1880.] under the gravitation of its own parts. 9 



Similarly the coefficient of z vanishes, and the equation be- 

 comes 



/ c 2 — a 2 \ 2c 2 „ /„ a 2 — b*~\,~ ^ 



or 



ldp f (c 2 -a 2 )(3c 2 + a 2 ) , ,c'-a 2 



(a + 6 ) 3 a 2 + 6 2 3 * * j 



with two similar equations in y and £ ; or 



where 



p a# p ay * p dz ' 



(c + a ) 2 c + a 



(a» + 6")» " 3 "^^+1 2 3 ^~ C 



, , 4c ! (c 2 -a 2 ) n2 (c 2 -a* 



_46V-J 2 ) _/M V 



(a 2 + 6 2 ) 2 1Zs W + 6 8 8+ V 



, _ 4aV- 6 2 ) , [ a*-b 2 



^-c^,_/^ + | 



(6 2 + c 2 ) 2 » W + c : 



45 2 (6 2 -c 2 ) , /6 2 -c 2 n J 

 C " G+ (&' +c 2 ) 2 ^~{¥T? ill ~\ 



4a 2 (c 2 -a 2 )„ 2 /c 2 -a 2 , \ 

 (c + a ) 2 \c + a 2 / 



