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fixed in the centre of the vortex ? But if this be sup- CHAP.

II. posed, his whole hypothesis is lost; for then the sun and stars must be opaque, and not luminous bodies. But Des Cartes hath found out a notable invention to send them far enough from the centre; which is, That N. 89. they move in the way between the poles towards the middle of the heaven in a right line, and there are gathered into little masses ; some from the north, and others from the south. But when they are in the body of the sun N. 91. or a star, then they make those spots which hinder "-9 their light, and are thrown off like a thick scum from heated liquors. But when he assigns the reason of gravity, he saith, It comes from hence, that those par- Id. Princip.

part. ir. ticles which have a quicker motion press down those n. 43. which are not so fit for it, and by that means they get nearer to the centre. How comes it then to be so much otherwise in these parts of the third element? How N. 25. come they not to be pressed down in the same vortex towards the centre ? Especially when himself there saith, That the particles of the first element have more power to depress the earthy particles than of the second, because they have more agitation ; and here he speaks of the motion within the vortex: so that, according to his principles, the matter of the third element ought to subside and be near the centre, being least apt for motion. But this would overthrow his whole theory about the sun and stars, and about light, and the spots of the sun, and of magnetic particles, &c. so that these particles of the third element must be disposed of as he thinks fit, lest they put all out of order. And it is strange he should parallel the scum made by the fermenting of liquors, with the natural motion of the matter of his elements. And if this principle were true, that the matter of the third element might get above, and leave the thinner and more subtle matter



BOOK nearest the centre, I do not see how the earth could be

- habitable ; for then we could breathe nothing but thin,

and ethereal air, which we could not bear: as appears Acosta of by the famous instance of Acosta, who speaks by his the Indies, 1. iii.c.9. own sad experience, as well as of others, that he was Boyle's Éx-in periments in great danger of his life, by going over one of the Air, p. highest mountains of Peru. From whence it is ob

served, that the most subtle air is too thin for respiration. But how comes it to pass, according to these principles, that the heavier part of the air is most to

wards the centre, and the lighter ascends highest ? For Cart. Prin- air, according to Des Cartes, is a congeries of the parcip. part. iv. n. 45.

'ticles of the third element, very thin and disjoined; and yet we find this come nearer the centre, according to its gravity, and the lighter air goes higher, and hath very different effects on men's bodies, though the motion of it be not strong nor violent. For Acosta saith, That air which is so fatal to passengers on those mountains of Peru, (which are so high, that he saith, the Alps and Pyrenees were but as ordinary houses to lofty towers,) is so still, that it is but as a small breath, neither strong nor violent, and yet it pierces so, that it often kills men without feeling, and makes their hands and toes drop off; as he affirms from his own knowledge.

From whence it appears to be a mere fetch in Des Cartes, to keep these particles of his third element from being nearer to the centre, although they are more weighty and indisposed to motion than others are.

But his whole hypothesis is overturned concerning the celestial bodies, if there be a principle of gravitation in matter, which makes a natural tendency towards the centre, according to the quantity and distance of it. The opinion of Des Cartes's great skill in geometry hath gone much farther towards persuading the world


of the truth of his theory, than any evidences that ap- Chap. peared in his principles themselves; for men who are_11. not deeply skilled in those matters, are very apt to be swayed by the authority of those that are. But, as it falls out in this case, we have this theory of gravitation fully demonstrated by a very learned and judicious Is. Newton

Philosoph. mathematician of our own, to whom I refer the reader, Natural. who hath given a mathematical account of the celestial bodies, not only of the sun and stars, but of comets, and the moon, from the principle of gravitation ; not inherent and essential to matter, but by a force given and directed by Divine power and wisdom: which being granted, we have no reason to be displeased with the clearest account which can be given, in a mathematical manner, of the chief phænomena of the universe. And the same person saith, He hath many Præfat. reasons to suspect that the rest may depend upon some secret powers, by which the particles of matter do either cohere or fly from each other; for want of the knowledge whereof, philosophers have hitherto blundered in natural philosophy. But we proceed in Des Cartes's account of his celestial vortices.

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