CHAP. I.
The Introduction, containing the order of the ensuing Enquiries.

AMong the many Experi­ments of latter Ages, there hath been invented that Engine that commonly goes under the name of the Torricellian Experiment, which is but this: A Glass-Tube of three foot or more long, closed at one end, and then filled with Mercury or Quick­silver, and then the open end stopped with the finger, and inverted into a vessel of restagnant Mercury & and when the end is sufficiently immersed, then the finger nimbly removed so that [Page 2]no Air get in, the Mercury will subside in the Tube to the height of 29 Inches, and half an inch, or near thereabout; but infallibly between 27 and 30 Inches, leaving the residue of the upper end of the Tube emptied of the Mercury.

This Experiment, and the solution of it, hath exercised the Tryals and Wits, and Invention of very many excellent Persons, such as were Helmont, Gassen­dus, Kircherus, Shottus, Dr. Carleton, Mr. Hobbs, Mr. Sinclere, Monsieur Pec­quett, Monsieur Pascall, Magnanus, Mr. Boyle, Linus, Honeratus, Fabri, and divers others; who though men of great Learning and Industry, have run into several Parties, and given Soluti­ons, and raised Conclusions from it, extreamly contradictory the one to the other.

And although this seems but a very trifling and ludicrous Experiment, yet almost all dissenting Parties have made it to suffragate to their several precon­cerned Sentiments, and Perswasions, and that in Philosophical Points of as great moment and importance per­chance [Page 3]as most to be found in na­tural Inquiries. Some from hence con­firm themselves in their Perswasion, that there are both interspersed and coacervated Vacuities or Spaces, empty of any corporeal substance in the Uni­verse; others again as confidently con­cluding the untruth of that Opinion, and that from the same Experiment. Others again from hence confirming themselves in the Cartesian suppositi­on of his Tria Principia, and especially of that Materia Subtilis, which cannot be excluded from pervading the most contumacious and solid body: Others attributing the same Power to the more subtil parts of the aerial consistence; some from hence concluding an actual pressure and gravitation of the Air up­on all subjected bodies, and that there­by the Mercury is susteined by way of Pressure, and Trusion, and Counterpoys, and have substituted thereupon as an undoubted Hypothesis, a world of admi­rable consequences in natural appea­rances, not only in the greater World, but also in the lesser World the humane [Page 4]structure. Others again have hereupon maintained their opinion of Attraction as the necessary effect of Tension, and resolve this suspension of the Mercury unto the force of attraction and suction, occasioned by that Catholick Law of Nature for preservation of the conti­nuity of the Universe, and all its parts, and the Fuga Vacui, and are no way satis­fied with that confidence that decryes it.

From this diversity of Judgments of Learned men, we may learn, first, how little it is in natural Effects that we re­ally and truly know and understand, when so trivial an Experiment that we have so easie an access unto, and handle with our hands, and perceive by our sight its motion, which yet so gravels, or at least divides men of great Parts, Judg­ment, Learning and Experience. 2. How strangely partial men are to those Sentiments that they have once enter­tained, and perchance taken much pains to mould and fashion, or have even publickly engaged unto or for; whereby it comes to pass that men are not wil­ling [Page 5]impartially to consider what makes against their opinion, and frame a thousand imaginations to evade the strength of the opposite reasons, and to construe all appearances (as melan­cholick persons do the sound of Bells) to speak what they fancy; And possi­bly all the opposite Opinators in this business are under the like partiality and unindifferency.

There is a great odds between a Mat­ter propounded only as an Hypothesis, and propounded as a real truth. In the former there is nothing more required than a true understanding of the Phae­nomena, and a ready Wit to contrive some Model, and to dress it up so hand­somly, that it may answer the Phaeno­mena, and to fit up such expedients as may meet with and stop the Leaks that otherwise would happen in the Hypo­thesis: And such a man tells us not so much what the truth of Nature is, as what he thinks he could have made it, if he had had the handling of it; such may be the Systemes of Ptolomy, Copernicus, and Tycho Brahe, [Page 6]which cannot be possibly all true, though possibly they may be all false. And yet every of them is so fitted and accommodated by the Wit, Invention, and Industry of the Authors, that they solve the Phaenomena very near equally: And thus if I remember aright des Cartes fairly propounds his tria Principia's; and some other parts of his New Philoso­phy.

But to propound a thing as really a truth in Nature, is another kind of bu­siness, and requires not so much a dex­trous Invention, but an impartial in­spection into the things themselves, and examination how all things stand one with another, as we truely find them, and not as we mind to make them: For the Laws of Nature are stable, and setled, and regular, and not like the Laws of Men, or the fashions of our Cloaths, mutable, according to new Modes, or devices of Fancy.

Therefore the bare accommodation of Hypotheses to the Solution of the most obvious Phaenomena is not always the measure of its truth, for that may [Page 7]be but the product of Invention and Wit. For it is apparent, that though it is impossible that all the varying So­lutions of this trifling Experiment can be all true, yet they are all so dressed and pieced up, that they do solve the most obvious Phaenomena in this Experiment, well near equally each with other.

But on the other side, if any Phaeno­mena happen cleerly either in this or any other instance, that do cross and thwart that which is taken up as a necessary postulatum in any of these Solutions; it is if not an undeniable, yet a great and possibly a clear demonstration, that the Hypothesis its self is false, and ill Founded, especially if it be the great Basis upon which such Hypothesis is bottomed and built.

And if the foundation of a Hypothe­sis, or the general postulatum upon which it is bottomed, be false, or only imagi­nary, although the Inferences and Con­clusions made upon such a Basis be de­duced with all the fineness and subtilty imaginable, and such (as were the postula­tum it self true, upon which they are bot­tomed) [Page 8]would be as necessary and consequential, as the Demonstrati­ons of Euclide, yet the whole fabrique will fail when it comes to tryal, and be­come like the Astrological Predictions Calculated with Art enough upon a false Ephemerides.

I that come after the Labours and Scrutinies of so many Excellent Men that have gone before me upon this Subject, cannot promise my self or others that I shall say much in this Matter that hath not been said before; and the ne­cessity of a free Discourse requires that I should take in somewhat of other mens Labours. But I shall avoid, as much as I can, the imputation of a Plagiary, by mentioning the Authors as I have oc­casion: But yet, though somewhat that I shall say hath been said before, especi­ally by Linus, and Fabri, yet somewhat will be new, although the most I shall do herein will be to make the Me­thod and manner of Explication of it as much my own as I can, which I shall do in this order.

First, I shall explain some Termes [Page 9]which I shall have occasion to use, that so I may write intelligibly according to that sense I gave my words; though it may be possibly not according to the sense wherein others have used them.

Secondly, as preliminary to what I shall say touching this Experiment, I shall set down some Statical Observati­ons, that may be useful to me upon this inquiry, not that I shall ingage my self in the whole Theory of Statical Principles and conclusions; this hath been done already by those worthy Per­sons that have ex professo handled this Subject, as Archimedes, Steving, Mr. Boyl, and others; but only shall glean up some general Observations therein ne­cessary to this inquiry.

Thirdly, I shall set down what it is not, that may be supposed in the space derelicted by the Mercury, namely, it is not Nothing, nor Ayre, nor Aether, nor any Body that comes from without.

Fourthly, I shall set down what I think it is that possesseth the place de­relict by the Mercury.

Fifthly, I shall set down what I think [Page 10]is not the cause that suspends the Cylin­der of Mercury, in the Tube to that Altitude of 29 Inches, or thereabouts; namely, not the Gravitation or pressure of the impending Ayr, nor its Ela­stricity.

Sixth, I shall set down what I think is the cause, that suspends the column of Mercury from subsiding in the Tube be­low Twenty nine Inches, or thereabouts.

Seventhly, I shall set down those ob­jections, that seem of the greatest force against the last supposition.

Eighthly, I shall take a particular ex­amination of some other Experiments, as touching the cohesion of Polished Marbles, and the Magdeburgh Hemi­sphere, and the rising of Water in the common Pumps.

And this Order I shall as near as I can observe in the ensuing Chapters.

CHAP. II.
The Explication of some Terms, that may be of use in the following Inquiry.

FIrst, I shall observe the difference between the specifical or intrin­sique Weight of a heavy Body, and the extrinsique Weight or pondus molis.

For instance, a pound of Mercury, and a hundred pound of Mercury, have the same intrinsique Weight, but yet not the same extrinsique Weight: A pound of Water and a pound of Mer­cury have the same extrinsique Weight, for each quantity weighs but a pound, but they have not the same intrinsique Weight, for quantity for quantity, Mer­cury is heavier then Water.

Those Bodies are said to have the same specifical or intrinsique Weight, when the same bulk or quantity coun­terpoiseth equally the other; and those Bodies are said to differ in intrinsique Weight, where a greater quantity of the one is required to Equiponderate a [Page 12]less quantity of the other; as for in­stance, a Cylinder of Mercury, of an Inch long, and half an Inch Diameter, counterpoiseth a Cylinder of Water of the same Diameter and 13 Inches ½ or 14 Inches long, or thereabouts. But although a Body specifically or intrin­sically lighter than another, may in some cases have the advantage in point of speed in motion of a Body of equal extrinsical Weight, because it takes up less room, and so meets with less resi­stance in the medium, yet upon the Scale they equally counterpoise each other.

But again, there is this difference be­tween them; a Body of a greater intrin­sique or specifical Gravity of an equal ex­trinsique Weight, with a Body of less in­trinsique weight, will sometimes equally press upon a Fluid Body, upon its Super­ficies, but will press more than the ligh­ter, when both have the advantage to get below the Superficies; for instance,

Take a pound of Lead, and a pound of Wood, whether lighter or heavier than a quantity of Water equal to it, [Page 13]lay them each upon a peece of Cork that will support them in the Water; the pound of Lead, and the pound of Cork will both swim upon the Water.

But if the Cork be taken away, the Led will sink, and the Wood will swim if lighter than a like quantity of Wa­ter, and if heavier than the like quan­tity it will sink, but not so fast as the Led.

2. There is a difference between an intrinsique Weight, and an accidental Weight, which may be various; as for instance:

In respect of the position of the one and the other: Water and Water are both intrinsically of the same Weight, yet if Water be in a Tube, open at both ends, and be stopt with the Finger at the lower end, and then when contiguous to the Water in a Vessel, the lower end it is opened, all the Water in the Tube will subside to an equal Superficies with the Water in the Vessel, because its higher position gives it an accidental Weight more than that in the Vessel.

So again, Ayr and Ayr have the same [Page 14]Weight, though it be hardly measurable, but if Ayr be compressed as in a Wind­gun, it gains an accidental Gravity by its Compression of parts more than the common Ayr.

3. There is a difference in Terms between Gravitation, and pressure of heavy Bodies; for instance, A Tube stopt at the upper end, and driven down in a Vessel of Water forcibly, the pres­sure of the Water upon the Ayr in the Tube, will contract the Ayr as much as it can (suppose it an Inch) and the rest of the Ayr in the Tube will press upon the Water, because it will not yield more to the Water; this is pro­perly Pressure in the Ayr upon the Wa­ter, and of the Water upwards upon the Ayr; yet neither are properly Gra­vitation, though possibly, I may in some passages use the words promiscuously.

4. There is a difference between Gravitation ad motum, which I call sometime sensible or perceptible Gra­vitation, and Gravitation ad pondus, which I sometimes call real or insensible, or Physical Gravitation: For instance,

If a cubical Vessel of Water contain 56 pound weight of Water, and a piece of Cork, or parcel of Oyl of two pound weight be placed upon the top of the Water, it will not sensibly gravitate, but will be born up by the upper Su­perficies of the Water, whereunto the lower Superficies of the Cork or Oyl will be contiguous, because being spe­cifically or intrinsecally lighter than Water, it is sustained by it, and makes no motion in the subjected Water.

( Fig. I.) But yet it is plain that in concretion with the water, the whole weighs 58 pound, whereas before the water alone weighed but 56 pound; so that here is a gravitation ad pondus ad­ded hereunto in concreto to the water. But let us suppose that the Vessel A, B, C, D, be filled with water unto the su­perficies C, D, and the tube E, open at both ends be immersed into the water, and then a quantity of oyl, that is lighter specifically than water, be poured upon the superficies of the water; this will raise the water into the tube E, above the common superficies of the water, to [Page 16]such a proportion of height in the Tube as will countervail the weight of a like Cylinder of Oyl, which will be some. what near to the superficies of the Oyl, because the water at G, is not equally pressed with the rest of the superficies of the water by the incumbent Oyl. The disparity of the pressure causing motion or elevation of the water in the part not equally pressed; so it is gra­vitatio ad motum, and not simply ad pon­dus. So if upon a vessel of water there be placed a Body specifically heavier than water, but not exactly commen­surate to its superficies; here is gravi­tatio ad motum, as well as ad pondus; for the body sinking into the water must needs raise up as much water as the space it self takes in subsiding into the vessel of water.

And upon the same account it is, if the subsiding body be a Fluid, as Mer­cury, it will by sinking into the water drive up as much water as the room it takes, and so make the superficies high­er; so that an unequal pressure of any Fluid must necessarily make a motion [Page 17]upwards of the parts of it, and thereby raise the superficies by so much in bulk of water as will countervail the room that the immersed body takes up in the water. And this and the like I call sensible gravitation, or gravitation ad motum.

5. There is a difference between Pon­dus, and Potentia; and this is well enough evidenced in the instance of the Oyl and Water above given: The oyl gra­vitates upon all the superficies of the water, except that subjected to the ori­fice of the Tube E there is the pondus of the oyl and the water driving up, and sustaining the water in the Tube to that height that equiponderates a like column of oyl there is the Potentia.

Mr. Sinclere and others, that contend for the Solution of the Torricellian Ex­periment by the Gravitation of the Ayr, apply this difference unto two in­stances, which possibly in the event of their Examination will appear otherwise; namely: 1. That the Ayr equally pressing the restagnated Mer­cury in all places thereof, but that [Page 18]which is directly under the column of the suspended Mercury, and thereby Equiponderating a column of Mercury only of 29 Inches ½ and no more, keeps it suspended at that height by the Equi­pondium of both, there is the Gravita­tion of the column of Mercury, which is the pondus, and the Impending column of Ayr, which is the potentia sustinens, that Counterpoyseth that pondus. I shall have occasion to use this difference of pondus and potentia, in relation to this Experiment also, but in a different way. 2. The other instance, to which he ap­plies this difference, is in all Fluids, whether Ayr, Water, Mercury, or any else: Namely, if a Body be in any depth of Water; suppose above it were 20 foot of Water, and below it two, three, or four Foot of Water, or more, subjacent to the lower Base of the Body. The upper column of Water is suppo­sed to press downwards, per modum pon­deris, upon the upper Superficies of the Body, and the lower column of Water, contiguous to the lower Superficies of the Body, is supposed to press upwards, [Page 19] per modum potentioe. And he supposeth that the pressure of the potentia up­wards, is alwayes equal to the pressing of the pondus downward: This is a sup­position fitted principally for the ac­commodating of the Solution of the Cohesion of Polished Marbles, by the Gravitation and potentia of the Ayr, pressing upwards and downwards, and some other instances, whereunto the single Gravitation of Ayr down­wards will not be sufficient: The proof whereof will be considered hereafter.

6. There is a difference between the resistence or Renitence of a Fluid, and the Gravitation or pressure thereof: If a man strikes forcibly with the flat of his hand upon the Superficies of the Water, he shall find near as much pain as if he struck upon a Board, although the Water doth not counter-move the hand, but receives and resists its sudden force; the like occurs frequently in Ayr: The fierce striking of a wand through it, bends the wand, and the fierce Collisian of the Bullet against it, is not without a resistence of the Ayr, [Page 20]though too weak to encounter it.

And this Renitence or resistence, without any counter-motion at all by the Water, is that which makes the Motion of the same heavy Body through the Water considerably slower than through the Ayr; and the same Weight of Led or Iron, or other heavy Body in Water, to weigh less upon the Scale, than when it is in Ayr, the re­tardation of its Motion, and the cor­rection of its weight, being the same effect of the same Cause; namely, the resistence of the Water, greater than in the Ayr, without relation to any counter-motion, or counter-pressure in the Water it self.

7. There is a difference between Rarefaction and Tention, and between Condensation and Compression, though the effects be much alike in both.

Rarefaction, (for instance, of the Ayr) is the Extention of its parts, commonly by heat, or what is equivo­lent, the fiery Partacles that it receives, whether from the Sun, the Aether, or common fire, or other Calefactive nature.

Tension, is when the parts of the Ayr are distended by virtue of some force or power that layes hold of its Ex­tremes, as a Lute-string is under a Ten­sion to a greater length, by a considera­ble weight appended to it; only it hath this difference, a Lute-string or the like, is not capable of Tension in length, but it must have a contraction in thickness, but Ayr as it hath a motion every way, so it is capable of Tension every way.

The effects aswel of Tension as Rare­faction, are these, viz. the same sub­stance holds thereby a greater and more extended space. 2. The Body, thus either by heat or force, Rarefied or Tensed beyond its true natural size and staple, hath a Motion of restitution, na­rurally contracting it selfd, and pressing inward. 3. The Body thus contra­cting it self, by the Catholick Law of Nature, to preserve the continuity of the World, layes hold upon the Bodies next adjacent, and conterminous to it, and as much as it can draws it inward.

Again, Condensation and Compres­sion differ in this, that the former is [Page 22]commonly made by the Constipation of Cold; the latter, by any other for­cible pressure, as in Wind-guns, Aeoli­piles, and the like.

They both agree in their effects. 1. That the Ayr Condensed or Com­pressed, takes up less room or space, than its natural and due size. 2. That they have each a Motion of restitution, by ex­panding it self to its just size.

And this Elatory or Spring, I allow to the Ayr; namely, of retraction, and expansion, when put out of its natural size or staple: But the imaginary pro­digious Spring, attributed to the com­mon Ayr, as its natural tendency, I take to be only invention.

It is hard to say to what proportion Ayr may be Rarefied or Tensed; some think to above 70 times its common ex­tension, or to what degree it may be Condensed or Rarefied; some think to seven, nine, or ten times, less then its ordinary consistences, or more: Quod vide apud Morsen in pneumaticis, et aliis.

8. There is a difference between the common Gravitation of a Fluid of [Page 23]any kind, as it is a heavy Body, and the appropriate Gravitation of it as it is a Fluid Body: In respect of the former, it doth as all heavy Bodies, press per­pendicularly downward towards the Centre; But as it is a Fluid Body, it hath an appropriate Gravitation of its own, whereby it corrects and allayes in some sort, its common Gravitation: For instance, Water in its own consi­stency, hath a lateral Motion, a Motion per declivè, an Horisontal Motion, within the compass of its own Super­ficies; yea, and a Vertical Motion up­ward, within the compass of its own Superficies: As if a Tube full of Ayr, stopt below, be immersed into Water, and then unstopped, the Water will heave as freely upward as it would otherwise downward, till it attain its own common level or Superficies; and sutable to its Motion is its Gravitation, which is nothing else but motus, or cona­tus ad motum.

And besides this appropriate Gravi­tation of Fluids, there is a certain pro­per and connatural Texture in Fluids, [Page 24]and especially in Ayr, whereby the sub­jected parts do suspend, and hold up considerably the Superior parts from any considerable Gravitation, so that no Body, or portion of space less than the whole Base of the whole Fluid is considerably pressed upon by any such imaginary Column Commensurated to the Base of the subjected Fluid, as hath been elsewhere observed, and will be further Illustrated in some of the following Chapters.

9. There is a common and allowable difference beween the pure Ayr, such as may be in the upper Region, and that which is now commonly called the Atmosphere. The former is so pure and subtil, that the greatest pre­tenders to the Ayrs Gravitation that I have seen, do not take upon them to to determin, that it hath any Weight.

The Atmosphere, is that portion of the Ayr that is the common receptacle of Vapours, and the Effluvia of the Earth and Water, whereby it is less subtil than the pure Ayr.

Though some, out of the confidence [Page 25]they have of their attaining the just pro­portion of weight between Water and Ayr, and the just proportion of weight between Mercury and Water, and upon the high confidence they have of the just Equipondium between 29 Inches ½ of Mercury, and a Column of Atmosphere of the same thickness with the Column of Mercury, have undertaken, to define the just height of the Atmosphere; some determining it to be just 7000 Fathoms, some 7 Miles; yet the Doctors much differ among themselves in their ac­count; some telling us, they take it to be 22 Miles high, others 50, others above 100.

And there must needs be an excee­ding incertainty in this way of Com­puting it. For first, Though the just proportion of weight between the Quicksilver and Water is easily and cer­tainly discovered to be truly as Mersen­nus, and others, have accounted it, viz. that one Cubick Inch of Mercury will just counterpoise 13 Cubick Inches and ½ of Water; yet the proportion of weight that Ayr bears to Water, (if it [Page 26]have any real weight at all,) is not to be exactly Calculated, whatsoever Expe­riments have been made thereof by Mersennus and others; the former tel­ling us, that the weight of Water to Ayr, is as one to about 1300; the others telling us it is as one to 1000, or at least some small proportion less. 2. Admit the proportion were justly known, yet those that take their mea­sure of the height of the Atmosphere, or Gravitating Ayr, (if any such be) by the supposed Equipondium, between 29 Inches ½ of the suspended Mercury; and a Column of Ayr commensurate in thickness to such a Mercurial Co­lumn, have bottomed themselves, as I think, upon a false Foundation. 3. But if it were true, as they would have it, yet even upon their own principles, it is extremely mistaken and convinced by their own suppositions and Experi­ments, as shall be observed in the ensu­ing Chapters.

And thus far to render my self intelli­gible in my expressions in the future Inquiry.

I shall only add some Matters that will be useful as to the point of Calcu­lation.

The weight of Water is various, according to several places; Stevin tells us, that in some parts of Holland, a Cubique Foot of Water weighs 63 pound; as I remember, Mr. Sinclere Computes it to 56 pound, and conse­sequently, a Cube of Water 6 Inches square, weighs 7 pounds; and I have by tryal found, that it weighs 7 pounds wanting two Ounces; but the Stan­dard of 56 pound and 7 pound, ordina­rily sutes the proportion of weight of those two Bodies: Upon tryal, I have found the proportion very little diffe­ring, viz. a Cube of 6 Inches square of Water to weigh 7 pound wanting two Ounces, and consequently a Cu­bical Foot to weigh 55 pound 4 Ounces.

The readiest way to avoid Fractions and the long process of Arithmetical Calculations, is by immersing any re­gular or other Solid Body into a Vessel full of Water, and to save that which [Page 28]is impelled over by the immersion of the Solid Body, to discover the proportion of weight between such a Solid, and a Fluid of the same Moles or Dimensi­ons.

The measure of a Cubique or Square Body, is by Multiplying the one side into the other, to find the Area of In­ches; and by Multiplying the Area by the measure of Inches in profundity.

The measure of a Cylinder is by multiplying half the Diameter into half the Circumference, which yields the Area, and Multiplying the Area (of Inches) into the number of Inches, in the depth of the Cylinder: I mention these Figures, because the most ordina­ry and useful in Hydrostatiques.

Mercury is thirteen times and an half and somewhat more heavier than the like quantity of Water, as I have found upon tryal: If it be taken four­teen times heavier, it will not be much out of the way, and avoids Fractions. And therefore upon that computation, if a Cube of six Inches Square of Water weighs seven pound, a like [Page 29]Cube of Mercury will weigh 98 pound Averdupoise.

The often use of Mercury even in the Torricellian Experiment, but espe­cially, where there is occasion of fre­quent Superfusion or Infusion of Wa­ter in the operation, will certainly much alter its Texture, Weight, and Use, as I have Experimentally found.

It is a matter of great difficulty to avoid the immission of Ayr in the Torricellian Experiment, which will much disorder the operations.

CHAP. III.
Concerning the Gravitation of Bodyes; and first, concerning the Gravitation of Fluids, in relation to Fluids of the same kind and consistence: And therein also, first of the Gravitation of Water upon water.

ALL heavy Bodyes have a Physical Gravitation belonging to them, as the natural effect of that Gravity; for Gravitation is either Motion, or conatus ad motum, which is the natural effect or action of Gravity.

And yet although the parts of all continued Homogeneal heavy Bodies participate of the same common Gra­vity, that is common to the whole continuum; Those parts are impeded in their actual or sensible Gravitation one upon another, by the support that each inferiour part gives to the superi­our parts, as the upper parts of a Cube of Lead do not actually Gravitate upon [Page 31]the inferior parts, because the upper are Mechanically impeded by the lower, from their actual Gravitation upon them; yet every Atom thereof con­tributes to the Gravitation of the whole upon the Scale.

But if the Solid Body be not all of the same consistence, but the lower are of a lighter or more laxe Texture, or consistence than the upper, there the upper parts will not only Physically and really, but Mechanically and sensibly Gravitate upon the lower, according to the measure of their excess of weight and solidity above the lower, as if the upper part of a concrete Cube consists of Lead, and the lower parts of Clay, in process of time, at lest the upper will crumble away and decay the lower, by their more prevalent Gravitation, and the impority of the resistence and sustentation of the lower.

Touching the Gravitation of Fluids upon Fluids, of the same kind and con­sistence, I shall premise something; and first, concerning the Gravitation of Water upon Water, and then of Ayr upon Ayr.

It seems clear, that the upper parts of Water do not actually or sensibly Gravitate or press upon the lower parts of Water; They do indeed Gravitate ad pondus and Physically upon the lower, so as to make the whole hea­vier, but they do not. Gravitate ad mo­tum, or sensibly: That which per­swades me hereunto is Reason and Ex­perience, or Observation.

( Fig. 2.) For Reason, I alledge, that if the upper parts, suppose the Cube of Wa­ter C should Gravitate sensibly upon D, and consequently upon E, in the Vessel of Water A B, it must either be by displacing of D and E from their positi­on, and so C to subside in the place of D, and after in the place of E, or else it must be by Compressing of D into a shallower space; but it can be neither of these, and therefore it cannot sensi­bly or ad motum, Gravitate upon D, and consequently upon E.

As to the first Proposition, we can­not, that I know of, think of a third; It is true, it hath a Gravitation ad pon­dus, because it adds the weight of a [Page 33]Cube of Water to the common weight of the Water, but as to any sensible Gravitation, or Gravitation ad motum it is otherwise.

As to the minor Proposition, it con­sists of two Parts; 1. An Exclusion of the displacing of D: 2. An Exclu­sion of its compression or contraction in height.

1. It cannot remove D from the place it holds, because the Cube of Water C is of equal weight and solidness with that of D; and it must be either a Body intrinsecally or at least extrinse­cally heavier than D, that must make D give place to it.

If it be said that D may get out of either side, and so give way to the pres­sure of C; that cannot be, for the Col­lateral or Transversal Column of either side, as strongly compresseth D as the Cube C, because each side is not only pressing with its lateral pressure against the sides of D, But there impends up­on that lateral Column a Cube or Co­lumn, of equal hèight with C, and pres­seth as hard upon it.

2. Again, if C should actually and sensibly Gravitate upon D, and conse­quently C and D upon E, and so C should subside, that which is driven up would possess the place of C, and then that should subside again, and other should succeed in its place, and so the Body should be in perpetual Motion, which is not only contrary to common Sense and Experience, but to Reason also.

3. Again, (which is but a various Explication of the first instance) it is not possible for a Body of equal weight (such as C is to D) to impel or drive out of its place a Body of the same equal weight, for the resistance is as strong as the power that should move it, which necessarily must give rest; for if the Cube D be driven out of its place unto a higher Superficies, it must be driven up by a greater weight than it self, otherwise it will never obey it, nor yield to it.

Some therefore finding these diffi­culties, have resorted to the second part, namely, That the Cube D is comprest into a shallower consistence: But this can not be neither.

First, if it be compressed down­wards; namely, between C and E, and also E between D and the Fund, then it must be comprest narrower also, be­cause for the reason before given, the lateral pressures against the sides of D must be as effectual as that upon the upper Base of D; which would make strange work.

Secondly, Though the quality of Ayr be such, as it may be capable of Compression, yet Water is utterly uncapable of it; if we lay a weight of a hundred pound upon a Vessel of Wa­ter, indeed if it do not compress the whole Superficies of the Water entire­ly, it will drive it up where it doth not press; but if it strictly cover the whole Superficies of the Water, it will never press it shallower.

Thirdly, It is more evident to Ex­perience, that the lower parts of the Water are not pressed by the upper: For first, If it should be so, a Tube of Water, suppose ten Foot long, filled and closely stopped at both ends, would break the Glass, if it lay Horizontally, [Page 36]or if a reclined Tube were exactly fil­led, yet being set up perpendicularly, it would leave a vacancy, which it will never do, notwithstanding the preten­ded Accession of the Gravitation of Ayr to boot. Again secondly, Let any man try it in a Tube of Water of con­siderable length, and put in a little button of Wax, inclosing a peece of Lead to make it sink, it will sink to the bottom of the Water, rather with some little degrees of Acceleration, the lower it descends; which could never be, if the Water were more compact and prest below than above.

As to Experiments and Observati­ons, it is agreed by all persons, that have treated of Hydrostatiques, that I know, only one excepted, That if a Solid Body, suppose of Wood, of equal weight with the like quantity of Water, be placed in Water, it will reft in all Positions under the Superficies of the Water, which could not possibly be, if the Water to wards the bottom were more compressed than it is towards the Superficies: This is agreed by Archi­medes, [Page 37]the Master of Hydrostatiques, in his Book, De Insidentibus Humido; by Stevin, in his Hydrostatical Elements, Prop. 4. By Mr. wallis, Mr. Boyl, and others.

Only a late Author, in his Hydrostati­cal Theorems, tells us, that such a Solid will emerge so, that its upper Superfi­cies will be contiguous to the Superfi­cies of the Water; And this he con­cludes, not so much upon his Observa­tion or Experience, for ought I can find, as upon this very supposition, that the Water below is more compressed than that above.

It is a difficult matter to find any Solid by its own specifical uniform weight, to be just equal to the weight of a bulk of Water of an equal dimen­sion to it, without application of some subsidiary supplyes to equal it, which possibly may make the Experi­ment it self uneffectual; yet upon the best tryal I could make by such subsi­diary applications, I rather find such an Equiponderating Solid rather to be apt to subside to the bottom, than emerge to the top.

2. Again, the next Experiment which I shall mention, shall be that of the same Author, in his seventeenth Experiment, wherein, if I understand him aright, he contradicts what he had delivered in his fifteenth Theorem: viz. ‘ If a Glass bubble with a long stem turned up, heated, and then the stem Her­metically sealed and depressed into the Wa­ter, by a convenient weight of Lead, and the Bubble tyed with a string to the Beam of a Ballance, with so much weight as might counterpoise the Bubble, then the stem bro­ken with a Forcept, whereby the Water entred and half filled the Bubble, the Bub­ble subsided and required an addition of a farther counterpoise of 4 Drams and 38 Grains, to reduce it to an Equilibrium, then the Bubble taken out, and the Water driven out of it, weighed 4 Drams and 30 Grains:’ This instance being given by a worthy Person, to prove, that Water weighs in Water: But the Author, in answer thereunto, clearly evinceth, that the Water in the Bubble is sup­ported by the subjacent Water, and concludes evidently thereupon, that [Page 39]Water weighs not in Water.

3. Again, if Water should sensibly Gravitate upon Water, it must as sen­sibly Gravitate upon any Body sub­jected in it, especially if it be at the Base or fund of the Water: But the Experience of divers, of the agility of Fish of a great breadth, lying at the bottom of the Water, and infinite more, do sufficiently evince, that the weight of the superior parts of Water Gravitate not upon the inferior parts, with any sensible pressure, for if it should, it must of necessity Gravitate upon the interjacent Water, lying be­tween the uppermost Cube and the Bo­dy; and if it should do so, if must con­siderably Gravitate upon the subjacent Body.

