies, without our calling to their immediate performance this supposed Spirit of nature.

3. Again, It is very difficult to form to our selves a notion of this Spirits Nature, that may have any probable certainty: let us take but these few difficulties.

1. Is it a distinct, self-subsisting Spirit, separated from Matter? or is it a kind of common Soul or Form residing in the Universe, as the Soul of a Brute resides in his Body, and united to it by a wonderful union? If it be the former, it is a kind of Angelick Nature, not united to Mat­ter, but acting separately upon it, subsisting without it, and is in all probability an Intelligence. If the latter, it were fit to know whether it were an immaterial Form, as the Humane Soul; and then perchance [Page 31] we should give it too great a prefe­rence: Or is it a material Form, as that of Brutes? And then it will be worth knowing whether it hath the like perfection of Sense, or be of a lower allay, and only vital, like those of Vegetables. Or is it a kind of connatural Sense, suted to all material Beings, together with a sentient per­ception and appetite, proportionate to the Nature of every material or substantial created being, as Campa­nella and our learned Countriman hath lately asserted. Whatever it be, we are perfectly in the dark to form any conception of it with any tolerable evidence or satisfaction.

Again 2. Are there other parti­cular or specifical Forms in the seve­rall Classes of material Existences, as Animals, Vegetables, Minerals, &c. that exert the several operations that seem specifical to their Natures, but individuated in the several indi­vidual existences, Or is this com­mon spirit of Nature that which ex­erts all these Operations which are [Page 32] therefore only diversified by the diver­sification of the compositions of those bodies in which and through which they are exerted, as the common Bel­lows in the Organ; and the breath thereof gives the various sounds in the Organ-Pipe, according to their Figures, Stops or Amplitudes? If we suppose the former, we seem to multiply Entities without necessity; if the latter, we destroy all that we are building, and make all the Ani­mals, and Vegetables, and Material Beings in the Universe (if this Spirit be universal) or in this lower World (if singly belonging to this Systeme) to be nothing else but pure mecha­nical pieces, without any sentient or vital principle of their own, but only are the dead Tools and Instru­ments of this spirit of Nature; such difficulties as these would be cleared, to give us some Idea or probable fix­ed notion of this Spirit of Nature, or Hylarchical Principle.

But now if we should suppose the interposition of this common Spirit [Page 33] of Nature in some Phaenomena or mo­tions of particular Bodies, yet it seems necessary for us to suppose these two things in the exertions thereof.

1. That it doth not immediately in­terpose, unless upon great emergencies, and to deliver the things of Nature from some important inconvenience, which without so effectual an inter­position would befall them; as to pre­serve the continuity of the parts of the Universe, or avoid vacuity, and the like, and not upon those little oc­casions which are of no consideration and importance, whether they be re­lieved or supplied or not; such as are the emergency of a Rundle of light Wood from the bottom of the Water, or the sustaining of a weight, or attra­ction by the Embolus of a Syringe or Air-Pump, or the keeping up of the Valve or Operculum in the lower end of a Tube immersed in Water. These and the like Instances are of so small concernment to the good of the Uni­verse, or to the Nature of Physical Bodies, that they were scarce worthy [Page 34] the access of the noble Spirit of Na­ture; Nodi vix tali vindice digni.

2. That if this Spirit of Nature doth at any time interpose, yet it rare­ly, if at all, acts by violent or con­vulsive motions, but pacately, and as much as may be, in consonance to the regular disposition of Bodies; and therefore it is, that even in Animals, where their motion is exerted by a clear, internal, vital, sentient princi­ple, it doth for the most part act re­gularly, and in the best Mechanism ima­ginable, their Bodies, Nerves, Bones, Muscles are ordered by a rare and ex­cellent Mechanism for the exerting of those motions, and the motions themselves performed by those Or­gans, by the explosion and retraction of the Spirits in their several vessels, with admirable order and artifice, as will appear to any that will bestow the pains to read Galen, De usu Partium, and Aristotle, De Gressu Animalium; and therefore we have much more rea­son to think that this supposed noble Spirit, the Spirit of Nature, acts not [Page 35] at random, or convulsively, or irre­gularly, but according to the best Rules and mechanical methods appli­cable to such motions as it doth occa­sionally exert.

So that if we should never so much allow of the Spirit of Nature, and its interpositions, yet still the necessary instruments, modes and methods of its motion according to Mechanical Rules, must still be sought after.

For it would be a pitiful refuge for a man pretending to Philosophy, to give this general solution to all Phaeno­mena of Nature, that this is so, be­cause the Spirit of Nature thus orders it; without giving some probable ac­count of the particular means or me­thod by which the Spirit of Nature ef­fects it, and likewise of the end, use and design of the Spirit of Nature in what it thus effects.

CHAP. IV. Touching Rarefaction and Conden­sation, and their kinds.

BEcause much hath been said by others touching Rarity and Den­sity of Physical Bodies, which I call Affections, Passions or Qualities of Physical Bodies; and it may be con­ducible to the solution of many Phy­sical Phaenomena; and to the clearing of my apprehensions concerning it, and to the answering of most of the Objections of any weight, made a­gainst the Suppositions which I have stated, in the two Pamphlets above mentioned, I will endeavour to give that account concerning this matter that seems reasonable to me; though I must confess it is possibly one of the abstrusest Subjects in Natural Philo­sophy, wherein I shall observe as near as I can, this Method.

1. To consider the several consi­stence of Bodies.

2. To shew the various kinds of Rarefaction and Condensation of those Bodies.

3. To what kinds of Bodies, and to what kinds of Rarefaction and Con­densation this Argument in hand is ap­plicable; that so we may come closer to the business in question, and speak ad idem.

As to the first and second, Sir Fran­cis Bacon in his Historia Densi & Rari, hath in a great measure fitted them to my hand; whose Method I shall here­in follow.

1. Of Bodies, some seem to be pro­perly called Tangible, some Pneuma­tica; which though they are not Spi­rits, nor void of Matter, no, nor yet totally imperceptible to the Touch, yet are more subtil, and less obvious by any gross contact, to that Sense, and therefore may be called Spirita­lia.

Of the former sort, some are more fixt, and of a more setled consistence, [Page 38] as Gold, Iron, Stone, Wood, &c. Others are fluid, either from the texture of their Nature; as Water, Oyl, Mercury; or by Art or Accident, as Gold, Sil­ver, Lead, &c. in Fusion or Dissolu­tion.

Of the latter sort, viz. Pneumatica, there are several kinds, and of vari­ous degrees of exaltation, as Aether, Air, Flame, Spirits of Animals or Ve­getables, Smoke, Vapors, &c.

Although tangible Bodies may be capable of Rarefaction and Condensa­tion, at least in some of the accep­tations thereof hereafter described, yet I shall not much meddle with them, unless it be such as be fluid, because not to my present purpose; and because what is hereafter said touching the Rarefaction or Conden­sation of some Fluids, and of those Pneumatica, will in some measure ex­plicate somewhat concerning the Condensation or Rarefaction of other tangible Bodies.

2. Touching Rarefaction and Con­densation, thus much first in general [Page 39] is to be said, Rarefaction is when the same Body, or at least portion of ma­terial Substance, takes up a greater external dimension, or a larger ap­pearing trine dimension, viz. of breadth, length and depth than it had before.

And on the contrary, Condensation is when the same Body or portion of material Substance takes up a less ex­ternal dimension than it had before; this may suffice as the common Phae­nomenon of Rarefaction and Condensa­tion, as it stands objected to our sense; though when we come to particu­lars, this general sensible description of either will not serve alwayes the Subject, nor sufficiently explicate it.

Some Appearances in Bodies look like Rarefaction, which indeed are not such, but only in appearance; such as are Augmentation of Bodies by an unperceptible accession of new mat­ter, as in Augmentation; sometimes by assimilation of contiguous matter into its own consistence, sometimes by the apertures or distraction of the [Page 40] parts of a Body, and intrusion or in­termission, or attraction of other Mat­ter of a different Nature, Quality, or Texture, or of the same Nature, Quality or Texture with it self; these are not truly those kinds of Rarefacti­ons whereof our enquiry is instituted; for though the Moles or Bulk seem to be extended and enlarged, yet the true Bulk of the same Matter is the same as before, though it may be un­der a different configuration or po­sition.

Again, on the contrary, some ap­pearances in Bodies, look like Con­densation; but in truth are not such; as when part of a Body is emitted ei­ther by perspiration or dissolution of some of its more subtil parts, where­by that which remaineth, taketh up less circuit or bulk, or where some of its parts are first subtilized, and then dismissed, and some other Instances of like kind may be given; but these are not true and real Condensations; for the entire matter remaines not in the Bo­dy condensed, as was before, but is [Page 41] diminished: These therefore are not the Rarefactions and Condensations whereof the Enquiry proceeds; for the same Body in both instances hold the same true space it had before, though the extream appearing Limits seem to be altered.

3. The Question therefore in hand is, touching that kind of Rarefaction, where the same Body or portion of material Substance, without accessi­on of more or other bodily matter, yet takes up a larger space than it did before.

2. And where it doth not only take up a larger exterior compass, circuit or superficies; but where it al­so fills those intrinsick spaces which are within the circuit of that extent, as fully as it did before. For if for the purpose, a portion of Air of a Cubique Figure six inches square, do swell to a Cubique Dimension of seven inches square, yet if in that very dilatation there be as great a disjunction or divul­sion of the parts of the Air within the cubique space of six inches, as amounts [Page 42] to that external accession of one inch, whereby it becomes a Cube of seven inches square, here is no true Rarefa­ction, nor is the space enlarged, but only the Figure of the same Body, and of its Extention altered.

If an Artificer take a little Cylinder of Silver of two inches long, and half an inch round, and guild it, he will by his Art draw out this little Bar into 40 yards or more of fine Silver Thred, though the length be encrea­sed, yet the breadth is diminished, and the Silver Thred takes up no more true extent of its trine dimension than it had before; nay, which is remarka­ble, the extent of the Superficies of the Silver is not enlarged, though the figure be altered; which appears by this, that every part of the Superfi­cies of the Silver thred will conti­nue guilt as it was in the Superficies of the Ingot.

And upon the same account it is on the other side, when a Body or portion of material Substance is said truly to be condensed.

