Chap. i. PHILOSOPHICAL DISCOVERIES. 295

B O O K IV.

7 'he effeEls of the general power of gravity deduced

synthetically .

C H A P. I.

Of the centre os the solar syslem.

1 . I R Jsaac Newton having established the general prin-ciple of the gravitation of the particles of matter,Lj and having determined the chief powers that act in thelystem, viz. those which tend to the Sun^ Jupiter^ Saturn ,and the Earth ; and having found that the celestial motionsare performed in free spaces, where the resistance is insensible ;he has now prepared the way for proceeding synthetically inhis account of the system of the world, and enquiring into thevarious effects that arise from a power so evidently established.Any general principle ascertained in nature is a great acqui-sition to philosophy, especially when the variations of thispower, with its direction and force, are clearly determined ;and the fertility of this principle will appear from the variousphænomena resolved by it synthetically , of which we are nowto treat. Sir Isaac Newton begins with enquiring into thecentre of the system. The Pythagoreans ascribed this place tothe centre of the .fun, the followers of Arifiotle and Ptolemy tothe earth. But Sir Isaac ^ having found that these gravitate to-wards each other and towards all the other bodies in the system,* neither