ESSAY TOUCHING THE Gravitation, or Non-gravitation OF FLUID BODIES, And The Reasons thereof.

LONDON, Printed by W. Godbid, for William Shrewsbury, at the sign of the Bible in Duck-lane. 1673.

THE CONTENTS.

  • CHAP. I. THe Introduction. Pag. 1
  • CHAP. II. Of Gravity and Gravitation, and the true Reason of the latter. Pag. 9
  • CHAP. III. Concerning the Gravitation of Solid Bodies, and there parts. Pag. 13
  • [Page]CHAP. IV. Concerning the Gravitation of Solid Bodies in Contiguity, and not in Continuity. Pag. 19
  • CHAP. V. Concerning the Gravitation of Fluids upon subjected Bo­dies; and first, of the Gra­vitation of Water. Pag. 30
  • CHAP. VI. Concerning the Reasons assigned, by others for the Non-Gra­vitation of Fluid Water upon Subjected Bodies Pag. 37
  • [Page]CHAP. VII. Concerning the most probable Solution of the Phaenome­non of the Non-Gravita­tion of Water in its Fluid Consistence. Pag. 48
  • CHAP. VIII. The second and principal Rea­son of the Non-Gravitation of Water upon it self, or a Subjected Animal, or other Body. Pag. 58
  • CHAP. IX. Certain Consequences or Con­sectaries, drawn from [Page]what hath been before said. Pag. 78
  • CHAP. X. Concerning the Gravitation of the Aire. Pag. 83

Concerning Gravitation of Fluids upon Subjected Bodies.

CHAP. I. The Introduction.

I Have considered the noble Problem tou­ching the Gravitati­on or Non-gravita­tion of Fluids upon the Bodies subjected to them: And of those several So­lutions and Suppositions touching the same, given by the great Wits of latter Ages, which I shall in their due place, more particularly examine.

And I must needs commend the Industrie of this latter Age, in the inventing and exhibiting of very choice Experiments, as in re­lation to some other Philosophical Essays, so in particular, touching this Phenomenon of the Gravi­tation or Non-gravitation of Flu­ids.

But yet I must further add, that though their Experiments herein have been searched out, and formed with great Ingenuity, Industry, Curiosity and Expence; yet their Solutions of them, and the Suppo­sitions and Reasons whereunto they have reduced them, have been (in my understanding) very unsa­tisfactory and inevident, if not wholly untrue and inexplicable,

And the reasons hereof seem to be principally these, viz. 1. That men have pre-ingaged themselves and their judgments in the asserti­on [Page 3]and maintainance of certain preconceived Hypotheses and Prin­ciples which they have invented, and are therefore extreamly ad­dicted to, and unwilling to hear or receive any thing that may ren­der their Labour herein vain and fruitless. And upon that account, have, not without much partiality, misapplyed and misappropriated their Experiments and the Solu­tions of them, in favour of such Hypotheses as they have once in­vented or entertained, and with too much prejudice, reject any o­ther Solutions, that may either o­verthrow, or at least not gratify such preconceived suppositions. 2. That men have not strictly enough considered of the Nature of Gravitations, and the Reason thereof. 3. That they have not enough taken into consideration those several accidental (as I may [Page 4]call them) Interventions that abate, impede, advance, or direct the Gra­vitation of Bodies, though in themselves heavy, and tending to the Centre.

I do not intend to make a full Tract concerning Gravity or Gra­vitation; those that mind to trou­ble themselves therein, may at their leisure consult those Excel­lent Men that have written at large of this subject, as Archimedes de insidentibus humido. Mersenius, and Stevinus their Hydrostaticks; and although I cannot subscribe to all that the two latter have written in this subject, yet I must needs say, that I think little of moment hath been added to their Principles and Demonstrations by later Writers, only some new Experiments have been added by later Writers, bot­tom'd upon the Doctrin and Ex­periments of these Ancients.

I shall therefore direct all I have to say principally to this one mat­ter or point, namely, the Gravita­tion or non-Gravitation of Fluids upon subjected Bodies, and the de­grees and reasons of this Phaeno­menon.

And though it may possibly happen, that what I say herein may as little satissie others, as their suppositions have satisfied me. And though my Explications of my thoughts herein, and the applica­tion of my Experiments thereunto may not be so clear and well wor­ded as others of this Subject have been, yet I have this Apology for these defects; 1. That what I now write, though it hath been long upon my thoughts, was written raptim and hastily. 2. That I do not know that the Path I walk herein was ever before troden by any else. 3. It is but an Essay, and [Page 6]took not up many hours in wri­ting, and will take up much less in reading thereof.

And this I premise, not to arro­gate singularity to my self, or to please my self in being the first in­ventor of this Explication; for possibly it may fall out, that it may bescarce worth the owning, when well examined by better Judg­ments, and possibly I my self may retract some things in it, upon bet­ter reason discovered: Yea, and possibly it may fall out, that some others have had a more early conception of it than my self, and may have dressed it in better order; and indeed it would be some confir­mation to me, if it were so, though I have not yet known or heard of any such Anticipation.

I have seen many men very confident in the suppositions which they have found out; and yet up­on [Page 7]on full examination, their mistakes have been discovered: And al­though I think that I have laid down true suppositions, yet I will not be over-confident of them; for I may be over partial to my self, as I find others are to them­selves and their suppositions; and it is not the confidence of the Au­thor, but the Evidence of Reason, that prevails with sober men; and therefore I do propound them but as Essays, and submit them to fur­ther examination.

And the reason why I offer it to the publick view is, that better Judgments than my own may con­sider it; and though possibly they may not in all things approve it, or the manner of its Explication, yet they may by this opportunity, either improve it if they allow it, or make some useful superstructi­ons upon it, for the farther disco­very [Page 8]very of this noble Problem; as Arithmeticians do by the Rule of False Position, make true Con­clusions, or at least may desert the vanity of this or any other opini­ons formerly offered touching the Solution of this quaesitum, and offer better.

Chap. II.

Of Gravity and Gravitation, and the true Reason of the latter.

GRavity if self seems to be an Intrinsecal quality of Bodies, whereby they tend down wards to, or to wards the Centre of the Earth.

I am not here to trouble my self with these Philosophical Questi­ons, whether there be any other Centre of Gravity than the Cen­tre of the Earth for weighty Bo­dies? Nor what is the prime cause of descent of heavy Bodies, whe­ther any Magnetical quality in the Earth, or any forcible ex­trinsecal Impression by the Motion of the Heavens, or heavenly Bodies, or that Circumpulsion of other Bodies, that some have ima­gined, [Page 10]or any Intrinsick form of the heavy Bodies themselves, which is analogical to a vital prin­ciple, exerts this power. But it serves my turn at this time to call it an Intrinsick Quality of heavy Bodies. Gravitation is either Mo­tion it self, or the conatus or nisus admotum; and therefore it is (that according to that linea directionis, whereby, or according to which the Motion of Bodies are directed) not improper to say, that accor­ding to that Line of Direction, these Bodies do gravitare; and al­though ordinarily the Line of Di­rections of heavy Bodies, naturally is towards the Centre of the Earth in a perpendicular descent, which is the ordinary motion of Gravitation, and is greater or lesser according to the strength, weak­ness, or allay of this nisus or conatus: Yet it is not altogether incongru­ous [Page 11]to say, that every thing that hath a nisus or conatus ad motum, doth in some sort Gravitate accor­ding to the Degree and Line of such Direction; and thus Fluids, though the primitive Line of the Direction of their Gravitation, may be perpendicular, yet Flu­ids have for the most part a na­tural Direction or Gravitation o­therways, and some Fluids may have an Accidental Gravitation o­therways. For instance, Water, though it have its primitive Line of Direction of its motion down­ward to the Centre, yet it hath Lines of Direction of its Motion otherways, as Laterally, or per de­clive, and in some instances per ascensum, (whereof hereafter,) and consequently Gravitates every of those ways. For, as I said before, Gravitation is nothing else but Motion, or at least conatus or nisus ad motum.

