Perhaps the most formidable _ocean-going_ torpedo vessel yet constructed is the American despatch-vessel _Alarm_, designed by Admiral David Porter, of the United States Navy. It is 172 feet long, including a ram of twenty-seven feet in length. One of her special qualities is the power of launching torpedoes from almost any point, from cylinders specially constructed for the purpose, that at the bow being thirty-two feet in length. A torpedo-boat, built by the Messrs. Yarrow, of Poplar, for the Russian Government during the late war, appears to have special merits. It is built of light steel, with what is called a “whale-back”—a semi-circular covering, which resists any ordinary shot and throws off any sea whatever. The funnel is not in the centre, but towards the side, in order not to interfere with the steersman’s view nor with the torpedo boom. It has a boom which can be lowered in the water, the torpedo being submerged ten feet before it is started off on its deadly errand. And, finally, it can be projected from the stern, which gives it a splendid chance of leaving before the final explosion. In the late Turko-Russian war torpedoes were often attached to logs of wood or clumps of brushwood, and floated into the stream of the Danube. These often attracted little attention; and when they came into contact with any obstacle the mine exploded by means of percussion, the blow being delivered by a projecting arm or other contrivance driven back upon some detonating substance within. The Harvey torpedo, one of the leading types, consists of a stout wooden casing, strengthened on the outside with iron straps, and containing a metal shell, which holds the powder charge. The largest size of this weapon measures 4 feet 6 inches in length by 2 feet in depth, and 2 feet 6 inches in width, and carries 100 lbs. of dynamite. The torpedo is fired by being brought into hugging contact with an enemy’s ship, when one or other of two projecting levers acts upon an exploding bolt causing the ignition of the charge. The exploding apparatus consists of a tube containing a chemical agent and a bulb holding another. The nature of these chemicals is such that when they combine violent combustion ensues, which explodes the charge. These torpedoes are towed at the end of a long hawser, connected to a spar, so arranged that the torpedo itself, instead of following immediately in the wake or trail of the vessel towing it, diverges in the same manner that an otter float does: from which device Captain Harvey took his idea. Attached to the torpedo are two large buoys, for the purpose of supporting it when the vessel is not moving through the water, or when the towing-line is slackened. Another variety is fired by electricity.