We daily fee great Ships, whilft floating in the Water, mov'd with little Bodies ftriking againft them. From which Experience I conclude, notwithftanding all the fubterfuges of Monfieur des Cartes and the Cartefians, that if thefe great Bodies were in a Vacuum, they might be moved with much greater facility, fince the Realbn of a Veffel's being mov'd in the Water with fome difficulty, is the refiftance the Water makes to the imparted Motion; which in a void fpace will not be found. Now that which manifeftly fhews that Water refills the Motion imprefTed on the VefTel, is the cefTation of its Motion fome time after the Impulfion, which certainly would not happen, did not the VefTel lofe its Motion, by communicating it to the Water; or if the Water yielded to its paffage without any oppofition; or laftly, imparted to it fome of its own Motion. Therefore fince a VefTel agitated in the Water, ceafes by degrees to move, 'tis an infallible fign that the Water, initead of forwarding, as Monfieur des Cartes pretends, withftands its Motion; and confequently it would be infinitely eafier to move a great Body in a Vacuum than in Water, fince there would be no refiftance on the part of furrounding Bodies. 'Tis evident therefore, that Reft has no Force to refill Motion, and that the leaft Motion contains more Power and Force then the greateft Reft; or at leaft, that we ought not to meafure the Force of Motion and Reft, by the Proportion we find between the Magnitude of Bodies in thofe two States, as Monfieur des Cartes has done.
'Tis true, there is fome reafon to believe that the VefTel is mov'd, whilft in the Water, by rea- fon of the continual change which happen in the watery parts about it, though to us it feems not to change its place: And this has been an inducement to M. Des Cartes and fome Pcrfons ro ° Z believe oo F. Malebranche Concerning Bdo k VIl believe, that 'tis not the bate Force of the impelling Agent which makes it advance in Water 5 but that having before received a great deal of Motion Irom the little parts of the furrounding Liquid, which prefs it equally on all fides, this Motion, is only determined by the adventitious. Motion of the impelling Body •, fo that what moves a Body in Water, could not do it in a Va- cuum. ' And thus it is that M. Des Cartes and his Followers defend the Rules' of Motion they have given us.
Let usfuppofe, for Example, a Piece of Wood of a Foot fquare, plac'd in a liquid Body, all the little parts whereof aft and move againft it •, and becaufe they prefs it equally on all fides, as"* well towards A as B, the piece of Wood ftirs. neither one way nor another: Now if I drive ano- ther Piece of Wood of half a Foot againft the former, on the fide A, I lee it advance forward h hence I conclude, that it might be mov'd in a Vacuum with lefs Foice than that of the Piece that drives it, for the foregoing Reafons. But the Perfons L-fpeak of deny it, and anfwer, that therea- * Art. 5. fon of the greater Piece's advancing, when urg'd by the little one, is, that the * latter unable to move ■ it fingly, being joyn'd with the parts of the agitated Liquid, determines them to drive it by im- parting fome of their Motion to it. But 'tis manifeft that by this Anfwer, the Piece of Wood, when Once mov'd, could never diminifh its Motion •, but muft, on the contrary, perpetually increafe it. For according to this Anfwer, the Piece of Wood is more driven by the Water to the fide of A than B, therefore it mull: perpetually proceed-, and becaufe this Impuliion is continual, its Motion muft conftantly increafe. But, as I have faid, the Water is fo far from facilitating its Mo- tion, that it continually refills it; which refiftance ftill leffening it more and more, at laft makes it altogether infenfible.
But I am now to prove that the Piece of Wood which is equally pnfti'd by the little parts of the encompaffing Water, has no Motion or Force at all, capable of moving it, though it continually changes its immediate place; and the Surface of the Water round it is different at different times. For if it be fo that a Body equally prefs'd on all fides, as a Piece of Wood, be deftitute of Motion,. undoubtedly that foreign Force that ftrikes againft it, muft communicate it, fince at the time of this Force's urging it on, the Water refifts, and infenfibly diflipates the imprefs'd Motion, cauf- ing it, by little and little, at laft to ceafe.
it is certain, at leaft to thofe I fpeak to, that there is no more Motion in Nature at one time than another; and. that Bodies at reft cannot be put in Motion, but by the Collifion of fome agi- tated Bodies, which communicate their Motion to them. Whence I conclude, that a Body, which I iuppofe created perfectly at Reft in the midft of Water, will never receive any degree of Motion, from the little parts of the Water which furround it, and which ftrike continually againft it, provided *heir Force be equal on all fides-, becaufe all thefe little parts which daifi e- qually againft it on all fides, rebounding again with their whole Motion, communicate none of it} and coniequently this Body ought to be confider'd as at Reft, and without any moving Force, though it continually changes its Situation.
