Archimedes Project

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in, by these poles, as much as it loses in its equatorial parts. And, by this means, it would be able to carry round with it those globules that are nearest, with the greater velocity; and the remoter, with less. And by this means, those globules, which are nearest the centre of the sun, must be smallest; because, were they greater, or equal, they would, by reason of their velocity, have a greater centrifugal force, and recede from the centre. If it should happen, that any of these sunlike bodies, in the centres of the several Vortices, should be so incrustated, and weakened, as to be carried about in the Vortex of the true sun; if it were of less solidity, or had less motion, than the globules towards the extremity of the solar Vortex, it would descend towards the sun, till it met with globules of the same solidity, and susceptible of the same degree of motion with itself; and thus, being fixed there, it would be for ever after carried about by the motion of the Vortex, without either approaching any nearer to the sun, or receding from it; and so would become a planet.

Supposing then all this; we are next to imagine, that our system was at first divided into several Vortices, in the centre of each of which was a lucid spherical body; and that some of these, being gradually incrustated, were swallowed up by others which were larger, and more powerful, till at length they were all destroyed, and swallowed up by the largest solar Vortex; except some few which were thrown off in right lines from one Vortex to another, and so become comets.

But this doctrine of Vortices is, at best, merely hypothetical. It does not pretend to shew by what laws and means the celestial motions are effected, so much as by what means they possibly might, in case it should have so pleased the Creator. But we have another principle which accounts for the same phenomena as well, nay, better than that of Vortices; and which we plainly find has an actual existence in the nature of things: and this is gravity, or the weight of bodies.

The Vortices, then, should be thrown out of philosophy, were it only that two different adequate causes of the same phenomena are inconsistent.

But there are other objections against them. For, 1°, if the bodies of the planets and comets be carried round the sun in Vortices, the bodies with the parts of the Vortex immediately investing them, must move with the same velocity, and in the same direction; and besides, they must have the same density, or the same vis inertiæ. But it is evident, that the planets and comets move in the very same parts of the heavens with different velocity, and in different directions. It follows, therefore, that those parts of the Vortex must revolve at the same time, in different directions, and with different velocities; since one velocity, and direction, will be required for the passage of the planets, and another for that of the comets.

2°, If it were granted, that several Vortices are contained in the same space, and do penetrate each other, and revolve with divers motions; since these motions must be conformable to those of the bodies, which are perfectly regular, and performed in conic sections; it may be asked, How they should have been preserved entire so many ages, and not disturbed and confounded by the adverse actions and shocks of so much matter as they must meet withal?

3°, The number of comets is very great, and their motions are perfectly regular, observing the same laws with the planets, and moving in orbits, that are exceedingly eccentric. Accordingly, they move every way, and towards all parts of the heavens, freely pervading the planetary regions, and going frequently contrary to the order of the signs; which would be impossible unless these Vortices were away.

4°, If the planets move round the sun in Vortices, those parts of the Vortices next the planets, we have already observed, would be equally dense with the planets themselves: consequently the vortical matter, contiguous to the perimeter of the earth's orbit, would be as dense as the earth itself: and that between the orbits of the earth and Saturn, must be as dense, or denser. For a Vortex cannot maintain itself, unless the more dense parts be in the centre, and the less dense towards the circumference: and since the periodical times of the planets are in sesquialterate ratio of their distances from the sun, the parts of the Vortex must be in the same ratio. Whence it follows, that the centrifugal forces of the parts will be reciprocally as the squares of the distances. Such, therefore, as are at a greater distance from the centre, will endeavour to recede from it with the less force. Accordingly, if they be less dense, they must give way to the greater force, by which the parts nearer the centre endeavour to rise. Thus, the more dense will rise, and the less dense descend; and thus there will be a change of places, till the whole fluid matter of the Vortex be so adjusted as that it may rest in equilibrio.

Thus will the greatest part of the Vortex without the earth's orbit, have a degree of density and inactivity, not less than that of the earth itself. Whence the comets must meet with a very great resistance, which is contrary to all appearances. Cotes, Præf. ad Newt. Princip. The doctrine of Vortices, Newton observes, labours under many difficulties: for a planet to describe areas proportional to the times, the periodical times of a Vortex should be in a duplicate ratio of their distances from the sun; and for the periodical time of the planets, to be in a sesquiplicate proportion of their distances from the sun, the periodical times of the parts of the Vortex should be in the same proportion of their distances: and, lastly, for the less Vortices about Jupiter, Saturn, and the other planets, to be preserved, and swim securely in the sun's Vortex, the periodical times of the sun's Vortex should be equal. None of which proportions are found to obtain in the revolutions of the sun and planets round their axes. Phil. Nat. Princ. Math. apud Schol. Gen. in Calce.

Besides, the planets, according to this hypothesis, being carried about the sun in ellipses, and having the sun in the focus of each figure, by lines drawn from themselves to the sun, they always describe areas proportionable to the times of their revolutions, which that author shews the parts of no Vortex can do. Schol. prop. ult. lib. ii. Princip.

Again, Dr. Keill proves, in his Examination of Burnet's Theory, that if the earth were carried in a Vortex, it would move faster in the proportion of three to