Torpedo Characteristics
The vessel was intended to use torpedoes containing 400 lb (180 kg) of black powder; but those actually employed by it contained 60 lb (27 kg) of fine powder of the kind known in the American service as No. 7. The "obstruction shells" have each an air space left round the powder, so as to allow the free expansion of the gases, and the torpedoes intended for use against vessels are of slightly less specific gravity than water, so that when released from the holder they rise slowly until they come against the bottom of the vessel under which they are placed. As will be seen by the section, Fig. 2, the powder is so placed in the torpedo that, when the later is released, it floats nearly upright with its point downwards. Within the torpedo case, on one side, is placed a tube, at the lower end of which is a percussion fuse in communication with the powder. At the upper end of the tube is a ball, which is held from falling upon the percussion fuse by a sliding pin placed beneath it. This pin passes out through the torpedo case, and has an eye formed at its outer end, as shown in Fig. 2. When the torpedo is placed in the casing at the end of the projecting tube, that side of the torpedo through which the sliding pin just mentioned projects is placed downwards, and one end of a cord is attached to the eye of the pin, and the other end to another eye fixed to the casing at the end of the projecting tube. The length of this cord is regulated according to the distance at which it is desired to fire the torpedo — the length generally employed being about 20 ft (6 m) — and it acts in the following manner: When the torpedo has been projected by means of the tube and released, the tube is of course drawn back, and as this movement takes place the cord is tightened, and the sliding pin is withdrawn from the torpedo case, this movement releasing the ball and allowing it to fall upon the percussion fuse, and explode the torpedo.
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