_General Description of the Torpedo._--At Fig. 122 is shown a longitudinal section of a Lay torpedo boat constructed and provided with guiding and controlling apparatus, and with means for propelling it by ammoniacal gas. Fig. 123 is a horizontal section of the same; _A_ is the hull or body of the boat, which has conical ends _A_^{1}, _A_^{2}, and is formed of thin plate iron, or steel, or other suitable material. The section in the end _A_^{1} forms the magazine containing the charge of dynamite or other explosive material; _A_^{3} is the section containing the gas reservoir or holder; the compartment _A_^{4} contains the apparatus for holding and paying out the electric cable; the compartment _A_^{5} in the end _A_^{2} contains the motor engine, the steering apparatus, and other parts to be hereinafter described. All of these compartments or sections are separated from each other by means of air-tight bulkheads _A_^{6}. The torpedo boat may be propelled by means of a single screw, double screw, or two screws. In the latter method, which is shown at Figs. 122 and 123, the propellers _B_ and _C_ are made to revolve in opposite directions; the shaft _D_ of the propeller _B_ is hollow or tubular, and the shaft _E_ of the screw _C_ passes through the same; these screws are actuated by an engine shown at _F._ _H_, _H_ are the horizontal rudders, or side wings, two forward and two aft; these wings are mounted on shafts or spindles passing transversely through the boat; these rudders may be set to occupy a horizontal position, or a more or less inclined position in the proper direction, to cause the submerging of the boat by the action of the water on the said rudders as the boat moves forward, and they are adjusted before starting. _N_, _N_ are two guide rods, one aft and one forward, which project up from the boat to enable the operator to determine its position at any part of its run, and in the case of a night attack they are provided with lights; the said rods can be raised or lowered at the will of the operator. _Q_ is the electric cable, which affords a medium of communication between the operator on shore, &c., and the torpedo boat, whereby it may be started, stopped, steered, fired, and has her position ascertained; this cable is carried in the boat in a coil arranged longitudinally in the air-tight chamber _A_^{4} in the reel frame _R_, and is payed out as the torpedo progresses through a tube _S_, projecting aft under the boat and beyond the rudders and propellers, so that the said cable will not be fouled by the same; or it may be payed out through a hollow shaft in the centre of the boat. One end of this cable is connected to a keyboard at the station on shore or on board of the ship or other structure from which the torpedo boats are controlled. This keyboard is provided with a suitable battery or other means for generating the electric current, as hereinafter described.