_Armament of the "Destroyer."_--The _Destroyer_ is to be armed with torpedoes somewhat similar to the projectile torpedo, drawings of which were submitted by Captain Ericsson, the inventor, to Emperor Napoleon III. in 1854. The present weapon is composed of a solid block of light wood, the explosive charge being contained in a metallic vessel inserted at its forward end. Instead of being circular, as was the case with the original torpedo, its transverse section is square, with parallel top and bottom and vertical sides, forming very sharp wedges at both ends, cased with steel plates. The extreme length of the _Destroyer_ torpedo is 23 feet. Ignition is effected by means of a percussion fuze placed in the head of the weapon. _Operating the Torpedo._--The method of operating the torpedo is that of inserting it into a horizontal tube near the bottom of the vessel, provided with valves for keeping out the sea during the process of insertion, as shown at Fig. 148. When near the hostile vessel, this valve is opened, and the torpedo expelled by a piston actuated by steam power, the expulsion being effected without recourse to gunpowder or other explosive agent. The area of the actuating piston of the _Destroyer_ is 314 square inches, while the sectional area of the projectile is only 196 square inches; this difference in size of the two areas is a special and important feature of the invention, as will be understood from the following: the tension of the acting medium in the _Destroyer_ exceeds 200 lbs. per square inch, therefore the torpedo will be pushed out by a force of (314 × 200) / 196 = 320 lbs. per square inch, and as the distance passed by the piston while impelling the torpedo is 30 feet, an energy of nearly 2,000,000 foot-pounds will be imparted to the projectile. When making an attack, it is intended that the vessel should at the instant of firing her torpedo reverse her engines, this retrograde motion being greatly assisted by the recoil, which must attend the discharge of a body weighing some 1,400 lbs. impelled by the aforesaid enormous force, and moving through a distance of 30 feet before reaching the water.[O] Certainly this new system of submarine attack seems feasible, but it has yet to prove, in common with all other new inventions, whether its theoretical capabilities are also practical ones. At Fig. 149 is shown a general view of this novel torpedo vessel under weigh. [Illustration: THE "DESTROYER" TORPEDO SHIP. PLATE XLVI] _Torpedo Boats._--In offensive torpedo warfare, whether using the spar, locomotive, or towing torpedo, especially in the case of the former class of submarine weapons, to ensure a successful attack it is absolutely essential to operate those weapons from steam boats, which are capable of fulfilling as near as possible the conditions herein enumerated:-- 1.--They should be capable of steaming at least 18 knots per hour. 2.--Their engines should be noiseless, and easily managed.