A HISTORY OF SCIENCE 



"CoR. 5. The power of gravity is of a different 

 nature from the power of magnetism; for the mag- 

 netic attraction is not as the matter attracted. Some 

 bodies are attracted more by the magnet ; others less ; 

 most bodies not at all. The power of magnetism in 

 one and the same body may be increased and dimin- 

 ished; and is sometimes far stronger, for the quantity 

 of matter, than the power of gravity; and in reced- 

 ing from the magnet decreases not in the duplicate, 

 but almost in the triplicate proportion of the dis- 

 tance, as nearly as I could judge from some rude 

 observations. 



" PROPOSITION VII., THEOREM VII. 



" That there is a power of gravity tending to all bodies, 

 proportional to the several quantities of matter which they 

 contain. 



" That all the planets mutually gravitate one towards 

 another we have proved before; as well as that the 

 force of gravity towards every one of them considered 

 apart, is reciprocally as the square of the distance of 

 places from the centre of the planet. And thence it 

 follows, that the gravity tending towards all the 

 planets is proportional to the matter which they 

 contain. 



" Moreover, since all the parts of any planet A grav- 

 itates towards any other planet B ; and the gravity of 

 every part is to the gravity of the whole as the matter 

 of the part is to the matter of the whole ; and to every 

 action corresponds a reaction; therefore the planet B 

 will, on the other hand, gravitate towards all the 



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