Roever — Geometrical Constructions of Lines of Force. 205 



with those of A would trace the same curves. Fig. 3 shows 

 a few of the lines of force proceeding from a system consist- 



ing of two parallel electrified lines A and A having charges 

 m = 4 and m' = 1, respectively, of like sign. 



If m = m', numerically, equation (1) becomes 



co — to' = a. ( 5 ) , 



which is the equation of a circle referred to the poles A and 

 A . A line of force is only an arc of this circle. It starts at 

 A and stops at A. 



If co = to' = 0, then from equation ( 1 ) 



m 



m — m 



a (6), 



which determines the direction of the asymptote to a line of 