But this Non-gravitation of Water upon Water, or upon subjected Bodies, and the reasons thereof, I have elsewhere examined.

( Fig. 3.) An excellent Person, in the first, second, and last Chapters of Hy­drostatical Paradoxes, hath endevoured to prove the actual Gravitation of the [Page 40]superior parts of Water upon the infe­rior, by three instances, viz. If in the third Figure, the Vessel AB be filled with Water unto the Superficies c d, and then the Tube be by suction filled with Oyl of Turpentine (a Body ligh­ter than so much Water) be stopped nimbly at the top, whereby the Oyl remains suspended, and then the lower open end be immersed in the Vessel of Water unto any depth, suppose H, and then the Finger be removed from G, the Supersicies of the Tube, the Oyl will be kept up to such a height as may counterpoise the like Column of Water in the Vessel; and if it be immersed lower, the Oyl will rise in the Cube considerably higher, and if it be lifted up higher, nearer to the Superficies of the Water, the Oyl will subside lower, and discharge part of it self into the Water, because then the like Column of Water in the Vessel grows shorter, and hath a less counterpoise to the Co­lumn of Oyl in the Tube, which he concludes to be a concludent evidence of the various degrees of Gravitation [Page 41]of the Water upon the various imagi­nary Superficies thereof. The second instance is like it, namely, That if the same Vessel were filled with Oyl to the Superficies C D, and the Tube g filled three or four Inches with Water by suction, and the upper end g nimbly stopt with the Finger, and then the lower end H immersed in the Oyl, the deeper it is immersed, the higher the Superficies of the Water in the Tube will remain sustained, and the nearer it is brought to the Superficies, the lower it will subside, by reason of the various degrees of Gravitation of the Oyl in several imaginary Superficies; though at the highest elevation of the Tube of Oyl, in the first instance, the Oyl, in respect of its less Gravity than Water, will sit some what higher in the Tube than the Superficies of the Wa­ter; and the Water in the Tube, in the second instance, will sit lower than the Superficies of the Oyl, because excee­ding it, quantity for quantity in speci­fical Gravity. 3. The third is that of the valve, which deeply immersed [Page 42]in Water, the cover of the value will be sustained by the Gravitation of the Water, with a considerable weight ap­pended to it.

But it seems to me, that these Expe­riments concludes nothing to this bu­siness; but only evidence a resistence of the Water to that Body which will raise its Superficies. For it is appa­rent, that there is required a pressure, or force, to raise the Body of Water to a higher Superficies, exceeding the weight of so much Water as is so im­pelled higher than before, or at least equal to it.

Now the pressing down of the Tube of Oyl into the Water, or the Tube of Water into the Oyl, raiseth the Super­ficies of the Water or Oyl so much as the Tube is impressed into the Water, namely, a quantity of Oyl or Water in the Vessel, equal to the Body impres­sed and immersed in it, is raised there­by, and put out of its former place, which it contents against, by a Reni­tence resistence, or contrary pressure; and as the less of the Tube is immersed, [Page 43]the less Liquor in the Vessel is moved up; so the more of that Body is im­mersed, the more is pressed up, and consequently, the greater pressure is made upon the Water, the lower it is immersed; because it takes up more room in the Water, and a greater force is thereby exercised, to the elevation of a greater quantity of Water; and that Water, the more it is, hath the more accidental weight, or rather, resistence, against that force which thus raiseth it up above its common superficies, which before it obtained.

And that this is the true reason of it, and not the various Gravitations of the superior parts upon the inferior, seems evident by this one instance, which because it will be useful hereaf­ter, upon other occasions, I shall here insert more largely, though the thing be commonly known.

I filled a Tube of Lead of six Inches Diameter, and four Foot deep, and close at the bottom with Water; And took a Porringer of Pewter, five Inches Diameter, and about two Inches deep, [Page 44]and filled it with leaden Shot, and pou­red Water into it, to fill up the chinks, and making four holes, I suspended it with a Packthrid, like the Dish of a pair of Scales, and exactly weighing it, and the Shot, Thred, and Water, it weighed all exactly 78 Ounces, wan­ting ⅛ of an Ounce; then suspending the Dish with a Packthrid, to the end of the beam, I set it down 40 Inches deep into the Water, below its Super­ficies, and it lost its weight, by the resistance and crassitude of the medium, viz. the Water 9 Ounces ½ of its weight in Ayr; and so weighed 68 Ounces, and near about ½ of an Ounce; and just the same weight it held, when raised 15 Inches, when raised 28 Inches, though it was then within 12 Inches of the Superficies; but at last, when I raised it 12 Inches higher, so that the Superficies of the weight was equal with it, and yet it lost not above ⅛ of an Ounce; which I decrement, was, as I think, because possibly the four strings that sustained it were not now under Water.

What then is the reason why, when the Tube of Oyl or Water is sunk lower, the pressure of the Water is un­equal? and why in this instance, the weight of the Dish is no more charged with the weight of the Water, at 40 Inches, than when just even with the Superficies of the Water: I say it is not the Gravitation of the superior parts of the Water upon the inferior, for then my weight of 5 Inches Di­ameter could never keep the same weight at 40 Inches depth of Water, at 12 Inches depth, and just at the Su­perficies; but the true reason is, because in the weight of the Porringer and Shot, being the same bulk at 40 Inches deep, as at the very Superficies, drives up no more Water out of its place at one station, than another; namely, a bulk commensurate to the bulk of the Porringer, Shot, and included Water, which is the same, both at the fund of the Tube, and when its Superficies is contiguous to the Superficies of the Water: But in the instances of the Tube, if it were suppressed an Inch [Page 46]Diameter, when it is immersed an Inch its potentia, lifts up but a part of Water commensurate to that Inch; and there­fore the resistence, or Renitence between the Tube, and the Water, is but little; but when it is immersed ten Inches, there is ten times more Water driven up, and therefore the Renitence is the greater, and impels the Liquor included in the Tube the higher; But this con­cerns nothing the weight of Water in its quiet consistence: His other Expe­riments, in order to the proof of the Gravitation of Water upon Water, I shall consider in the fifth Chapter.

CHAP. IV.
Concerning the Gravitation of the Ayr upon Ayr, or any subjected Bodies in it.

THe Question in hand concernes not Ayr put out of its ordinary texture, but touching the free Ayr, wherein Men and Animals live and breath.

And now to state this Question a­right, we must consider, 1. What the Question is not, and 2. What the Que­stion is.

1. The Question is not whether Ayr compressed and thrust together, hath a weight in it that may put it into a con­siderable Gravitation upon other Ayr, either not compressed at all, or less compressed; for it seems very proba­ble by the Experiments of these Ex­cellent Men, Mersennus, Shottus, Mr. Boyl, and others, that have set them­selves unto tryals, in order to this in­quiry, [Page 48]that such a Gravitation may and doth happen by the compression of Ayr in AEolipiles and Wind-guns, that such Ayr may have a pretty evident prepon­deration to so much free and common Ayr.

2. Neither is it the Question, whe­ther there may not be, or are not inter­spersions of Vapours Effluvia, and Efflu­via, or other Moleculoe even in the free and common Ayr, that considered in themselves, have a preponderation even to the Ayr it self; for although the strict intermingling, interweaving, and contiguation of some Vapours and Effluvia, grosser and weightyer than the Ayr it self, may enable the Ayr to su­stain and bear up many of these grosser Bodies, (as Water oftentimes sustains minute Bodies, or Gravels of Sand spe­cifically heavier than the Water) yet we every day see, that if these portions of interspersed Vapours or Effluvia, grow too heavy for the Ayr to sustain them, they are precipitated out of it, and discharge themselves upon the Earth, as we see in Hail, Snow, Rain, [Page 49]and Mists. 3. Neither is the Question, whether a portion of the free Ayr, sepa­rated and disjoyned from all commu­nication with the foreign Ayr, hath any Gravitation or no, for it seems to me, that it may have, by such a separation an actual Gravitation, which is not by rea­son that it acquires any new quality or accession of weight, than it had before, but by reason of such separation it doth Removere prohibens of its actual Gravita­tion; namely, the contignation that it hath with the common Ayr, into and with which it was in continuity, it was interwoven, and that little inconsiderable Gravitation that it natu­rally and simply considered hath, is overmatched and broken by those inter­veining Filaments of the rest of the Ayr, with which it is in continuity.

And therefore I do think, that if Ayr of the same consistence with the Ayr we live in, were freely let into a Bladder, which we will per imposibile suppose to be destitute of all weight, such a Bladder of Ayr, thus filled, (though without the help of inflation, [Page 50]by our longes, which must needs carry with it some fuliginous Ingredients;) I say, such a Bladder of Ayr would sub­side in the same common Ayr out of which it was taken, and would Gravi­tate upon the Ballance, more than the like quantity of free and open Ayr incumbent upon the other Ballance.

Nay farther I dare adventure to say, That if we could suppose a Tube, open at both ends, so long, as to reach from the top of the Atmosphere, unto this Earth, such an included portion of Ayr, severed from communion with the Atmosphere, would have some Gravita­tion more considerable perchance, than we have ever felt from the open Ayr.

For I do much attribute the exclu­sion of all sensible Gravitation of the free Ayr, to that mutual interweaving of the Filaments of Ayr one into ano­ther, like a vast Net, with small Mashes or interstitia, filled gradually with parts more and more subtil; and this contig­nation sustains and keeps the parts of it from that separation, that otherwise [Page 51]the interposition of a grosser body would intercept: And although Wa­ter, in respect of its weight and texture, be more subject to disjoyn from the rest of its body, than Ayr is, we shall find in the next Chapter somewhat Analo­gous to this, even in a consistent Body of Water.

4. Neither is it the Question, whe­ther even the free Ayr it self may have some intrinsique Gravity, though ad­mirably little and inconsiderable; for if we do suppose the compression of divers Particles of Ayr may render that compressed Body of Ayr sensibly hea­vy, we may not wholly exclude those Particles from all kind of Gravity be­fore compression, for no weighty Body can arise from the coalition of such parts as had no manner of Gravity before.

5. Nay, yet farther, the Question is not, whether as the free Ayr hath some intrinsique Gravitation; so neither is it the Question, whether this free Ayr hath not some, though very inconside­rable measure of actual Gravitation; [Page 52]it is not impossible but it may have some, though scarce perceptible to sense, notwithstanding all the inter­spertions and mixtures of Vapours and Effluvia from the Earth and Water.

But the Question is, whether the free and common Ayr, wherein we live, which is commonly called At­mosphere, extending upwards about seven Miles or more, hath any sensible actual Gravitation upon the lower World. 2. Admit it have, whether any determinate portion of that Atmo­sphere, as a Column or inverted Cone, for the purpose, of six Inches square at the Base, hath any actual Gravitation upon the subjected Base, upon which it is supposed to rest. 3. Admit it hath, whether that Gravitation be of any considerable, and of what moment.

Before I come to discuss the Questi­ons themselves, it will be necessary to repeat somewhat that I have before said, touching the proportion of Gra­vitation, that is alloted to a portion of, for instance of six Inches square of the Atmosphere, when it pertingeth near to the Superficies of the Earth.

A Cube of Water, six Inches square, contains 216 square Inches, and upon the exact Calculation of those that have tryed it, weighs just seven Pounds, and a Cube of twelve Inches square of Water weighs 56 Pounds.

A Cube of Quicksilver weighs four­teen times as much as the like quantity of Water, though Mersennus, and some others, nearer to the truth, com­pute it to be thirteen and ½; but I will make my Calculation by fourteen, to avoid Fractions.

The consequence whereof will be, that a Cube of six Inches square of Mercury, will weigh 98 Pounds, which is fourteen times as much as the like Cube of Water.

The consequence whereof is, that fourteen such Tubes of Mercury weighs 1372 pound.

In the Torricellian Experiment, the Mercury is sustained to the height of 29 Inches ½; to avoid Fractions, let us reckon it 30 Inches, be the Column never so large.

If the Column of Mercury be six [Page 54]Inches square at the Base, then there will be five such square Cubes of Mer­cury in that Column will weigh 490 Pounds: According to the late Phi­losophy, this Column of Mercury is counterpoised with a Column of the Atmosphere of six Inches square, and extending from the restagnant Mercu­ry to the upper surface of the Atmo­sphere.

And consequently, this Column of Ayr or Atmosphere, doth actually gra­vitate with a weight of 490 Pounds, upon the restagnant Mercury, and real­ly and actually weighs as much as that comes to; and consequently, when I hold a Trencher in my hand of six In­ches square, there is incumbent upon it 490 Pound weight of Ayr, though there be found a help in that case to support it, by the recoyling Column of Ayr, commensurate to it; whereof in its due place.

And this is the supposition I contend against in this paper, viz. that 1. The whole Body of the Atmosphere hath no considerable Gravitation either upon its [Page 55]own parts, or upon the subjected Body of the Terrestrial Globe, much less such a prodigious Gravitation as is here supposed. 2. If it had, yet any given portion or Column of the At­mosphere, hath no such Gravitation.

Touching the Gravitation of the whole Atmosphere in general, upon the Terrestrial Globe entirely, I shall not say much, because it is not capable of Experiment, only my reason and sense suggests it to me, that it is neither evi­dent nor likely to be of so vast a Gra­vitation as the late Philosophers affirm.

First, I confess I am none of those Adepts in Philosophy, that can tell us how to solve all the effects in Nature, without recourse to the infinite Wis­dom, Power, and Goodness of the Glo­rious God, who certainly knew better how to frame the World, and fix the Laws of Nature, than the wisest of Men or Angels. I must confess, I know not how to resolve the reason of the Motion of weighty Bodies downward nor why or how either the Sun holds his regular Motion, if the Hypothesis [Page 56]of Ptolemy be true, or why the Earth, as other Planetary Bodies, holds its re­gular Motion, if the Systeme of Coper­nicus, and Galilaeus, be true, and a thou­sand such instances; but into the primi­tive disposition and ordination of the Most Wise, Powerful, and Soveraign Lord and Maker of the World, who hath fixed the Order and Law of Na­ture, by his Soveraign Fiat, with the most exact accommodation of it to the concerns of the Universe, and all the parts thereof, and with most in­comparable Congruity. This Sove­raign Architect, that hath made all the parts of this Mundus aspect abilis in Or­der, Weight, and Measure, and designed the Earth and Ayr, for the habitation and use of Men, and all other breathing Animals, and likewise for Vegetables, hath so ordered and digested the texture of the Ayr, that the inferior part is more gross than the superior, and fit­ted for nourishment and respiration; the upper parts more subtil, and pure, and light, and destined to other uses, hath ballanced the Ayr, so that the more [Page 57]light and subtil parts are inclinable per­chance, more to ascend; and the lower parts gradually more laden with Parti­cles of a grosser allay, and so possibly thereby inclinable to subside; and he hath connected the more subtile, and the more Feculent parts thereof, so together, that they hold an Equilibrium as a state and posture more serviceable to the ends and uses he designed for it, and for which they serve: The procee­ding of this Soveraign Architect in the Frame of this great Building of the Universe, not being like to the Architecture of men, who begin at the bottom; but he began at the Roof, and Builded downwards, and in that process, suspended the inferior parts of the World upon the superior. But this kind of reasoning, I know, is not grate­ful to the palate of the present Philoso­phers; I therefore proceed.

Secondly, Therefore I say, that the common appearances of the World, so far as they are obvious to our common senses, contradicts this immense, nay, or any considerable Gravitation of the [Page 58]Atmosphere upon subjected Bodies; It is hardly conceptible, how Birds could raise themselves upon their wings, and keep themselves in free Ayr, if a bur­then perchance of above 1000 pound weight should lie upon their Wings and Bodies; it were not possible for me to breath, to walk, to stand upon my Feet, if at every time I open my Mouth, a Column of Ayr of three hundred pounds weight were pressing into it, it would tare open the valves of my Larinx, and blow up my Stomach and Intrals, like a Bladder, and break my Ribs, if it had an admission; and if it had not the circumjacent pressure of the Ayr, would press me to death: These and the like instances render this prodigious Gravitation of the Ayr incredible to us vulgar Souls, that are apt to creditour senses.

But I very well know, that these will be said to be vulgar common pla­ces, and that they have many hand­some Solutions of these common diffi­culties.

And it is true, I very well know, [Page 59]they have colourable Solutions for those sensible occurrences, as the sup­posed counterpoise of included Ayr, and of the recoyling Columns of Ayr; which I shall in due time consider.

But I do reply, that though these common instances perchance amount not to demonstrations of the untruth of the Hypothesis, yet they do require a very great and very clear evidence to encounter even those vulgar experien­ces; and therefore, if any Solutions offred of them, are not perfectly con­cludent, but strained, and the instan­ces they give in their favour, are capa­ble of any other Solution, than this which is so visibly and apparently con­trary to our sense; such Solutions and such instances are too weak and impo­tent to build such uncouth conclusions upon.

Thirdly, Therefore I say, there is not any one instance or experiment, that ever I yet heard of, for the evincing of this imaginary Gravitation of the free Ayr, but is readily capable of a more sutable Solution more adequately [Page 60]fitted to the Phaenomenon, and less in­cumbred with difficulties than this new Solution, by the Gravitation and Elatory of the Ayr. I shall refer my self herein to Mr. Linus his Tract De In­seperabilitate Corporum: And Honoraly Fabri, in the 6 ^th of his late Philosophical Conferences, wherein all the instances given from the Magdeburg Engin, and the English Ayr Pump, and particularly the Torricellian Experiment, are suffi­ciently and much more satisfactory and naturally solved, without recourse to this imaginary Weight or Spring of Ayr.

And there are above an hundred Ex­periments of this kind and nature, which can never by this solution be ex­plicated (without intolerable torture of them) some instances whereof we shall in due time remember.

But omitting more that may be re­plyed in general to the common Gra­vitation of the Ayr; I shall more par­ticularly and closely apply my self to the second.

2. Therefore, admitting it were [Page 61]possible to suppose the whole Body of the Atmosphere might Gravitate upon the Earth in general, yet no one par­ticular portion of the free and common Ayr, impending upon any one determi­nate Superficies, can at all or at least can sensibly or considerably Gravitate upon any determinate Basis.

And the reason seems to me to be this, because although we should admit a considerable Gravity of a portion of Ayr taken, divided and separated as one intire separate Gross Body (as in a Bladder, a Glass Bubble, or the like) so that it partakes of the common quality of heavy Bodies, yet there is a peculi­ar pressure or Gravitation belonging to this subtile Fluid Body, which hath its lines of direction every way within the compass of its own extream Superficies, whereby that perpendicular Gravita­tion, which is common to all Bodies, is corrected, abated, and in a great mea­sure suspended. 2. Because that if there were no such allay given to its common perpendicular Gravitation, by its proper Motion or Gravitation of its [Page 62]own; yet the Ayr being one continued Body, and so interwoven and mortaised as it were, one part in another, the other parts of the Ayr that are conti­guous every where to the Earth, do sustain and bear it up, like the sides of an Arch, from any sensible pressure or Gravitation upon any determinate or particular Body, that is within the com­pass of its pressure; as I have elsewhere inforced the Argument in relation to the Gravitation of Water upon sub­jected Bodies, narrower than the com­mon Base that supports such Water.

And although the Ayr hath an in­termingling with it of Vapours and Terrestrial and Aqueous Efftuvia hea­vier than it self; yet they are so inter­woven in the very Webb and texture of the Ayr, that it supports many of them, and those that are too heavy for it, or much disunited and separate from it, are precipitated upon the Superficies of the Earth, and the Ayr discharged of them, as in Rain, Snow, Hail, sub­siding Gravel Sand, & c.

And although the instance that I [Page 63]am now giving, is more proper for the next Section, yet it is in some kind su­table for the explication of what I intend.

Of all hands it is agreed, that the Water, though a Fluid Body, is, some say, thirteen hundred times heavier than the like portion of Ayr; others, that it is a thousand times heavier; they that speak least, say it is above nine hundred times heavier than Ayr: And it is obvious to any that attends it, that there is not the same strict Cohesion of one part of Water with another, as is of one part of Ayr with another, un­less divided by a more firm and stable Body then it self: And therefore there is far more reason, that one part or Column of Water in its consistency should Gravitate upon a subjected Body, than there is, that a Column of Ayr should in the free and open Ayr, Gravitate upon a body subjected to it; And yet it will be found, that in libera aqua, that Gravitation that it exerciseth upon a Body subjected to it, and capable of it, is not above one half so much [Page 64]as the weight of such a Column of Water, divided and separated from the common consistent Water.

It is true, I had not so dextrous a Messenger, to make the Experiment in the bottom of the Sea, or 20 Fathom within Water, as Dromo is Poetically related to have done, though I believe he never made that tryal: But I will give an account of what I have tryed and found.

( Fig. 4) I took a Glass Siphan of a quarter of an Inch Diameter, the lon­ger legg 32 Inches, the shorter 8. Inches long, open at both ends.

I filled the short legg with Mercury, which accordingly as it must, rose to 8 Inches high in the longer legg; and then stopping the shorter legg with my Finger to avoid any violent pressure by the fall of the Water upon the Mercury, I then filled the longer legg to the top with Water, and gently removing my Finger from the shorter legg, to avoid too violent an Exsilition of the Mercury, I found the Mercury to subside in the longer legg two Inches and a quarter, [Page 65]and as much driven out of the shorter legg, by the accession of the weight of 24 Inches of Water in the longer legg, (which I confess is somewhat less than the proportion of weight between Wa­ter and Mercury; wherein, according to an exact calculation, 28 inches of Water counterpoiseth 2 Inches of Mer­cury. But then emptying the Water and Mercury out of the Tube, I again filled up the Tube with Mercury, to 8 Inches in both leggs, namely to the top of the short legg.

And then filling a glass Tube, of a­bout three Inches diameter, and 32 In­ches long, with Water, I immersed the Syphon with the Quick-filver to the bottom of the greater Tube full of Wa­ter. And although the column of Wa­ter in the great Tube, impending upon the orifice of the shorter legg, was full 24 Inches, yet it drew down the Mer­cury in the short legg, and raised it in the longer legg, empty of Water, only one Inch, and no more, whereby it did rise in the longer legg to 9 Inches, and subsided in the shorter to 7 Inches, [Page 66]as I could easily perceive through the great Tube, by a Scale of Inches, and quarters, fitted to each leg of the Syphon.

I then tried it doubly, viz. pouring in the Water into the longer legg of the the Syphon, whereby the subjacent Mer­cury subsided in the longer legg two Inches, and as much thereof driven out of the shorter legg, and then immersed the Syphon into a glass-vessel, 32 Inches deep, filled with Water; the Mercury thereupon subsided in the short legg somewhat neer an Inch, and no more, and accordingly impelled up the Mer­cury and incumbent Water in the lon­ger legg neer an Inch: whereby it ap­pears, that there was no AEquipondium between the pillar of Water included in the Tube, and the imaginary pillar of Water in the open vessel.

And in this experiment I must re­member, that the orifice of the shorter legg of the Tube, and the legg it self, was of somewhat a larger diameter than the longer legg; and that might give some advantage to the pressure of the Water in the vessel upon the shorter [Page 67]legg. But notwithstanding that advan­tage, the gravitation of the external Water, or any imaginary column there­of was not half so much as the gravita­tion of the Cylinder of Water included in the Tube; which is sufficient to con­vince the mistake of those that assign an equal pressure to an imaginary column of free Air or Water, with an equal column of Air or Water that entirely presseth upon the Mercury, and hath no other circumjacent base to lean upon.

And it is to be noted, that although, as I have said, a Cylinder of two Inches of Mercury doth really counterpoise a Cylinder of 28 Inches of Water, of the same diameter, yet in this instance of the Syphon, 24 Inches of Water drew down two Inches of Mercury, and rai­sed as much out of the shorter legg. And the reason seems to be, because the Mer­cury being in aequilibrio, was more capa­ble of a sensible pressure by a less quan­tity of Water in this libra naturalis, than it would be, if both were weighed in their gross consistence in an artisicial Scale.

And the reasons why the pressure through the Tube, is stronger than the pressure by the open vessel of Water, are these: 1. Because in the Tube the Water included had no communion with any open or free Water, nor had any sustentation thereby, but in the com­mon Water there is a communication and mutual sustentation of one part by another. 2. And principally because when in the Tube the Water had no other Base but the Mercury, to which it was commensurate, and therefore sin­gly, and entirely, and adequatly pressed it. But the Water in the vessel had ano­ther Base circumjacent to it, namely the bottom of the vessel, from which it was built like an Arch over the short legg of the Mercury, whereby the weight, pressing upon the Mercury, was broken, abated, and intercepted. For Water will find the lowest Base for its rest.

And surely if this be true in Water, as upon more than one tryal I found it, it will be much more so in the open Air, which will much disorder the whole hy­pothesis [Page 69]of the Gravitation of the Air, and those very subtle and fine Conclu­sions that are spun out of it, and built upon it.

But I would not be mistaken, as if I meant that the Column of 24 Inches of free Water did gravitate upon the ori­fice of the shorter legg of the Syphon, to the weight of neer an Inch of Mercury, for That is wholly contrary to my Sup­position: but only I hereby shew the great disproportion of the appearing Gravitation of Water, where it hath no lower nor other Base upon which it leans, but only the body of the Mercu­ry, and where it hath another or lower Base upon which it leans.

For in this instance of the Syphon, there is another reason of the Gravita­tion of the free Water upon the cavity of the shorter legg of the Syphon: for here the pressing or keeping down of the body of the Syphon into the free Water, displaceth and raiseth up a por­tion of Water answerable to the bulk of the whole convex Superficies of the Syphon, which is far greater than its [Page 70]cavity, and that Water so diplaced doth indeed press upon the Tube that displaceth it; and because it can find no part yeilding to its pressure but the orifice of the shorter Tube, it presseth there in such proportion, as the whole bulk of the Water so lifted up by the immersion of the Syphon, bears to about an Inch of included Mercury, and 24 Inches of the Water included in the Tube. But of this more distinctly and exactly, when I come to examin the reason of the Valve.

2. But having thus offered my rea­sons against this prodigious Gravitati­on of the imaginary Aery Cylinders, I shall proceed to some plain and home [...] Experiments and Reasons, which seem to me very much to encounter the Sup­position.

I shall begin with that whereunto I am sure they are furnished with an An­swer, but such an Answer as will give me the opportunity of a Reply, which possibly may be of more moment, than if the Experiment it self were without an Answer.

Take a pair of Scales, the one Dish of 12 [Page 71]Inches of diameter, the other of 3 Inches diameter, yet of that thickness, that it may be just of the same weight with the other, each dish weighing for the pur­pose three Pounds. These two Dishes will yet exactly equiponderate, yet the one sustains a Column of Air of above twelve times the weight of the other, yea and according to the proportion a­bove computed, possibly the greater Column impending upon the greater Dish, may weigh above 4000l weight.

But there is a common Answer sin­gularly fitted to this difficulty. For it is said, there is a Column of Air below each Dish, that hath a Superficies com­mensurate to the lower Base of each Dish, which though it be but 3 or 2 or 1 foot, nay but an Inch above the Earth, bears up each Dish as strongly as the Column of Air of 7 miles high bears them down, and so there is an aequipondi­um between the pondus deprimens upon the upper side of the Scale, and the pa­tientia sustinens of the lower side, and the Pillar of a Foot of length, between the Earth and the greater Scale, is of a [Page 72]Foot diameter, and sustains it as forcibly as the pondus deprimens of a Foot diame­ter depresseth it, and so it is supported by an equal force impelling it upward, as it is depressed by the weight of Air incumbent upon it. And the case is the same with the lesser Scale, and so the greater Scale, though it hath a greater weight than the lesser impendent upon it; so it is recompensed with a more forcible power than the less hath to su­stain it, and so there is an aequipondium.

But although this seems marvellous, that the potentia of a Pillar of Air from the Earth to the Base of the Scale should counterpoise so vast a weight, as what is incumbent upon it, yet to serve the turn, and to give a Solution by the weight and power of the Air to main­tain the cohesion of two polished Mar­bles ( de quo infra) this reason is given, that as there is a vast weight of Atmo­sphere upon the Scale, so there is the same Gravitation of Air round about it all, but what is just under the Scale; and this impending Air round about the sides of the Scale, as it is so much, so it [Page 73]is somewhat weightier than that which impends upon the Scale; for this reaches only to the Scale, and that reacheth somewhat farther in length, even by so much as the distance is be­tween the Earth and the Scale; and this doth so gird and help in that short Co­lumn of Air subjacent to the Scale, that it is as firm a Pedestal or potentia to su­stain the Scale, and to press it up by the auxiliary Columns of Air, that supply and support it, as the impending Co­lumn is to depress it, and so between both there is an aequipondium. So that in all cases, as well in Air as Water, the subjected Column sustaining and im­pelling upwards, and the potentia there­of is of equal force to the pondus of the superior Column, depressing the upper Superficies of the intermediate Body.

And the same they suppose in Water, the instances whereof is the Valve, and some other instances; but of these in the former Chapter.

And now upon this Supposition of the potentia sustinens of the recoiling Pillar, as I may call it, sustaining and im­pelling [Page 74]up the lower Supersicies of the body, they have raised most marvellous Paradoxes and Consequences, namely, that if a Milstone were by some art sus­pended in the Air, if it were possible that the Pillar of Air incumbent upon it were either wholly taken away, or de­prived of all Gravitation, this Milstone would be sustained by the subjected Co­lumn of Air, and possibly carried up much higher, yea, and if a long Co­lumn of Brass were let down deep e­nough into the Ocean, they assign a depth, at which the Column of Brass would sink no lower, but be sustained by that marvellous potentia of the recoil­ing or subjected Column of Water: things that I confess are wittily dedu­ced, and consequential enough upon their postulata admitted, but such as are warily enough propounded, because impossible to be tried.

But in answer to this Question like­wise, I say this will be found untrue, and therefore although the Consequences are Logically enough inferred upon such premises; yet the thing proving [Page 75]false in the event, the Premises, Princi­ples, and Postulat a themselves must needs be fictitious and vain.

Suppose therefore two small Cylin­ders of Brass, each of 41 weight, but the one of two Inches diameter, the other of one Inch diameter, and therefore about double the length of the other, were weighed in a vessel of Water by a pair of Scales, with the Superficies of each just even with the Superficies of the Water in the vessel, they will each lose a just equal portion of their weight by the thickness of the medium, and will still hold their aequipondium, yet the imagina­ry column of Air impending upon the two Inches Cylinder above treble the weight to that impending upon the one Inch diameter, and here is no recoiling Column of Air to sustain them.

But I easily foresee the Answer to this Instance, and therefore I gave it to let in what I have to say; for it will be said, that the Gravitation of the Air upon the residue of the Water, gives a greater concrete weight to the Water, by so much as the Column of Air, commen­surate [Page 76]to the Superficies of the Water, adds to it, and so both Air and Water make one common pressure, and conse­quently the recoiling or sustaining Co­lumn of Water, hath as great a potentia sustinens as the weight of both put toge­ther can contribute. But to avoid this Effugium, sirst I took two Brass Cylin­ders, weighing each four pound, but one of double the others diameter, I took then two Laton-Tubes of 6 Inches dia­meter, and about two foot in length, closed at both ends, only in the centre of the close Cover of the one I caused a hole to be made, commensurate to the Superficies of the Cylinder of Brass of 2 inches diam. & a like hole in the other, commensurate to the cylinder of Brass, of 1 Inch diameter, so that they might just play upon them without any considera­ble distance between the weights, and the concavity of the holes. I then filled the vessels brim full of water, & weighed the Cylinders with their Superficies just equal with the Water and Cover. Here could be no Gravitation of the Air upon any part of the Water, but only upon [Page 77]the Weights, so that the Column of Air, pressing upon the greater Weight, being, as is supposed, above treble to what presseth upon the less, must needs drive it down, because the recoyling Pillar of Water, could not counter­vail such a disparity of pondus of Air.

