204 



Trans. Acad. Sci. of St. Louis. 



the angular velocities of the rotating lines are, numerically, 

 inversely proportional to the charges on their respective 

 axes. 



Equations (2) and (4) also have the same form, and in this 

 case also the primed constants are interchanged. This shows 

 that the curve representing a line of force proceeding from a 

 system consisting of two parallel electrified lines having charges 

 of the same algebraic sign is the locus of the intersection of 

 two straight lines rotating in the same plaue about the two 

 parallel lines as axes with angular velocities having opposite 

 algebraic signs (i. e., the lines rotating in the opposite direc- 

 tions) ; also, as in the last case, that the angular velocities 

 of the rotating lines are, numerically, inversely proportional 

 to the charges on their respective axes. 



Fig. 2 shows the lines of force proceeding from a system 

 consisting of two parallel and oppositely electrified lines A and 

 A' having charges m = 2 and — m' = — 1, respectively. If A 

 and A were the axes of two wheels having radial spokes, 

 and if wheel A rotated twice as fast as wheel A and in the 

 same direction, the points of intersection of the spokes of A 



