p energy of a
heavy fly-wheel. Generally speaking, they are cigar-shaped crafts,
from 10 to 18 feet long and 15 to 17 inches in diameter, capable of
carrying from 75 to 250 pounds of explosive at a rate of 25 to 30
knots for 400 yards, at any depth at which they may be set. Of the
controllable locomotive torpedoes, the three representative types are
the Patrick, Sims and Brennan. They are in general terms cigar boats,
about 40 feet long and 2 feet in diameter, carrying charges of 400
pounds of explosive. The Patrick and Sims are maintained at a constant
depth under water by means of a float. The Brennan has diving rudders
like a Whitehead or a Howell. The Patrick is driven by means of
carbonic acid gas through an engine, and is controlled by an electric
wire from shore. The Sims is driven by electricity from a dynamo on
shore through a cable to an electric engine in the torpedo. The
Brennan is driven and controlled by means of two fine steel wires
wound on reels in the torpedo, the reels being geared to the propeller
shafts. The wires are led to corresponding reels on shore, and these
are rapidly revolved by means of an engine. A brake on each shore reel
controls the torpedo. The speed of all these torpedoes is about 19
knots, and their effective range one mile.

A Whitehead was successfully used in the Turco-Russian war of 1877.
The Turkish vessel previously mentioned was sunk by one.

Blasting gelatine, dynamite and gun-cotton are capable of many
applications to engineering purposes on shore in time of war, and in
most cases they are better than powder. They received the serious
attention of French engineers during the siege of Paris, and were
employed in the various sorties which were made from the city, in
throwing down walls, bursting guns, etc. An explosive for such
purposes, and indeed for most military uses, should satisfy the
following conditions:

(1) Very shattering in its effects.

(2) Insensible to shocks of projectiles.

(3) Plastic.

(4) Easy and safe to manipulate.

(5) Easy to insert a fuse.

(6) Great stability at all natural temperatures and when used
in wet localities.

Neither blasting gelatine, dynamite nor gun-cotton fulfills all these
conditions; but they satisfy many of them and are more powerful than
other substances. For the destruction of walls, trees, rails, bridges,
etc., it is simply necessary to attach to them small bags of
explosive, which are ign