[Page 43]1. It must be the same portion of matter that was before, without any diminution of its parts, or of any mat­ter in it that contributed to its former Moles.

2. The same matter without any diminution, must really take up less room or space than it did before; for if it only take up a less Superficies or external extent, yet withal it makes up spaces or porosities within the compass of that external extent, which before was not filled by it self, but either was simply empty of any bo­dy, or only filled with such a body as now recedes, and gives way to the body supposed to be condensed, to take it up, then here is only a change of the space it had before, and of its configuration▪ not a less space really taken up as commensurate to that body that is supposed to be condensed. So that the Question between the ancient and modern Philosophy, is not so much de modo, how Condensa­tion or Rarefaction is made, as con­cerning the thing it self, whether re­ally [Page 44] and truly there be any such thing or affection in bodies as Rarefaction and Condensation; the latter Philosophy in truth denying the thing, when they give it such an explication as really and in truth consists not with it; as we shall see hereafter.

This being therefore the state of the Notion of Rarefaction and Conden­sation, in its true explication, we are to consider, what bodies, or motions in bodies are such as are applicable to the Argument in hand.

The special Instances that I shall use are these.

1. The Rarefaction or Condensation of bodies by Transmutation; thus Water by Rarefaction is sometimes changed into Air, which hath there­by a greater extension than it had be­fore by about 900 times; and Air by Condensation is changed into Water, and thereby loseth by contraction a like proportion of space than it had before. Thus Aristotle in 4. Phys. cap. 9. and the great Verulam, in Historia Densi & Rari, pag. 88.

[Page 45]2. The Rarefaction that is caused by external violence, as in the Air-Pump, in the Cacabus Evacuatorius, and the Magdeburg Engin, this is a Rare­faction by Tension, whereby the Air is dilated, not only in its external Bulk, but in all the parts of it, and in its internal, as well as external parts and dimensions. And thus Mersennus and others tell us, Air may be dila­ted to near 70 times its former and natural extent.

3. The Condensation that is made by Compression: Some there are that think Water is thus contractible and condensible by compression: The same Verulam, ubi supra, pag. 99. tells us, that taking a Leaden hollow Globe, and fill it with Water, and then strongly stop the Orifice which took in the Water, and compress the Globe in a strong Presser, whereby it may be reduced to an eighth part of its former dimension, the Water will sustain that contraction; but if it be pressed farther, the Water will dis­charge it self through the Globe ad [Page 46] modum parvi imbris. It is not impossi­ble but it might do so from its first compression, though the streams, by reason of their exility, were imper­ceptible to the Eye, as the emanation of effluvia through the pores of the bodies of Animals, electrical effluxes, or the Odors of Herbs; for Water, though fluid, seems very impatient of Condensation by compression; yet it is not impossible, if under a very strong pressure; but to the very eye it appears capable of dilatation by Tension in its discharge of it self by Bubbles, upon a strong Tension.

But howsoever it is with Water, it is apparent that Air is capable of condensation and contraction by com­pression; this appears visibly in the compression of the Air by Wind-Guns, and the careful injection of water by a well ordered Syringe in an empty Aeolipile, so that Air by these means may be contracted into a seventh, nay possibly a seventieth part of its natural space or dimen­sion.

[Page 47]4. The Rarefaction and consequen­tial dilatation of Bodies by Heat or Fire: Thus Water it self is rarefied and extended into Vapours by Heat. The Lord Verulam, ubi supra, pag. 28. gives us a notable Instance, by taking a Vial-Glass holding an ounce, filling it half full of Spirit of Wine, then ta­king an empty Bladder that held about 8 pints, and tying it about the neck of the Vial strictly, the Spirit of Wine heated upon the Coals, the Aura Spiritus Vini filled the Bladder, and yet only six penny weight of the Spirit of Wine spent, which did not amount to the 40th. part of a pint, yet filled the Bladder of 8 pints with its rarified Air. And although this Instance be in the Spirit of Wine, which is fuller of subtil Matter than the like quantity of Water, yet it will hold its proportion with the Fumes or Vapours of Water.

And of the like kind is the Rare­faction by Ignition in the Gunpow­der, where a grain of Gunpowder fired, will expand above a thousand [Page 48] times its former dimension and more.

But that which is most obvious to Sense, and most apposite to my pur­pose, and therefore will be the Sub­ject of most of my ensuing applicati­ons, is, the Rarefaction of Air by heat, whereby it may gain an expansion of above 70 times its natural size and dimension, as is easily found by the strong heating of a strong Brass con­cave Globe, which if the included Air have no vent, will break it, and if it have a vent, and after it is strongly heated, cast into a Vessel of Water, it will soon discover the pro­portion of its dilatation by the con­traction that it receives from the cold Water, and by the quantity of Water it sucks in upon that con­traction.

5. The Condensation and conse­quential contraction that the Air re­ceives by the constipation of it by Cold, especially after a strong dila­tation; but although there be no such preceding dilatation or expansion of the Air by heat, yet it is visible [Page 49] in Weather-Glasses, and other En­gines of that nature, that the Air is contracted in its dimension, by the ambient Cold, from what it usually hath at other times.

CHAP. V. Concerning the Phaenomena of Ra­refaction and Condensation apparent to Sense.

TO pursue all the Phaenomena of Condensation and Rarefaction in its full Latitude, were too long a bu­siness, and not so much conducible to my purpose: I shall therefore take up those Phaenomena that are apparent­ly evident to Sense in the Rarefaction and Condensation of Air; for the due discussion of that single Subject will give an estimate and explication of other Rarefactions and Condensations.

1. It is evident to our very Senses, that a smaller portion of Air, suppose [Page 50] a Cubique Foot in a Vessel, being ratified by heat, will take up a far greater space than it did before such application, and the like will be when it is done by Tension, as in the Air-Pump, and the Magdeburg-Engin; for when a great part of the Air is driven out by Heat, in the one Instance, and drawn out by Traction, in the other; yet it is evident to Sense, that the Receiver or other Vessel remains full of a very rare and extended Air; for sensibly no other Substance sup­plies it.

2. It is evident to Sense, that this distension of the Air is not only in the Extima Superficies, but in all the very internal parts of it; for it is ap­parent to our Sense, that it hath a vi­sible effect as well upon the Birds, Water, or other Body, placed in the middle of the Cavity of the Receiver, as in those that are conterminous to the Sides of it, as appears in those many Instances given by Mr. B. espe­cially in 21, 22, &c. Experiments. And unless the whole Body were ex­tended [Page 51] every where and every way, it were impossible that a little portion of Air included in a Bladder, should encrease its bulk by Heat, to ten times its extension, as it will do, and is ap­parent to our Sight by the ample di­stention of the Bladder.

3. It is apparent to our Sense, that if the Air be rarified by Heat in any close Vessel, as the Heat, which is the cause of its Rarefaction, decays, so the Air endeavours its contraction, to gain its primitive size, which it then attains, when the Heat is perfectly gone out, if it be not impeded by the closeness of the Vessel.

This is visible in Weather-Glasses of 22 inches long; whereby, when for the purpose, the Water riseth to ten Inches, and leaves twelve inches of Air in the Head of the Glass, the warm hand laid upon the Head of the Glass, will depress the Water, by expanding the included Air two or three inches; but the Hand being re­moved, the Air will contract it self to its former Staple, and so the [Page 52] Water will rise to ten, as before.

4. It is evident to Sense, that the Air contracting it self, doth by that which is called by some, Motus nexus, lay hold of the inward sides of a close Vessel containing and strictly impri­soning it; and if they be otherwise severable, yet the strong contraction of the filaments of the Air holds them together, as appears abundantly by the Instance of the Magdeburg Hemispheres, mentioned at large in the 18th. Chap­ter of the Observations upon the Tori­cellian Experiment, and other Instances of the like Nature, given in that Book.

5. It is evident to Sense, that in that strong cohesion of the Filaments of the Air to the sides of the Vessel, when by the decay of Heat, it con­tracts it self with a motus or conatus of restitution, and with it the ambient Vessel by a motus nexus, yet if a small degree of Heat be moved to the Ves­sel, that contraction is relaxed, and the Vessels fall asunder; and the like is done by the smallest admission of [Page 53] the free or solute Air, though through a Pin-hole; for by the Heat the in­cluded Air is again dilated, left lax, as before it grew cold, and by the ad­mission of foreign Air, the included Air is relieved gradually to that ex­pansion as is natural to it, and as it had before its Rarefaction or Condensa­tion.

6. It is evident to Sense, that upon the smallest Pin-hole made in the Ves­sel where the Air is, that thus con­tracts and endeavours its restitution, either upon Tension, or upon grow­ing cold after Rarefaction, the Air thus tensed or contracting it self, will greedily suck in the foreign Air, yea, or Water, for its relief against that Tension that it is under.

7. In Condensation of Air, especi­ally by compression, it is apparent, that the Air takes up, or may take up a far less room than is natural to it, as appears in Wind-guns or Aeoli­piles.

8. It is also apparent to Sense, that the compressed Air in those Instances, [Page 54] endeavours with great strength and force its relaxation from this com­pression, in so much as if it can get liberty, it will cast out a Bullet with great force in Wind-guns, and in Aeolipiles well made, and well char­ged with Water, by a Syringe it will throw up the Water above twenty foot high.

These Phaenomena are as evident to our Sense of Sight and Touch, as any thing we see or feel; and though there is difference among the Learned in the solution or manner of explication of these Phaenomena, yet the effects themselves are plain and sensible, and do give a sensible demonstration that surely there is some alteration of the state of this Body of the Air, or of its Texture or Fabrick under these various Appearances, which are usu­ally called Rarefaction and Condensa­tion. But whether they are really such, or how made or ordered, will be the Subject of farther Enquiry.

CHAP. VI. Concerning the various Solutions of Condensation and Rarefaction, and first, of that which is by sup­posed interspersed Vacuities.

RArity and Density of Bodies, al­though it terminate in a greater or lesser dimension or extent, which properly respects Quantity, yet they seem in themselves to be but various Passions, Affections or Qualities of Bodies arising from their different Textures, either more crass or more subtil: And Rarefaction or Condensa­tion of Bodies seems to be those several Motions towards these Qualities of Rarity or Density, caused for the most part by some external or adventitious Agent, which changeth and altereth the Texture of any Body whereby it assumes those Qualities of Rarity or [Page 56] Density different from its own natural constitution, and sutable to the varie­ty of the Texture they do for the time undergo.