And therefore it is no real in­congruity to say, that Fire or Gun­powder doth Gravitate in its Lines of Ascension or Expansion; that the Bullet, when shot upright, doth Gravitate ascendendo, when it is shot level it Gravitates horizon­tally, as long as that force prevails against its natural motion of De­scent. For as to this purpose, Gra­vitation is nothing else but motus, or nisus ad motum secundum in line am Directionis ejusdem.

And therefore it is, that when a weight of 10 or 20l. is in the Scale A, and nothing in the Scale B, a Percussion with a Hand or Ham­mer in the Scale B, that moves the Scale A with its weight from the Horizontal Plane, wherein it stands, is truly said praegravitare to the Weight and Scale at A.

[figure]

CHAP. III

Concerning the Gravitation of Solid Bodies, and their parts.

IT is most certain, that every So­lid Body, separate from the Earth, hath an actual Pressure or Gravitation, or conatus ad motum towards the Centre of the Earth, as its proper Line of Direction; (I speak not here of the Centre of Gravity of the Bodies themselves, de quo vide sis Galdinum Gondicburl­dum, & Stephinum.) Yea, if a Body be a Fluid Body, yet if it be severed from a Body of its own nature by a Vessel containing it, this Fluid Bo­dy in this consistency, obtains the natural rule and reason of a Solid Body, consisting of the Water and the Vessel containing it. As, for [Page 14]instance, Water in a Pail or Bucket, as so stated, hath in it the nature of a Solid Body, and the Gra­vitation thereof is perpendicular to the Centre, which is its proper Line of Direction. And so Air in­cluded in a Bladder, though it swims in Water, yet doth Gravitate in some measure as other Solid Bo­dies do, and descends naturally to this Centre: yea a portion of Wa­ter by it self, being poured out of a Vessel from the top of a Tower or Steeple, hath its Line of Direction through the Air to the Centre, and will follow and Gravitate in that Line of perpendicular Descent. For though it be a Fluid Body in it self, yet relatively to the Air, being a lighter Body, through which it moves, it is in the nature of a Solid Body; and yet in a great Descent the Acceleration of its motion, and the renitence of the Air will break [Page 15]it into Drops or Dew, before it comes to the bottom in a great De­scent.

But though Solid Bodies do actu­ally Gravitate, yet if they be conti­nued, the parts thereof do not Gra­vitate one upon another, because mutually and mechanically sustei­ned one by another, and in a state of Continuity: as a Bowl of Ebo­ny that may weigh 10l, yet the upper Parts or Quarters thereof, whiles in Continuity, do not gra­vitate upon the lower; for if a hole were bored through the Bowl, yet the upper parts thereof would not gravitate upon the Cavity, for the reason before given.

And therefore the vast body of the Earth doth not gravitate upon its own Centre, because though all the parts thereof are perchance not simply continued as a Stone or piece of Wood; yet partly by their [Page 16]mutual Compression one to ano­ther, and partly by the Intervention of the cement of Water, they are quasi unum continuum.

Again, if we should suppose that the vast body of the Earth were di­vided into several solid inverted Cones or Pyramids, and that the Centre of the Earth were a lesser Globe of soft Wax or Quick-silver, or other soft Matter, suppose a Mile in Diameter; and that each Cone or Pyramid, having a part of the acute end cut off, to be contiguous to this Globe of Wax; yet it were impossible that they should press or gravitate upon that Globe of Wax, because they would be each sup­ported one by another, as will ap­pear by the following Figure.

[figure]

A the Globe of Wax in the mid­dle of the Earth, B the Earth, c c c the several divided inverted Cones. For the upper Base of every Cone being larger than the acute part thereof, every Cone will be sup­ported by his fellow without any gravitation upon the Clobe, as A.

Yea, and it would fall out to be in the same manner, though we should suppose that the Globe of the Earth, which some have supposed to be 7000 Miles Diameter, should be but 1000 Miles in Earth, and the other 6000 Miles to be a Globe of Water, or some fluid Body, [Page 18]for the reason before given.

And this by the way may shew the mistake of their supposition that think the impendent Column of the Atmosphere, which they think to be seven Miles high, is a bare Column commensurate in its top and bottom, for it cannot be so, but at the most is an inverted Cone or Pyramis, considerably wider at seven Miles distance then it is at the Earth: which if considered, would trouble their Explication of the Torricellian Experiment, upon an account of the actual Gravitation of a Column of Air.

CHAP. IV.

Concerning the Gravitation of Solid Bodies in Contiguity, and not in Continuity.

THE laws of Statiques do in­fallibly demonstrate, that the weight A incumbent upon the staff B, which at both extremities is supported by C and D, that C bears but one half of the weight A, and D the other half.

[figure]

And consequently if there were another Staff set on cross from E to F of the same length, each Suppor­ter [Page 20]would bear but a fourth part of the Weight.

[figure]

This being premised, I shall now consider the Gravitation of Solids not united and cemented together, either by Contunity of parts, or that which may be equivalent, Lime, Cement, or Morter, as in Brick-wals or Houses, but of such Solids as are united onely by Con­tiguity.

I will therefore suppose a Pyramis (or if you will a Pillar or Wall, for it will come all to one pass) having a foundation of twelve Stones, eve­ry way a Foot square, and piled up one upon another, breaking off joint according to Art of Masoncy, [Page 21]but without Cement or Morter; so that it will be twelve Foot square at the Base, according to this Fi­gure, 03 and consequently the Area at the Base be 144 square Feet.

[figure]

In this Figure these things are observable.

The upper Stone marked (1) is supported by the four next Stones upon which it is bottomed, and each of these four Stones bear but a fourth part of its weight; the next Row of Stones (being nine) bear each of them but a ninth part of the uppermost; and the four next, which is proportionably abated to the lowermost Rows. Now suppose, that the ground or basis whereupon it rests subjected under the middle of the Pyramis namely the square of sixteen square Stones, which make sixteen square Feet, were gently taken away; yet there would not thereupon sink a Co­lumn of sixteen square Feet exten­ding to the top of the Pyramis, for two plain Mechanical Reasons.

1. Because that Column is not merely supported by the base of six­teen [Page 23]square Feet, but by the residue of the whole Pile; and it would stand like an Arch over that Cavi­ty, which would happen upon the removal of these fourteen Stones, and those that are entirely suppor­ted by them.

