PHYSICAL ASTRONOMY. 



plane of the equator, be called g 9 the force of 

 gravity at any distance r, from the centre, in 

 the same plane, will be 



MACLAURIN'S Fluxions, 659. 



Supposing e 9 as in the former articles, to be the dif- 

 ference of the two semi-axes of the meridian, 

 e % = 2 a c, and the above will become, 



It is evident from this, that the attraction of a sphe- 

 roid, in the plane of its equator, does not decrease 

 exactly in the inverse ratio of the square of the dis- 

 tance ; on which account a small inequality is 

 produced in the motion of the satellites belonging 

 to planets which are not entirely spherical. The 

 Moon is subject to an inequality arising from this 

 cause, as are also the satellites of Jupiter. 



SECT. 



