A voyage to the world of Cartesius written originally in French, translated into English by T. Taylor, of Magdalen Colledge in Oxford.

The second Argument.

In order to comprehend this Difficulty, we must suppose with M. Descartes, that all the fix'd Stars are not contain'd in the Circumfe∣rence of the same Sphere, nor equally distant from the Centre of the visible World. That some are sunk deeper in the vast Spaces of the Firmament, others dive nearer to the Centre of the World. We must also remember that each of them have their proper Vortex, of which they are themselves the Centre, and that those Vortexes are so many different Spheres rang'd above, below, and on the sides of one another. As for Instance, we must conceive the Vortex of the Sun, in which floats our Earth, with the other Planets, as a fluid Sphere, surrounded with many others like it, which it touches in several points of its external Superficies, just as a Bowl incompass'd on every side with other Bowls touches them all in different parts of its Circumference.

[illustration]

S The Vortex of the Sun.

In the third place we must recollect M. Des∣cartes's manner of explaining Light, which con∣sists in that endeavour the Matter of the first Ele∣ment makes at the Centre of the Vortex, to get farther from the Centre, whence, pressing on the Celestial Matter, or the second Element in all imaginable Points, that impulse and that

pressure light on all the Lines that reach to the Circumference of the Vortex; some of which necessarily falling on our Eye, when directed to∣wards the Star or Sun, make such a Pression and Vibration there, as determine our Soul to that Perception which goes by the Name of Vision.

[illustration]

This Figure will easily explain it, where the little Points at the Centre of the Circle repre∣sent the Matter of the first Element, or the Body of the Star. The Lines drawn out to the Cir∣cumference, represent the Celestial Matter, whose Rays concenter in the Eye plac'd at the Circumference of the Vortex.

We presume to affirm, That in this Situ∣ation of the Vortexes, we who are in that of the Sun should not be able to see the Stars, Monsieur Descartes's Principles suppo∣sed.

Let us add to the preceding Figure, four other Vortexes, supposing them the Vortexes of four Stars that are nearest to that of the Sun.

[illustration]

Let the Eye, plac'd in the other Figure to be∣hold the Sun, be turn'd towards one of these Vortexes, to behold, for Instance, the Star B. wee'l demonstrate by M. Descartes's Principles, that it is not possible to be seen.

The Demonstration.

The Eye can no ways obtain the sight of the Star B, but by means of the Rays or Lines of the Celestial Matter, push'd by that Impulse the Star B. causes in strugling to get from the Centre of its Vortex, which Impulse is communicated to the Eye, by its pressure and concussion of the

Strings of the Optick Nerve. But this is impossi∣ble, supposing the Eye placed in the Vortex of the Sun. And thus we prove it.

That Impulse must be communicated to the Eye by one of these two ways; either immedi∣ately by a Ray, or Line of Matter drawn from the Vortex of the Star and Terminating in the Eye; or mediately by a Line of the Solary Vor∣tex, in which the Eye is plac'd, retorted on the Eye by the Vortex of the Star. As if the Line B, A. of the Stellary Vortex, should retort upon the Eye the Line A. C. of the Solary Vortex. For it is impossible to conceive the Star should cause any Impression on the Eye but by one of these two ways: But neither the one nor the other will serve our turn.

Not the first, because the Vortexes, according to M. Descartes, have each their circumscrib'd and separate Sphere of activity, and a Motion altogether different. Insomuch that the Lines of the one are never blended with the Lines of the other: But end severally at the Circumfe∣rence of their own Vortex; and if once that Communication or rather Confusion should be admitted, all would speedily return, into that confus'd and disorderly Chaos, from which M. Descartes will have his World extracted, by the only Laws of Motion; and farther, since there is no point in the Vortex of the Sun, wherein we cannot see the Star, the Matter of the Stars Vortex must necessarily possess all the Space of the Vortex of the Sun; than which no∣thing can be more absurd.

There remains the second way, which will prove as useless as the former to M. Descartes, proceeding on his Principles; forasmuch as with

him the Vortexes, though unequal perhaps in Big∣ness, must be ever equally matcht in Power and Efficacy. For, says he, unless there was that equality betwixt them, they would infallibly destroy each other. Now that equality pro∣ceeds from this, that the Star of a Vortex mov∣ing still uniformly round, presses the Matter of its Sphere towards the Circumference, and a∣gainst the neighbouring Vortexes precisely with so much force as the Stars of the other Vortexes press the Matter of their Sphere in opposition to it. Which is the reason, according to him, that they always maintain their Ground against each other: But from hence also we manifestly conclude, That the Matter of one Vortex is in∣capable of repelling that of another, or causing it to recoil towards the Centre, from whence it struggles and contends to move with all its force, reliev'd also with the whole Posse of the Star that pushes it. Therefore that Effort, the Mat∣ter of a Star makes to get farther off the Cen∣tre, can make no Impression on our Eye, so long as it is in the Solary Vortex; since the com∣munication of that Impression is utterly pre∣vented by the Matter of the Solary Vortex, that with all its might and main resists it, and con∣sequently hinders that pressure on the Organ, which is the only cause of Sight. To explain our selves by a comparison much like that so of∣ten made use of by M. Descartes. Let us sup∣pose a blind Man, whose Hand stirring neither one way nor other, touches the end of a Staff. Let us again suppose his Hand so capacitated and dispos'd, that for the Perception of the Staff it is not sufficient that it be immediately con∣tiguous to it, but that there be besides that Con∣tact,

some pressure of the Staff against the Hand. Let us in the third place suppose another Hand, pushing it strongly against that of the blind Man. Lastly, let us suppose that a third Person, holding the Staff in the middle, indea∣vours to withhold it from the Hand of the blind Man, and that this indeavour be exactly equal to that the second Hand makes the contrary way. In this case the Staff will advance neither one way nor other, it will make no pressure on the Hand of the blind Man, and consequently, according to the first part of the Supposition, he will not be sensible of it.