Now the proof I have for the rebounding of thefe little parts, together with their whole Mo-' tion, is this -, That otherwife the Water which touches this Body, muft grow very cold, or even congeal'd, and become almoft as hard as the Wood upon its Surface, fince the Motion of the watry parts ought to be equally diffus'd into the little parts of the Body they encompafs.
But that I may accommodate my lelf to the Patrons of M. Des Cartes's Opinion, I am willing to grant that we ought not to confider a VefTel on the Water as at Reft. I grant likewife, that all the parts of the environing Water are fubfervient to the new Motion imprinted by the Wa- terman, though it be but too vifible by the decreafe of the Boat's Motion, that they refift it more on the fide where it makes, than on the other whence it is driven: Notwithftanding which fuppofition, I fay, that of all the Parts of Water in the River, according to M. Des Cartes, there are none which can promote the Motion of the VefTel, except thofe which immediately *Arf. 62,. touch it on the fide it is driven on. For * according to that Philofopher, The Water being fluid, all the parts that go to its Compofition, aft not conjointly againft the Body we would move; but only iboje which touching it, conjointly bear upon it. But thofe which conjointly bear upon the VefTel, and the BoatVman together, are twenty times more inconfiderable than the Boat. 'Tis plain therefore, from the Explication given by M. Des Cartes in this Article, concerning the difficulty we find to break a Nail between our Fingers, that a little Body is capable of moving one much bigger than it felf For in ftiort, our Hands are not ib fluid as Water -, and when we would break a Nail, there are more parts that aft jointly in our hands, than in the Water which putties a- gainft a VefTel.
But here's a more fenfible Experiment. Take a Plank well fmooth'd, or any other very hard Plain, drive in it a Nail half way, and let this Plain in a fomewhat inclining pofture -, then place a Bar of Iron an hundred times thicker than the Nail, an Inch or two above it, and letting it ilide down, it will not break it. Mean time it is obfervable, that, according to Des Cartes, all the parts of the Bar, as being hard and folid, act jointly upon the Nail. It therefore there were no other Cement than Reft to unite the parts of the Nail, the Bar of Iron being an hundred times big- ger, ought by the Fifth Rule of M. Des Carles, and according to Reafon, communicate fomewhat of its Motion to the part of the Nail it fell upon; that is, to break it, and pais on, even though this Bar ihould Hide with a very gentle Motion. Therefore we muft feek fome other Caule than the Reft of Bodies, that makes them hard, and capable of refilling the violence that is offer'd to break them, fince Reft has no Force to withftand Motion: And I am perfuaded thefe Experien- ce are lutticient to evince, that the abftracled Proofs we have given are not talfe.
We Chap. IX. The Search after Truth. pi We rauft then examine the third Thing we fuppofed before might be the caufe of the fferi£t Union found between the Parts of hard Bodies ^ namely, an invisible Matter which furrounds them; and which being rapidly mov'd, pulhes moll violently the external and internal Parts of thefe Bodies, and conllringes them in fuch a manner as requires greater ftrength to feparate therri, than has that invifible and extremely agitated Matter.
Methinks I might reasonably conclude, that the Union of the conftituent Parts of hard Bo- dies depends on an invifible Matter which furrounds and comprelTes them, fince the two other things, fuppoled poflible Caufes of this union^ have been difcover'd not to be truly lb. For fince I meet with Refiftance in breaking a Piece of Iron, which Refiftance proceeds not from the Iron, nor the Will of God, as I think I have proved, it rauft necelTarily proceed from fome invifible Matter, which can be no other than that which immediately furrounds and comprelTes ir. Ne- verthelefs, I fhall give fome pofitive Proofs of this Opinion, after I have more largely explain'd it by fome Inflance.