There have been various Solutions or Explications of these apparent Phae­nomena of Condensation and Rarefaction, which I shall in the next place consider; holding my self to that of the Air, either by compression, in case of Condensation, or by expansion by Heat, or by Tension by force, in case of Rarefaction; because this In­stance of Rarefaction and Condensa­tion of the Air, is most obvious to Sense, and doth in a great measure explain the Rarefaction or Condensation or other Bodies capable of those Affections.

These Methods of Solutions of Ex­plications of Rarefaction or Condensa­tion that have been taken up by seve­ral parties, are principally three.

1. Of those that suppose the same to be performed by reason of intersper­sed Vacuities, Porosities, or Spaces, empty of all body interposed between aery particles, which in cases of Rare­faction, [Page 57] are made wider by a kind of divulsion or greater apertures of the particles of Air, or other bodies rari­fied, whereby the Interstitia of the aerie Particles are greater, and those empty interspersed Vacuities made lar­ger; and in case of Condensation, the aerie Particles are crouded closer to­gether, and those empty spaces or In­terstitia made less by reception of those particles of Air into those Vacuities, in a closer posture or conjunction than they were before such compression, constipation or condensation; and this I call the Epicurean Solution.

2. Of those that admit no Vacuities at all in the Universe, but that all places or spaces are full of some body or other, but that in the Rarefaction of the Air, whether by Heat (which I call simple Rarefection or Expan­sion) or by a forcible distraction or divulsion of the particles of such ra­refied or expanded body by force, which I call Tension, those particles of the extended or rarefied body, are removed to a greater distance one from [Page 58] another, and as they are so removed, other more subtil, corporeal particles do interpose gradually, and fill up those Interstitia; and in case of Conden­sation, the more subtil parts with which all bodies are furnished, but especially the Air, are driven out by compres­sion, and take up a temporary residence at least in the conterminous Air. And this I call the Cartesian Solution; though this, as shall be shewn, have some variation in the manner of its expli­cation.

But though these methods differ in the application to the matter in hand, yet they both much agree in this, that the first material Principles of Bodies are certain minute Corpuscles or A­toms; which, though they are really bodies, and therefore Mathematically divisible, yet they are so minute, that physically and actually they are indivisible; and therefore in them­selves hard and unfrangible into lesser portions. This I shall examine hereaf­ter in the seventh and eighth Chap­ters.

[Page 59]3. The third Solution is that of the ancient Philosophers, and some other of the Modern, which suppose that Rarity and Density are really natural Affections or Qualities of Physical bodies, and that Rarefaction is a real expansion of the very entire Moles of the body truly rarefied; and Con­densation is a real contraction of the whole dimension of the body con­densed, namely, where it is truly and formally a true Rarefaction or Conden­sation, as the Question is above sta­ted in the beginning of the Fourth Chapter? And this I call the Aristo­telian Solution; and seems to me the truest, in the manner hereafter de­described.

First therefore, Touching the first of these Solutions, by interspersed Va­cuities: This, though it doth in truth take away the true Notion of Rarefaction and Condensation, as it is before stated; for still the same body holds but the same quantity of space, though in different position or ubica­tion of its parts, yet I must needs say, [Page 60] were the supposition of interspersed Vacuities true, would in a great mea­sure (though not altogether) salve many of the Phaenomena of Rarefaction and Condensation.

But there are these two grand Ob­jections, that I think render this So­lution impossible to be true.

1. It seems to me utterly untrue, that there are any such interspersed Vacuities, wholly destitute of Body, either in the Air or any other Body, and herein the Cartesians and I agree. And that which renders this Suppo­sition untrue, is that excellent de­monstration improved by Sir K. Digby, in his History of Bodies.

If there were such interspersed Va­cuities, it must necessarily follow that those Bodies of an equal Superficies, that are more rare, must have more or greater interspersions of such Vacui­ties, than such as are more dense; or which is all one, the same Moles of body that is more dense, must needs have more of matter or body in it than that which is more rare; or which [Page 61] seems to be equally consequential, that where the body is more weighty, the same external Moles of the more weighty body must needs have more of body, and less of interspersed Va­cuities than that which is more light, where the external Moles of either is equal.

And therefore a Cubique Foot of Gold must have more of Body, and less of interspersed Vacuities than the like Cubique Foot of Silver, and that than the like Cubique Foot of Water; and that than the like Cu­bique Foot of Air.

The Lord Verulam, in his Historia Densi & Rari, pag. 8 & 9, by an exact computation, gives us the Estimate of the disproportion of Weight of the same extrinsick Moles of several bodies; whereby he finds that a por­tion of pure Gold reduced into a Cubical Figure or Moles, weighed 20 ^d weight, and the like Moles of of Mercury 19 ^d weight and 9 grains; the like Moles of Silver weighed 10 ^d weight and 21 grains; and the like [Page 62] Moles of Water weighed 1 ^d weight and 3 grains; and upon a like trial, pag. 20. found, that the heavier any solid body is, and more united its parts are, the lighter was the same body reduced into Dust (though close­ly compressed together) in compari­son to the weight of the same body before its pulverization.

His Experiment goes not so far as the disproportion between the weight or denseness of Air or Water, but Mersennus and some others that have been curious in this Computation, tell us, that the same extrinsick Moles of Water is about 14 times lighter than the like Moles of Mercury, and the same Moles of Air is at least 900 times, others say, 1300 times lighter than the like Moles of Water.

The consequence whereof is, that if we should suppose a Cubick inch or foot of Mercury to be entirely full without interspersed Vacuities or other Matter in it (which yet upon the ac­count given, wants much) it must follow that in one Cubique inch or [Page 63] foot, or other Moles of Air, for one particle of body, there must be 11699 parts of empty space, each of these spaces equal to the space that the real body of the Air takes up; such is the disproportion of the weight between the like quantity or Moles of Air to that of like Moles of Mercury, viz. as 1 to 11700.

The consequence whereof would be, that yet the Cubique foot, or inch, or other measure or a Vessel contain­ing nothing but Air, might receive a quantity of Mercury that bears pro­portion, as 11699 to 1, and a quan­tity of Water as bears the proportion of 899 to 1, without extruding any part of the included Air, or overfilling or breaking the Vessel wherein it is inclu­ded. And if we should suppose that in the common Air we breath in, there should be but 891 parts of Vacuities, for one part of true substantial Air (as there must be upon this supposition) all respiration would presently be ob­structed, and indeed all that Motion which we see, especially in Meteors.

[Page 64]But as this is prodigiously incredi­ble, so it is apparently untrue: For take a Tube full of Air, and stop it at one end, immerse the open end in­to Water, and press it down as low as may be, yet not one half of the Tube will be filled with Water; nay take an Aeolipile of Brass with a Sy­ringe to drive in the Water, it will with great difficulty receive into it ¾ parts of Water; and thereby the Air contracted into a quarter of its former room, and with great pains and force it may be, into a much less room; but never any pretended it could be compressed into the 899 ^th part of its former room; and yet thus it may be, and with great ease, be­cause here are 899 empty spaces which may receive the water with as much ease as if the Bottle or vessel were not empty only of Water or Air, but per­fectly empty of any other body, aba­ting only 1/900 of the room to receive the Air.

2. The Second difficulty in this Supposition seems to be this, that it [Page 65] doth not answer the Phaenomena, espe­cially in condensation of Air by pres­sure, as in Wind-Guns and Aeolipiles, which visibly with a great force en­deavours its restitution, as appears in the explosion of the Air in Wind-guns, and ejection of Water pressed into Aeolipiles; for the Air upon this Supposition, hath a free room far more than sufficient for its reception, and therefore hath no need of any such violence in its motion of restitution, it having 899 empty cavities, where­as it hath need but of 1/900 part thereof for its reception, and more vacuity can contribute nothing either to resist compression, or to cause a sensible force of restitution, because nothing can have no activity or motion.

3. Again, if Air or Water be strongly rarefied by Heat, we see it takes up a larger extention than be­fore it had, and that with such an energy and force, that it will break a strong Vessel inclosing it; which it could never do, were there any considerable interspersions of Vacui­ties; [Page 66] because the body of the Air would with much more ease break into those vacua Interstitia, which have no resistance against it, than it would or could force its room upon the ambient Vessel that containes it, and resists its dilatation with all the strength it hath. And this very rea­son doth as effectually conclude against the second Solution of Rarefaction by the admission of Materia Subtilis into the supposed Interstitia, if duly consi­dered.

CHAP. VII. Concerning the Second Solution of Rarefaction and Condensation, and its insufficiency.

I Come in the next place to consi­der the Second Solution above of­fered, which supposeth these things.

1. That there is no empty space or interspersed vacuity in the Air or any part of the Universe; with which I agree.

2. That the Principles of com­pounded bodies are certain minute Atomical Corpuscles, physically in­divisible, and yet for all this, these very minute bodies are some grosser, like little Globuli, ground to as small a magnitude as is naturally possible, and yet the Ramenta or Filings of these Globuli are smaller than the for­mer, and make that Constituent or Principle which they call Materia sub­tilis, [Page 68] which interposeth between other grosser Atoms or Corpuscles, and fil­leth up the Interstitia between them; this Supposition I deny, and shall shew my Reasons against it.

3. That in Rarefaction or Tension of the Air, or other Bodies capable of Rarefaction, there is only a separa­tion or disjunction of the parts there­of to a greater distance one from ano­ther, which doth not at all encrease its extension, but only varies the position or vicinity of its parts; and hereupon to fill the Interstitia between the parts thus divulsed, there is immitted into those Interstitia subtil matter, or those subtil Filings of the Globuli that fill those spaces which are therefore bor­rowed from the subtil matter of the other parts of circumjacent Air; or finally from the Aether, which seems to be the subtilest matter in Na­ture.

4. That in Condensation of the Air, &c. by compression that Subtilis­sima Materia that resided before with­in the body of that portion of Air, [Page 69] is by compression squeezed out, and driven into the conterminous Air, whereby that which we call the con­densed portion of Air and its parts come closer together, and take up less room or space than it seemed to have before; namely, in the external bulk or Superficies, though in truth and reality the Air it self thus see­mingly condensed, and its particles, take up really as much room or space as before, though the figure, and po­sition, and ubication of that space that it takes up now, is only altered by its secession into the spaces where­in the subtilissima materia now flown away, did formerly reside.

