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Show NA are reciprocally three forefollows : {otion, confid ; i vd by Natural Agents: it never has yet been _obfervd that any Body did bring itfelf from ? to Motion ; nor that eve Motion did bring itfelf to Re? ; ever any Body in Motion alter’d its Cc i f: But that t | gs would run e be any Univerfe. Vettel It for ev were not I ne(s of the Place on if fome Body by alter their Courfe I Motion ft or the r movd:; or t tion did not TaMEr ce, a. Eop; on, hinder one if the Air 1, would f ft of a Mafs of Matter This Vis Inertia, .or Paffive Principle, is effential to Matter for it neither can be ivd of it, nor ‘intended or remitted in the fame Body, but is always in Proportion to the Quantity of Matter Bodies do contain. From what hasbeen before faid, the following Corollaries may be deduc’d: a. Tt appears plain from hence, Thatnei- any Particle of Matter, or Combination rticles, #.e. No Body, can either move or themfelves, or alter the Direéion r Motion by themfel : For Mat1 is not -endow’d with SelfMotion, with a Powerto alter the Courfe in \ put ; but is ly Paffive, and mu of itfelf for ever continue in that fame and dr Direction. And befi Principle, which t call’'d, The Mis In Plane ; for at the firft, while the Veffel js in Motion along the Plane, the Liquor in jt feems to move with a Direétion contrary to that of the Veffel, the Water rifing on the hinder Side of the Veffel This is not becaufe there is any fuch stion imprefs’d upon the Ws er, but be. the ¢ endeayouring byits Vs Inertie to continue in its State of Re/, the Veffel is not able to communicate its Motion to it immediately, becaufe of the Bulk and fluid State of it; but the Water perfeveres its State of Reft, while the Veffel makes forward, and fo feems to move a contrary Way. But as foon as the Water has the Motion of Veffel intirely communicated to it, and begins to move with a Velocity equal to that of the Veffel ; if youftop the Veffel on a fudden, the Waterftill continues its Motion, and dafhes over the Sides of the and Courfe m iI f it cannot i is fettled in, for ev of irfelf, ic never can when it is in MoIter its Courfe, elf aftera particular b Bodies do to the utmoft of their Powe any Change or Alteration of t whateverit be, either of Ref its Direction ; and this Re equal in the fame Body ; a1 dies is proportional to the Qu they contain. i [here is as much Force requir’d to ftop a Body in Motion, is requir’d to put it into Motion, and on t nd therefore fince the far the contrary equal Changes of this Refiftance will as po fully operate keep a Body in Motion, as to k ep it at Ref 2 and by. confequence it can nevér char i State of Ref, A 2 or Direétion ofitfelf: hence, that no fe 2. , will of itfelt M whenit is once put naturally move in a curve Line lly forward in the fame ftra i “Dire@ion of the Movit atfoever does move in a cut ¢ alter its Direction in every Point ; no Body can naturally move © in a curve Line. 3. Hence it appears, that thofe great Bond G ets, their Satellite are at firft y z not naturally, and of them i their move itfelf another way, is one and the fame thing ; fo that Matterofitfelf fo farindi Tent as to Motion or Re/?, that it is not inclin’d More to one thanit is to the other ; and does refift a Change from Re? to Moti Much as it does from M tion to Ref. This Paffive Principle in Matter, or Vis Inertia, is very confpicuous in the Motion of a Veffel full “of Liquor upon a Horizontal g Force; Li for eve eve’ htt Lines for © Motions of thefe does no lefs refift its being chang’d from Rez to Motion, than it does being chang’d from Motion to Reft. Andas any Force will imprefs fome Degree of Motion on a re{ting Body ; fo; in like manner, the fame Degree ofForce being imprefs’d at the fame Time with a contrary DireCtion, will bring it again to Refs but it is not abfolutely neceffary, as to the Being of Matter, that it be either in Motion or vet. For, let Matter be in which of thefe States foever, it will ftill be Matter. And fo; fince the Vis Inertie or paffive Principle is effential to Matter, it thereby becomes indifferent wi they would run ou And of ‘ies Conie in thei Of bits depend abfolutely Force. And thence it is, 4. That neither Motior of them particularly) is effe That is as much as to fay, th at Mat - ter a different as to either of thefe partic arly, ae doe Body was before in Motion, the Motion which arifes from that impre{s’d Force, ifin the fame Direction, does fo much increafe the former Motion ; if it has a contrary Direétion, ‘it deftroys a Part of the former Motion, equal to that which is imprefs’d; when it has a Di- rection oblique to the former Motion, it is either added to or fubtraéted from the former Motion, according as the Motion, arifing from a Compofitionofthefe two, is determin’d. From what has been faid, it