Some of the contrivances to which naval engineers are directing their attention are called _outrigger torpedoes_. A small swift steamer has an outrigger or pole projecting twenty or twenty-five feet from one side; a torpedo case is fastened to the outer end of the pole, and a concussion-fuse is fitted to it, or an electric-wire extends along the pole. When the steamer has cautiously and silently brought the torpedo (which may be either a little above or a little below the surface of the water) under the bottom of an enemy's ship, the composition within it is fired by the fuse or current, and the explosion left to do its destructive work. It is supposed and intended that the distance of twenty or twenty-five feet between the steamer and the torpedo will keep the former free from peril. Some torpedoes are self-explosive on touching the enemy's ship. One variety is a hollow iron cone, kept at a certain depth under water by a mooring chain; the cone contains from one to three hundred pounds of powder; above this is an air-space to give buoyancy, over this a small apparatus of chemicals, and at the top of all a projecting rod. If the bottom or lower part of the hull of a passing ship happens to strike against this rod, a kind of trigger explodes the chemicals and then the powder--with what result the evil fates are left to determine. Another kind, not self-explosive, is ignited from the shore. The torpedo-cone is moored as in the former case, and electric wires extend from it to a battery on shore. When an enemy's ship is seen to be passing just over the torpedo, a shock is sent from shore, and the demon of mischief explodes. A self-exploding torpedo has the disadvantage of destroying one's own ships occasionally, by a mishap; while the others are with difficulty coaxed to explode just at the desired instant. Six or eight years ago, the public were a good deal mystified about Captain Harvey's torpedo, what it was and what it was intended to accomplish. It was described as an oblong box, to be towed beside a steamer by means of a long rope. It was charged with a powerful explosive composition; it had projecting levers at the top, a tube containing a detonating compound, and a bolt that could be pressed down upon the detonator by the levers. Towed out to its place by a steamer of great speed, it is brought close to the side of a hostile ship, the tow-rope is then slightly slackened, the torpedo sinks a little, and as the rope tightens again, it comes with a violent blow against the ship's bottom, exploding and making (theoretically at anyrate) a big hole in the ship's hull: a short process, but by no means a merry one. (The English authorities are said to be manufacturing Harvey's torpedoes at Woolwich Arsenal at the time we write, June 1877.)