3.—They do not require specially trained men to manipulate them.
4.—Extempore ones can be easily and readily made.
Best Kinds of Mechanical Mines.—Among the very numerous and various kinds of mechanical submarine mines that have been devised the following may be considered as the most effective, and practicable of them all:—
- 1.—Frame Torpedoes.
- 2.—Buoyant Mines.
This includes:—
- a.—Barrel Mine.
- b.—Brook's Mine.
- 3.—Singer's Mine.
- 4.—McEvoy's Improved Mine.
- 5.—Extempore Mine.
Frame Torpedoes.—This form of defensive mine is shown at Fig. 6. It consists of a frame work which is formed of four strong timbers a, a, a, a, these being kept parallel and only a few feet apart by means of cross timbers b, b. A cast-iron torpedo c, c, c, in the shape of a shell, is bolted to the head of each of the timbers a, a, a, containing about thirty pounds of fine grained gunpowder, and fitted with a percussion fuse, which is so placed that it would come into contact with a vessel striking against the framework, directly or not. One end of the frame is securely anchored, the other, that on which the torpedoes are fixed, is kept at its proper distance below the surface of the water by means of chains, d, d, and anchors. To prevent the frame from sinking when sodden with water, the uprights e, e, are provided.
This form of mechanical mine, which performs the double function of torpedo and obstruction, was much used by the Confederates, and found extremely useful, no passage was attempted to be forced by the Federals where these torpedoes were known to be placed.
Stake Torpedo.—[Fig. 7] represents another form of the frame torpedo.
It consists of a piece of timber, a, its heels secured by a heavy metal shoe b, working in a universal joint in the mooring, c. At the head of the piece of timber is secured a torpedo d, containing about fifty pounds of gunpowder, and fitted with four or five sensitive fuzes. The proper angle of inclination is obtained by securing the upper end of the timber to an anchor as shown at e. As a proof of the efficiency of this species of mechanical mine, even though having been in position for a great length of time, the U.S. gunboat, Jonquil, was nearly destroyed whilst attempting to remove some similar torpedoes which had been in position for two years.