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 ignited by means of blasters’ fuse and a cap of fulminate of mercury, or by an electric fuse.

We now come to the application of high explosives to warfare in the shape of bursting charges for shells.  This is the latest phase of the problem, and it is undoubtedly fraught with the most important consequences to both attack and defense.  Difficult as it has been to obtain an exact estimate of the force of different explosives under water, the problem is far greater out of the water and under the ordinary conditions of shell fire; the principal obstacle being in the fact that it is physically impossible to control the force of large quantities in order to measure it, and small quantities give irregular results.  Theoretically, the matter has been accomplished by Berthelot, the head of the French government “Commission of Explosives,” by calculating the volume of