th 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.

In photographing the bores of great guns, electric lights are used, and
they make known if the gun is accurately rifled and how it is standing
the erosion of the powder gases.

In the case of a fort, electricity can be employed in connection with the
instruments used for determining at each instant the position of an
approaching vessel or army. Whitehead torpedoes are now so arranged that
they can be ejected by pressing an electric button.

Electric lights for vessels are now of recognized importance. At first
they were objected to on the ground that if the wire carrying the current
should be shot away in action, the whole ship would be plunged in
darkness; and so it would be in an accident befalling the dynamo that
generates the current. The criticism is sensible, but the answer is that