Submarine mines:—As before.
Effect of explosion:—(a) mine, at 146' distance, split in two; (b) mine, 34' distance, destroyed; at 49' distance, fractured; at 68' distance, indented but not fractured; (c) mine, 58' distance, case much bulged, and leaky; (d) mine, at 244' distance, rivets started, case half full of water; at 195' distance, sunk, several rivets started; (e) mine, at 195' distance, bolt loosened; (f) mine, at 68' distance, not injured.
3rd Experiment.
Countermine:—453 lbs. of dynamite, enclosed in a case, 24-1/2" × 28-1/4" × 1/8". It was moored 9-3/4' below the surface; depth of water as before.
Submarine mines:—As before.
Effect of explosion:—(b) mine, at 49' distance, sunk and not recovered; at 58' distance, very much indented; (c) mine, at 58' distance, case much indented and leaky; (f) mine, at 48-1/2' distance, uninjured.
4th Experiment.
Countermine:—As before, but moored 29-1/4' below the surface.
Effect of explosion:—(a) mine, at 195' distance, completely stove in; (c) mine, at 58' distance, case indented but charge dry; (e) mine, at 175' distance, slightly leaky; (f) mine, at 48-1/2' distance, upper half indented in three places. It was also discovered during the above experiments that submarine mines charged with dynamite can be caused to explode by the detonation of a charge of the same explosive, at distances from it considerably beyond those at which the cases themselves are damaged by a similar charge. To prevent the foregoing, it is necessary to pack the dynamite very carefully, using at the same time special precautions.