Torpedoes and Torpedo Warfare / Containing a Complete and Concise Account of the Rise and Progress of Submarine Warfare

by Charles William Sleeman

The metals being the best known conductors, are usually employed as the means of transferring the electric current from one place to another.

Electric Circuit.—The conditions attending this operation are different from those of any other known method of transmission.

A complete circuit must always be formed by the electric current, i.e. it cannot start from one place A, travel to another place B, and cease there, but the current must be completed before it can be said to have reached B. There cannot be a current of electricity without a means of recombination, which recombination must be at the source, or place of original disturbance.

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.