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the Syſtem of the World. For by the propoſitions mathematically demonſtrated in the firſt book, we there derive from the celeſtial phenomena the forces of Gravity with which bodies tend to the Sun and the several Planets. Then, from theſe forces, by other propoſitions which are alſo mathematical, we deduce the motions of the Planets, the Comets, the Moon, and the Sea. I wiſh we could derive the reſt of the phenomena of Nature by the same kind of reaſoning from mechanical principles. For I am induced by many reaſons to ſuſpect that they may all depend upon certain forces by which the particles of bodies, by ſome cauſes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown, Philoſophers have hitherto attempted the search of Nature in vain. But I hope the principles here laid down will afford ſome light either to that, or ſome truer, method of Philoſophy.
In the publication of this Work, the moſt acute and universally learned Mr. Edmund Halley not only aſſiſted me with his pains in correcting the preſs and taking care of the ſchemes, but it was to
