Eoever — 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 — a> = 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 w = &)' = 0, then from equation ( 1 ) 



6 = 



m 



m — m 



a. 



(6), 



which determines the direction of the asymptote to a line of 