And yet I found not above one Grain odds in their Weights, the broader weighing about a thin Groat more than the narrower.

But because I would have no evasi­on, by supposing that that small di­stance between the Weights and the Hole, might give some more help and strength to the sustaining Pillar of Wa­ter by letting in some Air to lean upon the Water, thereby to enable it to keep the Equipondium. I took a very flat peece of Lead, with a hole in the Cen­tre, no bigger than would let through Freely that small Packthrid that suspen­ded the Weight, and letting the Thrid through the hole, and pressing the Lead so exactly close, that no Air can pass to press upon the Water and Weight, but just that little passage for [Page 78]the Thrid which impended also in the very middle of the Weight, and there­by covering the Orifice, fitted to the one Inch weight; yet the Equipondium between both, continued exactly the same, as when both holes were left open, one of two Inches, the other of one Inch Diameter, at both times, the Vessels being perfectly full of Water.

And yet according to the supposition, the supposed Weight of the Pillar of Atmosphere impendent upon the two Inch Weight, could not be so little as 200 pound, and the weight of Air, pressing upon the Centre of the lesser Weight, and no where else, being not a quarter of an Inch Diameter, could not in proportion, weigh the 100 ^th part of 200 pound, according to the suppo­sition of this new Philosophy: And all this while the entire Superficies of the Water, discharged of all manner of Gravitation of superior Air, by the close cover that every where covered its Supersicies.

I do not understand what evasion can be made, unless they will suppose that [Page 79]the little hole for the Thrid, might by a strange Contagion, infect the entire Body of Water, with a new Gravitati­on, which nevertheless is so impossible, that it deserves no other answer than what our common sense allows; for this little pertuse, letting in that little Column of Ayr of a quarter of an Inch Diameter, impends not upon the Water, but is wholly received by the Brass Weights, upon whose Centres it leans.

So that the imaginary repercussive Column bearing up the Body into an Equilibrium, with the impendent Co­lumn of Air (admitting the Air should have such a Gravitation downward) must needs be a fiction upon a fiction, and therefore upon the whole matter laid together, both are fictions, and nei­ther true.

2. But yet farther, if such a pressure upward of the inferior, or (as I have called it) the recoyling Column of Air should be admitted, it doth wholly de­stroy the supposition of Gravitation of the superior Column of Air, because [Page 80]in truth it renders the superior and in­ferior Columns of Air in a perfect aequi­librium, every lower portion of Air checking and counterpressing the su­perior, with the same strength or poten­tia sustinens, that the superior portion chargeth the inferior with a pondus de­primens.

( Fig. 5.) For suppose in the 5 ^th Fi­gure A B were a Cylinder or Column of Air, reaching from A the Supersicies of the Atmosphere, to B the Superficies of the Earth, and of 12 Inches diameter. If the portion B E F press with an equal potentia upward to the portion A E F, pressing with an equal weight down­ward; then these two portions of Air must be at rest, and in aequilibrio, and so far every divisible part of every other portion of the entire Column. And if the superior and inferior parts of the Air be by this means in aequilibrio, there can be no more Gravitation downward than upward; for all motion must arise from a disparity of weight and weight, or power and power, or power and weight. And therefore it is that al­though [Page 81] one Scale be charged with a hundred pounds weight, and the other Scale be charged with as much, the Scales will be at rest, because in aequili­brio; and by the advantage though but of a Grain of weight, added to one Scale, they will be put into motion, but not 'till then.

But then it will be required to make out that, upon the Supposition, that in our first Instance the greater Scale is kept in aequilibrio by the pondus of the superior, and the potentia of the inferior Air; that there will be the same aequi­librium between the pondus A E F, and the potentia E F B, upon or in every ima­ginary Superficies of the Column of the Atmosphere; as E F C D, or any other imaginary superficient, interja­cent between the top of the Atmo­sphere A, and the Superficies of the Earth at B.

And surely there need not be much pains taken to prove this: for it is not the interposition of the Scale that makes the aequilibrium, but it is the coun­terpressure of the superior and inferior [Page 82]part of the aerial Cylinder, which must needs be as effectual, and of the same kind and strength, if that Scale were removed out of the way; for though the interposition of the Scale hinder the contiguity of the upper and lower Cy­linder, yet it contributes nothing to the Gravitation of the one, or pressure upward of the other.

Upon all which large digression, it seems to me that their very answer given, that the equal Gravitation of each Scale, the greater and the lesser, is by the equal pressure, viz. by reason the greater Scale as it is pressed by a greater aerial Cylinder, is also supported by a reversed or recoiling Cylinder of Air of equal sustaining force, though not of equal length with the superior, de­stroys totally their whole Supposition of the Gravitation of the Air, and ren­ders their contrivance of the investiga­tion of the weight of the Atmosphere, by the aequipondium thereof, to a Cylin­der of 29 Inches of Mercury, utterly ineffectual.

And this it seems to me must be ad­mitted, [Page 83]namely that the inferior Cylin­der of Air recoiling and returning from the Earth, or any other solid Base, doth in truth sustain the impending pondus of the same Cylinder, and so there is an aequipondium in any given or imagi­nary Superficies of Air between the pondus deprimens and the potentia susti­nens, in the same perpendicular Pillar or Column: and so the Air becomes not heavy in it self, but yet that it gravitates entirely upon the Base, which is as it were the common hypomoclian that re­ceives the impression of the impendent Air, and remits the potentia upward in counterpoise to it.

But then they say, that where in that Pillar of Atmosphere the Contiguity between the superior and inferior Co­lumn is interrupted by some interve­nient body: as in the first instance, by the intervention of the Scale the aequi­pondium between the pondus deprimens, and the potentia sustinens of the aerial Pillar, is wrought by another means, namely the imaginary Pillars of Atmo­sphere circumjacent to that intercep­ting [Page 84]body: as suppose the three Co­lumns of Atmosphere A M B N C O, and the Column B were cut off at D by any solid body (suppose the Scales, in the first instance;) yet the two adjoin­ing Columns gravitate upon the infe­rior Pillar of Air (suppose it transverse,) and so give it as vigorous a repercussion as if it were in the same perpendicular Column: as in the figure,

Suppose B H be a Column of Air, im­pending upon the cube H, of six Inches square; H to be (for instance) a cube of Brass, some way there sustained; E N be the subjected Column of the same base, resting upon the Superficies of the Earth at N. Suppose also A D m, and C F o, be two lateral Columns of Air, pressing g upon a lateral or transversal Pedestal of Air G I K L, upon an imagi­nary Superficies, contiguous to the lower Base of the cube H, namely G D F I; here the Cylinders H D and C F press so strongly upon the entire transversal Base G D E F G K L M N O, that the por­tion thereof E N is so strongly bound together, compressed, and fortified by [Page 85]the columns A D and C F, that it su­stains the cube H as forcibly as it would have sustained B H an entire Column of Air, and so makes an aequipondium and sustentation of the cube H.

( Fig. 6.) To examine the truth of this Supposition, let us suppose in this, A to be the base of the cube B C D, and E to be the bases of four Pillars or Co­lumns of Air, contiguous to the four sides of this cube, equal in Base to it, and all these Bases, both of the cube A and of the four collateral Pillars of Air, to be upon the Superficies of the Earth. If A be removed higher, as to H in the former figure, the intermediate space between H (in the former figure) and the Superficies of the Earth, viz. the space H N, must be furnished with Air; now the Air, that must supply that space, cannot be immediately thrust in from the Pillar superior to the cube, viz. H B, because the descent of that Pillar of Air is obstructed by the interposition of the cube H, whereupon it is bot­tomed. Therefore of necessity each of the collateral Pillars of Air, B C D E, [Page 86]must thrust in an equal portion of their stock of Air, to supply the interstitium of H n in the former figure; and then they will want so much of their Pillar, as will make good what they have thus contributed to fill that space. And this they are to borrow from the Pillar H B, that lay perpendicular to the cube, which now at this Elevation is B H: for as the cube it gradually raiseth from N towards H, the Pillar of Air incum­bent upon it must be displaced, and what is so displaced, must be thrust into the lateral Pillars B C D E, to supply what they contribute to the relicted space H N: and so in every Elevation higher of the cube H, so much space as it leaves, must be immediately thrust in from the collateral Pillars adjacent to the Tube, and must be made good in the same moment from the Air, thrust out of the perpendicular Pillar B H, by the gradual Elevation of the cube to supply the collateral Pillars. By this process of one part of the Air into ano­ther, to accommodate the motion of its parts, it seems evident, that there is not [Page 87]that pressure of one part of the Air upon another, nor of all upon the common Base, that should be like so many Wed­ges to keep every portion of Air just in that place it hath; or by Gravitation of one part upon another, to keep all the parts so tight one to another, as the Supposition imports. For then certainly there could be no motion or transmi­gration of one part of the Air into ano­ther, as we see there is not only in the Instance above given, but in a thousand more. The most forcible Winds could no more remove one portion of Air out of its place, then they could remove a Pyramid of Memphis, if this Sup­position were true.

Therefore there seems to be very lit­tle ground for the late Masters of Expe­riments, to lay any weight of proof for their supposed Gravitation of the Air, upon the Torricellian Experiment; which, by what I have said, and shall hereafter say more at large, depends upon a clear other Solution.

And thus far in general, touching the Gravitation of Air in Air, or upon [Page 88]any other Bodies; wherein I have been the longer, because I shall perchance hereafter have recourse to some of the things said in this Chapter.

CHAP. V.
Concerning the Gravitation of heavier Fluids upon those that are lighter.

THere be those that contend, that there is no Body positively light, but only comparatively; and that the Ascension of any Bodies is not from the intrinsick nature or quality of the Bo­dies themselves, but because others that are more heavy than those are, and more vigorous in their descent, do drive up those that are less heavy, by taking their places, and so force them to mount higher.

Whatever may be said in this respect, in relation to Air, yet surely it holds true in other grosser Fluids, and some­times in solid Bodies also: Oyl is truly heavy, and yet driven higher by Wa­ter, [Page 89]which is ordinarily heavier than Oyl. And the same is true in relation to Water and Mercury, the latter dri­ving up the former though a heavy Body, because not so heavy as Mercury. As I have before said, there is a double Disparity or aequipondium of heavy Bo­dies; one in relation to their intrinsick of specifical weight, another in relation to the external or quantitative weight. Water is specifically heavier than Oyl, and Mercury than Water; whence it comes to pass, that a bulk of Mercury weighs more than a bulk of Water equal to the bulk of Mercury; one square Inch of Mercury, counterpoising neer 14 square Inches of Water. But yet the bulk or quantity of Water may be so much, or so great, that it may overpoise the Mercury, two ounces of Water ne­cessarily being more, and weighing double to an ounce of Mercury, though specifically heavier than Water.

And therefore in the consideration of the gravitation of heavy Fluids upon lighter, we are to take these two parts into consideration. viz.

1. The Gravitation of a Body, spe­cifically heavier, upon or in a Body spe­cifically lighter; as the Gravitation of Mercury upon Water, or Water upon Oyl or Air.

2. The Gravitation of a Body spe­cifically lighter, yet in quantity or ex­trinsically heavier than the Fluid it presseth; as two pound of Oyl upon a pound of Water, and the like.

As to the former of these, there seem to be four ways, wherein the Gravitati­on or pressure of a Fluid upon a Fluid, specifically lighter, sensibly is exercised. viz. 1. By way of Penetration, 2. by way of perpendicular, or other descen­ding Depression, 3. by way of lateral Pressure, 4. by way of Elevation of the lighter Body.

For the first, if a cube of 12 Inches square be filled 9 Inches with Oyl, and the other three be filled up with Water; though for the present the Water gent­ly poured on will flote upon the Oyl, yet in a little time it will penetrate through it, and get under it, and the 9 Inches of Oyl will swim upon it, pres­sing [Page 91]its Superficies equally every where.

And so if a lumen be at the bottom of the cube, the Water first, and then the Oyl, will gravitate upon the Air, and press through it.

But if the top of the cube be closely covered, so that Air cannot get in above the Water, the Oyl will not descend through the lumen, the reason whereof is hereafter explained.

For the second, it is very plain, that the heavier Fluid will in some Instances press upon all the lighter, by a depression where it can have way; sometimes im­mediately, sometimes mediately, viz. notwitstanding the interposition of an­other body. For instance,

If an empty Bottle or Glass-bubble be placed in a vessel of Water, at a small depth, the Air included in the Bottle or Bubble, being a Body lighter than Wa­ter, will mount up to the top, if it be not kept down: for a small pressure of Water, though it press upon the inclu­ded Air as much as it can, yet it cannot compress the Air so much, as to drive into it a quantity of Water, that may [Page 92]make the Bottle and included Water equal in weight, or more in weight than the like bulk of simple Water; but if more Water be poured into the vessel, whereby a weight of Water incumbent upon the narrow mouth of the Bottle or Bubble, is sufficient to compress the included Air, to such a contraction, as may admit Water enough to make the Bottle, with the admitted Water, to counterpoise more than a like quan­tity of simple Water, the Bottle or Bub­ble will subside, and sink to the bottom again; if the vessel be unladen conside­rably of its Water, whereby the Air included in the vessel being under a less pressure, can expand it self to its natu­ral dimension, and thereby thrust out of the Bottle so much of the included Wa­ter, as may render the Bottle, with the included Water, lighter than a like quantity or bulk of simple Water, equal to the bulk of the Bottle, the Bottle will emerge again.

This is the Experiment mentioned by Shottus, in his Magia hydraulica, par­te 3, l. 5, problem. 3. and the excellent [Page 93]Author of Hydrostatical Paradoxes, pag. 16, 53, 153. and elsewhere. The Ex­periment is certainly true, but the So­lution thereof, and the Conclusion de­duced from it, of the Gravitation of the upper parts of the Water upon the low­er, is as I think wholly mistaken; for the reason of it is not from the imagi­nary Gravitation of Water upon Wa­ter, but of Water upon Air, which be­ing a lighter body than Water, and ca­pable of compression into a narrower compass, by the Gravitation of Water upon it, sustains that weight of the Wa­ter, and is compressed by it, and under it: it is not an effect of Gravitation of Water upon Water, which is of equal intrinsick or Specifical Gravity, but of Water upon Air, which is a lighter Fluid, and compressible. Again, this Gravitation of heavier Fluids upon lighter, though not immediately conti­guous, is plain by this instance.

If a Cylindrical vessel of Water be of 6 Inches diameter, and there be a rundle of Wood specifically lighter than Water of five Inches ¾ diameter [Page 94]placed at the very bottom of it, the Water will drive it up to the Superfi­cies of it, because it is a Body specifically lighter than the Water. But if there be a hole of five Inches diameter in the bot­tom of that vessel, and the Rundle be placed upon that hole, so that it some-what overlaps the hole, so that the Wa­ter cannot pass out of it, and then it be filled up with Water; the Rundle will gravitate upon that hole, and the in­cumbent Cylinder of Water, commen­surate in Base to that Rundle, so hard and close, that it requires a weight in a pair of Scales, neer commensurate to the weight of the impending Cylinder of Water, to raise it from the bottom; and the reason is, because the Rundle being the Operculnm of that hole, through which the Water should pass into the lighter Fluid, the Air, and so is the impediment of the Waters pas­sage, it gravitates upon it, because it hath mediately a lighter Element upon which it gravitates, namely the Air. It is Stevinus his Experiment, in his pra­ctical Hydrostaticks, upon his 10. Pro­position.

And upon the same reason it is, that if a Glass-bottle filled with Sea-water, and stopped, be let down twenty fa­thoms into the Sea, it will not break, for it is filled with a Fluid of an equal weight, and so the external Water doth not sensibly gravitate upon it, for it hath within a sufficient power to resist the external pressure. But if it be full only of Air, and stopt, and let down as deep by a weight appended to it, (as it must) it will be broken by the pressure and weight of the Water immediately upon the inclu­ded Air, which is lighter than so much Water, and so it presseth upon it, to drive it up, and crusheth the glass into it.

And this I take to be one reason, though not the only reason of the Experiment of the Valve, and likewise of Oyl thrusting up Water into a Tube, though of a speci­fically heavier consistence; and possibly may contribute something to the in­stance in the fourth Chapter, whereby a Syphon filled up with Mercury to the hight of the shorter leg, and immersed in Water, the Mercury in the shorter legg will subside a little, and ascend in the lon­ger [Page 96]leg, although the Mercury be a Body 14 times heavier than Water; for in these instances, though the immediate contiguity be of the heavier Body to the lighter, as Oyl to Water, and Water to Mercury, yet in as much as the Mer­cury in both leggs is in aequilibrio, and the Air is behind the Mercury in the longer legg of the Syphon, and behind the Water in the Tube, the Water in the one case, and the Oyl in the orther, doth in truth gravitate upon that Air mediately and effectively, rather than upon the intermediate heavier. Fluid, especially if the body of the Air be any whit lower than the Superficies of the Water.

And thus far touching the Gravita­tion or pressure of a Fluid specifically heavier, upon a Fluid specifically lighter. I should now come to consider the pres­sure of a Fluid specifically lighter, yet with an excess of extrinsick or quantita­tive weight upon a Fluid specifically heavier; as two pound of Water upon a pound of Mercury, or two pound of Oyl upon a pound of Water: but be­cause [Page 97]this and some other considerati­ons, for the better clearing of the mat­ters contained in this Chapter, may oc­cur in the next, I shall remit it thither.

CHAP. VI.
Concerning the Pressure or Gravitation of lighter Fluids, upon those that are spe­cifically heavier.

IT is certain, that every Body, whi­the fluid, or solid, incumbent upon another, though that Other be a thou­sand times intrinsically and also extrin­sically heavier than the incumbent Bo­dy doth gravitate and press upon it.

And therefore if we should suppose the Air to have a weight, but a thou­sand times less than the like portion of Water, a portion of one square foot of Air incumbent upon the Ocean, would have some pressure upon it: some­what like the Problem that passed in the Affirmative among Fresh-men in the University, That if a Horse had as much as he could carry, the addition of the weight of the thousandth part of a Fea­ther [Page 98]would break his back.

But this is not the pressure or Gravi­tation I am speaking of, but such a Gra­vitation or pressure, as would put the subjected heavier Fluid into a sensible motion, or change of place or situation.

In a pair of artificial Scales, a pound of Feathers or Water, will equiponde­rate a pound of Gold or Mercury, and 2 pound of Feathers will preponderate a pound of Gold or Mercury, not withstan­ding the great disparity of their intrin­sick weight.

And so in a Ballance that seems more natural, if a Syphon of half an Inch dia­meter, with one legg of six Inches long, and the other of thirty four Inches long, or more, be filled with Mercury to the height of the shorter legg, and then stopping the Orifice of the shorter legg with the finger, fill the longer legg with water, and then opening the Orifice of the shorter legg, the Water in the longer legg, though specifically lighter than the Mercury, will drive out the Mercury out of the Syphon, be­cause the extrinsick or quantitative [Page 99]weight of so much Water exceeds the extrinsick or quantitative weight of the subjacent Mercury.

If a cubick vessel be filled six Inches high with Water, and a Glass-pipe open at both ends be immersed at one end in the Water, and then superinfuse gently (to avoid disturbance) so much Oyl as will fill it up ten Inches, viz. four In­ches of Oyl, and six of Water, the Pipe will be filled with Water neer to the le­vel of the Superficies of the Oyl, but not quite level to the Superficies of the Oyl, it will want so much, as the like quantity of Water in the Pipe, is heavier than the like quantity of Oyl.

But if a Pipe filled with Oyl, and the upper end stopt with a finger, whereby the Oyl remains suspended in the Tube, or Pipe, and then the open end be im­mersed in the Water, the Oyl, while it obtains a Superficies in the Pipe consi­derably higher than the Water in the vessel, will subside 'till it come to such an Elevation above the Superficies of the Water, as is proportionable to the degree of specifical Lightness that it [Page 100]obtains more than the like quantity of Water. And 'till then it subsides into the Water, because it hath a greater proportion of accidental weight by its so great Elevation above the Supersi­cies of the Water: for the Elevation of one fluid body above another, gives the greater strength and swifter motion to its descent: whereby though a ligh­ter body, it conquers the resistance of the Water of a lower Superficies.

Which is the reason, why a Tube of Water, four foot high, casts out more Water in the same portion of time, through the same lumen, than a vessel of the same diameter, and but two foot high, as I shall hereafter more at large observe.

And this is the reason, why if a small Glass-Tube of six Inches long, be filled with Water, and the upper end being stopped with the finger, whereby the Water is suspended in the Pipe, and then the lower end being immersed in a vessel of Water six foot deep, and then the upper end unstopped, the whole Water in the Pipe will empty it self, [Page 101]'till it attain a Superficies equal with the Water in the vessel, and will not be kept suspended in the Pipe by the resistance of the Water in the vessel, because if it obtain never so little more height in the Pipe than in the vessel, it hath a grea­ter force to press downward, than the Water in the vessel hath strength to re­sist it.

If a Tube stopt at one end be filled with Mercury, and inverted in the open Air, the Air will ascend and terebrate through the Mercury as fast as that de­scends; so there is a kind of pressure of the Air ascendendo upon the Mercury, and thereby both the Air and Mercury obtain their several natural motions, this descendendo, and that ascendendo, whereby Vacuity is prevented, and the continuity of the parts of the Universe preserved.

But if the Tube be very small, so that the Air cannot make its way through the lower orifice, to gratifie the Mercu­ry with a descent, by that means the Mercury will remain suspended in the small Tube, and will not descend. The [Page 102]like will happen, if such a small Tube be inverted into Water, the smallness of the orifice not admitting the ascent of the Water to supply the space derelicted by a descent of the Mercury, the Mer­cury by force of the Catholick law of Nature will remain suspended, and its natural descent will be thereby super­seded.

So that the pressure or Gravitation of a lighter Body upon a more gross and weighty, will be occasioned, 1. Either by the Excess of the quantity and ex­trinsick weight of the Fluid specifically lighter, or 2. by the advantage of its Po­sition or Elevation above the Superfi­cies of the grosser Fluid, or 3. by the interposition of that common law of Nature, ut evitetur vacuum.

I shall conclude these general Obser­vations, touching the Gravitation of Fluids, with that of the Valve, descri­bed by the Excellent Author of Hydrosta­tical Paradoxes, cap. ultimo, which was certainly a most ingenuous Experi­ment, though I am not at all satisfied with the Solution he gives of it, nor the [Page 103]Consequences deduced by him from it, touching the Gravitation of Water upon Water, (I mean sensible Gravita­tion) of the superior parts upon the in­ferior parts of the Water in free water.

And I am as much dissatisfied with that obscure Solution that is given thereof by the Learned Author of the Enchiridion Metaphysicum.

And because in this one Experiment duly observed and improved, many of the most abstruse Conclusions of Hy­drostaticks may be cleared even to sense, I shall distinctly examine it, and the phae­nomena appearing in it.

The Instrument is thus made, accor­ding to that form which I made use of.

I took a hollow Tube of Laton, close­ly sodered at the Sides and joynts, of 39 Inches long, two Inches ½ in the dia­meter from the top to the bottom, with a Brass Valve at the end of it sodered to it, and a brass Sucker or Cover of the same fashion with those used in Pumps, only in Pumps the Cover or Sucker hath its head upward, in this Instru­ment the head is downward, whereby [Page 104]it being inverted it falls out about an Inch below the Valve, but cannot fall out more, because stayed by the Frame of the Valve.

Fig. 7. This Sucker exactly covers the mouth of the Valve, that no water can come in, when the Sucker is closely strained up, by a string fastned to it in the inward pin of it, and so conveyed up through the Tubes. The Sucker thus fastned to the Valve or Box, and the Box soder'd close to the Tube, and the string conveyed up through the Tube to the open end of it, the Engin is formed according to the Figure in the Margin, representing A the Tube, B the String, C the brazen Box of the Valve soder'd to the Tube, D the Sucker or Cover of the Valve let down as low as it will go, with a Hook to hold any weight appended to it; which Sucker being strained up with the string, close­ly stops the lower orifice of the Tube, and Box of the Valve.

The Valve thus prepared, I strictly weighed the whole Valve, Tube, Sucker, and Thrid, with the wooden [Page 105]Nut upon which to roll the string, which weighed in all three pounds, two ounces and a half, or 50 ounces and a half.

The Sucker (for so I shall call the name of the Valve) weighed seven oun­ces and one half: and I was curious in weighing these things, because the great use of my Experiments consisted in the comparison of weights of the Instruments themselves, and the Water.

I took then a great glass Tube, of a­bout five Inches diameter, and about two foot and a half long, and filled it with Water; though I used also a Leaden vessel of six Inches diameter, and four foot long, for the immersion of my Valve, which though it were deeper, yet the Glass vessel was more ac­commodate to my use, and served as well, and therefore I used it, and there­upon made those several Trials.

( Fig. 8.) 1. The Tube let into the Water, with the Valve open, would freely subside to the bottom of the Wa­ter, be it never so deep, the water get­ting up into the cavity of the Tube: for [Page 106]the moles of the Tube in that instance, is no more than the length and thickness of the Laton, the Brass Valve and Sucker; but the weight thereof being more than such a single moles of water, it must necessarily subside to the bottom of the water.

2. The Valve being drawn up, and sustained by the Thrid wound about the wooden Nut at the top of the Valve, whereby no water could come into the Tube, and then left freely to subside in the water, would subside to a depth of one and twenty Inches, and so swim erect in that depth of water, one and twenty Inches being immersed in the water, and eighteen Inches of the Tube being in the open Air, above the Su­perficies of the water.

And the reason is, because though the Laton and Brass be specifically hea­vier than Water, and therefore will sink, as in the last Instance; yet because now the Tube sits upon the water, as one entire Cylinder, and a Cylinder of Laton thirty nine Inches long, and two Inches ½ broad filled with Air only, is [Page 107]not heavier than a Cylinder of Water of one and twenty Inches long, and two Inches ½ diameter, but do equiponde­rate; therefore the Tube sinks no lower than one and twenty Inches to make an aequipondium between it self and the like bulk of Water.

3. I therefore with all the exact­ness I could, measured the weight of the Water commensurate to a Cylin­der of two Inches ½ diameter, and one and twenty Inches long, (the quantity of the Tube swimming in the Water.)

First therefore filling my Glass Tube very full of Water, I immersed the Valve open into one and twenty Inches deep; then at that depth lifting up the Sucker, and inclosing the one and twenty Inches of Water thus impri­soned in the Tube, and so taking it out closed; and then when out of the Glass Tube setting it to run into a vessel weighed before, I find the weight of the included Water weighed fourty and seven Ounces and half, or three pound wanting half an Ounce, which is about three Ounces less than the weight of [Page 108]the whole Instrument. And this abate­ment it hath for the thickness of the Tube and Valve, because the water that is pressed upon by the Tube and Valve, and so raised out of its place, is pressed up by the convex or outside of the Tube and Valve, and commensurate to it.

Therefore again straining up the string of the Valve, whereby no water could get in, and filling my Glass Tube of restagnant water to the very brim or brink of the Glass, and then I immer­sed my Tube into the water to one and twenty Inches depth; the Valve strai­ned up by the string, and preserved the water that was impelled up by the im­mersion, and thrown over: and this I likewise exactly weighed, and found to weigh near upon the point of fifty one Ounces ½, or three pound three Ounces and half, which is about an Ounce more than the weight of the Engine; which disparity might happen for want of ex­actness. But the summe of it is, there is no considerable difference between the weight of the whole Engine, and the weight of so much Water, as will [Page 109]countervail in quantity to so much of the Engine or mingled Cylinder of 21 Inches thereof immersed in water.

Which gives us a plain account, why and how much a Body lighter than the like quantity of water, will sit a­bove water, and why, and how it comes to pass, that some Ships draw more water than others, and how much bur­then they will bear, before they will sink, viz. if the Ship or Barge with all its Cavities and Lading, be not heavier than such a solid bulk of water, as equals the whole Moles and Cavity of the Ship or Barge, the Barge will live, though it draw water neer to the very top of the sides of the vessel. And if the Ship or vessel be lighter than such a moles of water as equals the whole con­tinent of the Ship or Barge, so much of the Ship or Barge will emerge above the water. For in the instance in hand, in as much as 21 Inches of immersion of the Tube, was the product of its whole weight of three pound, two Ounces and half; and those one and twenty Inches thus immersed, were [Page 110]equal in weight to a bulk of Water, commensurate to that Cylinder of 21 Inches immersed, the rest of the Tube viz. 18 Inches, did flote erect upon the Water; for if it should have subsided, the moles of Water lifted up out of its place would have exceeded the weight of the whole Valve, viz. three pound, two Ounces, and half, which by the rules and Laws of Hydrostaticks it may not do,

4. If the Sucker be drawn up, and then immersed so low, that the portion of Water impelled up by the Tube, do exceed the weight of the Sucker, viz. 7 ounces and half, the Sucker will be sustained by the pressure of the Water upon it: as suppose in the 8 ^th Figure it were pressed even to L M, or N O, which is nine Inches below the Superficies of the Water. And the reason is, because the Sucker is now the moveable Basis of the included Column of Air, which is a light Body, and so gravitates no­thing upon the Water; and the Sucker being as it were the Basis of that Co­lumn, and moveable, weighs but seven [Page 111]Ounces and half, and the Tube subsiding as low as L M or N O, presseth up a portion of Water of double that weight, and this portion of Water bears against the Base or Sucker more forcibly and powerfully than the Sucker can bear against it.

5. But if the weight of a moles of Water, commensurate to so much of the Tube as is immersed in the Water, be less than the weight of the Sucker, the Sucker by its own weight will sub­side, notwithstanding its immersion in­to Water.

By iterated Trials I found, that if I kept up the Sucker by the Thrid, and immersed it to ten Inches, or more, and let go the string, whereby the Sucker, though now at liberty, would yet not subside, but remain suspended by the pressure of the Water upon it; yet if I gently raised it up, 'till it came only to an immersion of four Inches and half, the Sucker would subside; wherefore closing in the included Water at that depth, by lifting up the Thrid, and so closing the Sucker, I weighed that in­closed [Page 112]Water, and found it just weighed as much as the Sucker, viz. seven Oun­ces and half, and there could be no con­siderable odds here by the thickness of the Tube, the immersed portion thereof being butsmall, and the sides very thin.

6. But because I would pursue the proportion to the uttermost, I kept up the Sucker with the string, 'till the Tube came to the immersion of four Inches and half, and then subsided; I then inclosed that four Inches and half of Water, and kept up the Sucker, and immersed the Tube with the inclosed four Inches and half of Water, and gent­ly raising it up, it subsided at nine Inches immersion.

And the reason is the same as before, for the included cavity of nine Inches, had in it four Inches and half of Air, which weighed nothing, and four In­ches and half of Water, which as before is shewn, weighs seven Ounces and half, and the weight of the Valve which weighs also seven Ounces and half, the whole weight of the included Air, Wa­ter, and Valve, weighing only fifteen [Page 113]Ounces, and a Column of Water of nine Inches high, and two Inches and half broad, equal to the cavity of the immer­sed nine Inches of the Tube, would have been of the same weight with the four Inches and half of included Water; and the Sucker, whose weight is now to make good the uppermost four Inches and half of Airy space, and so there is and aequipondium between the included four Inches and half of included Water, together with the weight of the Sucker to a Cylinder of Water of nine Inches long, and two Inches and half broad, commensurate to the like cavity of the Tube, and the like quantity of nine In­ches of Water, impelled out of its place by nine Inches of the Tube immersed below the Superficies of the Water.

And the same rule and proportion will hold upon the like quantity of more Water taken in, and a deeper immersion, allowing the same thing for that thickness of the sides of the Tube, which upon a deep immersion is more considerable than upon an immer­sion of four Inches and half.