This Solution of Rarefaction and Condensation, I think is neither true, nor doth it in any measure answer the Phaenomena in Rarefaction or Condensa­tion.

First therefore, I think the very Supposition it self of these solute A­toms is but imaginary and the crea­ture of the Brain, and therefore I think may deserve the Title of Ido­lum [Page 70] Epicureum, or Cartesianum, never intended by the latter as any real Truth, but only as a Supposition, Engin or Medium to explicate the Phaenomena of Nature, though now unwarily enough taken up by many Virtuosi as a Truth.

1. It robs all bodies of any real or possible continuity without a mira­cle, or the substitution of some ce­menting matter, differing from A­toms or solute bodies, to hold the parts of the Universe together; for how can really separate bodies, such as the very least of Atoms are suppo­sed to be, have any continuity, or so much as mutual cohesion barely by contiguity? For as to the Atomi ha­matae, they savour too rankly of fiction and invention, and the Polar Magne­tism and difference of Sexes of Atoms seems as vain.

2. We see in many bodies not only a continuity, but a strong texture, whereby they will not readily be bro­ken, that yet at first arise from a thin watry substance or concrement, as the [Page 71] Nerves of Animals, the Wood of Trees, the Barks of Trees and Plants; as Withy, Flax, Nettles, nay the very Spiders Web, hath besides its continuity, a certain tenaciousness; so hath Water it self, as appears by the traction of the water in the longer Leg of a Si­phon; this tenaciousness, glutinous­ness, and strong cohesion of parts of bodies one to another, could never be by the apposition of solute particles one to another, though never so small, but from a kind of intrin­sick contexture of the bodies them­selves.

2. Upon this Supposition, it were necessary that all bodies should be equally hard, and equally weighty, and equally dense. Those Atoms, even those that are the most minute, that are the Constituents of the Ma­teria subtilissima, are yet supposed to be bodies, and essentially divisible, though not divided, nor indeed divi­sible physically by any force, and therefore hard and unfrangible; and therefore, if we should take a Vessel [Page 72] of a foot square filled with Air, this Moles, though we call it of Air, is yet really made up of those hard particles, and then how is it possible it should be soft to the touch any more than Brass or Steel? For the softness of dust of Gold or other solid Bodies, is not from the dust it self, but from the numerous interspersed particles of Air. Again this Cubique Vessel full of Air is entirely full of body, or not; if it be not, then this supposition must necessarily admit interspersed Vacuities; the thing that the whole Supposition of the Cartesians deny: But if it be full of body in every ima­ginable space thereof, why should not this Cubique Moles of Air thus con­stipated with a plenitude of body, be as weighty as the like Cube of wa­ter, yea, or Gold; for as to solidity, the Atomical bodies themselves in both, are of the same consistence, and all spaces are supposed full both in the Cubique foot of Air and Wa­ter, for excess of weight, is but the effect of excess of Matter or bodily substance.

[Page 73]4. Again, It is most certain that the smallest Atoms or Particles of matter, even the Ramenta that are supposed the Constituents of the Ma­teria subtilissima, are yet bodies, and consequently have their Trina Dimen­sio, and variety of configurations; some spherical, some cubical, some triangular; be these never so little, yet it is impossible they can exactly touch one another in all parts of their Su­perficies; a spherical body cannot be in all its Superficies contiguous to ano­ther spherical or cubical body; and consequently there must be some real, though small Intervals between these minute Particles, and then the Carte­sians, to make good their Supposition, must have yet another matter more subtil than that which they yet call subtilissima, to fill those Chinks: Et quis custodiet ipsos Custodes?

And it is not enough to say these fissures between the minutest Parti­cles, are inconsiderable: For if they be at all, it spoiles the Supposition; but besides that, certainly he that [Page 74] holds this Supposition, must yet ad­mit that in the Cubique Foot of Air, the Interstitia must needs be greater than in Water or Mercury of the like Moles; for certainly otherwise the weight of Mercury, Water and Air, would be all one; and so they fall in with the Vacuists.

Therefore upon the whole Matter, it seems more agreeable both to Na­ture, Sense and Reason, that in the first production of bodies homogeneal, whether by Creation by Almighty God, or by Generation, according to his instituted Law of Nature, the consistency of things, and their se­veral textures, to be the immediate effect of their first production, and that they consist of parts in union, and not separated till actual separa­tion, and that these parts are of the like consistence and texture with the whole in bodies homogeneal, as in Air and in Water, and not of parts or principles quite of another consi­stence and frame from the whole; all the parts of the Air to be Air; but [Page 75] yet some Air or Airs at some times more subtil than others; and so for Water: And therefore all this Appa­ratus of Atoms, and Globuli, and mi­nute particles, are not of things that ever really existed, but only the crea­tures and fictions of the Brain.

But if we should admit of any one common material principle of physi­cal bodies, it is most consonant both to the Doctrine of the Scriptures, and to some of the ancient Philosophers, that it should be Water.

1. Thus it is declared in that admi­rable Narrative of the Creation, the first distinct body we find mentioned, is the Water.

2. This was the opinion of the Learned Thales, Milesius, and others of the Ancients, Ex Aqua omnia.

3. The accommodation of Water to the production of other bodies by the transmutation of its texture, speaks much for it to be the common principle of material bodies.

1. It is productive of Consistences rarer and more subtil than it self, as [Page 76] Vapours, Fumes; yea and of the ve­ry Air it self, by the means of acti­vity of Heat.

2. It is productive of things more crass and solid than it self, as Leaves, Fruit, Wood, Shells, Stones, which we see arise from certain concretions singly of water.

3. It is productive of consistences that have greater tenaciousness and connexion than it self; as we see in the production of the Nerves, Tu­nicles, Tendons, Muscles of Animals, which are at first but certain wate­rish concrements, digested by the A­nimal heat into those Ligaments, and in the tough and strong barks and fi­laments of Vegetables, in their trunks, rinds, &c. which are at first but a kind of limpid juice or water sucked up into the bodies of Vegetables; and that even where it hath no o­ther visible nutriment but simple Wa­ter.

4. In the dissolution of bodies, ei­ther artificially or naturally, they seem most readily to reassume a wa­terish [Page 77] Consistence: Water therefore seems more accommodate to be the common material principle, much rather than these imaginable Atoms, though I take not upon me positive­ly to determine it.

CHAP. VIII. Further Considerations concerning the deficiency of this second So­lution in relation to Rarefaction and Condensation, and the Supplements that have been de­vised to enforce or supply it.

IN the last Chapter I have consi­dered the improbability of the Supposition in general.

I shall now set down those Rea­sons and Evidences which render the whole Supposition utterly inapplica­ble to the Phaenomena of Rarefaction and Condensation.

[Page 78]1. As to Rarefaction, the intromis­sion of these foreign particles of Mat­ter, to supply the supposed separa­tion of the particles of the Air, or other body rarefied, it is not possibly consistent with that motion which rarefied bodies have in the time of their rarefaction, which is most ap­parently expulsive of any foreign Matter, and not receptive of it.

Take a Corn of Gunpowder, and give it fire, it turns in a moment to a body of flame above 1000 times larger than it self; it drives away the conterminous Air from it; and if it be a good quantity of Powder, it will break the Windows. Walls and Contignations next to it, and this done in a moment, and in the mo­ment of its expansion: Is it imagi­nable to any man that thinks twice, that in that moment of its expansion, when it drives all before it and from it, this Subtilissima Materia, which is so subtil and delicate, should have ad­mission, and admission in that mo­ment, to make good an expansion of [Page 79] such an extent, nature and quality?

Again, When Air in a Vessel, is brought near the fire, and warmed by this Heat, the Air is expanded, and a great part of it driven out of the Vessel; and if the Vessel be close, it will break, from the dilatation within; so that in all this rarefaction, the Air, and all the particles of it, and within it, have a pressure out­ward, not any motion of receptive­ness of any thing from without, and therefore must necessarily drive away those gentle particles of Materia sub­tilissima, and can never admit them in the act of rarefaction done by Heat.

2. It is a very hard supposal that the subtil Matter should pass through the most impervious bodies, as Glass, Brass, yea Gold it self, for the supply­ing of the Interstitia of tense or rare­fied bodies, as it must according to this Supposition. But,

3. It is not only difficult to believe it, but the contrary thereof is most apparently evident to the very Sense, especially in the Magdeburg Hemi­spheres, [Page 80] described, cap. 18. Nugarum: If you take the two Brass Hemi­spheres there described, and by heat rarefie the Air in them, then clap them together in the manner there described, when the included heat is spent, they will cohere so strong to­gether, that 30 l. weight will not se­ver them, but let them receive a mo­derate heat again from the fire, or let there be a hole no bigger than the point of a Needle to let in any fo­reign Air, they will be quickly se­vered; for the tension which the in­cluded particles of Air do gain by their motion of restitution, and Motus nexus, is thereby relaxed: And it is observable, that these Hemispheres, if they are kept from heat or perfora­tion, they will remain in this po­sture of cohesion an hour, nay possi­bly a day, or week, or more: Now if this subtil matter, which must be the means of Rarefaction, or extension, according to the Cartesian Supposition, pervades the Vessel so easily, how comes it to pass that it is kept in [Page 81] this straight prison without avolation through the Brass Hemispheres? Or rather, why doth not a greater quan­tity thereof pervade the Brass Hemi­sphere all this while, and release the Air from its hard tension, by separa­ting thereby the Hemispheres, and so restoring the Air in all parts to its just and natural texture and position? And certainly if the Spirit of Nature or Hylarchical Principle had any thing to do in matters of this Nature, or were effective in it, here were a pro­per business and exercise for it; But we see that without perforation or ac­cession of Heat, nothing of such re­laxation is effected, notwitstanding the great stress that the Air is under in the Hemispheres, and which yet would be inevitably relaxed, if a con­siderable portion of subtil Matter did penetrate through the Hemispheres, and mix it self with the included rarefied Air, as well as if a little Air were let into it through a Pin-hole.

