intended to reduce the effects of Inductive Action. 337 



earth. We must indeed look upon the earth as a great reser- 

 voir, capable, with proper arrangements, of affording any supply, 

 or of disposing of any discharge. If the Atlantic Cable were 

 a tube carrying water instead of electricity, receiving it at 

 one end and discharging it at the other, it would never be as- 

 sumed that the portions discharged in America would flow by a 

 return current back through the ocean to supply the other end ; 

 and the cases are precisely similar : the earth acts the part of a 

 reservoir with regard to electricity as much as the ocean does 

 with regard to water ; and the circumstances under which return- 

 currents either of water or electricity could be produced, would 

 bear the same analogy to each other. The only benefit, then, 

 which the present wire could confer, would be by improving 

 to a certain extent the conducting character of the earth, or 

 in other words, by increasing its capacity to receive the dis- 

 charge, or afford the necessary supply. I am free to admit, 

 however, that with the present wire the amount of assistance 

 that would be afforded might be limited from its vei'y inadequate 

 conducting capacity. With a capacious insulated return wire, 

 however, the case would be different. It would, as I stated in 

 my last paper, lessen the amount of induction by decreasing re- 

 sistance, and consequently obviating the necessity of employing 

 currents of high tension ; but it must not be inferred from this 

 that inductive action would not take place at all. The two cables 

 would, in fact, when carrying reverse currents, represent two 

 Leyden jars oppositely charged, and with their outer coatings in 

 conducting communication with each other, or as is actually the 

 case, both uninsulated. Let us now examine the various condi- 

 tions of such an arrangement. 



1st. Take a single cable working to earth at the remote end ; 

 the effect, however instantaneous, must originate at the battery 

 end. If a positive current be transmitted, the wave proceeds by 

 propulsion from the battei-y to the remote end, which remains 

 normal until the excess of current over the resistance of the wire 

 and the inductive action through the dielectric, makes its appear- 

 ance there, and the effect of the discharge at that end will depend 

 upon the relation of these counteracting elements to each other. 

 If a negative or reverse current be transmitted, still the effect 

 commences at the battery end by exhaustion (for want of a better 

 term), and the remote end still remains normal until the resist- 

 ance offered by the wire to the passage of electricity in that 

 direction, and the inductive action of the dielectric, shall have 

 permitted the effect to be manifested at the other end. In either 

 case, the amount of the effect at the remote ends will result from 

 a single force operating in one direction only. 



2udly. If whilst a cuiTcnt, say for example a positive onOf 



