OBSERVATIONS Touching the PRINCIPLES OF NATURAL MOTIONS; And especially touching Rarefaction & Condensation: TOGETHER WITH A REPLY to certain REMARKS touching the Gravitation of FLUIDS.

By the Author of DIFFICILES NƲGAE.

LONDON, Printed by W. Godbid, for W. Shrowsbury, at the Bible in Duke-Lane, 1677.

The Right Hon.ble Algernon Capell, Earl of Essex, Viscount Maldon, and Baron Capell of Hadham: 1701.



ABout Two or Three Years since, I was content that Two Small Books, or rather Pamphlets, that I had collected, partly in my Youth, and partly at the Recreations of leisure hours, should be published in Print; The one Entituled, An Essay touching the Gravitation of Fluids; The other, Difficiles Nugae, or, Observations touching the Torri­cellian Experiment.

In the Publishing of them, I did not set them off with any Ostentation; but let them go with uninviting Titles, and not so much as bestowed upon them my [Page] Name: For I thought that they were but Trifles, and such as were below the Perusal of the Learned men of the Age, and at best, a Divertisement of some leisure-hours, to young Students in Mat­ters of this Nature.

But beyond my expectation, these Nugae (for so I must still call them) had the unexpected honour to be perused and examined by Two especially of the most Learned Masters in Philosophy and Mathematicks, that this latter Age hath yielded; and not only so, but they have given them the honour to make Observations, Animadversions and Re­marks upon them.

Those which came out first were short and obiter, upon occasion of another Dis­course, which gave opportunity of a short Defence. Those that came out since, were more large.

The Nameless Author of the Essay and Nugae, doth return to them his thankful Acknowledgment of thoir Favour, in ta­king Notice of such Trifles, and using them and the unknown Author with that Civility that they have expressed in their Remarks.

[Page]The truth is. the Controversie falls to be of that Nature, that among the Three Contenders, every one opposeth somewhat that the other two grant; and asserts somewhat that the other two deny: For instance, I contend against the solving of the Phaenomena in the Torricellian Experiment, by the weight or Elasticity of the Air, or by a common Spirit of Na­ture; but that it is done Mechanically by Tension.

My first Opponent supposeth it not done by Tension, nor the common Spirit of Nature, but by the Weight and Elasticity of the Air.

The Third contends that it is neither done by the Elasticity or weight of the Air, nor by Tension; but by the Spirit of Na­ture.

Thus every one agrees and disagrees with the other; and every Opponent in one kind, is in another kind the Advocate of the Party he opposeth.

And this will both assist and justifie me, in writing in the farther Explication and Application of what I have asserted; which I shall do with plainness and free­ness: [Page] but without Arrogance to my self, as if I had wholly confuted my Opponents; or detraction from my Opponents, or their Assertions, by censuring them as absurd or contradictory. For in those cases, the Judg­ment is the Readers, not the Opponents.

In Philosophical Enquiries and Con­clusions, we may observe two kinds of Methods used by some men.

Some begin at their Senses, examine particular Matters of Facts, how they are, or fall out, search into Experi­ments and visible Trials, and those Ap­pearances of Nature that are obvious to our Senses, and from these they deduce their Conclusions and Theorems.

And certainly he that attentively reads Aristotle, especially in his History of Animals, of their Parts, Going and Ge­neration, in his Meteorologicks, in his Books De Anima; yea, in his very Phy­sicks, will find, that as he was the grea­test Master of Experience and Observa­tion of this kind, so it was the great Method of his Deductions and Conclusi­ons. And therefore they that when they would seem to cry up Experimental Phi­losophy, [Page] think they do but right in de­crying Aristotle, either have not consi­dered him, or surely are too injurious to him.

Again, There are some that lay the first Foundations of their Philosophy in Notions, and Speculations, and precon­ceived Systemes of their own framing; and then conforming the Solution of the Phaenomena in Nature, to those Noti­ons. And these most commonly do by Na­ture and Natural Appearances, as that Tyrant did by his Prisoners that were too long or too short for his Iron Bed; stretched the latter, and cut the former to its dimension; so these handle the Phaenomena in Nature; torture and torment them into a consonancy to their Notions; or at best, substitute new preca­rious Notions to piece out their Hypothe­ses, and to render sensible Appearances to hold analogy with that Notional Sy­steme of things that they have framed: And I must needs say, that I think the general Mode and Fashion of the re­assumed Philosophy of Lucretius, E­picurus and Democritus, the Restitu­tion [Page] and Reformation of it by Des Car­tes and Gassendus, hath too much of this latter Method in it, and is a very uncertain and preposterous way of forming Conclusions. I have therefore chosen the former of these Methods, and as near as I can, framed my Conclusions from the evidence of Sense and particular Ex­periences and Experiments.

And although it is not impossible for me to be mistaken in some of my Experi­ments, and the Inferences made there­upon; yet I think I have not much mi­staken herein; only one Experiment, which I call a double Trial, pag. 84. of the Dif­ficiles Nugae, is somewhat obscurely de­livered by me, and not so much to my pur­pose; of which I take notice in my Reply to the 6th Remark upon that Book.

I have in the Beginning of this Book spent Ten chapters touching the Princi­ples of Motion, Essential Forms, Ra­refaction and Condensation; which have a general influence into much of what is said concerning those matters, which often occur in the Remarks; and thereby I at once give my sense concerning [Page] those difficult points, and save my self the labour of often Repetitions or Answers touching things therein delivered.

The Subject of the Controversie, I con­fess, is of no great importance, neither is the fortune of Greece (as the Pro­verb is) concerned whether of the Con­troverters Suppositions be the truest; or whether, it may be, some other may be discovered truer than any of the former. All that I shall say touching our Dis­courses of this nature, is this, That though they are not very profitable ex­pences of time in the Writers or Readers; yet they may be innocent Diversions to both, and may be of some use in the in­dagation of Natural Causes and Ef­fects.

Some Favours I must desire of the Rea­der.

1. That he will be contented to bear with such vulgar Expressions which serve my turn to give account of my Thoughts in a Matter of this Nature; such as are, Architecture, Cones, Capes, Masonry, and twenty such vulgar Ex­pressions, [Page] which, it may be, Learned men may think too mean, and repeat them with some disdain.

2. That though I do many times use Expressions that are not polished accor­ding to Grammatical or Scholastick Niceties or Modes, that I may be ex­cused herein, and that the Reader will look to the Scope and Drift; and mark at what I aim; and not cavil at bare Terms and Expressions, so long as the thing they design be laid open: This is an unhappiness that too often befals men that are inquisitive after Truth; that their Readers or Opponents miss the scope of the Writer, and fall upon Criticismes about Words and Forms of Expressions. Words are but Signs of Conceptions and Thoughts; and as I have elsewhere said, they perform their Office well enough, when they render our Thoughts intel­ligible.

3. That he will be content to su­spend his Censure upon Clauses or Sen­tences apart, till he hath perused all: It is not possible, especially in Discourses [Page] of this Nature, to speak or write all at once. Some things that are but shortly or obscurely delivered, or per­chance omitted in one Sentence, Page, or Paragraph, may be supplied or ex­plained in another.


  • CHap. 1. Concerning Motion, and its Original. Pag. 1
  • Chap. 2. A farther Disquisition touching the immediate Cause of Motion. Pag. 7
  • Chap. 3. Concerning some other more universal or common Causes assigned to Motions, viz. Anima Mundi, Spiri­tus Naturae, & Principia Hylar­chica. Pag. 25
  • Chap. 4. Touching Rarefaction and Condensation, and their Kinds. Pag. 36
  • Chap. 5. Concerning the Phaenomena of Rarefaction and Condensation appa­rent to Sense. Pag. 49
  • Chap. 6. Concerning the various Soluti­ons of Condensation and Rarefacti­on; and first, of that which is by sup­posed interspersed Vacuities. Pag. 55
  • Chap. 7. Concerning the Second Solution [Page] of Rarefaction and Condensation, and its insufficiency. Pag. 67
  • Chap. 8. Further Considerations concer­ning the Deficiency of the Second Solu­tion in relation to Rarefaction and Condensation, and the Supplements that have been devised to enforce or supply it. Pag. 77
  • Chap. 9. Touching the Third Supposition of the Method of Rarefaction and Con­densation according to the Ancient Phi­losophy, which seems to be the truest. Pag. 87
  • Chap. 10. A further Consideration of Rarefaction and Condensation, and of the Supposition of the Penetrability or Impenetrability of Bodies, Material Substances, Quantity, Extension, &c. Pag. 108


PAg. 39. l. 4. dele appearing. p. 43. l. 10. r. it it makes spaces. p. 63. l. 25. abstracted, r. obstru­cted. p. 64. l. 18. r. and with great ease, if the suppo­sition be true. p. 65. l. 15. more, r. mere. p. 89. l. 20. Tube, r. Cube. p. 94. l. 23. dele actual. p. 95. l. 13. cancelled, r. cantelled. p. 106. l. 7. r. passion or quality of. p. 131. l. 21. r. in Condensation. p. 189. l. 6. r. pre­ponderation. p. 192. l. 25. Ballance, r. Bottom. p. 204. l. 20. some, r. sense. p. 239. l. 24. r. preponderated. p. 276. l. 17. r. foreign.

OBSERVATIONS Touching the Principles of Natural Motions; and especially touching RAREFACTION and CONDENSATION.

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 20d weight, and the like Moles of of Mercury 19d weight and 9 grains; the like Moles of Silver weighed 10d weight and 21 grains; and the like [Page 62] Moles of Water weighed 1d 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 899th 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 4th 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 4th 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 100th 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 8th 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 7th Chapter, and likewise the Opinion of acquest of new Matter, and expulsion of part of the old, in the 8th Chapter, and have entertain'd the Opinion of the An­cient and some of the Modern Philo­sophers, in the 9th 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 100th part or 1000th 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 4to 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.

REMARKS upon the Essay touching GRAVITATION of FLUIDS.

REMARK I. Upon the Second CHAPTER.

THis Remark fiercely, and in the first greeting, chargeth the Se­cond Chapter of the Essay with con­tradiction, in that in some places thereof, it is said, That Gravity is a quality whereby heavy Bodies tend to the Center; and yet in other places it is said, That Gravitation is but Nisus or Conatus ad Motum; and therefore that it is not improper to say, that Bo­dies that have a Nisus or Conatus ad Motum verticalem, do gravitate up­ward; which the Remarker thinks [Page 135] to have been more properly expres­sed by Levitation; and to call it Gravi­tation, is repugnant and contradictory to what is said of the quality of Gra­vity.

But to avoid a frivolous contention of Words, it might have been fairly and easily observed, that in truth all kind of Gravitation is but Motion or Conatus ad Motum.

But in that Conatus or Nisus ad Motum, we are necessarily to consider two things.

  • 1. The Principium Motivum.
  • 2. The Terminus Motus, or Conatus ad Motum.

The Principium Motivum may be various, and tending to various ter­minations, it may be extrinsecal and accidental; as when I throw a Stone into a Bucket of Water, the motion of the Water is thereby caused up­ward, and raiseth its Superficies, and the motion of the Water upward, is not altogether improperly called Gra­vitation upward, coming from an ex­ternal force.

[Page 136]Again, The Principle of the Mo­tion, or Conatus ad Motum, may be in­trinsick, and from that intrinsick Principle, may have a motion or Co­natus ad Motum downward, which I call the intrinsick quality of Gravity; this intrinsick quality governs and enclines the Motion and Conatus ad Motum, to a central termination, when it hath no collateral impediment. Any man with half an eye may see here is a Conatus ad Motum of the heavy Body to a central motion, which is its Gravitation, and yet the Principle that impresseth this kind of termina­tion of its Motion, is that which I call, and call truly, the Quality of Gravity in the heavy Body.

In the very Instance of the Motion of Water in relation to the Rundle of Wood, specifically lighter than Wa­ter, we may observe both these Gra­vitations or Motions the Water pres­seth downward from its intrinsecal Principle or Quality of Gravity, and thereby undermines and gets below the Rundle; and then by a relative, [Page 137] occasional or accidental motion, in relation to the Rundle of Wood, it presseth upward, and drives up the Rundle of Wood with a force and kind of gravitation or motion upward to the Superficies of the Water: The same Water hath these various termi­nations, one downward, from its own intrinsick quality of Gravity, though the exercise thereof be suspen­ded till it find a lighter Body within its dimension to exert it; the other, upward, in relation to the Rundle of Wood, which by circumpulsion it drives upward.

And therefore the kind consequen­ces that I hold, there is nothing but mobility in Bodies, and that I use the phrase of Gravity according to the vulgar acceptation, and as Idolum fori, or that the actual descent of Water or other heavy Body, is from a di­stinct Being, as is inferred in the first, second and sixth Sections of that Chap­ter, are but mistaken Collections, and have no concession from me or any thing I have therein asserted, nor are at all true, as I think.

[Page 138]As to the 4th and 5th Illation in that Remark, where it is said, The Water hath no Nisus ad motum upward into the Tube immersed, and stopped at the lower end, till opened, that, in the Sequel of this Enquiry will appear not to be altogether true: But if it were never so true, yet it impugnes not what is above by me delivered; for the Water is driven up into the Tube by the weight of the body of the Water in the Bucket, upon the Cavity of the Tube filled only with Air, and so the rising of the Water into the Tube, is by the pressure of an accidental Position, and the flui­dity of the ascending Water, meeting with an Element in the Tube lighter than the Water.

We see in a pair of Scales a weight of two pound in one Scale, makes the weight of one pound in the other Scale, to ascend, though both are heavy Bodies; and this by Mechanique and Statique Principles: So in the Siphon, A B, Water poured into the Leg A, raiseth the water in the other [Page 139] Leg, to an equal Superficies, upon ne­cessary statique grounds, without cal­ling in any subsidiary Spirit of Na­ture to effect the ascent; for rhe Si­phon is a kind of natural Libra: And so when the Tube stopped with the Finger beneath, is immersed into a Bucket of Water, and then opened, the circumjacent water being both fluid and heavy, is driven up into the vacant Tube, till it come to an equal Superficies with the rest of the water in the Bucket, by a kind of due Equi­pondium. And all this is most regu­larly and necessarily effected accor­ding to the common Mechanism of Statique Principles, without any help from the supposed Spirit of Nature, to fetch out the Air out of the Tube, or to raise the Water into it.

There be many accidental causes of the motion of water vertically up­ward, which yet consist with its in­trinsecal principle or quality, which I call Gravity, or Conatus to a central motion; For instance,

1. It is moved upward by casting [Page 140] into it a heavier Body, which takes up some of its room; as throwing a Stone into a Bucket of water.

2. It is moved upward by attra­ction; as in Pumps and Syringes.

3. It is moved upward, when within its own dimension it meets with a lighter body than it self; as in the instance of the Tube of Air immersed, and then unstopped at the bottom; or where a Rundle of lighter Wood is immersed in it, it is apparent the water raiseth it, and casteth it to the Superficies with a kind of Force; so that it will leap above the Superfi­cies of the water, when it comes thi­ther. But these accidental vertical Motions do not at all take away the intrinsick principle of its Gravity, but consist with it; and therefore it is no contradiction to say that Gravitation is but Conatus ad Motum, be the mo­tion lateral or vertical, or central; and yet at the same time to say, that Gravity is a quality in heavy bodies, that specificates and determines their Conatus ad Motum to be central or per­pendicular.

