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CHAPTER II. 



THE INDUCTIVE EPOCH OF NEWTON. DISCOVERY 

 OF THE UNIVERSAL GRAVITATION OF MATTER, 

 ACCORDING TO THE LAW OF THE INVERSE SQUARE 

 OF THE DISTANCE. 



IN order that we may the more clearly consider 

 the bearing of this, the greatest scientific dis- 

 covery ever made, we shall resolve it into the par- 

 tial propositions of which it consists. Of these we 

 may enumerate five. The doctrine of universal gra- 

 vitation asserts, 



1. That the force by which the different planets 

 are attracted to the sun is in the inverse proportion 

 of the squares of their distances ; 



2. That the force by which the same planet is 

 attracted to the sun, in different parts of its orbit, is 

 also in the inverse proportion of the inverse squares 

 of the distances ; 



3. That the earth also exerts such a force on 

 the moon, and that this force is identical with the 

 force of gravity ; 



4. That bodies thus act on other bodies, besides 

 those which revolve round them; thus, that the sun 

 exerts such a force on the moon and satellites, and 

 that the planets exert such forces on one another; 



5. That this force, thus exerted by the general 



