( 430 ) 

 Div' %' = Jlv\>-^nk p^ (Mv , .... (Ie) 



Div' Jp' = O , (lic) 



BXp'. a.fp'. , , , A= 35'v 

 T.' -^^'"'^^'^"^ i-"ö^" 



3rz^_9g',v __3^\ 

 3?/' 3s' "~ 3t' 



3g':r 35'.- _ 3JpV 



3^' 3/ ~ 3«' 



(llle) 



(TVc) 



3j^' 3'/' 3'' 



Cv = %\- + A- ^2 (IV 5',, + i>-- 5'.) + (% C-»'-- - IV- J?',/) 

 €,/ = 1 g'.v - ^' y. ^- 5',/ + (^y tv /y. - IV .fV,") ) . . (V.) 



<E, =. y 5', - h ^ t.:r 5"'. + (^IV -O y - y % •<> .. 



Putting i> = in tlio three lust equations we sec that 



%x 1 'T ^yi 'T ^~ 



aro the components of the electric force that would act on a particle 



at rest. 



§ 5. We shall l)e»in with an application of the equations 



to 



