o&tt of V in the COM of a tpbncal 



r'un'-ti.'n if f/ir- ili*t'in f, ,, t r> 



f -r the axis of x the straight line joi centre of 



[ \\ ith the attracted p. obviously the 



i of t attraction; let a be the distance 



in the n distance of any point it 



g shell from and <f> the other polar 



itcs of this point ; then the mass of the element at 

 it is pu'in0ouo0o<l>, and 



F- 



re M t and u, are the internal and external radii of the 



Now r'-y' 



therefore sin 6 -3- 



and V-^jjpududr. 



We must now distinguish three 



1 ''. /* is beyond the external surface, the limits of r 

 arc a u and a + u ; therefore 



-':/> 



.t if A/ denote the mass of the spherical shell, 