4. In the Instance last given, and many other of like nature, that might [Page 82] be given, where the filaments of the Air in their relaxation from heat, have a motion of contraction in them­selves per viam restitutionis, and a consequential attraction on the Vessel including them per modum nexus, it is impossible this can be salved by the Supposition of the Cartesians and Lucretians, which suppose the Air to consist of minute particles only joyned together by contiguity, for where there is only contiguity without con­tinuity of parts, that body can ne­ver draw another body per modum tra­ctionis, it will be really less tenacious than a Rope of Sand; so that such an intromission of particles thus solute, as they state most bodies to be, by a bare contiguity of Atoms, could ne­ver explicate this visible Phaenome­non that ensues upon tension of the Air, or after the avolation or extin­guishment of Heat that first expan­ded it.

5. And as this Supposition by no means salves the Phaenomena of Rare­faction of the Air, and what ensues [Page 83] thereupon, so it as little salves that of Condensation or Constipation of Air by compression, as we see in Wind-Guns, and other Engines, which upon a Discharge, or a Motion of that compression, do with a force ex­plode or discharge themselves, and press very hard upon bodies that are in their way; so that a Wind-Gun will drive a Bullet through a pretty thick piece of Wood, which could never be, if this Solution of Rarefaction and Condensation were true.

1. If the Air it self, and also this subsidiary Materia subtilissima were but a collection of minute bodies, joyned only in contiguity one to ano­ther, all the compression in the world would give it no more elasticity, or that explosive motion, than if a por­tion of Calice-Sand were forced into a Gun or other Vessel, with all the compression imaginable.

2. But again, in that elastical ex­plosion by the Air compressed into a narrower room, what is it that actu­ally exerciseth that explosive Elasti­city? [Page 84] Is it the subtil matter that was mingled with the included com­pressed Air? Surely no; for according to this Supposition, that is squeezed out and permeated through the Bar­rel or Trunk of the Wind-gun: Or is it the grosser Particles of the Air that is yet left in the Gun, and can­not get out till the Obturaculum be removed? But there is no reason for that to have any Elasticity; for by the avolation of the subtil Matter, there is room enough left for it; and under that narrow dimension that now it hath, yet hath it as much room as before; for the avolation of the Materia subtilis hath made a per­fect room for it, and left it a space exactly commensurate to its corporeal Moles. But it may be that the Mate­ria subtilis that was driven out by the compression, now upon the aperture of the Obturaculum, pervades the sub­stance of the Gun with that force that it gives the explosion. But it is apparent that neither this can help it; for it doth appear that the Mo­tion [Page 85] of the Subtil Matter into the Orifice of the Wind-gun upon the re­moval of the Obturaculum must needs run counter to the explosion of the Air, and obstruct it. Again, it is apparent that the subtil Matter is dri­ven out gradually and with iterated force, and it cannot pervade the Iron sides of the Gun, but gradually, and with great straining, and to imagine that in a moment, the moment of a Motion of the Obturaculum, the whole body of that removed Matter should pervade the strong and close Metal in an instant to give that strong and for­cible explosion, exceeds all reason, sense and credibility. And therefore it was but necessary for those that will maintain this Assertion to substi­tute a Spirit of Nature, or an Hylar­chical Principle, which for the preser­vation of Bodies in their due natural state and position, should act little less than miraculously to supply all these Difficulties, which yet notwith­standing must be supposed according to this Supposition to act in contradi­ction [Page 86] to it self and Nature also. For when in Rarefaction of Bodies this Spiritus Naturae sends supplies of subtil Matter to fill the Interstitia, it must necessarily rob other parts of the Air of some of that subtil Matter that pro­perly belonged to its texture and natu­ral constitution; and so when one portion of Matter is gratified, ano­ther is impoverished of what belongs to it, which seems wholly unsutable to the office which this vicarious Spi­rit of Nature (according to this new Supposition) is substituted to exer­cise.

CHAP. IX. Touching the Third Supposition of the Method of Rarefaction and Condensation according to the Ancient Philosophy, and seems to be the truest.

HAving examined the two for­mer Suppositions, and as near as I can, discovered their insufficiency, I now come to the Third, which I think to be true, viz. as to that kind of Rarefaction and Condensation (which before in the 4 ^th Chapter is stated to be the true Matter of the Question) for in Rarefaction of a Body (suppose Air) either by Heat or Tension, there is a real expansion or dilatation of the same Moles of Matter of the Air, and all its parts to a larger space, extent or dimension than it had be­fore; and in Condensation, by Cold, [Page 88] (but more evidently by compression) the same Moles of Matter, and all its parts have a narrower or less space or expansion than before.

I suppose therefore that although Rarefaction and Condensation of any Body from its natural size and di­mension belonging to it, is for the most part, if not alwayes, by the agency or efficiency of some external cause, yet under such circumstances: Rarity and Density are but natural af­fections, or rather Passions, Qualities or Modes of such Bodies arising from their very texture and make, and are as naturally belonging to them as Heat or Cold, Humidity or Driness, Smooth­ness or Roughness, or other tangible Qualities to other Bodies that are more gross and corporeal.

2. I do suppose that whatever men have talkt or wrote concerning Spatia imaginaria, without relation to any Bodies to fill it, yet as time or suc­cessive duration is a kind of Attendant upon successive Motion, so space is a kind of Entity relative to Bodies, and dependent upon them.

[Page 89]3. To make way to what I have to say herein: It seems to me no kind of repugnancy in Nature, but altoge­ther consonant thereunto, and that it is equally possible and reasonable that a Body that is much more rare than another, and having in it less of so­lid corporeity, and consequently of weight, than another, yet may as entirely fill the whole space within the compass of its external Superficies, as a body of a denser consistence, so that although Gold be 18000 times bulk for bulk heavier than Air, and near 20 times heavier than Wa­ter; and although Water be near 14 times lighter than Mercury, yet it is no way repugnant, but highly con­sonant to Nature, that all the parti­cles of a Tube of Air may be as close­ly united one to another, and as en­tirely fill that Cubical space, as the like Cubical body of Water or Mercury, or Gold: And that although it is inherent in the very nature of a rare body, not to have so firm a con­sistency as that which is more crass [Page 90] and solid; yet such a rare body may be wholly destitute of Pores or Inter­stitia between its parts, as the most solid body imaginable; for porosity or distance of parts is not an effect necessarily resulting from Rarity. For it would be a strange position, that no Body that were not summè solidum or crassum, could have been created, that had all its parts commensurate to all the space within the external di­mensions, or extima Superficies of such body, and yet this must necessarily follow, if such a commensuration ex natura rei, were contradictory to, and inconsistent with any body that is not summè solidum or crassum, whereof pos­sibly there is no instance that is or can be made; for Gold it self is not summè crassum or solidum; for one piece of Gold may be solider, and have more of crass Matter than another: which appears by the Disparity of weight between two several kinds of Gold of the same bulk.

Nay, upon a strict search it may be found de facto true, that some [Page 91] kinds of Wood or Metals that are more crass, and consequently more weighty than others, may yet be more porous than some Woods or Metals that are lighter and of a grea­ter tenuity; yea, Glass or Crystal, that is lighter and less crass than some o­ther bodies, may be less porous than such as are heavier and crasser; or if comparison be made between it and common Iron-Ore, the like between Calice-Sand and yellow Wax, and many more, whereof the Table of the Lord Verulam, in his Historia Densi & Rari, may yield us many In­stances.

Again, we have no better measure of the Rarity or Density in Bodies than their difference of weight, Quod Rarum, leve; quod Densum, grave. Let us resume the Instance given su­pra, cap. 6. Wherein it appears that Air is at least 12000 times lighter; and consequently rarer than Mercury: Now if we should suppose the Air in a Cubique Vessel of a Foot square, should fill but 1/12000 of that space, [Page 92] and the rest, viz. 11999 parts of that space must be either totally empty, or supplied with another kind of He­terogeneous subtil Matter, differing from Air: This must be the conse­quence of the Supposition that the Moles aeris is not commensurate to all the spaces within the Cavity of that Cube, and yet it is so evident­ly against Sense, that it is not possi­ble to be admitted, or almost con­ceivable by any that duly thinks of it.

Water is subtiler than Mercury, by 14 times; Air is subtiler than Wa­ter by 900 times; and possibly the Aether above the Atmosphere, or the Elementa Stellarum is as much subti­ler than common Air of our lower Atmosphere. It were a wild conceit to think that every given portion of the Ethereal world must necessarily have forty thousand equal portions, either of Vacuity, or of subtil Mat­ter, more refined than Aether, and that no one given portion of Ethereal Matter; suppose a Cubique Foot could [Page 93] be exactly commensurate to all the space within that Cubique Foot, but must have forty thousand intersper­sed pores, either wholly vacant, or filled with another more subtil Mat­ter than it self.

I conclude therefore, it is equally consonant to the nature of Bodies, that a more rare or subtil Body may be, and is equally commensurate to all the spaces within the extent of its Ubication, as the crassest body in the World.

The thing I drive at is this real Truth, viz. that a Body though ne­ver so rare, may be entirely com­mensurate to all the space within the compass of its external Superficies, as well as the densest or crassest Body that is or can be in Nature; and consequently that the same Body, if it have at several times several tex­tures, may in these several seasons entirely possess spaces answering such textures; as, if Water gain the tex­ture of Air, it may be commensurate to all spaces within its Superficies.

[Page 94]4. It seems to me, that although some particles of Air included in the common Body of the Air, may pos­sibly be more subtil than others, yet as to point of extension or contra­ction, all the parts thereof, even the minutest parts thereof, as to the qua­lity of Rarity and Tenuity, and the motion of Rarefaction and Condensation, are of the same nature, and perfectly homogeneal; and the like for Water; and although some imaginable parts thereof may be rarer, others crasser, yet they are perfectly mingled toge­ther, as common Constituents of the same Body we call Air; and there­fore to suppose the first Constituent minute particles of Air or Water, are hard, or of any other nature than the whole Body, is a precarious, in­evident and unreasonable Supposition.