REMARK II. Descent of Bodies.

THis Remark would surely have have been spared, if the Author had been pleased to have read the next Page; where it is affirmed, that Water powred through the Air, hath a direct central Direction and Gravita­tion, Pag. 14. of the Essay.

REMARK III. Touching the Gravitation of Parts of Solid Bodies one upon ano­ther.

THat every part of a Solid Body hath its common quality of heaviness, and would in a state of [Page 242] Separation, descend, and that every part contributes to the weight of the whole, is no where questioned; on­ly when the Body is in continuity, and of an equal consistence, that there is a suspension of actual Gravitation of one part upon another, is that which is affirmed: But where they are of different Consistencies, there many times happens actual and sensible Gravitation of one part of a Solid Body upon another. This is obser­ved in the Third Chapter of the Nugae, pag. 1. And had it been observed, the Remark I suppose would have been spared.

REMARK IV, V, VI, VII. Upon the Fourth CHAPTER.

FOr the rendring my Thoughts more intelligible, touching Gra­vitation of FLUIDS, and to make my Approaches to it the more easie and fair, I give in that Chapter In­stances of solute solid Bodies, and how the pressure of their parts are refracted, I begin with meer gross Bodies, square Stones of a foot square; then descend to Wheat, Shot and Sand; and in these latter, I make my application to their own incumbency upon an Egg-shell, because not so easily ex­plicable by a perforation of their Base in respect of the exility of their Cor­puscles.

But yet I must tell the Reader, that allowing the proportion of their perforated Hole in the Base, to be but answerable to the exility of their [Page 144] Bodies, the coalition of more grains of Wheat, Shot or Granules of Sand at the same Orifice so proportioned, would stop their subsiding; as ap­pears to any that thinks it not be­low him, to observe in Hour-glasses, where the passage, though big e­nough for one Granule of Sand, will not admit the passage of two or three crowded together; and Wheat will quarre in the Binn of a Mill if not shaken by the Clack.

But as to the thing designed by these Instances, it is only to shew how by various, especially lateral pressures, the pressure of a Column of Stone, Wheat, Shot or Sand upon a subjected Body, is much broken. And certainly in solid Bodies, ita se habent minora ad minora, ut majora ad majora. If we had a good Magnify­ing-Glass, we should find the piling of the Granules of Sand upon Sand, though not so regular as is done by Masonry; yet holding a fair and well-near equal analogy to it; one Granule of Sand would appear to [Page 145] support two or three, and those again others; and the declivity of the mo­tion of the Sands would be conspicu­ous, and their bearing against the sides of the Vessel, and their declination from the middle of the Vessel.

But the great Objection that is all along made, is, that the Corpuscles of Water are not to be resembled to those of Sand, but are much more mi­nute and glib, and therefore the In­stances hold no proportion to that of water.

If I should admit the Remarkers Assertion, that Water is no continued Body, but consists of minute separate Corpuscles, yet it would not much ad­vantage the Objection, for these Cor­puscles are not Indivisibles, but Bo­dies consisting of trine dimension, and possibly there is not that dispro­portion between such an Atome of Water and a Granule of Sand, as be­tween a Granule of Sand and a white Pease, much less a Cube of 12 inches square. And certainly in Bodies, ita se habent minora corpora ad minus spa­tium, [Page 146] ut majora ad majus: But I must not admit of this Supposition, that Water is no continued Body; for cer­tainly Water conjunct, though it be a fluid Body, is as really a continued Body, as Steel or Gold.

But to render the Instances of Sand, &c. as reasonably explicative of this Phaenomenon in Water, I shall subjoin and explicate this rude Diagram.


Suppose C D a Vessel of Water, with its various Lines of Declivity, and perpendicular direction, if you [Page 147] please, A, the Egg-shell, F, my ima­ginary Cone or Cap, impending up­on it, B A, and A D, a Circle of wa­ter in the Base of the Vessel encircling the Egg-shell. I say it is impossible the Column of water incumbent on the shell, could press upon it, unless it could press upon and remove the circular Base of Water, encircling the shell, and unless that sink or remove by the incumbent water, the Egg-shell can be pressed no more in the in­stance of water, than that of Sand or Pease mentioned, pag. 7. of the Addi­tions to the Pamphlet. But since the encircling water B A D, is of the same texture, weight and consistence with the rest of the water, it must re­main unmoved as a Rock, and bear the pressure both of the perpendicular and declining water, which must ne­cessarily protect the shell from the en­tire pressure of a Column of water commensurate in Base to the Egg-shell, which cannot be without pressing up­on and displacing the circumjacent water, which is not possible; for now [Page 248] the water incumbent upon the shell, and the circumjacent water, make, as it were, one common Basis to the su­perior water.

The analogy therefore between the instance of the sand and water, and the accommodateness of the former to the explication of the latter, in this Phaenomenon of the non-gravitation of Fluids upon included heavy bodies, consists in these two Parallels.

1. Of the upper parts of the sand or water, in relation to the lower parts, viz. premendo the lateral and in­clining motion and pressure of both, breaking and allaying their perpendi­cular or central pressure.

2. Of the lower parts of the sand and water in relation to the upper, viz. sustinendo the Base of water or sand, circumjacent to the Egg-shell, contri­buting to the sustentation of the whole superior mass of sand or water, and every particle incumbent upon that Base, sustaining a numerous company of other Particles, and those again o­thers, so that the whole commensu­rate [Page 149] Column of the superior sand or water (abating that small proportion, which, for want of a better expression, I call a Cap or Cone) incumbent up­on the shell, cannot gravitate upon it. And thus I use my Masonry of cu­bique Stones to explicate the manner of the gravitation of Sand, and the Arch of Sands, to explicate how the perpendicular pressure of water upon a subjected body in a Column com­mensurate thereunto, is remedied; only in Sand the Monads and their mutual sustentation is more conspicu­ous to the Eye, than in Water; but in Water the advantage is in some re­spect more effective of this alleviation by the continuity of its Matter.


IT is thereby imagined, that the la­teral pressure being checked by the sides of the Tube should spend their direction perpendicularly down­ward, and so more endanger the shell, which, as it is evidently contrary to the Sense and Experience of the fact, so it is contrary to Reason; for the ten­dency of the lateral motion is still the same as at first, and the bare obstacle of its expansion cannot in a body of this nature, give it a motion of resili­tion to a perpendicular gravitation; and if it could, it is impeded by the intervening Sand.

As to the 9th Remark, it is answered in the Observations upon the 4th and 5th Remark: But by the way, the jum­bling of water hinders not its conti­nuity, so long as the parts thereof are in conjunction one with another.


IT is agreed between us, that Gra­vitation is Nisus ad Motum; but it never was, nor ever can be agreed by me or any person, that thinks be­fore he writes or speaks, that such a Gravitation may not be excited and directed by a quality inherent in the Subject, which may terminate that mo­tion, and incline and direct its motion to the Center. Gravity therefore is not of the same extent with mobi­lity, but it is a mobility determined in its termination by the principle that puts it in motion, which, in the in­stance in hand, is the quality of Gra­vity, which is a determinate specifical principle, determining the mobility of heavy bodies naturally to a central direction, though it may be some time accidentally impeded, and ordinarily impeded by the fluidity of a fluid body.


THat the parts of Water, when in conjunction one with ano­ther, are only contiguous, I do admit by way of Argument; but I no where admit it by way of Concession: for if I should, I think I should grant that which is by no means true. I on­ly therefore in that place argue, that were the parts of water solute, and only contiguous, yet even there the actual gravitation of them would be suspended as well as in Sand.

And because the business of conti­nuity and contiguity often occurs in the Remark, and great endeavours are therein used to prove the particles of Water and Air only contiguous, I shall here once for all, make some Ob­servations touching Continuity and Contiguity, that I may avoid Repeti­tion.

We learn both from the Ancient and [Page 153] Modern Philosophy, that Contigua sunt, quorum ultima sunt simul in situ, & non est possibile quod inter ea cadat aliquid quod habet situm. Continuum autem il­lud, cujus natura est quod inter partes ejus reperitur unus terminus communis, or, quorum ultima sunt unum in actu: which is a little clearer explained by the Moderns, that Continua sunt, quando ex pluribus quantis fiat unum totum nul­la sensibili commissura inter partes rema­nente; or, implicatio & incorporatio partium unitarum; so that they, as it were, run one into another without any sensible discrimination of their Moles or Situs.

Although in grosser Bodies there is more required than contiguity, to make them continuous, yet in Liquids, especially perfectly homogeneal, as Water and Water, Air and Air, Mer­cury and Mercury, there ariseth a con­tinuity of parts meerly upon their contiguity or contingency; for there­upon they presently incorporate, im­plicate and mingle so one with ano­ther, that there remaines no possible [Page 154] distinction of the parts united, one drop of water touching another, one portion of Air touching another, one little globule of Mercury touching ano­ther, become perfectly continued bo­dies without more ado, though they were before divided by their distance, and interposition of another Body; this is apparent to our very Sense, that these are undistinguishably united, in­corporated and implicated one in ano­ther by their very contact, as closely, though not so firmly as Lead, Iron, or Gold, after Hammering or Fu­sion.

In all Bodies that are in continuity, as there is a unity of Existence, so (ordinarily, though not alwayes) follows a unity of motion. It doth not alwayes follow, because there may intervene something that may disorder or break it.

But in things barely contiguous, as they are not in themselves united so regularly; ad motum unius non sequitur motus alterius, unless united by alliga­tion, as in Chains of several Links; [Page 155] by some other accidental intervention, as in the cohesion of distinct contigu­ous bodies, for the avoiding of Vacui­ty, as in polished Marble, &c. And herein we may easily observe the con­tinuity of Water.

Take a Siphon, and fill it with wa­ter, stopping both Legs with your finger, till the shorter Leg be immer­sed into a Vessel of water, the water will be entirely drawn out of the Ves­sel by a Funiculus of continued water, ascending and descending from the first immersion, as is shewed in the Additions to the Nugae.

But fill the Siphon with the finest Powder or Sand, that traction will never follow upon its immersion into a Vessel of the same or the like Sand or Powder; for in the former there is a traction by the continued Body of Water: But in the latter, the parti­cles are solute, and only contiguous, and will not cohere, but gives us the Proverb of a Rope of Sand.

And what is here observed touch­ing the continuity of Water, and the [Page 156] traction wrought in the virtue of that continuity, is observable touching the Air, and the traction wrought by its filaments, as appears most evidently in the Magdeburg Hemispheres, in the 18th. Chapter of the Difficiles Nugae, and in the raising and holding up of water in the heated Tube or Glass, de­scribed in the 16th. Chapter, which could never be effected, did the Air consist only of contiguous and solute particles, unless we should dream they were fastened together by Hooks or Chains.

And upon what hath been said, it is most apparent, that neither the softness of the Air, nor its easie di­visibility or separability by a Feather or a Cobweb, nor the attenuation of the particles of water into vapors, by the heat of the Sun, are so much as tolerable Reasons against their conti­nuity; for although the disjunction and separation of the parts interrupt the continuity between the parts, when actually separated, yet the se­parability or easiness of separability of [Page 157] the parts of it, are not so much as a shadow of Argument against their continuity, till such an actual sepa­ration be made. No man that thinks twice, can imagine that Lead in fusi­on, is less a continued Body, than when it was solid; or that Gold bea­ten into Leaf, is less continued than when in the Ingot, and yet the sepa­rability of its parts much more facile than before. And therefore the Fan­cy of contiguity only of fluid Bodies, is the effect of that Idolum Democrati­cum or Cartesianum, which with his imaginary Globuli, and their Ramenta, the Materia Subtilis, hath disordered mens Sentiments, as in many other things, so in this, touching Continuity and Ratio Continui.


I Am very well contented to be re­ctified touching the Nature of the Principium Hylarchicum of the Learned Remarker. I must confess, when I found so much of a Spiritual Nature attributed to it, and that great and ready accommodation of it to the sol­ving of most of the admirable Phaeno­mena in Nature, whether Mechanical or Vital, I thought it had been some intelligent Spirit or Intelligence; but now I understand that it is only pla­stick and vital, not intelligent, and doubtful whether sentient or not: But of whatever nature it be supposed to be, it seems necessary to prove its very existence by such instances as are not meerly Mechanical; otherwise I fear more is asserted than proved.


IN these Remarks lies most of the Elixir of the precedent Remarks. And besides, they offer at somewhat of experimental proof of what they assert, besides bare Notions; but how far these proofs are sufficient or effe­ctual, we shall see hereafter: And therefore I shall insist somewhat lar­ger upon them and the Observations that are to be made upon them.

Archimedes, in his Third Proposi­tion De Insidentibus Humido, tells us, that if solid Bodies, having a Bulk or Moles, be equally heavy to the Wa­ter wherein they are placed, being let down into the Water, are so immer­sed, that nothing of the Superficies of the Water is above them, yet they are not pressed downward.

And in the Sixth Proposition, he tells, that a Solid Body, lighter than the Water, being forced down into [Page 160] the Water, is driven up with such a force, as the Water having an equal Moles to that immersed Body, is hea­vier than that Body.

And this driving upward of the lighter Body, is by that circumpulsion of a heavier fluid Body upon another Body lighter than it self, which will (if it can) take up the place that the lighter Body hath invaded within its Dimensions, and the Limits of its Pro­vince.

And the truth is, the reason of the motion of a Ballance or Libra Artifi­cialis in the Air, wherein a heavier weight in one Scale, lifts up a lighter weight in the other Scale, is in effect the same with this natural libration between the heavier Body of the Wa­ter, and the lighter Body of the Wood; only here it seems like a Ballance in­verted, wherein the counterpoise of the Moles of Water being greater and more than the like Moles of a lighter solid Body, must needs overweigh it, and if it be possible, get below and un­der it, as in this Scheme.

[Page 161]


Suppose A, be a Cube of Wood of 6 inches square, immersed towards the bottom of the Cubical Vessel of Water C D, and lighter than the like Moles of water, this Cube takes up the room of 234 square inches, which (were not the Cube there) would be in a great measure taken up by the Wa­ter. The Cube of wood is environ­ed with a quantity of water equal in Moles to this Cube of wood, but ex­ceeding it considerably in weight, the weight of the water must necessarily preponderate the Cube of wood, and consequently must thrust it upward, that it may possess the place the Cube of wood hath invaded, and so in this Libra Naturalis the heavier Moles of [Page 162] water must necessarily drive up the lighter Moles of wood, as in the arti­ficial Scale, the heavier Scale raiseth the lighter.

And hence it is that without the aid of an Hylarchical Principle the Water bears and carries up the Rundle of light wood in the Instance so often magnified by the Remarker. For un­less the Rundle were so closely fast­ned to the Base, either by some glu­tinous matter, or by its strict jointing and adhesion to the sides or Base of the Vessel, as would be too strong for the water, to displace it, it is hardly pos­sible by any art whatsoever to make the Rundle so close to the Base of the Vessel, but the subtil particles of wa­ter will creep between the Rundle and the Base, and throw it up in spite of the imaginary Column of water, com­mensurate to the Rundle that is sup­posed to keep it down: and herein, as I before observed, the water hath acci­dentally, and upon this occasion a mo­tion upward, which yet is but the Consequent of its motion downward below the Rundle.

