Matter and Motion* 1 7 



sensible distances. The first is called 

 the attraction of gravity, or, by mathe- 

 maticians, the centripetal force. 



This is the species of attraction whose 

 laws we have endeavoured to elucidate. 

 It is one of the most universal principles 

 In nature. We see and feel it operate in 

 bodies near the earth, and find by obser- 

 vation that the same power (i. e. a power 

 which acts in the same manner, and by 

 the same rules, viz. always proportionally 

 to the quantities of mattter, and inverse- 

 ly as the squares of the distances) does al- 

 so obtain in the moon, and the other plan- 

 ets, both primary and secondary, as well 

 as in the comets ; and even that this is 

 the very power by which they are all re- 

 tained in their orbits. This mighty prin- 

 ciple fornixS the earth into a round and 

 dense ball, holds every thing animate and 

 inanimate to its surface, and makes its 

 whole surface its general top. 



.From this attraction arises all the mo- 

 tion, and consequently all the mutation, 

 in the great world. By this heavy bodies 

 descend, and light ones ascend ; by this 

 projectiles are directed, vapours and ex- 

 halations rise, and rains fall -, by this 

 B 



