A voyage to the world of Cartesius written originally in French, and now translated into English.

The Demonstration.

Either the particular Vortex attributed to the Earth is the same with what it had, whilst yet it was a Star; or else it is a new one, made since the Destruction of the other. We maintain that neither the one nor the other can be said. Therefore it can have none at all.

It cannot be that it formerly had. For 'tis M. Descartes's Position that a Star degenerates into a Planet or a Comet, by the loss only of its Vortex. According to him, a Vortex is pre∣serv'd meerly by its Matter, having as much Motion and Resistance as the Matter of those a∣bout it; and its Matter loses that equality of Motion and Resistance, when the Star at the Centre can no longer communicate so much by

reason of the Scum that covers it. Now the Earth is a Star not only covered with a Scum or Dross, but with several thick Crusts of an un∣accountable Depth. So that it was incapable of preserving its Vortex, which must have been quite and clean destroy'd, and swallow'd up (as M. Descartes's Latin Word expresses it) by that of the Sun. Let us see then if the Earth was able to procure a new one since its removal near the Sun.

[illustration]

S the Sun. T the Earth. A B C D the little Vortex of the Earth. N A C Z the great Orb wherein the Earth is carried round the Sun.

M. Descartes takes this same course to com∣municate hi•• Thoughts: He makes this Figure which represents the Vortex of the Sun, in which the Centre S is the Sun it self. The little Circle or Ellipsis design'd with C. D. B. A. represents the

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Matter which carries the Planet round the Sun moves far swifter than the Planet. He ex∣plains, I say, this Supposition by the Simily of a Boat falling down a River, which goes on much slower than the Water that flows under it: A plausible comparison at first sight, but that has nothing solid in it: Since the reason of the Boats tardy Motion in respect of the Water that for∣ces it along, is wanting in the Planet, steer'd in the midst of the Celestial Matter. The reason is this, that part of the Boat, which stands a∣bove the Water, meets with the opposition of the Air, which bends its course differently from the Water, and consequently resists the Motion wherewith the Water influences the Boat. And the greater that resistance is, as in a contrary Wind, the slower is the Motion of the Boat, in comparison with that of the Water. And the less the resistance is, as when the Wind stands fair, the swifter is the motion of the Boat: But this is not to be found in the Planet, plung'd in the midst of the Celestial Matter: It pre∣serves intirely all that Motion the Celestial Mat∣ter can impress upon it, free from all external Opposition. Besides, being of it self indiffe∣rent to Motion, or to rest, to such or such a de∣gree of Motion, or this or that Determination, it offers no resistance, as M. Descartes himself speaks to the Matter of the Heaven.

He gives next the reason of that inequality of Motion of the Celestial Matter, and of the Planet carried by it; which is (says he) that though such little Bodies, as are the insensible parts of the Celestial Matter, conspiring all together to act confederately against a great one, may be as prevalent as that; notwithstanding they can ne∣ver

move it in all respects so swift, as they are mov'd themselves; 'cause though they are uni∣ted in some of their Motions which they com∣municate unto it, they infallibly disagree in o∣thers which they cannot communicate. Either we are mistaken, or this is a meer Gipsy-talk, at least in relation to the Business we are upon; and one of these Slights of Hand, we have observ'd M. Descartes from time to time to make use of, designedly to blind his Reader, and to conceal from him the Lameness and Imperfection of a Conclusion necessary to his System; which he is well aware of, but is unwilling any one else should see. 'Tis but bringing some pretty sort of Comparison that may prepare the Mind, and sooth and tame (if we may so speak) the Ima∣gination of his Reader, though commonly it never comes up to the stress of the Difficulty; and then clapping on it for a Confirmation some abstracted Reason, that few either can or will take pains to understand, and the Business is done; fore-seeing that being half-gain'd al∣ready by the Comparison, they will easily sur∣render themselves to the least appearance of Truth, which he shall give them a glimpse of in his reason, that often is a meer fallacy at bottom. And as for this before us: What matters it, though the little Bodies, that drive on a great one, should have several Motions? What tho' they do not communicate all these several Moti∣ons, provided they have still Strength enough to force it on, that the Body makes no resistance, that they all combine, as we suppose, with M. Descartes, to communicate the Motion requisite, and that we conceive them all pressing on its Surface, so as to push it towards the place where

they are push'd themselves? For certainly in all these Circumstances, we must conceive it going at as great a rate as they.

And yet from a Principle so weakly establisht as this, he concludes, That the Celestial Matter ought to move the Planet round its own Centre, and constitute a little Heaven about it, to turn at the same time as the great one. But not now to controvert that Supposition, as poorly prov'd as it is, let us persue him in his reasoning; and to see if it be good, let us imagine the Earth T. as it were suspended in a Void, and let us fancy a Circle of Celestial Matter as thick as the Diame∣ter of the Earth, that viol••ntly rushing like a Torrent, carries it suddenly away: But as we suppose this Torrent to be swifter than the Earth, methinks without having puzzled our Heads much with the Rules of the Determinations of Motion, we might readily conceive it, upon its violent dashing against the Earth, to be immedi∣ately divided in two Parts or Arms, whereof one should run above, the other below it; and whether we conceive this Stream of an equal, or a greater depth, than the Diameter of the Earth, it would diffuse it self round its Surface, above, below, and on every side. Whence it follows, that it would impress no Motion on it about its own Centre, but would moreover deprive it of that Motion if it had one; all the Lines of the Torrent counterpoizing one another, and resist∣ing the Determinations they should meet with in the Earth contrary to their own.

Here ought to be the foregoing Figure, p. 278.