2. Because the weight & the re­nitence of the rest of the Pile would keep up the Pyramis, if it had a suf­ficient weight by the residue of the Pile to bear one against another.

And so the residue of the Pyramis would stand without any Gravita­tion upon that Cavity, which would be left by the subsiding of those sixteen Stones, and those that are meerly supported on them, without any actual Gravitation upon that Cavity that is left, but onely upon the rest of the Base of the Pyramide; onely those Stones that were entirely supported by the sixteen subsiding Stones would [Page 24]sink with it, and leave a Cavity like an Arch, maintained by the rest of the Pyramis, according to this ensuing

[figure]

Figure, supposed to be the empty place of those sixteen subsiding stones, with those entirely supported by them, viz. nine, four, and one. And this Instance I have given of square Stones, to explain the reason of the thing: for it will hold in smaller and more irregular bodies.

Suppose there were a laying of a Floor of grains of Wheat, in a Floor of about 42 Foot circumfe­rence, and place an Egg, nay an Egg-shell, or Glass-bubble perfora­ted, that there may be the less pre­tence of resistance by its plenitude [Page 25]of Air; let this Egg-shell or Bubble be placed in the middle of this Floor, that it may not be injured meerly by the hardness of the floor, then gently cover it with more Wheat of about a Foot deep, then pour upon it 20 or 40 Bushels of Wheat; that the Egg-shell or Bub­ble may lie above ten Foot under the top of the Heap; yet this Egg­shell or Bubble shall not be broken: and yet take a Glass or wooden hol­low Cylinder, commensurate in base to the Egg-shell or Bubble, and four Foot long, stopped at the bot­tom, and lay it gently upon the Egg-shell or Bubble, it shall with its weight crush it to pieces.

And the reason is, 1. Because that every subjected grain of Wheat bears two, three, or four above it, and so the Egg­shell is not pressed with the weight of a whole Cylinder of Wheat of [Page 26]ten Foot in height, and proportio­nable in the base to the extension of the Egg-shell, but at the most with a small little Cone of Wheat, perchance not two Inches high; so that the Egg-shell and its little Cap or Cone of Wheat stands as under an Arch, supported by the rest of the Grains in the whole Heap.

2. Although the Grains of Wheat are of visible and considera­ble bulk, yet the position of the Heap of Wheat directs every Grain of Wheat poured upon the Heap accidentally to a lateral pres­sure per declive, which refracts their perpendicular Gravitation. But of this more particularly and evi­dently, when we come to the Gra­vitation of Fluids.

And in conformity to these, or one of these Reasons, I took a Cy­linder of Deal boards nailed toge­ther, and open at both ends, of about [Page 27]two Foot long, and six Inches square in the concave Diam, and took two halves of an Egg-shell, emptied, and clapped them toge­ther, which would not sustein half a Pound weight put upon them, without a total crushing of them.

This Egg-shell I laid in a little bed of Calice Sand, and then putting my hollow Cylinder upon it, and poured into it gently Callice Sand, till I had filled my Cylinder to the top, which contained about four Pound weight of Sand, and that very dry, and then upon the Sand I placed about six or seven pound weight of Lead, and carefully lay­ing down my Cylinder of Sand, I found yet my Egg-shell in the same state as at first, without the least bruising, yea and lifting up the Cy­linder of Sand, I found it so com­pacted, that it would not wholly go out, but remained suspended in [Page 28]the body of the Cylinder, which I attributed, and (as I think) truly to the lateral pressure of the Sand upon the sides of the Vessel, where­by these minute Particles were dri­ven to lean one against another so hard, that they retain'd a kind of Solidity by this renitence.

And I think in this Experiment I have no need to have recourse to an Intelligent Hylarchical princi­ple that suspended the Sand from Gravitation, nor to that other diffi­cult Solution from the Texture of the subjected bodies; but merely to those two formerly mentioned, viz.

1. That each Particle of Sand sustained mechanically the incum­bent Particles, and left my Egg­shell as it were under an Arch, being pressed not with a Cylinder o [...] Sand proportionable to its base, bu [...] at most with a small Cap or Con [...] of Sand, that did not considerably gravitate upon it.

2. That though the Sand is no fluid body, yet the smalness of its Corpuscles had an accidental late­ral Direction per deelive against the sides of the Vessel, which lateral Direction refracted the perpendi­cular Gravitation of the Sand, as will be shewn more, when we come to consider of the Gravitati­on of Fluids, which may be illustra­ted by this Instance.

And because I proposed to prose­cute this Tryal farther, I made an Experiment by a heavier body, namely Leaden Hail-shot.

I took a Cylinder of Latten ware, about two Inches in Diame­ter, and 10 Inches deep, open at both ends, which held about six Pound of Shot. I placed it close to a Table, and filled it, and then gent­ly taking it from the Table, the Shot subsiding expanded into a compass of a Foot Diameter.

I then took the end of an Egg­shell, compressible with less than a Pound weight, placed it in a little Box that was receptible within the cavity of the Cylinder, and filled it up round with Shot, that it might not receive injury by the fall of the Shot through the. Cylinder, and then clapping the Cylinder upon it, filled it up with about six Pound of Shot; but upon the ope­ning of it the Egg-shell was not damnified.

Then I tried it by an Insect, namely putting in a Beetle into the box, and covering him with Shot, so that the fall of Shot from a high­er place might not damnisie him; then putting my Cylinder over the box, filled it up with six Pound of Leaden Shot, and then opening it, I found my Beetle as lively as before, yet a weight of Lead in one solid body, commensurate to the base of [Page 31]the Beetle would have crushed him to pieces.

So that the Non-gravitation of these sinall bodies of Sand, Granner, and Shot, may sufficiently prepare our minds to apprehend one of the reasons of Non-gravitation of Fluids, which though fluid, yet are not disjoined as in those former In­stances, but a continued body, and therefore the upper Particles there­of more capable of support from those subjected Particles.

CHAP. V.

Concerning the Gravitation of Fluids upon subjected Bo­dies, and first of the Gravi­tation of Water.

SOme things must be premised, before I come to the main matter lintend herein.

1. That it is certain Water hath an intrinsecal Gravity of its own, as it is a heavy body.

2. And consequently, if Water be considered separate from Water, as for the purpose when it is put into a Vessel, as a Pail, Bucket, and hollow Cube, or Globe, the Water and the Vessel wherein it is making now one body, doth actually gravi­tate, and hath only one Direction [Page 33]of its motus or conatus ad motum, as other solid bodies have, namely per­pendicular to the Centre of the Earth, which is the Line and Term of its Motion. So that some have by computation estimated that a Cubique Foot of Water weighs about 65 Pound; for here the Wa­ter is not considered as a fluid Ele­ment, but is reduced into the nature of a solid heavy body, by the Vessel wherein it is contained and inclu­ded, which together with it makes up one body, and consequently go­verned by the rules of Gravitation incident to solid bodies, viz. to de­scend perpendicularly. Therefore what I am now to treat of is touch­ing the gravitation of Water, as it is in its own consistency a fluid bo­dy; and herein farther these things are to be admitted: 1. That the gravitation of the fluid water is all one, whether it be [Page 34]in the great vessel of the Sea or Oce­an, or in any other artificial and smaller vessel, as a Tub, Trough, or Cistern, I mean as to the main question; though there may be some various accidental differences in respect of the strength, weight, or consistence of the waters them­selves; therefore the same reason will be of the Gravitation or Non­gravitation of Water upon a subje­cted body, whether it be in the Sea or in a Tub.

