he torpedo is thus simple, the defense of a
harbor becomes a complex problem, on account of the time and expense
required to perfect it, and the training of a corps of men to operate the
torpedoes.

In order to detect the presence of torpedoes in an enemy's harbor, an
instrument has been invented by Capt. McEvoy, called the "torpedo
detecter," in which the action is somewhat similar to that of the
induction balance, the iron of a torpedo case having the effect of
increasing the number of lines of force embraced by one of two opposing
coils, so that the current induced in it overpowers that induced in the
other, and a distinct sound is heard in a telephone receiver in circuit
with them. As yet, this instrument has met with little practical success,
but, its principle being correct, we can say with considerable confidence
that the reason of its non-success probably is that the coils and current
used are both too small.

Lieut. Fiske described the spar torpedo and the various classes of
movable torpedoes, including the Lay. His conclusion is that the most
successful of the movable torpedoes is the Simms, with which very
promising experiments have been conducted under the superintendence of
Gen. Abbot.

Recent experiments in England have shown that the Whitehead torpedo, over
which control ceases after it is fired, is not so formidable a weapon
when fired at a ship _under way_ as many supposed, for the simple reason
that it can be dodged. But an electrical torpedo, over which control is
exercised while it is in motion through the water, cannot be dodged,
provided it receives sufficient speed. For effective work against ships
capable of steaming fifteen knots per hour, the torpedo should have a
speed of twenty knots. There is no theoretical difficulty in the way of
producing this, for a speed of eleven knots has already been recorded,
though an electric torpedo, to get this speed, would have to be larger
than a Whitehead having the same speed. It may be conceived that a
torpedo carrying 50 lb. of gun-cotton, capable of going 20 knots per
hour, so that it would pass over a distance of 500 yards in about 45
sec., and yet be absolutely under control all the time, so that it can be
constantly kept pointed at its target, would be a very unpleasant thing
for an enemy to meet.

Military telegraphy is a second use of electricity in warfare. Lieut.
Fiske traces its origin to our own civil war. Foreign nations took the
hint from