Comparing the effect of this torpedo with the 7th, 33 lbs. of dynamite; with the latter charge the breach was made at the cost of the bottom plates as well as the vertical and longitudinal frames, which were completely torn asunder and strained; with the gunpowder charge, only the bottom plates were broken through, whilst the plates whose directions were nearly parallel to the lines of explosive effect were but little affected.
Experiments at Portsmouth, England, 1874-75.—The object of these experiments was to ascertain the effect of 500 lbs. gun-cotton torpedoes exploded at various distances from a target representing the double bottom of H.M.S. Hercules.
They were carried out in Stokes Bay, under the supervision of officers belonging to the torpedo department of the Royal Engineers, and a torpedo committee, composed of naval and military officers.
The Oberon, the vessel chosen for these experiments, was fitted with a double bottom, representing as nearly as possible that of the Hercules without the armour; also with a surface condenser, and its connections; a donkey Kingston feed-valve; and athwartship water-tight bulkheads, which divided the ship into seven water-tight compartments. The outer skin was composed of 3/16" and 7/8" iron plates. In her starboard side at different points were fixed forty-four crusher gauges, and over each side were suspended six shots, each fitted with a crusher gauge.
Displacement of the Oberon about 1100 tons.
The ship was anchored head and stern. Her mean draught of water during the experiments was 11 feet.
1st Experiment.
Torpedo:—500 lbs. of gun-cotton, in discs saturated with water, and enclosed in an iron cylindrical case, 34" × 30" × 1/4", with arched ends; the primer consisted of two dry discs, and two detonators. It was placed 101' horizontal from the target, and opposite the condenser on the starboard side; 47' below the surface of the water, on the ground.
Effect of explosion:—No damage was done to the hull, or condenser, but light articles, such as bunker plates, gratings, tank lids, &c., were displaced.