The telephone is also used with success in warfare, and in fact sometimes assists the telegraph in cases where, by reason of the haste with which a line has been run, the current leaks off.  A telephone may then be used to receive the message—­and for a transmitter a simple buzzer or automatic circuit breaker, controlled by an ordinary key.  In the case of vessels there is much difficulty in using the telegraph and the telephone, as the wire may be fouled and broken when the ship swings by a long chain.  In England in the case of a lightship this difficulty has been surmounted, or rather avoided, by making hollow the cable by which the ship rides, and running an insulated wire along the long tube thus formed inside.  But the problem is much simplified when temporary communication only is desired between ships at anchor, between a ship and the shore, or even between a ship and a boat which has been sent off on some special service, such as reconnoitering, sounding, etc.  In this case portable telephones are used, in which the wire is so placed on a reel in circuit with the telephone that communication is preserved, even while the wire is running off the reel.

The telegraph and telephone are both coming largely into use in artillery experiments, for example, in tracking a vessel as she comes up a channel so that her exact position at each instant may be known, and in determining the spot of fall of a projectile.  In getting the time of flight of projectiles electricity is of value; by breaking a wire in circuit with a chronograph, the precise instant of start to within a thousandth of a second being automatically registered.  Velocimeters are a familiar application of electricity somewhat analogous.  In these, wires are cut by the projectile at different points in its flight, and the breaking of the electric current causes the appearance of marks on a surface moving along at a known speed.  The velocity of the projectile in going from one wire to another can then be found.

Electricity is also used for firing great guns, both in ships and forts.  In the former, it eliminates the factor of change produced by the rolling of the ship during the movement of the arm to fire the gun.  The touch of a button accomplishes the same thing almost instantaneously.  Moreover, an absolutely simultaneous broadside can be delivered by electricity.  The officer discharges the guns from a fighting tower, whither the wires lead, and the men can at once lie down out of the enemy’s machine guns, as soon as their own guns are ready for discharge.  The electric motor will certainly be used very generally for handling ordnance on board ships not very heavily plated with armor, since a small wire is a much more convenient mode of conveying energy to a motor of any kind, and is much less liable to injury, than a comparatively large pipe for conveying steam, compressed air, or water under pressure.  Besides, the electric motor is the ideal engine for work on shipboard, by reason of its smooth and silent motion, its freedom from dirt and grease, the readiness with which it can be started, stopped, and reversed, and its high efficiency.  Indeed, in future we may look to a protected apparatus for all such uses in every fort and every powerful ship.