114 of the Newtonian system",

aU bodies, and gives them' a tendency to salstowards the center of the earth: and that thisforce, whatever it may be, acts most stronglyupon the earth’s surface ; being subject, eitherin ascending or descending, to continual dimi-nution. How then does it appear, that gravity,or weight, is an inherent and necessary propertyof body ? It increases or diminiflies perpetuallyaccording to a certain proportion of the distancefrom the center; but what is permanent andessential admits not of such different and variousmutations. You fee then that weight is not sonecessarily' connected with matter, as, from aflight consideration of the subject, you wouldnaturally imagine.

These were probably Newton’s first reflectionsupon the nature of falling bodies. We shall nowfee what use he made of them, in applying themto the celestial motions. He soon perceived thatthe force of gravity was not confined to thesurface of our globe, being found to act alike atthe bottom of the lowest vallies, and at the topsof the highest mountains. Perhaps, said he, itextends as far as the moon, and is the means ofretaining her in her orbit. The conjecture washappy; and, by the following application of it,he was presently enabled to prove its validity.Imagine the moon, at the first moment ofits creation, to have been projected forwards,with a certain velocity, in a straight-lined direc-tion j