[illustration]

Let us apply this to the Case in Dispute: We will imagine a Line of Celestial Matter reach∣ing from the Eye to the Circumference of the Solary Vortex. The immediate Conjunction of that Line with the Eye is insufficient to produce

the sensation of Light, unless something more be added. That then which must be added, is an impulse and pressure of that Line against the Eye, which will determine it to see; and this is the Doctrin of M. Descartes. But now whence comes that pressure in the Hypothesis before us? It cannot proceed precisely from that Line of Celestial Matter, seeing it makes a directly con∣trary Attempt, to withdraw it self from the Eye towards the Circumference of the Solary Vortex. It must then, if at all, proceed from the Line of the neighbouring Star's Vortex, that reflects the aforesaid Line against the Eye. But this making as forcible an Attempt to get from, as that to press it on the Eye; it is plain, that Effort and Impulse can no more reach the Eye, than can the Effort of the Hand that pushes the Staff, arrive to the Hand of the blind Man; and that the Eye admits no pression from the Cele∣stial Matter requisite to cause the Perception of Sight: Like as the blind Man's Hand receives no Impression of the Staff, requisite to excite the Sense of Feeling, or to cause the Perception of the Staff; and consequently the Eye, plac'd in the Vortex of the Sun, will be as far from seeing the Star, as the blind Man from feeling the Staff.

But for a Confirmation of all this, we must remember, that in the Principles of Descartes, not only what interrupts that Effort and that Pressure, but also what ever weakens or curtails one or the other, consequently frustrates the effect of the luminous Object on the Eye; and thus it is that Philosopher explains the spots of the Sun, or those defailures of Light, that appear in several parts of the Convex of that

Luminary. For, according to him, the parts of the third Element, hookt and ingendred with each other on the Surface of the Sun, keep the Matter of the first Element, of which the Sun is made, from pushing the Celestial Matter to∣wards my Eye, with so much force as formerly: Which is the reason that the Lines of the Ce∣lestial Matter, which touch my Eye, and which we suppose extended to that Matter of the third Element flak'd upon the Body of the Sun, are no longer Rays of Light, that should represent to me that part of the Sun as bright as all the rest. So that the Light, which I perceive in all the Sun besides, causes me to perceive in that part of the Sun a defect of Light, which we call a Spot or Stain. Now it is evident that this Portion of Matter of the third Element, that only floats upon the Surface of the Sun, breaks the force, wherewith the Matter of the Sun pushes the Celestial Matter against my Eye, much less, than if a force equal to that of the Matter of the Sun stood determin'd, and fully bent against it, as it happens in this Case, where the Matter of the Solary Vortex with∣stands the Effort of the Star, and consequently hinders it from making any Impression on my Eye. And here let M. Descartes shuffle and cut, and make what stir he pleases to recover his Reader, by an Explication of Refractions made in the Rays of the Star, upon their passage through the Vortex of the Sun; his only Design is to lurk and secure himself in that Darkness and Obscurity with which he purposely benights the Question. Let him only tell us what he means by those Rays of the Star that arrive to the Earth athwart the Solary Vortex. But what

we have said will sufficiently evidence, how groundless and trifling will appear whatever shall be urg'd thereupon.

[illustration]

But if it be impossible to conceive the commu∣nication of the Effort and Impulsion of a Star, whose Vortex immediately borders on the Suns, what will become of the other Stars, whose Vortexes are infinitely distant from that of the Sun, and which must make a sensible impression on our Eye across a great many Vortexes, whose Matter is differently mov'd, and are all so many Obstacles to that Communication? Doubtless, though all we have been urging amounted not to a Demonstration, in respect of the Stars situate near the Sun, it would infallibly, in respect of all the other. So that instead of those infinite Stars, we see sparkling in the Firmament by night, we should not discover an hundred with the best Perspectives.

What now if we should add it were impossi∣ble to see the Sun it self? Yet this may be prov'd by the same Principles; for no more is requisite for this, than that the Earth should have a particular Vortex, whose Motion should equalize and resist that of the Celestial Matter which the Sun pushes towards our Eyes. But so much is true, according to Descartes himself; for he expresly teaches, That the Earth hath a particular Vortex, whose Matter struggles as much as possible from the Centre. That effort is contrary to the effort of the Matter of the Solary Vortex on that side which is inlightned by the Sun. That effort is equal to that of the Matter of the Sun: Otherwise the Vortex of the Earth would run to ruin. Therefore the Im∣pression of the Sun cannot be communicated to our Eye.

What shall we say of the Planets and Comets, which are seen by the help only of the reflected Rays of the Sun, and that consequently are not so strong as if they were direct? If the Earth's Vortex, arguing on Descartes's Principles, is able to obstruct the latter, how much easier is it to ob∣struct the former, and hinders us from seeing all those Stars?

All this seem'd very difficult; and before we turn'd Cartesians, we had a mind to be satisfy'd thereupon. But one thing yet remains, and perhaps something better than ordinary, upon the particular Vortex of the Earth, which is Matter of a third Difficulty in us.