side, thus continuing the inner skin up to the protective deck (see Fig. 26).

Second class cruisers are the smallest vessels of the Royal Navy in which double bottoms are fitted, and in the remaining vessels we have to consider, the valuable element of safety provided by the inner skin has to be dispensed with.

Third Class Cruisers.-In these vessels we have a different set of conditions to consider. There is no double bottom, and the plating, being of small thickness, requires to be well stiffened. For such vessels, therefore, the adoption of the longitudinal system of framing would be unsuitable, and the best method is the trans

verse system. The section of such a ship is shown in Fig. 27, and the arrangement of framing is shown in some detail in Fig. 28. This framing is 24 in. apart throughout. The floor-plate, 10 lbs. (4 in.), extends from bilge to bilge. This plate is slotted out at the middle line to allow the lower bar of the middle line keelson to pass continuously through. The frame bar, 4 in. x 3 in., is continuous from the middle line to the protective deck on either side, and the reverse bar, 3 in. x 3 in., is continuous from the deck on one side to the deck on the other side, running along the top of the floor-plate as shown. Some difficulty is experienced in making the bunker bulkhead watertight where the frame, etc., pass through. In order to make a

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satisfactory job, the bulkhead is stopped at the reverse bar, and a dished plate is fitted below between each pair of frames as shown. The frame above the protective deck is formed of a 4-in. zed

bar.

The longitudinal framing consists of a middle line keelson and two side keelsons on either side. The middle line keelson is

formed by intercostal plates, 15 lbs. (3 in.), between adjacent frames, connected to the floor-plates by angles 2 in. x 2 in. These plates project above the floors and connect to two continuous angles, 3 in. x 3 in. The lower edges of the intercostal plates connect to a continuous angle, 3 in. x 3 in. There are in addition two continuous rider plates, each 9 in. x 12 running along the top of the floors. The side

lbs. (in.), keelsons are

intercostal, with a rider plate on top as shown. Below the protective deck, before and abaft the machinery space, the frame is formed as shown in Fig. 28, with a 4-in. zed bar connecting on to a 10-lb. (in.) floor-plate. Above the protective deck the frame is formed of a 4-in. zed bar.

Sloops.-A large number of small vessels, about 1000 tons displacement, called sloops, are employed on foreign stations. They carry some sail-power, and are sheathed

with wood and copper for the reasons given above.

COAL

COAL

A section of such a ship is given in Fig. 29. One feature of these vessels is the absence of any protective deck. In the side bunkers, however, there is a division, at about the level of the waterline. It is intended that the coal should remain in the upper part of the bunker as long as possible, in order to serve the purpose of protection, and to assist in preserving the stability if the side were pierced.

FIG. 29.-Sheathed sloop.

These ships are framed on the transverse system with the frames 24 in. apart. Below the watertight division in the bunkers a frame bar, 4 in. x 3 in. (Fig. 30), is worked from side to side. Between the coal-bunker bulkheads a floor-plate is worked, 10 lbs. (4 in.), with a reverse bar, 3 in. × 2 in., on the upper edge. A 3 in. x 2 in. reverse bar is connected to the frame bar above the bulkhead. Above the bunker division the frame consists of a 4-in. zed bar. It will be noticed that the bunker division severs the transverse frame completely, and to maintain the continuity of the transverse strength bracket plates are worked as shown.

The middle line keelson (Fig. 30) is formed by an intercostal plate, 15 lbs. (3 in.), between each pair of frames, with staple angles, 3 in. x 3 in., connecting to the flat keel and to the floors. The intercostal plates project above the floors and connect to two continuous angles, 3 in. x 3 in. An intercostal keelson is also worked on either side.

Torpedo-boat Destroyers.-The essential feature of this type of vessel is speed, and every effort is made by careful design, high quality material and careful workmanship, to keep down the weight of the hull structure to the lowest amount possible. Sections of a typical destroyer are given in Figs. 31 and 32 the

first showing the transverse portions of structure, and the second those portions which give longitudinal strength.

The ship is framed on the transverse system with a frame, floor, and reverse frame. Deep frames are fitted at intervals. There is a middle line intercostal keelson with continuous angles at the top and bottom. The engine and boiler bearers are so arranged as to assist materially in providing longitudinal strength

to the structure. Flanging of plates is largely adopted to save the weight of connecting angle bars. The deck is of special importance, as it is severely strained if the ship is subjected to a sagging moment. In this case the deck between the beams is liable to buckle, being of thin plating, and in order to enable it to effectively stand the strains, it is well stiffened by fore-and-aft girders. Deep beams are fitted at intervals.