Roever — Geometrical Properties of Lines of Force. 287 

 m versin co — nrax 2 — K (25), 



in which Zisa constant. If in equation (25) x = 

 K = m versin co = m versin a, 



in which a is the special value of co for which x = 0. Sub- 

 stituting this value of K, equation (25) becomes 



m (versin co — versin a) = irox 2 (26). 



For co = equation (25) becomes 



K = — it ax 2 = — it ox 2 . 



Substituting this value of K, equation (25) becomes 



ttcf (x 2 — x 2 ) = m versin co (27). 



If the point and plane have charges of like signs the 

 equation of a line of force is 



m versin co + ttox 2 = K' (28), 



in which K' is a constant. For x = this equation becomes 



K' = m versin a. 



Substituting this value of K', equation (28) becomes 



m (versin co — versin a) = — irax 2 (29). 



For co = V equation (28) becomes 



K ' = 2m + ttctx 2 



Substituting this value of K', equation (28) becomes 



7777 (x 2 — x 2 ) = m (2 — versin co) (30). 



