_Propulsion._—On the surface the vessel is propelled by a 160 h.p., single screw, four-cylinder, Otto gasoline engine, capable of giving a speed of 8 knots, while when submerged it is driven through the water by a 70 h.p. electric waterproof motor giving a speed of 7 knots. The radius of action at the surface is about 400 knots, while the storage batteries have sufficient capacity for a speed of 7 knots on a four hours’ submerged run. Gearing is provided for the charging of the batteries by using the motor as a dynamo, and running it from the gasoline engine when at the surface, and from connecting the propeller either to the engine or the motor; these operations are effected through clutches. Switchboards and switches are provided for the safe and efficient distribution of the electric current throughout the vessel. The lighting system consists of portable incandescent electric lamps, together with several ports and openings in the hull to admit the outside light. The hull is circular, in cross sections, and is divided by the watertight bulkheads into three separate compartments. There is also a thorough subdivision of the bottom and every precaution is taken to localise any injury to the hull which might threaten the buoyancy. In the forward compartment is one torpedo expulsion tube, located at the extreme forward end of the vessel, opening outward two feet below the light water-line. The tube is placed with its muzzle in the nose of the craft and its axis inclined somewhat to the longitudinal axis of the vessel. The muzzle of the tube is closed by a watertight door, and this can be lifted from within for the discharge of the five Whitehead torpedoes, each 11 feet 8 inches long, which are carried in the interior. One torpedo is placed in the tube, and the other four are placed side by side above the storage batteries. When the first torpedo is fired a sufficient amount of water to compensate for the loss of weight is automatically and almost instantaneously admitted into the tube, causing only a slight change of time for a few seconds. Such compensation is necessary, as the submarine boat is lighter than the amount of water it displaces and any alteration in its weight tends to send it up to the surface or down towards the bottom. When the second torpedo is placed in the tube the water is run into a special torpedo compensating tank; of these tanks there are four, and they are filled as each torpedo is fired. When the last torpedo has been ejected the expulsion tube is filled with water and is kept thus until the end of the run. Besides the torpedo tube there is in the forward compartment a series of air flasks, a gasoline tank of 850 gallons capacity, and a trimming tank.