[Page 163]And upon the same account it is, if you take a hollow Cane, suppose one inch diameter, 12 inches long, let the Base thereof be filled with a quan­tity of Lead for about an inch, then let there be powred in 6 inches of wa­ter, and then there will remain 5 inches of Air in the upper part of the Cane, although the Lead be heavier than so much water, and the water in the Cane equal in specifical weight to so much water; yet as long as the whole weight of the Cane thus compounded, doth not equal the weight of a like Mo­les of water, this Cane immersed into a Vessel of water 12 inches deep, will not subside or rest at the bottom of the Vessel, but will be driven up to that height in the water, that the parts of the Cane subsiding in the water, will countervail a Moles of water e­qual to the weight of the whole Cane, and there it will swim erect. Experi­ence and the very Reason of the thing, makes the truth hereof apparent.

Stevin (that next to Archimedes, hath written best of Hydrostatiques) [Page 164] in his 5th Book, Prop. 2. supposeth nevertheless, that if this Rundle co­ver a hole in the bottom of the Vessel, it will not rise, but will be kept down by the impending Column of water commensurate to the Base of the Run­dle.

Albert Girard, the Commentator, denies this; unless the Rundle be of e­qual or greater weight than the like quantity of water.

But the truth lies between them both; for the Rundle lighter than the water, will be undermined in the Rims and Edges, and so the water will get out, do what the Artist can, if the Rundle be lighter than the like Moles of water.

But then when the water hath thus gotten a passage to pass through the Orifice into the free Air (upon which it hath been shewn, the Moles of wa­ter commensurate to the passage it hath now, presseth with its full swing) and if it meets with the Rundle in the way of its motion, so long as it stands in its way, it will gravitate upon it [Page 165] till the water hath wholly discharged it self through the Orifice.

And therefore the reason is obvious why there is some impediment in the ascent of the Rundle, when it is thus placed upon an Orifice, without cal­ling in any other principle than the natural pressure of the water upon that Orifice, now giving it an access to an Element that it can press upon, viz. the Air below the Orifice.

Just as we see in our Kettles and Brewing Furnaces, when they have a small Leak, the Servant throws in a handful of Bran, which though per­chance it would not so readily sink, much less sink to the Leak, yet the motion of the water to the Leak, will carry those light and small particles thither, which being crouded in by the weight of that Column of water that is commensurate to the Orifice of the Leak, stops it.

And the like is done upon a Leak in a Ship, where a light Fardel thrown out into the Sea, will be carried down to the Leak, and crowded into it by [Page 166] the water, & sometimes stop the Leak.

And therefore touching the gravi­tation of the Column of Water upon the Rundle of light wood, where there is a hole under it in the Base (which I add as an exception, pag. 57. and is no more than what Stevin tells us in the 5th Book of his Practical Hydrosta­tiques) both He and I must be under­stood where any little water passeth under the Rundle to the Hole, and therefore to clear that Experiment, and the reason of it, I made exact tri­als concerning it, as followeth.

I took a Cylindrous Bucket of about eight inches diameter, and five inches deep, and made a round hole in the bottom, of two inches diameter, and a rundle of light wood of 4 inches diame­ter, to cover it, with a stick in the midst,


to lift it up, or press it down, or to suspend the Rundle by it to a Balance, according to the Figure in the Margin, and made it as smooth and even to the Base of the Buc­ket as I could, and pressed it [Page 167] the Orifice, and filled the Bucket with water, yet the water, do what I could, would press between the sides of the Rundle and the Base of the Vessel, and so discharge it self in some small pro­portion through the Orifice, and all that while it did so, the Rundle, though lighter than the like Moles of water, was kept down by the pres­sure and issuing of that small quan­tity of water, and so continued, till al­most all the water had thus run out; the reason whereof is before given, viz. the motion of the water to the Orifice, kept down the Rundle. But then emptying all the water, and rub­bing the Orifice and Rundle dry, I applied Neats-foot Oyl to the Rundle and Base, which by its glutinous con­sistence kept the Rundle and Base close together, and applied the Ballance to the hook of the Handle of the Run­dle, and it was not severed from the Base by less than 7 ounces, though the Rundle weighed not above an ounce.

Then oyling the Base and Rundle as before, and uniting them, I filled the [Page 168] Bucket with water, which by reason of the glutinous Oyl, did not pass, nor sever the Rundle from the Base.

Then fixing the Rundle as before, to a Scale, I tried what weight was suf­ficient to sever the Rundle from the Base, being under the supposed pres­sure of that imaginary Colum of wa­ter of 5 inches deep, and I found that very near the same weight would se­ver it from the Base under water, as did sever it when it lay dry; and though in several trials there was some little disparity, which might arise from the unequal strictness of the juncture, either by the quantity of Oil, or posi­tion of the Rundle, wherein I could not possibly be exactly uniform, yet the Rundle was separated under tnat Moles of water, sometimes with seven ounces weight, sometimes with eight; but at most, with ten ounces. And yet in the Column of water commen­surate to the Rundle, were 55 square inches; which, according to the ex­actest computation of the weight of water, amounted to at least 24 ounces [Page 169] weight: And this sheweth that gra­vitation of the water upon the Run­dle, is to be understood, when there is some passage to give the water mo­tion. So that it seems to me, the Con­clusion that the Remarker makes from this Instance, in favour of the Hylar­chical Principle, or the supposed Gra­vitation of a Cylinder of water upon the Rundle where no water passeth, must be laid aside, as no way assisting his Hypothesis, in impugning mine.

And therefore, whereas Stevinus in his Practical Hydrostatique, ubi supra, grants, that the Body of a man, or other Body, lying flat upon the bot­tom of a great Vessel of water, feels no considerable pressure of the in­cumbent water, yet if there be a hole in the bottom of the Vessel under that bo­dy, it shall find a considerable pressure of the incumbent water; this is to be un­derstood cum grano Salis, viz. if the Body do not so entirely and closely stop the Orifice in the bottom of the Vessel; but that the water finds a passage be­tween it and the Base, to discharge [Page 170] it self, the Body then indeed shall find a pressure from the superior water at least, according to the weight of such a Column of water as can thus dis­charge it self between the Body and bottom through the Orifice. But if it stop the Orifice so entirely and close, that no water can pass that way, there will ensue no Gravitation upon the Body, by reason of that Hole or Ori­fice thus stopped; for it is as if it were not: the body becomes as it were part of the entire close Base of the Vessel.

And thus much may serve to expli­cate the Phaenomenon of the orifice or hole in the Base of a vessel under the Rundle.

But now as to the Instance given in the 20th Remark, whereunto the Learned Remarker appeals as an irre­fragable Instance to take away at once the Mechanical Accounts of Conti­nuity and Architecture, I doubt the Au­thor gives us this Experiment without exact trial; for if he had tried it, I think he would never have urged it.

The Experiment, as I take it, is this; Take a Cylindraceous Bucket [Page 171] of 63 parts in the internal Diameter, and let another Cylindraceous Bucket be of 62 parts external diameter, with 4 sloping holes at the bottom, and put the less into the greater, and fill them up with Water to the Brims, then take away your hand, and the narrower Bucket will emerge, leaving no more in the water than what is equal to the weight of such a Moles of water as is equal to the whole Vessel in weight.

I shall take this Instance in pieces, and then we shall see what is in it,

And for the better clearing of it, I shall make my way to it by Instances, though not altogether like it, yet gi­ving a great light to it, and it may be, to other matters of this kind; and I shall first consider the comparison be­tween Bodies specifically heavier than the fluids, and then in Bodies specifi­cally lighter.

If there be a Bucket or a Cylindra­ceous Vessel, suppose 9 inches deep, then take a Cylinder of 9 inches high, and narrower than the Bucket, but of a Material specifically heavier than [Page 172] the like Moles of water, as suppose it Tin or Ebony; if the Vessel be filled with a Moles of water of twice or thrice, or ten times the extrinsick weight of that Cylinder, yet the Cy­linder will still sink to the bottom, by its advantage of its intrinsick or speci­fical over-weight or heaviness more than water.

Now I shall consider the proportion where the solid Body is specifically lighter than Water or other fluid Bo­dy in Which it is immersed.

I took a Cylinder of wood 4 inches deep, and 4 inches diameter, which weighed 18 ounces.

The like Bulk of Water equal in Bulk to that Cylinder of Wood, weighed 32 ounces.

So that the Water had a specifical or intrinsick weight near double to the Wood.

And consequently the Wood being immersed in a Vessel of Water, near one half thereof lay above the Super­ficies of the Water, as it must do ac­cording to the Rule of Hydrostatiques. [Page 173] I took 2 Cylindrous Vessels, one of 6 inches diameter, the other of 9 inches diameter; I put the Cylinder of wood into the Vessel of 6 inches diameter, and as much water as countervailed the Wood-Cylinder in extrinsick weight, but not in Bulk, and the wood-Cylinder would not swim; for though the intrinsick weight of the Water was near double to the weight of the Wood, yet the extrinsick weight of both was equal, viz, 18 ounces, and so there was an Equipondium be­tween the Water and the Wood, and consequently that Water would not raise the Wood from the Base of the Vessel.

But putting in so much Water more into that Vessel, as that the la­teral or ambient Water would rise so high as to cover a little more than one half of the Cylinder of Wood (namely, such a quantity thereof as was equal to a Moles of Water, equi­ponderating the weight of the whole Cylinder of Wood) then the Cylin­der of Wood would swim, though [Page 174] the Base of the Water between the Cylinder of Wood and the bottom of the Vessel had not half an inch in depth.

And the reason is, because the entire water both lateral, and at the bottom, is one continued body, and entirely presseth the Cylinder of wood upward, in as much as the lateral or ambient water hath gained an height upon the Cylinder, somewhat more than the immersed parts of the Cylinder of wood proportionable to a Moles of water equal to the whole weight which that whole Cylinder of wood amounts unto; for the Cylinder of wood weighed but 18 ounces, but the whole weight of the water might be 20 ounces or more.

But again, put this Cylinder of wood into the Cylindrous Vessel or Bucket of 9 inches diameter close to the Base, and pour in four or five times the quantity of water into the Bucket more than what was in the former Cylindrous Vessel of six inches diameter; as suppose it be five pounds [Page 175] of water, yet unless the Superficies of that water rise not to more than the height of half the Cylinder of wood, viz. something more than two inches high upon the sides, the Cylinder of wood will rest upon the Base, and will not swim: And the reason is, because the water presseth according to its altitude, and not according to its amplitude, and therefore though the whole water in the 9 inches buc­ket be five times more in weight than the Cylinder of wood is, if it rise not so high as to take something more than half of the height of the Cylinder of wood, namely, such a quantity there­of as is commensurate to a quantity of water equal in weight to the whole weight of the Cylinder of wood, the Cylinder of wood would not swim, but will stand upon its Base at the bot­tom of the Vessel. And this is the reason why a Ship or Vessel that draws for the purpose 4 fathom of water, will swim in a narrow Cut or Chan­nel that hath 5 or 6 fathom of wa­ter, though the Channel be less than [Page 276] 20 fathom over in breadth; and if the Channel were 20 Miles over, and of a less depth than the Ships draught of water, viz. 4 fathom, the Ship will be on ground, and will not swim, and yet the weight and quantity of whole water in the broader Channel, is many thousand times more than that in the narrow Channel.

And the like Instance may be given in Floats of Timber in a deep and nar­row Channel, and a broad and shallow Channel.

For the pressure of water is more or less according to the height or depth of water, and not according to its amplitude or breadth, though the wa­ter with ampler Superficies be a thou­sand times more in weight and bulk than the deeper water.

Now to the Buckets instanced in the Remarks;

If there be a Bucket of 20 inches diameter, and another of equal height but of 6 inches diameter, fill the lesser Bucket with water, and place it in the middle of the greater Bucket, and [Page 177] then fill the circumjacent sides of the greater Bucket with water, though the greater Bucket hold 5 times the water of the lesser Bucket, yet (allow­ing, as I must, the wood of the lesser Bucket to be but of the same weight with the like Moles of Water) the lesser Bucket will still remain conti­guous to the bottom, and will not rise one inch, and the reason is, because the water without, and the water within the Bucket, though of a dif­ferent Moles, yet have the same speci­fical weight, and (as to this purpose) as if it were so much unvesseled wa­ter (I say, as to this purpose, for as to the other purposes, there will be a difference, as I shall shew hereaf­ter.)

But if the lesser Bucket be totally empty, or only filled part with wa­ter, suppose half way, then the water in the greater Bucket, will drive up the lesser; but not till only so much be immersed as countervails its de­fect of weight, according to the 4th. 5th and 6th. Proposition of Archimedes, ubi supra.

[Page 178]But now to come to the Experiment of the lesser Bucket or Cylindraceous Vessel perforated in the bottom, and then water poured into the greater or lesser (for it comes all to one ac­count) will the lesser Bucket emerge, unless held down by the hand? By no means in the world; for the water will presently pass through the perfo­rations from one Bucket to the other, till they come to one common su­perficial height, and still the lesser Bucket will rest upon the Base of the greater, because they have an equi­pondium; supposing (as we must) that the wood of the lesser Bucket is of equal specifical weight to the like Moles of water. Indeed it is true, that if the holes be small, so that there must be a Mora before the water can be conveyed from one Vessel to ano­ther, then if the water be plentifully poured into the sides of the greater Bucket, the lesser will rise till it have received so much water as equals the Superficies of both, and then the les­ser Bucket will subside contiguous [Page 179] to the Base; for the water in both Buckets being of an equal height, was in aequipendio.

So that as the Instance it self con­duceth little to the ends propounded, were it true; so I doubt it is mista­ken, and upon trial will not be found true.

I did expect to have met with an Objection which may seem prima facie to impugne what I have formerly de­livered; yet upon a strict examination it would not have any efficacy.

Take a Cube or Cylinder of wood of equal intrinsick weight with so much water, suppose it a Cube of six inches diameter, and put it into a Cy­linder or cubique Vessel of water of eight inches deep, and twelve inches diameter, this Cube or Cylinder would rest two inches above the Base of the Vessel, and would not gravi­tate either upon the two inches of wa­ter in the Base of the Vessel, nor upon any Body that were but two inches thick, and lay between the Cube and the Base of the Vessel of water, yet [Page 180] here can be no lateral pressure or per declive in the Cube, it self being solid, and having only a central gravita­tion; so that it may seem the lateral pressure which is the Subject of the Eighth Chapter of the Essay, applied to the Water, is no ingredient into its Non-gravitation.

I answer, that the Fact is true, but the illation thereupon is not consequen­tial.

In my Observation upon the 4th, 5th, and 7th. Remark, I say the non-gravi­tation of Fluids is in relation to the pressure of the upper parts upon the lower, which is per declive premendo: and in relation of the lower parts to the upper sustinendo; now although in this Instance the former hath no part, yet the latter hath.

In this instance the Cube or Cy­linder is sustained and born up by the subjacent water, which is as the pe­destal upon which it is bottomed; and therefore neither doth nor can press below the position it holds: But suppose the Body subjacent to it, [Page 181] were 6 inches deep, then it would be under the pressure of that Cylinder or Cube of wood, as much as the weight of 4 inches of the Cube a­mounts to in the water, and the body would be under a pressure commensu­rate at least to so much weight as the Cube, or so much thereof as is thereby driven out of the Superficies of the water, exceeds in its extrinsick weight the like Moles of water, with so much of the Cube as lies in the water.

