FRAME TORPEDOES, BUOYANT MECHANICAL MINES.
The Barrel Torpedo.—One description of this form of mechanical submarine mine is shown at [Fig. 8]. It consists of a barrel a, to the ends of which are attached two cones of pine b, b, for the purpose of preventing the current from turning the mine over.
To ensure its being watertight, pitch is poured into the interior through the bunghole, and the barrel rolled about, so that the inside may be evenly covered. The outside was also thoroughly coated with pitch. These mines usually contain about 100 lbs. of gunpowder, and are exploded by means of percussion or chemical fuzes (c, c, c,) generally five in number, screwed into sockets on each side and on the top of the bilge of the barrels. To keep them upright a weight d is hung below the mine.
This kind of mechanical mine was much used by the Confederates, and to some extent by the Turks in their late war with Russia.
They are cheap, convenient, and under certain circumstances very effective. One of the objections to their use is the difficulty of mooring them securely in strong currents, as otherwise they are very liable to shift their positions. Three Confederate vessels were "hoisted by their own petards," from this cause.[I]
Brook's Torpedo.—Another form of buoyant mechanical mine is represented at [Fig. 9]. It was designed for the express purpose of preventing its discovery by dragging, etc., by the enemy. It consists of the torpedo case a, formed of copper, which is attached to a spar b, the lower end of which is secured to an universal joint in its anchor c. Five percussion or chemical fuzes d, d, d, are screwed into the head of the copper case.
Turtle Torpedo.—To increase the danger and uncertainty of any attempt to remove this form of buoyant mine, a turtle torpedo A, is attached to it by a wire e. This torpedo contains about 100 lbs. of gunpowder, and is exploded by means of a friction primer which passes through a watertight joint f, and is attached to the wire e.