280 



decree of their gravitation. For were the gravity of a 

 body but the half of what it is now, that body would re- 

 act but half as much as it does ; and of course, were all 

 its gravitation to cease, it would iiot re-act at all. 



Again ; it is supposed, gravitation is twenty-three 

 times greater on the surface of the sun than on the sur- 

 face of the earth. Hence a body which weighs one 

 pound here, would there weigh three and twenty. Con- 

 sequently without any addition of matter, it would re- 

 act twenty three times more than it does here. There- 

 fore this re-actiori, supposed an absolute law of matter, 

 is only a circumstance depending on the relative law of 

 gravitation. 



13. Come we now to the doctrine of centripetal and 

 centrifugal forces. 



In another age it will be iuatter of universal wonder, 

 that one of the most profound mathematicians in the 

 world should assume two powers for circulating the pla- 

 nets, and even circulale the quantities of matter thereby 

 from the proportions wherein they must act in produ- 

 cing and maintaining the circuits of the moving stars : 

 while it is demonstrable to common sense, from the ad- 

 mitted nature of these two powers, that it is absolutely 

 impossible they can support one single rotation of an. orb; 



Gravitation is allowed by all to be a constant power 

 in bodies, which cannot be altered but by change of 

 distance. It cannot be suspended ; for though its effect 

 may be resisted, yet its tendency thereto is invariable. 

 It is therefore a proper undestroyabie power, uninter- 

 ruptedly acting in and upon bodies. 



The ItAvs assigned to projection are just the reverse. 

 When- any proportion of the quantity of projectile motion 

 is destroyed, either by direct Opposition, or by change 

 of its direction, it exerts no nisus to recover its first quan- 

 tity of motion. Consequently as long as any power, 

 such as that of gravitation, is bending the direction of 

 projection, it is a contiuual resistance of the power of 



