1897.J HOUSTON, KEXNELLY — THE PATH OF A CURRENT. 149 



Both electric and magnetic fluxes contain energy. Work must be 

 charged on the flux to establish it, and this work is liberated when 

 the flux disappears. The energy in the ether varies as the square of 

 the flux density, so that if we crowd uniformly twice as much flux 

 through a given area of cross-section, we quadruple the amount of 

 energy which resides in that portion of space per cubic inch, or per 

 cubic centimetre. 



The electric transmission of power consists in transferring electric 

 and magnetic flux to a distance and allowing these fluxes to be ex- 

 pended in liberating, at the receiving end of the line, the energy 

 they contain. An electric generator is a machine for producing 

 electric flux and thus transferring electric energy to the ether. This 

 electric flux, or energized condition of the ether, is transferred to a 

 distant point along wires, the ether being deprived of its energy at 

 the receiving end of the line. The electric flux is there absorbed, 

 and the work which was expended by the generator is recovered to 

 a greater or less extent. 



The electric flux is transmitted from the generator to the receiver, 

 through an insulating medium, being guided on its passage by a 

 pair of conductors, extending all the way from the generator to the 

 receiver. Such a pair of conductors, with the associated insulating 

 medium between them, is called an electric circuit. The curious fact 

 exists that while the old conception of an electric circuit held that 

 the electric current passed through the conductors, and was retained 

 in position on those conductors by reason of the insulating medium 

 surrounding them, the modern view holds, on the contrary, that 

 the electric current flows through the insulating medium and is held 

 in position, or guided to its destination, by the two conductors. In 

 other words, the modern theory completely reverses the relative 

 functions of the insulator and the conductors in the old theory. 



There are three standard types of pairs of conductors, and their 

 associated, intervening, insulating medium; viz., 



1. An aerial conductor, such as a telegraph wire, supported sensi- 

 bly parallel to the surface of the ground. Here the wire forms one 

 conductor, the ground the other conductor, wliile the ether asso- 

 ciated with the air between them is the medium through which the 

 electric current flows. 



2. Subterranean or submarine conductors separated from the 

 surrounding conducting earth or water by a uniform layer or coat- 

 ing of insulating material. Here one conductor is formed by the 