Take a Globe of any hard Metal, which is hollow within, and divided in two Halfs, join them together with a little Bond of Wax at the place of their Union, and then extract the Air: thefe two half Globes will be fo nimby join'd to one another, that two Teams of Horfes fallned to the Rings on the oppofite fides of the Globe, fhall not feparate them, provided they be large in proportion to the Number of Horfes; when yet if the Air be fuffer'd to enter, one Man fhall feparate them with a great deal of Eafe. From this Experiment 'tis eafie to conclude, that what united the two iicmifpheres to one another, was the PrefTure of the furrounding Air Upon their outward and convex Surface, whilft there was no Compreflion in their concave and inward parts j fo that the A£lion of the Horfes which drew the two He?nifpheres on either fide, could not con- quer the Refiftance made by innumerable little Parts of Air, by their preffing thefe two Halfs: But the leaft Force is capable of dividing them when the Air entring in the Copper Globe, drives againft the Concave and inward Surfaces, as much as the external Air preffes againft the outward and convex.
Take, on the contrary, the Bladder of a Carp, and put it in a VefTel from which the Air is pump'd: this Bladder being full of Air, will crack and burft, becaufe then there is no exteriour Air to refill that within the Bladder. 'Tis likewiie for the fame'Reafon I have given of the firfl Experiment, that two Glafs or Marble Plains, ground and polifh'd upon one another, fo cling toge- ther, that Violence mufl be us'd to feparate them one way; becaufe the two parts of the Marble are preis'd and conftring'd by the external Air that furrounds them, and are not fo llrongly prefs'd by that between. I might produce infinite other Experiments to prove that the grofs Air which furrounds Bodies ftrongly unites their Parts: But what I have faid is enough to give a diftinO: Explication of my Thoughts upon the prefent Queftion..
I fay then, that what caufes the Parts of hard Bodies and the little Fetters before-mentioned to hang fo clofely united to each other, is, there being other little Bodies infinitely more agitated than the courfe Air we breath, which bear againft them, and comprefs them h and that which makes it fo hard to feparate them, is not their Reft, but the Agitation of thefe little furround- ing Bodies. So that that which refills Motion' is not Reft, ( this being but the Frivation of it, and has no Force at alL,) but fome contrary Motion.
This fimple Expofition of my Opinion perhaps feems reafonable-, yet 1 forefee, that many Perfons will not eafily be indue'd to yield to it. Hard Bodies make fo great Impreflion on the Senfes when they ftrike us, or when we ufe Violence to break them, that we are inclin'd to be- lieve their Parts more ftriftly united than they really are. And on the contrary, the little Bodies which I have faid encompafs them, and to which I have alcribed the Force of caufing this Union, making no Impreflion on our Senfes, feem too weak to produce fo fenfible an Effect.
But to take away this Prejudice, which bottoms on the Impreffions of our Senfes, and on the Difficulty we find to imagine Bodies more little and agitated than thofe we daily fee j 'tis to be confider'd, that the Hardnefs of Bodies is not to be meafur'd with relation to our Hands, or the Endeavours we are able to make, which are different at different times. For indeed, if the great- ell Force of Men be nothing in comparifon with that of the fubtle Matter, we mould be much to blame to believe, that Diamonds., and the hardeft Stones, cannot derive their Hardnefs from ' the Compreffion of thofe little rapid Bodies which environ them. Now we may vifibly difcover how inconfiderably weak is Humane Force, if it be confider'd that Man's Power of moving his Body in fo many manners, proceeds from a very moderate Fermentation of the Blood, which fome- what agitates the fmaller Parts of it, and fo produces the Animal Spirits. For 'tis the Agitation of thefe Spirits, which makes the Strength of the Body, and gives us the Power of making thofe Endeavours "which we groundlefly regard, as fomething great and mighty.
