Boever — Geometrical Properties of Lines of Force. 279 



2. The system having electric charges of like signs corre- 

 sponds to the case in which OP has < . ^^^ j.j> rotation 



and JPD has a motion to the 



C right ) 



( left r 



ight handed 

 Fi2. 2. 



Fig. 3 shows the lines of force proceeding from a system 

 consisting of one electrified plane AB and an electrified line 



O parallel to this plane.* In the figure — = — = r ^ = 01, 



air nir 



These are the curves that would be seen by looking at the 



wheel of a passing wagon through a picket fence. In this 



Fig. 3. 



case, however, the concave portions of the curves would be 

 upward regardless of the direction in which the wagon is mov- 

 ing, so long as the wheel receives its rotary motion by rolling 

 on the ground. 



* The lines of force do not extend beyond (below in Fig. 3.) the elec- 

 trified plane, but terminate in it. The equations, however, represent curves 

 which extend indefinitely beyond the electrified plane. 