2. That without all question, when Water hath its passage out of a Vessel upon or through a ligh­ter medium than it self, it doth actu­ally gravitate; as if a hole be made in the bottome of a Tub, it doth gravitate upon that hole.

I shall not in this place dispute, whether Water in its fluid consi­stency hath not some degree of gra­vitation, for it hath been experi­mented [Page 35]by many, that a Tube of Quicksilver inverted into a vessel of restagnant Quicksilver immer­sed into Water, hath some Indica­tion of the gravitation of Water, by the ascending of the Quicksilver into the Tube, the deeper it is im­mersed in the water: and there may be reason for it, 1. In respect of the interspersions in the water of divers terrestrial Particles, or granula arenae, that are in their own nature heavier than the water; which is visible to the Eye in great Rivers, and much more in the Sea. 2. There may possibly be supposed a small Cap or Cone of water, that may be impendent upon the subje­cted body, that may indure some inconsiderable and scarce percepti­ble gravitation. [Vide quae dicta sunt in fine Capitis 9.]

But that this gravitation is in any degree proportionable to the [Page 36]column of Water, impending upon the subjected body, with a base an­swerable to it; or indeed that it is any considerable pressure in the hundredth degree of such a propor­tion, is most certainly untrue.

And if I should call hereunto the attestation of divers, the Expe­riment of the Tadpoles and Fishes, as well swimming in a great Pro­fundity of water as in a small, nay in a vessel of water compress'd as much as possibly may be with a Rammer; these and infinite In­stancesmore would make it beyond contradiction, that such pressure or gravitation is not at all considera­ble, though some it may be.

And now my business is to ex­amine the reason of this Phaenome­non, namely why the water in the Sea or in a Bucket doth not gravi­tate in proportion answerable to its intrinsick Gravity, or in pro­portion [Page 37]to a column of water, pro­portioned in base to the bredth of the subjected body.

CHAP. VI.

Concerning the Reasons assigned by others for the Non-gravi­tation of fluid Water upon subjected Bodies.

Though some contend for some gravitation of water, yet it is certain, that fluid water doth not gravitate upon subjected bodies in that prodigious proporti­on of weight, that a column of water commensurate in base to the subjected bodies, and extending from them to the superficies of the water,; for if it should, it must crush the subjected bodies to pieces, [Page 38]or at least wholly suspend their mo­tion, for such a column of water, ten or twelve Fathom deep, impending upon a Diver, would amount to some Tuns of Water, which if se­parated in a vessel, would crush all his bones. But the Reasons that Learned men have assigned for this matter, as they differ among them­selves, so they are in themselves very inevident and unsatisfactory, which, as near as I apprehend them, are much of what follows.

Stevinus gives this reason, that the pressure of water is equal every way, upward, downward, and la­terally, and therefore the body of a man being thus equally compressed every way by the circumjacent wa­ter, hath his continuity preserved, and is not crushed by the impen­ding weight of water, neither feels it, but is kept in an equal state and AEquilibrium.

But the truth is, this leaves the difficulty equal, if nor worse than before; for an equal pressure of every side would crush his bowels, and brest, and ribs into an intolera­ble condition, and yet leave him to the severity of the perpendicular weight nevertheless.

Des Cartes gives this obscure and scarce intelligible Reason of it, which, as near as I apprehend him, is thus; Because when the man sinks into the water, as he descends, the subjacent water takes the room that his body left. But this salves not the difficulty of the Non­gravitation of the column of wa­ter, when once got above him.

Mersenius salves it, as he thinks, by the Doctrine of Archimedes, de insidentibus humido, namely that any given portion of water suffers no weight by the superior portion of water, because they are all of one [Page 40]equal Gravity, and therefore every part of water sits quiet in any situs given, without Gravitation or be­ing gravitated by any portion of it self.

And that Bodies heavier than water, (as the body of man is) loseth so much of their natural weight, when in the water, by the weight of such a quantity of water, as is commensurate to the bulk of that heavier body; so that it hath no more than what it exceeds the weight of the like quantity of wa­ter. As if the body of a man weighs 200 Pound, and the like quantity of water would weigh 150 Pound, the body of a man would weigh in water but 50 Pound, and upon this account a Diver might easily e­merge out of the water, for he car­ries with him but 50 Pound weight; and the intermediate wa­ter not being gravitated by the [Page 41]portion of water above it, doth not consequently gravitate upon the man, unless some accident inter­vene, as where the body of the man stops a Leak or a Hole in that ves­sel wherein he is.

But this, though it assert the thing, namely that Water gravi­tates not upon Water, or upon any body of an intrinsick Gravity equal to Water, yet it leaves us in the dark, touching the reason of the Non-gravitation of Water upon the subjacent Water, or any body of an equal intrinsick Gravity with it; since he seems to agree, that the whole Water gravitates upon the Fund or basis of the Vessel, for some have thought it impossible that the whole body of the water should gravitate upon the basis, unless eve­ry part gravitate upon what is in­termediate between it and the basis. Though by the way this is not con­sequential, [Page 42]sequential, for a piece of Lead of a Pound weight doth actually gravi­tate upon the Scale, and yet the up­per part of that piece of Lead doth not gravitate upon the subjacent parts thereof, so long as they are one continued body; and so it may be, and probably is in fluid bodies, while they have their continuity; for a Bucket of water is as much one continued body, as a Bucket of Pitch or Wax, till it be actually di­vided; but of this hereafter.

A later Author, not content with these Explications, hath sup­posed a middle intelligent nature between Almighty God, and Mat­ter, or Bodies, which he calls principium hylarchicum, under whose regiment those various appearan­ces of Nature are managed, of which we cannot find any ready sufficient natural Solution. And al­though the end of this learned Au­thor [Page 43]be good, namely to convince Atheists, and such as deny the Ex­istence of separate or Spiritual In­telligences, yet me thinks the me­dium, at least as to the particular in hand, is not so suitable. The most important and surest Truths in the world never receive so much detri­ment by the Arguments and So­phistry of Opponents, as they do by those Arguments in their favour which have improper mediums to support their Conclusions, or such as are capable of other Solutions.

Most certainly the Ever-glorious and most Wise God is the Author of Nature, and of all the Laws thereof; they are his Institutions by which he orders and regulates the Motions and Appearances in Nature. And he supports them as an Universal Cause, by the constant influence of his Power and Good­ness; and all their Appearances are [Page 44]nevertheless ordinarily regular ac­cording to hisinstituted Laws of Nature. And as it far more ad­vanceth the honour and skill of an excellent Artist, that hath so fra­med and ordered an Automaton, that it may be regularly guided to its end, according to the design of the Artist, without the immediate hand or identifical act of the Artist to guide every motion: so it far more advanceth the glory of the Divine Wisdom, in that he hath setled such a regular order in things of Nature, that may regularly con­duct them to their designed end; then if the Glorious God, or any intelligent Power by him substitu­ted, should by immediate and identical interposition produce e­very Phaenomenon in Nature, saving nevertheless to him his Power and Pleasure pro arbitrio, and upon such occasions as he thinks fit to inter­pose [Page 45]his own immediate power, ei­ther by the determination of his own will immediately, or by the ministration of Angels or Intelli­gences, to advance, correct, or al­ter his standing Laws in particular cases and emergencies.

