To sink the torpedo at the end of its run, a spiral-spring valve is placed in the after wall of the adjustment chamber, which can be attached to the brass rod working the engine-valve in such a way that when the latter valve is closed the spring-valve is opened, admitting water to the chamber and thus sinking the torpedo. If it is desired to explode the torpedo at the end of the run, the nose-piece is connected to the engine-valve, which, on closing, draws it violently back and releases the firing-pin. To adjust the depth of flotation, a small wheel, the face of which is marked in feet, is placed in the adjustment chamber, and is turned by means of a key until the number of feet desired comes under a pointer. The secret of the Whitehead is in the mechanism by which the torpedo maintains a desired depth. The adjustment chamber, which is next abaft the explosion chamber, is connected by screw to the forward and after chambers in such a manner that by means of a number of small holes bored around the circumference the faces of the chamber are exposed to the pressure of the outside water, which varies with the depth to which the torpedo descends. Within the adjustment chamber is an endless strong spiral spring, attached to the after face of the chamber, and so arranged that after being set to a certain tension, capable of resisting an equivalent pressure on the outside of the face, any increase or decrease in this pressure will cause this spring to work a rod by which the horizontal rudders of the torpedo are regulated. Within this adjustment chamber is also placed an automatic balance, which assists in maintaining the torpedo at the desired depth by swinging forward on the torpedo’s descending or aft on ascending, and thus assisting the rudders. The Whitehead may be discharged through a submerged tube in the stern or in broadside, from a carriage above the water-line, or from the surface. For discharging under water a tube is fitted to an orifice in the stern or broadside, closed by a water-tight valve; the inner end is closed by a water-tight door. The torpedo, being prepared, is placed in the tube, the door is shut, water is admitted to the interior, and the valve is opened. The torpedo is then shot out and started by means of a piston bearing against its rear end and worked by compressed air. To prevent it from slipping out before the time, a stop is provided at the forward end of the tube, which is removed automatically at the same time that the compressed air is admitted to the piston. In the case of broadside discharge, the tube works inside an iron casing, through a stuffing-box at the inner end and in a shield at the outer end. The shield, placed on the forward side of the orifice, is of such a length as to protect the torpedo from the pressure of the water passing the vessel.