Small 13 10.58 in. 14 18 200 8.5 dynamite
The length of a large modern torpedo, it will be observed, is only three inches less than that of Fulton’s famous submarine boat of 1801. A Whitehead torpedo is really a small automatic submarine, steered and controlled by the most ingenious and sensitive machinery, as surely as if it were manned by a crew of Lilliputian seamen.
Projecting from the head is the “striker,” a rod which, when the torpedo runs into anything hard, is driven back in against a detonator or “percussion-cap” of fulminate of mercury. Just as the hammer of a toy “cap-pistol” explodes a paper cap, so the sudden shock of the in-driven striker explodes the fulminate, which is instantly expanded to more than two thousand times its former size. This, in turn, gives a severe blow to the surrounding “primer” of dry guncotton. The primer is exploded, and by its own expansion sets off the main charge of several hundred pounds of wet guncotton.
The reason for this is that though wet guncotton is safe to handle because a very great shock is required to make it explode, dry guncotton is much less so, while a shell or torpedo filled with fulminate of mercury would be more dangerous to its owners than to their enemies, because the slightest jar might set it off prematurely. Every precaution is taken to prevent a torpedo’s exploding too soon and damaging the vessel from which it is fired.
When the torpedo is shot out of the tube, by compressed air, like a pea from a pea-shooter, the striker is held fast by the “jammer”: a small propellor-shaped collar, whose blades begin to revolve as soon as they strike the water, till the collar has unscrewed itself and dropped off after the torpedo has traveled about forty feet. A copper pin that runs through the striker-rod is not removed but must be broken short off by a blow of considerable violence, such as would be given by running into a ship’s hull. As a third safeguard, there is a strong safety-catch, that must be released by hand, just before the torpedo is placed in the tube.
The explosive charge of two or three hundred pounds of wet guncotton is called the “war-head.” In peace and for target-practice it is replaced by a dummy head of thick steel. The usual target is the space between two buoys moored a ship’s length or less apart. At the end of a practice run, the torpedo rises to the surface, where it can be recovered and used again. This is distinctly worth while, for a modern torpedo costs more than seven thousand dollars.