Chap. i. PHILOSOPHICAL DISCOVERIES.

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It is not therefore the business of philosophy, in our presentsituation in the universe, to attempt to take in at once, in oneview, the whole scheme of nature ; but to extend, with greatcare and circumspection, our knowledge, by just steps, fromfenstble things, as far as our observations or reasonings fromthem will carry us, in our enquiries concerning either thegreater motions and operations of nature, or her more subtileand hidden works. In this way Sir Isaac Newton proceededin his discoveries : he established his account of the system ofthe world upon the best astronomical observations, on the onehand; and performed, himself, on the other, with the greatestaddress, the experiments by which he was enabled to pry intothe more secret operations of nature, amongst the minute par-ticles of matter. On either side he has extended our viewsvery far, and has left valuable hints and intimations of whatyet lies involved in obscurity.

For those purposes he has given us two incomparable treatises,the most perfect in their kind philosophy has to boast of; hisMathematical Principles of Natural Philosophy, and his Trea-tise of Optics . In the first, he describes the system of theworld, and demonstrates the powers which govern the celestialmotions, and produce their mutual influences. These are ex-tended from the centre of the fun to the utmost altitude of thehighest comet, and probably to the farthest limits of the uni-verse. Nor are these new or abstruse principles, like to thosewhich never had a being but in the imagination of philo-sophers, but the fame which are most familiar to mankind,and in common use, farther extended and more accurately de-fined. In the second, he treats of light, which, tho’ the mostpotent agent in nature, that is sensible to us, acts only at the leastdistances. His admirable discoveries, on this subject, led him

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