upwards, and under the heavy weights of the barbettes and the engines. The third class is fitted under the main transverse bulkheads (the inner bottom being continuous), and at intervals between (see Fig. 52). The bracket frames are fitted to the remainder. In one ship out of a total of 780, 456 were solid, 180 were watertight, and 144 were bracket frames.

The bracket frame is built up as shown in Fig. 17. Deep angles, 5 in. x 3 in., are worked to the outer and inner bottoms, and to these in each bay are riveted two bracket plates, 15 lbs. (in.), with their inner edges stiffened by a 3-in. flange. These are connected to the vertical keel and longitudinals by pieces of angle 3 in. x 3 in.

The plate frame (Fig. 17) consists of a 15-lb. plate connected to the inner bottom, vertical keel, etc., by angles 3 in. x 3 in., and to the outer bottom by angles 3 in. x 3 in. Each plate is stiffened by an angle bar, and holes large enough to enable a man to pass through for inspection purposes are cut to lighten the plate.

The watertight frames (Fig. 17) with the vertical keel and watertight longitudinals divide the double-bottom space into a large number of watertight compartments. The frame is made of 15-lb. (3-in.) plating under the transverse bulkheads, and 12 lbs. (in.) in other places. The space is filled in solid with the plate, and staple angles are worked round the top and bottom as shown. This enables a tight fit to be made, and the whole is closely riveted for watertight work and caulked. These frames are specially stiffened, as shown, by three channel bars in the first bay, one channel and two angles in the other bays up to No. 4 longitudinal. This extensive stiffening is fitted to make the framing strong enough to stand the severe strains which exist when such a heavy ship is in dry dock. Recent ships are being fitted with docking keels at the side, as in Fig. 13. In these cases the stiffening of the watertight frames is not so extensive as described above.

Extra frames, both longitudinal and transverse, are worked under the engines in order to provide a rigid support.

Framing behind and above Armour.-The character of the framing behind armour is governed by the necessity of providing a rigid support to the armour. For armour 6 in. and 7 in. thick, the framing is formed of 10-in. zed bars, 24 in. apart, with fore-and-aft stiffening girders. For armour 9 in. thick, a more massive support

is necessary, and the framing is formed of plate frames 15 in. deep, 24 in. apart, with angles on the edges as shown in Fig. 18. There are fore-and-aft girders in addition, as shown. In either case the frames are well supported by bracket plates at the heads and heels.

The framing above the armour, between the main and upper

decks, consists of 6-in. zed bars 4 ft. apart, with 4 in. x 3 in. angles between. In ships with an armoured battery, as Fig. 13, the framing is made stronger to form a support for the armour.

Framing at the Ends of Ship.-The above description refers to the framing over the length of double bottom, or about twothirds the length. The ends of the ship are framed on a somewhat

different principle. Here the longitudinal strength is of less importance, and the main function of the framing is to stiffen the outer bottom plating. Accordingly we find that the transverse framing is continuous either side of the vertical keel to the protective deck, and this framing is more closely spaced, viz. 3 ft.

The vertical keel is still continuous, but not watertight, and the frame consists of a vertical floor-plate with outer and inner angles to the bilge. Above this the frame is formed of a 6-in.

zed bar. In Fig. 19 the top of the floors is covered in with a watertight platform, and the zed bar is passed through with the inner flange cut away. This makes the watertight work at the ship's side more readily performed than if the complete zed bar went through (see Fig. 41).

As before stated, the vertical keel is continuous from end to end of the ship, but the five longitudinals on each side, which extend over the length of double bottom, are altered in character at the ends. They are either twisted round to connect on to a

fore-and-aft bulkhead or a flat, or tapered down to one of the forms shown in Fig. 19. The lower one is simply formed by an intercostal plate between each pair of floors, and the upper ones are each formed by a 10-in. zed, slotted over each frame, with a continuous 3 in. x 3 in. angle on the inside. Fig. 20 shows in detail how a longitudinal is tapered down over three frame spaces to the zed bar form. This is necessary to avoid This is necessary to avoid any discontinuity in the fore-and-aft strength.

Above the protective deck the transverse framing is still 3 ft. apart, and is formed of 6-in. zed bars. In recent ships armour of varying thickness is fitted at the forward end, and behind this the frames are 2 ft. apart to well support the armour. At the extreme forward end, before the collision bulkhead, and below the protective deck, the frame consists of a solid plate connected

by angles to the outer bottom, etc. This plate is well lightened by holes.

It will be noticed that, although the inner bottom proper stops at about one-sixth the vessel's length from each end, yet an inner skin is obtained well towards the ends by the provision of the watertight flats forming the floors of the store-rooms, etc. (see Fig. 19).

First Class Cruisers.-Vessels of this type are in some cases of equal or even greater displacement than battle-ships, by displacement being meant the total weight of the ship. The broad distinction between a battle-ship and a first class cruiser of recent design, is that the former has thicker armour with a greater proportion of the side area protected and with a heavy armament of 12-in. guns, while the latter has lighter protection and

armament, but with high speed. The following comparison will illustrate this distinction:

The design of first class cruisers has undergone great alteration in recent years. In vessels of Edgar, Powerful, and Diadem classes

the protection was ob

tained by a thick protective deck near the waterline, in association with the stowage of coal above the deck (see Figs. 21 and 22). The great improvement in the quality of armour, brought about by the Krupp process, made it possible to armour the vessels of the Cressy class with a broad patch of 6-in. armour. This method of protection with thick main and middle decks has been a feature of first class cruiser designs since that time (see Fig. 23).

In the Edgar and Diadem (Figs. 21 and 22) the inner skin is continued up to the protective deck, but in later ships, as Fig. 23, the inner skin is only carried to the upper part of bilge. This gives a larger space