CONTENTS. 



Objirvation here on Earth, but it was inferred from the Dcfcent of the Moon The 



Theory of Gravitation in this Way generalized by Sir Ifaac, and its Law difcovered 

 —How the Theory of Gravitation, thus made general, is to be applied to the Planets — 

 The Motion of the Planets fuppofed by Sir Ifaac to be compounded, as he fuppofed 

 that of ProjecTi!es to be — The two Motions are, the one in the Line of Proje£tion, the 

 other in the Line of Gravitation — The Motion of the Planets not actually combined, but 

 only fuppofed to be fo for the Sake of Demonftration — A fimple uncompounded Motion 

 of the Planets is, by its Nature, poflible — If fo, all the Properties of the Motion arc 

 from thence deducible, though we may not be able to make the Dedudlion — Better to 

 acknowledge our Ignorance, than makeftrange and improbable Suppofuions — Our Ig- 

 norance muft be acknowledged in many other Things, of which we can make no Syflem 

 — But Sir Ifaac has made a Syftem of Aftronomy — This Syftem to be fupported with- 

 out the aftual Compofition of the Planetary Motion — The Hypothefis of fuch aCom- 

 pofition fufficient — This Hypothefis moft natural— It is according to the Method of 

 Science, and particularly according to Euclid's Method — If the Hypothefis of a Cen- 

 tripetal Force be admitted, the Hypothefis of a Projectile Force in the Line of the Tan- 

 gent abfolutely necefTary — The neceflary Conne£fie» betwixt thefe two Motions, and 

 their Dependency upon one another — The one being given, therefore the other is given — 

 The Moving Force in the Line of Projeflion is fhewn to have a relation to the Diftancc 

 from the Centre, as well as the Centripetal Motion — What that Relation is — The 

 Dedudion from any Hypothefis, if that Hypothefis be granted, as certain from the 

 Reality — Example of the like Deduftion from an Hypothefis not fo obvious and na- 

 tural, in the Cafe of the Compofition of Alotion — From that Example the Argument of 

 the Newtonians anfwered, that the fame Fjff'e^ muft be always produced by the fame 

 Caufe. Page 405 



CHAP. VII. 



The Advantage of thus Amplifying the AJlronomy of Sir Ifaac Newton — Firji, It difin- 

 cumbers the Syftem of the Hypothefis of the Planets being moved by Bodily Impulfe— 

 The Confequences of fuch an Hypothefis — ido. Of the Notion of a Perpetuity of 

 Motion begun by Bodily Impulfe— 2,tio, Of Body attrafling or impelling Body at a Dif- 

 tance — ^to. Of the Compofition of the Planetary Motion — Such a Compofition irrccon- 

 cileable with the Simplicity of Nature — ^to. Of the Hypothefis of the Planets all fall- 

 ing into their Centres, if their Motions were to be flopped — La/lly, Of a Centrifugal 

 Forte fuppofed in the Planetary Motion — The Confequence of this Hypothefis down- 

 right Alaterialifm — Inapplicable to the Motion of the Planets, whether that Alotion be 

 by Alind or Body — The Centrifugal Force of the Stone and Sling explained— The Ori~ 

 ^in of the Notion of a Centrifugal Force. p. 428 



CHAP. 



