This "place of disturbance" or _source_ must be considered as having two sides, i.e. at some spot the normal or natural electrical equilibrium is disturbed, and electricity is separated into too much (positive) on one side, and too little (negative) on the other side. If then no means of recombination be afforded, the electricities remain separated, and no current exists; but if a _conductor_ be made to connect the two sides, electricity is set in motion, and a current established. Originally to form a circuit between two stations _A_ and _B_, a conducting wire and a return wire were necessary, but in 1837 Steinway discovered that the earth itself answered all the purposes of a return wire, in fact under favourable conditions much better. Thus, to form a circuit between _A_ and _B_, a conducting wire is required, and a buried metal plate at _A_ and _B_, the earth by these means taking the place of the return wire. The aforesaid metal plates are technically termed _earth plates_. The greater the size of the earth plates (up to certain limits), the deeper they are buried, and the better the conducting power of the soil surrounding them, the better conductors the plates become, or the less resistance the earth portion of the circuit offers. If either plate be not in communication with the earth, or else be separated from the wire, the circuit is not complete, or, as it is termed, "it is broken," and no current will flow, the signal not made, torpedo not fired, &c. _"Short" Circuit._--Due to the fact that recombination, or a tendency to equilibrium, is always at work when electricity has been evoked, the conducting path along which the electric current flows must be covered with a nonconducting substance, or, as it termed, "insulated," or else the current would not perform its duty, but escape to earth, and so form what is termed a "short circuit." A current of electricity always chooses the _easiest path_ to effect recombination, or electrical equilibrium. _Insulators, &c._--On land, telegraph wires are as a rule laid above the ground, and therefore require supporting at every few yards; this is done by means of posts, and as these are formed of substances which are conductors of electricity, the wires require to be insulated from them. The insulators generally employed for such purposes are cup-shaped pieces of porcelain, or pottery, fixed to the head of the telegraph posts. By means of these insulators, the current of electricity is prevented from escaping to the earth by the post conductors. A certain amount of leakage, or loss of electricity, must occur at each of these posts, as there is no such thing as a perfect insulator. When the wires are laid on the ground or under ground, or under water, they are insulated by covering them with gutta percha, india rubber, &c., and any loss of current is thus prevented. _Methods of generating Electricity._--For the purposes of torpedo warfare there are two methods of evoking electricity, viz.--