ITOKV'S 



Cor nu t\\ >ids are points v 



co-ordinates :i >rtional t> th-- ax<-s t<> \\hirh they arc 



respectively parallel. 



toids the distance between two , ne on 



each ellipsoid, is equal to the distance between their < 

 sponding points. 



Let (x, y, z) and (f, 17, f) denote two points /'and Q <m an 

 ellipsoid whose semi-axes are a, b, r; tlu-n the corresponding 

 points 7 X ami (f on an ellipsoid wi. 

 will be denoted by 



/a/iC S'y c'^\ , /a'f 7/7; r'f\ 

 U > b > c) U ' /' ' T/' 



Thus 



Therefore PQ"-PQ* = 



because the ellipsoids are confocal. 



fore 

 thus PQ = P'Q. 



Ivory 8 Theorem. The attraction of an ellipsoid on n 

 tide on the surface of a confocal < resolved parallel t 



an axis ?x t<> thr. attraction of the second ellipsoid on tlif 

 corresponding j>int <m the surface of the fast ellipsoid, so 



