as a
recognized weapon was during our war of secession, when thirty-seven
vessels were either sunk or seriously injured by them. Gunpowder was
used in these torpedoes, though it is stated that attempts were made
to use other substances without success. Since that time all maritime
nations have made a close study of the subject and have adopted
various high explosives, according to the results of their
experiments. In general terms it may be stated that explosive chemical
compounds have been found more suitable than explosive mixtures,
because of the uniformity of direction in which they exert their
pressure, and from the fact that water does not injure them. Mixtures
may be very powerful, but they are erratic and require tight cases. In
the United States we use dynamite for harbor mines. It is composed of
seventy-five per cent. nitro-glycerine and twenty-five per cent.
silica; but blasting gelatine and forcite gelatine will probably be
adopted, when they can be satisfactorily manufactured here, as they
are more powerful. The former is composed of ninety-two per cent. of
nitro-glycerine and eight per cent. of gun-cotton, and the latter of
ninety-five per cent. of nitro-gelatine and five per cent. unnitrated
cellulose.

For naval use we have adopted gun-cotton as being the most convenient.
In Europe gun-cotton is generally used for both fixed mines and
movable torpedoes; Russia, Austria, and Italy use blasting gelatine
also.

In actual warfare but little experience has been had. Two Peruvian
vessels were sunk by dynamite in the Chili-Peruvian war, one Turk by
means of gun-cotton during the Turco-Russian war of 1877, and two
Chinese by gun-cotton in the Franco-Chinese war of 1884.

In making experiments to determine the relative strength of the
different explosives under water, very curious and puzzling results
have been obtained. Nitro-glycerine being the simplest and most
complete in its chemical decomposition, and apparently the most
powerful in air, it was natural to suppose that it would be the same
in submarine work, but it was found by Gen. Abbot, at Willets Point,
after repeated experiments, as shown in his report of 1881, that it
was not so powerful in its effect by twenty per cent. as dynamite No.
1, although the dynamite contained twenty-five per cent. of an
absolutely inert substance. His idea was that it was too quick in its
action, and, since water is slightly compressible, a minute fraction
of time is