But it muft be obferv'd, that this fermentation of our Blood, is but a fmall Communication of that fubtle Matter's Motion we have been fpeaking of. For all the Fermentations of vifible Bodies are nothing but Communications of Motion from the Invifible, fince every Body receives its Agitation from fome other. 'Tis not therefore to be wonder'd if our Force be not fb great as that of the fame fubtle Matter we receive it from. But if our Blood fermented as much in our Heart as Gun-Powder ferments, and is agitated when Fire is put to it •, that is, if our Blood re- ceived as great a Communication of Motion from the fubtle Matter, as Gun-Powder receives, we might do extraordinary things with a great deal of Eafe •, as break a Bar of Iron, overturn an Houfe, &c. provided we fuppofe a competent proportion between our Members and our Blood fb violently agitated. We mult therefore rid our felves of our Prejudice, and not, following the Impreflion <p2 F. Malebranche Concerning Book VI.
Impreffion of our Senfes, imagine that the Parts of hard Bodies are fo ftrongly united to one ano- • ther, becaufe of the Difficulty we find to break them.
But if moreover, we confider the Effects of Fire in Mines, the Gravity of Bodies, and feve- ral other natural Effefts, which have no other Caufe then the Commotion of thefe irifenfible Corpiifcles, as is prov'd by M. Des Cartes in many places of his Works, we fhall manifeftlv dii- cover, that it does not exceed their Force, to unite and bind together the Parts of hard Bodies ib powerfully as we find them. For in fhort, I fear not to affirm, that a Cannon-Bullet, whole Motion feems fo extraordinary, receives not the thoufandth part of the Motion of the fubtle Matter which furrounds it.
My AiTertion will not be doubted of, if it be confider'd, Tirft, That the Gun-Powder is not all inflam'd, nor at the fame inftant: Secondly, That though it were all on Fire in the f elf-lame Mo- ment, yet it floats a very fhort time, in the fubtle Matter; and Bodies fwimming but a little while in others, can receive no great Motion from them; as may be feen in Boats when riding in a Scream, which receive their Motion by degrees. Thirdly, and principally, That each part of the Powder can receive but a collateral Motion, which the fubtle Matter yields to. For Water only communicates to the VelTel the direQ: Motion which is common to all the parts of it, which Mo- tion is generally very inconfiderable in refpeft of the others.
I might ftill prove to M. Des Cartcs's Followers, the Geatnefs of the fubtle Matter's Motion, by the Motion of the Earth, and the Heavinefs of Bodies; from whence might be drawn verv certain and exacf Proofs, if that were neceifary to my Subject But in order to have one i'uf- ficient Proof of the violent Agitation of the fubtle Matter, to which I afcribe the Hardnefs of Bodies, it fufjkes (without feeing Des Cartes's Works) to read attentively what I have written in the J'econd Chapter of the fourth Book, towards the End.
Being now deliver' d from our Prejudices, which induc'd.us to believe our Efforts very potent, and thole of the fubtle Matter which furrounds and conftringes hard Bodies, very feeble •, being, likewife fitisfied of the vehement Commotion of this Matter, by what has been faid of Gun- Powder •, 'twill be no hard Marter to difcover, that 'tis abfolutely neceifary that this Matter, act- ing infinitely more on the Surface, than the Infide of the hard Bodies it encompaffes and com- prelfes, ihould be the Caufe of their Hardnels, or of the Refiftance we feel when we endeavour to break them.
But fince there are always many Parts of this invifible Matter pairing through the P6res»of hard Bodies, they not only render them hard, as I have before explain'd; hut are alfo the Caufes that fome are fpringing, and elaftical, that others ftand bent, and others ftill are fluid and liquid < and in fhort are the Caufe not only of the Force which the Parts of hard Bodies have to remain dole by one another -, but of that likewife which the parts of fluid Bodies have to feparate; or which is the fame thing, are the Caufe of the Hardnefs of fome Bodies, and the Fluidity of others.
But whereas 'tis abfolutely neceffary to know diftin&ly the Phyficks of M. Des Cartes, the Fi- gure of his Elements, and of the parts which conftitute particular Bodies, to account for the ftiffnefs of fome and the flexibility of others,. I lliall not infift upon explaining it. Such as have read the Works of that Philofopher, will eafily imagine what may be the caufe of thefe things y whereas it would be a difficult task for me to explain it; and thofe who are unaquainted with that Author would have a very confus'd Notion of the Reafons I might offer.