But yet farther, it seems to me that the particular instance of the Non-gravitation of water deserves no more a recourse to an Hylarchi­cal Agent, than the Instance above given of the Non-gravitation of a heap of Sand, or Corn, or Shot; for I think the Solution of one and the other are rational, and much of the same kind, as to the Mechanical part hereof.

But yet farther, a very Late and Excellent man hath endeavoured to give a Solution of this phaenome­non, which seems less satisfactory than any of the rest; for when he hath abundantly demonstrated by [Page 46]his exact Experiments that Ani­mals do not suffer so great a pres­sure by the incumbent column of water, that doth considerably if at all impede their Animal motion, he attributes it to the Frame and Texture of their Bodies, the orde­ring of their Bones, Muscles, and other parts; and this I confess gra­tifieth the preconceived hypothesis of the Gravitation of the supposed column of water, (as likewise of that of Air, in the Solution of the Torricellian Experiment.) But it seems to me, that this Solution sa­vours more of a Miracle than the former supposition of the Hylar­chical Principle: that a Flownder should at Land be pressed to death by the weight of a gallon of water in a Bucket laid upon him; and yet should not be damnisied by the weight of two, or three, or ten Tun of water in the bottom of the Sea [Page 47]yet he sustains it without detriment or impediment of his life or agil motion: which I say were miracu­lous, if those Tuns of water did a­ctually gravitate in that measure. Therefore I think there had need be some other Solutions than those thought upon, if we can hit upon them.

CHAP. VII.

Concerning the most probable solution of the Phaenomenon of the Non-Gravitation of Water in its fluid consistence.

IN matters controverted, though it be more easie to find faults with the suppositions of others, than to substitute such in their room as may be less capable of Ex­ception; yet it is but just that (if it be possible) for every one that ex­cepts against anothers supposition, should exhibit one of his own, that so he may run the same tryal with o­thers, as others have done with him. And therefore in the former Chapter having (as near as I can understand them) propounded the [Page 49]Solutions of other men, and laid them by, as seeming to me either inevident, or not giving a reasona­ble account of the Probleme, I shall now exhibit my own Conjecture of the Reason of this Appearance in Nature, wishing it no better suc­cess with others, than it deserves.

I have before premised, that 1. this question must not be under­stood of a vessel of water, as the continens and res contenta make but one common Body, for so it is but in nature of a solid and not of a fluid body, and there is in that re­spect no more consideration to be had of its fluidity, than if the wa­ter in the vessel had been congeled into a whole Kegg of Ice; for the Kegg of Ice and the Water in the Bucket, together with the Bucket containing it; or the Water in the Bladder, together with the Blad­der containing it, descend by one [Page 50]simple line of Gravitation, perpen­dicularly from its centre of Gra­vity towards the centre of the Earth: but the question is touch­ing the gravitation of the water in its fluid consistence, though con­tained in the Ocean, or in a Tub or Bucket. 2. That I do not in this place contend against all Gravita­tion of water, for possibly there may be some little allowed it, as un­to Air, and especially by reason of the interspersions in the water (as likewise in the Air) of some small Atomes or Particles of terrestrial Matter, which may be heterogene­ous to the nature of water as such, and as those Particles are in their gravity heavier than water, so they may accidentally cause a greater gravitation in the Particles of some water more than of other, as hath been before said.

But that which I contend for in [Page 51]this place, is first, that the gravita­tion of water in its fluid consisten­cy, whether in the Sea or in a Bucket, if any at all, yet is so incon­siderable, that it doth not conside­rably press upon subjected bodies, nor incommodate Animals that live therein at any profundity, and not in the thousandth part in actu­al gravitation proportionable to the weight of a Column of water commensurate in base to the subje­cted body, and extending from the same to the superficies of the water. Secondly, to assign some reason of such Non-gravitation, and why it is not, no nor indeed can be.

The former of these is in effect confessed by all impartial Writers, and evident to every days experi­ence. The latter therefore, name­ly the reason thereof, are the subject of this Chapters inquiry.

And I think the reasons of this [Page 52]Non-gravitation of the Particles of water upon such subjected bodies, are especially two. The first is Me­chanical, from the structure of the fluid water; and the second is meer­ly natural, from the nature of Flu­ids. Touching the former of these, the Mechanical Solution of this Problem, this hath been in effect given before, in the Non-gravita­tion of the parts of solid bodies while in Continuity, which it is plain though they all together gra­vitate upon the Scale, yet one part doth not gravitate upon another: And water, though a fluid body, yet hath its continuity, which is undivided, and so gravitates not upon its own parts, nor upon any body within it of equal or greater weight than it self. But 2. admit, that water, in respect of its fluidity, should most participate of the na­ture [Page 53]or reason of solute and separa­ble bodies, that are only contigu­ous; yet even in those solute bo­dies, as Sand, Granes, Shot, every Monad of such solute bodies gives support to the superjacent Particles, though not united into one continu­um, as in the instances of a Pyramid of square Stones, a heap of Wheat, or of Callice Sand; wherein a kind of Arch is made over the subjected bodies, that they by no means su­stain the whole weight of the in­cumbent column, proportionate to the base of the body included.

But in case of the body of water, the same advantage is infinitely more improveable for the ease and security of the subjacent bodies, whether animate or not. For al­though I shall not take advantage of the imaginary configuration of the Particles of water invented by des Cartes, who supposeth them to [Page 54]be like small oblong filaments or fibres, not much unlike little Grigs or Eels, which would easily make a consistency, that like an Arch would protect and cover the subja­cent body. Nevertheless I shall say this, that the union of its parts are much closer than that of the Monads of Callice sand, for the water is quid continuum, though fluidum; & therefore as the parts of one conti­nued solid body do not gravitate upon the other parts, but only upon the common base of the whole bo­dy; so the parts of water do not gravitate upon themselves, nor up­on any particular base less than their own base, but one part su­stains the other without any gravi­tation: as the Arch of a well fra­med Vault, doth not press upon the subjected Vault, but each part is sustained by the other, and the whole by those walls from whence [Page 55]the Ribs of the Arch are drawn. A very little industrious trial of the suspension of Sand in a Tube fra­med for that purpose, will make the Instance more intelligible, than words or writing can do it.

It may possibly be true, that a more broad body, heavier than so much quantity of water, may have a greater gravitation of water up­on it than a narrower, because the arch that is made over it by the wa­ter, is greater than that Arch that is made over the narrower body. For instance, let us suppose that in the bottom of a Bucket of water, three foot deep, and one foot in the circumference, there be placed an Ebony rundle, of one Inch thick, and eight Inches Diameter; and in the bottom of the like Bucket there be placed a rundle of Ebony of four Inches Diameter, and of such a thickness as may make the [Page 56]weight of it equal to the weight of the greater rundle, as in the subje­cted Figures.

