83 BOOK II. Attraction and Gravity considered CHAP. I. Attraction inquired into, from the writings of Sir Isaac Newton, and the most eminent of his followers. I Nthe former part of this Treatise, I have made it appear, that the only rational and intelligible philosophy is that which attributes all motion to the action of matter upon matter; or, which is the same thing, that maintains an agency of material and secondary causes, under the direction of God, the moral governor of the world, and the supreme cause of all things. To such a philosophy as this, I have attempted to clear the way, by removing all the principal objections of our modern learned men and if the supposed evidence for a vacuum, depending upon the famous theory of resistances, which gained so much credit with Mr. Cotes, and many others, as to be unhappily mistaken for a demonstration; if this, I say, has been obviated to the satisfaction of the learned reader, what remains to be done will rather be a work of ease and amusement, than of difficult and doubtful disputation. For, if the notion of a vacuum be unsupported, and false in itself, nothing that is advanced in the mathematical philosophy, relating to physical causes, can possibly be right. Where that philosophy has mistaken or misrepresented the nature of these causes, it will be found inconsistent either with itself or with nature, and most probably with both so that to detect the falsehood of it, we shall have nothing to do, but to compare it with itself, and with those notions of the natural world, with which our senses and experience will furnish us. In this disquisition, we shall have in review before us, a great variety of useful and curious experiments, which cannot fail of giving some entertainment, to a mind that hath bestowed any of its attention upon such subjects. As As my concern at present is barely with physical causes, no reader can be so absurd as to suspect, that I am aiming at the demolition of all that is now called by the name of natural philosophy, without doing me a manifest injustice, and betraying his own want of knowledge. The doctrine of unmechanical causes, though the forwardnefs and indiscretion of some adventurers may have loaded it with a much greater weight than it is able to bear, does yet make but an inconsiderable part of the established philosophy; and if it should hereafter give place to some more natural account of things, the remaining parts will always retain their present value. Such a work as that of professor S' Gravesande, will deserve the admiration of the ingenious, so long as the world lasts; and that man must have but an indifferent relish for the sciences, who is not greatly delighted with the discoveries and improvements he may there meet with, in mechanics, optics, and astronomy. I speak this in much sincerity and it is intended to obviate any prejudices that might be raised against my design, either wilfully or by mistake. To give offence, is no part of my design; and I am unwilling, that any well G 3 well-designing person should think me to be possessed by a spirit of detraction, while I am conscious to myself it is far from me, and that I write upon much higher motives. I am encouraged therefore to hope for the attention at least, if not the favour, of all candid men and lovers of physical truth, while I inquire into the sense and merit of those causes, by which the Author of nature is now supposed to direct the natural world. First then, let us inquire, what kind of force or agency Sir Isaac Newton and his followers would have us understand by the terms attraction and repulsion. That attraction hath been called in for the explication of natural appearances, both great and small, every person must know, who has either heard or read any course of physical lectures delivered in English within this last century: it is looked upon as a principle, not to be approached without a degree of reverence, because the great Sir Isaac Newton thought proper to make use of it but if the word should have no fixed meaning, and should itself want an explication, it will explain nothing at all; it will be a word without an idea: and if we apply it to any particular case, we shall explain, as |