plainly appears, That in the prefent Conftitution of Things, there can be no perpetual Motion. By a as to Ref} or Motion, and is equally fufceptible perpetual Motion you are to underftand an unof either, according as the external Force interrupted Communication ofthe fame Deurges it. 5. Hence may be demonftrated the Necef= fity of a Vacuum, or Space diftin@ from Matter: For fince it is fo that all Bodies do by their Vis Inertia, to the utmoft of their Power; gree of Motion, from one Part of Matter to anothet in a Circle: Not as Bodies, which are put into a Motion, do for ever continue in the fame, unlefs fo far as they are refifted or ftopp’d by other Bodies ; but a Circulation of refift any manner of Change or Alteration of the fame Quantity of Motion, fo as it returns their State either of Ref or Motion; and fince perpetually undiminith’d fromthe firft Mover. the Refiftance is always equal in the fame For, Motion produe’d (by the Law) is but Body, or the fame, andin different Bodies, is proportionable to the Quantity of Matter whereoftt y confift; and fince, by Confequence, if two Bodies which contain equal Quantities of Matter, moving with equal Quickne{s in contrary Direétions, fo that they {trike dire€tly upon one another, they will for ertain both ref or ftop at the Point of their Meeting or Concourfe; as alfo it being demonftrable, That two Bodies moving with equal Celerities contrary one to the other, and both refting where they meet; are equally heavy; it then follows of Neceflity; that two Bodies; which contain. equal Quantities of Matter, are equally heavy: andif this be allow’d, if there were two Spheres of equal Diaimeters; and there were no Vacuities in Bodies; they would contain equal Quantities proportionable to the Force generating ; and all the Motions which are perform’d onthis Globe, being perform’d in a refifting Fluid (the Air) a confiderable Quantity of this Mo- tion muft neceffarily be fpent in the Communication, oh this Medium, and fo of confe= quence it is impoffible that the fame Quantity of Motion fhould return undiminifh’d upon the firft Mover; whichis neceflary, in order to a perpetual Motion. Befides, fuch is the Nature of material Or- gans, That a greater or leffer Degree of Fri¢tion cannot be avoided, although the Ma- chine fhould be fram’d according to the moft exact Principles of Geometry and Mechanicks, there not being in Nature any Congruity that is perfect, or Smoothnefs that ig exact; the Manner of Cohefion of Bodies ; the finall Pro- of Matter, and of confequence would be of equal Weight, i.e. Two Spheres; the one of Wood, andthe other of Gold, would have the fame Specifick Gravities ; but this being contradiéted by Experience, Vacuities in the portion the folid Matter bears to the Vacuities in them, not admitting of them fo to be. And befides, an ordinary Microfcope will difcover how very imperfeét our moft finifh’?d Mecha- Vities, nicated, it is impoffible there fhould be a perpe- Sphere of Wood muft of Neceffity be admitted to anfwer for the Difference of their Gra. As to the Second, That the Changes mdde in the Motion of Bodies are always proportional, &c. that maybeilluftrated by the following Confiderations : Effeéts are always in Proportion to their adequate Caufes; and if any Degree of Force Produce any Degree of Motion, then it follows, That a double Degree of the fame Force will produce a double Degree of Motion; and but are For to change its Direction, andofitfelf to NA a three-fold Degree of the fame Force, a ce-fold Degree of the fame Motion; and “oon: And this Motion muft of Neceffity Proceed in the fame Direétion as that of the Force moving, fince the Motion is caus’d only y d becaufe by the former Law, Boch are in Motion cannot change their ns of themfelves; fo that except their lter’d by fome new Force, the Bodi es muft proceed in the fame Direétion t of the moving Courfe. And if a nick Performances are. Now as the Things before-méntion’d muft very confiderably diminifh the Force commu- tual Motion, except the Force communicated. were greater than the Force generating, by fo much as to make amends for the Diminution made therein by all thefe Caufes; fo that the Motion imprefs’d may never return undiminifh’d to the fir Mover: But that being con- trary to this Law, it is evident, that the Motion muft decreafe, till at laft it ftops, and fo of confequence, in the prefent State of Things, there cannot be any perpetual Motion. As to the Third Law, That Repulfe and Reaétion is always equal to Impulfe or Action, &c. To illuftrate this, confider, That whatfoever preffes or draws another, is as muchprefs’d or drawn by that other. If a Stone be prefs’d by the Finger, the Finger is prefs’d by the Stone again. If an Anvil be ftruck with a Hammer, the Hammer is ftruck by the Anvil with equal Force. If a Horfe draw a Stone 5 forward |
