ENERGY ACCELERATIONS, A STUDY IN ENERGY, &C. 285 



Then 



d f\ ,\ dV fdV, . dF,,\ 



d W N dV /dV,, . df\\ 



Hence 



^/2 /l \ diK dV / d , d\dV 





d'- ^1 ,\ 1 ^dj\'^ ,d^r d'-r 



Assumiug /' {a\, a-^) d,t\ d.i'^ to represent tlie probability of tlie two 

 particles lying between the points a\, ir.^ and .i-, -|- ^/^'j , % -\- dx.^ 

 respectively, we j)i*oceecl to replace tlie expressions by tlieir mean A^alnes 

 as in Example 1. 

 Now 



showing that [d?'V\d,x^dx^~] is usually différent to zéro, and tlie mean 

 ])roduct [77, r.,] enters into the équations of energy equilibrium unless 

 for some reason its value is zéro 



[a) If flm happeiiH fo h/' Ihe casi^ the équations of energy equili- 

 brium give 



ri ,-1 Lv^y J ,ri 2-| Lv^y j 



^Vdx:^\ Vdx^^\ 



