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 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. 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 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 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 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 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 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 And consequently if there were another Staff set on cross from E to F of the same length each Supporter would bear but a fourth part of the Weight This being premised
it I found my Beetle as lively as before yet a weight of Lead in one solid body commensurate to the base of 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 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 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 Non-gravitation 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 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 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 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 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 Non-gravitation 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 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
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 non-gravitation of Water the reason thereof which may be as I think applicable to all other fluid bodies as Oyl yea Quick-silver it 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 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 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 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 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 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 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 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 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 it s 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 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 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
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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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. 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 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 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 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 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 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 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 teâ—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 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 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 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 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 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