If the singularity is a point source of strength m, then 



Q 47r I— 1 — 1 I J 



Then , as | r | -> °° , 



r(r t) m r 





-|r|' \\r\') 



and as r -^ r 



Q 4tt z 

 e 



If these expressions are inserted into Equation A-2, the following 

 results are obtained by carefully evaluating the limits 





r| -> oo ^e ^ 



= - p V m + pm [V + V^(r^)] 



= pm VgCr^) 



/r — r 



-'{ "''' I- k^ ''''' 



72 



