First, fewest, and heaviest are the harbor-defense vessels—monitors and massively walled floating batteries, intended to remain in harbors, or close to the coast, as movable forts.
Second, battle-ships—the strongest, most thickly armored, heavily armed style of ships that can be made, and still be able to go to sea; but these are not expected to leave their home ports for a long time, nor to go to any great distance unless compelled to do so in actual war.
Third, cruisers. These take the place of the old-fashioned lesser fighting-ships, the seventy-fours, frigates, corvettes, and sloops, and vary greatly in size, model, speed, and power of armament.
Fourth, small, swift, strongly armed but lightly armored, torpedo-boat chasers, small gunboats for use in rivers and shallow coastal waters, despatch-boats, dynamite-cruisers, such as our American Vesuvius, tow-boats, and similar minor craft—the run-abouts of the naval service.
Fifth, torpedo-boats.
The material of all these is steel. Wood is no longer permitted even in the fittings of their cabins, because wood will splinter and burn.
The great hull of a modern battle-ship, as described by Lieutenant S. A. Staunton, U. S. N., which supports and carries the vast weights of machinery, guns, and armor, aggregating perhaps more than ten thousand tons, is built of plates of rolled steel, varying from 1⅜ inches thick at the keel to ¾ inch at the water-line. These are closely jointed and fitted, and bound together with straps, angle-irons, and brackets, so as to make a strong unyielding structure braced in all directions. Then, through the central part of the ship, at least, vertical plates are erected upon the frame and outside plating, which bear a second or inner bottom, thus forming the “double bottom” as high as the water-line, having the space between the inner and outer sheathing separated into a multitude of small water-tight cells, so that an injury to the outside hull would not cause the vessel to leak unless the inner bottom were also punctured.
Throughout the whole length of the vessel, reaching from side to side and from the keel to the main deck, are many steel bulkheads, sufficiently strong to resist the pressure of the water, and communicating only by water-tight doors, so that even were an accident, such as a collision or running upon a rock, or an enemy’s shell, to open a hole through both bottoms, the ship would still float, because the inflowing water would be confined to a single compartment, leaving the rest of the ship dry and buoyant. Nothing less than the blow of a ram, smashing through everything and throwing several compartments into one, would be likely to sink such a ship, and this is one reason why ramming has again become prominent in naval tactics.
THE FIRST SEA-FIGHT OF MODERN WAR-SHIPS.