7. And although I did not make an actual trial how much weight in an empty Tube, deeply immersed, would be sustained by the Sucker without sub­siding; yet by this proportion it is easie to be calculated, viz. that the Tube be­ing kept empty, and immersed to any depth below four Inches and a half, the Sucker will sustain without subsiding such a weight, as is equal to a portion of Water commensurate in bulk to so much of that empty Cylinder in the Tube, as is depressed below the Superfi­cies of the vessel of restagnant water.

So that if the empty Tube will sustain seven Ounces and half (the weight of the Sucker,) at four Inches and half im­mersion, it will sustain fifteen Ounces at nine Inches immersion, thirty Ounces at eighteen Inches immersion, sixty Ounces at thirty six Inches of immer­sion; for an empty Cylinder of thirty six Inches long and two Inches and half broad, will contain a Cylinder of Wa­ter of sixty Ounces weight, allowing somewhat as before, for the thickness of the sides of the Tube.

8. In this it appears that the Water doth not gravitate upon the Water, but gravitates upon a Body lighter than it self, though this Gravitation be im­mediately upon a Body as heavy or hea­vier than it self. When there is nothing but Air in the Tube, the Sucker is the moveable Basis of that Air, and it gra­vitates immediately upon the Sucker, but mediately and remotely upon the Air above it, when there is a little co­lumn of Air in the top of the Tube, and below the Superficies of the Water, and under that a column of Water, and un­der that the Sucker. If the whole Con­crete be lighter than so much Water, it gravitates upon the Sucker, Water, and Air, because though the Brass be specifically heavier than Water, and the Water over it specifically of an equal weight with Water; yet the quantita­tive or extrinsick weight of both is less than the weight of so much Water as is equal to a Bulk or Cylinder of Water, entirely commensurate to the quantity of the Air, Water, and Sucker, below the Superficies of the Water.

9. That when a Body lighter than so much water is within the compass of the Superficies of the body of restagnant water, the water presseth upon it up­ward, impelling it up, as here upon an immersion of the Valve laden with four Inches and half of water, and likewise with the weight of the Sucker, into nine Inches of water, an equal quantity of water to the moles of the immersed Tube, viz. nine Inches sustains the Sucker, notwithstanding its own weight and the weight of four Inches and half of water incumbent upon it, because those two weigh but fifteen Ounces, and nine Inches of the exterior water weighs as much, and so there is an aequi­pondium between the potentia sustinens, and the pondus deprimens.

CHAP. VII.
Concerning the Space derelicted by the de­scent of the Mercury in the Torricellian Experiment, and what it is not, or what it is that fills it.

HAving gone through the two pre­mised Considerations, prelimi­nary to this Inquiry, I now come to the third General, namely what it is that fills the space derelicted by the descen­ding Mercury in the Tube. And first I shall consider, whether it be a Space purely void of any Body. 2. If it hath some Body that fills that Space, I shall consider what it is not that fills it. 3. I shall consider what it is that most pro­bably may be thought to fill it.

First therefore I say it is not Nothing, or a pure Vacuity, but it is some cor­poreal substance that succeeds in the head of the Tube, derelicted by the Mer­cury.

And here 1. I shall not enter into [Page 118]any large debate touching the possibili­ty or impossibility of interspersed or coacervated vacuities in any parts of the Universe; neither 2. shall I insist upon those obscure evidences of the in­existence of a Body in that derelicted space; as namely the communication of Sounds, or the reception of Light, or transmission of Colours, or other vi­sible species in or from it. But 3. I shall ground my Conclusion from those more sensible and apparent Phaenomena which do evince it; namely, those sensible plain Effects in that seeming empty Space, which could never be produeed but by the contiguity and presence of some corporeal substance, filling that supposed empty space.

1. It is most evident to any man's sense that will but try it, that if the Tube be open at both ends, and filled up with Mercury, and then one end stopped with the finger, and the other end inverted and immersed in the restagnant Mer­cury, whereby it descends from the top of the Tube, a strong and sensible At­traction is wrought upon the pulp of [Page 119]the upper finger that closeth it, which continues and grows more and more forcible, sensible, and evident, the farther the Mercury is removed from the upper end, and approaching to its usual station of 29 Inches.

This Attraction is impossible to be without the contiguity of some Body to the pulp of the finger, which cannot be the Mercury it self, for That in a Tube of four Foot long is removed a­bove a Foot distant from the finger, by that time it comes to its station; yet all this while the strong suction upon the pulp of the finger continues.

And they that go about to tell us, that it is not Attraction or Suction by any power within the Tube, but by the pulsion of the incumbent column of Air, need no other confutation than their own sense to assure them the con­trary; for most evidently the force that the finger feels is from within, and not from without: and this Solution by Pulsion, is given only to gratifie that imaginary Supposition that some have entertained of the Aery Column, where­of in due time.

2. The instance of Hanoratus Fabri in the 6 ^th of his Physical Dialogue, (though not tryed by myself, yet asserted to be tryed by him) puts it out of question. If at the upper end of the Tube there be fixed a folded Paper, which may be extended by any force, but otherwise contracting it self (in the manner of Paper-Lanthorns made by School-boys), this plicat a charta will by the subsiding of the Mercury be unfolded and exten­ded, which could not be, but by the contiguity of some Body unto it.

3. The instance given by Linus, and improved by Fabri, ubi supra, of an emp­ty Bladder close tyed, and fastned to the upper end and the inside of the Tube, extended after the descent of the Mer­cury, and again contracting it self to its former dimension by the inclination of the Tube, makes it plain, that this Extention is the effect of some included Body in that relicted space, which is not the bare gross body of the Mercury, which is removed a Foot or more below it, and in which there is not so much as pretended to be any Magnetick qua­lity [Page 121]in relation to the Bladder.

And they that tell us it is the Elatery of the Air included in the Bladder, that extends it by a natural expansion, tell us an invention fitted to serve the Suppo­sition of the prodigious natural Elatery of uncompress'd Air, whereof hereaf­ter.

It is true, that if this Bladder hath any little orifice, or hole open in it, the distention will not ensue; but the rea­son thereof is evident, (not upon their Supposition of the impediment of the natural Elater of the Air included in the Bladder,) but because in that case the Attraction is made as well upon the inside of the Bladder through the orifice, as upon the outside, and so the Bladder obtains the same consistence as at first; but where there is no orifice, the Attraction can only be but upon the outside of the Bladder, upon which there necessarily follows an Extension of the Bladder, and a necessary Conse­quent thereof is a Dilatation and Ex­pansion of that little particle of Air in­cluded in it, to the uttermost dilatation [Page 122]that that attractive force can give it, or produce in it, which is not by natural Elasticity, but by forcible Tension.

Upon these and the like sensible and plain Instances it seems undeniable by any, that will not abandon his own sense, that it is not Nothing that is in that derelicted space, but it is some bo­dily substance; for otherwise it were impossible that those, and the like sensible effects could be produced: for regular­ly, all natural bodily effects are wrought by a contact of some Active body up­on the Patient.

CHAP. VIII.
Concerning the Body supplying the derelicted Space in the top of the Tube, and first what it is not.

IN the former Chapter I have conclu­ded, that it is some corporeal Sub­stance in the space derelicted by the Mercury in the top of the Tube, though not conspicuous to the sight: and now [Page 123]I shall consider first what it is not, and 2. what it seems most probably to be.

There are two general Opinions touching it: one that supposeth it is some Body that comes de foris into that derelicted space; and those again fall into several Opinions; some suppose it to be the forreign Air that pervades ei­ther the Pores of the Glass, or the Mer­cury; others that it is Ather, or Ethe­real matter, or (which is a differing kind of Explication of the same thing) that it is des Cartes his materia subtilis, or his Third Element, the ramenta or filings of Atomical Bodies. The other gene­ral Opinion is, that it is a bodily sub­stance, not coming de foris, but arising from the included Mercurial Body.

Now as to the former of these gene­ral Suppositions that it comes de foris, I shall discharge the question from that Supposition of des Cartes his materia subtilis, for there is no probable evidence of any such Principle, it being only an imaginary substitution; and if it be any thing besides imagination, it seems to be but Air, or at most that subtler part [Page 124]of the Universe called Aether, which possibly may be nothing else but the subtler and more refined parts of the Air, disgrossed of those vapours or Efflu­via, which obtain ordinarily in the in­ferior parts of the Air, commonly cal­led the Atmosphere.

And therefore one method of discus­sion of this question will possibly be ap­plicable to both these Suppositions, of the admission of forreign Air or Aether into the derelicted space in the Tube above the Mercury.

If therefore it be forreign Air or AE­ther that occupies that place, it must be upon one of these accounts, viz. either that the Air or Aether, upon the account of its own subtlety and tenuity, freely and of its own accord pervades the Glass or the Body of the subsiding Mer­cury, and so takes up the derelicted room; or else that although of its own accord it would not penetrate through either of those two Bodies, yet that it is as it were forcibly strained through the pores of the Glass or Mercury, and by the subsiding of the Mercury, and the [Page 125]resistence of Nature against Vacuity, percolated into that vacant space.

As to the former of these Solutions, it seems altogether unreasonable to ima­gine any free or unconstrained penetra­tion of the Air, or Aether, into that space: for although the Glass, and like­wise the Mercury are not altogether de­stitute of Pores, yet they do not run in a straight uninterrupted line, but are crossed and obstructed by interposed filaments, that must necessarily stop the free passage of the Air or Aether through them, so that they are not wholly per­vious to those Bodies.

And that this is so, appears by this one instance, which is as good as a thou­sand.

If it were true, that the Air or Aether did freely pass through the supposed pores of the Glass or Mercury, the Mer­cury would never be suspended at twen­ty nine Inches, but would wholly sink into the vessel or restagnant Mercury; for the insinuation of the Air or Aether through the Glass or Mercury, would supply the vacuity, as well below twen­ty [Page 126]nine Inches as above, and so accom­modate the derelicted space in all its E­vacuation, as well as in part, and like­wise would accommodate the Mercury in its natural descent without any in­convenience; and yet we find, that at twenty nine Inches the Meccury keeps up, and subsides not.

And that which puts it out of que­stion, that the natural irruption of the Air or Aether fills not this Space, is this: let but the least orifice, no bigger than the point of a small Needle be made in the top of the Glass Tube, the Mercury would entirely descend, and not be su­stained at twenty nine Inches, because here is an admission of forreign Air to supply the space derelicted by the Mer­cury, as fast as it descends. And the same effect would follow, if the Air or Aether did penetrate through the small pores of the Glass or Mercury. And since we see it doth not obtain that effect, we have reason unquestionably to conclude, it hath not any admission ab extra through those supposed pores of either of those Bodies.

It remains therefore to be considered, whether that by the great contention of Nature against Vacuity, and the for­cible stress of the Mercury on its descent downward, there be not a kind of for­cible straining of some Aery or Ethe­real Particles through the Glass, or at least through the Mercury, which is partly exposed to the external Air.

I answer, first, as touching the per­meating of Air or Aether through the Glass; it seems utterly impossible, for the reason before given. Indeed the vigor of Light or Fire penetrates the Glass, not (as it seems) by any transition of any Corporeal Substance, but only of a vis, virtus, or vigor, which commu­nicates the quality of lumen or calor to the Body that it finds there, but conveys not any Corporeal Substance transmit­ted through the Glass.

Secondly, as touching the supposed straining of the Air or Aether through the Mercury, and discharging it in the summity of the Tube: I must needs say, that in some instances the forreign Air will make a visible perforation and [Page 128]transition through the body of Mercu­ry, as well as of Water.

If a Tube of Glass, sealed at one end, be filled with Water, or Mercury, and then inverted in the free Air, (unless the Tube be extremely small) the Mer­cury will subside and descend by the sides of the Tube, and the Air ascend through it in a Pillar or Bubbles in the midst, in the very same successive order as the Mercury descends; the Mercury thus laterally descending, making way for the ascent of the Air, and the Air in the same successive moments ascending, filling the room relicted by the Mercu­ry: and this ascent of the Air is evident and conspicuous to the Eye.

But in the matter in question, there seems to be no such pervading of the Air through the pores of the suspended or restagnant Mercury.

First, if such a transition of the Air were through the column and restag­nant Mercury, it must needs (as in the former case) make a visible appearance thereof in the Mercury, and raise some tumultuous phaenomena in it, but no such [Page 129]thing appears to the eye in the Torricel­lian Experiment!

Secondly, the difficulty of the transi­tus of the external Air through the Mercury in the Torricellian Experiment is infinitely greater than in the instance above given: for in that instance the Air hath but one motion upward, and is assisted in it by the Mercury giving way to it. But here in the Torricellian Experiment, there must be a double in­tention and motion of the Air, viz. 1. It must descendendo terebrate through the restagnant Mercury, and then when it hath passed that difficulty, it must tere­brate through the erect column of Mercury ascendendo. And it is not con­ceptible that the pores of the erect and restagnant Quick-silver, crossing one another in respect of their position and situation, can accommodate such a crooked and contradictory motion of any particle of Air.

Thirdly, again it cannot reasonably be thought, but that if there were such a transition of the Air through the re­stagnant, and suspended Quick-silver, [Page 130]but it should be as reasonabe to continue after the subsiding of the Mercury to twenty nine Inches, as before, the pas­sage remaining still open through the Mercury. The consequence whereof would be, that the whole Tube would be supplied with Air, and consequently the whole body of Mercury be emptied into the restagnant vessel; as when a little Pin-hole is made in the top of the sealed Tube.

Fourthly, again if it were forreign Air or Aether that were admitted, it is not easily conceptible, how the finger stopping the upper orifice of the Tube, should be attracted inward, or the Blad­der distended, as in the former Chapter; for the immission of forreign Air through the Mercury, or Glass, must rather contract than expand the Blad­der, by the accession of an external com­pression from it, as will happen upon the least hole made in the Tube. Upon these and the like reasons it seems to me altogether improbable, that the de­relicted space should be filled with Air or Aether from without, by an intro­mission [Page 131]of it through the Glass or Mer­cury.

CHAP. IX
Concerning the other Supposition, namely, that this derelicted Space is filled with a Body ab intra.

Since therefore I have concluded, that this derelicted Space in the Tube is filled with a Body, and that That Body comes not ab extra, and there is no Bo­dy within to suppply that room but the Mercury, or that which must be ex­tracted from it: and in as much as the Mercurial consistence it self is descended to twenty nine Inches, it remains neces­sary that this Body that fills the dereli­cted interstitium, must be a subtle body extracted from the Mercurial body. But how, or in what manner this is ef­fected, is inquirable.

And now before I come to the Inqui­ry it self, I must take notice that there are three kinds of instances of the Torri­cellian Experiment.

1. The first is, where the Tube is just twenty nine Inches and half long, and sealed at the top, and then filled with Mercury, and inverted into restagnant Mercury, without any admission of any Air; and though that be difficult to effect, yet if it be effected, there is no va­cant space left, but the column of Mer­cury adheres to the top of the Tube, it being its just station.

2. The second is, when the Tube is above twenty nine Inches and half, sup­pose four foot long, sealed at the top, and filled up to twenty nine Inches and half, and then inverted, whereby the Air ri­seth to the top of the Tube, and the Mercury subsides not only to twenty nine Inches and half, but much lower, namely as far as that column of Air in the upper end of the Tube is by tension extendible by the force of the descension of the Mercury, which being about eighteen Inches of Air, possibly by the descent of the Mercury will be extended to above twice the length, whereby the Mercury may subside it may be to about fourteen Inches, (I am not curious in the Calculation.)

3. The third Instance is, where the Tube for the purpose is four foot long, sealed at one end, filled with Mercury without any portion of Air admitted, whereby the Mercury inverted into a vessel of restagnant Mercury, subsides to twenty nine Inches and half, and so leaves about eighteen Inches deserted by the Mercury.

And though in the pursuit of this dis­course there will be use of the discussion of the two former Instances, yet in this place only the last of the three yeilds the Inquiry, namely what it is that fills that space derelicted by the Mercury.

And I adventure to conclude, that it is a subtle Corporeal Substance extra­cted from the gross Mercurial Body, or forced out of it.

The methods of this Separation are two, the one proposed by Linus, the other offered by others.

That of Linus (if I understand him aright) seems to be this: namely that by the descent of the Mercury, and in obse­quium naturae universalis, for preventing of Vacuity, there are taken away succes­sively [Page 134]from the superficies of the Mer­cury certain scales as it were of an in­divisible profundity, and these are rari­fied into a subtle invisible consistence or vapor, which supply that deserted space, and make up a kind of funiculus that suspends the Mercury to the Tube, and is coextended to the whole vacant space gradually, as the Mercury descended.

This seems to be somewhat difficult, especially considering the heterogene­ous parts of the Mercury, whereof some seem to be of that solidity, that are un­capable of such a separation.

Besides it would be difficult to con­ceive, how these superficies of this Body should in a moment, by the inclination of the Tube, be rejoyned to the Mercu­rial body and consistence; and in a moment again, upon the re-erection of the Tube to its perpendicular posture, be rarefied from so gross a consistence into so subtle and invisible a nature; both which will be the effects, one of the inclination, the other of the re-ere­ction of the Tube.

Therefore I shall rather choose ano­ther, [Page 135]and, as I think a more accounta­ble Solution.

It is plain to our daily observation, that all Bodies, especially such as are liquid or fluid, do continually send out from them certain subtle Effluvia, scarce perceptible to the Eye, but manifest in their effects. It is also evident, that all Bodies, especially fluids, and such as consist even of Heterogeneous parts, by strong agitation, by heat or motion, have many of their parts resolved into a more subtle consistence, than appeared before such agitation. Thus Water by heat or violent motion resolves it self into vapours or steams.

Mercury is of it self an heterogeneous body, consisting of some more solid, o­ther more fluid and moist parts. If any man shall take the pains violently to shake Water and Mercury together, and throughly wash it, he shall find the shi­ning parts that are the more fluid, se­vered from little black or dark granules like Sand, which will gradually subside visibly in the water into a heap, before the nimble shining particles united [Page 136]to them, and also certain Airy corpuscles rising to the top of the Water.

And as thus by the separation by wa­ter, so by a strong heat the Mercurial Bodies will be in a great measure re­solved into a fume or smoak, which ne­vertheless (as is said) will coagulate a­gain, and assume the former Mercurial consistency, at least in a great measure.

Mercury, though it be one of the col­dest Minerals, doth contain and send out from its body certain Effluvia, and noxious vapors, as they experiment that are conversant in Mines of that kind.

If any man observe the descent of the Mercury from the top of a long Tube in the Torricellian Engine, he shall find the descent not so quick and nimble, as if both ends were open, and (contrary to the usual acceleration of descending heavy Bodies) more and more slow and faint, the nearer it comes to its station; which is an evidence that there is a luct a and contention in Nature, while it extrates, separates, and abrades the parts, that must supply the derelicted [Page 137]space, and likewise in giving them a tension or dilatation answerable to it.

They that have exercised much the Torricellian Experiments, and those of the like nature with Mercury, have ap­parently found that the frequent itera­tion of these Experiments have much imbased the nature of Mercury, depu­rating it from those subtle steams and Effluvia that naturally attend it, and thereby the very Mineral it self becomes more vapid, discharged of its subtle Spi­rits or parts, and rendred less useful not only for Medicinal but Mechanical Experiments: whereby it appears that it loseth somewhat of its more subtle sub­stance by iterated Experiments, and will prove more sluggish. For this I call to witness Honoratus Fabri, in the latter end of his Philosophical Dialogues, and some of our own Nation that have asserted the same, and in my own Ex­perience I have also found it true.

It is certain, that when Mercury, or any other fluid falls in a Tube, the high­er it falls, the more force it hath, and the greater compression the lower parts [Page 138]receive from the upper; for all Bodies that descend, descend with the greater force, according to the altitude of their descent, as I shall have occasion hereaf­ter to observe.

The descent therefore of Mercury in a Tube of six foot high, is much more powerful than a descent from four foot high; and That than a descent from three foot, or twenty nine Inches high, and consequently the compression of the inferior parts by the superior; and in a greater descent than in a less. the agitation of all is the more vigorous

And yet (as I before said) it is evident in the descent of the Mercury from a Tube of four foot high, stopt above, and im­mersed beneath in restagnant Mercury, is not without a lucta or contention; and although the higher the Tube is, the descent at first is more quick, yet it gradually grows slower and slower, 'till it come to the common station of its suspension, viz. twenty nine Inches and half, or thereabouts. But yet even in the first efforts of its motion, it is not so quick or violent, as its own natural [Page 139]motion would otherwise attain for it, receives a remora and impediment by the difficulty of separating of its subtle parts.

These things are apparently true to any man's observation, and from these observations I frame these Conclusions.

1. That the substance that fills the head of the Tube, as the Mercury de­scends, are the Effiuvia, steams, or sub­tle vaporous parts of the Mercurial Body.

2. That these steams or vapors are separated from the Mercurial body by a double immediate means. First by way of Expression, or driving them out by the strong descending motion of the Mercury, the compression of the inferior parts by the superior, and the great agi­tation of its parts; the grosser Mercu­rial parts coming closer together, and driving out the more subtle and vapo­rous parts. Secondly by way of Ex­traction, or straining out those parts that are more subtle and fluid, and ca­pable of Expansion, and from hence ariseth that lucta and mora in the descent [Page 140]of the Mercury, by the straining of the Mercurial vaporous bodies, and raking them out. And

3. That those parts thus extracted are dilated and extended to as great an amplitude and tension, as the strength of the descent of the Mercury, and the amplitude of the space it leaves re­quires; which tension also contributes much to the retarding of the swiftness of the Mercurial descent.

4. And because at twenty nine In­ches and half, the weight of the Mer­cury decreaseth to such a state, as cannot work any farther separation of subtle matter to supply any more room, it stays there, and descends no farther, not having strength enough at that hight to separate any subtle matter from it self, to supply the space it should leave by such descent.

5. Although the immediate cause of the separation of the subtle matter of Mercury, and the expansion or dilata­tion thereof, be the force of the descent, and weight, and pressure of the Mercu­ry, yet this is performed in obsequium [Page 141]universalis naturae, for the avoiding of the dissolution of Continuity, or, which is all one, obfugam vacui.

6. And the same reason mutatis mu­tandis will be applicable to the suspensi­on of water in a Tube, which will be sus­pended at 31 foot, or thereabout, as Mer­cury is at twenty nine Inches. For by the same means that subtle parts are sepa­rable from Mercury, subtle parts are much more separable from Water, by a strong tension or compression of it, as appears by the raising of innumerable Airy Bubbles out of a vessel of Water, by the strong tension of the Air in the Air-pump, large instances whereof ap­pears in Mr. Boyle's Experiments, 19, 21, 22, 23, &c.

The whole process and model of the suspending of Water in a long Tube above one and thirty foot long, and how it subsides to about one and thirty foot, and no longer. vide apud Shottum in his mirabilia Vari lib. 3. cap. 2. in Ex­perimento Robervalli Magnani & Bertii.

And now if it be said, suppose the Tube were seven, eight, or ten foot [Page 142]long, or if it were three or four foot long, and the upper end were a Bolts head, that should contain three or four pound of Mercury, this would subside to twenty nine Inches: where should there be Effluvia to fill so great a space?

I answer: the more Mercury descends to twenty nine Inches, the more Efflu­via there will be to fill that place that the Mercury left, and so the Supply will necessarily be as liberal, as the space the Mercury took up before its descent to 29 Inches and half, because there is a grea­ter stock of Mercury to yeild it, and a greater continuation of motion to ex­tract it. And there seems no necessity of any great quantity of subtle matter to be driven, or driven out of the Mer­curial Mass, because it is a substance ca­pable of dilatation to a greater expan­sion than its own natural consistency, by the subsiding of the Mercury.

Mersennus tells us, that by experience he finds, that by a strong tension of a particle of Air, it is capable to an ex­pansion of neer seventy times the space of its ordinary consistency, as in Aeoli­piles, [Page 143]and the like Engins. And we see that if an Inch of Air be left in the top of the Tube, it will by the bare force of the descent of the Mercury be expanded to neer ten times its former space. And upon the same account it will fall out, that the quantity of one Inch of those Mercurial effluxes will, by the descent of the Mercury, be stretched out and ex­panded to fill the derelicted space of the Mercury, far exceeding their common and ordinary extension.

Fig. 9. The most considerable Ob­jection against this Supposition seems to be this. That if the Tube of four foot long filled with Mercury, and then im­mersed in restagnant Mercury, where­by the Mercury subsides to twenty nine Inches, and leaves a space of about 18 Inches seemingly empty, yet if the Tube be inclined, as in B, to an altitude pa­rallel to twenty nine Inches of vertical hight. The Tube B will be as at first filled with Mercury, drawn or driven out of the restagnant vessel, and no va­cant space left; and if again it be ere­cted perpendicularly as before, the Mer­cury [Page 144]will subside as before, viz. to twen­ty nine Inches; what becomes of the subtle exhalation upon the inclination of the Tube?

I answer, it is true, that by the incli­nation of the Tube the Mercury that de­scended out of the. Tube into the re­stagnant vessel of Mercury, will be drawn up into the Tube, and the Tube filled again with it, the same by the in­clination of the Tube becomes of less accidental weight. But this doth no way cross what I have supposed: I therefore answer,

1. That by the inclination of the Tube at B, the Mercury doth not press so urgently upon the subjected Mercury, as it doth in its perpendicular position; for it is sustained according to the laws of Staticks by leaning upon the incli­ned Tube, and presseth not so forcibly upon the fund or Base.

2. That therefore the pores or con­sistency of the Mercury in the inclined Tube are more lax and open, and regain more of that natural texture of its Mer­curial consistence, and receives into it [Page 145]again those connatural steams or efflu­xes, that were shot or drawn out of it by its former compression, and the attra­ction made upon it by reason of its de­scent.

3. And by its re-erection unto its former perpendicular posture, they are again thrust or drawn out by its con­traction and compression, and the for­cible attraction wrought upon it by that Catholick Law of Nature, preser­ving the continuity of the Universe.

And that which seems evidently to evince the truth hereof, is the instance given by the Excellent Author himself, in his 20, 21, 22, 23, but especially in his 24 ^th Experiment of the Air-pump; wherein the violent attraction of the Pump, and the strong tension of the Air included in the Receiver, raiseth from the bottom of an included vessel of Wa­ter Oyl, but especially Spirit of Wine, great Bubbles to the top of the vessels, (which is performed either by that for­cible extraction of the more subtle and Aerial Particles included in that liquor, or by subtilizing or rarefying some [Page 146]parts of the liquor. But as soon as that strong tension and attraction by the included Air is taken off, by the immis­sion of fresh Air into the Receiver, the Bubbles subsided, and the subtle parts included in it were again rejoined, and reunited to the same liquors from whence they were exhausted, which by a new tension wrought by a new re­peted suction of the Pump, might be again extracted.

And thus far touching the third Ge­neral, namely what it is that is inclu­ded in the space derelicted by the Mer­cury.

CHAP. X.
The enquiry touching the Cause that keeps the Mercury suspended in the Tube at 29 Inches, or there about; and first what is not the Cause of this Suspension.

THE consideration of what it is that remains in the derelicted space, in the upper end of the Tube, and the consideration what it is, that keeps up the Mercury to twenty nine Inches, or thereabouts, are of two several kinds: for although the former Consideration is necessary to be known, before we can arrive at a reasonable discovery of the latter; yet it would not be simply of it self impossible, that there should be such a corporeal substance, as I have above conjectured, in the derelicted head of the Tube, and yet the Mercury might wholly discharge it self in the restag­nant vessel, which yet we see it doth not.

Therefore having in the former [Page 148]Chapters finished the former, which was the fourth general Inquiry, name­ly, what it is that fills the derelicted space; I now come to the fifth and sixth Inquiry, namely what is not the cause of this suspension of the Mercury, and what seems to me the true cause thereof.

And among those that are assigned for causes of this suspicion, which yet are not causes thereof, I shall mention on­ly these three; namely the renitence or resistance of the Mercury in the restag­nant vessel; 2. and the counterpoise of the impendent column of the Atmo­sphere, equal in base to the base of the Cylinder of Mercury suspended in the Tube; and 3. the Elatery or Spring of the inferior part of the Air.

Of the former briefly in this Chapter, of the two latter more at large in what follows.

Stevinus in the Explication of the 10 ^th Proposition of his Hydrostaticks, assirms, that the resistence of the base of any fluid Body, is greater in propor­tion than the pondus deprimens of a like [Page 149]fluid: which Fabri in the sixth of his Philosophical Dialogues, pag. 480. and 493, goes about Geometrically to demon­strate: but I confess that it is performed with so much intricacy, and obscurity, that I do not fully apprehend it.

And if this be so, it may seem at first view, that the resistance of the restag­nant Mercury in the subjacent vessel, which is as it were the base or foot of that Mercurial Column of Mercury, that is suspended in the Tube, may con­tribute something to its sustentation in that position.

But upon due consideration I find this is but an imagination, and contri­butes nothing to this phaenomenon.

Indeed, if a liquid be impendent upon solid base, as Mercury upon Marble; or if a lighter or less compacted fluid be bot­tomed or imbased upon a much more gross and compacted fluid, as a Tube full of Air upon a Superficies of Water, or a Tube full of Water upon a Superficies of Mercury, though the Tube be open at both ends, the Base will sustain the Column of the lighter or less compacted fluid.

But if they are of the same kind and consistence, the Base contributes no­thing to the sustentation of the impen­ding Column. But if there be no other impediment, it will wholly subside. And therefore if a Tube, open at both ends, be filled with Water, and the lower end stopt with the finger, be immersed under a vessel of Water, and then unstopped; or if an open Tube stopt at the lower end with the finger, be immersed in a vessel of restagnant Mercury; in the former case the Water, and in the latter the Mercury will wholly subside to the level of the Super­ficies of the Water or Mercury in the subjacent vessel, which would not be, not withstanding the Tube were open at both ends, if a Base of the same fluid had any force or resistance against its descent.

Nay the truth is, the position of the Water or Mercury in the Tube, in any the least degree higher than the Super­ficies of the Water or Mercury in the vessel, hath an accidental Gravitation upon a lower Superficies of the same [Page 151]fluid, by reason of such position or ele­vation of the fluid in the Tube, above the Superficies of the fluid in the vessel, and by that position presseth upon it, as shall be farther illustrated hereafter. And therefore the pondus deprimens of the same fluid in such an elevated posi­tion, conquers and overmatcheth the potentia sustinens of the subjected fluid, though it were an Ocean of Water. I therefore lay aside this Supposition, as contributing nothing to this phaenome­non, and proceed to the examining of those, that with great pretension and patronage are suggested to be the Cause of this Suspension.

CHAP. XI.
Concerning the supposition of the aequipon­dium of a pillar of the Air, or Atmo­sphere, as the Cause sustaining the Mer­curial Cylinder.

THis latter age, as it produced the Torricellian Experiment, so it hath produced a new Systeme in Nature for the Solution of it, namely the Gravi­tation of the Atmosphere, and an aequi­pondium of a Column thereof to the weight of the Mercurial Cylinder con­tained in the Tube, whereby it is sustai­ned; a fuller Explication whereof here­after follows.

And it is admirable to see, how much this new opinion hath, obtained among the Virtuosi of this latter Age; so that as a new fashion is greedily entertained a­mong the Gallants of the times, and an old fashion despised and contemned; so this new hypothesis is as greedily enter­tained by the great Wits of the times, [Page 153]and hath obtained the stile of a Doctrine; and the Old Peripatetical Learning, touching Vacuum, and the Inseparabili­ty of Bodies, exterminated, under the re­proach of decantata fuga.

Nay the theory is so much idolized, that some late Authors have strangely contended for the dignity of being the first Inventers of it.

