Before going below the chimney is to be unshipped and all the openings are hermetically closed. Sufficient time is allowed for the motor to cool and for the air to be cleared of the hot gases. The steam engine has to be replaced by the electric motor and water ballast has to be pumped in. At first these operations took at least a quarter of an hour, but the newer vessels of the _Narval_ class are said to be able to disappear beneath the waves in some five moments only. [Illustration: _Photo by_] [_M. Bar_ THE “NARVAL.” ] The armament consists of four 17½ inch Whitehead torpedoes, and there are two Drzewiecki torpedo tubes on each side and towards the upper part of the boat, which launch the torpedoes in the direction of the beam. “As long ago as 1893,” says a French writer, “Mr. Drzewiecki invented a method of firing a torpedo which is quite different from the torpedo tubes commonly used, and which is, therefore, peculiarly suited for submarine vessels. By it the torpedo could be fired at any angle from 30 to 120 degrees from the bow, and experiments with it were carried out in 1894 at Cherbourg. The system may be briefly explained as follows: At the side of the boat a horizontal spar is placed, which works on a hinge at an angle to the bow. The torpedo is fastened to this spar by two pairs of clamps, and when not in use lies along the side of the boat in a recess cut in the side. A swing-out rod, fastened at one end to the spar and at the other to the boat, enables the desired angle for firing to be obtained. A lever worked from inside the vessel pushes the spar and the torpedo away from the side of the boat, and the pressure of the water stiffens the swing-out rod, and by so doing frees the torpedo from the clamps, and opens the air lever which sets the torpedo in motion. It is, therefore, necessary that the vessel should be under way when the torpedo is fired.