[figure]

I say it may fall out, that the wa­ter may more gravitate upon the greater Rundle, than upon the les­ser, because that small Cone of wa­ter that is incumbent upon the greater, which hath the larger base, makes a larger Conical body of wa­ter upon that which hath the lar­ger basis, than that which hath the narrower. This may be easily tried by a pair of Scales, industriously or­dered for such an Experiment. But however that fall out, it is most evident, that the whole weight of the column of water, commensu­rate to the base of either Rundle, [Page 57]and extending it self to the superfi­cies of the water, doth not in its full weight gravitate upon either, un­less we suppose a hole in the bot­tom of the Vessel under either Run­dle, and then indeed the water will gravitate upon the Rundle, because it gravitates upon the hole.

But if the subjected body be lighter than the like quantity of water, commensurable to its bulk, then it is true the water will un­dermine that lighter body, and car­ry it to the superficies, notwithstan­ding the superimpendent Cone or Column of water: but this is not to my present purpose to explicate, and therefore I leave it.

CHAP. VIII.

The second and principle Rea­son of the Non-gravitation of Water upon it self, or a sub­jected Animal, or other body.

I Come now to the second princi­pal Reason of this Non-gravita­tion of Water, either upon its infe­riour parts, or upon any subjected Animal or Body, either heavier or equal in weight to the like bulk of Water; for if it be lighter, it will swim, as hath been said. And this I take to be the true natural specifi­cal Reason of the Non-gravitation of Fluids; though the former, namely the Mechanical Reason be­fore given is not wholly useless, but contributes its part to it.

And here I must premise what I before said of that actual gravita­tion, viz. that it is either Motion, or conatus or nisus ad motum.

And therefore let the body be ne­ver so intrinsecally heavy, yet if even by accident (much more if by the natural consistency thereof) that nisus or conatus be suspended or corrected, the Gravitation abateth. For instance, it is most certain that the body of the Earth is intrinsecal­ly heavy, and the heaviest of all Elements that we know of; yet whether we suppose it to be the Centre of the World, or that the Sun is that Centre, and the Earth in its magnus Orbis moves about it, yet it hath no Gravitation to in­cline it to change its place, or its circular motion; and the reason is, because it hath no nisus or conatus to any other position or place then what it hath.

Again, in matters artificial it is plain, that a Pound of Lead hath its natural motion by a per­pendicular direction and line to the centre of the Earth; and this is the true cause of its Gravitation upon my Hand, namely its nisus ad mo­tum; and as any body hath the grea­ter nisus or conatus than another, so it hath the greater actual Gravi­tation, as Gold more than Quicksil­ver, that than Lead, that than Tin, quantity for quantity.

But if I take a pair of Scales, and in one Scale put a pound of Lead, and in another half a Pound, I check and abate its conatus, and conse­quently its gravitation, and it hath but half the vigor of gravitation as it had before; and if I counterpoise it in the other Scale with a full e­qual weight, I suspend totally its gravitation, and it shall ascend or descend with a small advantage of [Page 61]a grane added to the opposite Scale, or to this, and still the reason is the same, the nisus, or conatus ad motum, and consequently the actual gravi­tation depending upon it, is check­ed by the Counter-motion of the opposite Scale. That therefore which I must perform in the appli­cation of this Reason, consists of these Parts or Propositions.

1. The first Proposition, which is this; That which hath several Directions or Lines of its conatus ad motum, must needs have several Di­rections of its Gravitation.

2. That body which hath seve­ral lines or directions of its Gravita­tion variously directed, cannot en­tirely gravitate in one line, or by one direction.

3. That which doth not gravi­tate by one line or direction, but va­riously, it must necessarily follow, that every tendency, line, or dire­ction [Page 62]of its gravitation doth correct and refract the force of its other gravitations according to its other tendencies and directions.

4. That Fluids, and particular­ly that of Water and Air, have se­veral lines of its direction of gravi­tation, and therefore necessarily one must be refracted, impeded, and abated by the other.

5. And consequently, the dire­ction of its perpendicular or lateral gravitation are corrected, and very neer wholly suspended by the other tendencies or directions of its moti­on. And although in order of rea­soning I should begin with the more general Propositions; yet be­cause they will be the best eviden­ced by beginning with the enquiry into the various directions of the motion, conatus and nisus of Fluids, I shall invert the order of that Rati­ocination, and begin at the latter [Page 63]end, namely the various Directions of the conatus or nisus ad motum of Fluids.

That there is a motion, and co­natus ad motum in water, as a heavy body, in a perpendicular line of di­rection toward the centre, all do agree, and it need not be questioned, for it seems it is the primitive cona­tus of this as of all heavy bodies, and is an effect of its intrinsick gra­vity. But besides this primitive motion as a heavy Body, it hath di­vers other motions and directions as a fluid body, and those naturally belonging to it in that consistency. For instance, 1. It hath within the compass of its own superficies a lateral moti­on parallel to the Horizon: which appears by the immersing of a Tube shut at both ends, and placed horizontally below the superficies of the water, and then suddenly [Page 64]unstopping one end, the water will as nimbly move into that Tube, as if it stood perpendicular to the Horizon.

2. Again, within the compass of its own superficies it hath a moti­on, and consequently a conatus ad motum, and consequently a gravita­tion directly vertical; as it a Tube stopt at the lower end, and immer­sed into the water, and then the lower end artificially unstopped, the water will arise in that Tube to the level of the superficies of the stagnant water, and drive out the Air that was in it before.

3. Again, it is certain, that the water in any vessel hath conatus ad motum per declive, in all points be­tween a line parallel to the Hori­zon, and the line of its perpendicu­lar gravitation, according to this rude Diagram in the vessel of wa­ter A.

[figure]

And although for descriptions sake I make these lines of direction per declive, to be from the centre of the superficies of the water, yet I think it improper, and indeed im­possible to shew or define, from what point of the water this cona­tus ad motum per declive begins. Nay farther, it seems evident, that wa­ter being a homogeneal body, every assignable Particle of water hath this direction of descensus per decli­ve, as all other directions incident to its fluid nature, as well as the o­ther [Page 66]ther motions or conatus above speci­fied.

And that the water hath these lateral pressures, and conatus ad mo­tumper declive, is evident to sense; for, take a Barrel set upon his base, and fill'd with water or any other liquor, it will with almost an equal force gravitate upon the sides of the vessel, as well as upon the fund or base, and break out the sides if it be not well guarded with Hoops or other strictures.

Now to apply this position to the former Propositions, I say this various motion and conatus ad mo­tum of Fluids, causeth several kinds and species of lines and directions of their Gravitation, some directly descending, some directly ascend­ing, some Horizontally lateral, some per declive, or medial between a line parallel to the Horizon, and per­pendicular thereunto.

