Manchester Memoirs, Vol. I. {igo6), No.H. 27 



Hence the density of particles, which varies as Ljr, or as i/r"+^ 

 falls off about as the inverse fourth power of the distance up to 

 r= I '8, and then much more rapidly. 



TABf.E I. 



NOTE IV. 



If we do not take the special case where a = R, we arrive at 

 the integral 



K C sin9/zfi 



where 



and is positive if 



negative if 



^J \{2a. 



VrJ \{2uR- A''}cos'y -f Z\ 



Z={a — Rf - {r - ci)' 



a - R^ r - a or r <^ 2a - R ; 

 r-^za-R. 

 We thus have two cases to deal with in the integration. 