5. I do suppose it as a certain, evident truth, that the actual exi­stence of parts or particles of conti­nued Bodies (as most evidently Wa­ter and Air are) are but only poten­tially, or by the operations of the [Page 95] Understanding in such Bodies, and not really existing, as parts, or as di­vided, till a real and actual separation of them with integral parts, though they may be bigger or less, according to the method of their separation; yet,

1. Still remain Bodies.

2. Cannot be indivisible, no not phy­sically.

3. Are of the very same nature, texture or make with the whole Bo­dy out of which they are cancelled; and therefore when the external Su­perficies of the whole bulk in Rare­faction is expanded, or in Condensation is contracted, the like expansion and contraction happens in proportion in every particle thereof, in a true and proper Rarefaction or Condensation, whereof the Question is stated.

6. I do not think that corporeity or bodily consistence is the same thing with quantity or trina dimensio; but that this is but an affection or conse­quence of it; for otherwise all Bodies that have an equal trina dimensio, [Page 96] must needs have the same Density, or an equal mass of Matter, or Cor­poreal Moles, which is contrary to Experience; for a Cubique Foot of Water hath less of Matter than a Cu­bique Foot of Mercury, as appears by the disparity of their weight, the best indication of the disparity of the Moles of Matter.

These things being thus premised, I now proceed to declare my thoughts touching Rarefaction and Condensation, holding my self singly to it as it is stated, to be the Question in the 4 ^th Chapter, and principally applying my self to those Bodies that are most Pneumatical or Spirital (I say not Spi­ritual.)

It seems therefore to me, that as several Bodies of the same external extent or Superficies; as, suppose a Cubical Foot of Air, Water, Mercury, or Gold, may have, and have yet a close continuity of all their particles without any Interstitia of vacuous spaces, or of other Matter, to fill them up, and all this arising from the [Page 97] various textures of those bodies, so the same body by a various texture acquired by accidental emergencies either of heat, tension or compressi­on, may acquire a greater or less ex­pansion, according to those varieties of acquired textures, yet without any new accession of substance, or deper­dition of any its included particles, but still remaining individually the very same Matter.

For if several bodies of various tex­tures, may be some more rare, and some more dense, from their very Make and texture, and yet as well those that are more rare, as suppose Air or Water may as exactly fill all the spaces within the compass of their extension, without the subsidiary help of vacuities or other interspersed bo­dies, as well as those of a more con­dense consistency; suppose Gold, Lead: or Mercury; the very same reason doth enforce that the same body, if its texture be either by force or accident, altered to a greater Rarity or Densi­ty than it had before, may alter its [Page 98] space, and yet be entirely and exactly commensurate to a greater or lesser space, according to such alteration of its texture, as well as those several bodies that had primitively the like variety of texture constant to their nature.

For Matter or material substance is of it self equally susceptive of a laxer or crasser, a rarer or denser consistence or texture of parts; only when it is lax or rare, the same portion of Mat­ter takes up more space, when it is crass or dense, it takes up less space.

For instance, in Distillation we will suppose that first by some mode­rate Heat the distillatory Vessels, the Vessel (wherein the Roses for the pur­pose are placed to be distilled) the Head of the Still, and the Recipient to be as much evacuated of Air, or the included Air attenuated as much as may be, and then the Vessels close­ly luted one to another, the moist Matter of the Roses by gentle heat is resolved first into a subtil Fume or [Page 99] Vapour, and so rarefied from what it was in the Rose-Leaves: Then again these Fumes or Vapors partly by the coldness of the Head of the Still, partly by the collection and ag­gregation of the Vapors themselves, resolve into drops of water, and so discharge themselves into the Recei­vers: Here the very same body by the change of its texture, namely, the watry or moist substance of the Roses is first dilated into Fumes or Vapors, and then contracted into Water; and the first receive a dilata­tion or expansion into Vapors, where it takes up a larger dimension in all its parts, as well as in its ambient Su­perficies, and then a contraction into a narrower compass, when resolved in­to Water, and yet continues still the same body; but by variation of its textures, assumes a larger or narrow­er dimension in all its parts without reception of new foreign particles to dilate it, or emission of some of its substance in contraction or condensa­tion.

[Page 100]Which Instance explains what I in­tend; namely, that the same indivi­dual body, according to the variety of its textures, may acquire a larger or less space, and yet continue the same body, though altered in the tex­tures of Rarity or Density; as Air hath a larger expansion than Water, so if Water be converted into Air, and thereby its texture altered into a more subtil expansive body, it takes up the same dimension as if it had been never Water, but alwayes Air. And if Air again be converted into Water, it takes up the same contra­cted dimension, as if it had ever been Water.

And this method of solution of Condensation and Rarefaction, answers all the evident, apparent and sensible Phaenomena in Rarefaction and Conden­sation above delivered, and that with­out any difficulty or strained supposi­tion: For instance, In Rarefaction by Heat, or by tension of a Cubical Foot of Air in a Vessel, it is visible that the Air, and every particle of it, [Page 101] gains a larger extent every way; for it will break the Vessel, unless it have vent, which it could not do, unless the entire body were extended, and not barely the Superficies, because unless the whole Moles were every way expanded, it would have room enough within it self for its reception without breaking the Vessel that con­tains it.

Again, when the Heat decays, and consequently the Air relaxed from that extent, it endeavours its own contraction to its just and natural size and texture which it lost for the time, by the foreign violence of expansion by Heat or Tension, and this by a natural motion of restitution to its natural texture; and because it can­not gain its relaxation to its former texture by contraction, by reason of the vacuity that would thereupon follow, it doth as much as it may, and lays hold on the internal sides of the Vessels wherein it is imprisoned, and pulls them together; but as soon as it gains a relaxation by the admis­sion [Page 102] of foreign Air into it, the very same portion of expanded Air that under its expansion filled a Cube of a Foot square, will subside into a space of less than six inches square, which was its true natural space resulting from the texture it then had, by that admission of foreign Air.

Again, in Condensation a portion of Air, suppose a Cubique Foot in its just and natural texture, entirely fills all the space within that Cubical Foot (for its texture is suited to such a space) but being compressed forcibly into a Wind-gun or Aeolipile, the texture is changed by this violence, and it takes up perchance not the twentieth part of that space: The difference of its extension ariseth from the alteration of its texture by this external compres­sive force used upon it; and hereup­on it gains an Elasticity, which is no­thing else but a natural motion or co­natus to be restored to its former just and natural texture, and consequent­ly to that just extent, and Liberty, and position of space that belongs natu­rally [Page 103] to it, as a Stick, or Branch of a Tree, or Spring of Steel being bent beyond, or against its just position, hath its motion of restitution to its for­mer position, with a force or resili­tion: For the Air in its natural con­stitution, hath a certain determinate texture belonging to it, and conse­quently a just and natural extension proportionate to that texture. And this it greedily endeavours to keep; and when disturbed from it, to re-ac­quire, which is the motion of restitu­tion which I often express by the natu­ral and spontaneous contraction of a Lute-string, after an extention beyond its proper texture. And this is the ge­nuine and true cause of that strong and violent explosion that happens in those Pneumatical Engins of various sorts.

So that in these and all other Phae­nomena of Rarefaction and Condensation, this plain, and common, and ancient Solution squares exactly with them, as might be instanced in infinite more Particulars, if it were needful.

[Page 102]And with this agree the best Phi­losophers both Ancient and Mo­dern.

Aristotle, that great Priest of Na­ture, in 4 Physicor. cap. 9. wherein he answers the Objections brought by others to prove Vacuities from the Phaenomena in Rarefaction and Conden­sation, tells us that Rarity and Density properly so called, are not by acces­sion of new Matter, or loss of any of the old, but from the potentiality of Matter it self, to undergo several textures, and consequently several ex­tensions, Si factus est Aer ex Aqua, eadem materia facta est Aer, nulla re insuper alia assumpta sed quod erat po­tentia, id tandem facta est actu; & si­mili modo si orta est Aqua ex Aere, ea­dem namque materia nunc in magnam ex parva, nunc in parvam ex magna verti­tur molem, &c. Qua re ipsa Moles sen­sibilis non ideo extenditur aut constringi­tur quia materiae aliquid insuper adjicit aut objicit, sed quia ipsa Materies utrum­que subire potest, quo sit ut idem sit ra­rum & densum, & utriusque Materia una, [Page 105] atqui densum est grave, rarum autem leve.

Again, the Lord Verulam, a great inquisitor into Nature, and not very friendly to Aristotle in his Historia Densi & Rari, after several Instances of Pseudo-rarefactions, when he speaks of Rarefaction of Air by Heat, pag. 43. tells us, Aer per calorem dilatatur sim­pliciter, neque enim separatur quippiam, aut emittitur, ut in tangibilibus, sed simpliciter fit expansio.

This Rarefaction is not therefore by the distraction of the particles of Air one from another to a greater di­stance, and interposing porosities or interstitia either of perfect empty spaces as the Vacuists would have it, or filled with adventitious subtil Matter, as the Cartesians would have it; neither in Condensation are any parts of Air, or included in Air drawn out, and there­by the remaining particles rendred into a closer order and contiguity one to another:

But in the former the extension of the whole portion of Air, and of [Page 106] every particle is thereof quaquaversum enlarged, and in Condensation the en­tire extension of the Air and every part thereof is quaquaversum contra­cted, and this variation is no other but a common affection, or rather position or quantity of Matter neces­sarily arising from the various tex­tures that it successively acquires.

And therefore the great Objections that are made against this Method of the Ancients in their accounts of Ra­refaction and Condensation, fall to just nothing; as for instance,

1. That in Rarefaction of the Air, it must be softer to the touch, and in Condensation harder: I would gladly hear of that man that ever knew de fa­cto Air condensed but to its 100 ^th part yet if it were condensed 900 times, it would not be so dense as Water, or what disproportion to the touch he can find between Smoke and Air, and yet the former is far more dense; for it is conspicuous to the view: so that he had need be a man of exquisite sense, to make any conclusion from his [Page 107] touch, touching the Rarity and Den­sity of a Pneumatical Body.

Again, if the Atomical Hypothesis were admitted, it is not conceptible but that all bodies, whether in their natural texture, or under the motions of Rarefaction and Condensation, must be hard and equally hard, because consisting of a plenitude of Atoms, which are all supposed to be hard and infrangible.

CHAP. X. A farther Consideration of Rarefa­ction and Condensation, and of the Supposition of the pene­trability or impenetrability of Bo­dies, Material Substances, Quan­tity, Extension, &c.