Now methinks in explaining these things thus, it is not a bare Similitude that we offer, but a

perfect Idea of that which ought to happen in the Motion of the Celestial Matter, wherein the Earth is carried round the Sun,

Wherefore then will Descartes have the Cele∣stial Matter that carries the Earth, and insists a∣gainst its Superficies towards A, making greater haste than the Earth, bend its whole Current from A to B, not suffering half of it to run from A to D? For 'tis impossible for things to be, or to be conceiv'd otherwise. But if it ought to fall out thus, as questionless it ought, the Earth no longer-has a Vortex; since the Matter flowing from A to D, prevents that which flows from A to B from returning by C. D. Nothing can be more plain and evident than this Demonstration.

But let us suppose per impossible, that the Mat∣ter when arriv'd at A, should entirely make a double, to run towards B. Would it make a Vortex? No by no means. For advancing from B. to C. and arriving at C. it ought to deviate from the Centre of its Motion, and continue its Progress towards Z. The Reason given for it in the Principles of Descartes, is, That▪ this is the very place in all the little Circle it had begun to describe, where it finds least resistance. First, because the Matter it meets in that same Point is already on its Motion towards Z. and freely re∣signs its place. Secondly, because that which is below it, that is to say betwixt D. and C. resists it, and hinders its Descent, being more weighty, according to M. Descartes. And thirdly, because the Circle C Z. is its natural place, according to the same Philosopher. It will flow therefore more to∣wards Z. than D. and consequently make no Vortex.

But let us farther suppose a Vortex made, and the Matter continuing its round, from A. to B.

from B. to C. and from C. to A. would this Vor∣tex last? Not at all. For we must suppose one of these three things: Either that it is stronger than the Vortex of the Sun, that is, its Matter has a stronger bent and tendency from its Centre, than the Matter of the Sun's Vortex has from his, or that it is weaker; or that they both are equal. If it is weaker it must be destroy'd by the Vortex of the Sun. If stronger it must ruin his. It re∣mains then that its Strength be equal with the Suns: And M. Descartes must unavoidably sup∣pose it: But how will he prove it to us, I say not by a Demonstration (we will not put him on so hard a Task) but how will he bring the least Conjecture to give this Supposition a pretence to probability? Cannot we on the other side pro∣duce several Reasons to destroy this Supposition? Cannot we shew, in case the Vortex of the Earth was as strong as that of the Sun, and the little Glo∣bules wrested themselves as forcibly from the Cen∣tre of their Vortex, that the Earth it self would appear a Sun▪ and so would Iupiter to boot? Since that which makes the Centre of a Vortex to us seem luminous, is only the vehement Motion of its Matter? Though Descartes says the Centre would be drain'd of all its Matter, might not we however, imitating the Stile of that Philosopher, compare the Vortex of the Sun quite from S. to D. to a vast Ocean, whose boystrous Tide swel∣ling against the Stream of a little River, by which we illustrate the Vortex of the Earth, obli∣ges it to fall back again, and adds a Determina∣tion to its Waters quite contrary to its former? But with Descartes for a Vortex to be destroy'd, and for the Matter of the Vortex to take the Mo∣tion and Determination of another, is one and

the same thing. Let M. Descartes but prove his Vortex of the Earth with the least part of the rea∣son we have brought against it, or by as natural a Comparison as we have us'd to demonstrate it a meer Chimera, and he need not fear to stand the Test, Sallies and Assaults, of the best of his Adversaries.

What now if we should fall to examining the Difficulties that may be gather'd from the little Planet in particular, I mean the Moon consider'd in the petty Vortex of the Earth? Should we probably find less Matter of Objection?

Here ought to be the foregoing Figure, p. 278.

We advance no more than this, that suppo∣sing the Moon when arriv'd at A. was carried on towards B. she ought to deviate from her Vortex in C. For first, That's the external Superficies of the little Vortex, as M. Descartes will not deny. Secondly, She Attempts to leave her Vortex, by his grand Principle of circular Motion. He pretends she cannot make her escape towards B. because the Matter of the Solary Vortex in that place is more light and active, and repels her towards the Centre. Nor can she, according to him, make downwards towards K. for that, says he, the Celestial Matter on that side is hea∣vier than the Moon, and equally opposes her Descent: But we say she will get out of her Cir∣cle at C. and continue her Progress toward Z. For being in C. she finds no resistance, since the Matter of C. Z. is that of her own Circle, which is already on its March, and willing to give up its place. Besides, being in that place, she actu∣ally makes an Attempt to get rid of the Centre

of her Motion, that is to say, of T. she therefore will accomplish her escape, since there is no Ob∣stacle in that as is found in the other Points; and being cast out of her Circle, she will be oblig'd to continue her Journy towards Z. by the Mat∣ter plac'd above, and below her in the Circle, for the self-same Reasons as are given by M. Des∣cartes.

Yet in spite of all this, it cannot be deny'd, but that M. Descartes had good reason to order his Suppositions of these things as he did. His System was too far advanc'd to think of stop∣ping at so small an Obstacle as a Moon. All the Grandee-Planets were plac'd severally, according to the Quality and Preeminence their Solidity had given them. Madam Luna too was seated in the Circle of the Earth. There was only one little Inconvenience in the case, which was, that she must necessarily take a turn about the Earth, and consequently must be sometimes in the Earths own Circle, and sometimes out of it. She must therefore have a little Vortex of her own. And this is the best, as also only reason that can be given for his making one on purpose: And setting this aside, the Laws of Staticks alone could never have prevail'd with his Frugality, to put it self to that extraordinary Ex∣pense.

We had not insisted so long upon this Article, had not we consider'd it as the capital Point in the Cartesian System; and as the Founda∣tion of that prodigious Edifice, which has been taken in our days by so many, for the compleatest Mastery of a Human Mind. Let us see the Importance of our Demonstration by the Corollaries drawn from it.