But on the other side, where there is nothing impending upon the sub­jacent body but the superior imaginary Column of water, the subjected body is not compressed at 9, 6 or 3 inches immersion below the Superficies of the water, partly by reason of the Me­chanism (I do not say Masonry of the water, though that expression is fre­quently, but needlesly used by the Re­marker) and partly by reason of the va­rious termination of the motions of fluid Bodies.

[Page 182]It shall not be altogether imperti­nent to subjoin the ensuing Experi­ment.

I took a Cube of wood 4 inches square, and very near of an equal speci­fick weight of the like Moles of wa­ter; for it did not rise half an inch a­bove the water, and being let down to subside freely in a Vessel brim-full of water, it threw over a portion of wa­ter very near of the same weight with it self, viz. 28 ounces and a half.

This Cube being laid into a Vessel of 8 inches deep of water, therefore was raised at his Base about 4 inches above the water in the Base of the Vessel, which water sustained it. And now it had been unquestionable that if a body of less than 4 inches thick, had been subjected under the Cube, it would have sustained no pressure from the water nor from the Cube, which was entirely born up to that height by the subjacent water.

But if the body subjected to the Cube, had been 5, 6 or 7 inches thick, it would have been pressed upon by [Page 183] various proportions from the impen­ding Cube.

For fixing a string and hook to the middle of the Superficies of the Cube, it required near 12 ounces in the op­posite Scale, to raise the Superficies 2 inches above the water; near 20 ounces to raise it 3 inches above the water; and near 28 ounces and a half to raise the lower Superficies of the Cube equal in height to the upper Superficies of the water, which answe­red the full weight of the Cube of wood; and therefore according to these proportions, it would gravitate upon a subjacent body that gave it the like elevations.

But in water we see the pressure dif­ferent from the pressure of such a woo­den Cube; for in whatsoever depth the subjected body is immersed, whe­ther deeper or shallower, it sustains no sensible difference of the pressure of the Column of water impending upon it, nor indeed any sensible pres­sure at all, though at five or ten fa­thoms deep; which, as it gives us the [Page 184] difference between the pressure of a solid and fluid body, upon a body in water subjected to it, so it gives us the reason of it, viz. the pressure of the solid body is impeded only by the subjected water, bearing it up, viz. sustinendo. But there are two impe­diments that hinder the pressure of the superior water upon the lower water on the body under it, viz. the sustentation of the superior water by the inferior; and likewise the lateral and declivous motion of the water, refracting its perpendicular pressure, while it is solute water.

And now because that the various habitudes of heavier or lighter bodies immersed in fluids heavier or lighter than themselves, seems to be a pleasant, and possibly a useful Specu­lation, and yet is difficult to be di­stinctly, and explicitly, and clearly declared: And possibly in what is before said in this Observation, the same is not so distinctly delivered as might be wished; I shall therefore desire the Readers pardon, if I resume [Page 185] and repeat much of what is before said, and digest the whole in some­what a clearer method.

First, I shall declare the difference between the terms of intrinsick and extrinsick weight, whether of fluids or solids, and what I mean by those terms, and how one body is said to exceed another in intrinsick or extrin­sick weight, or both; That body which hath more of bodily Moles or Matter than another body of the same dimension, is intrinsecally heavier than that body which hath the same dimension, and yet hath less corpore­al Matter or material Substance in it; and therefore is denser and crasser than the latter, and the indication of that density and crassitude is by the over­weight it hath over the other body; as a cubique inch of Gold is heavier, and therefore hath more of material substance than a cubique inch of Brass or Iron; and a cubique inch of Mer­cury is heavier, and therefore hath more of material substance in it than a cubique inch of water.

[Page 186]And therefore a heavier body im­mersed into a lighter fluid, as a cubique inch of Gold, Brass, Iron, &c. into water, though it take up but the room and dimension of a like cubique inch of the water wherein it is immersed, must needs sink into the water, and drive up that cubique inch of water in its motion of descent; for it out-weighs it: and as in an artificial bal­lance, the Scale that is charged with the greater weight, raiseth up the o­ther that hath the lesser; so it is in this natural libration between the heavier body and the lighter fluid. And that I may here say it once for all, there is a most perfect analogy between the artificial Ballance and this natural Ballance, in relation to the motions of and in fluids; and he that means to have a true image of the latter, must attain it best by comparison of it with the former.

A body that is specifically or intrin­secally lighter than another, yet by accession, or accumulation, or acqui­sition of more parts of Matter than [Page 187] another body intrinsecally heavier, hath, may thereby extrinsecally, and in denomination, and also in its effect of preponderation, be heavier than that other; as two pounds of water is heavier extrinsecally, and in prepon­deration than a pound of Gold, though intrinsecally heavier: And therefore, if a Cube or Cylinder of wood be sup­posed intrinsecally lighter than water, yet if such a Cylinder of wood, weigh­ing 4 pounds, be immersed into a like cylindrous Vessel of water, which wa­ter hath not 4 pounds of weight, the cylinder of wood will sink, and will not emerge, because in extrinsick weight it exceeds the extrinsick weight of the water in the Vessel into which it is immersed. But if the wa­ter be of the weight of four pound and a half (and in a due position, as shall be shewed) the cylinder of wood will rise and swim in the water, because, now as well the extrinsick, as the in­trinsick weight of the wooden cylin­der is over-weighed by the water.

If a body that is intrinsecally hea­vier, [Page 188] be immersed into a body intrinse­cally lighter, as Gold into water, it will subside, as hath been said: But yet a body intrinsecally heavier than the fluid wherein it is immersed, may accidentally be extrinsecally lighter than the body wherein it is immersed, namely, when it acquires a Bulk or ca­pacity so large, that a like Moles of water will be of a greater weight than such an immersed body specifical­ly and intrinsecally heavier, and then that body, though intrinsecally hea­vier, will swim upon the water, and be sustained by it.

The most obvious Instances of this kind, are two, viz.

1. When that body intrinsecally heavier is mingled and concreted with other bodies intrinsecally lighter than the fluid wherein it is immersed, and so the whole concrete immersed body weighs less than the like Moles of water would weigh; as where a small quantity of Gold or Lead is mingled with a greater quantity of wood lighter than water, and so both [Page 189] make up a concrete body lighter than so much water.

2. When the body intrinsecally hea­vier, is formed into a Cavity, as in Tin, Silver or Lead-Bottles, though the Material be specifically heavier than water, yet if they have such a dimension as that a quantity or Moles of water, of the same external dimen­sion, will exceed such Bottle (as it stands empty) in weight, this body intrinsecally heavier, yet extrinsecally is lighter than the water wherein it is immersed, and therefore will be su­stained by it.

And upon this reason it is that Ships and other Vessels are born up by the water, although they are of­ten lad [...] with great Ordnance, Bul­lets, and other things intrinsecally heavier than the like quantity of wa­ter; yet in as much as the whole Ship or Vessel hath a great Cavity, and takes up room in the Sea, pro­portionable to that structure, and a Moles of water commensurate to the hull of the Ship, as it hath that concave [Page 190] posture, is of much greater extrin­sick weight than the Vessel, there­fore it is born up and sustained by it. And thus a body intrinsecally hea­vier than a fluid wherein it is immer­sed, may be extrinsecally lighter.

1. In respect of its concretion or composition.

2. In respect of its structure and ca­vity, which gives a greater ampli­tude to it. That body is said to be both extrinsecally and intrinsecally heavier, when it exceeds another body in both respects, as an Ingott of Gold that weighs two pounds, is both extrinsecally and intrinsecally heavier than an Ingot of Silver, weighing only one pound.

And thus far concerning weight extrinsick and intrinsick.

Secondly, The Second thing which I intend, is, to declare the various habitudes of heavier or lighter bo­dies, with relation to the fluids in which they are immersed; whereby possibly much of the Learning and Experience De insidentibus humido, [Page 191] may be explicated, namely,

1. Where a body specifically or in­trinsecally heavier, is immersed in a fluid intrinsecally lighter than it self, as Gold, Lead or Iron in water.

2. Where a body is immersed into a fluid of equal weight with it self, which though it may be difficult to at­tain, yet attainable it is, as shall be shewed.

3. When a body specifically or intrinsecally lighter, is immersed in­to a fluid, and intrinsecally heavier than it self; as a Globe or Cube of Fir or Elm into water, which is much heavier intrinsecally than such light Woods.

4. When a body intrinsecally ligh­ter, y [...] extrinsecally heavier than that portion of fluid wherein it is im­mersed, be equal in weight to it, as where a Globe or Cube of Fir or Elm, weighing six pounds, is immersed in­to a Vessel of water containing just six pounds weight of water, or any quantity less than it. Therefore,

1. If a dense body being immersed [Page 192] in a fluid intrinsecally lighter than it, that dense body will subside to the bottom, though the fluid body in ex­trinsecal weight be more than forty times of greater extent than such a dense body; as if a Cube or Globe of Lead or Mercury, though but of an inch diameter, be cast into the deep Ocean, for the Reasons before given, where I treat of the difference between extrinsick and intrinsick disparity of Gravity: Only it hath those Excep­tions before given, touching the mix­ture of such heavier body with a lighter, and the configuration of such dense body into Cavity or hollowness, for the Reasons there given, which I need not repeat.

2. If a dense body be immersed in­to a fluid of an equal intrinsick weight with such dense body, it is generally thought that such dense body will keep any position that it is put into, if placed near the top, or in the mid­dle, or near the Ballance of the Ves­sel containing the fluid (though I have for the most part observed it to [Page 193] rise towards the Superficies of the fluid, and hold its upper Superficies equal to it) as suppose a Cube of water six inches square weigh 14 pound, a like cubique piece of wood of the same di­mension and weight, will stand at all positions in a Vessel of 7 or 8 Gallons of water; for such a dense Body is as so much water in this respect, they being of equal Bulk, and equal intrin­sick weight. But it is a very diffi­cult matter to find just such an equa­lity between Solids and Fluids, being of such different textures. The best Expedient is by a hollow Vial-Glass, reduced to such an equipondium by im­mission of small leaden Shot into it, till the Glass and Shot arise to the just equipondium of a Bulk of water e­qual to the whole Superficies of the Glass.

3. When a Body intrinsecally lighter than a Fluid is immersed in such fluid, part of that lighter Body will rise a­bove the Superficies of the water, or other Fluid into which it is immersed, and will leave so much of it self un­der [Page 194] the Superficies of the water, as is equal to a Body or Bulk of water fully commensurate to the whole weight of such immersed Body. For instance, Suppose a Globe of light wood of six inches diameter weigh 5 pound, and a globular portion of water of the like diameter weigh 10 pounds, this globe of wood immersed in a large Vessel of water, will rise so that one half there­of will be above the Superficies of the water and the other half will be be­low the Superficies of the water; for the intrinsick weight of the water is double to the intrinsick weight of the wood; so that a portion of water equal to half the Globe of wood, weighs as much as the whole Globe of wood. And the like proportion will hold where the Globe of wood is lighter than the like portion of water by one third, or one fourth, or one sixth part, mutatis mutandis.

4. If a gross Body (suppose of wood) specifically lighter than the like quan­tity of water, be immersed into a quan­tity of water extrinsecally lighter than [Page 195] that immersed Body, that Body, though specifically and intrinsecally lighter, will not rise from the bottom of the Vessel, but will sink down to the Base or bottom of the Vessel, and remain contiguous to it, notwithstanding the intrinsecal overweight of the water to the immersed Body; as if in the former instance, a Globe of wood of 6 inches diameter, and 5 pound weight, be lighter by half intrinsecally than the like portion of water, if this Globe of wood be immersed into a cylindrous Vessel of 7 or 8 inches diameter con­taining 4 pound weight, nay 5 pound weight of water, the Globe of wood shall not swim nor rise from the Base of the Vessel, and the reason is apparent, because though in intrinsick weight, the water is double to that wood, yet in extrinsick weight the Globe of wood in one instance exceeds, in the other instance equals the extrinsick weight of the water, and so the intrin­sick weight of the water, is over-mat­ched by the extrinsick weight of the wood, and therefore cannot preponde­rate [Page 196] it, nor consequently drive it up; as in a pair of Scales, if there be two pound of Feathers in one Scale, and but a pound of Lead in the other, the pound of Lead, though intrinsecally heavier than the Feathers, will not raise the Scale of the Feathers, but will be raised up by them; and if in one Scale there be two pound of Fea­thers, and in the other two pound of Lead, neither Scale will be raised by the other, but stand in a state of rest, because in Aequilibrio.

5. If a Cube or Globe of wood of six inches diameter, and weighing six pound, be but half so heavy as the like Globe or Cube of water (weigh­ing for the purpose 13 pound) and be immersed into a Vessel of water ten or twenty foot square, which is filled with water only to two inches deep; though this water be of an intrinsick double weight to the Cube or Globe of wood, and extrinsecally it may be a­bove forty times more weighty than that Cube or Globe of wood; yet that Cube or Globe of wood will [Page 197] subside to the Base of the Vessel, or rest there in contiguity to it, without any swimming or bearing up above the Base of the Vessel. And the reason is, because the strength of the pressure of water is alwayes secundum altitudinem vel profunditatem, and not at all secun­dum latitudinem vel amplitudinem; and the water in the Vessel rising but two inches high, doth not equal the half weight of the Cube or Globe, which requires somewhat more than three inches of water to overmatch the ex­trinsecal weight of the Cube of wood, without which, it will not be moved by the preponderation of the water; but the wood will preponderate the energy of that expanded water, or at least be in aequilibrio with it, and so not moved from the Base of the Ves­sel.

6. But if in the Instance last given, a Globe of wood of six inches diame­ter and six pounds weight, being but of half the weight of the like Globe of six inches diameter of water (weigh­ing therefore 12 pound) be immersed [Page 198] into a cylindrous Vessel of water of 7 or 8 inches diameter, and of such a depth as may hold 7 or 8 pound of water, without being forced over by the immission of the wooden Globe into it, and let there be but 7 or 8 pound of water powred into it, and then let the Globe of wood of half the intrinsick weight of the water be put into it; or let the wooden Cube be first put in, and then the 7 pound of water; here the water between the Base of the wooden Globe and the Base of the Vessel, it may be, will not be an inch deep; but the water in the sides of the cylindrous Vessel may rise four, five, or six inches higher. In this Instance, this wooden Globe will swim, and the reason is plain.

1. Because the water in the Vessel is not only intrinsecally, but also ex­trinsecally heavier than the Globe of wood, this weighing only 6 pounds, and the water in the Vessel 7 or 8 pounds; but that over-weight of wa­ter alone would not be sufficient to bear up the Globe of wood, as is shew­ed [Page 199] in the next precedent Observation. Therefore,

2. The immediate reason thereof is, because the ambient or lateral water between the Globe and the Vessel, ri­seth to above half the diameter of the wooden Globe, and presseth secundum altitudinem, upon the little portion of water next the Base of the Vessel, as a weight of water of near 7 or 8 pound and so exceeds the whole weight of the Globe of wood.