And some that have defended the Peripatetical Solution of fugavacui, as Shottus, when he wrot his mirabilia Hy­draulica and pneumatica; yet whether overwhelmed and astonished with the Magdeburgh Experiment and varieties thereof, or whether he was not willing to seem to perceive less than the Virtuosi, that had espoused the new Solution, becomes a Convert, and fairly retracts his former Opinion, and gives up the Solution of the Torricellian Experiment to the aequipondium of the like portion of the Atmosphere, in his Technica Curi­osa, l. 4. cap., 6. §. 2.

And 'tis pleasant to see what a won­derful progeny, and voluminous Sy­stems of Theories, Consectaries, and [Page 154]Conclusions have been since built upon this Supposition! wherein though the Authors have shewn much wit, subtle­ty, and learning, yet they have lost the expence of much time, and invention, and pains, if at last when all is done, it prove but an imagination.

The Supposition therefore seems to be this: I. That the Atmosphere or lower portion of the Air, some say seven, some twenty two, others fifty, others an hun­dred miles high, hath a considerable Gravitation upon its inferior parts upon the Earth, and upon all Bodies in this lower world.

2. That where a Tube, sealed at one end, is filled with Mercury, and then inverted into a restagnant vessel of Mercury, the Mercury will subside to twenty nine Inches and half, and no lower, because a column of Atmosphe­rical Air, of the same base with the ca­vity of the Tube, and incumbent upon the face of the restagnant Mercury, doth just counterpoise such a column of Mer­cury of twenty nine Inches and half [Page 155]high: so that if the Mercurial Cylinder be of that bulk, as to weigh five pound, the Atmospherical Cylinder weighs just as much, and so as one artificial scale being charged with an equal weight with the other, stands in this aequilibri­um: so in this natural Scale the Atmo­spherical Cylinder pressing upon the restagnant Mercury with an equal weight, to the 29 Inches and half of Mercury in the Tube, sustains and keeps it up in an aequilibrium.

3. But if while the Mercurial Cy­linder stands thus suspended, there be any little hole made in the sealed top of the Tube, the weight of the Air now pressing in upon the Mercurial Cylin­der, takes away that aequilibrium which it had with that external column of At­mosphere, while it was protected from the impendent column of Air by the sealed top of the Glass; and now the Mercury is driven down by the equal weight of the Air, and wholly subfides into the restagnant Mercury; for now the Aereal Cylinder without the Tube, and that within and upon the Tube, [Page 156]have the same common weight or Gra­vitation upon the Mercury. And upon these Suppositions they graft innumera­ble Conclusions, and among the rest that the Air gravitates upon all Bodies; that the exact proportion of the weight of Air is herehence necessarily deduci­ble; for if a column of Mercury, of half an Inch diameter, and twenty nine In­ches and half high, weighs two pound (for instance,) then a column of Air of the same diameter, extending from the restagnant Mercury to the top of the Atmosphere, weighs just as much. And from hence they measure the hight of the Atmosphere, or ponderous Air; namely, Air being about a thousand times lighter than the like bulk of Wa­ter, and Water being fourteen times lighter than the like bulk of Mercury, it must follow by the rule of proportion, That if two pound of Mercury give a column of half an Inch diameter, to be twenty nine Inches high; then two pound of Atmosphere must give a co­lumn of twenty nine times 14000 Inches high: (I am not curious in the [Page 157]proportion, but only shew the method of their inferences:) and abundance of such fine Consequences are built upon this Platform, which were too large to enumerate.

Now as touching this Solution of the Suspension of the Mercury in the Tube, by the aequipondium of a Cylinder of Air, of the same diameter with the Cylinder of Mercury, I say it seems to me an Imagination, and to be utterly un­true.

I will not repete what I have former­ly said against the Gravitation of the Air, in the fourth Chapter, which yet I take to be sufficient to evince the un­truth of this Supposition: but I will subjoin two or three homely Experi­ments, which with the application of them will, as I think, detect the untruth and inefficacy of this Solution.

1. I will begin with one offered by the Asserters themselves of this Solu­tion, of a late learned Author, in the 11. Proposition of his Hydrostaticks, and the Scholium thereupon, which I shall agree to be a true Experiment, but the appli­cation [Page 158]thereof too much distorted, to gratifie the hypothesis, but in truth and reality utterly confounding it.

Take a vessel of reftagnant Mercury, of seven Inches deep; then take a Glass Tube of half an Inch diameter in the cavity, and of half an Inch thick in each side, sealed at the one end, and of 3 foot long; whereby the entire Tube will be an Inch and a half in its whole diameter: Fill it with Mercury, and stop it with the finger at the open end, and invert and immerse it to the bottom of the restagnant Mercury. It will then come to pass, that about twenty nine Inches and half, the ordinary altitude of the column of Mercury, will be above the Superficies of the restagnant Mer­cury, and the whole Tube will thereby remain full to the top: but the Glass being lighter than the Mercury, will be impelled up by the restagnant Mercury neer to the Superficies thereof, where­by there will remain about six Inches of the upper end of the Tube empty of the Mercury, but still there will be about twenty nine Inches and half of the Tube [Page 159]still full of Mercury, namely, the usual station of its Suspension.

I will suppose the twenty nine Inches and half of Mercury, suspended in the Tube, to weigh one pound, and that the Glass Tube of it self weighs likewise one pound.

I will now suppose, that the upper end of the Tube were fixed by a string to the Beam of a pair of Scales, as in his 319th figure in that book. I say that two pound in the adverse Scale will counterpoise this Tube with the inclu­ded Mercury, and if any little advantage of weight, suppose an Ounce, were ad­ded to the adverse Scale, that Scale charged with two pound and an Ounce, will preponderate it.

And I say no more than what the Author says was determined touching it by the Royal Society, whereunto he subscribes, pag. 727. in these words. ‘ Pon­dus in adversa lance contraponderans aequi­pollebat suspensi hydrargyri cujusounque al­titudinis, at que simul (quantum conjectando aestimabant) suspensi tubi ei parti quae stag­nantis in subjecto vase hydrargyri superfi­ciei [Page 160]supereminebat.’ Now it is certain that if the one pound of Mercury con­tributes to this weight, it is not sustain­ed by the adjacent external column of Air, pressing the Superficies of the re­stagnant Mercury; for if so, it is sustain­ed by the aequipondium of that Aereal co­lumn, and cannot affect the Scale with its weight; for it is sustained by ano­ther counterpoise, and not by the two pound weight of the Scale.

And again it is as certain, that if the Mercury do contribute to the counter­poise of the Scale, it must by some means be as it were fastned to the Scale, (we will suppose it to be Linus his funiculus,) for otherwise the Glass would only weigh as a separate thing from the Mercury, which would of it self contri­bute ( ex suppositione) but one pound to the weight, which would be necessari­ly preponderated by the adverse Scale charged with two pound weight.

And therefore it is most clear, if the included column of Mercury contri­butes one pound weight to the ballance, it is not sustained by the imaginary [Page 161]column of Air equal in diameter to the Mercurial Cylinder, but by an intrin­sick connection or ligament to the Tube, whereby it weighs as one con­crete Body with the Glass, which I call the Funiculus ex subtilibus Mercurialibus effluviis contextus.

The Author, to avoid this difficulty, therefore tells us, that this thing primo aspectu incautis nonnullis ad Staticam mi­nus attentis facile imponeret; and to avoid the imposture, tells us, that all this while it is not the Mercury that contri­butes to the weight, for that hath ano­ther kind of Sustentation by the aequi­pondium of the forreign Air; but it is another column of Air, that impends upon the upper end of the Glass Tube as its Base, and therefore commensurate to the suspended Mercury in weight. And this is the effect of the Solution, namely, that only the Glass, and the co­lumn of Air impendent upon it, makes the counterpoise, and the Mercury con­tributes nothing to it.

And indeed if the column of Air, charging the Tube, were of an equal [Page 162]diameter with the Mercury, or the ca­vity of the Tube, the Evasion were handsome and suitable to their hypothesis, though untrue: but the instance in question, as it is proposed, quite shat­ters this Solution, and renders it not on­ly untrue, but unsuitable to their very principles.

For in this instance, the diameter of the column of Mercury is but half an Inch, but the diameter of the whole Tube is an Inch and half, which gives an area to the base of the Cylinder of Air impending on it, more than four times bigger than the Base of the Mercurial Cylinder. And therefore if a Cylin­der of the Atmosphere of half an Inch diameter, be commensurate to the weight of the Mercurial Cylinder, and consequently weighs a full pound at that scantlet; the Aereal Cylinder, commensurate to the upper area of the Glass tube, which is an Inch and half diameter, must necessarily weigh above four pounds, and therefore would not be equiponderated by the two pound weight in the opposite Scale.

This instance therefore which is de­livered with the memorial of the day, and place of its Exhibition, seems to make more to the disadvantage, than the advantage of this new Philosophy.

But to this Objection there is a Solu­tion offered, namely, that let the Glass be of what thickness it will, That alters not the case; for the Mercury is pressed up by the counterpoise of a Cylinder of Air, answerable to the cavity of the Tube, not to the crassitude of its sides: for Glass being a Body specifically lighter than the Mercury, the Glass it self is sustained by the restagnant Mer­cury, which is its Base, and supports it.

But still this Answer, though it be true, avoids not the Objection. For 1. let us suppose, in stead of a Tube of Glass, a Tube of Gold, which being spe­cifically heavier than so much Mercury, would sink to the bottom, and not be sustained by the Mercury, but must be lifted up, and sustained purely by the weight in the opposite Scale: 2. or suppose the Tube of Glass were charged in its closed end with a greater quantity [Page 164]of Lead, that, though specifically lighter than Mercury, would by its excess of extrinsical weight, depress the Tube to the bottom of the restagnant Mercury: or 3. though the Tryal were made by a Glass Tube filled with Water, and in­verted into a vessel of Water; for there the Glass Tube, with the inclosed Cy­linder of Water, would subside to the bottom, being altogether in its con­crete heavier than the Water, and could not be supported by the restagnant Water, but by the weight in the adverse Scale: in these Instances the difficulty will not be salved.

Therefore I took a Glass Tube, the cavity whereof was half an Inch diame­ter, the thickness of the Glass incircling the cavity [...]of an Inch; and conse­quently from outside to outside the dia­meter of the Tube was ⅝ of an Inch; the length of the Tube eighteen Inches, the weight thereof in the Air two oun­ces ¾ of an Ounce, and being heavier than the like bulk of Water, it would freely subside perpendicularly to the bot­tom of a vessel of restagnant Water [Page 165]deeper than 18 Inches, notwithstan­ding the sustentation it had by the in­cluded Air, being empty, and so the Water contributed nothing to the sup­port of the Tube when it came to be weighed, but only the thickness of its medium, which yet was not able to sup­port it from sinking.

The Water which the Tube would contain, weighed one Ounce and three quarters, wanting about a Grain or two at most.

The Tube was tied at the closed end with a string to the Scale of a Ballance and filled with Water, and stopping it with the finger, inverted into a vessel of Water 18 Inches deep, or more: and then the Tube with the included Wa­ter thus immersed in Water, carefully weighed, the Water still remaining sus­pended in the Tube, (as it will do as long as it stands so immersed,) and the Events were these: When the Tube was full six Inches above the Superficies of the Water in the Vessel, it weighed just two Ounces and three quarters of an Ounce, which [Page 166]weight in the opposite Scale kept it in an equilibrium; for now the rest of the Water in the Tube, below the Superfi­cies of the Water in the vessel, weighed nothing at all, because it obtained so far the same common Superficies, and was therefore sustained by the common weight which it had with the Water in the vessel, and only six Inches of Water contributed to the counterpoise, toge­ther with the weight of the Glass Tube it self, though refracted by the thick­ness of the medium: so that now these six Inches of suspended Water, and the Tube it self, weighed no more at this position in the Water, than what the Tube alone weighed in the Air.

But when the Tube, with the inclu­ded column of Water was raised very neer eighteen Inches above the Super­ficies of the vessel of Water, so that there was as little as could well be to keep the orifice of the Tube under Water, viz. about a quarter of an Inch, it then required an addition of very neer one Ounce ¾ in the opposite Scale, to hold the Tube in an aequilibrium which equal­led [Page 167]the true weight of the Tube it self and Water included, when in the free Air, viz. two Ounces and three quar­ters, and one Ounce and three quarters, in all four Ounces and half; because now the Water in the Tube had now in effect its due weight, which it had when divided from the Water in the vessel, and so had its due Gravitation upon the Scale.

Upon this Tryal of it with Water these things are observable.

1. That according to the proporti­on of the Elevation assigned to Water, it would have been sustained in a Tube of one and thirty foot high, and conse­quently in this of eighteen Inches the Water had not attained a twentieth part of that height, at which it might in a Tube be kept suspended.

2. That according to these mens Suppositions, the Suspension in the Tube, either of Water or Mercury, is supposed to be by the pressure of a co­lumn of the Atmosphere upon the Wa­ter or Mercury in the vessel, and there­by the column of Water or Mercury is [Page 168]by that counterpoise driven up in the Tube. This Tube being but of eighteen Inches long, the forreign Atmospheri­cal pillar still will urge the Water or Mercury to rise to an aequipondium with it, namely the Mercury to twenty nine Inches, the Water to thirty one foot, or thereabouts.

3. And consequently, according to their Supposition, the Cylinder of Water, in the instance in question, within the Tube, presseth up the Tube, and would lift it up to one and thirty foot high, had the Tube been long e­nough.

4. But as the Atmospherical Cylin­der without the Tube presseth up the Water, so the Atmospherical Cylinder incumbent upon the head of the Tube, presseth it down; and so according to those men it is not the Waten in the Tube, that gives any counterpoise to the opposite Scale, but the Atmosphe­rical Cylinder, answerable to the cavi­ty of the Tube, that presseth upon the head of the Tube.

5. And that weight of the Atmo­spherical [Page 169]Cylinder upon the head of the Tube, is counterpoised by the forreign Cylinder, abating only so much, as the proportion of the Water thrust or kept up in the Tube, amounteth to; which being in the instance in hand about a twentieth part of what the forreign At­mospherical pillar weighs, the Atmo­spherical pillar incumbent upon the head of the Tube weighs just so much as the Water included in the Tube a­mounts unto. But upon the whole mat­ter, this fine Theory appears to be but a handsom Imagination. For it is plain, in the instance in hand, the At­mospherical Cylinder, incumbent upon the head of the Tube, is larger than the cavity of the Tube, and consequently more weighty by far (if it have any weight at all) than that forreign Cylin­der of Atmosphere, which is supposed to sustain the included column of Wa­ter, and the Tube it self is not sustained nor sustainable by the Water in the ves­sel, but is wholly raised by the weight in the opposite Scale: and therefore the Supposition, that the weight that pres­seth [Page 170]upon the Scale, is the weight of the Cylinder of Air upon the Tube it self, is vain; for then it should sustain the weight, not only of the Tube, but another weight far greater than the forreign column of Air could counter­poise.

And that which seems to me to con­vince this mistake in the whole propo­sed Theory, is this plain and obvious Experiment.

Fig. 10. I therefore took a Glass-tube of about half an Inch diameter, 18 Inches long, closed at one end; and weighing it exactly in the open Air, it weighed two Ounces and three quarters of an Ounce, and heating it very hot, where­by the included Air was highly rarified, I suspended the closed end upon one Scale of a Ballance, and let the open end sink a little into a vessel of Water, and counterpoised it in the other Scale with two Ounces three quarters; and be­cause the end of the Tube did but little more than touch the Water, it held the same weight as before upon the Scale, viz. two Ounces three quarters.

As soon as the Tube was thus conti­guous to the Water, it attracted and rai­sed the Water so, that in half a quarter of an hour the Tube was filled twelve Inches with Water, the Air contracting in self to six Inches in the top of the Tube, whereby it appears it was rarified two thirds beyond its natural and or­dinary rise and standard, which now againe it acquired by contracting it self.

The Water which it attracted being carefully marked at its highest Elevati­on, and then strictly measured, weighed one Ounce and a quarter.

Now the things observable in this instance are these. 1. That the single Tube, with the included rarified Air, did really weigh even in the external Air but two Ounces three quarters, and by that weight in the opposite Scale it was perfectly kept in aequilibrio. 2. That when it touched the Superficies of the Water, and thereby attracted the Wa­ter into it, it presently grew more weighty, which it gradually increased, and accordingly more and more subsi­ded, Tube and all, into the subjected [Page 172]vessel of Water, as it received into it more Water, and consequently grew more weighty, 'till its full comple­ment of 12 Inches of Water drawn up into it 3. That when it was filled with twelve Inches of Water, then it weigh­ed the full weight of the Tube, and the Water viz. two Ounces three quar­ters for the weight of the Tube, and one Ounce and a quarter for the weight of the Water intato four Ounces, and therefore four Ounces in the opposite Scale would keep it just in aquibrio. On­ly care must be taken, either by depres­sing the Water, or raising the Ballance, that the Tube must only touch the top of the Water, for otherwise the Water will run out, and prevent the tryal. Now to discover what it is that thus de­presseth the Tube gradually, as the Water riseth up into the Tube, whe­ther the weight of the Tube, or the weight of the Water included in it, I will consider, 1. What the external column of Air, which those Masters suppose to press up the Water in the Tube, contri­butes [Page 173]to it. and surely according to this Supposition of theirs, this is so far from causing any access of Gravitation to the Tube or Water included in it, that it rather presseth up the Tube, by pressing and impelling the Water into it, and indeed it is that which they themselves say, and build their Theories upon it, viz. that for this reason the Water in the Tube weighs nothing.

2. What the column of Air impen­dent upon the top of the Tube, com­mensurate in diameter to the cavity of the Tube, doth contribute, which accor­ding to their Solution must be it that weighs down the Tube by pressing up­on it. But certainly this doth nothing in this case; for if the Tube it self, filled with rarified Air, weighs in the open Air but two Ounces three quarters, it can never come to weigh four Ounces when in the Water, (where by reason of the thickness of the medium, it must lose, and not gain weight,) and it had the same column of Air impendent upon its top, as well before its immersion in­to the Water, as after. And before its [Page 174]immersion (whether it were full of com­mon Air, or of Air thus highly rarified by heat) it still weighed neither more nor less than two Ounces three quar­ters.

3. Therefore it remains, that it is the weight of the Water, that thus creeps up in the Tube, and in its ascent to twelve Inches weighed just one Ounce and a quarter that gravitates in the Tube, and renders the weight of the whole to be four Ounces, which in the opposite Scale holds both Tube and Water in aeguilibrio.

And as the Tube is suspended to the Ballance by the string or thrid, so the included rarified Air is suspended to the top of the cavity of the Tube, by the powerful Laws of Nature, and lays hold upon the Superficies of the Water; and as it contracts it self more and more, draws up the column of Water higher and higher; as a Lute-string fastned to a fixed Body above, and to a small Weight below, after a high tension raiseth the Weight by contracting it self, and this to maintain the continuity of the parts of Nature.

And this is a plain sensible and unfor­ced Solution; and it seems to me, that those that tell us, that it is only the Tube, and the incumbent Cylinder of Air only, that gives the weight, were imposed upon, though not by ignorance of Statical Laws, yet by fondness and partiality to a new invented hypothesis.

2. The second Instance that I shall give, shall be this: Take a Glass Tube, closed at one end, of an Inch diameter in the cavity; fill it with Mercury, stop it with a small Engine, and invert it in­to a vessel of restagnant Mercury of an Inch and half diameter; then opening it by a contrivance which is not diffi­cult, after it is inverted in the Mercury, the Mercury will be sustained at twenty nine Inches and half, as well as if the vessel of restagnant Mercury were of six Inches diameter.

And yet it is apparent, that the rim or round Superficies of the vessel of re­stagnant Mercury, is not above one fourth part in area of the Mercurial Cy­linder, and cannot be pressed with a co­lumn of Air commensurate to the cavi­ty [Page 176]of the Tube; for the incircling co­lumn of Mercury is not a fourth part of the area of the Tube, neither can it be pressed with a column of Air of a grea­ter diameter or dimension than that lit­tle rim of Mercury that incompasseth the Tube. So that it is not the aequipon­dium of the Atmospherical Column that sustains the Mercury in the Tube, for if it should; a column of Air of the fourth part of an Inch diameter, should be as weighty as a column of Air of an Inch diameter, because it must in this Instance make an aequipondium to a weight of Mercury, commensurate to a column of Air of an Inch diameter.

Therefore it is not the aequipondium of the Air that sustains the Mercury in the Tube, but something else, and what that is, we shall here after examine.

3. My third Instance is that com­mon one: If the Torricellian Engine be put in practice, in a great Glass Recei­ver, wholly excluding any communi­cation with the forreign Air, the Mer­cury will be suspended at twenty nine Inches and half, as well as in the free [Page 177]Air. And yet here can be no Atomo­spherical column, reaching from the top of the Atmosphere to the restagnant Mercury, with its Gravitation, to su­stain the Mercurial column, the same being intercepted and broken by the in­terposition of the Glass.

And this plain obvious evident In­stance had wholly destroyed the hypothe­sis, and utterly disordered and scattered all the porismata and Consequences built upon it, had not another supple­mental invention stept in to relieve it, namely the prodigious Elatery of the free Air, which upon a due examinati­on will prove as great a mistake, and as impotent to relieve this deficient hypo­thesis as the former; and if it prove so, I doubt our new Philosophers must be fain to return to the decantata fuga vacui for a better Solution.

CHAP. XII.
Touching the Elatery or Spring of the Air.

I Come now to consider that subsidi­ary help, substituted by the New Philosophy, for the Solution of the Phaenomena of the Torricellian and o­ther Experiments of this nature: and herein I shall consider these things.

1. What Elatery or Spring is of all hands agreed to be truly found in the Air.

2. What Elatery or Spring is substitu­ted by the late Philosophy, and how ap­plied by them to the Solution of phaeno­mena of this kind.

3. The Arguments, Reasons, and Evi­dences that evince the mistake of this new Elaterical Supposition.

First, as to the former of these, this is agreed of all hands, that the Air being a subtle Fluid, is capable of an acciden­tal Elasticity of very great efficacy and force: namely, when by accidental im­pression [Page 179]upon it, it loseth that common and natural state or consistence, that otherwise belongs to it.

As I. by a great compression of its parts together, such as we see in Wind­guns, whereby it is compressed into a space sometimes seven times less than that which is natural to it, and then by a natural and strange motion of restitu­tion it hath an Elasticity, whereby to regain its natural state and position. 2. By constipation of its parts by Cold, whereby it is bound up sometimes to a narrower room, and then by the ap­proach of convenient heat, that consti­pation is relaxed, and the Air regains its natural liberty, motion, and consi­stency: and 3. by Rarifaction by heat, whereby it is expanded beyond its na­tural size, and as it grows cold, it obtains a kind of Elasticity in ward, and an in­ward endeavouring to contract it self to its natural size and dimension. 4. In a strong tension by an accidental or col­lateral force, whereupon it con­tracts it self as much as it can to its na­tural state, and resists that tension [Page 180]which discomposeth and extends it; from whence follows that which is usually called Suction, or Attraction, of which I shall have occasion hereafter to write more at large.

Again 2. it must be agreed, that al­though the Air in its natural consi­stence is by a great force compressible into a close order, yet it doth resist such a compression, and doth not easily yeild to it; and therefore take a Tube of any considerable length, closed at one end, and the open end inverted upon the Water, and pressed down, yet the Air included will retain very much of its natural state, and receives but a small contraction by the counterpressure of the Water, possibly an Inch in two or three, or somewhat more, according to the depth of its immersion.

But these Elateries are not such as concern the present question.

Therefore I come to the Supposition of the new Philosophy, in relation to this business of Elasticity of the Air, which the attribute to the common and free Air in which we breath and [Page 181]live; and if I mistake them not, their Supposition is this: I. That the Air is a kind of Spungy Body, not much unlike (as to this pur­pose) to a Spunge or Fleece of Wool, capable of compression, and under that compression endeavouring to loosen and discharge it self by that which we call Springiness or Elasticity.

And herein we do not considerably differ, only they say that this Elasticity is of a vast, and almost unlimited nature, that scarce hath any bounds to it; we say that it hath more contracted and de­termined limits of its Elasticity, and those are such as every portion of free Air obtains in a common and usual state of the temperament of the Weather.

2. Again they say, that the Body of the Air, or at least of the Atmosphere, consists of a great many little crooked filaments like Springes, which when extended to a greater straightness than is suitable to them, as in its high tension or rarifaction, indeavour regaining of their natural curvitude; and when by any weight or force they are drawn close to­gether, [Page 182]they, spring out to their just ex­tension, and that gives a common Springiness to the Air in such a consi­stence or circumstance.

3. That the superior parts of the Air gradually gravitate and compress the inferior parts, and therefore the higher the Atmosphere or Air is, the less it is compressed, but the lower it is, the more it is compressed, the lower­most parts receiving and sustaining the pressure of all these parts that are above.

4. That the actual Elatery, or Spring of the Atmosphere, or Air, is the issue or effect of this Gravitation; and the more the Gravitation is, the greater the Spring of those parts are, when they can but get liberty to expand themselves; for the greater weight doth the more bind and incurvate these crooked filaments, which makes them fly out extremely, when they can get themselves unfettered from the oppres­sing weight, and even while they are under that pressure they have their cona­ [...]us for their liberty.

5. That because the lower parts of [Page 183]the Air next the Earth are most pressed upon by the superior parts, therefore the lower parts of the Air have the grea­test Elasticity and Springiness, which it exerciseth according as it gets liberty.

6. That therefore this inferior Air hath a natural vast propension to Ex­tension, and amplifying of it self, inso­much that if we should suppose any part of the Universe were free from any Bo­dy, or had a more subtle Body than that of the common Air, if a portion of the lower Air next the Earth were placed there, it would upon the account of its own natural Elasticity, expand it self as largely, and it may be much larger than those Artificial Expansions wrought by fire in AEolipiles, and other Engines, wherein nevertheless the Air may be so ordered, as to possess seventy times more room than before it had.

7. That therefore when we see a little portion of Air included in a Tube, in the Torricellian Experiment, exten­ded upon the descent of the Mercury four, five, or six Inches, or into a larger room than it possessed upon its first in­clusion [Page 184]this is no forced tension of the Air, but a free natural expansion of it self, having gained room and opportu­nity, by the descent of the Mercury, for its recception; and therefore this natu­ral expansion of that included particle of Air, is one great help towards the de­scent of the Mercury, 'till it comes to its station.

8. That in as much as the Elastici­ty of the Air, when contiguous to the Earth, or other solid Body, is impeded in its Elasticity downward by the resi­stance of the Earth, it is as it were re­verberated upward, and laterally, where it may be exercised: which is a great means of that support that the recoiling Aereal particles give to weighty Bodies, which is seen in the sustentation of the lower of the adhering Marbles.

9. That every part of the lower Air is under the same compression with the same region wherein it is, and therefore if a portion of the free or open Air be inclosed within a Glass-Receiver, closed on every side, yet it hath the same Ela­sticity that the portion of Air had, out of which it was taken.

10. And because that Airin the Glass is on every side penned up, and its Ela­sticity being as it were reverberated from every side of the Glass, doth the more intensely and forcibly recoil in­ward: and therefore it comes to pass, that though the great Glass Receiver, compassing in the Torricellian Engine on every side, be destitute of the weight of the column of Atmosphere, to sus­pend the Mercury by its aequipondium; yet the included Air doth the very same thing by its Elatery or Spring upon the restagnant Mercury.

And thus we see how, for the accom­modating of the Torricellian phaeno­nomena, and some others of like nature, where the pondus Atmosphoericum cannot be had nor acquired, what a laborious invention and process is framed for the supply of that deficiency.

Therefore I come to considerand ex­amine, whether this laborious process have any thing of truth and reality in it, or whether, as that of the pondus cylin­dri Atmospharici, it be only a fine in­vention to help and support a lame and [Page 186]languishing hypothesis or Solutions.

Although whatsoever doth oppose the Gravitation of the commen Air, doth as necessarily conclude against this Elasticity of the free and common Air; and although much of what I have written in the third and tenth Chap­ters, against the Gravithtion of the Air, is equally applicable against this imagi­nary Elasticity thereof, since the Ela­sticity is by the hypothesis supposed to be the effect of its Gravitation; yet I shall repete nothing, or very little, of what I have there said, but apply my self singly to the discussion of this Elatery or Sprin­giness of the common or free Air, both by Reason and by Experiments.

1. The Spring of the Air is bottom­ed upon the supposition of the actual pressure of the superior parts of the Air or Atmosphere upon the inferior, and the lower parts being under the grea­ter pressure, hath consequently the grea­ter Elatery. But upon what hath been before said, in the third Chapter, there is no such Gravitation or pressure of the Air or Atmosphere, and consequently [Page 187]no such Elatery in the free and open Air.

2. If there should be admitted any such Elasticity in a portion of the Air below in this inferior region, included within a Glass vessel or Receiver, (the instance for whose sake this invention was principally devised,) so as to sustain the suspended column of Mercury, then of necessity there must be the same Ela­sticity of the same or the like portion of the common Air, (for it is all supposed under the same common pressure of the superior parts:) the consequence where of must needs be, that either the attri­bution of that Suspension to the Gravi­tation of a Column of the Air, and all the delicate Consectaries thereupon, are more Fancies and Mistakes, because the whole phaenomenon is performable and performed by the Elasticity of the Air, as well without as within this close Glass vessel; or else the joint power of the pondus, as well as the Elasticity of the forreign Air, must raise the Mercu­ry in the Tube to fifty nine Inches, since the Elarery of the Air alone, without [Page 188]the aid of the Gravity of the Atmosphe­rical Cylinder in the inclosed vessel, is able to keep it suspended to twenty nine Inches and half. But we see the con­trary in the Experiment tried, as well within as without the inclosed Glass; therefore either the weight of the At­mospherical Cylinder, or its Elatery, must be laid aside in this Solution, or, which is the truer Conclusion, neither the one nor the other are to be admitted, but both are to be rejected as crossing one another, and also the truth of the Solution.

3. Nay, but yet farther, if this Ela­tery be admitted, the whole Scheme of the Gravitation of the Air, or any part thereof, must be rejected as fictitious, and impossible; and on the other side, if the supposed Gravitation of the Air or At­mospherical Cylinder be admitted, the Elatery must be rejected, and the whole Air will be in aequilibrio, in as much as upon this supposition of this New Phi­losophy, the Elatery presseth as much upward, as the Gravitation doth down­ward, and è converso the Gravitation as [Page 189]much downward, as the Elatery doth upward: so that after all this laborious apparatus of Gravitation, and Cylinders, and Atmosphere, and Elatery, the Air is at quiet, at rest, and in aequilibrio, which is easily granted without all this difficult hypothesis.

For according to these mens supposi­tion (if we should admit it) the Atmo­sphere were seven Miles high, we must needs suppose that the greatest Elatery is next the Superficies of the Earth, be­cause there it is more charged with the weight of the superior parts of the Air; and because the rerrestrial Globe checks the Elatery of it downward; the Elatery must discharge it self by its motion up­ward, and so encounter the pressure of the Air, by how much more its Springs and crooked Particles are charged. And a Mile higher in the Atmosphere where is less pressure, there is consequently less Elatery or resistance of that pressure, and yet sufficient to keep that rundle of Atmosphere in an aequilibrium.

And it is plain, that this Connter­motion of the supposed Spring, or Ela­tery, [Page 190]and Gravitation of the Air, must by their mutual conflict, one cheok and refract the other.

But then it is hoped, that the interpo­sition of another gross Body between the ponderous Air tending downward, and the reverberated, recoiling, Elasti­cal Air tending upward, may part the fray; and thereupon in the instance of the two cohering Marbles, the upper column of impending Air may press down the upper Marble, and the lower column of recoiling Air may press up the lower Marble.