THe principal Objection against the method of Rarefaction and Condensation, propounded in the for­mer Chapter, is this, That it is im­possible the same Moles of Matter can assume a larger space and dimension, as in Rarefaction, without a division of one part from another, and there­by leaving certain vacant Interstitia between the parts separated, or with­out a supposition of a pre-existent pe­netration of the parts of Matter, while in its former more condensed consi­stence, [Page 109] and in Rarefaction thrusting out those parts that formerly penetra­ted one another, being unfettered in Rarefaction, or by admission of new porosities made in the rarefied Matter, and reception therein of other foreign Matter. Again, Condensation of the same portion of Matter cannot be without supposition of vacant empty Spatiola, which are closed up by the strict coalition of parts, or by suppo­sing a penetrability and penetration of the parts of the same portion of Matter in its new acquired state of Condensation, or by driving out from that portion of Matter some of its more subtil parts, whereby the re­maining parts are fewer, and take up less room or space than before such Condensation: The first is the first way propounded by the Vacuists, and is re­jected. The second is in effect the way propounded by me in the former Chapter, but is said to be inconsi­stent in nature, because penetrability of bodies or of extension of Material Substance, is rejected by almost all [Page 110] Philosophers; therefore the last, which is the middle way, contended against in the 8 ^th Chapter, must be the true Method of Rarefaction and Condensa­tion.

I answer, It is true, I have laid aside, and that justly, the Opinion of the Vacuists, in the 7 ^th Chapter, and likewise the Opinion of acquest of new Matter, and expulsion of part of the old, in the 8 ^th Chapter, and have entertain'd the Opinion of the An­cient and some of the Modern Philo­sophers, in the 9 ^th Chapter. And it is true that this Opinion thus by me entertained, cannot well be suppor­ted without a supposition of the pe­netrability of material Substances, or somewhat analogal thereunto, viz. Contraction and Dilatation: And it is true, that although I think that this penetrability of Material Substance, be a great truth, yet it is some dif­ficulty to explain it; which neverthe­less I shall endeavour to do; and in doing of it, the Answer to the Obje­ction will evidence it self. And I [Page 111] shall choose to do it this way, name­ly, by explication of Terms and Words, and rendring my apprehensions suta­ble to those Explications, though it may be in a different manner from the usual or Scholastick expressions.

1. Concerning Penetrability and Impenetrability.

2. Concerning Material Sub­stance.

3. Concerning Body, and where­in it differs from the Notion of Sub­stance.

4. Concerning Quantity.

5. Concerning Rarity and Den­sity.

6. Concerning Extension or Di­mension.

7. Concerning Penetrability, how it is or is not applicable to the for­mer Subjects.

First, Penetrability or Penetration of Matter or Bodies, &c. is of three sorts, viz.

1. The permeation or penetration of one Body into or through another, by porosities of the penetrated Body, [Page 112] either found or made by the penetra­ting Body; this is common almost to all Bodies, and is not the Penetrabi­lity in question.

2. The separation, distraction or division of the parts of a penetrated Body by the force and energy of ano­ther Body; as the Arrow through the Air, or the Bullet through the sides of a Ship; this is also usual, and is not the penetration or penetrability in question.

3. When one part or particle of Matter is taken into another portion of Matter by a kind of contraction, and swallowed up and drowned as it were, in another portion of Matter, by a stricter union than it had before; whereby the same numerical portion of Matter hath a less extension and space than it had before, and yet con­tinues the same portion of Matter without diminution or encrease of substance, and this is that which is the Subject of the Question in hand.

And this penetration of Matter or Bodies may be considered two ways.

[Page 113]1. When two distinct divided bo­dies or portions of Matter are said thus to penetrate each other.

2. When the united parts of the same portion of Matter do penetrate and swallow each other, as is suppo­sed to be done in Condensation; and though the former be considerable, yet this latter is that kind of penetra­tion touching which the Question grows.

Secondly, Matter or Material Sub­stance is the Substratum of Bodies; and although it is not possible for it to exist one moment without a de­terminate extent and determination into some Body compleated in Esse Corporeo, yet it is of it self indifferent to any particular extension or bodily Concrement. This is that Materia Prima, the Subject of all Generation and Corruption, yet it self ingene­rable and incorruptible; that Proteus which in various successions is ca­pable of various Forms, Extensions and Variety of Bodies; as we see in a piece of Wood thrown into the Fire, [Page 114] that same material substance which but now was Wood, assumes several Natures and Extensions, some more fixed than the Wood, as its Salts; some more lax, as Ashes and Smoke, and accordingly undergoes Varieties of Extensions different from what the very same portion of Matter had be­fore: the very same individual sup­posed portion of Matter is capable of being determined into Air, Water, or some other Body; and if deter­mined into Water, it may be the supposed portion of Matter would make up a Cubical Body of an inch square; but if determined into Air, it would make a Cubical body of a­bove 1000 times that extension, and yet the individual portion of Matter simply the same, and neither more nor less under those different textures and extensions; for Material Sub­stance is naturally susceptive succes­sively of various textures and consi­stences, from whence do necessarily result successively various extents or diminutions of that one individual [Page 115] particle of Matter under those various consistences.

Thirdly, Body is nothing else but Matter determined into a Body of this or that Nature, Figure, Tex­ture, Plexus, Quality and Dimension; these are superadditions to Matter, and being added to it, determine it into Body; and when this Body by the power of the Agent, assumes another distinct consistence; then is that Body, either essentially changed into another kind of Body, or else accidentally altered in figure, dimen­sion, texture, or otherwise, and yet the Matter continues entirely the same, as in some Bodies; the very same Cubique inch of Bees-Wax may be moulded into a Globe, a Cone, a Trigone, &c. and yet continues the same numerical and individual piece of Wax.

Fourthly, Quantity; and herein I shall take the Liberty to use this word according to my own sense, abstract­ed from others acceptation: I call therefore Quantity that Habitude [Page 116] whereby a Material Substance under any determination is denominated more or less, and is a kind of proper inseparable Accident (if we will call it so) of Material Substance, and in­trinsick to it, and really differs from Extension or Dimension: For in­stance, a Cubique inch of Water is rarefied into 1000 Cubique inches of Air; or a Cubique Foot of Air is by heat rarified into five cubique Feet of Air; here is variety of Extension, and yet the same quantity of Matter in the cubique inch of Water, and in the cubique foot of Air, as is after Rarefaction in the 1000 cubique inches of Air, and 5 cubique feet of Air, Quantity being closely knit to Mate­rial Substance, but this or that parti­cular extension variable, though the quantity ( i. e.) the Moles, the much­ness of Substance be the same.

And herein, among other things, it differs from Extension, that Ex­tension is measured by artificial mea­sures of Inches, Palms, Feet, Cubits; but Quantity, in my acceptation, is [Page 117] measured by weight, which gives the discrimination of Quantity or Much­ness of Matter, where, it may be, the extent is equal; as a cubique foot of wa­ter is equal in dimension to a cubique foot of Mercury; but there is 14 times more weight, and consequently more Matter and Material quantity in the latter than in the former.

Fifthly, Density and Rarity are va­rious Qualities both of Bodies and Material Substance; and they are e­qually susceptive of those qualities, as they are of Colour, Figure, varie­ty of Texture, or the like, namely, in successive portions of Time or Du­ration: and hence it is infallibly true that the same Material Substance that is now actually rare, is potentially dense; or that which now is actually dense, is potentially rare, without any admission of new Substance, or deperdition of any of the old. And as several portions of Material Sub­stance are susceptive of, or actually under several degrees of Rarity or Density, as Gold, Iron, Wax, Water, [Page 118] Air; so the same portion of Material Substance may in successive portions of times be susceptive of several de­grees of Rarity or Density; for, as I said, they are but several qualities, or if you will, modes of Matter.

The Motion to Rarity or Density, is that which is usually called Rarefa­ction or Condensation; and though Matter or Body be susceptive of it (some more easily, some more diffi­cultly) yet it is most ordinarily the effect of an extrinsecal Agent, as Fire, Tension, Constipation, Compres­sion.

The Method whereby the alteration from Rarity to Density, or to a less degree of Density, and e converso, is effected, is the alteration of the tex­ture of the Body so rarefied or conden­sed into a more dilate or contracted consistence.

And this Alteration is sometimes so great, that it alters the very nature or Species of the Body, as when Air is condensed into Water, or Wa­ter into Air; sometimes it only alters [Page 119] the texture, without altering the na­ture; as when Air is compressed in­to a narrower compass in Wind-guns, or dilated by heat in Aeolipiles, it re­mains Air still, though under differ­ing texture from what it had be­fore.

The effects of Rarefaction and Con­densation are neither increase nor di­minution of the Substance thus con­densed or rarefied, nor of its quanti­ty or muchness: If a cubique inch of Brass were condensed into Gold, indeed the Moles would be less in ex­tent; but there would be the very same individual portion of material substance in both; and the very same weight that the cubique inch of Brass had, would the portion of Gold have upon such a condensation: For weight and not extent is the best measure of equality or disparity of material sub­stance.

But indeed as to Extension, the measures would differ; the same Mo­les of Matter condensed might not take up half the extent it did before, [Page 120] and being rarefied, might take up ten times its extension or dimen­sion.

Sixthly, Dimension or Extension; Though as Quantity imports much or little, it be inseparable from the notion of material Substance, yet actual Ex­tension in this or that determinate measure or degree, is but purely ac­cidental to Material Substance; for it may have one extension one hour, and the next hour have another, as its texture is altered: For variety of extension is consequential, and neces­sarily consequential upon alteration of texture.

There are certain distinctions to be observed touching Extension, viz.

1. An actual, and an habitual, ap­titudinary and potential extension, al­though de facto every portion of mat­ter is under some actual extension, yet, as I said, this or that actual ex­tension is not intrinsecal or essential to Matter; for as it is capable of a variation of its texture, so it is capa­ble of a change, variation and altera­tion [Page 121] of its dimension. But that ha­bitual, aptitudinary and potential ex­tension whereby it must necessarily be at some time or moment under some determinate extension or other, is intrinsick to it, though it be suc­cessively alterable as its texture is alte­rable.