And consequently in the very same fluid body every different di­rection (whether lateral per declive, or perpendicular) of its Gravi­tation is corrected, abated, and refracted by the other; and it is impossible it should have its full swinge of motion any one way, or by any one line, since it hath its considerable motion or co­natus ad motum, the same moment by another line, either contrary or extremely different from the other, omnibus intentus minor est ad singula. And consequently the gravitation of Fluids, whether lateral, or per­pendicular, or per declive, sive per modum lineae subtensae, is abated, cor­rected, and refracted, by the vari­ous lines of its tendency: for it is impossible that the same body can at the same time with its full swinge be carried to any one point, which at the same time hath very [Page 68]neer an equal conatus ad motum to a various point, and by a various line of Direction; or that that Fluid should totis viribus be directed in its motion or conatus thereunto to­wards the centre, which at the same time is directed laterally, or to­wards the North in its lateral mo­tion, or motus per declive, which at the same time hath a direction or tendency towards the South-East or West, or any other point of the Compass, either laterally or per declive.

It is true, that possibly that kind of line of Direction in a perpendi­cular descent may be considerably stronger and more efficacious, and consequently the gravitation that way stronger than in any one o­ther line of direction of its gravita­tion, because there contributes to that motion, not only the nature of Water as a fluid body, but also as a [Page 69]heavy body, which always taketh the shortest line of direction to the centre, which is the perpendicu­lar.

And hence it is, that if there be an Engine consisting of a Base pa­rallel to the Horizon, and a perpen­dicular upon that Base, and a Sub­tense or decline superficies from that perpendicular to the Horizon, as in the subjected Figure.

[figure]

The weight A upon the Sub­tense doth counterpoise to the weight B in a reversed proportion, answerable to the length of the lines C E and C D. So that if the per­pendicular C D be half the length of the Subtense c E, the same weight [Page 70]upon the line C D gravitates double to the same weight A, upon the line C E: because it hath the most expedite and short way to the cen­tre by the perpendicular C D; and the other by C E is longer, and refra­cted, and broken by the inclination and distance C E. But on the other side, if the line of perpendicular descent of the Fluid be compared with all those various and many lines of its other direction, when the centre at least hath any conside­rable depth, the perpendicular mo­tion of its gravitation as a hea­vy body, is either altogether or ve­ry neer altogether corrected, aba­ted, and refracted by its other mo­tions or conatus ad motum, or gravi­tation as a fluid body, since there are as many or more other species of lines directing its conatus ad motum in other lines, as there are of its per­pendicular descent.

And è converso, all the several la­teral lines, or lines of Declivity of its tendency ad motum are so far cor­rected and refracted by its perpen­dicular, and other conatus ad motum, that they are as in the former in­stance of the two equiponderating Ballances, rendred in a manner in aequilibrio, and all of its several lines of Gravitation and tendencies thereunto, are in a very great de­gree suspended and refracted one by another.

And surely this consequence is abundantly evidenced by the in­stances before given, Chap. 4. in the Column of Callice Sand: which is much more confirmed in water. For the Monads of Callice Sand are actually divided one from another, but the Particles of water are con­joined in one Continuum: the mo­tion of Callice Sand per declive is not simply natural, but aceidental in [Page 72]respect of the position of those parts upon which it falls, which because they one hinder another from the next and shortest way to the centre of their motion, by a straight line, therefore move per declive as well as they may. But Fluids have all those varieties of tendencies inci­dent to their nature; yet it is appa­rent beyond all contradiction, that this accidental te [...]dency of the motion of Sands per declive, doth break the perpendicular gravita­tion, and makes it not to gravitate upon the most fragile subjected bo­dy in its full weight.

But I shall yet farther adven­ture to add one farther Explication and Enforcement of this Supposi­tion: it is asserted by some, that a Foot square or Cubique Foot of water, weighs about 65 pounds, which I have not Experimen­ted, and therefore cannot assert; [Page 73]But I will suppose (as making best for the Explication of what I in­tend) it weighs but twelve pound, and this is the entire perpendicu­lar weight of this portion of water; for ex supposito it weighs no more, being put into a Bucket, & weigh­ed in a pair of Scales, with due al­lowance for the weight of the ves­sel; and it is impossible it should be more in the whole than the weight supposed.

But it is apparent, that the dire­ction of this weight of twelve Pound, allowed to the water while it is in the Bucket, is not only per­pendicular upon the Base, but late­rally upon the Sides of the vessel that contains it: and every side of this Cube of water hath as many kinds for its Direction of descent lateral or per declive, as the Base hath for its perpendicular descent.

And yet here is but entirely crie [Page 74]twelve Pound weight of water, that must serve as the common stock of all its Pressures, viz. late­ral per declive, or perpendicular, and must be distributed to all these lines as water from one common Cistern, through so many Pipes to serve all these Gravitations, or conatus ad motum; for it hath not in all above twelve Pound weight to serve all these conatus or Gravitati­ons.

The consequence whereof is of necessity, that this common stock of intrinsick weight of twelve pound, belonging to all this portion of water, is neither intirely allow­ed as the supply or portion of the perpendicular weight or gravita­tion, nor entirely allowed to the la­teral gravitation, or the nisus ad mo­tum per declive, nor to any one kind of Line of either of these conatus; but is indifferently, or very neer [Page 75]indifferently communicated to eve­ry line of its conatus ad motum, whe­ther lineally descending, or colla­terally, or per declive, and the com­mon portion of twelve Pound weight is very neer equally divided to every line of Direction in the water, which are as many as there be divisible parts in the lateral or subjected base of the vessel of water.

And by this distribution it must needs fall out, that the weight of twelve Pound of water is infinite­ly distributed according to various direction, and no one line can pre­tend to the entire gravitation of that twelve pound of water, no nor to the thousandth part thereof, considering its various distribu­tion.

And now if any one shall ask, if the water in the Bucket hath not one entire gravitation towards the Centre in the perpendicular Line, [Page 76]but hath its weight thus distribu­ted to several lines of direction; how it comes to pass that the whole Bucket of water weighs perpendi­cularly twelve Pound, and that weight is not broken by the lateral pressure of the water.

The Answer is plain, and hath been sufficiently insinuated before.

The water in the Bucket is as fluid a body as so much water in the Ocean, and hath the same kind of motion, and conatus ad motum, as well collaterally as by direct de­scent, as is incident to its nature, though it receive an obstruction in that motion, by the strong sides and contignation of the Bucket. But the Bucket of water is now be­come as one solid body, and gravi­tates according to a solid body, viz. per lineam descensionis, and not as a Fluid quoquoversum: and though the fluid water within the Bucket [Page 77]press upon all parts of the Bucket, according to its natural and vari­ous tendency, yet it goes no farther, nor do the sides of the Bucket press upon the ambient Air, or medium, being sufficiently secured by its strength and firmness, and not yeil­ding to the conatus or nisus of the included water.

Many other Instances and Ex­periments might be added for the evincing of the truth of this Suppo­sition, but if I make my self intel­ligible to the Reader, these are suf­ficient to explicate what I mean, and his own observation will fur­nish him with Experiments either to confute, or to confirm what I have said.

And thus far touching the non­gravitation of Water, & the reason thereof; which may be (as I think) applicable to all other fluid bo­dies, as Oyl, yea Quick-silver it [Page 78]self, at least in a great degree, and by analogy of Reason, though I have not had opportunity to Expe­riment it.

CHAP. IX.

Certain Consequences or Conse­ctaries, drawn from what hath been before said.

FRom what hath been before ex­pressed in the two former Chapters, these things seem natu­rally to follow.

