[ i8 ] 



Hence therefore it appears, that Newton rightly fuppofes 

 the preceffion of the nodes of a rigid, detached annulus, and of 

 a folitary moon to be equal ; though the principles on which 

 he argvies are infufBcient, becaufe he did not, as was neceffary, 

 confider the opei'ation of the counterading centrifugal force. 

 And when he comes to apply this dedudlion, his concluion 

 is erroneous, becaufe, omitting the confideration of the centri- 

 fugal force as before, he conceived, that the motion of a folitary 

 annulus and of a ring attached to a fphere were produced 

 by the fame efficient force ; whereas in this latter cafe, the cen- 

 trifugal force of the annulus vanifhes, and therefore the whole 

 force of the fun becomes efficient-, that is, the efficient force 

 in the cafe of a ring adhering to the equator of a globe, is 

 double the efficient force in the cafe of a folitary ring; and 

 therefore the quantity of the preceffion, eftimated on this falfe 

 hypothefis, comes out too little by jull one half. 



Bishop Horsely, in his commentary on this problem, ob- 

 ferves, that if this affertion, to wit, that the motion of the 

 nodes of a rigid annulus and of a folitary moon are the fame, 

 be true, he cannot fee how the quantity of the preceffion of the 

 equinoxes can be different from that which is affi-ned by 

 Newton ; but he refrains from any ablolute decifion : " Si hoc 

 " vere didum fit (fays he) f^ quod par eft ratio nodorum 

 " annuii lunarum terram ambientis, five lunx illse fe mutuo 

 " contingant, five liquefcant, & in annulum continuum for- 



" mentur. 



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