and 



On the Theory of Surface Forces. 469 



Again, by II. (17), 



vo>,pi)= p2va-s/wQ^ 



»/ —oo 



Jo Jo 



Jo Jo 



- E { (p2 " Pl) J " *® ?rfr ~ ^ -Pl )£ +©*#} • 



Consider now 



(p-Pi).V(p,/>i) + (ft-p).V(p«,p), ... (2) 



and collect separately the part independent of E, and that 

 proportional to Br 1 . For the first we have 



''W-ftlffM .... (3) 



the same as if a=0. 



For the second, omitting the factor — 27r/R, we get 



(p-pO {<*-*)[" * (Of «- (ft-ri [ a *C0 ?^} 



(ps-p) { (p?-pi) rv (o?^?-(p-pi) r V(o?rft}, 



fe-pp 2 J>(o?^-2(p-^(p s -/»)rf(0(:^ . w 



K=2tt [>(?)<*?, 



? 2 -i>i=K( P /-p 1 2 )+2T/E, .... (5) 



-2ir(p-p I )0>2-p)[V(?)rrf&-. • . (6) 



+ 

 or 



Now 



so that 

 where 



