152 HOUSTOX, KENXELLY THE PATH OF A CURREXT. [Mar. 19. 



Fig. 3, represents two parallel wires, AB and CD, the latter posi- 

 tively and the former negatively charged. Here the flux issues 

 from the wire CD, and converges upon the wire AB, in curves, which 

 are all arcs of circles. The flux density is greatest in the neighbor- 

 hood of each wire and least in the intermediate portions. On the 

 left-hand side, the longitudinal section shows that the flux is dis- 

 tributed uniformly in planes perpendicular to the two wires. 



The electric flux, which thus permeates the insulating medium, per- 

 sists as long as the insulation is maintained, even in the absence of 

 the original electric source. Thus, if a pair of wires be perfectly 

 insulated from each other, and are charged as represented in Fig. 3, 

 by connection to an electric source ; then, so far as is known, the 

 electric flux, which will be developed between them in the insulat- 

 ing medium, will be indefinitely maintained, although in practice 

 there is always sufficient leakage to permit the charge to gradually 

 disappear. 



In order to study the electric transmission of power over a cir- 

 cuit, we may suppose that a pair of perfectly conducting wires exists 

 extending between two cities. These conductors may be, say, of the 

 third type; /. e.^ may consist of a pair of parallel wires supported in 

 air. Let AB and CD, Fig. 4, represent such a pair of conductors 



Fig. 4 „E„ 



-D 



Fig. 5 E 



A B 



_ ^^ liiMO **■ J. 



Fig. 6 E 



^ A SlA^ 





Figs. 4-6. — Movement of Electric Flux in Circuit of Perfect Conduction and In- 

 sulation. 



between the terminal stations AC, on the left hand, and BD, on the 

 right. At the middle of the line E, we may suppose that suitable 