But if by reason of the amplitude of the Vessel, the lateral water encir­cling the Globe of wood, had risen but an inch or two above the Base of the Globe of wood, that would ne­ver raise the Globe of wood from the Base of the Vessel, but there it would stand contiguous to the Base of the Ves­sel; or if the Globe of wood were put into such a Vessel of water, it would sink to the bottom, for it preponde­rates the weight of the water in such a position; these Figures will explain it.

[Page 200]


In the lesser Vessel A B, where the 7 or 8 pound of water riseth never so little above the diameter of the woo­den Globe C, the wooden Globe of six inches diameter, and 6 pound weight, will swim: But in the greater Vessel, or where by reason of its amplitude, the lateral water doth not arise above the diameter of the Globe, the Globe will not swim, but rest contiguous to the bottom, though the water in that Vessel were 20 or 40 pound weight.


THis Remark is sufficiently answe­red before, where I say that heavi­ness in bodies, is an intrinsick quality, that it is not mobility at large, but a spe­cial or specifick mobility, whereby its Gravitation is naturally determined to be central. That mobility upward in heavy Bodies, is occasional and acci­dental, and not purely natural, as a heavy body.

I must confess, I do not understand what the Remark means, when it says, that Water hath no tendency to mo­tion downward, but when it is out of its place, what is meant by the place of Water? Is it a place determinate with relation to the position of the Vniverse? If so, we find no place in Nature, but the Water will descend from it, unless it be in the very indi­visible Center, which though it be the termination of its motion, was surely never intended for its place, be­cause [Page 202] never ample or capable to receive it; let the water be in the Ocean, or in the middle Region of the Air, or in the Bowels of the Earth, it will still, as a heavier Body, descend, if it be not impeded: Or, is the place of it, that place where any portion of wa­ter is placed; suppose in a Vessel upon my Table, or upon the top of my House, or on the top of a Steeple; yet there this water will still descend if it be not impeded? Or is it, that the Wa­ter having gotten into any place in its fluid consistence, it is now become its natural place per occupationem, and all other Bodies invading that place, are intruders, and put it out of its place, and so give it a Nisus downward? But the Water it self, when I remove a Vessel of it out of the River, into a Boat, or upon the Shore, invades the place that the Air before had, and so cannot be the proper place of the Wa­ter.

So that upon the whole account, the Water unless otherwise impeded, must necessarily move downward in [Page 203] all positions, though sometimes it hath an accidental or consequential motion upwards; and by reason of its fluidity, a lateral motion: therefore I confess I am to seek what is meant, when it is said that the Nisus of Water down­ward is occasional, and pro re nata as well as upward, namely when it is out of its place.


I Answer to the Demand, the Mo­bility of the Water downward, is natural, being thereunto, as a heavy Body, determined by the Principle thereof, viz. intrinsick Gravity, but the other Motions are either from its fluidity, or occasional.

Though it be not pertinent to the Debate, yet it is plain that at the same time Water may have an occasional [Page 204] motion upward or laterally, and yet a natural motion downward. The Buc­ket of Water weighing 12 pound, will weigh as much when a Tube stopped below and immersed, and then opened below, gives an occasional motion to part of the Water upward into the Tube. And the same is apparent when it drives up a light Rundle of Wood from the Base to the Superficies.

The rest of the Remark is princi­pally levelled against Continuity of Water; the contrary whereof is here affirmed to be proved in the former Remarks. Indeed I find this often said, but without any proof that I can find. And indeed it requires a very evident proof; for its Continuity is affirmed by all others that I know of, and is evident to some.

Concerning the motion and pressure of Sand, I have said enough; only where it is said, that an Animal is not damnified under a high heap of Sand, may have some such reason as the su­spension of Fluids; I freely agree herein; for, as I take it, the Animal [Page 205] is protected in both by the Mecha­nism of the incumbent parts, but not by such Hylarchical Principle as the Au­thor supposeth.


THat the natural gravitation down­ward, is not inconsistent with an occasional gravitation lateral; yea, and in some cases vertical, is most evi­dent by what hath been said upon the last Remark: And therefore those other actual gravitations are not bare imagi­nations, but may be as real effects in Nature; as when a Bullet is shot out of a Gun in a horizontal Line, at the same time there is a conatus ad motum Horizontalem & Centralem (for other­wise the Bullet could never sink from a straight Line) the former is conatus ad motum violentum, and the latter ad motum naturalem.

But as to the distinction that I make between the fluid Water in the Buc­ket [Page 206] and the Bucket, containing an en­tire Cylinder, constituted both of the Bucket and Water in it, and that the latter hath one simple motion down­ward, as a heavy Body, or as a Keg of Ice; but the fluid water in the Bucket, had as a fluid Body, those various motions, which in this Chap­ter I assign unto it. I must confess, when I wrote it, I thought, and still think it so plain, and intelligible, and evident, that I wonder it should not be understood, or should be thought a repugnancy in Nature.

The Water in the Bucket is per­fectly a fluid Body, and hath its per­pendicular motion downward; which is simply natural to it as a heavy Body, and its lateral motion belonging to it, as a fluid Body; by which it would drive out the sides of the Bucket, near the top, especially, were it not well fenced; and though by the strong gards of the Bucket, it be kept in, that it cannot effect what it endeavours; yet it hath still its conatus ad motum lateralem; but that conatus is still kept [Page 207] in by the strong sides and bottom of the Bucket.

But the Bucket of Water is now one entire aggregate Body consisting of Wood formed into a Cylindraceous form, and Water contained within it, and so presseth simply centrally, as if the Water were congealed into Ice; or as if Water and Earth were min­gled together into one solid Mass, in which Instances the Bucket of Water presseth not as a fluid Body of Water, but as a common solid aggregate Body.

And now if you ask, But why doth not the Bucket of Water press laterally as well as the Water in the Bucket? The Answer offers it self, even before the Question asked; be­cause the sides of the Bucket are solid, and not fluid, and can no more press laterally upon the circumjacent Air, than if they were empty of Water; the Water within the Bucket presseth up­on the interior sides and cavity of the Bucket, but is restrained from pressing farther by the contignation of the [Page 208] Bucket, but the convexity of the sides of the Bucket do not, cannot press upon the ambient Air; and so the whole weight is discharged from it in a central direction, as in truth it doth alwayes in a solid Body.

And the consequence that would be drawn from hence, that then Water congealed should be heavier than the same Water solute, is the vainest in­ference imaginable; for the Water as one common Body, had the same, and possibly a little more weight before its congealing, than after; and though its congealing hinder the various moti­ons of it as a fluid Body, it doth not encrease nor considerably impair its weight upon the Scale as a heavy Body.

Methinks the Reasoning of the Re­marker in this Case, is just as if a ship were sayling from North to South, a man should say it were unconcepti­ble that a Passenger should walk up­on the Deck from South to North; for then he should be moved with two contrary motions, and of con­trary [Page 209] terminations at the same time, and yet is apparently true, that at the same time he is moved ad motum Navis, from North to South, and ad motum proprium, from South to North: so the same Vessel of water, as it is one entire heavy bulk, hath simply its cen­tral termination; yet the several in­cluded fluid parts in their fluid consi­stence, have and may have various ter­minations, as well lateral or incli­ning, as perpendicular or central.

But to put a period to this Debate, when I speak of the various motions of fluids as fluids, I speak of the mo­tions of the parts of that common bo­dy which is fluid, and those are hori­zontal, per declive, lateral and central. But when I speak of its motion as one common body, then it is true the mo­tion is central, which is its motion of natural gravitation upon the Scale; and therefore 12 pound of water with­out relation to the Vessel wherein it is, will weigh still 12 pound upon the Scale, and yet its parts have those se­veral motions before described, which [Page 210] abate not the weight of the whole Mass, but correct the particular pres­sures of it, and the several parts there­of while in fluore.

And by way of illustration of what I say, take these few Instances; a Barrel of new Wine or Beer, suppose it weigh 100 pound, after a little time, it will gain a motion of fermen­tation; which by reason it proceeds from heat, is principally upward, to­wards the Superficies, yet notwithstan­ding this motion, the Barrel of Beer or Wine, will as a heavy body, weigh as much as before the excitation of tha [...] motion, unless some of the Liquor b [...] spent at a vent, or break the Barrel.

In Animals there is a great variety of the motions, not only of the Spi­rits, but of the Blood, the Chyle, the Lympha, and most considerably up­ward towards the Head and superio [...] parts of the Body, whereupon it wa [...] supposed by some Learned men, tha [...] the Body of a dead Animal that by such death had lost none of his blood should weigh more than the same body [Page 211] living; but upon strict trials it hath been found that the weight continues the same upon the Scale; so that the various motions of the Blood, Hu­mors, Chyle and Lympha, which are of a different, yea, and in many re­spects, of a contrary termination to that of natural gravity, doth not on­ly consist with the proper motion of gravity of the whole Moles Corporea, but doth not so much as abate it; yet these particular partial motions of the Blood, Humors, Chyle and Latex, may one correct the other.

And the same I say of Water; though there be particular motions of its parts, as a fluid body, and those correct and refract one another; yet the motion of the entire Moles Corpo­rea, as constituting one entire body, retains its entire weight upon the Scale, viz. 12 pound, and this with­out any repugnancy to, or diminution of the Laws of Nature, in relation to the descent of heavy bodies to the Center.

Take a Ballance, and charge one [Page 212] Scale with 3 pound weight, the other with 2 pound weight, the preponde­ration of the Scale with 3 pound weight, will raise up the Scale with 2 pound weight, so that in a relative consideration between the weights, the latter hath no sensible gravitation, and yet the hand that holds the Bal­lance, will sustain and feel in both Scales together the weight of 5 pound; and it were an unreasonable way of ar­gumentation to urge, that because the lighter weight hath lost its actual gra­vitation in relation to the heavier weight, therefore the weight of both should be but 3 pound, which is the preponderating weight of the heavier Scale.

If there be a triangular body made of Boards, Latin, or any other like Matter, whose Basis A B, is parallel to the Horizon, and the Cathet B C, perpendicular to it, and 3 foot high, the subtense C A, 6 foot long, as in the Figure following, which is dou­ble the length of the perpendicular, it is demonstrable that a weight E, [Page 213]


of 2 pound weight, will counter­poise the weight D, of 4 pound weight, and that as the distance C A, is to the distance C B, so the momentum of the weight E, is to the momentum of the weight D. The moment of the weight therefore in the perpendicular descent C B, will be double to the moment of the same weight upon the declive sub­tense Line A C. That which I would observe in this Instance, is this.

1. That notwithstanding this aequi­pondium in this Instance between the 2 pound and 4 pound, whereby the re­lative weight of each is abated, yet the entire Engin with its weights, will weigh 6 pound besides the weight of the Engin.

[Page 214]2. That by the declivity of the mo­tion of D, it loseth half of that weight that it would have in a direct descent from C to B; and so this accidental interposition of a motion per declive, corrects that natural gravitation that is truly central and perpendicu­lar.

3. But yet it doth not wholly re­move or take it away, only the de­clive termination or direction takes off one half of the actual perpendicular or central gravitation. And this In­stance explicates, and in a great mea­sure proves what I have said, and e­vinceth that these 29, 30 Remarks are not of that moment as the Remar­ker takes them to be.

So that upon the whole Matter, though a Tun of Water in a Vessel, weigh 2000 pound weight, and that a man being laid upon his back in the bottom of that Vessel, be subjected to a Pile or Column of Water, equal in Base to the half of that Tun of Water, yet the man shall not be pressed with 1000 pound weight of Water, nor the [Page 215] 1000th part thereof; and yet the whole Vessel of Water, or the whole water in the Vessel, shall nevertheless weigh 2000 pound, upon the Reasons given in the 7th and 8th Chapters of the Essay, without the help of an Hy­larchical Spirit, whether intelligent, sentient, or plastick only.

And thus I have done with the Re­marks upon the Pamphlet, called, An ESSAY touching the Gravitation of Flu­ids: The Brief of what I have here­in and there delivered, are as follow­eth.

I. That there seems to me a double Reason of the Non-gravitation of Flu­ids upon Bodies within them of a nar­rower Base at least, than the Base of the whole Moles of the Water incum­bent upon them; namely,

1. Mechanical, which is principally sustinendo; the inferior parts of the Water sustaining and bearing up the superior, as analogical to the sustenta­tion of the superior parts of Sands or other minute Bodies by the infe­rior.

[Page 216]2. Natural, premendo; which is the motion of the parts of Water it self, as a fluid, though withal a heavy Bo­dy; which being per declive, and ve­ry near horizontal, corrects the cen­tral gravitation.

II. That although the Moles of Water, considered as one common Mass or Moles, moves as a heavy Bo­dy, in a central termination, yet the Water and its parts considered in their fluid consistency, have differing mo­tions, as a fluid body, and with vari­ous terminations, viz. central, lateral, and per declive, which check and re­fract the pressure of each other; so that the entire pressure of the parts of wa­ter is not all one way, because a fluid Body, though as one entire Moles, it press with one single central termina­tion as a heavy body, yet the parts thereof in their common consistency, have various motions or Conatus ad mo­tum.

III. That although the various Co­natus ad motum of the parts of water in fluore, do correct the motions of wa­ter, [Page 217] in relation to their terminations, as a fluid body, whereby Divers (Uri­natores) are not pressed to death, yet these motions of its parts, as a fluid body, do not abate or alter the com­mon motion of the whole Moles, when in one collection, in its central termi­nation, as a heavy body.

IV. That besides these motions inci­dent to Water, as a heavy or a fluid body, there are or may be certain ac­cidental motions ab extrinseco, which may give water a vertical ascending motion of pressure, by an external force, as that motion which ariseth by circumpulsion, where it meets with a lighter body below the Superfi­cies, as in that of the Rundle of a ligh­ter body, as a Rundle of Wood, the rising up of Water into a Tube full of Air, the instance of the value given in the ensuing Remarks; all which, though they partly happen from the fluidity of water, yet they are effected from an accidental interposition, and most ordinarily are consequential up­on a descent of the Water first, all [Page 218] which motions of parts of fluids ari­sing either ab extrinseco, or from its fluidity, yet are consistent with its in­trinsecal quality of a heavy body, and the motion or Conatus ad motum of the entire Moles thereof in a central termi­nation or motion towards the Center, which I usually express by a central motion or termination.

Touching the REMARKS upon Difficiles Nugae.


I Now come to the Second Course of Remarks upon Difficiles Nugae, and begin with the first.

In this Remark the Learned Author hath fallen upon one of the subtillest Subjects in Philosophy, and such as would require more than a small Treatise to give a tolerable accompt touching it, namely, Rarefaction and Condensation.

I have more largely given an ac­count of my thoughts touching it, in the beginning of this Book; where­by it will appear whether the Princi­ples I take up, are unproved; or whe­ther they or the Remarkers Principles be, or can be proved by any Experi­ment [Page 220] or Reason in Nature, or whe­ther his Principles or mine are such as are repugnant to Reason, and absurd, if we closely canvass them, and more considerately search into them.

It was not in that place here remar­ked upon, necessary to prove them, but to suppose them; the proof was therefore there omitted: I having therefore now in the beginning sup­plied that defect in some measure.


THe Learned Remarker mistakes the Scope of the Assertion; it is true that the conjunction of solid heavy bodies contribute to their weight, and consequently to the moti­on of the whole solid body downward. But the actual gravitation of one part upon another, is suspended by their continuity, the lower parts receiving, and sustaining, and so de facto suspen­ding the actual gravitation of the up­per parts upon the lower; so that al­though the superior parts contribute to the total weight, yet they do not superately and actually gravitate upon the lower parts.


