_Her Armament--Engines._--At Fig. 146 is shown the spar and mode of working it. It consists of a long hollow iron cylinder lying on its supports between decks. Its outboard end rests in a kind of trough, and to this extremity the torpedo is fixed. The spar is controlled by means of tackles and a steam winch. The side spars are 18 feet, and the bow spar 32 feet in length. If the hostile vessel is defended by torpedo guards, by means of a mechanical contrivance the torpedo signals the fact, and is not exploded until the vessel has forced the obstructions. The engines of the _Alarm_ are compound, with four cylinders, the condenser being placed between them. There are four cylindrical tubular boilers with an aggregate heating surface of 4,600 square feet. Her speed is about 16 knots. Her upper deck is only 3 feet above the water. She is fitted with an electric light, and also with machine guns on her broadside.[N]
This is undoubtedly a most formidable vessel, both as a ram and a torpedo ship, and if capable of performing all that is expected of her, will prove a valuable addition to the United States Navy.
_Captain Ericsson's Torpedo Vessel "Destroyer."_--This torpedo vessel was devised and built by Captain John Ericsson. The _Destroyer_ is 130 feet long, 11 feet deep, and 12 feet beam, extreme; both ends of her hull are precisely alike, and terminate with very fine wedges. The rudder is attached to a vertical wrought iron post welded to a prolongation of the keel, just abaft the propeller, as shown at Fig. 147. The tillers consist of thin plates of iron riveted on opposite sides of the rudder, a few inches from its bottom. These tillers are operated by straight rods connected to the pistons of horizontal hydraulic cylinders of 5 inches diameter, which are attached to the sides of the keel. The steering gear by the above arrangement is placed 10 feet below the water line, while the top of the rudder is 6 feet below the same, and thus perfect security is afforded to this most important feature of a torpedo vessel. The intention of the designer in constructing this vessel is to render her so far impregnable, that in attacking bow on she can defy the opponent's fire, at the same time offering absolute protection to her commander and steersman, and also protecting the base of her funnel. The leading feature of the construction of the hull of the _Destroyer_ is its being provided with an intermediate curved deck, which extends from stem to stern, and which is composed of plate iron strongly ribbed, and perfectly water-tight. This intermediate deck supports a heavy solid armour plate, fixed transversely to the line of keel, and 32 feet from the bow, inclined at an angle of 45°, and supported on its after side by a wood backing 4 feet 6 inches in thickness. Behind this formidable shield the steering wheel is manipulated, a wire rope extending from its barrel to a four-way cock placed near the stern, by means of which water pressure is admitted alternately to the hydraulic cylinders, previously mentioned, the motion of whose pistons actuate the rudder. The lower division of the vessel is ventilated by powerful blowers, and contains the machinery; it also affords a safe retreat for the crew during the attack. The upper division is filled with blocks of cork, excepting a small part near the bow, occupied by the aforesaid armour plate and wood backing.
