IVORY'S i 



ihews that a shell of any t '. V.n> >. ?,. internal and external 



COO- 

 10 attract ft portiek within 



:-.er hou: has been already established; see 



229. Suppose we require the a: of a spheroid on 



111 tjrtrrnnt parti. 1,-. 



the equation (2) of Art 226, we shall now have F 9 - II 

 i /wiVi'iv quantity, and the two root* of that quadratic equa- 

 v ill have the tame sign. 1 1. nee we shall find 



limits of the integration with respect to 6 will involve 4, 

 so limits will be found by putting // . 

 to the following quadratic equation for determining tan 0, 



: the limits of <f> are to be determined from the condition 

 that H of tan furnished by this quadratic conation 



be e*mal; this leads after some reduction to the following 

 equation for determining the limits of ^, 



however unnecessary to proceed with these complicated 



ations, for we can obtain the result it i.y means 



orcm, \v a relation between tho 



*oid* on external and internal particles ; this 



..ill be true for spheroids as they are included among 



iV/ji. and since the attraction of a spheroid on an internal 



as been alrca theorem will enable 



attraction of a spheroid on an external particle. 



*. We shall i preliminary del and pro- 



posi re we give Ivory's theorem. 