I Must confess the substiturion of an Hylarchical Principle to perform all the Phaenomena of motions in Natural Bodies, is a compendious and easie way for the answering of all difficul­ties: But he that but observes the In­stance here endeavoured to be confu­ted, will find (as in many others, that I shall hereafter mention) they do not stand in need of such a help; for it is meerly Mechanical, from the various Librations of the Water and Oyl, at various immersions, by a kind of in­verted natural Ballance between the Water and Oyl in these various posi­tions; therefore I shall refer the truth of the Solution to the Readers trial, and what hath been before said upon the former Remarks.


IT is cautiously said, that (in a manner) I acknowledge what is endeavoured to be proved in the first Remark: For in the Atmosphear the Air is more compounded than above it; and yet all are connexed together by continuity, and so, in a manner, I do not acknowledge it also. Touch­ing the continuity of the Air, it is said by the Author to be sufficiently disproved; but it is only said so: And I think the continuity of the Air is sufficiently proved, and in it self most evident, if no proof were of­fered of it.


THe exclusion of innate Gravity, because the parts compressed will sensibly gravitate, but do not sensibly gravitate before compression, seems to me as strange a consequence, as if a man should say, a Feather hath no sensible gravitation, but a peck of Feathers put together, have a sensible gravitation; therefore there is no such thing as intrinsick gravity in the Feather.


ANd I have before noted, that Continuity consists not in the facility or difficulty of separation of parts, which yet till such separation, are in continuity, and when that se­paration is past, may grow together into continuity again, by the first con­tact of the separated parts, as the Air and Water do upon removing of what separates their parts.


IN the 4th Chapter, pag. 64. of the Nugae, I have given an account touching the various pressure of solute and included water; namely, that in a Siphon there described, the Water in the open Air poured into the longer Leg, being 24 inches, depressed the [Page 226] Mercury 2 inches and ¼, and drove it out of the short Leg; but the solute water in an open Tube incumbent up­on the shorter Leg, drove back only one inch, the longer Leg being em­pty: Now if the impelling down of 2 inches and ¼ of Mercury by the 24 inches of Water in the longer Leg, be no more than the pressing down of one inch of Mercury, by the solute Water of 24 inches deep in the shorter Leg, the Remarker is in the right, and I was in the wrong; but if these be differing pressures, and the pres­sing down of one inch of the Mer­cury by the solute Water leaning upon the short Leg, be less than the pressing of two inches and ¼ by the 24 inches of Water included in the longer Leg, then I was not mistaken; and a little Arithmetick will serve to disco­ver it.

The Remark gives this Answer to this part of the Experiment, That more was impelled up by the solute Water, because the shorter Leg was wider, and so required more Mercury [Page 272] in the other Leg to counterpoise it.

But to give the Remark satisfaction herein, I have made a most exact scru­tiny into this part of the Expe­riment; and to the Objection I give these Answers.

1. The Cavity of the Siphon in the shorter Leg was ⅛ parts of an inch, or ¼ of half an inch, the breadth of the Cavity of the longer Leg was not the 40th part of an inch less than the shorter, which is so small a dispro­portion that it could scarce be sensible, and this upon an exact admeasure­ment: And again, when the Mercury in the shorter tube was depressed an inch by the solute Water incumbent upon it, there was not any visible dif­ference between the extent of the Mer­cury driven up in the longer, and de­pressed in the shorter Leg, both being indistinguishably the same, viz. an inch subsiding in the shorter, and an inch only rising in the longer Leg, which evidenceth the imperceptibleness of the difference.

[Page 228]2. If it gave an advantage of rai­sing of the Mercury, it must be to the shorter Leg, because it had a grea­ter Moles of Mercury in it, and of Wa­ter upon it.

3. But the truth is, the pressure of Water or Mercury in an inverted Si­phon, is equal, though the amplitude of the Legs differ; for Fluids in that Instance, press secundum altitudinem or longitudinem, not secundum amplitudi­nem. A Siphon inverted, having one Leg of 6 inches diameter, and the other but of an inch diameter, filled with Water or Mercury, will have their Superficies of equal heights, not­withstanding the disproportion of their amplitude.

This part of the Experiment there­fore stands unshaken by the Remark, and therefore surely the Experiment it self, nor the Collection thereupon made by the Remark, gives little coun­tenance to the magnified demonstra­tion mentioned in the Remark, but con­cludes effectually against it.

Indeed as to the second Instance or [Page 229] Trial, which I call the double Trial, pag. 66. it hath reasonably given a just cause of exception, yet not without some Mistake in the Remark, because it was tried when two inches and more of the Mercury was first driven out of the Siphon, by the Water poured into the longer Leg, and therefore I lay no weight upon it; yet even there, there is a disparity in the pressure of the so­lute and enclosed water, there being a greater height of water pressing up­on the Mercury in the shorter Leg than in the longer: But because this second trial is less evident, I lay it aside; yet howsoever this doth not impeach the former trial, nor the Conclusion which I lay upon it, viz. that the force of the same Column of water contra­cted in the longer Leg of the Siphon, and having no other Base but the Mer­cury it self, is of greater force than the like Column of solute Water in the open Vessel impending upon the shor­ter Leg, especially since in the one case and the other, the open Air gives the most fair trial to the energy of both: [Page 230] and therefore the disparity of the pres­sure of enclosed and solute water, which the Remarker is pleasantly di­sposed to call the Masonry of the water, is not hereby impeach­ed, nor the notable demonstra­tion in the Enchiridion Metaphysicum, by the Rundle of wood any way re­lieved.

And for evidence of the truth of the pressure of water secundum altitudinem, and not secundum amplitudinem, and al­so the disparity of pressure of solute water, and water under a constriction to a narrow Basis, I have observed that if a Tube of half an inch diameter, and 4 foot high, with a Lumen of a quarter of an inch diameter in the side near the Base, be filled with water, the parabolical Line that the water will make out of that Vessel in its first exsilition, will be as long, yea, and somewhat longer than the like parabo­lical Line made in the first exsilition, by the like Lumen out of a Vessel of six inches diameter, and the same height, which must needs proceed from the [Page 231] greater pressure by that Column of water that hath an equal height, but a Base of more equality to the Lumen, according to the subjoined Figure.



THe true reason of the rising of the Rundle of wood is neither from the Spirit of Nature, nor from an Hy­larchical Principle, but from the plain common known Rules of Hydrostaticks, whereby necessarily a fluid Body drives up a solid Body lighter than it self, to the Superficies, if it can by any means in the least proportion, insinuate it self between the Rundle and the Base of the Vessel, and this is done by cir­cumpulsion.

But as touching Stevinus his Expe­riment of the Rundle covering a per­tuse or hole in the Basis of the Vessel, I must needs say, Stevinus delivers it in his Observations upon the 10th. Pro­position of his Hydrostatiques, from whence I transcribe it, pag. 94. of the Nugae.

I have said enough touching this Business before upon Remark 19, 20. [Page 233] upon the Essay; I shall therefore short­ly collect somewhat of what is there more fully delivered.

If the Rundle of Wood be specifi­cally lighter than a portion of water equal to its Moles, and the Rundle be pressed down as contiguous as may be to the plain Basis of the Vessel, yet it will rise; for by reason of the porosi­ties and chamfers of the wood, all the industry imaginable will not press it so close, but there will be some inter­stitia between the Rundle and the Ba­sis or bottom of the Vessel into which the Water will creep, and so under­mine and drive up the Rundle to the Superficies of the Water, by an ascen­ding pressure of the Water, which ascending pressure is nevertheless wrought and effected first by a descent of the water round the sides of the Rundle, and so by a kind of Ballance, overweighing the Rundle of wood, and thereupon necessarily weighing it up.

2. If the Rundle be closely fixed to the bottom by a viscous, or gluti­nous, [Page 234] or thick Oylie matter, that the water cannot get under it, the Run­dle will not rise, upon this double ac­count.

1. Because that adhering Oyl by the mutual adhesion to the Rundle and Base, renders the Rundle consequen­tially, and effectively, and extrinsecal­ly heavier by its adhesion, than the like Moles of Water, whereby the Wa­ter cannot raise it.

But, 2. and principally, Because the interposed viscous Oyl doth obstruct the migration or insinuation of the Water between the Rundle and Basis or bottom of the Vessel, and so it can­not get under it to drive it up; but stands now as one common fixed Base of the Vessel united to the true Base thereof,

3. If there be a hole in the bottom of the Vessel, suppose of two inches diameter, and the Rundle of light wood be 4 inches diameter, and so overlap the Orifice, the Rundle will not rise, because the Water, notwith­standing all the care imaginable, will [Page 235] creep under the sides of the Rundle, and discharge it self gradually through the hole; for the water having never so little passage through the pertuse or hole, though not commensurate to the 40th. part of its amplitude, will con­tend and press that way, and so gravi­tate upon the Rundle that lies in its way, by its Conatus ad motum to that Orifice, where it finds never so little vent that it may discharge it self; for the water pressing upon and through the Orifice, doth necessarily press up­on the interposed Rundle.

4. And if the Rundle of wood could be kept so close to the bottom, either by its own exquisite smoothness (which is hardly possible) or by any viscous Oyl, or by any fixation to the bottom or Base of the Vessel, now it stands as one common Base to the water, as the rest of the bottom of the Vessel doth, and is of no use to explicate the Phaenomenon; for it is all one as if it were one continued solid Base to the Vessel, unmoved and unmoveable by the water.

[Page 236]And this upon more than one trial, I find true; and when duly weighed, it makes nothing in favour of the Remarkers Hypothesis, or to the disad­vantage of my Supposition in the Es­say, though I confess it doth more di­stinctly and clearly explicate the Phae­nomenon.


THe adequate Reason is truly gi­ven by me, if the Glass were excessively strong, or if it were filled with water, it would not break, be­cause the internal water bears as strongly against the external pressure of the external water, as that can downward against it.

As we see in making new Cuts and Rivers; if there be a River with a small or weak bank on its South side, and another Cut of Water be made on the South side of that slender Bank, the water in the River will not break [Page 237] the Bank; for the adjacent Cut filled with water, strengthens the Bank by its renitence; but if the Cutt be emp­ty of water, the Bank of the River will break, because the conterminous Air is not of strength enough to bal­ance it. The sides of the Glass-Bot­tles of themselves being too weak to protect them, and the included Air ca­pable of compression by the heavier Element of water, it wants strength to protect it, and so breaks.

But as for the Air being out of its place when under water, I have ob­served enough before of the vanity of that Reason, and the ensuing Remarks will give me occasion to re-inforce it.


IF the Remarker had been pleased to take notice of what is so often men­tioned in both the Tracts upon which he remarks, and is of infallible truth, that the pressure of water in this In­stance and divers others, is never se­cundum amplitudinem, but secundum al­titudinem: Much of this Remark might have been spared, and the censure of absurdity would have been reserved to better purpose; for the water in the Pipe of one quarter of an inch diame­ter, must be counterpoised with a Cy­linder of external water, of equal height and length to that in the Tube. And if the height be less, though the amplitude of the Water be more, it will not counterpoise it in this motion.


I Come to the Instance which I call the Valve, he calls the Obturacu­lum.

I have given my reason of that Phae­nomenon, why the Obturaculum will not subside in such an immersion into wa­ter; this is the Subject of Cap. 6. Nu­garum, pag. 102, &c. and in the Ob­servation upon the Remark; which is this in effect.

When the whole Tube with its Valve closed, is counterpoised with a portion of water of greater, or at least, equal weight to the whole in­strument, and of equal Bulk to so much thereof as is immersed in the water, the whole Engin must necessarily swim; for it is in aequilibrio with, or preponderated by so much water, which it displaceth by its immersion. And it is in effect no other, than if a Cylindrical Body, suppose a Cane, [Page 240] were of two inches diameter, and of two foot long, the bottom filled about an inch with Lead, and then 11 inches with Water, and the rest with Air, and suppose the whole Cane were lighter than the like Bulk of Water, so that a Moles of water countervail­ing 12 inches of this Cylinder, would counterpoise it, it is absolutely neces­sary that this Cylinder must swim perpendiculary and erect in the water at an immersion of twelve inches; for the water bearing against its Basis, must necessarily sustain it at that height.

And perfectly the same reason is that which keeps up the Obturaculum, by pressing against it at the bottom; which now is as it were one com­mon piece of the whole Latin Cy­linder or Valve; And this aequilibrium is the true Cause of its sustenta­tion.

But the Remarker hath given us another kind of Solution; which if I understand aright, is to this purpose, that in this Instance the Air is out of [Page 241] its place being in the Latin Cube be­low the Superficies of the Water, and that the Spirit of Nature, or the Prin­cipium Hylarchicum, to rescue it from this inconvenience, draws up the Air, and drives down the contiguous wa­ter, and therewith draws and drives up the Obturaculum, which by the Abituriency (as it is called) of the Air, is sustained: And as a strong proof hereof, it is said both in the Re­mark, and in the Enchiridion Metaphy­sicum, that if the Tube be stopped near the Sucker or Obturaculum, it will by no means be sustained; because now the Obturaculum is not concerned in the abiturience of the Air thus se­parated from it by the interposed ob­struction.

This I call an obscure Solution; and had I then searched into it, as I have done since, I should have stiled it a mistaken Solution; for so it is.

1. I do not understand how the Air is out of its place, when it fills the Tube below the Superficies of the Wa­ter, any more than if the Vessel were [Page 242] placed upon a Steeple, the Air on ei­ther side reaching below the fund of the Vessel, it may be 40 yards, were out of his place, because the Bucket of Water stands above it.

2. Neither do I understand how the Spirit of Nature is concerned to fetch up the Air out of the Tube, or to bring the water into the Tube; but it is performed by a plain statical ne­cessity, and the relative pressure of the Water upon the Basis of the Tube, being lighter than the like Moles of Water.

3. Be it in his place, or out of his place; if the instance given by the Remarker of the falling off of the Valve or Obturaculum, when another Obtura­culum is interposed, were as true as it is confidently affirmed, there might have some relief thereby been given to the Solution, which I called ob­scure: But most plainly it is not true; and by frequent trials I have found that notwithstanding that interposed stopping a little above the Sucker, or Obturaculum, the Obturaculum will con­tinue [Page 243] suspended as well as if there were no such interposed stoppage. I took a Latin Tube of two foot five inches long, and one inch and a quar­ter diameter, with its Valve and Obtu­raculum closely fitted each to other, but so as with its own weight the Obtura­culum would subside in the open Air, the weight of the whole Engin weigh­ed 12 ounces and a half and 9d weight.

I stopped the Tube within less than ah inch above the Obturaculum with Cork, so every way encompassed with a strong Cement, that all possible in­tercourse between the superior Air and the lower brazen Obturaculum was en­tirely stopped.

The Valve or Obturaculum being put up, and the Tube immersed into a full Vessel of Water, subsided to 18 inches depth, and thereby drave over a por­tion of Water equal in weight to the weight of the Engin, and equal in Bulk or Moles to the 18 inches of the Engin immersed in the Water; and all this while the Obturaculum stuck fast; I therefore gently raised the En­gin [Page 244] till it came within 5 or 6 inches of the Superficies of the Water, and yet it continued sustained till it was raised to such a height as the weight of the Obturaculum counterpoised a Column of Water commensurate in weight unto it, and so long the Obtu­raculum continued suspended; but when the Tube was lifted higher, so that the aequipondium between the Ob­turaculum and the like Moles of Water was lost, then the Obturaculum fell down, as in the instance of the Valve, that had no such interposed obstru­ction.

