explosive with destructive effect. The danger of premature or accidental explosion by anything coming in contact with the projecting striker is obviated by several checks which prevent any chance blow driving the rod home against the fulminate charge. The anterior projecting end of the rod has a screw thread worked upon it, and on this turns freely a nut provided with wings like a small fan, revolving in such a manner that as the torpedo is moved through the water, the nut is spun off, and the striker is free to be driven back, except in so far as it is still retained by a small copper pin, the breaking of which requires a considerable blow. Again, the little fan above mentioned cannot begin to spin off the rod until another pin or wedge has been withdrawn, which operation is performed just before launching the weapon. Immediately behind the exploding head of the torpedo is the air-chamber, which occupies a considerable space in the length, _i.e._, about one-third of the whole. This part is made of the toughest steel, nearly ⅓ of an inch thick, and contains the power actuating the motor, in the form of air forced into it by powerful pumps on board the ship, until the pressure reaches the enormous amount of 1,300 lbs. or more on the square inch, or, at least, this is what is made use of in the newer patterns when charged for action. In the largest size of the weapon the weight of air injected may be more than 60 lbs., and, of course, considerably detracts from the buoyancy of this part. Behind the air-chamber comes another much shorter compartment we have called the “steering chamber,” in which are contained the most ingenious and delicate parts of the apparatus, namely, the mechanism by which this extraordinary artificial fish adjusts itself, after the manner of a living thing, to the required conditions. Among other contrivances, it contains several valves controlling the action of the compressed air on the engines, etc. The enormous pressure to which the air-chamber is charged, if allowed to act unchecked, would give at first a power almost sufficient to shatter the machinery, and, in order to prevent this, a “reducing valve” is interposed so that only a moderate and uniform pressure of air is allowed to act upon the engines. Then there is the “starting valve” by which the air is admitted or cut off from the engines, and still another valve which is contrived to delay the action of the compressed air for the short interval during which the torpedo is passing from the discharging tube until it enters the water. For during this interval the propellers not having to act against the water, but only against the resistance of the atmosphere, would be whirled round at an enormous speed, and the machinery would sustain such shocks and strains as might endanger the whole apparatus. It is to prevent this that the “delay action valve” is provided.