94-95] 



ST11EAM-L1NES DUE TO A SPHERE. 



137 



Again, the stream-function due to two double-sources having 

 their axes oppositely directed along the axis of x t will be of the 

 form 



where r ly r. 2 denote the distances of any point from the positions, 

 P! and P 2 , say, of the two sources. At the stream-surface i/r = 

 we have 



