266 Mr KELLAND, ON THE MOTION OF 



but Stt ^ ° . . ... = S 



{ {x - «)■- + y- + z')i -^ \t--{2ax- a') \ i 



^.r-a L 3 f2aX-a'\ 3.5 (2aX-nY , 3.5.7 /..-V , 1 



1 f 3 2aaf-2a'x + a'' 



r' \ 2 r 



3.5 /4aV^^8aV\ 3.5.7 /8a'ar'\ 1 



"•" 274 I ? ) "^ 2 . 4 . 6 I /•■= 7 ■•■} 



'2? -^-^r' + 2 »•" 



f x' + y + x' \ 



Now S ^ =32 



r 



,2 9 



-.2 1 



3a^' 



f)=o. 



1 /3 15.r' 35 a;', 

 also it is evident that 2 2-5 ( ^ -= — ►" "^ r: 



= ^P 



r V2 r' 2 •/• 



3 





= 2^J-7^'-14.rY+f.r'} 



= 2^ |14a''-42ar>''} 



= 14 2^{.r'-3xyi; 



so that the tendency will be to restore the equilibrium, if 



2-^(a;' — 3/) is negative. 



