﻿of Radiation in any Material System. 521 



These conditions can be imposed on SF because F is 

 denned by (24) completely as a function of the distribution 

 and velocity of the charge. 



Now at any surface where F is normal the condition 

 Div F = reduces to 



dv 



H^v> =0 (34) 



where -7- denotes differentiation along the outward drawn 



civ ° 



normal v and p u p 2 are the principal radii of: curvature. 

 (34) and the similar result for 6F gives 



Multiply (33) by dv and integrate throughout the volume V 



3 3 



Use (35) and notice that the right-hand side vanishes by 

 partial integration since <p is zero at 8. We have 



j( F ^-O= ' 



ft^dv^fafdv, 



3 3 



\<]>J!>pdo = $ \<j) pde. 



*3 3 



SlLn/dt^-ATfi^dvdt, . . . (3G) 

 :j=f{^+*p(^-*o)}*.. • • (37) 



or 



also 



(31) reduces to 



4 



where 



