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 required in the development of the full force of the explosive.  Gen. Abbot’s results for intensity of action per unit of weight of the most important substances is as follows: 

Blasting gelatine........................... 142
Forcite     "    ........................... 133
Dynamite No. 1.............................. 100
Gun-cotton, wet.............................  87
Nitro-glycerine.............................  81
Gunpowder.............................. 20 to 50

Col.  Bucknill, of the Royal Engineers, in his publication of 1888, gives the following: 

Blasting gelatine........................... 142
Forcite     "    ........................... 133
Dynamite No. 1.............................. 100
Gun-cotton, dry............................. 100
"         " .............................  80
Gunpowder...................................  25

In both tables dynamite No. 1 is assumed as the standard of comparison.  Col.  Bucknill states that his gun-cotton results differ from Gen. Abbot’s, because he experimented with much larger quantities, viz., 500-pound charges.  Gen. Abbot’s experiments led him to believe that an instantaneous mean pressure of 6,500 pounds per square inch would give a fatal blow to the double bottom of a modern armorclad, and he developed a formula which gives this blow with blasting gelatine at the following distances under water, viz.: 

Pounds. 
At  5 feet..................................   4
" 10  "  ..................................  17
" 20  "  ..................................  67
" 30  "  .................................. 160
" 40  "  .................................. 311

Col.  Bucknill’s experiments caused him to believe that a pressure of 12,000 pounds per square inch is required, and his formula, which is somewhat different from Abbot’s, gives widely different results at close quarters, but they approach each other as the distance increases.