1. That the upper parts of a fluid body doth not gravitate upon the lower parts of that fluid body.

2. That if any body of equal weight with the Fluid be within the extent of the fluid body, the fluid body doth not gravitate upon it, nor it upon the subjected fluid bo­dy, [Page 79]but every part holds its station.

3. That a fluid body contained within a solid vessel, doth not with its full weight gravitate upon the base of that vessel that contains it, as the whole body of the Sea, or of the water in a Bucket, doth not gravitate with its full weight upon the entire base that sustains it; and this is in re­spect of the natural consistency and frame of Fluids, not purely up­on the account of Mechanical Su­stentation, which must be agreed somewhere to gravitate, though not upon all parts, as hath been shewn.

4. Though it were granted that the entire bulk and weight of the water in the Sea or a Vessel might gravitate upon the entire base, (which yet is not admitted) yet the parallel parts of water do not entirely gravitate upon a part [Page 80]proportionable to them. For in­stance, suppose a Cube of water in a vessel of nine Inches square; if we should suppose the whole Cube should gravitate upon the base, yet the column of three Inches square in the middle of the Cube would not gravitate upon three Inches square in the middle of the base of the Cube, even for the Mechanical reason above given.

5. That consequently, no bo­dy heavier than water in the base of Fund, doth sustain a weight of water proportionable to such a co­lumn of water as is in the base and top, commensurate to the ampli­tude of the body in the fund or bot­tom.

I shall add this unpolished Experi­ment for the conclusion of this Chap. namely, I made an Experiment touching the weight of a piece of Lead, in several depths of water; [Page 81]I cannot build much upon it, be­cause my opportunities for it were not exact, nor such as others may have, yet I shall offer it: others may make, or possibly have made it with more exactness.

I took a flat round Cake of Lead, of four Inches Diameter, and ma­king four holes in the four quar­ters of it, I suspended it parallel to the Horizon upon a Packthrid of five Foot long, and hanged it to the end of a ballance like the Dish or Scale, and counterpoised the Lead and Packthrid by a weight impo­sed in the other Scale, the Lead and Packthrid in arido weighed ten Ounces, and as much as the Dish wherein the ten ounces were pla­ced, which possibly might be about two ounces more, in all about 12 Ounces.

In a vessel above four foot deep in water, I immersed the Lead four [Page 82]Foot deep in water, and then (as it needs must by the grossness of the medium) it lost part of its gravita­tion, and weighed only eight Oun­ces ½ ¼, besides the weight of the opposite Scale. Then taking up the string shorter, I immersed it only in a Foot depth of water, but yet it gain'd no more weight that I could perceive, but weighed as before one Ounce ½ ¼.

But indeed immersing it onely in one Inch of water below the su­perficies, it increased its weight near ⅛ of of an Ounce, for the Lead weighed one Ounce ½ ¼ ⅛ of an Ounce, or very near thereabouts, besides the weight of the opposite Scale or Dish.

By this rude Experiment it seems the Column of four Foot of water, gravitated no more than one Foot of water; for if it had any accession of weight, it was not perceptible, [Page 83]yet (according to Stevinus calcula­tion, in his 4th book of his Hydro­staticks, (which yet I do not altoge­ther allow) that a Cubique Foot of water weighs 65 Pound), the pro­portion of the Column of 4. foot a­mounts to about 567 square Inches, which is about 8 pound; but the Column of one Foot is but 144 In­ches, which is but about two pound weight of water. I do not trouble my self with curiosity in calcula­tion; but it sufficeth, to give some account of the Imperceptibleness, or at least Inconsiderableness of the difference of the gravitations of Water in various Depths.

CHAP. X.

Concerning the gravitation of the Air.

I Do not intend here to make any large discourse upon this point, [Page 84]because indeed it deserves a larger Examination than this portion of Paper that remains will afford, to unrivet that Opinion touching the Gravitation of free Air, with which many have pleased themselves, and thereby indeavoured to reduce the solutions of Problems and Appea­rances in Nature, but are therein as I think deceived.

That the Air may have Gravita­tion, it being secluded from the am­bient Air by a Vessel (as well as Water) as in a Bladder, none that I know do much deny.

That the interspersions in the Air of halitus terrestres, & vapores aquosi, may have and hath some Gravitation more than what be­longs to pure Air, I shall not que­stion. But that the Air, yea or At­mosphere hath that prodigious gra­vitation, that the late Masters of Experiments have attributed to it, [Page 85]is I suppose a mistaken Assertion. As, for instance, that upon a restag­nant vessel of three Inches diame­ter, the weight of the incumbent column of Air, actually gravitating upon that restagnant vessel of Quick-silver, and commensurate to the base thereof, and extending from the same to the upper surface of the Atmosphere, which they suppose to be 6 or 7 Miles) should counterpoise a suspended column of Quick-silver, which may be 2, 3, 4, or 5 Pounds, according to the bigness of the Tube. This, I say, seems to me but an Imagination, and impossible to be true, and would choak all Animals on the Earth in two minutes, if it were so.

For the plain truth is, the Air, no nor yet the Atmosphere, not­withstanding its interspersions, hath no considerable gravitation upon subjected bodies. And the [Page 86]reason is in effect before given, in the case of the water, and its gravi­tation, but with much greater ad­vantage applicable to the Air.

1. The body of the Air is not only quid continuum, but the parts of it are so contiguated, like a Net, that each part supports another; and its as impossible that one part should gravitate considerably upon any subjected body, as the Arch of Westminster Abby should gravitate upon the people in the Church.

2. The conatus ad motum, and consequently the gravitation of the Air is quoquoversum, viz. sursum, de­orsum, dextrorsum, sinistrorsum, &c. it will come down my chimney, and in at my door, and up my stairs, and these various conatus ad motum of the Air and of its Particles, do necessarily refract any gravitation that it may imaginably have per li­neam perpendicularem descensus, and [Page 87]renders it equable and disingaged from any one line of presence.

And by this conatus ad motum, I mean not that Imaginary Elaterium which some have called in to the Aid of their solution of the Torricel­lian Experiment, which I must needs say needs more help than one: for though Air violently compress'd, as in Wind-guns, hath its conatus of restitution to its natu­ral staple, and being expanded by Rarifaction, hath its natural moti­on or conatus of restitution to its due consistency, as appears in the Torricellian, and divers other Expe­riments; yet the great Elaterium of the Air in its natural consistence, called in by some to help at a lift, as it hath little evidence, so it contri­butes less to the solution.

Indeed it hath a Fluidity greater than Water, and therefore is move­able to all places for its reception. [Page 88]It is compressible, which water is not; but for any Elaterium, or such considerable Expansion of it self, as to offer any force to other bodies, seems unwarranted by reason or Experience, or common sense, un­less where by violence or accident compressed or expanded beyond its natural size.

But I do not at present pursue this matter to all its Refuges, it re­quires more time and Paper, and will exceed the bounds of my inten­ded Pamphlet; and besides, the Discussion beforegoing, touching the reason of Non-gravitation of Water, renders that concerning Non-gravitation of Air easily in­telligible, and applicable to it, with much greater advantage of reason and evidence.

FINIS.

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