"war" head. The former is filled only with water, while the latter bears that powerful charge of gun-cotton. It must be plain that without some form of protection against accidental discharge, a torpedo becomes a dangerous neighbor,

safely clear of the firing ship. Now, when a torpedo is in a submerged tube, the swash of the water, if the vessel be under way, might work this safety propeller loose; and accordingly, as an added precaution, there is a stout shearing pin

of copper which holds the rod in place until the heavy blow of actual contact breaks the pin and drives the plunger against the primer. For target practice, of course, the war head, ordinarily stowed securely below in a special magazine, is replaced by a nose which can be hammered and banged without risk of

dry gun-cotton, which is sensitive, and the initial detonating primer of some thirty odd grains of fulminate of mercury, which, when ignited by percussion, expands to 2,500 times its normal size, and deals to the dry gun-cotton a frightful blow, and that, in turn detonates the otherwise insensitive wet gun-cotton.

ber, is constructed of the finest of compressed steel, which is finally worked down to a thickness of three-tenths of an inch. When fully charged, it becomes itself an explosive body of no mean force, as more than one accident has proved.

The Balance Chamber

Next abaft the air chamber comes the balance chamber, so long a well-guarded secret; and in this water-tight space are the depth-controlling mechanism and some of the important valves. Let us see how the balance mechanism works. Primarily it consists of two parts: a delicately pivoted pendulum or weight, and

can be set to work effectually at depths of from six to fifteen feet. The valve is connected to one of the arms of the pendulum. Now, as the torpedo starts below its designed depth, the external water pressure, pushing against the India rubber diaphragm and the opposing spring, causes the valve rod to move just to the extent to which the water pressure overbalances the set spring; and this motion, in turn, is transmitted to the horizontal rudders. The torpedo is in this way caused to return to its old depth, where the spring again balances the external water pressure, and the rudders return to their normal position. If the

Bainbridge" Class of 16 vessels. Contract speed, 29 knots.

a valve affected by hydrostatic pressure. The pendulum, by its upper arm, is connected with a controlling rod leading directly to the horizontal rudders at the tail of the torpedo, which, moving up and down, control the weapon in a vertical direction. If the torpedo plunges by the head, the pendulum, which moves longitudinally, swings forward and brings the horizontal rudder up, forcing the torpedo toward the surface until the weapon lies horizontal once more. This, however, could not by itself keep the torpedo at a uniform depth; and at this point the hydrostatic valve comes into play. This valve, while open to the influence of the sea, is yet shielded from the water by a stout India rubber diaphragm. The active agent of this valve is a spring, carefully standardized, which

torpedo rises, the spring overcomes the lessened external pressure, and moves the rudders in the opposite direction, thus forcing the torpedo back to its designed submergence. Neither the spring nor the pendulum, in itself, is powerful enough to work the rudders directly against the pressure of the passing water when at full speed. To aid them in this work, there is provided a small servomotor, with air impulse, which, being supplied with air through a small valve controlled by the pendulum and the hydrostatic valve, has ample power to move the rudders.

The Starting Valve

This valve turns the air on to the engines. It is primarily actuated by a small lever which projects beyond the upper

surface of the torpedo, and which is tripped-thereby opening the air ductas the torpedo passes out of the tube. If the air, at this time, however, were turned on full, the engines would be made to race at the violent rate of 2,000 revolutions a minute, which might rack the torpedo and some of the delicate operative mechanisms. To prevent this, there is, just back of the starting-valve lever, a small flat tripper, which, in turn, controls a delay-action valve that checks the passage of air until this tripper has been thrown back by the action of the water after the torpedo has plunged and the

The Engines

The engines are of the three-cylinder Brotherhood type and beautifully compact; and, while the cylinders are less than four inches in diameter and the pistons have a stroke of only three inches, still they develop an energy of fully 56 indicated horse-power. These engines drive directly a single shaft, which, in turn, drives directly only one of the two propellers. The other screw, fitted to a sleeve actuated by gearing that engages the primary shaft, is driven in the opposite direction. This is because the propellers are "rights" and "lefts," so that

propellers are buried. Even now the full pressure of air in the flask is not allowed to reach the engines, for, if such were the case-apart from the tax upon the engines-they would be driven at constantly reduced speed and the travel of the torpedo would be uncertain. To prevent this, a reducing valve yet intervenes between the air supply and the engines. This little valve is an ingeniously contrived affair, in which, by a system of springs and sliding vents and by the opposition of the air supply, the air, acting against itself, is made to feed at a constant and reduced pressure to the engines.

the resultant thrust may be uniform and directly ahead.

The Buoyancy Chamber

Back of the engine space comes the buoyancy chamber, which, as its name denotes, is designed to give the torpedo the necessary buoyancy. This buoyancy, when the air flask is charged at 1.350 pounds, is just zero; and when fully charged, is negative to a considerable extent, showing thereby the weight of compressed air. This chamber, because it must withstand considerable outside pressure, is securely braced by steel rings within. In this chamber, at the bottom