A, A, Bronze conning tower; B, Sighting hood; C, C, Hatches; D, Exhaust from engines; E, E, Torpedo tubes; F, F, Gasoline tanks; G, G, Line of spindle hull; (From Scientific American) sist of a spindle or cigar-shaped hull of steel plates 65 feet long by about 11 feet greatest diameter. On top of this hull has been built a superstructure, which gives the boat the appearance above water of having an ordinary torpedo-boat hull, with a conning tower mounted in the center. Within the superstructure, designated by G in the cross-section, there are carried eight gasoline tanks, F, having a total capacity of 1,050 gallons; two lubricating oil tanks of 120 gallons total capacity; six high-pressure air tanks formed of 8-inch Mannesmann tubes and containing 21 cubic feet of air at pressure of 2,000 pounds per square inch; and four low-pressure air tanks containing 122 by hydraulic rams, which ease the shock when the boat strikes bottom, and upon which she runs, driven, however, by her propellers, when a good opportunity oc curs. The engine room in the rear of the boat is a marvel of compactness, and when one sees the two 125-horse-power, four-cylinder, White & Middleton gasoline engines, one on either side of a narrow aisle, one wonders how they were ever got in there, much less how they can be made to operate satisfactorily in such close quarters. Yet the fact is they are two of the most reliable pieces of machinery in the boat, and, started, if need be, by the explosion of a cartridge in one cylinder, they will Front end of engine room, showing switchboard and valves controlling flow of water into five ballast tanks (From Scientific American) cubic feet of air at 60 pounds pressure. The pressure is reduced from 2,000 to 60 pounds by means of a Foster reducing valve. The superstructure has a watertight bulkhead across its center, which divides it into two huge water tanks that are the first to be filled when submerging. Another tank (not shown) is located in the center of the boat beneath the storage batteries, M, while the five other ballast tanks, Q, are disposed symmetrically about the bottom of the hull. The diving compartment, its door, and the air lock are shown at K, L, and J; the galley and cabin at H and I, with torpedo tubes projecting from the latter through the hull on each side at E, and a third tube projecting from the engine room through the stern; the conning tower and sighting hood are seen at A and B, while the three hatches are lettered C, and the exhaust pipe of the engines, D. P P are detachable anchor weights; N N a detachable keel; and O O the buffer wheels operated run for hours without giving trouble, seeming to have, apparently, all the reliability of a stationary gas engine. A magneto is regularly used for the ignition current. Directly back of each engine is a 50-horse-power, shunt-wound, Diehl electric motor, which is connected to the engine on one side and to the propeller shaft on the other through friction clutches. Ordinarily, the engine is started by the motor, after which the clutch operating the propeller is thrown in and the brushes are lifted from the motor commutator if a long run is to be made. the battery needs recharging, this can be done while the boat is running by altering the pitch of the screws, thus driving the boat more slowly and using the surplus power to run the motors as dynamos and allow them to recharge the battery. This consists of sixty cells of Gould battery weighing 75,895 pounds, and capable of furnishing 1,680 amperes, or 852 horsepower, for three hours, which gives the If |