This was the event of this Experi­ment often made, and will doubtless fall out upon any other mans Trial, if it be carefully and soberly put in ure.

Only this must be remembred, if the Obturaculum be not very true and exact, but that the water comes in considerably between the Obturaculum and the Valve, the Obturaculum will fall off after a little while at least, as well in this, as in the unstopped Tube [Page 245] described in the Fifth Chapter of the Nugae, partly by reason of the laxness of its adhesion, and partly by reason of the additional weight of water get­ting in above the lower Obturacu­lum.

And yet it must be remembred also, that though there be the greatest care imaginable used, if the Obturaculum be so lax as to fall from the Valve in the open Air, though it be so close as to stick together in the Water, the Wa­ter will creep between the Fissures of the Obturaculum and the Valve, with a force, if it have any room to re­ceive it. And whether even that ve­ry pressure of the water upwards through that Fissure, may for a while contribute to the bearing up of the Valve (as in the instance of the Rundles of Wood covering the Orifice in the Base, it contributes to the keeping down of the Rundle) may be considerable. But howsoever, if it receive too much water, it pres­seth the Obturaculum the more down­ward, [Page 246] and thereby in time weakens the adhesion thereof.

And now what part hath this Spi­ritus Naturae to act in this case?

I shall therefore conclude this Re­mark upon which so great a stress is laid to prove the Hylarchical Principle, and the manner of its sustaining the Obturaculum, by evocating the Air, and its ready obsequious abituriency, to be not so much an obscure, as a mi­staken Solution, and bottomed upon a mistaken Experiment.


IN this Remark, the Author is plea­sant with his Hylarchical Principle, attributing to it a pretty kind of Intel­ligence, only where he sayes, that it is the Pulp, not the Skin of the Finger that feels the monition of the Hylar­chical Principle; it is certainly both; for the Pulp cannot be attracted, un­less the intervening Skin be attra­cted.

The 15th. Remark will come to be considered hereafter.


EXception is taken because I say, re­gularly bodily effects are wrought by contact of some active body upon the Patient: The Remarker might, if he had pleased, have taken notice that I often say, In bodily motions some things act from an inward active prin­ciple inherent in them, as the descent of heavy Bodies. Other things there are that are moved by an external or fo­reign active principle, or at least, some other body put into motion, as in a Clock, the descent of the weight of Lead is ab intrinseco principio, and not by any contact, but the turning about of the Wheels of the Clock, is by the connexion of the Line to the weight, and its circumvolution about the wheel per contactum. To the for­mer I never apply this Axiom, as he calls it, as he himself after in his 37th [Page 249] Remark fairly confesseth. This active intrinsick principle I call the Law of Nature alligated to heavy bodies; and if he had called it an Hylarchical Prin­ciple, I should not have contended with him about the word: But in these motions ab extrinseco, I dare think at least, he will not deny it to be regular­ly true.


THere is no great matter in these, but only touching the porosity of Glass; and the difficulty of the transition of the Materia Subtilis through it, by the renitence of the Air; upon which little more need to be said than what occurs before.

Only where the Remarker subjoynes that upon the gentle gradual incli­ning of the Tube of Mercury, yet when it comes to an erect posture the Mercury subsides to 29 inches, is an [Page 250] Argument that there are no such efflu­via from the Mercury, to supply the derelicted space in the top of the Tube. This, though often repeated by him in the subsequent Remarks, seems to be no Objection; for whether the sub­siding be more gradual, or more sud­den, the compression of the Mercurial parts, and traction upon them, are equal when it attains its perpendicular pressure; as to use my old comparison, if a man strain a Lute-string from a lower to a higher Note, suppose from an Eighth to a Third, if he do it ra­pidly, he shall indeed endanger the Lute-string; but whether it be wound up swifter or slower, the tension of the Lute-string is the same at an equal height, in both motions of the Pin: Indeed while the inclination con­tinues, the pressure and gravitation of the Mercury upon it self, is less, and consequently the tension weaker; and therefore the portions of Effluvia sent or drawn out in that posture, are less; but when it comes to an erect perpen­dicular posture, the pressure and gra­vitation, [Page 251] and traction and tension is e­qual, whether that posture be attained suddenly or more leisurely.

As to the length of the Tube, or its capacity in the top to receive more Mercury, as I have made the Objection; so the Answer that I give, that the more Mercury descends, the more efflu­via are emitted, seems to me a suffici­ent Answer, whether the Tube be lei­surely or suddenly brought to a verti­cal posture.


THere is in these Remarks no dif­ference between us; for it seems I write herein according to his Sense; only in the Solution by me given by Tension, and Rarefaction, and Attra­ction thereby wrought, It agrees not to his Judgment, as contradicting the instance of the sustaining of the Embolus of the Air-pump, upon which the Enchiridion layes great stress to prove an Hylarchical Principle; there­fore most of the ensuing Remarks are levelled against that Solution.


TOuching the various position of the Mercury upon the top and bottom of a Hill, I need not say more than what is said in my 14th Chapter of the Nugae, and therefore I spare repetition. Touching the rea­son assigned by the Remark of the swel­ling of a Bladder, and the raising of Bubbles out of Water and Spirit of Wine in the Air-pump, by me attri­buted to Tension and Attraction, thereby wrought; but by the Remar­ker to a tumultuary agitation of the parts of Water, &c. As he is little sa­tisfied with my explication, so I am as little satisfied with his; both indeed produce an agitation of the Water in the Glass; but that which I assign, is regular, orderly and sutable to the effect produced; but the tumultuary [Page 254] agitation of the Remarker, is confused, irregular, and unproductive of such regular motion; and besides, is un­evident, and contradicted by Phaenome­na of like nature; as we shall see plainly in the Magdeburgh Hemi­spheres.

The Ludicrous Instance, as I call it, of the Attraction of Tobacco through Water, is properly brought in by me in this place, to shew that in many Instances, Attraction may be made through Water, which was seasonable in that place, and proper enough.


IN these two Remarks the Remarker endeavours to shew,

1. The Groundlessness of the Solu­tion offered by me to the Torricellian Phaenomena. And, 2. Its Repug­nancy.

The former he saith he hath shewn in Remark 32. But all that is done to shew it, is to substitute certain inevi­dent, and I think, mistaken Supposi­tions: As,

1. The perviousness of Glass to the subtiler aerial particles; this indeed he hath often said, but no where pro­ved; and if it were admitted, would not only perfectly destroy the appa­rent Phaenomena in that Instrument, but would utterly confound his Answer to the resiliency of the Mercury upon a sudden lifting up and separation of the Tube from the restagnant Mercu­ry: For what need such a violent [Page 256] resilition where the top of the Tube admits the subtiler aerial particles to pervade the Glass?

2. The gentle inclining of the Tube to prevent the tumultuary agi­tation of the Mercury. But what I have shewn in my Observation upon Remark 17, &c. I think sufficiently discovers the impotence of this Ob­jection.

3. The gravitation upward by a Circle of motion, is utterly unapt to salve the resilition; for that circulation can be but a slow, gentle motion, and cannot possibly have so rapid a motion by the imaginary straightness of the Channel; as we may suppose in the Streights in the Sea; upon which the Ocean presseth; but this neither can nor need receive a greater portion of subtil Air to relieve it than possibly 2 inches in height, and the 8th part of an inch in Diameter, where the amplitude of the Tube is no grea­ter.

As to the Second, namely, the re­pugnancy which is assigned.

[Page 257]1. In that I deny a Vacuum, which he saith cannot be by another way pre­vented, but by the transition of the subtil particles of Air through the Glass; but such a course of argumen­tation seems to be of kin to that which is called Petitio Principii, he knows I assign another cause, though he di­spute the truth of it. Then he pro­ceeds to the leisurely inclining of the Tube; which I confess is often repeat­ed, but I think need not be more than once answered, which I think is done in my Observations upon Remark 17, &c.

Then he proceeds to the Argument touching Rarefaction, and the incon­venience of the penetration of dimen­sions, and so endeavours to prove re­pugnancies in what is said by a Problem that deserves more discussion than the Argument in hand, as hath been shew­ed in the beginning of this Book, wherein I have nevertheless expressed my thoughts touching it.

I cannot tell what the Remarker imagines or conceives against the co­hesion [Page 258] of grosser Bodies by the tension of lighter bodies, but I can tell what is evident to my sense, and so may any that will give his Senses leave freely to determin, without stifling them by Notions, namely, that there is as plain a cohesion in the Magdeburgh Hemi­spheres; yea, and in the Torricellian Engin, as there is between things fast­ned each to other by a string: And therefore I cannot so over-readily change the conviction of my Senses, for a Notion or Conception asserted and magnified, but not proved.

But to infer that because Water, which is above 900 times crasser than Air, is not compressible to a sensible smaller room by a great weight, there­fore a portion of subtil Matter cannot be extracted out of it or Mercury, with so small a weight as the Mercurial Cylinder, or that the effluvia of Water or Mercury, which are as subtil as Air, cannot be expanded by a less weight than Water compressed into a sensible narrower room, seem hard il­lations, and very inconsequential; for [Page 259] we see the heat of a mans hand will expand Air in Weather-Glasses to near a double extension.


I Do prove the attraction of tensed Bodies by the plain evidence of Sense, and I assign the preservation of the continuity of the Universe, as the end thereof, and the supream effi­cient cause thereof to be, the most wise and powerful Creator of all things, and the immediate effective cause, that instituted Law that he hath placed in things natural; the immediate instru­mental cause in many motions that are not primitive in their Subjects, to be from the singular disposition of the part of the Universe, & their admirable me­chanical adaptation each to other. And as to the vicarious Spirit of Nature, as a distinct incorporeal subsistence, when the Author hath given us better proofs thereof than the suspending of [Page 260] Mercury in the Torricellian Experiment, the driving up a Rundle of light wood by the Water, and potentia attractiva of the Embolus of the Air-Pump, and such like petty Instances, together with his bare Notion touching it: It may possibly obtain a better entertain­ment than yet I find it doth, at least with me.


THis Instance in the Bladder and Cupping-Glasses, is passed over in this Remark very lightly, and it was necessary so to be dealt with, because too troublesome to be explicated other­wise than by Tension and Attraction, and it would require an admirable pro­cess in the Hylarchical Principle; to ef­fect this, and some proof besides single Notions and Conceptions of such ex­plication by such a principle.


THe Instance here given, hath put the Remarker to a great deal of pains to find a solution for it and the consequences of it (for the Hypothesis of Attraction is confidently said to be fully confuted, though it be only so said, but not so done.) But yet the Hy­larchical Principle is at length furnished with an Hylostatical Libration and Hy­lostatical power of union of the several parts of Water, Air and Glass: And at this rate I confess there will never want a ready solution to any difficul­ty; for it is but asserting that the Spi­rit of Nature is furnished with that ef­fectual power, and the knot is untied or cut, though there be not a Syllable of proof offered for it; but it is only graf­fed on to the Hypothesis of the Spirit of Nature by the wit of the Assertor, to accommodate the Hypothesis.


I Refer my self to what is said be­fore in the first Chapter of this Book, and upon the same Remark, there need not be said more.

The Laws of Nature were the Laws of God imprinted upon the nature of Physical Beings by his Almighty Fiat; and though as to particular Beings, he hath substituted particular active prin­ciples, usually called Essential and Vi­tal Forms; yet as to the Universe it self, it seems to be too great an Empire to be put into the vicariat hands of that which is here called the Spirit of Na­ture. The great God that gave the Laws of Nature, is sufficient without such a Substitute, and is only sufficient for the regiment of so great an Empire; and this may serve also to Remark 38. We are not disputing whether such a Spirit of Nature be possible to be, but whether de facto it be or not, or that [Page 263] it is necessary that it should be, at least as to those motions which have so evi­dent explication from other princi­ples.


HErein we differ not as to the re­jecting of the great Elasticity of the Air.


I Confess when I read the beginning of this Remark, I hoped to meet with such a Solution to the Instance remarked upon, as would be close and clear; because this Instance bears so hard against most of what the Remarker hath before affirmed; but I was de­ceived herein.

In this Instance of the Magdeburg [Page 264] Hemispheres, these things are most evi­dent to any mans Sense.

1. That the included Air is certain­ly expanded and rarefied by the heat, beyond its natural size.

2. That while they are so hot, and the Air so expanded and lax, they do not at all cohere.

3. That as they grow cold, they do most evidently cohere; so that they will not be divulsed without a consi­derable strength.

4. That most necessarily as the in­cluded Air grows cold, and the heat which was the cause of its expansion; decayes, so the Air must needs endea­vour its restitution to its natural di­mension, by contracting it self inward to its natural size.

5. And yet if it have such a degree of heat, as again gives a more lax state to the included Air, the cohesion will cease, and the Hemispheres fall asunder.

6. And as the Remarker confesseth, and the most clear evidence of Sense evinceth, those Phaenomena are not [Page 265] wrought, nor indeed possible to be wrought, either by the weight, pres­sure or elasticity of the external Air, as the Elaterists would have it.

The Consequence of all which is, that certainly as far as Sense can lead us, the Air is rarefied by the Heat; and as the Heat decayes, the Air endea­vours its own contraction, and there necessarily follows, even to our Sense, an attraction upon the sides of the He­mispheres, whereby they cohere; and that cohesion will continue till relax­ed by another accession of Heat, or ad­mission of more Air.

But now what doth the Remark pro­pound in this Instance? Marry, an Hy­lostatical Spirit, which, pro re nata, works these various Phaenomena, which is only a conjecture, and hath no evi­dence to prove it besides Notion or I­magination; but the method of the effecting it by this Hylostatical Spirit, is more admirable, though it is plea­santly offered, that thereby all goes off glibly. And it is to this effect, as I take it.

[Page 266] The Hylostatical Spirit finding the sub­tilty of Matter imprisoned in an undue place between the Hemispheres, presently makes up an occasional Gravitation or Elasticity in the ambient Air to squeeze out the included subtil Matter, and give it liberty, and thereby presseth the He­mispheres together. And so in this glib Hypothesis the Remark doth two things. viz.

1. It creates a weight or elasticity in the ambient Air pro re nata, which as it is in effect contrary to all that he hath before delivered against the weight or elasticity of the Air, so it hath this disadvantage, as is proposed by the Remark, that it is infinitely more incredible than the common Supposi­tion of the Elaterists, and indeed little less than miraculous.

And 2. It is a Conatus of this Hylo­statical Spirit to no purpose at all, and meerly frustraneous, unless by such an admirable condensation of the ambient Air it could break the brazen Ribs; whereas indeed it makes the Prison the stronger. I must confess, this Fetch [Page 267] goes not down so easily with me, nor I believe with many more.


I Come to the Remarks upon the Phae­nomena of the Glass-Pump, where­in I attribute the raising of the Water in the Glass to the traction made by the tensed Air in the Shank of the Pump, and the dilatation of the Air in the top of the Glass, by the extraction of the Water. And the reason why after ite­rated evacuations of the Water by that suction or traction, no more will rise, to be, because the Air in the Bottle hath undergone as great a tension or di­latation as a Pump of that length can give it.