But this will do nothing to help the business in hand, touching the Mercu­rial column in the Torricellian Experi­ment (for as for the cohesion of the two Marbles, and the reason of it, I shall in its due place examine.)

For it is plain there, that if there be any Elasticity in the Air next the Earth, there is proportion for proportion as much Elasticity in the Air next the re­stagnant Mercury, upon which it is in­cumbent, and which we may if we please, place even to the Superficies of [Page 191]the Earth; for the column of Air ( ex suppositione) proportionable in base to the Mercury, is as really gravitating upon the Mercury, as upon the Earth, and consequently there is the very same Ela­tery or sursum pressure of inferior parts of that Atmospherical pillar incumbent upon the Mercury, that would break the Gravitation of that upper Atmo­spherical Cylinder, and render it inef­fectual.

Besides all this, as it requires a strong Phantasy to suppose this wonderful Ela­sticity of the Air, so it requires a much more potent phantasy to keep the Ela­sticity of it within the precise lateral di­mensions of the Atmospherical pillar in a straight line: for the Elastical par­ticles of the Aereal parts, adjacent to that Atmospherical Cylinder, will in­croach and break it upon this Cylinder, and disorder and refract its pressure, be­sides what the concussion of Winds would effect.

4. But suppose in the free Air the pondus deprimens of the Atmospherical Cylinder were too hard for its Elatery, [Page 190]so although in an inclosed Glass the Ela­tery doth the whole business in suspen­ding the Mercury in the Tube, yet in the open Air the pondus deprimens con­quers its Elasticity, and the whole phae­nomenon shall be there performed by the pondus deprimens of the aereal Cylinder: I say such a Supposition as this would render the lower parts of the Air unmo­veable, and bind it up so, that it could never stir without an admirable relaxa­tion of it by the violence of heat, which is contrary to all the experience of the World. For we see by the smallest winds the motion of Smoak, and a thou­sand Instances more, the lower parts of the Air are in a perpetual flux and motion, which it could never do, if un­der so rigorous a constipation and com­pression by its superior parts. And though this immediately contradicts the great pressure of the inferior Air by the superior, yet by necessary conse­quence it contradicts the supposed Ela­tery thereof.

5. But as to the very instance before given, of the suspension of the Mercury [Page 193]in a Tube placed in a closed Glass Re­ceiver, protected from the impendent aereal ponderous Cylinder; I say, that the suspension of the Mercury is not caused either by the Weight or the Ela­tery of the Air. Not by its weight, be­cause the Atmospherical column is in­tercepted, and kept off by the interposi­tion of the Glass; it remains therefore that it must be done by the Elatery or Spring of the Air included in the vessel: but that cannot possibly do it, for these Reasons. 1. Because that Elatery that must sustain the column of Mercury, cannot be an Elatery pressing upward or laterally, but it must be such an Ela­tery as must press downward, to bear against the excursion of the suspended column of Mercury, and thereby keep it in aequilibrio: and certainly if there be any Elatery of the Air, it must bear ra­ther upward against what presseth it down, and causeth it, than downward. 2. But if it be said that by the Receiver, or Glass inclosing the Air every way, the Elatery is as well turned downward as upward, and so counterpoiseth the co­lumn [Page 194]of Mercury, and so it is not like the recoil of the Spring of the Air from the Earth, which must be principally upward, because checked and reverbe­rated at its base; but here the reper­cussion is from all parts of the Glass, as well from above as beneath. I say this very objection renders it utterly impos­sible, that the Elatery of the Air in the Glass can cause this Suspension, or in any measure contribute to it. For let us suppose the Glass Receiver to be spheri­cal, the repercussion of the Elatery of the Air must be equal from all parts: the consequence whereof must necessa­rily be, than this Elatery presseth as well upwards as downward, and from every part of the Spherical cavity of the Glass, the consequence whereof must needs be, that the whole Elatery is in suspence, and one Elastical line breaks, refracts, and retunds, another; so that the tendency of this Elasticity is neither upwards nor downwards, not from any point of the Compass, but all things are at rest, as where Winds blow with an equal strength every way, the [Page 195]Air is undisturbed, and so no pressure at all made upon the Mercury, but it is but a meer evasion to shore up an hypo­thesis.

CHAP. XIII.
Certain Experiments, evincing that the common Air in its ordinary consistence, hath no, or no considerable. Elasticity or Spring, without an accidental or preter­natural Compression.

IN the former Chapter I have given the reasons against the wonderful Elasticity of the Air, or Atmosphere, and the insufficiency of that Suppositi­on to give a Solution to the phaenomena in the Torricellian Experiment. And I now come to some experimental Instan­ces, farther illustrating and proving what I have said in the former Chap­ter, namely that either there is no Ela­sticity at all in the common Air, nor in any part thereof inclosed in the vessel, de quo supra, or if any at all, yet very lit­tle, [Page 196]and such as is no ways able to keep such a column of Mercury suspen­ded, which may possibly weigh ac­cording to the amplitude of the Tube two or three pounds, which yet we see suspended in the Torricellian Ex­periment.

For it is a certain and demonstrable truth, that if any potentia, be it what it will, sustains a weight or pondus depri­mens, the potentia sustentans must be of an equal strength to that weight, o­therwise it must give way, and yeild to it.

Therefore if the potentia of the Ela­sticity of the common Air (not compres­sed or constipated accidentally) be not equal in this instance to two pound of Mercury, it can never sustain or keep it suspended: and this is that which I shall endeavour to make good.

Fig. 12. Take a Bottle-Glass A, fill it with Water to B, which may contain about six Ounces of Water, the rest of the Bottle full of Air; then take the Bolts-head C, heat it very hot, that the Air may be in a great measure driven [Page 197]out of it, and the rest highly rarified and expanded: Invert it into the Glass Bottle, so that the free Air may come in, (though but at a Pin-hole,) as the Air in the Bolts-head grows cool, and con­sequently contracted neer to its natural size and state: the Air thus rarified, the Water in the Bottle will be drawn up into the Bolts-head to supply the va­cancy, which otherwise would happen by the restitution of the Air. But if the fissure between the Bottle and Shank of the Bolts-head had been hastily so clo­sed, that no Air could enter into it, some Water would arise as suppose to D, but the whole Water would never be driven up out of the Bottle by any Elatery of the Air included in it; but only the su­perior Air in C, being so highly rarified by the heat, that one third part of the Air in C, as it stood unrarified, takes up the whole Bolts-head by rarifaction; and as the Air in the Bolts-head grows to its natural temper, and consequently endeavours to retract it self to its natu­ral dimension, so having the fluid Wa­ter to work upon, it draws it up, and by [Page 198]the advantage of that attraction gives a tension or expansion to the Air in the upper part of the Bottle, as much as is capable to be obtained by the strength of the attraction and suction of the rari­fied Air in the Bolts-head, which draw­ing up the Water, and leaving less Wa­ter there than before, must needs expand the inclosed Air in the top of the Bottle, to supply that recess.

Now if the Air in the head of the Bottle, being taken out of the common Air, and of the same consistence with it, had that strong Elatery that these men suppose, so that it reacheth as it were after a dimension five, nay forty times larger than that it hath, it would thrust up the whole Water in the Bot­tle as high as E, as it would have done if the fissure between the Bolts-head and the Bottle had not been strictly closed.

And this it should have done the ra­ther, because the superior Air is so much rarified, that it takes up three times the room of common unexpanded Air, and so is capable of a more effectual impres­sion from the Air in the Bottle, and [Page 199]would not rest at D, but drive up the Water as high as E.

And if any shall say, that the weight of the interposed Water is too great for its Elatery, to thrust it up as high as E; certainly he that shall suppose that the Elatery of the Air, included in a close Receiver, is able to thrust and keep a column of Mercury to twenty nine Inches high, which column weighs pos­sibly a pound or more, cannot doubt but the Elatery of the Air in the top of the Bottle, if it were of that force that these men suppose, would thrust up five or six Ounces of Water, about five or six Inches high, into the Bolts head.

But the plain truth is, that in this in­stance, nor any of the like nature, it is neither the weight nor the Elatery of the Air included in the Bottle, that for­ceth up any drop of Water above its Superficies, but the powerful attraction of the expanded Air in the Bolts-head, endeavouring its own contraction when growing cold, and so attracting the Water to supply that casma, that would otherwise follow upon its attraction.

And therefore when by the descent of the Mercury a little portion of Air in the top of the Tube in the Torricellian Engin, gains four or five times a greater extent than it had before; this is done by the tension of that little aereal Cylin­der, by the force of the descent of the Mercury, as shall be more at large shewn hereafter, and not as is groundlesly sup­posed by the natural Elasticity or expan­sion of that portion of Air. For if that should be the cause, it were necessary that the finger stopping the top of the inverted Tube open at both ends, should be thrust up, and not drawn in, and an empty Bladder should be more compres­sed than distended by such Elasticity of the included Air, the contrary whereof is evident both to Sense and Experience.

CHAP. XIV.
The consideration of some Arguments for the weight and Elatery of the Air.

I Shall not spend much time upon These arguments, but only note some general Observations upon them, and then single out some Instances wherein I shall be more particular.

In general therefore I say, 1. That all those Instances and Ex­periments produced to prove such a Weight or Elasticity of the free Air, that may be capable of effecting the phaenome­na in the Torricellian Experiment, yea or in the Magdeburgh Instrument, or the English Air-pump, are all capable of ano­ther Solution, as appears by the an­swers that Linus hath given to them, which I need not repeat.

2. That the application of the Weight and Elasticity of the Air to the Solution of these phaenomena, is forced, streined, and in many instances contra­ry [Page 202]to the evidence of Sense; so that though the appearances themselves are true, yet those Causes assigned are very inevident, full of difficulties and absur­dities, and require such a train of supple­mental Suppositions to make them but Tolerably applicable, that no man dis­ingaged from a party can easily subscribe to them.

3. That there are some Instances and Experiments that are so untractable to this method of Solution, that all the inventions of the most Mercurial wits and highest ingaged in the patronage thereof, cannot by any means relieve it.

4. That the plain and common So­lution of them by the inseparability of Bodies, and the fuga vacui, (pleasantly by some stiled decantata olim fuga vacui) doth most naturally, and without any stress offered to Sense or Nature, answer all Instances and difficulties, and fails in none.

5. That it is most evident to any man, that without prejudice or partiali­ty shall observe it, all or the most part of those Instances and Experiments, [Page 203]which (to serve the hypothesis of the gra­vitation and Elasticity of the common Air) are resolved into Pression or Ela­sticity of the Air, are plainly performed by Suction and Attraction of the Air, when put under a great tension or rari­faction, which wholly subverts the So­lution by Pressure or Elasticity of the Air.

Now as to some particular Instances.

First, we are told that the Torricellian Engin, wherein at the bot [...] of the hill, the Mercury riseth to twenty nine Inches and half, carried up to the top of the hill Puy de dome in France, subsided three Inches: and some Instances of like nature given in Lancashire, it sub­sides neer two Inches. From whence it is inferred, that this variation ariseth, because upon the top of the Mountain, which was 3000 foot high, the column of the Atmosphere was shorter, and so gravitated less upon the restagnant Mer­cury, than it did at the bottom of the hill, which caused the disparity of the position.

I answer, admitting the fact true, yet [Page 204]the cause assigned is non causa pro causa, or at least we have no sufficient evidence that this is the cause.

The various Elevation or depression of the Mercury is not in respect of the height or lowness of the place, where the Instrument is used, but in respect of the temperamont of the Air wherein it is used. The Excellent Author tells us, in his eighteenth Experiment, that the Torricellian Engin placed in his Chamb [...] window for a good season, the Mercury had various Elevations and subsidings, according to the temper of the Air; and that this variation was considerable, namely two Inches, and that in cold weather, contrary to the use of other Weather-Glasses, it fell much lower than at other times. And if this beso, it is no wonder, at the top of the hill, where the Air was much colder, it might subside considerably from the height it had at the bottom.

But whether it were colder or hot­ter, yet certainly there is that difference of temperament in the various regions of the Air, that might make a various [Page 205]position in the Mercury. What if we should say, that the vis igneapenetrativa AEtheris is stronger there than below the hill, and so might strongly dilate that small portion of Air upon the top of the hill, though the sense of heat be there less?

But I cannot chuse but observe, that if we should assign this Subsidency of three Inches of Mercury to the shortning of the Atmospherical Cylinder, by 500 Fathoms of perpendicular height; we must necessarily conclude the great mi­stakes in the computation of the gravi­table Air or Atmosphere, and must ren­der it of a prodigious height beyond all the Estimates of the latter Elaterists, whereof some tell us it is seven Miles high. By others Computation that it is 33893 Feet, which is 5648 Fa­thoms, somewhat less than seven Miles.

But if a Mile next the Earth should abate but three Inches in the height of the Mercury, six Miles more would hardly abate three Inches more, viz. six Inches; nor twenty four Miles more [Page 206]would abate nine Inches. For a Mile of Air next the Earth (if the gravitation of the Air should be admitted) would more than ten times counterpoise the next Mile about it, because it hath these advantages, 1. of the greater incum­bent weight of the superior Air, 2. of the stubborn resistance of the terrestrial Globe, whereby it is more constipated and bound together the nearer it is to its reflexion and repercussion. 3. The great concrement and accession that it hath of grosser vapors, and terrestrial effluxes, wherewith the lower parts must needs be more laden than the up­per; so that form the first gravitating particle of Air or Atmosphere to the lowest, it will increase by a Geometri­cal Progression in every part, as 1, 2, 4, 8, 16, or very near it, which will render the lowest Mile prodigiously more weighty than any of the superior Miles.

But I dismiss this business of the gra­vitation of the free Air as a meer No­tion.

The Instances to prove the Elasticity of the Air, are for the most part such as [Page 207]are endeavoured to be made out by the tension or rarifaction of the Air by the Wind-pump, or Magdeburgh Instru­ment. And the answer to any one of them gives an answer to all, for the ap­plication of them to the Elasticity or Spring of the included Air is bottomed upon one common mistaken ground. I shall therefore mention but one or two of them.

The Excellent Author in his Book of Physico-Mechanical Experiments, Exp. 5. gives an account, how a dry Bladder well tied, and blown moderately full, and fastned into the inside of the Recei­ver in the Air-pump, upon a strong ex­haustion of the Pump was broken; and in the 16 ^th Experiment, a Glass included in the Receiver, broken by the exhau­sting of the Air. And in the Continu­ation of new Experiments, Exper. 7 and 9, the same Instance of breaking of in­cluded Bladders and Glasses is repeted, and attributed always to the natural dilatation of the internal Air included in the Glass and Bladder, the circumja­cent Air being rarified by tension.

But the true Solution of both is quite another matter. The Bladder is dilated by the attraction wrought by the tensed or expanded Air, upon the outside of the Bladder, and thereby the included Air necessarily expanded by that force, stretching out the sides of the Bladder that includes it, and when it is capable of no greater stretching it breaks, not by the natural expansion of the included Air, but by the strong tension wrought upon the Bladder by the attraction of rarified or tensed Air in the Receiver, that tears the Bladder.

And as to the Sealed Glasss-bubble, the fracture thereof with that violence is not by the natural Elasticity of the Air included in it, but by the strong at­traction wrought upon every part of its external Superficies, by the tension of the strongly circumjacent tensed Air in the Receiver.

And therefore if the Bladder or Bub­ble were filled with Water, and closed fast, (which is not capable of any natu­ral Elasticity) I make little question but the strong attraction of the expanded [Page 209]Air in the Receiver would break the Glass and Bladder, especially if it have any angles, (though I confess I cannot be very confident of what I never tried.)

And yet if it should succeed accor­ding as I suppose, though the natural Elasticity of included Air would be thereby convinced of untruth; I expect there must be another expedient inven­ted by the Elaterists to salve it, viz. as prodigious a weight in the included Water, as there is supposed an Elasticity in the included Air.

In the late Book intituled, New Expe­riments about the Pressure and Spring of Air upon Bodies under Water, Experi­ment the second, I find this Experiment, which is to the effect following.

Take a Bladder, and squeezing out the greatest part of its Air, tye the neck very close, and fastning a competent Weight to it, place it in a great large Glass, and placing that Glass upon the Air-pump, fill it with Water, and then covering the Glass with a large Recei­ver well luted to the Pump, the Air pumped out of the large Receiver, the [Page 210]Bladder below the Water would gra­dually swell, 'till by often pumping out the Air, the Bladder would be full blown. And the Supposition is this, that the Air being highly rarified and extended in the Receiver, whereby the strength of its counterpressure or Spring was weakned and abated; the little portion of Air in the Bladder, notwith­standing the interposition of the Water, having the advantage thereby of expan­ding if self, did accordingly fill up the Bladder.

The truth of the fact is unquestiona­ble, but the Solution of it by the natural Spring of the Air in the Bladder, is an assignation of non causa pro causa; but the true Cause is, that by the strong tension of the Air in the Receiver, it lays hold and attracts upon all the parts of the Water, and all that is included in it, and the Bladder being within the reach of that forcible attraction, hath its sides thereby distended, and the in­cluded portion of Air expanded and rarified by the tension upon the Bladder; not by any natural Elasticity of the in­cluded [Page 211]Air, but by the forcible attraction wrought upon the external Superficies of the Bladder, and pulling it asunder, whereby the included Air by the com­mon Law of Nature is necessarily ex­panded to prevent a vacuity.

And as if there had been no Water interposed, the Bladder would thus have been extended, and the Air inclu­ded in it expanded, by the strong attra­ction of the rarified Air in the Recei­ver; so the same effect will as necessa­rily ensue, notwithstanding the inter­position of the body of Water: for that vis attractiva of the expanded Air in the Receiver, though it immediately fa­sten upon the Superficies of the Water in the vessel, yet thereby and there with it also pervades the whole body of the Water, which being a fluid body hath thereby a tension made upon it, and all its parts, and all that is included in it.

And the truth of this appears beyond dispute, for the Learned Author in his 19, 21, 22, 23, &c Experiments, tels us, and that truly, that by this pumping and rarifying of the Air in the great Re­ceiver, [Page 212]Water, Spirit of Wine, &c. will be raised to run out of a Glass included in it, & that bubbles will thereby be for­med at the bottom of the included ves­sel of Water: whereof the true cause (whatever be otherwise assigned) is the forcible attraction of the tensed and ex­panded Air in the Receiver upon the in­cluded Water, which strongly per­vades the whole body of Water, pene­trates to the very fund or bottom of it, and puts it altogether into a various agi­tation.

And therefore as this attraction per­vades the whole body of water, so it per­tingeth to the included Bladder in the very same manner as it doth upon the Water, though with a more sensible ex­tumescence of the Bladder, because more capable of it.

We need not resort to a more evident Instance than that common and ludi­crous Experiment, yet taken notice of by Regius, of immersing the small end ( Fig. 13.) of a lighted Tobacco-pipe B under Water in a Vial, and sucking another Pipe C, not touching the water, [Page 213]the Glass being closely covered, the strong attraction of the Mouth upon the one Pipe will, through the Water upon the orifice of the immersed Pipe, draw the Smoak into the other, not­withstanding the interposition of the Water, and will put all the parts of the Water, to the very bottom of it, and the granules of Sand lying at the bottom of the Water, into motion and elevati­on, as in the Figure.

And the very same Answer is most clearly to be given to the third and fourth Experiments in that place, and to others of like nature, without recur­ring to an imaginary natural Elastici­ty in a small portion of included Air, whereby to expand it self without any forcible attractions to such a prodigious amplitude.

And thus I have done with what I have to say against the Solution of the Torricellian Experiment, either by the Weight or Elasticity of the Air or At­mosphere; which to me seems a Sup­position contradictory to our very Sen­ses, a Supposition attended with infi­nite [Page 214]absurdities and inexplicable diffi­culties.

And yet, as I have before said, it is wonderful to see with what tenacity, and with how great confidence it is as­serted, and how marvellously it hath obtained among the gens literata, and what Systems of new Physicks, what rare trains of Consequences, what Pro­positions, porismata, Scholia, it hath mul­tiplied! wherein if the Foundation it self prove but a mistake, men have spent much labour in vain upon it.

Therefore laying aside this Solution as untrue, I proceed to that which the more steady Modern Philosophers, con­sonant to the ancient Principles, have given in this case, and seems to be most consonant to truth.

CHAP. XV.
Concerning the true Cause of the suspension of the Mercury at twenty nine Inches and half, or there about, in the Torricellian Engin.

I Come now to consider of that cause of the suspension of the Mercury at twenty nine Inches and half, or therea­bouts, in the Torricellian Engin.

They that assign the Diversity of the Weights of fluid Bodies, tell us; 1. That although Air be intrinse­cally heavy, yet it is neer one thousand times, or as Mersennus will have it, a­bout 1300 times lighter than the like quantity of Water; and this they en­deavour to evince by Experiments. But this Conclusion is very doubtful and difficult.

2. That Water is fourteen times, or very neer thereabout, lighter than Mercury, quantity for quantity, and this as it is easie to be tryed, so upon try­al [Page 216]I find it very neer the truth, though Water it self in several places differeth somewhat in weight, and therefore it is not casie to make this the common stan­dard for all Waters, though the diffe­rence be not considerably great.

Though Water be ordinarily four­teen times lighter than Mercury, yet this is not the just proportion of the suspension of one and the other in a Tube.

For if a Tube of Water, above one and thirty foot long, stopt above and immersed at the other end in restagnant Water, it will subside as is ordinarily said to thirty and one foot, others say more, whereof see the Experiment apud Schottum in Technicis Curiosis, l. 3. cap. 2. Exper. 2, & 3.

But in the case of Mercury, if the Tube of above twenty nine Inches and half long, suppose four foot, be stopt at the top, and immersed at the open end in restagnant Mercury, it will subside to twenty nine Inches and half, or there­about.

But although in these two fluids, of [Page 217]this different gravity, the subsiding of either vary, yet the reason both of the sub­siding and suspending of the one and the other will be the same.

Therefore what I say in relation to the suspension and subsiding of Mercury, will be in its reason applicable to the other, and therefore I shall here only treat of the suspending of Mercury, be­cause the Instruments to try the Expe­riment in Water are more massy and un­tractable, but, as I said, the reason of one will be the reason of the other.

There be three Instances of the sus­pension of the Mercury in the Torricel­lian Engin, which though they all are resolvible into one common reason, yet that reason hath a various application severally to them.

First, when the Tube exceedeth in length the ordinary station of the sus­pended Mercury, viz. twenty nine In­ches and half, as suppose it be four foot long, and the Tube receive only thirty Inches of Mercury, or though the Tube be filled more than twenty nine Inches and half of Mercury, yet it is not [Page 218]so perfectly filled, but that there remains a portion of Air in the head of the Tube, upon its inverting into the restagnant Mercury.

In this Instance, if the portion of Air be so great before its Expansion, that be­ing expanded by the descent of the Mer­cury, it can reach below twenty nine Inches and half, as suppose to 20, 23, 24 Inches or less, then the Mercury will subside to that scantlet that the portion of Air is extendible unto.

If the portion of Air be less than can be extended, below twenty nine Inches and half, or the distance be so great that the extension of that portion of Air can­not by its expansion supply a greater room than what just answers to that station: as suppose the Tube were above 4 foot long, and filled with Mercury all but half an Inch, and then inverted into the vessel of restagnant Mercury, whereby before its subsiding there would be about half an Inch of free Air in the head of the Tube; and by the de­scent of the Mercury to twenty nine In­ches and half if that little portion of [Page 219]Air were yet so much as were capable of such an extension, it would be extended to that length, viz. eighteen Inches and half; but if that task were too hard for so small a portion of Air to be extended unto, then the same would be supplied by the subsidiary steams and effluvia out of the Mercury, to make a retreat for the Mercury, to a descent of twenty nine Inches and half, as hath been shewn, and shall now farther be declared in what follows.

In this Instance these things are to be noted. 1. That by the descent of the Mercury there is no vacuity left in the place derelicted by the Mercury, as hath been shewn Chap. 2. That there is no new Air admitted into the Tube de foris, as hath been shewn before, Chap. 3. But that little portion of Air is ex­tended from the very head of the cavity of the Tube to the subsided Mercury, if it be of that substance that is capable of such an extension to the Mercurial sta­tion of twenty nine Inches and half: and if it be too little for such an exten­sion, it is supplied by a suitable portion [Page 220]of the Mercurial steams, as hath been shewn. 4. But that extension or dilata­tion of that little portion of included Air, is not by any natural Elatery or ex­pansion of its own, as hath been shewn in the two former Chapters, for it is a portion of the free Air; but it is a strong tension of that portion of included Air, to prevent that casma and separation of Bodies without any thing intervening, or the fuga vacui, so often mentioned by the Ancients. 5. And consequently, though in relation to the laws of the Universe, it be a natural expansion or dilatation of the Air in this circum­stance, in obsequium naturae universalis, 01 yet in relation to the particular state and consistence of that portion of the Air thus expanded or tensed by the subsiding of the Mercury, it is forced and violent. As the erect posture of my Body is natu­ral to me, while it makes one common composition with my Soul and Spirits, and in Concreto, though it be violent in relation to the moles corporea of my Body, which would otherwise fall down to the Earth. 6. And the consequence of [Page 221]this tension of the included portion of Air (considered conjunctly with the na­tural inseparability of the parts of the Universe, which is all one with that which the Ancients called fuga vacui) is the sustentation of the Mercury, that column of descended Air, which Linus not absurdly calls funiculus, being inse­parably united, and adhering to the top of the Tube at one end, and to the Mer­curial Cylinder at the other end, and this funiculus aereus not being capable to be extended farther than to twenty nine Inches and half, being the Mercurial station, by the force of the descent of the Mercury, sustains and holds it up at that station: and so the pondus deprimens of the Mercurial Cylinder is equal to the potentia superne sustinens of the Aereal descended Cylinder upon it, in a kind of aequilibrium, the Mercurial Cylinder by its natural motion endeavouring its descent downward, and the aereal co­lumn by a motion of restitution to its natural size and staple, retracting it as much as it may upward; and the same reason will hold of the portion of inclu­ded [Page 222]Air, be so much as is capable of an extension below twenty nine Inches and half of the Tube: but not sufficient by such a force to be dilated to a full de­pletion of the Mercury out of the Tube, as possibly to 20, 15, 10, or 5 Inches from the restagnant Mercury, in which case the Mercury will subside to such a de­gree, and no lower.

The reason therefore, 1. Why the Mercury subsides so low as twenty nine Inches and half, its usual station, (or lower, if the portion of included Air be greater, as is before said) is, because the weight of the descending Mercurial co­lumn is of that strength, to give the in­cluded Air that tension or dilatation. 2. Why it subsides no lower, is because when the Air hath attained its utmost tension that the descent of that column of Mercury can give it (which ordinarily is at the height of twenty nine Inches and half) that aereal descended Cylin­der holds it there, and keeps it up to that height, the weight of the Mercury being now lessen'd.

And that this is the cause of its susten­tation, [Page 223]appears evidently by these few Instances. 1. If the Tube of Mercury in this sustentation be suddenly lifted up from the restagnant Mercury, there will be a strong resilition of the Mercu­ry towards the top of the Tube, that will endanger breaking it; as we see a Lute­string, if hanged upon a Nail, and o­vercharged with a Weight or strength at the lower end, by which it breaks in the middle, the upper part of it will forcibly resilire in its contraction to its ordinary size. 2. If the Tube be incli­ned to a Level in the same parallel line to twenty nine Inches and half of the erected Tube, whereby it loseth its weight by the incumbence that it hath upon the sides of the declined Tube, the Air will contract it self to its former con­sistency, which it had before that ten­sion, being by this inclination of the Tube delivered from it.

And they that object against the ten­sion of the Air in this case; because if it had a tension in length, as the Lute­string hath, it would have likewise a contraction in its bredth, and so would [Page 224]not fill the Tube, must remember that the Air is a tensible Body of such a na­ture, as is at the same time tensible in bredth as well as length, and in such its tension as closely adheres to the sides of the Tube, as it doth at one end to the top of the Tube, and at the other end to the Mercurial column.

I shall not here enlarge with Instan­ces, to shew, that the tension of the Air, or any other tensible fluid. Body neces­sarily effects attraction on the Bodies to which it is contiguous, but shall reserve that to the following Chapters: and I have been the longer in the explication of this Instance, because it fully opens the reason of the second Instance, which now next follows. Therefore, 2. The second Instance is, where a Tube closed at one end, above twenty nine Inches long, suppose it four foot long, is entirely filled with Mercury, and no Air admitted into it, and then inverted into a vessel of restagnant Mercury, without admission of any Air into it, either upon its inversion or im­mersion, (which though it be difficult, [Page 225]may yet be done) in this cases the Mer­cury will subside to twenty nine Inches and half in the Tube.

This derelicted space of eighteen Inches and half, is, as I have before said, filled with a Mercurial steam or vapor, extracted out of the Mercury it self, and abraded from it by the descent and compression of the parts of that Mercu­rial column, as I have before shewn Chap. and thereby likewise rarified or tensed, as the Air is in the former In­stance.

And this being either real Air inclu­ded within the pores of the Mercury, and expressed from it, or else a subtle Ingredient into the Mercurial compo­sition, and extracted, and in its extra­ction dilated, as the Air is in the former Instance. It performs the same office in relation to the suspension of the Mer­cury, as the included extended Air did in the former Instance, and therefore it need not to be repeated.

Only I shall adde this farther, 1. That it appears the extraction of the subtle effluvia, and their dilatation, is perform­ed [Page 226]with a great stress or straining of them out of the Mercurial Body, and with little less labour extended; which appears by the slow descent of the Mer­cury, arising from the lucta or contest that grows between the weight of the Mercury descending on the one hand, and the straining and abrading of those subtle particles, and their tension or rarifaction of the other hand. And the like slow descent there appears in the first Instance, especially as the Mer­cury more and more subsides; for then the Mercury having neer acquired its ordinary station, grows lighter, and the strength of its pressure begins utterly to languish and decay too, being neer equally matched with the potentia susti­nens of the extracted subtilized particles in this Instance, and by the tension of the Air in the former instance; the rea­son whereof shall be farther enlarged, when I come to the third Instance. 2. Whereas in the former Instance, by the inclining of the Tube, the Air re­gains its former contracted extent, here by the inclining of the Tube these sub­tle [Page 227]particles extracted out of the Mercu­ry, and dilated, are not only contracted, but refumed into the Mercury from which they were extracted, as is shewn in the Chapter. 3. That upon the over sudden Elevation of the Tube out of the restagnant Mercury, there will be the like resilition of the Mercury into the top of the Tube, as in the former in­stance.

By this funiculus subtilis materiae the Mercurial column is sustained at twen­ty nine Inches and half, as in the former Instance of the funiculus aereus.

But now how it comes to pass, that since there is yet remaining twenty nine Inches and half in the Tube, which doubtless hath a residue of subtle matter extractable out of it, to supply a grea­ter room, that what is yet left above twenty nine Inches and half, how it comes to pass that by the weight of that twenty nine Inches and half of Mercu­ry, there is not more of the Mercurial effluxes extracted and dilated, which may give a total descent and evacuation of the Mercurial column into the re­stagnant [Page 228]Mercury remains to be con­sidered, which shall be done in the third Instance which follows.

3. The third instance is, when the Tube is but just twenty nine Inches and half, or shorter, suppose 25, 20, 10, or 5 Inches long, and filled entirely with Mercury, and then inverted into the vessel of restagnant Mercury; in that case the entire Mercury will remain sus­pended, and remain contiguous to the top of the Tube, and no part will de­scend, neither will there be any such funiculus of Air or subtle Matter to con­nect it to the top of the Tube.

The reason of this is what in effect was given in the former instances, though the application be disserent.

