and integrity are vitally important. As merchant ships habitually, though not invariably, lie at a dock when in port, while menof-war commonly ride at anchor, the sides of merchant ships are 'clearer of projecting obstructions than those of men-of-war, the guns of the latter alone often proving an embarrassment in going alongside a dock or another vessel.

Sailing Ships (Plate 5), which a few years ago seemed likely to disappear from the seas, are increasing in number, and appear to be entering upon a new, though limited, career of usefulness in the transportation of non-perishable cargoes. They are often equipped with engine power sufficient to drive them at a moderate speed when the wind fails.

Naval Aviation is yet in its infancy and no one can say what lines of technical development it is to follow. Whatever these lines may prove to be, the resulting machines must be small, compact and strong, capable of being assembled and disassembled simply and quickly. They must stow in a small space, must be easily handled for launching and hoisting in, even under unfavorable conditions of weather, and must be fitted to withstand the severe strains incident to landing on rough water and riding out a gale if necessary. These requirements are radically different from those involved in the design of land planes and far more difficult of realization. They account fully for the backwardness of naval, as compared with military and commercial aviation.

The principal fields of Naval Aviation are Scouting, Bombing, and Spotting (Fire Control).

In Scouting, sea-planes, sent out either from individual fighting ships or from specially designed "Sea-Plane Carriers accompanying the fleet, will cover a wide area of vision, keeping in touch with the commander-in-chief by wireless telephone, and giving notice of the appearance and the movements of an enemy force many hours before contact can be made in any other way. Attacks by bombing will be directed not only against capital ships, but aganist destroyers and submarines. Planes of special types will carry torpedoes to be launched at high speed and from considerable elevation. Finally, spotting by air-planes or by captive balloons will make it possible to direct the fire of the heavy guns against targets far beyond the ship's horizon.

CHAPTER II.

THE HULL AND FITTINGS OF A SHIP.

The principal parts of the hull of a modern ship are named below, and the locations of many of them are shown on Plates 6, 7, 8. These are views of the midship section, bow and stern of a battleship.

The Keel in a large ship is usually composed of the outer keel, the inner keel, the vertical keel, and the middle strake of the inner bottom plating, called the keelson, with their accompanying angle bars. In some merchant ships a vertical outside keel, or bar keel, is fitted. At its forward end the keel joins the stem, which is of great strength, and at its after end joins the stern-post, also very strong and arranged to carry the propellers and rudder.

To the keel are attached the frames, built up of main frame bars, floor-plates, and reverse-frame bars, all of which are strengthened and stiffened by longitudinals of various types. To the framing, the outside or shell plating is secured, the garboard strakes being adjacent to the keel plates and the sheer strakes being adjacent to main or upper deck beams.

An inner bottom is fitted on all large ships; this extends up the ship's side to the armor shelf on armored ships, and to the margin plates on other vessels.

It is subdivided into small compartments by water-tight floors and longitudinals, so that leakage is reduced to a minimum if the ship touches bottom. The frames near the bow and stern are sometimes spaced more closely than elsewhere to provide local strength, and breast hooks, panting stringers, transom plates and counters are fitted for like reasons.

Bulkheads are used to vertically subdivide the ship's interior into water-tight compartments for the preservation of buoyancy and stability; oil-tight bulkheads are fitted to form the necessary fuel oil tanks, and non-water-tight bulkheads are fitted to provide stowage and living spaces where water-tightness is not essential.

Decks are used primarily to provide shelter, working spaces and living quarters; and secondarily to horizontally subdivide the