These things I must observe touch­ing this Pump.

1. The length of the Shank or Pump if self above the Glass, was not much above fourteen inches, and the Embo­lus proportionable thereunto, if it had [Page 268] been longer, the attractive force must have been greater, and would proba­bly have given a stronger traction, and consequently a greater expansion, ten­sion or rarefaction to the Air in the up­per part of the Glass.

2. That in this Instance here is no misplacing of the Air or Water; upon which the Author builds much of the activity of his Hylarchical Principle in divers of his Remarks; for the Air in the Bottle, and in the Shank of the Pump, are both above the scituation of the Water in the Bottle. And here the Author, after some recourse to the impossibility of penetration of dimensi­ons, which he so often inculcates, gives us his Solution, returns to the acti­vity of the Hylostatical Principle, which because the subtil Matter misplaced, in­vigorates the external Air to do some­thing in this business, but tells us not expresly what, or how, in this place: We shall hereafter, it may be, find what is meant.

Only he tells us two things. 1. That it is impossible so heavy a Body as Wa­ter, [Page 269] should rise so high into so extream a thin Body in the Glass, and that with­out fresh Air succeeding. 2. That the Embolus that at the first pumping, over­came the consistence of the Air should as reasonably overcome it still.

As to the first, It seems he is now plea­sed to admit an intrinsick Gravity in the Water, which renders it unwilling to ascend; but besides, according to the Authors Assertion in his Remarks, the more subtil parts of the Air will pervade the Glass, if that were true, there would be supplemental subtil Air at least, to supply the evacuation of the Water to the last drop.

As to the Second, There is nothing more plain to our very Sense, than that any extendible or tensible Body till it be broken, doth more easily yield to the first attempts of its extension, which yet with more difficulty, suc­ceeds afterward as is evident in the Air-Pump and a Lute-string, which is an Instance I frequently use, I confess; but it explains my meaning; so that this Remark concludes nothing against [Page 270] what I have delivered in relation to my Glass-Pump, nor to evidence the interposition therein of the supposed Hylarchical Principle.


BEfore I come to my Observations upon these Remarks, it may be convenient to give an explication of the dimensions of the Glass-Pump that I made use of; referring my self to the Figure thereof, described in the Nugae, Fig. 21.

The whole length from the upper end of the Embolus to the bottom of the Glass-Globe, was near 21 Inches; whereof the Embolus reaching to D, near as low as H, where the Water was to be pumped out, was about 8 inches from H, to the upper Surface of the Glass, near 4 inches; from the up­per Surface of the Glass to the bottom of it, about 9 inches, which was the [Page 271] diameter of the globular Glass; the continued Pipe of the Pump being less, running into the Glass about 7 inches, and so at E, opening and end­ing about 2 inches from the bottom of the globular Glass; consequently from the lower end of the Sucker at D, to the middle of the globular Glass about 8 inches and a half or 9 inches; the cavity of the Pump it self near two inches diameter or thereabouts; so that the Air between the bottom of the Embolus and the top of the Glass, might be a Cylinder of near 2 inches diame­ter, and about 4 inches long; by the tension whereof, the Water in half the Glass is by me supposed to be attra­cted and raised. The other and up­per half of the Glass contains the other half of the Globe, and is filled with Air, which contained about 5 pints; which was more than twenty times the quantity of Air contained in the Pump, between the lower end of the Embolus and the top of the Water. I say, by iterated pumpings I drew out a quart of Water, which made the wa­ter [Page 272] subside in the lower half of the Bot­tle above an inch and an half; and con­sequently the Air in the upper half of the Bottle expanded so, that now it contained about 7 pints of Air; after which, it was not capable of a grea­ter expansion by my small Pump: The Engin it self is more punctually descri­bed in the 19th Chapter of the Nugae; but the dimensions not so fully mentio­ned there as here.

This Instance I use as an evidence to prove the attraction of the Water by the tension of that little portion of Air in the cavity of the Pump and the sequaciousness of the Water to relieve that tension, and to preserve the con­tinuity of the Mundana Materia which in these Remarks is opposed by my lear­ned Antagonist.

And the Instance is opposed upon this account, that the Air in the Glass is tended from 7 to 5; whereas the Air in the Pump is tended from 1 to 5 spaces at least, which is said, is an evi­dence that there is no such tension; for if there were, the Air in the Glass [Page 273] would receive a greater tension than from 5 to 7, when the Air in the Pump is supposed to be tended from 1 to 5, which is ever proportionate to the tension of the Air in the Glass.

But surely this is an Objection of no force, for apparent Reasons: Though the expansion of 5 to 7, is not in pro­portion the same with the expansion from 1 to 5, yet such a proportion need not, nor indeed is possible in this case; for as the Body of the Air in the Glass, is above 20 times the quantity of the Body of the Air in the Pump, so such an expansion serves its turn, as may make good the space that is left by the evacuated water, which being no more but one quart, the Air in the Glass can receive no greater ampli­tude of expansion than one quart of space more than it had before. The measure of the extension of the Air not being governed by the bare pro­portion which happens in another di­stinct portion of Air, and that of a less dimension: But by the room or space that is left by its next contiguous Bo­dy [Page 274] that must be supplied by its expan­sion.

In the 45th Remark, that which was before wanting, seems now to be supplied, viz. The method which the Hylostatical Spirit useth in raising the Water in this and in other Pumps, viz. by a circular pressure and gravi­tation of the Air and Water incum­bent upon the Superficies of the Wa­ter that the bottom of the Pump is on, which jointly gravitates upwards, in regard of that subtil Element in the top of the Tube, that there may be no bare subtil Matter in the Pump; which gravitation and circulation is carried on by the Hylostatical Principle, that there may be no misplacing of the Elements of the Universe, where­of the Materia Subtilis is one. This is the Solution in substance, and very near the words of the Learned Au­thor.

This Solution, in my understanding, is not only wonderful inevident, but also very improper.

1. Here is granted an occasional E­lasticity [Page 275] of the Air and of the Water also, though supposed to be effected by the Spirit of Nature or Principium Hy­larchicum; which Elasticity I had thought the Author would not have granted to Air, much less to Wa­ter.

2. But the Supposition of this Cir­culation encounters it self: For either the Materia Subtilis (which is sup­posed subtil enough to pervade the Glass, though the crasser parts of the Air cannot) is either a distinct Ele­ment of it self, not incorporated with the Air, but of a distinct consistence; or else is part of the aery concretion of the Air, the subtil part thereof, and mingled with the Air as one constitu­ent part thereof, though in some cases severable from it; which way so­ever we take it, the difficulties of the Authors Supposition are unanswerable. It is plain, the Air in the upper part of the Glass, upon the exsuction of a quart of Wa­ter, takes up a quart more of room or space than it had before: If this be [Page 276] caused by the perforation of the Glass by the Materia Subtilis, as a distinct Element, and so uniting it self to the Air in the Glass, then this Materia Subtilis (which in respect of its purity, must needs have its proper place ra­ther above the place of the Air, by the Laws of Nature, and not below it) is called down by the Spirit of Na­ture, from its proper position into the cavity of the Glass, and so the natu­ral Order, Position and Taxis of the parts of the Universe disordered and discomposed.

Again, if the Materia Subtilis be but a constituent part of the Air, then is the fas;ter external Air robbed of part of its constitution, and impove­rished of what naturally belongs to it, to supply the space in the Glass de­relicted by the exhausted Water, and that portion of Air in the Glass fur­nished with a greater portion of the Materia Subtilis, then belongs to it; and all this done by the Spirit of Na­ture, which is supposed to be an active plastick principle to conserve the order [Page 277] of the Universe, and not to disorder it; which according to the Learned Authors supposition, must yet be the necessary consequence of this imagi­nary transposition of the Materia Sub­tilis in this Circulation.

3. Again, in this Circulation and circular pressure, we shall find the Chain broken, and the Circulation in­terrupted, or a worse inconvenience; the Air in the Glass moves upon the Water, and that again presseth up­ward, and moves upon the subtilized Air in the Pump, and then it is thrown out in the open external Air, and so moves upon that: It remains there­fore, for the compleating of the Circle, that now at last by ther interposition of the Hylostatical Principle, the external Air must circulate by a pressure upon the Air in the upper part of the Glass, and so the Dance is finished.

But 1. We must note that even the Author himself agrees that the grosser parts of the Air cannot pervade the Glass, but it must be the Materia Sub­tilis. I demand therefore, whether [Page 278] this Materia Subtilis pervades the Glass, and is united to the Air in the top of the Glass or not?

If it do not, surely the Circle is bro­ken, and with it, the circular pressure or gravitation.

If it do pervade the Glass, and be united to the Air included in the Bot­tle, these insuperable difficulties en­sue.

1. The Hylostatical Spirit, whose Office it seems is to keep the Universe in its due Libration, and to preserve the Air it self in its just size and consi­stency of gross and subtil Matter, as is above observed; breaks that order that it is placed there to conserve; for it takes too great a proportion of sub­til Matter from the common external Air which is due to it, and crowds it into the Air in the top of the Glass, which hath already more, or at least, as much as belongs to it.

2. It would follow that by such a Current of subtil Matter through the Pores of the Glass, that the Water should rise into the Pump even to the [Page 279] last drop; for here is a perpetual spring and supply of subtil Matter, strained every where through the Glass into the Air or aery space that was in the head of the Glass, and no fear of any Va­cuum to ensue by the passing away of the Water; so that it may (to use the Authors word) as glibly pass to the last drop, as at the first, which is evi­dently contrary to experience.

This Circular Gravitation there­fore is but a supplemental Invention, to help the Flaws that arise from the Hypothesis of the Interposition of the Hylarchical Principle, as the true cause of this Phaenomenon.


I Shall not need say any thing upon this Remark; for herein we are ve­ry much agreed; and he useth me and my Book with much Civility, and is pleased to contribute his own Learned Observations in favour of it.


I Shall not spend many words touch­ing the Conclusion.

In some things therein mentioned, we very well agree; namely, in the exclusion of that prodigious Gravity and Elasticity of the Air, whereunto the late Philosophers attribute the So­lution not only of the Torricellian Ex­periment, but many other Phaenomena.

In some things we differ; he from me, in my Solution of many of the Phaenomena mentioned in my Pamplets, by Rarefaction, Condensation and Attra­ction.

I differ also from him, and the state of that difference I set down shortly thus, both in the Negative, and in the Affirmative.

1. I do not deny, but do really assure my self, there are created Spirits, some simply void of all corporeal or physical matter; others, that though possibly [Page 282] they may have a material or physical Hypostasis or Substratum; yet it is so subtil, that it may deserve the name of a spiritual being in common expres­sion.

2. I do not conclude it impossible in Nature, but that there may be such a kind of common Spirit of Nature as the Author would have, and not much unlike to Helmonts Archeus, which he puts into a middle Office between the Soul and Body, or the Colcoda of Avi­cen.

3. But yet I do say I am not satisfied that there is sufficient evidence clear­ly to evince the same; & the rather, be­cause I see no necessity for such a being, in as much as Almighty God and his intimate presence with all his Works, and the Laws that he hath alligated to the natures of things, abundantly sup­ply all the general Offices for the com­mon good and order of the Universe, deputed to this Spirit of Nature: And the particular active Forms or Princi­ples of Life or Motion, placed by the God of Nature in the several Ranks [Page 283] of Beings, supplies what is necessary for their particular motions, operati­ons and instincts.

4. That the existence of a Spirit of Nature is not at all proved by those Motions and Effects in Nature, that are either purely mechanical, or that have any other immediate cause of greater, or but as great probability as such an unseen Spirit of Nature.

5. That consequently the rising of a Rundle in the Water, or the suspension of a weight in the Embolus of an Air-Pump, the Phaenomena in the Torricel­lian Experiment, or in the Magdeburgh Hemispheres, or in Pumps or Siphons, are non only invalid Arguments to prove such an Hylarchical Spirit, but very im­proper and disadvantageous to the Sup­position it self.

6. But if there be any such Hylar­chical Spirit, the proofs thereof should be made from such things as seem to have in themselves the Principles of their own motions, or at least, no other visible or probable immediate ex­ternal cause of such their motions.

[Page 284]7. That if there be such an Hylarchi­cal Principle as is contended for, and that he doth interpose in many things that are not Automata, yet it is most reasonable to suppose that the most ex­quisite methods of Mechanism are the most probable Media whereby it per­formeth such operations.

8. That therefore the Author of the Remarks should not be too much averse to the Mechanism of those Motions in Nature, as purely inconsistent with his Hylarchical Hypothesis; for hereby he renders it less credible, by denying things that are evident to Sense, and transposing them beyond credibility, lest they should seem to prejudice his Supposition of an Hylarchical Principle. It is too much the fashion of men en­gaged in Suppositions, to run into ex­treams, and that even in this Instance of Mechanism and Mechanical Moti­ons in Natural Bodies; as I have shew­ed in the second preliminary Chapter of this Book; some attributing too much to the Mechanism of things in Nature, and some too little.

[Page 285]And it seems to me that the Learned Author of these Remarks, out of the zeal he hath for the asserting of a most certain Truth, namely, the existence of incorporeal Spirits, hath gone far­ther than was either fit or needful, in the attribution of these Phaenomena in Nature, whereof we have been deba­ting, to the immediate operation of an incorporeal vital Spirit; which he calls the Spirit of Nature; which yet are reasonably salved by the Mechanism of Bodies, and the most wise Order, In­stitution and Laws setled by the great Creator of all things, which Laws are called the Laws of Nature.


Books printed for, and to be sold by William Shrowsbury, at the Sign of the Bible in Duck-lane.

AN Essay touching the Gravitation or Non-Gravitation of Fluid Bo­dies, and the reasons thereof; in 8.

  • Stereometric, or the Art of Practical Gauging; shewing in two Parts, 1. Diverse facile and compendious ways for Gauging of [...]uns and Brew­ers Vessels, of all Forms and Figures, either in whole, or gradually from Inch to Inch, whether the Tun or Vessels Bases above and below be Ho­mogeneal, or Heterogeneal, parallel, and alike situate or not. 2. The Gau­ging of any Wine, Brandy, or Oyl-Cask; be the same assum'd as Sphae­roidal, Parabolical, Conical, or Cylin­drical, either full, or partly empty, and at any position of the Cask, or Altitude of contained Liquor; per­formed [Page] either by brief Calculation, or Instrumental Operation.
  • Together with, a Large Table of Area's of a Circles Segments, and other ne­cessary Tables, and their excellent U­tilities and Improvements; with a co­pious and methodical Index of the whole; rendring the Work perspi­cuous and intelligible to Mean Capa­cities. By John Smith, Philo-Accom­ptant: in 8.
  • Franconis Burgersdicii Idaea Philosophiae Naturalis, sive Methodus Definitionum & Controversiarum Physicarum. Editio Novissima.
  • Huc accessit Idea Oeconomicae & Politicae Doctrinae, Eodem Auctore. Opus Posthumum. 12.
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  • Spadacrene Dunelmensis; Or, A short Treatise of an ancient Medicinal [Page] Fountaln, or Vitrioline Spaw near the City of Durham.
  • Together with the Constituent Princi­ples, Virtues and Uses thereof. By E. W. Doctor in Physick.

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