First, if in this instance the Mercury should any whit subside, either it must leave the interstitium between it self and the top of the Tube vacant of any Body, or it must yeild some subtle matter to supply the place it leaves abraded from it self, as in the second Instance. And if it can do neither of these, manet sors tertia, only to continue its station united to the top of the Tube.

The former of these cannot be, for I have supposed, and shall further inforce the contradiction of the Law of the U­niverse to that Supposition.

Therefore it remains, that either there must be a subtle matter extracted out of the included Mercury, or of necessity the Mercury must hold its entire pos­session of the whole Tube.

Although the remote cause of this extraction of subtle parts out of the Mercury, in the second Instance, be that law of the Universe, to hold toge­ther the continuity of its parts, and con­sequently to avoid a vacuum or casme in the Universe destitute of matter; yet the immediate cause of this extraction and rarifaction is the descent of the Mer­cury from the station that it hath, and the weight of its Body is the cause of that descent.

And because it requires a strong com­pression of the Mercury, either to drive or draw out this subtle matter, and as it were to rake it out of the bowels of the Mercury, and to extend it, and conse­quently a strong weight to effect that [Page 230]compression and extension, if that weight which it hath at 29 Inches and half, or under, be not effective of such an abrasion or extension of the sub­tle matter so abraded; such abrasion or extension not being effectible by that weight, the column of Mercury must hold its position, and becomes its own funiculus, and remain suspended to the top of the Tube.

Now it seems, that although a Mer­curial Cylinder of a height above thirty Inches, as suppose three or four foot, hath such a forcible pressure, weight, and gravitation upon the restagnant Mercury, not only to drive down the Mercurial Cylinder to twenty nine Iches and half, but also to extract and strain out of it, and extend a sufficient portion of subtle matter out of the Mer­curial Body to supply the room it leaves; yet that the weight only of twenty nine Inches and half, or below it, will not be able to drive, or draw out, or extend a portion sufficient for that Exigent.

And that is the reason, why at twen­ty nine Inches and half, or under that [Page 231]gage, whether the Tube be just twenty nine Inches and half, or longer; yet the Mercurial Cylinder rests there, wanting a sufficient potentia below that station by its weight, to extract or to rarifie any of its subtle parts, to supply the place which then it should desert or leave.

And herein the bigness or smallness of the Glass Tube, or the Mercurial Cy­linder included, makes no odds; though possibly according to the various dia­meters of the Tubes, one Cylinder of Mercury of 29 Inches and half high, may weight five times another Cylinder of the same height, and yet both would remain suspended in the Tubes.

But the disparity of the potentia de­primens, is from the disparity of the height of the Tube. And therefore the cause why the Cylinder of Mercury, filling a Tube of 3 or 4 foot long, will subside upon inversion unto twenty nine Inches and half, and there stay, is, be­cause before its descent to that station, its potentia was sufficient to abrade and extend the subtle matter, but at twenty nine Inches and half that potentia was spent.

And therefore the reason why the Tube of twenty nine Inches and half, or under, doth not subside at all, but re­mains cohering to the top of the Tube, is, because it hath not that potentia at that gage to abrade from it self matter to supply that place, if it should leave it.

And for this purpose it will not be amiss to take notice of what Galilaeus, and after him the Excellent Mersennus have given us in relation to the dispa­rity of the motiva potestas of the same fiu­id in different positions of height or ele­vation.

The acceleration of motion of heavy Bodies is ut quadr at a temporum, in which they move downwards; as if in the first Minute, a Body moves one foot, in the second minute it will move four foot, viz. two times two; in the third minute nine foot, viz. three times three; or, which comes to all one ac­count, heavy bodies in their descent, in every given portion of time, as a minute will percur portions of space per numeros impares ab unitate; as if in the first mi­nute [Page 233]it descend one foot, in the second it will descend three foot, in the third five foot, in the fourth minute seven foot, and so onward.

Mersennus partly upon this, Theory, and partly upon his own experience, makes two Conclusions, (which I have experimentally found true) that are ap­posite to explicate what I mean in this matter.

First, if there be two vessels of equal height, but of differing diameters, and with an equal lumen or hole in the bot­tom of each of them, and both filled with Water; the smaller vessel will in the same portion of time empty from it self as great a quantity of Water as the greater, for the Gravitation of the Wa­ter upon the Lumen is secundum altitu­dinem, not secundum latitudinem vasis: and upon the same account it is, that if the lumen be at the side, and the vessels be placed in the same horizontal paral­lel, the Parabolical line made by salient Water out of each vessel, will be of the same length and amplitude.

2. That if there be two Tubes or [Page 234]vessels of Water, A and B, of the height of nine foot, containing nine Gallons of Water, and B were a vessel of sixteen foot containing sixteen Gal­lons of Water, and each vessel had a small lumen in the side next to the Base, of equal bigness, and of that bigness, that were there but one Gallon in the Tube, it would empty that Gallon in one minute. In these Instances, A fil­led with Water would empty five Gal­lons in the first minute, three Gallons in the second minute, and one Gallon in the last minute. Again B, if filled with Water, would empty seven Gallons in the first minute, five in the second mi­nute, and three in the third minute, viz. in ratione subduplicata altitudinis. And this I have experimentally found to be true.

The consequence whereof is, that e­very fluid Body the higher it is eleva­ted, hath the greater and more effectual pressure by its position upon its lower parts or other fluid, than what barely ariseth from its weight: so that in a co­lumn of Mercury in a Tube of four foot [Page 235]high, though the lowest foot and the highest foot of Mercury be of an equal weight, yet the pressure of the upper­most or fourth foot, which I call its po­tentia deprimens, is to the third as seven to five, and the third to the second is as five to three, and the second to the first as three to one, namely when it hath a liberty of descending motion, as the Mercury hath in this Experiment; for the intermediate weight contributes to the pressure of the uppermost foot.

And hence it is that the power to se­rate and segregate, and strain, and ex­tend the subtle matter out of the Mercu­ry, is vigorous and effective in a Mercu­rial column of 4 foot high, and gradually is less and less 'till it come to twenty nine Inches and half; and then though it hath a considerable Gravitation, yet it is not equal to effect such a separation, and therefore must needs stand suspended at that height, or leave a vacuum behind it, which the Catholick laws of the Uni­verse do not permit.

And thus far touching the Explicati­on of the Solution, which seems to me [Page 236]to be the true Solution of the Torricelli­an Experiment.

And in the next place I shall subjoin some Instances that seem to me to con­firm it, and answer some Objections that are made against it.

CHAP. XVI.
Concerning the two Suppositions that are ne­cessary to maintain this Solution, viz Natures abhorrence of vacuum, and the Attraction of tensible fluids, or other bo­dies when under a tension.

THere are two Suppositions that are necessary to be proved, to render the Solution above given evident or probable. I. The exclusion of a vacuum or space in the Universe wholly empty of any Body. 2. That any Body, capa­ble of tension, or rarifaction by tension, (such as are the Air and thin effluvia of Mercury) to be attractive upon the con­tiguous Bodies, when actually under that tension.

1. As to the former of these, I need not much labour for it, upon two rea­sons. 1. Because there have been large Tractates upon this Position, and to re­peat them would be but actum agere. 2. Because the exclusion of the Gravita­tion and Elasticity of the Air, invented or substituted by the modern Elaterists, doth necessarily conclude, that there can be no vacuum in Nature; for all those Experiments and Instances, which they produce to prove that Gravitation or E­lasticity, and by which they go about to solve them, must (if those Solutions prove untrue, or ineffectual) of necessity maintain that ancient Peripatetical po­sition, because they are uncapable of any other Solution. And in my judgment that Gravitation and Elasticity of the common Air is sifficiently convinced by what hath been before said touch­ing it.

And when I meet with those Obje­ctions that I find used by Learned men, namely how the Mercury or Water comes to know there will be a vacuum, if they do not leave their natural Gra­vity, [Page 238]and so ascend or remain suspended to supply it, and how those stupid inani­mate Elements or Minerals come to un­derstand, that Nature so much abhor­reth a vacuum; are much of the same kind, as if a man should ask the Sun, if it move according to Ptolemy; or the Earth, if according to Copernicus it move; how they came to know that when they come to the Northern Tropick, they must move again to the Southern Tropick? or when it hath touched the Southern Tropick, it knows that it must come back to the Northern, and steer its course accordingly? Or as if a man should ask, how doth the Stone under­stand that he must descend, when yet all the men in the world can never give any satisfactory reason for its mo­tion to the Earth, more than to the Moon, but only Nature that is the prin­cipium motus & quietis, or rather the God of Nature, whose standing and statumi­nated Law Nature is, hath so order'd it, and ordered so in the best way for the use, beauty, and accommodation of the Universe. The plain truth of it is, the [Page 239]very consideration of the many attempts that have been made to explicate the reason of the descent of heavy Bodies, is enough to let us see, that we tire our selves in vain to determine the clear reason of it, without resolving it into the statuminated Law of Nature: though the Stone and the Earth are ina­nimate, or at leaft unreasonable Bodies, such kind of Objections therefore as these are fond and weak.

2. As to the second, namely the at­traction of Bodies extended, whether by rarifaction or tension, especially of the Air, or this subtle matter that ariseth from the Mercury. This affection and effect is as natural as any thing in Na­ture, as is truly observed by the learned Fabri, in primo tractatu physico, prop. 205, 206, 208. For a strict contiguity in all parts of several Bodies is a kind of con­tinuity of the Universe and all its parts; neither can I imagine how those that are fond of the Epicurean hypothesis, can better maintain the cohesion of the parts of solid bodies, their atomi hamati being but fancies of what men never saw in them.

The Air is the common cement and connecter of the different parts of this in­ferior world at lest, and strictly inter­poseth between their fissures and inter­stitia, to maintain a kind of common continuity between the different parts of the Universe, and makes it as it were one continued Body.

But to come to particular Instances, which shall not be laborious but familiar and common, to evince this cohesion of the parts of tensed or rarified Air, and the contraction that it makes upon con­tiguous bodies, in its endeavour of re­stitution to its natural state and consi­stence.

1. The instance of Cupping-glasses, where the Air is highly rarified or eva­cuated by the included burning Tow, and applied to the flesh, draws up the flesh strongly unto it, when by the ex­tinction of the Tow the rarified Air con­tracts it self to a narrow room, which can be no otherwise than by the cohe­sion of the particles of Air to the skin, and driving it in to the Glass, while it contract, it self to a narrower [Page 241]compass. And certainly they that tell us, that this is done by the pressure of the ambient Air upon the contiguous flesh, which thrusts it up into the Glass, either do not believe themselves while they say it, or are so transported with a love unto or ingagement for their belo­ved hypothesis, of the prodigious gravi­tation of the free Air, that they are con­tent to say any thing in its behalf.

Qui amant ipsi sibi somnia fingunt.

Shottus (who while he wrote his mi­rabilia hydraulica, was well satisfied with the Solution of the Torricellian Experi­ment by the common Solution of fuga vacui) was indeed afterward, when he wrote his mirabilia Magdeburgica, con­verted to the new Solution, being not willing it seems to be thought to see less in Nature than the new Tribe of Virtuosi that were concerned in that Engine. But for all that, this Instance of Cup­ping-glasses was too hard for that new Solution, and were fairly fain to have recourse to the decantata fuga vacui, or else it must stand unsolved, and so must any else that means an impartial and [Page 242]unpreingaged search into Nature.

2. If an empty Bladder be tied close about the neck, and fastned to the top of the Tube, Hermetically sealed in the Torricellian Experiment, upon the sub­siding of the Mercury the Bladder will be expanded, not by the natural Elate­ry of the little particle of included Air, but by the strong attraction of the tensed Air in the Tube, by the descent of the Mercury, whereof before.

3. The Instance given in the tenth Chapter, of the Tube heated, and ap­pended to a Ballance, so as it touch the Water, the Water rising in the Tube, the Tube will be drawn down, which is only done by the adhesion of the two extremes of the inclosed rarified Air, the one Extreme laying hold upon the top of the cavity of the Tube, the other end laying hold of the Water, and drawing it up, and therewith necessarily drawing the Tube down, whilst the included Air is contracting if self to its natural and narrower dimensions.

And because the Experiment made by a wide-mouth'd Glass would yeild [Page 243]some discoveries of this attraction by the rarified Air, which are not so visible in so narrow a Tube, I took a Beer-glass, as in the Figure 14, and suspended it by a Thrid to one Scale of the Ballance, and weighing it with a weight in the op­posite Scale, and found it weight two Ounces and half; then, as we used when we were School-boyes, sticking up a Candle in a Bason, I let down the Glass over the Candle contiguous to the Superficies of the Water, the Can­dle going out there was a portion of Water drawn up into the Glass, the Air upon the Candles going out, and the Glass drawn down into the Water, the included Air being under a cause of ra­rifaction, namely by the heat of the Candle, and by the extinction of the Flame now gradually contracting it self, and thereby drawing up the Water to supply that place.

The water drawn up into the glass was about half an Inch; we marked exactly the weight that was required now to lift up this Glass and included water was an addition of 4 Ounces and ¼ ⅛ of an [Page 244]Ounce; so that the whole weight that raised the Glass and Water inclosed, and severed it from the Water beneath, was six Ounces ½ ¼ ⅛ of an Ounce, and then, though not without reluctance, the Glass was raised out of the Water.

Then taking the exact quantity of other Water, equall to that formerly included in the Glass, (which was not difficult to do by the help of the remai­ning Mark) we weighed it, and found it to weight exactly three Ounces and half, and a very few Grains.

So that the weight of the Glass and inclosed Water amounting to six Oun­ces, there was requisite an addition of about half an Ounce to sever the Glass from the Superficies of the restagnant Water, which did apparently to the eye and touch adhere together, not­withstanding the counterpoise of six Ounces, equal to the weight of the Glass and included Water.

And this half Ounce of additional weight was due purely to the adhesion of the glass, Air, & inclosed water to the Superficies of the restagnant Water.

1. It seems evident, that not only the Glass, but the Water included in it, gravitates upon the Scale, for the coun­terpoise of six Ounces in the opposite Scale, equals the weight both of the Glass and Water inclosed in it, which could not be, unless both contributed to the aequipondium.

2. That it is impossible that the in­cluded Water could gravitate upon the Scale, unless the rarified Air were con­tiguous and cohering to the top of the Glass, and also to all the parts of it in­cluded within the cavity of the Glass above the Superficies and whole body of the included Water, and also firmly adhered to the Superficies of the inclu­ded Water, for they all make up but one common weight, and there must be a vinculum that must connect the Glass and the inclosed Water, and otherwise they could not gravitate together; so that the vinculum that binds the Water to the Glass is this funiculus (as Linus well calls it) of the rarified Air, as the Thrid is the vinculum that binds the Glass to the Scale: for otherwise the [Page 246]Glass would be only raised, and leave the Water to subside into the vessel of restagnant Water, and would never hold an aequipondium to more than two Oun­ces and a half, which was the just weight singly of the Glass.

But as for the fancy above mentioned, Chap. 10. that it is not the Glass and Water that make up the weight of six Ounces, but the Glass and the column of Air incumbent upon it, the vanity of that imagination is sufficiently convin­ced in that Chapter.

3. That consequently, the included rarified Air thus fastning upon the ca­vity of the Glass and the included Wa­ter by a strict cohesion, according to the nature of tensed fluids, contracting it self as much as it can by its motion of restitution, draws up the Water in the vessel into the Glass, and raiseth it as high, 'till there be an aequilibrium be­tween the pondus naturale deprimens of the Water, and the potentia sustinens of the Air, thus now contracting it self, and indeavouring its restitution to its just natural dimension.

4. As a specimen of this cohesion of the Air and Water included in the Glass, there is also a cohesion of the Limb of the Glass and the included Water unto the Superficies of the restagnant Water, which requires half an Ounce of weight to break that continuity between the upper and lower Water. And no other imaginable cause can be assigned for it, but that Natura aegrè patitur disjunctio­nem partium continui.

And as with the hand you lift up the Glass towards the Superficies of the re­stagnant Water, the Water included will rise with it much above the Super­ficies of the external Water, which can­not be by the imaginary pressure of the external Air, but by the adhesion of the column of Water to the included ten­sed Air, and of that to the concave Su­perficies of the Glass per modum unius con­tinui, which any man's tryal will make more plain and evident to him, than words in writing can easily express.

But some exception is taken to the word funiculus, and we are asked what Grappers there are belonging to this fu­niculus, [Page 248]that can so steadily lay hold of the Water and the Glass, and hold them thus tight togher?

And I must confess, that I wonder, that any that approves the Atomical or Epicurean Philosophy, can make that Question, since all their pretence of the cohesion of the imaginary Atomical Particles in any the most solid continu­um, are certain atomi hamati, that in­terlock one in another, which yet they never saw.

But let it be: I answer, the power of the laws of Nature are so efficacious, that they can and do colligate strictly parts even of most distantial textures and consistences, without the help of Vellicle, Hooks, or Grappers. What are the Hooks or Grappers, whereby the Humane Soul and Body, yea the Souls and Bodies of Animals are knit together, whereby the Bloud and the Spirits are colligated, whereby the Load­stone attracts the Iron, notwithstanding an interposed Plate of Brass or body of impervious Glass, and a thousand more Instances of Attraction between Bodies, [Page 249]without the intervention of sensible Grappers and Hooks, or such gross Mechanismes.

This, and some other as light as this, and some toying with the word funicu­lus, are the greatest Objections that I find against what Linus hath in this matter delivered, which seem to me of no moment. Words were made to ren­der Conceptions of things, and if they do that, they do their office.

And thus far concerning the Soluti­on of the Torricellian Engin. I shall adde a few words, as I promised, touching the cohesion of two polished Marbles, and the insufficiency of the Solution thereof given by the Elaterists, and the truth of the ancient Solution thereof.

CHAP. XVII. Concerning the Cause of the Cohesion of two polished Marbles.

THere are two Experiments, for the Solution whereof the Gravitation and Elatery of the Air is by the late Phi­losophers applied, which in this last place I shall examine according to my premised method.

The first is that of the cohesion of two polished Marbles. For instance, take two polished Marbles, of one dimension and figure, and exactly in the centre of each Marble let there be a Ring, where­by to suspend the upper, and whereby a weight may be appended to the lower. These two Marbles, especially if their smooth sides be a little oyled, and applied each to other, will adhere so strongly together, that the upper being suspended by its Ring to a post or frame, ( Fig. 15.) the lower will sustain a weight of 20, 30, or 40 pounds, though the [Page 251]Marbles be not above three Inches dia­meter.

And as it will do this in the open Air, it will also perform the same, though the Marbles be inclosed within a close large Glass-Receiver, whereby it is seve­red from the common Air, or any im­pending column of the Atmosphere.

The reason that the vulgar Philoso­phers were wont to give in these cases are these: First, as to the strict cohesion of the two Marbles, they give this reason; that the cohesion is ob fugam vacui. For if they should be severed by the appended weight, the separation of them would be in the same indivisible moment, be­cause they do contingere in puncto.

And in as much as all Bodies move successively, and not in an instant, it would be impossible for the circumam­bient Air in the moment of the separa­tion of these two Marbles, to pervade the whole interstitium that would hap­pen upon the first separation, and con­sequently there would be a mean time wherein the interstitium would remain [Page 252]empty, therefore the cohesion is so ob­stinate to prevent that monster in Na­ture, namely vacuum.

And to evidence that this is the rea­son, they say that if the aperture be at­tempted at the sides, either by pulling them at one side, or by appending the weight more to one side than the other, they are easily separated, because that aperture makes an Angle, ( Fig. 16.) and gradually admits the Air into it; for then the aperture is not all at once, but is apertio continuata from the first ope­ning. For although if the Base of the acute Angle, viz. A, were but a hairs breadth, the Angle were divisible Ma­thematically unto the uttermost extre­mity of it; yet it is not so Physically, it but gains a successive latitude, accor­ding as it gradually opens, and so is ac­commodated Physically to a successive intromission of the Air: but if the aper­ture were altogether, the separation in all parts of the Superficies must be Phy­sically as well as Mathematically in the same instant, which were too quick to give an admission to the successive mo­tion [Page 253]of the aery body in the same instant.

But now we will consider what So­lutions the late Philosophy gives in this instance.

Namely I. That in the free and open Air there is an impending column of Atmosphere, reaching from the summi­ty thereof to the upper Marble, and com­mensurate in its diameter and circumfe­rence to the area of the upper Marble that presseth it, with an excessive weight downwards, and so upon the upper Hemisphere if suspended parallel to the Horizon.

2. That again there is a returning or recoiling Cylinder of Air, reaching from the Superficies of the Earth up­wards, of as great a potentia sustinens as the superior column of Atmosphere hath a pondus deprimens: and this infe­rior or resulting column is commensu­rate also in its diameter and circumfe­rence to the lower Marble, or brazen Hemisphere, and thrusts that as vigo­rously up to the upper Marble, as the upper column presseth downward. And so the potentia sustinens being equal to [Page 254]the pondus deprimens, the lower Marble is able to sustain a weight equal to the weight of the upper atmospherical Cylinder; the reason of which admi­rable power (according to their Suppo­sition) is opened supra cap. 5.

3. And in as much as there runs down as weighty and potent aereal Cy­linders or Atmospherical portions by the sides, as well as perpendicularly, therefore although the Marbles were not placed parallel to the Horizon, but vertically (as when each is drawn seve­ral ways) this lateral pressure of the At­mosphere is as effectual to hold the Marbles together in that close posture, as if they stood parallel to the Horizon.

4. And because they will have a Salve for all Sores, although these En­gins be placed in a close Glass-Receiver, whereby the aereal Columns, as well superior as inferior, are wholly inter­cepted by the interposition of the great Glass Receiver, the Elasticity of the portion of Air included within that Glass Receiver, undertakes and effectu­ally performs the phaenomenon, by its vi­gorous [Page 255]Elasticity or counterpression both upward, and downward, and late­rally, upon the included Marbles or He­mispheres.

And this is the Solution that now ob­tains among the Virtuosi.

And upon these premises there are ad­mirable trains of Philosophical Conse­quences deduced with great industry and subtlety, in this particular instance of the Marbles, which a man may read at large in the late book of Hydrostatical Experiments, Exp. 13, and elsewhere.

And now for ought I know the mat­ter is brought to this issue, whether this or the former Solution be the truer, (for I know not a third) and if this prove un­true or uneffectual, the former of the Vulgar Philosophy must obtain, 'till some third be found out.

And therefore I will proceed in the examination of this new Hypothesis.

And although I think I have said e­nough against this whole Scheme of the Gravitation and Elatery of the Air, as it is propounded in the fourth, tenth, and eleventh Chapters; yet I shall here add [Page 256]some things more specifically applicable to these Engins and Experiments, and remit the Reader to those Chapters, as to the general untruth of the entire hy­pothesis.

First therefore, as to the cohesion of the Marbles I offer these considerations: 1. It is plain, that the lower Mar­ble, if there were nothing else to sustain it but the recoiling Cylinder of Air im­pelling it upward, it would certainly fall to the Earth, notwithstanding that imaginary potentia; for if it were other­wise, it would be a necessary conse­quence, that though it were not conti­guous to the upper, it would be sustai­ned by that potentia sustinens, and so we should have Milstones floting in the Air, according to the fancy of the last men­tioned Author of Hydrostatical Expe­riments.

But the help for this is, that in that in­stance the impending superior column of Air being of equal strength with the recoiling column of Air, there is an aequipondium between that pondus and po­tentia, and so the solute Marble or Mil­stone, [Page 257]having the advantage of his own weight, and the weight of the superior column would conquer the inferior; but here the inferior Marble is protected from the weight of the superior column of Air, and so hath nothing but his own weight to contend with the infe­rior column, and its potentia, which lat­ter overmatcheth it, and so keeps it sus­pended.

But this will not cure the Sore; for suppose it were two pieces of Wood, or that the Marbles were not excellently polished, so that they did not contingere in puncto, but some little fissure or inter­stitia did let in any small portion of Air, the Marble would fall off; and yet there the lower Marble is protected from the impendent column of Air by the supe­rior piece of Wood, or unpolished Mar­ble as well as here.

And to say these little filaments of in­terposed Air, which if all put together would not make a column of Air of a larger diameter than a small pin, should conquer the reflected Cylinder of Air, and its potentia, which these Masters [Page 258]suppose to be equivalent in power to thirty, forty, nay one hundred pound weight, renders the whole Supposition it self to be but utterly improbable. Some what therefore else it is, that keeps the lower Marble suspended to the up­per, and not the imaginary potentia of the reflected column of Air commensu­rate to the area of the inferior marble.

2. If the lower Marble were sustai­ned upon the account of the potentia su­stinens of the inferior column of Air, and by force thereof it could sustain (for in­stance) forty pounds weight, suspended in the center of the Marble, it were not easily conceptible how if but an eighth part of that weight were hanged near the limb or circumference of the lower Marble, it would fall asunder, as it will; for the potentia sustinens of the subjected column of Air is applied equally to all the area of the subjacent Marble. And the separation will follow, if the Mar­bles being oyled, the one may be slided off from the other without any dif­ficulty; and then when they are so sli­ded off, they are easily thereby severed, [Page 259]because no vacuity or instantaneous motion of the Air would follow there­upon: which could never be done, if they were so strongly wedged up one to another by so strong and powerful a counterpressure of the reflecting column of Air, which presseth up according to the new hypothesis with a potentia able to sustain neer a hundred pound weight.

3. Stevinus tells us in the observa­tions upon the tenth Proposition of his Hydrostaticks, that if a vessel be made in the form of Fig. 17. with a hole in the bottom, and a piece of Wood lighter than Water, viz. B B. Cover that hole, and then let the vessel be filled with Water; as great a strength will be required by the string at A to move that rundle of Wood from the hole it stops, as if a weight of Water commen­surate to the area of the rundle, from B to A, were impendent upon it. And this the Learned Author of Hydrostatical Paradoxes avouches to have tried him­self, and yet the Water included is not an half nor a quarter of that weight of Water. And the column of Air that [Page 260]these Masters suppose to press the Water at A, can be no larger than the orifice of the Pipe at A, which is not one fifth part of the amplitude of the rundle B, nor of the hole which it stops. But if there were such a reflected or recoiling column pressing upward to the hole of the vessel and rundle that covers it, which is five times larger than the ori­fice at A, to let in a column of gravita­ting Air; this rundle, and the Water incumbent upon it, should be forcibly thrust up by the recoiling column of Air: and yet Experience tells us, that it is so far from being thrust up by the po­tentia sustinens of the inferior aery co­lumn, that it is hardly to be raised with­out difficulty by a Thrid.

4. Again, take a vessel of Laton, of a cubical or cylindrical figure, about eight Inches diameter; make a round hole at the bottom of four Inches dia­meter. Then take a round piece of Brass or Lead, or smoothed Wood, of six Inches diameter, which may weigh two Ounces; wax it well, and exactly, and closely cover the hole, that it may over­lap, [Page 261]that no Air may go in or out by it, then rarifie the included Air, but not to a­ny considerable height, for then growing cold it will draw up the cover when clo­sed. Then close the top very close with Laton and Soder, that no Air can get in; the Air I suppose rarified may take up more room than its natural dimension by about two square Inches, which is more than the dimension of the Stopper: so that the supposed Elatery of the Air hath no resistence to its impelling up­ward, because it hath room for its re­ception. I say that this Stopper will not be impelled up by the pressure of the recoiling Cylinder of Air, though it weigh but two Ounces, and will be lif­ted up by a force or weight of three Ounces. And yet according to these mens Supposition, this recoiling column hath a potentia to impell or keep up for­ty pound, nay an hundred pound weight, being commensurate in power to an Atmospherical Cylinder of six Inches diameter, which according to their Supposition must weigh about 500l weight, namely a Cylinder of [Page 262]Mercury of six Inches diameter, and twenty nine Inches high, viz. 783 square Inches of Mercury, which is near 500l weight. It is true I have not tryed this, but my observation of the third Ex­periment makes me little doubt of this.

CHAP. XVIII. Concerning the Magdeburgh Hemispheres, and their Cohesion, and the reason thereof.

THE Air is capable of tension by force, and of rarifaction by heat; both which agree in this, that they both give a large expansion of a less portion of Air into a greater space than is natu­ral to it.

But herein they partly differ, and partly agree; that the immediate effect of a strong tension of Air by force (such as are the Air-pump, and the Magdeburgh Engin, and the Cacabus Evacuatorius de­scribed by Shottus in his Technica curiosa, lib. 1. cap. 5. & sequentibus) is attraction of the Superficies, to which the inclu­ded tensed Air is contiguous.

But the immediate effect of rarifaction [Page 263]of the Air, which is performed by heat, is a laxation of the filaments of the Air at first; for the Air being dilated, takes up more room, is more relaxed and ex­panded: but consequentially there fol­lows a contraction as the heat decays, and the Air endeavours its restitution to its natural texture, and so endeavours its contraction, and consequently lays hold on the contingent Superficies, within which it is imprisoned, and at­tracts it with its own contraction. The instances of both which motions and effects we have in the Magdeburgh He­mispheres described by Shottus, ubi supra, and hereafter more fully explicated.

Fig. 18, 19, 20. The Engin is thus described. Let there be two Brazen con­cave Hemispheres AB, with rings in the Poles or center of the convex Super­ficies of each of them at C and D, and a ring of Leather dipt in Wax to be placed between the two Hemispheres, viz. E, to keep the limbs or joints of them close from admission of any Air between the commissures or joints of the Hemi­spheres; and a Stop-cock in the lower [Page 264]Hemisphere at E K, both the Hemi­spheres conjoined with the Leather be­tween them. These Hemispheres thus joined, the Stop-cock at F to be left open, whereby in the Cacabus Evacuathius or Magdeburgh Engin, the Air in the cavi­ty of the Hemispheres may be as much exhausted as may be, and consequent­ly that which remains being thereby put into a great tension, to be inclosed by turning the Stop-cock, that no for­reign Air may be admitted. These He­mispheres thus ordered, will cohere so strongly together, that the strength of many Horses will not sever them, if the Hemispheres be large.

And the event is infallibly true, but the contest is touching the reason or So­lution of the phaenomena.

The modern Philosophers, with Schot­tus in his fourth Book of his Technica cu­riosa, cap. 7. (reversed §) 3. (being now a Convert to the Gravitation of the Air) tells us, that the reason hereof is, that the weight of a column of Air impendent uppon the upper Hemisphere, and the reverse column of Air pressing upon [Page 265]the lower Hemisphere upward, is the cause of this cohesion.

And that in case the Hemispheres be not placed erect, but laterally, with their Poles parallel to the Horizon, the lateral pressure of the two adverse columns of Air perform the business, and keep them strictly together against a most powerful force indeavouring their se­paration.

But still with this caution, that the separating force work upon the centre of the Hemispheres, and so draw upon all parts alike: for if the potentia sepa­rans be applied unequally, viz. at one side of each Hemisphere, and not equally from the centre, then the separation will easily follow upon the application of a small separating strength, which is also most certainly true. Again, if but a little portion of Air be let into the Stop-cock, the separation of them quickly follows, which is also true.

But now the vulgar Speculators think, that this Solution is untrue, and that the true reason of the cohesion of these Hemispheres is, because that the [Page 266]included portion of Air is not wholly exhausted, neither is it possible by hu­mane power wholly to evacuate it. But a great part therereof is exhausted, and that which remains inclosed is un­der a very great and violent tension, and hath a strong natural conatus of restitu­tion to its natural staple and standard, and that the filaments of the Air lay hold upon every point of the concave Superficies, and draw them inward, as it endavours its own contraction.

That there is not, nor can be, any casma or interval of empty space be­tween the convex Superficies of the in­cluded Air, and the concave Superficies of the including Hemispheres, for that is contrary to the common law of Na­ture; and yet the Air by its intrinsick texture, and proper motion of restituti­on, to that just dimension that Nature hath assigned to it, affects its own con­traction to its own state, and with it draws together, and holds together the ambient body including it.

