1x6 of the Newtonian system,

times. This is a law of nature which had be-fore been discovered by Kepler from observation.The supposition, therefore, that the moon isunder the influence of such a force, is confirmedboth by science and experience; and every im-provement which has since been made in thetheory of her motion, has been derived fromthese principles.

It was before discovered by Galileo, that abody projected through the air, with any forcewhatever, would describe a curve which is calleda parabola, if the medium had no resistance.But Newton, whose genius soared above pettydistinctions, extended this problem and made itmore general. He no longer considered thefalling body as having a limited distance; butregarding only the attraction of the earth, andthe lateral uniform velocity of the projectile, heproved that it would move round the earth inan elliptical orbit, having the center of the earthfor one of its foci. The falling body, in thisexample, may be considered as a moon, movinground the earth, or as one of the satellites ofJupiter or Saturn, moving round those planets;the circumstances, in either cafe, being exactlythe same.

That the moon is actually under the influenceof gravity,- and moves by means of that force,may be shewn as follows: Sir Isaac Newton hasdemonstrated, that if the moon was deprived of

r the