Again, 2. We must distinguish be­tween the extension in the superficial and external dimension, and that which is the whole portion of Mat­ter; the former may be without the true and real encrease of extent or di­mension; for possibly by the distracti­on and separation of the more inte­rior parts of Matter, and the produ­ction thereby of porosities, the exter­nal superficial extent may be enlar­ged, and yet the whole extent con­tinues the same, but only with a di­versified ubication of the more interior parts of Matter; but that exten­sion which is intended by me in Rare­faction, is an entire extension of the whole Matter and all its parts, with­out which there is no true and ad­equate [Page 122] extension; and that contracti­on or penetration of Material Sub­stance to Condensation, is the con­traction of the whole triple dimension, length, breadth and thickness of the whole Body and every part, yet re­taining the same quantity or much­ness of Substance.

And as I have shewed that in se­veral portions of Material Substance, it is not only consistent with the Laws of Nature, but evidently true in fact that a portion of rarefied Matter (sup­pose it Air) may be, and is co-exten­ded to all the spaces within the com­pass of that Matter, and fills them as entirely as a most dense Body or por­tion of Matter fills all the spaces with­in its superficial dimension (as sup­pose it Water, or even Mercury or Gold it self) so the same portion of compacted Matter, suppose it Water or Mercury, being rarefied into a more dilated and expanded consistence, as into Air or Fumes, may upon the very same account fill all the spaces within the extent of that dilated ex­tension, [Page 123] without any hiatus or inter­stitia of empty spaces, or the acquest of any additional Matter, because the texture of that portion of Matter is only changed, and a greater extension or dimension is necessarily consequen­tial upon, or concomitant with the variation of the texture of that very same portion of Matter to a greater expansion in Rarefaction.

Seventhly, The Contraction or E­volution and Expansion of a Spirit or Spiritual Substance, which is com­monly called Penetration, is incident to Spirits and Spiritual Substances, that are void of Matter; but this doth not at all impeach that natural pe­netration of Material Substance where­of I have spoken; for they differ toto coelo one from another.

1. In the principle of each Pe­netration: In Material Substance it always, or at least, common­ly, proceeds from an external effici­ent or force, as in Contraction or Penetration of Material Substances by compression, or by constipations from [Page 124] without; but the penetration or con­traction, or dilatation of a Spiritual Substance, is from an internal prin­ciple, possibly the determination of the will of such a Spirit to contraction or evolution.

2. In the Consequent, or rather Concomitant of such Penetration or Expansion: In Material Substance, upon contraction or penetration, the Matter is necessarily thereupon more dense; and in evolution or expansion, more rare; for it can­not be one or other without the ac­quest of a new texture of its parts, viz. more lax in Rarefaction, more close and compact in Condensation; but in the contraction or evolution of a Spirit, there is no alteration in the texture, or Rarity or Density of a spi­ritual substance: For Rarity and Den­sity are Qualities and Affections com­petible only to Bodies and Material Substances, not to Spirits or Sub­stances purely immaterial; therefore I do dismiss the Penetrability of Spi­rits, as a thing wholly unapplicable [Page 125] to the Matter in Question, and no way applicable to the Argument in hand.

Eighthly, Now to apply the business of Penetrability or Impenetrability to what hath been formerly delive­red.

First, In case of several Bodies that are under several actual dimensions, and not united one to another by con­tinuation, this concerns not the pre­sent Question, which is touching one common portion of Matter, whose parts are united one to another, and so in a state of union: yet whether that a Body may not be of so high a recti­fied purity and tenuity, that it may penetrate the dimensions of a gros­ser Body without porosities for its transition, either found or made in that penetrated Body, may be diffi­cult to determine, because we are unacquainted with the highest de­grees of subtilty of Bodies, and con­sequently of those Energies that are consequential thereupon: Only if Light be a Body, or if the Magneti­cal effusion be corporeal effluxes as [Page 226] some of the late Philosophers assert, it seems to favour such a penetrabili­ty of such subtil Bodies; for Light will pervade every part of the Dia­phanum, and Magnetical Effluxes will pervade the solidest Bodies, even Gold it self, as Experience shews us, with­out making porosities for its transition. But I dismiss this as not to the Que­stion in hand; and possibly the Sup­position that Light or Magnetical Ef­fluxes are Bodies, is untrue.

Secondly, As to portions of Matter, Bodies and Extensions thereof, where its parts are united in one common continuity, as in the case of proper Rarefaction and Condensation, it seems that such a penetration of actual di­mensions, or of Bodies determined in or under actual dimensions, such a penetration either of Bodies or actual dimensions, or extensions, is impos­sible and contradictory in it self, so long as such actual dimensions con­tinue unaltered by an alteration of the texture of such Body, and consequen­tially of such actual dimensions; for [Page 127] a cubique Body of 12 inches cannot be more or less in extension than it is, so long as it is a cubique Body of 12 inches: This is that penetration of Bodies and Dimensions that we do reject under that name.

Thirdly, But in as much as the ve­ry same portion of Material Substance is successively capable of several tex­tures, and consequently of several di­mensions, there is nothing in Nature or Reason that prohibits a successive penetration of Material Substances under such a mutation of textures and actual dimensions, so that one and the very same numerical portion of Matter that this moment is under a texture accommodate to the nature of the most subtil Air, being con­densed into a degree of Air less sub­til, or condensed into Water, its parts will be constipated and contra­cted into a closer posture, and take up less space according to the degree of its Condensation; which contra­ction or constipation of its parts, may not improperly be called penetration [Page 128] of material Substance, but is not pro­perly a penetration of Bodies, or ex­tension actually determined, and re­maining unaltered in its texture.

And this gives the difference be­tween 1. Penetration of actual Di­mensions; and, 2. Penetration of Bo­dies. 3. Penetration of Material Sub­stance. The two former are impos­sible without an alteration of the di­mension or texture of the Body. The third is not only possible but neces­sary, and necessarily consequential upon the alteration of the texture of the Body into a more rare or dense consistency.

And the evidence of the Truth hereof is, because the same numerical portion of Substance material in a state of Rarity, is as commensurate to all the particles of Space within the compass of its external Superficies, and hath as perfect and undivided continuation of its parts one to ano­ther; as when it is condensed into a consistence that bears not the 100 ^th part or 1000 ^th part of the same super­ficial [Page 129] dimension; for otherwise it were not possible to conceive, but that in the whole Body of Air and Aether, for one portion of Material Substance, there must be 1000 portions of em­pty spaces or nothings, which is against Nature.

And this Sentiment, though not warily enough examined and consi­dered by some Philosophical Heads, hath made them run on with one common cry against all penetration of Material Substances, under the name of penetration of Bodies and Extensions, as a great absurdity: But of latter times, some more conside­rate and inquisitive persons have sear­ched more freely and impartially in­to this business; and though they do reject that impossible and contradi­ctory penetration of Bodies and actual Extensions or Dimension remaining unaltered in the sense before given; yet do not only allow, as possible; but also assert, as natural and neces­sary penetration of the parts of the same individual portion of Material [Page 130] Substance, consisting in a State of uni­on, and under an alteration of tex­tures, and consequently a change of extensions, as any man may see in the Learned Treatise of Bodies, of Sir K. Digby, pag. The large Dispute of Guarinus, Guarini Disputatione 4to Ex­pensione, 2. De Rarefactione & Conden­satione. And our Learned Countrey­man, Dr. Glisson, in his Tractate De Natura Substantiae Energetica, cap. 27, 28. Wherein, among other clear Explications of this Matter of Pene­trability of Material Substances, he hath these Passages, namely, the pre­judice that men have taken up against penetrability of Matter, is, Quod ab incunte aetate consuevimus cogitare & dicere non dari penetrationem Corporum aut dimensionum quodque simul pro conces­so habuimus penetrationem Corporum & Substantiarum idem sonare. Again, Impossibile est, ut manente eadem Ex­tensione, mutetur Densitas, aut ut hac mutata, illa non mutetur; mutata di­mensione, ut in Condensatione, Mate­ria partes aliquas sui quasi absorbet in [Page 131] seipsam. And again, Sola terminata extensio est quae materiam durante eadem terminatione, & non diutius impenetra­bilem pr [...]stat.

Neither is this any Novel Doctrine, but the very Natural Sense of Ari­stotle in 4 to Physicorum, cap. 9. before cited, and those expressions of the potentiality of the very same portion of Matter to become rare or dense, and thereby the Extension altered, without any diminution of its Matter in Condensation, or acquisition of new Matter, in Rarefaction; though it mention not Penetrability in ex­press words, yet asserts the thing, as it is above declared.

Upon the whole Matter therefore it seems, 1. There is no necessity of a Sup­position of a penetration of Dimensions on Condensation; neither is it indeed possible where the Dimensions conti­nue the same, but would be a kind of contradiction. And,

2. Consequently where the Dimen­sions continue the same without alte­ration, it is impossible there should be [Page 132] a penetration of Bodies or Material Substances, remaining under the same actual dimension unaltered.

3. But there is not only a possibili­ty of the change of Extension, but the same will necessarily follow upon the change of the texture of the Body or Matter under such Extension: And,

4. Consequently the Extension there remaines not the same, but is chan­ged. And,

5. Under such a change of Dimen­sion or Extension, or together with it, there may be, and will follow that which is called a penetration of Mat­ter or Material Substance; for that which was the impediment thereof, namely, the actual Extension or Di­mension is not only changeable, but now changed. And,

6. Therefore it seems no absurdity in Nature or Reason, to suppose such a penetration of Material Substances, in the case of Condensation, and is the most reasonable Solution of it.

And thus I have given an Accompt of what seems probable to me touch­ing [Page 133] this dark and intricate Enquiry touching Rarefaction and Condensa­tion; and therefore I have been the longer in it, because I would be un­derstood, and because in the ensuing Remarks it is often urged against the Solution offered of the Phaenomena of the Torricellian Experiment; and I shall remit the Answer of the Remarks of that kind to this Preliminary Dis­course; which, though possibly it may not satisfie every Reader, yet it will at least render it evident, that the Objections made upon these ob­scure and intricate Suppositions of im­penetrability of Material Substance, are not so effectual, nor indeed proper to evince or prove, unless we had a clearer Discovery of the Nature and Affections of Bodies, than we have yet attained. And therefore Objecti­ons made from this Topique, lose their use, in as much as the Medium is more obscure than the very thing con­tended about. And now I shall pro­ceed to the Remarks themselves.