All large war-ships are now fitted with tubes, opening near the water-line in various parts of the hull, which form gun-like exits for these terrible weapons, which are set in motion by a puff of gunpowder; but in addition to this every maritime government now has a number (Great Britain has more than 250) of small, swift steamers designed wholly for this purpose and called torpedo-boats. Most of them are a hundred feet or so in length, and intended to accompany the fleet wherever it goes and in all weathers; but some are so small that they may be carried on the deck of a big cruiser. All are made long, low, and narrow, and the speed of many of them exceeds thirty miles an hour. There is almost nothing to catch the wind or show above deck except a pair of short, flattened smoke-stacks, one behind the other; and the steersman stands, with only his head and shoulders visible, in a little box with windows that serves the purpose of a wheel-house. A mere wire railing saves the crew from sliding off the deck, and in action everybody stays below. No weight is carried that can be avoided, and the engines, taking steam from two boilers, are as powerful as can be packed into the space at command. Usually only coal enough for a few hours’ steaming is carried, and every bushel of it is carefully selected as to quality, and is so treated and intelligently fed to the furnaces as to make the hottest possible fire, although never a spark must escape from the smoke-stack to betray the vessel in the darkness. [Illustration: A TORPEDO-BOAT AT FULL SPEED.] Next to speed the most important quality is ability to turn quickly, upon which might often depend the safety of the audacious little craft. Torpedo-boats, however, are designed for a wider service than simply to carry and discharge the frightful weapon from which they take their name. They are to the navy what scouts and skirmishers are to a land army. They form the cavalry of the sea, of which the cruisers are the infantry, and the battle-ships and monitors the artillery arm. They must spy out the position of the enemy’s fleet, hover about his flanks or haunt his anchorage to ascertain what he is about and what he means to do next. They must act as the pickets of their own fleet, patrolling the neighborhood, or waiting and watching, concealed among islands or in inlets and river-mouths, ready to hasten away to the admiral with warning of any movement of the adversary. [Illustration: ONE FORM OF SUBMARINE TORPEDO-BOAT.] It is not their business to fight (except rarely, in the one particular way), but rather to pry and sneak and run, for the benefit of the fleet they serve.