Nor fhall I ftand to refolve a vaft number of Difficulties which I forefee will be urg'd againft what I have been eftablifhing, becaufe if thofe who propofe them have no knowledge of true na- tural Phiiofophy, I mould but tire and confound them inftead of fatisfying them. But if they were Men of Science, I could not anfwer them. without a long train of diagrams and reafon- ing. Wherefore I think it belt to intreat thofe who (hall find any Difficulty in what I have faid, to give this Difcourie a more careful perufal; not doubting but if they read it and confider it as they ought, all their Objections will fall to the Ground. But after all, if they think my Requelt inconvenient, let them fit ftill, there being no great danger in the Ignorance of the Caufe of the Hardnels of Bodies.
I ipeak not here of contiguity: for 'tis manifeft that contiguous things touch fo little, that there's always a good quantity of fubtle Matter palling between them, which endeavouring to continue its Motion in a right Line hinders them from uniting.
As to the union found between two Marbles that have been polifh't one upon another, I have already explain'd it -, and 'tis eafie to fee, that though the fubtle Matter paffes conftantly between the two parts, as dole as they are yet the Air cannot get in; and therefore 'tis that which compreffes and conftringes the two parts together, and makes them fo difficult to be difunited, unleis we glide them over one another.
1 or all this it is manifeft that the Continuity, Contiguity and Union of two Marbles would be one and the fame thing in a vacuum t for neither have we different Ideas of them, fo that it would be to talk without underftanding our felves to make them differ abfolutely, and without any regard to the lurrounding Bodies.
i now come to make fome Reflexions upon M. Des Cartes's Opinion, and the Original of his Eirour: I call his Opinion an Errour, becaufe I can find no fincere way of defending what he has faid upon die Rules of Motion, and the Caufe of the Hardnefs of Bodies towards the end of the fecond Part of his Principles in leveral places •, and that he feems to have evidently prov'd the •Truth of the contrary Opinion.
This Chap. IX. The Search after Truth. 90 This great Man moft diftinctly conceiving that Matter could not naturally move it felf, but that the moving Force or" all Bodies was nothing but the general Will of the Author of Nature; and that therelore the Communications of their Motion upon their mutual Collilion, mult come from the fame Will, yielded to be carry 'd away with this Notion, That the Rules of the different Communication of Motions mult be ietch'd from the Proportion found between the different Mag- nitudes of Colliding Bodies •, it being impoflible to penetrate into the Defigns and Will of God. And whereas he concluded that every thing had theJForce to perfevere in its preterit State, whether it were in Motion, or Reft, becaufe God, whole Will conltituted this Force, a£ts always in the lame manner; he inferr'd that Reft had an equal Force with Motion. Thus he meafur'd the Ef- fects of the Power of Reft by the Greatnefs of the Body it refided in, as well as thole of Motion: And hence he gave the Rules of the Communication of Motion which are ken in his Principles, and the Caufe of the Hardnefs of Bodies, which I have endeavour'd to refute.
Tis a hard matter not to fubmit to the Opinion of Monfieur des Carles, when we contemplate it on the fame fide: For, once more, fince the Communication of Motions proceeds only from the Will of the Author of Nature, and rhat we fee all Bodies continue in the State they have once been put in, whether it be Motion or Reft, it feems that we ought to feek for the Rules of the different Communications of Motion upon the Concourfe of Bodies -, not in the Will of God, which is un- known to us •, but in the Proportion that is found between the Magnitudes of thefe fame Bodies.
I do not therefore admire that Monfieur des Cartes ftiould light upon this Notion; but i only wonder he did not correct it, when having pufh'd on his Difcoveries, he found out the Exiitence, and fome Effects of the fubtile Matter which furrounds all Bodies.
