Effect of explosion:—Outer bottom and frames injured in a similar manner to that described in the third experiment. Outer angle irons of the 1st, 2nd, and 3rd longitudinals were started in the wake of the broken place. A hole was blown through the inner bottom, measuring 9·5' × 1', or about 10 square feet in area. The bolts of the outer bottom plate of stern post much open, and at Nos. 16 and 17 on the port side the upper two strakes were buckled and the shelf plate started.
A steam launch, arranged in the same manner as in the fourth experiment, was uninjured, and shipped but little water.
Experiments with Countermine.—The following experiments have been carried out in England and other countries to ascertain some reliable data for countermining operations.
1st Experiment.
Experiments in the Medway, England, 1870.—Countermine:—432 lbs. of compressed gun-cotton, enclosed in a 3/16" iron case. It was moored at a depth of 37' below the surface of the water.
Submarine mines:—A series of similar cases containing coal dust, &c., were moored at distances of 50' to 100' from the countermine, and 37 feet below the surface.
Effect of explosion:—The submarine mine at 80' distance was completely destroyed; the dome of its circuit closer was dented in.
2nd Experiment.
Countermine:—As before, but moored 27' below the surface.