Not much unlike the tension of Lute­strings, highly wound up by their Pins, [Page 267]which have a tension and contraction of the extremes, to which they are fast­ned, namely the Bridg and the Pins.

That the reason why, if any Air be let in, even at a Pin-hole through the Hemispheres, it is greedily sucked in by the tensed and stretched Air, to relieve it from the Rack upon which it is stretched, and being taken in it relieves that tension, looseneth its contraction, and takes off its forcible attraction upon the concave Superficies of the including Hemispheres, and gives the included Air a fair relaxation to its due size, sta­ple, and standard; and so the cohesion ceaseth.

Fig. 21. That the reason why an a­perture is easily wrought, when the di­vulsion is only of one side, is partly the same with the reason of the like divul­sion of the the two cohering Marbles. 1. Because the aperture is angular, and not all at once. 2. The aperture is cunei formis, which every body knows is more forcible than a parallel aperture. And 3. by this kind of angular opening the filaments of the Air are broken suc­cessively [Page 268]one after another; but in a pa­rallel aperture all the filaments must be broken at once, and so make one com­mon resistance to the force. As a piece of Cloth may be torn with ease by one man, when thrid is broken after thrid, but cannot be torn by four men, when all the thrids are strained together, and so have an united and uniform strength and resistance.

And they say, that although this En­gin is contrived with great pomp, yet in truth it is no more than that Experi­ment, which we practised with our Nutshels when we were children, where by clapping half a Nutshel to our lips, or the back of our hands, and suck­ing out the Air, they would stick so close, that we could not easily fillip them off.

These are the two reasons that con­tend for the Solution of this Experi­ment, the Gravitation of the Air or Atmosphere of the one hand, and the motus or conatus restitutionis of the Air, and the natural inseparability of Bodies without any intervening Body of the [Page 269]other hand. If the former be laid aside as untrue, the latter needs no great la­bour to prove it; for these be the only two Competitors for the Solution of this Instance, that I ever heard of.

And I think it is very plain, that the imaginary gravitation of the Air, nei­ther hath nor can have any thing at all to do in this business.

And because I had not those Evacua­tory Engins before described, and if I had had them, yet I would not have singly rested upon them, without ma­king trial by rarifaction by heat, I took the method hereafter following, for the full examination of this Instance.

For it is obvious beyond dispute, that that if there be a cohesion wrought af­ter rarifaction of the Air by heat, in the Instances hereafter given, as there is when there is a tension of the Air by a forcible Evacuation, as in the former Instance; the true cause of each cohe­sion must be one and the same. And if the pondus externi aeris contribute no­thing to the cohesion of the Hemi­spheres after rarifaction of the included [Page 270]Air by heat, it contributes as little to the cohesion of the Hemispheres forci­bly evacuated by an Air-pump, or the Cacabus Evacuatorius before mentioned.

And on the other side, if the cohesion of the Hemispheres after rarifaction by heat be caused by the motus restitutionis of the included rarified Air, and by the strict continuity (as I may call it) of the filaments of the Air to the cavity of the Hemispheres, to avoid that Vacuity which would otherwise happen by the contraction of the Air into a less room than would fill the whole cavity; the same is unquestionably the reason of the cohesion of the Hemispheres forcibly evacuated as above.

The Instances therefore that I tryed are these that follow, which I shall men­tion severally, with my observation to each of them. For if I mistake not, this one Experiment, duly improved, whol­ly sets aside the imaginary Gravita­tion of the Air, so usually applied to the Solution of the Torricellian Ex­periment, the cohesion of Marbles, the raising of Water in Pumps, and [Page 271]by Suction, and many more of like na­ture.

First, I caused two Brass concave He­mispheres to be cast, each of six Inches and a quarter in the cavity, and about seven Inches diameter in the convexity, exactly closing one to another on their rim, and the lower let up into the cavity of the upper about half an Inch, for their more exact closure; and the outward rims of each about a quarter of an Inch in bredth, exactly closing one upon another, so that being closed they made one perfect Sphere, according to the form of the Magdeburgh Hemispheres above described.

The lower Hemisphere weighed six pounds, seven Ounces, and a half, viz. 103 Ounces, and half; the upper weigh­ed only six pounds.

I then took a circular piece of Calf­skin, a little above half an Inch broad, and in length sufficient to compass the Hemispheres, and dipping it in melted Bees-Wax, with a very little Rosin, so that it might just lye between the com­missures of the two Hemispheres, and [Page 272]stop out all access of the forreign Air be­tween them.

First therefore, without any thing more done, I applied the two Hemi­spheres each to other, with the interpo­sed girdle of waxed wet Leather, and pressed them close and hard together, that no commerce might be between the included and the common Air.

And so there neither was nor could be any force of compression used to the included Air, because 'till the closure of the. Hemispheres it had a free inter­course with the external Air, and when perfectly closed it was but just as much as the Hemispheres would freely con­tain, and consequently of the same tex­ture with the forreign Air.

In this Instance, the upper Hemi­sphere raised gently by the ring, there seemed a little weak cohesion be­tween them, because the rims were per­fectly closed, and the separation was altogether in the same moment, but the cohesion so faint and weak, that it would not sustain the hundredth part of the weight of the lower Hemisphere, and scarce perceptible.

And the reason of the disparity be­tween the cohesion of these Hemi­spheres, and that before mentioned of the 2 polished Marbles, are these. 1. Be­cause the contiguity of the two po­lished Marbles is in all points of their Superficies, but here the contiguity of the rims of the Hemispheres was but in a circle of a quarter of an Inch broad, and so the forreign Air had a shorter journey to go in the moment of the se­paration of the Hemispheres, than in the moment of the separation of the poli­shed Marbles. 2. Because the contigu­ity of the polished Marbles is without any interposition of Leather, which possibly would impede the firmness of the cohesion of the two Marbles them­selves.

But now if the pressure of the aereal Cylinders either in the polished Mar­bles, or in the instances of the Hemi­spheres, before and hereafter given, were the cause of their cohesion, what imaginable reason can be given why these two Hemispheres should not co­here as firmly in this Instance.

For though there be Air included be­tween the two Hemispheres, yet all communication between the included and forreign Air is perfectly excluded by walls of Brass, and the impervious Leather girdle.

If it be said, that the Elasticity of the included Air resists the compression by the forreign Air, and so impedes the cohesion.

I say if any such Elasticity were ad­mitted in the Air, (which I do not) yet most certainly the included Air hath no greater Elasticity than the common Air, whereof it was but just now a por­tion, and hath received no more com­pression by the juncture of the Hemi­spheres, no more than Air in a Bottle covered with a flat Board or Paper.

The consequence whereof is, that the Elasticity of the forreign Air is as strong as the Elasticity of the included Air, and must needs keep it in aequilibrio. And the consequence thereof is, that if the pon­dus externi aeris (if it were any way con­siderable) would have its free exercise upon these Hemispheres, though filled [Page 275]with Air; for according to these Ma­sters supposition, the Cylinder of Air of each side pressing each Hemisphere, is above seven hundred pound weight, which it may freely exercise, the imagi­nary Elasticity of the included and for­reign Air being ex suppositione equal. But the ensuing Experiments will ren­der this more evident.

Secondly therefore, I took a handful of flax, and leaving the mouth of the lower Hemisphere upward, I put in the flax, and gave fire to it, holding the up­per Hemisphere close over it, whereby the Air in both was greatly rarified, and a considerable portion of the space taken up by the flame of the flax. Then clapping the upper Hemisphere upon the lower, with the interposed Leather girdle, I pressed them together with all the strength I had, neither were they possibly capable of a neerer or closer contiguity to the interposed Leather, though the imaginary Cylinder of the Atmosphere had pressed them, and hereupon the flame and fire was pre­sently extinguished.

The Events were as followeth.

1. There grew a present cohesion of the two Hemispheres together, even while they were hot, and the included Air under a high degree of rarifaction by the heat, and so could not have any considerable tension while the heat con­tinued.

And the reason of this cohesion was plainly this. That the fire and flame had not only rarified the Air included within the compass of the Hemispheres, to an expansion far greater than was na­tural to it; but also the flame and fire took up a considerable portion of the space between the Hemispheres, which being extinct in the moment of their juncture, that very rarified Air that was within, was forced to take up so much more space as the flame took up before its extinction. And from thence grew necessarily an attraction upon the cavity of the Hemispheres, though that very Air was under a rarifaction by the con­tinuing heat.

2. But this cohesion was but weak, because the Air was then under a [Page 277]strong dilatation by the continuing heat, and therefore the upper Hemi­sphere lifted up by the ring, would not sustain the weight of the lower Hemi­sphere.

3. But when the Hemispheres thus hea­ted, and the included Air greatly rari­fied thereby, were permitted to conti­nue together closed 'till they were per­fectly cold, and thereby the Air had op­portunity to contract it self, or at lest to endeavour it as much as it could. Now the cohesion of the Hemispheres grew strong, so that the upper lifted up would raise the lower in conjunction with it, with the addition of some weight appended to the lower ring. And the reason was, because the heat which was the cause of the great dilata­tion of the included Air was now cea­sed, and the Air by its motion of re­stitution endeavoured to contract it self to its natural Expansion.

And because the included Air (it may be) was expanded to above four times its true natural size and dimension, and now endeavoured to contract it self [Page 278]into that space, but could not attain it, unless three fourths of the space inclu­ded within the Hemispheres should have been left perfectly empty, the Air en­deavouring its contraction, according to the particular inclination of its own motion; yet by the common law of the Universe was kept under its former Expansion, to prevent the casma be­tween the Air and the concave Super­ficies of the Hemispheres, and so as much as was possible attracted upon them, and kept them together, no for­reign Air being admissible for the relief of the included Air, to help to restore it to its due size and texture: as a living Oyster contracts its shell together by its own contraction within its shell, when a person is opening in. The compari­son is homely, and suits not in all things, because the Oyster is a vital Being, but yet it serves to explicate the method of this attraction, by the filaments of the Air upon the contiguous concave Superficies.

And from this instance of fired flax (resembling very much the common [Page 279]instance of Cupping-glasses,) it ap­pears plainly, that in those Glasses the flesh is not driven up by pressure of the forreign Air upon the glass or the con­tiguous parts of the flesh; but purely by the attraction of the included residue of Air upon the extinction of the flame. For the Hemispheres were at first pres­sed together as close as they could be, and no man can imagine that the exter­nal Air can have any influence through these Brazen Walls, that are neer half an Inch thick, where yet the Attraction upon the included Superficies is visible and apparent; and in this and my other Experiments it was not possible for the Hemispheres to receive a greater or clo­ser contiguity than I gave them on their first union: and therefore I do not wonder, that Schottus, though too hasti­ly subscribing to the pressure of the Air, as a Solution of some Experiments, yet in his Technica Curiosa, l. 4. cap. 12. § I. is forced to confess ‘ carnem & sanguinem sub­intrare cucurbitas, nec pressione Aeris ex­terni carni circum illas incumbenti, nec pressione aeris illas incumbentis & depri­mentis, [Page 280]ac intra carnem mergentis, sed suctione & attractione.’

3. Because I would improve the Ex­periment to the uttermost, I made a try­al with a stronger heat. I therefore put burning Coals and red hot Iron into each Hemisphere, 'till they were hot as I could well touch them, and then ca­sting out the Coals, the Air within the cavity of each Hemisphere was highly rarified; then clapping the Leather gir­dle about the rim I closed the Hemi­spheres very close, as my strength could force them together; the Events where­of were these:

1. While the Hemispheres were hot, and so the included Air under a high degree of rarifaction, there was very little or no cohesion, for the Air was under the same laxation as at first, and therefore they would presently fall asunder, the upper being raised by the ring.

2. As the heat decayed, and the He­spheres grew gradually colder and col­der, and consequently the Air more and more endeavours to contract it self, and [Page 281]as a consequence thereof attracted more forcibly upon the cavity of the Hemi­spheres, the stronger was there cohe­sion; because as the Air grew colder, it endeavoured more and more to ac­quire its just natural dimension and tex­ture.

3. At last, when the heat was quite extinct, and the Hemispheres grown perfectly cold, the cohesion was so strong, that the upper Hemisphere sus­pended upon a hook, did not only su­stain the lower Hemisphere, which weighed neer seven pounds, but also a weight of twenty eight pounds more, in all about thirty five pound weight, before they would be disjoyned.

For now the Air being discharged of that heat that kept it laxe, and without a bent, or tension, or contraction in­ward, did now endeavour its contra­ction strongly, and therewith pulled inward the Hemispheres, from which it could not be severed, by reason of common Natures declination of a Va­cuity.

4. My fourth Tryal was this, that [Page 282]when the Hemispheres were first hea­ted, and clapt together, and thereby when they became cold, cohered excee­ding strongly; yet when they were un­der that strong cohesion, that they would sustain a considerable weight as before, without parting asunder, yet if afterwards they were brought but to a moderate heat, either by a chafing-dish of Coals put under them, or by holding them neer the fire, they would suddenly fall asunder of themselves, without any weight appended to sever them.

The reason whereof is apparent, namely that by the heating of the He­mispheres the included Air is again ex­panded, and its tension laxed, and the filaments thereof which were before under a tension and contraction by the Air, striving to gain its natural tempe­rament, are now let loose, as a Lute­string is let down by the unscrewing of the Pins. And consequently the suction and attraction of the Air upon the con­cave Superficies of the Hemispheres, which before held them together, is re­laxed and discharged.

And thus we have the true phaenome­na of this Engin, and, as I take it the true reason and solution of them.

And upon these Instances I do con­clude,

1. That men have had very little reason to conclude the Gravitation or Pressure of the Air upon the inferior World, or the parts thereof; for the co­hesion of these Engins is most plainly upon another reason, as appears by what is before declared.

2. That this instance is so far from concluding the Gravitation of the Air in that measure, that the late Masters contend, that plainly that Supposition neither hath nor can have to do in the solution of these Instances.

For most unquestionably, the Air doth as much gravitate (if at all) upon the Hemispheres, when the included Air is rarified by heat, in these Instan­ces, as it doth when the Hemispheres are grown cold; and yet in the former case there is no cohesion, but contrari­wise a separation of the cohering He­mispheres if again they are heated.

3. That the cause of the cohesion therefore is not ab extra, or de foris, but ab intra; namely, one specifical to the Air, whereby becoming cold after a great expansion by heat, it endeavours its contraction to its due space and tex­ture, by a motion of restitution; the o­ther common to all parts of the Uni­verse, that common law of Nature that preserves contiguity, or indeed rather continuity of the parts of the Universe: and therefore suffers not the Air to con­tract it self, so as to leave an empty space between it self and the concave of the Hemispheres, whereby it comes to pass, that the Air endeavouring to contract it self, layes hold upon, and endeavours to contract and hold together all parts whereunto it is contiguous, when no access of forreign Air is admitted.

4. That the least admission of for­reign Air, though through a Pin-hole, in the Hemispheres, gradually gives a relaxation of the tension of the included Air, which greedily sucks it in, and thereby is delivered gradually from its tension, and lets go its hold of the conti­guous [Page 285]Superficies, which is the natural and necessary effect of that tension.

I cannot easily perceive how these Conclusions against the imaginary Gra­vitation of the Air can be evaded.

If it should be said, that the reason why the Hemispheres cohere not when they are hot, is, because the convexity likewise of the Hemispheres are also hot, and so retund the Gravitation or Pres­sure of the Air upon them by their heat, which is not so done when they are cold.

I answer 1. That though the con­vex Superficies were admitted to be as hot as could be indured, yet the Sphere of that Activity is not two foot in cir­cumference, which could never break the pressure of a column of Air of at least seven Miles high, and near a thousand pound weight, according to the Sup­position. 2. Neither is the heat requi­red to make such a disjunction of that Extremity, as to make any such impres­sion upon the Air; for if the Hemi­spheres be made but bloud warm after their cohesion, they will fall asunder.

3. But wholly to prevent this imagina­tion, if the Hemispheres be cased over with a flat or spherical Cover of Wood, Lead, or Brass, which may receive the supposed Gravitation of the Air, yet the cohesion, while the air is hot within, will not last; for it is the laxation or rela­xation of the tension of the Air within that, gives the separation, or easie sepa­rability of the Hemispheres.

CHAP. XIX.
Concerning the raising of the Water by Pumps or Syringes, and the Cause thereof.

IN the two former Chapters I have considered the cohesion of polished Marbles, and the Magdeburgh Hemi­spheres, both in truth resting upon So­lutions somewhat of the same nature. And therein I have as I think excluded the Gravitation of the Air, or Atmo­sphere, or aereal Cylinders, from any contribution thereunto.

I have chosen in this Chapter to con­sider [Page 287]the Elevation of Water in Pumps and Syringes, both which are in truth but the same Engin, though circum­stantially varied.

And although I shall herein have oc­casion to say something touching the Gravitation of the Air, and shall in some measure evidence, that the Water is not raised in these Engins by the weight of the Air, pressing upon the restagnant Well or other vessel of Water, yet I shall not labour that, much, in this dis­quisition, because enough hath been said thereof before.

But my principal scope herein is to discover, even to sense, that there is no such Elasticity in a separate portion of common Air as the Elaterists suppose, whereby to salve the suspension of a co­column of twenty nine Inches of Mer­cury in the Torricellian Experiment, when the same is pent up in a close ves­sel or room, every where excluding the imaginary pressure of the Atmospheri­cal Cylinder; and consequently that the Solution of that Experiment, either by the Weight or by the Spring of the [Page 288]Air, is a mistaken Solution, and hath no reality in it.

The raising of Water by common Pumps or Syringes (especially as it is this day ordered, sometimes with dou­ble, sometimes with single Valves, to hinder the regress of the Water) is so well known even to ordinary Plum­mers, that it needs no accurate descrip­tion.

But the reason of this Elevation of the Water is variously rendred, accor­ding to the different hypotheses that men have entertained.

The ancient and common, and I think the true reason thereof, is this:

The lower end of the cavity of the Pump or Syringe being immersed below the Superficies of the restagnant Water, there is a Cylinder of Air in the cavity of the Pump or Syringe, between the Superficies of the Water and the bottom of the Bucket and upper Valve of the Pump, or between the Superficies of the Water, and the bottom of the Em­bolus of the Syringe closely penned up.

That by the Elevation of the Bucket [Page 289]in the Pump, or Embolus in the Syringe, that portion of intermediate Air is un­der a tension, and draws vigorously upon the Superficies of the restagnant Water, and that again upon the conti­guous Water, and so the tensed funicu­lus of the Air raiseth a funiculus of Wa­ter, commensurate to the cavity of the Pump or Cylinder, which again by depression of the Bucket riseth through the Leather-valve that covers it, and by an iterated elevation of the Bucket or Embolus draws up more, whereby there is a continued supply of a funiculus aque­us, which is finally thrown out at the orifice, or nose of the Pump.

That it is a certain truth, that Water is raised either by a pondus or pressure, that is equivalent to the weight of the Water that is elevated, as in the Engins where Forcers or pressures are used to raise Water; or else by an attractive potentia equal to the weight of the Wa­ter drawn up, as in Pumps and Syrin­ges.

That consequently, the vis or potentia suctoria or attractiva, will raise such a [Page 290]weight of Water as is less than this vis or potentia, (for whether the Elevation of Water be by a vis deprimens as in pressing Engins, or vis suctoria or attra­ctiva as in Pumps or Syringes, or the preponderation of the potentia to the weight of the Water) thus it sustains, imples, or attracts, and therefore they are all reducible to the reason of the libra or Ballance.

And on the other side, if the weight of the Water exceed the pondus or poten­tia which must raise it, it cannot either draw, or impell, or keep it up beyond an aequilibrium with that pondus or potentia impellens or attrahens.

And therefore if there be an exces­sive distance between the Superficies of the restagnant Water, and the bottom of the Embolus or Bucket, suppose it 50 or 60 foot of perpendicular height, whereby the potentia attractiva is over­matched with a pondus of Water more than its strength, it will not raise it to a due height. For still as I said, where any weighty body is raised out of its place, it must be by a greater weight, or [Page 291]at lest by a potentia, exceeding that weight of the Body to be raised.

But the modern Philosophy tells us, that the raising of the Water in the Pump or Syringe, is not by a vis attra­ctiva or suctoria of the Bucket or Embolus, but that it is forced up by the weight of a Cylinder of Air, commensurate to the cavity of the Pump or Syringe.

And that the Elevation of the Pump or Embolus of the Syringe, attenuating the Air inclosed in the cavity of the Pump or Syringe, and thereby disabled by its laxity to resist the pressure of the external Cylinder of atmospherical Air, the Water is driven up into the cavity of the Pump or Syringe.

And because a Cylinder of Mercury of twenty nine Inches and half, is by them supposed to be of equal weight to the Cylinder of Air of like diameter, reaching from the top of the Atmo­sphere unto the vessel of restagnant Mercury in the Torricellian Experiment, and a Cylinder of Mercury of twenty nine Inches and half high, countervails in weight a Cylinder of Water of like [Page 292]diameter of about thirty three foot high, and consequently a Cylinder of the At­mosphere counterpoiseth a Cylinder of Water of about thirty three foot high, therefore the Water in a Pump will be raised but just to that height, viz. neer thirty three foot, and no higher, because such a column or Cylinder of Water is counterpoised by an Atmospherical Cylinder of like diameter. Thus I think it is rendred by Schottus in his Technica Curiosa, l.4.cap.8.§.4. and by the Excellent Author of Hydrostatical Para­doxes, n.5. and by other learned men of this latter age.

But under their favour I think this is not the true Solution of the instance in hand, but the first is the true Solution thereof.

If the elevation of the Water in the Pump may be more considerably higher than 33 foot, certainly this latter Solution cannot serve. And though this possibly hath not been fully tryed, and requires exact Engins to effect the Tryal to the uttermost; yet there are many that do experimentally affirm, [Page 293]that a Pump or Syringe well ordered will raise Water above forty foot perpendi­cular height; and if so, the counterpoise of the aereal Cylinder will not do the business. But this I have not tryed, I will therefore apply my self to what I have tryed.

Fig. 22. I took therefore a great and strong globular glass Bottle, ABC, holding five Quarts of Water, of about nine Inches Diameter, with a double orifice, viz. one at A, wherein to fa­sten my Pump hereafter described, ano­ther at B, to let in or pour out Water, to leave open or close, as I saw cause.

In A the neck of the Bottle I fastned a Laton Pump or Syringe, or about an Inch and a half diameter, marked D, with a small Pipe about half an Inch di­ameter; reaching neer the bottom of the Glass, viz. E; an Embolus at G reach­ing down neer H, and a little crooked Pipe at H to drive out the Water by the depression of the Embolus.

This Pump was fastned and strongly luted in the neck of the Glass with a double Valve, one about A to receive the [Page 294]Water into the Pump, and to sustain it from returning, by depressing the Embolus, another at K the top of the orifice, to keep the Air from entring upon raising the Embolus.

So that now the Bottle was the Well, which I filled up with Water.

Therefore leaving open the orifice at B, whereby the Air had free access into the Bottle, by lifting up and depressing the Embolus G the Water was freely and easily without any difficulty drawn out at the orifice K, through the Valve there placed, and so I emptied half the Bottle of Water, namely to I the supe­rior half, being full of free uncompres­sed and common Air; and the lower half at I being full of Water.

The Pump being in this posture, I took a short piece of Cork, first boyled and then dipt in melted Bees-wax and Rosin with it, I closely luted up the ori­fice at B, so that no air could possibly en­ter. And then I lifted up and depressed the Embolus several times, so long 'till I could see the whole success of this Tryal.

First, the Embolus was raised, but not [Page 295]with equal facility, as it was done when the orifice B was open.

The reason whereof is, because every elevation of the Embolus gave a violent tension to the Air in the superior cavity of the Glass, which upon every portion of Water drawn up must necessarily be expanded into a larger space to supply the space left by the raised Water. So that the expansion of the Air was not natural, or of its own accord, but by a violent attraction wrought upon it, and tension of it.

Secondly, yet notwithstanding the exclusion of the Air, I did freely pump out above a quart of Water, whereby the Water subsided an Inch and a half below I, and consequently the Air ex­panded and dilated to so much more space than it had before, viz. whereas the superior cavity of the Glass held by the Air was two quarts and half, now it took up the room of three quarts and half, and somewhat more.

So that here was a quart of Water raised up by the suction of the Embolus, and yet no possible Gravitation of that [Page 296]imaginary atmospherical column to press or drive it up; so that surely the ascent of the Water in the Pump is not by the Ballance, aequipondium, or pre­ponderation of a column of the Atmo­sphere to the column of Water raised in the cavity of the Pump, for here was no access for any such column: whe­ther the imaginary Elasticity of the in­cluded portion of Air may be called in to help the matter, we shall see here­after.

Thirdly, but when I had raised up this quart of Water, and emptied so much out of my Bottle, all my iterated tractions and trusions of my Embolus could raise not one drop more.

But all that was done by these repea­red motions, was only the rarifying of the Air included in the Pump, when the Embolus was lifted up, and conden­sing it again as the Embolus was depres­sed, but no Water raised.

Now in this instance, the reason why a quart of water was raised, though the orifice at B were stopped, was be­cause the potentia suctoria or attractiva [Page 297]of the Pump was strong enough to give a dilatation of the Air to a greater space by a quart than it had before.

And the reason why it could raise no more, is this, namely, in as much as every portion of Water raised out of the vessel, must of necessity leave a space devoid of so much Water as is so raised up, and that derelicted space must ei­ther be wholly vacant of any Body, which by the universal law of the Uni­verse is prohibited, or else the Air must expand it self to fill it. And in as much as the Air having undergone as great an Expansion already (by the evacuati­on of the first quart of Water) as this potentia or vis attractiva was able to effect. The included Air thus expanded resisteth any further expansion with an equal strength to the attractive power of the Pump, and so renders it conamen irritum, to give it a larger expansion, and consequently no more Water is raised.

But if a greater strength were applied, strong enough to master that resistence, as if the Pump were longer, that it [Page 298]might give a stronger suction, that might overmatch the resistence of the included Air against a higher degree of tension; yea or if the superior Air, af­ter this quart of Water was evacuated, had a strong external heat applied to it, whereby it might be capable of a larger expansion, the Water (while the Air was under this forcible expansion) would be as easily raised by the Pump as at first. But this I durst not try, for fear of breaking my Glass, or unluting of it.

Upon this consideration and tryal it is manifest,

First, that the Gravitation or pressure of the external Air is not the cause of raising the Water in the Pump; for here it is raised where there is no Gravi­tation, the orifice at B being perfectly stopt.

Secondly, that the common Air hath no such Elasticity, as the modern Phi­losophy assigns to it; for here a portion of Air included in the Glass is of the same texture with the common Air, and a portion of it, and yet evidently there [Page 299]is no such Elasticity in it as is supposed.

And this appears, 1. because it is not expanded to one third part of greater space than it had before, without a force offered to it, as above is shewn. 2. When it is expanded to a third part of space more than it had, it is so far from a na­tural expansion of it self farther, that it refists the attractiva potentia of the Pump to give any larger expansion. And 3. if it had yet a natural expansive power without force or violence added to it, it would certainly drive up the rest of the Water that remains, especially when the Air in the Pump is rarified or extended by the elevation of the Embo­lus, and yet no Water follows it, in this instance, which yet it would do, if the Air had a continuing Spring or Elasti­city to drive it up.

It is true, that naturally all the spaces of this lower World (at lest) are and must be filled with some body or other: and as one body moves or is moved out of one space to another, some other body succeeds in that space that is so left, and fills it. And the fluid Bodies of Air and [Page 300]Water, or some fluid bodily substance, equivalent to either of them, are in re­spect of their fluidity fitted more than other solider Bodies, to supply and make good the interstitia of other Bodies; and if they be contiguous unto them, to slip into the spaces deserted by their motion into other spaces, and accordingly will do it, if they are not impeded by the re­sistance or interposition of other more stubborn and untractable Bodies. And by this means upon the successive mo­tions of Bodies, there is maintained a successive and continual circulation in the motions, especially of those Bodies that are fluid, and so more ready and apt for motion.

In the Instance of my Pump, suppose that the orifice at B be left open, and the vessel or Bottle have a Gallon of Water in it, and there stands by it an empty vessel, suppose M, that contains a Gal­lon of Air: if I pump out a Gallon of Water out of the Pump into the vessel M, as the Pump is gradually emptied of the Gallon of Water into M, the Water leaves its place in the Pump, and takes [Page 301]up as much room in M, and the Air in M leaves as much space there, and takes it up in the Pump, to which it hath a free access; so that the two Ele­ments change their stations, and while they hold their natural texture, hold the same extension of space, though not the same situation. And thus a circulation is naturally consequential upon the mo­tion esepecially of fluid Bodies; and there­fore when the Water leaves its place in the Pump, and dispossesseth the Air in the vessel M, and the dispossessed Air gradually succeeds into the space left by the Water, as fast as the Water leaves it, and takes up another room equal to what it had before, though in another ubi; here is no Gravitation of an At­mospherical column upon the orifice B, but only a natural motion and successi­on of the like portion of Air into the place relicted by the Water, and a natu­ral desertion of that space which it be­fore had in the vessel M, which it can­not retain against the weightier and more prevalent Element of Water tak­ing it up. So that it is neither a Gravi­tation [Page 302]of the atmospherical Cylinder upon the orifice B, nor any great Ela­sticity of the Air that drives up the Wa­ter, but a natural circulation of the por­tion of Air into the space derelicted by the Water; and the immission or insi­nuation of the Air into that Cavity, is the Effect not the Cause of the recession of the Water.

And now to reduce all this long pro­cess to the thing I principally intended, we are told by the late Philosophy, that the suspension of the Mercury at twen­ty nine Inches height in the Torricellian Experiment, is caused by the counter­poise of the weight of an external atmo­spherical Column, commensurate in its crassitude and weight to the Mercurial Cylinder suspended in the Glass Tube.

And when it is replied, that the like suspension happens, if the Mercurial Engin be placed in a close room, yea or in a Glass every way closed, that admits not any such Mercurial column, but in­tercepts it and its pressure by its closure every way. We are again told, that that little portion of Air included with­in [Page 303]that room or Glass, hath so potent an Elasticity, that it will as effectually suspend the Mercury in the Tube, as that tall Atmospherical Cylinder of at least seven Miles long. This I say seems to me utterly incredible for these rea­sons:

1. The Air included in a close room or Glass, hath only the advantage of its imagined Elasticity, but not the advan­tage of the stupendous weight assigned by this New Philosophy to the external aereal Cylinder.

The external Air hath the same Ela­sticity attributed to it, as the Air inclu­ded in the close room or Glass, and also the supposed advantage of the weight of the Cylinder of the Atmosphere besides.

If the bare Elasticity of inclosed Air be sufficient to suspend the Mercury at twenty nine Inches and half, within the room or Glass; the same Elasticity in the external Air, with the advantage of its weight, should suspend the Mer­cury to fifty nine Inches high, which was never yet done.

2. If the Elatery of the Air cannot [Page 304]drive up a successive portion of Water of half an Inch diameter into my Pump, without the attraction of the Embolus; nor yet is that attraction also effectual to raise the Water, when it hath expanded the Air to about a fourth part of space more than is natural to it. It is impossi­ble that the Elasticity of the Air, inclu­ded in a close room or Glass Receiver, can drive and keep up a Cylinder of Mercury twenty nine Inches high, which yet according to the amplitude of its diameter may weigh, two, four, or ten pound.

I do therefore conclude upon the whole matter, that it seems to me, the new hypothesis of the Weight and Elasti­city of the Air, as it is delivered by the late Philosophy, is an Ingenuous Inven­tion, but wants Reality to support it self, or to give a right and true Solution to the Phanomena wherereunto it is applyed.