I am furpriz'd to find him, in the 13 2d Article of the Fourth Part, attribute the El aft ick Force of certain Bodies to the fubtile Matter, and yet not afcribe to it their Hardnefs, and the Refiltance they make to our Endeavours to bend and break them:, but only to the Reft of their Parts. For Art. 55. & I think it evident, that the Caufe of the Elaflicity and Stiffnefs of fome Bodies, is the fame with 4?- of the that which impowers them to refift the Violence that is us'd to break them: For indeed, the Force ^nd^dfe-' . which is employ'd in breaking a piece of Steel, has but an infenfible Difference from that which where. is us'd to bend it.
I mean not to multiply Reafons here, which one might give for the proving thefe things •, nor to aniwer fome Difficulties poffible to be urg'd about Bodies which are not fenfibly [fringing, and yet are difficultly bent; For all thefe Difficulties vanifti, if we confider that the fubtile Matter cannot eafily make new Tracks in Bodies which break in bending, as in Glafs and temper'd Steel; which it can eafier do in fuch Bodies as are compos'd of branchy Parts, and that are not brittle, as in Gold and Lead: And Laft/y, that there is no hard Body, but has fome kind of Elaterium.
'Tis a hard matter to perfuade one's felf that Monfieur des Cartes did pofitively believe the Cauie of Hardnefs to be different from that which makes the Elaflicity •, and what looks moft likely, is, that he made not fufficient Reflexion on that matter. When a Man has for a long time medita- ted on any Subject, and is well fatisfied about that of his preient Enquiry, he commonly thinks no farther on it -, he believes that the Conceptions he had of it are undeniable Truths, and rhat it is needlels to examine them any more. But a Man has fo many Things in him which difrelifh his Application, provoke him to precipitate Judgments^ and fubje£t him to Errour, that though his Mind remains apparently fatisfied, yet it is not always well inftrucf ed in the Truth. Monfieur des Cartes was a Man, like us: No greater Solidity, Accuracy, Extent, and Penetration of Thought is any where to be met with, than in his Works, I confefs; but yet he was not infallible: There- fore 'tis very probable he remain'd fo fettl'd in his Opinion, from his not fufficiently reflecting that he aiTerted fomething in the Confequence of his Principles, contrary to it. He grounded it on ve- ry fpecious and probable Reafons-, but fuch notwithftanding, as being not capable of themfelves to force his Confent, he might ftili have fufpended his Judgment •, and confequently, as a Philo- fopher, he ought to have done it. It was not enough to examine in a hard Body, what was in it that might make it fo -, but he ought likewife to have thought on the invifible Bodies, which might give it Hardnefs; as he did at the End of his Pbilofopbical Principles, when he afcrib'd ro them the Caufe of their Elafticity: He ought to have made an exa£t Divifion, and comprehenure of whatever might contribute to the Hardnefs of Bodies. It was not enough to have fought the Caufes of it in the Will of God ^ he ought alfo to have thought on the fubtile Matter, which fur- rounds thefe Bodies: For though the Exiftence of that violently agitated Matter was not yet pro-. ved in the place of his Principles where he fpeaks of Hardnefs:, it was not however rejected; he ought therefore to have fufpended his Judgment, and have well remember'd that what he had written concerning the Caufe of Hardnefs, and of the Rules of ^Motion, was fit to be revis'd; which I believe was neglected by him •, or at leaft, he has not fufficiently confider'd the true Rea- fon of a thing very eafie to be difcover'd, and which yet is of greateft Confequence in Natural Phi-' lofophy. I thus explain my felf: Monfieur des Cartes well knew that to the Support of his Syftem, ( the Truth of which he could not reafonably fuf pe£t, ) it was abfolutely necellary that great Bodies ftiould always communicate fome of their Motion to the leiTer which they met with •, and that the latter fhould rebound at the Encounter of the former, without the like Lois of their own: For otherwife, the firft Element would not have all the Motion that is neceflary above the fecond, nor the fecond above the third 5 and fo all his Syftem would be abfolutely falfe, as is manifeft to thofe who have a little confider'd it. But in fuppofing that Reft has Force to refift Motion, and that a great Body in Reft cannot be mov'd by another lefs than it felf, though moft violently ftriking againft it, 'tis plain that great A a Bodies a a F. Malebranche Concerning Book VL