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 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

available for coal. In recent cruisers, also, the upper coal-bunker bulkhead has been dispensed with, to increase the facility of transporting the coal.

Many first class cruisers, including some of Edgar class and all the ships of Diadem, Powerful, and Cressy classes, have been constructed with the bottom sheathed with wood and copper. This has been done because these ships are intended to keep the sea for long periods without docking. The sheathing of copper is found to be the best anti-fouler. In building a ship, however, sheathed instead of unsheathed, certain sacrifices have to be made,

viz. increase of first cost and reduction of measured mile speed. We shall return to this subject later when dealing with methods of preventing fouling.

Framing of a First Class Cruiser.-Taking the framing of the cruiser whose section is shown in Fig. 23, we notice that the vertical keel is 42 ins. deep and 25 lbs. ( in.). This depth is maintained over the whole length of the ship except in the engine-room, where the depth is about 5 ft. The two top angles are 3 in. x 3 in., and the lower angles 4 in. x 4 in. There are four longitudinals on each side, of which the second and fourth

ARMOUR

are watertight. These extend over the length of the double bottom, i.e. about half length of ship.

The transverse framing in the double bottom is similar in character to that already described for a battle-ship. The framing behind the 4-in. armour is formed of 8-in. zed bars, with a foreand-aft stiffening girder. The remainder of the framing, both longitudinal and transverse, is generally similar to that adopted in battle-ships as described above.

In this type of ship, in consequence of the great power of the engines, the framing in the engine-room is built exceedingly strong. We have noticed that

here the vertical keel is 5 ft. in 1
depth, and extra fore-and-aft
girders are worked, in addition
to the ordinary longitudinals, to
give a rigid support to the
engines.

Second Class Cruisers.The majority of vessels of this type are sheathed with wood and copper, being intended for service on foreign stations, where the ships have to keep the sea for long periods. A typical

W.T.

W.T.

COAL

FIG. 24.-Sheathed second class cruiser.

section of a second class cruiser is given in Fig. 24. We notice that the protective deck and the coal above constitute the protection. The advantage of a double bottom is retained, but it is of less extent than in the previous cases considered, only extending to the coal-bunker bulkhead.

The construction of this ship is shown in Fig. 25. There is a continuous vertical keel 36 in. x 17 lbs. (16 in.), with double angles along the top 3 in. x 3 in., and double angles along the bottom 3 in. × 3 in. There are two longitudinals on either side, 15 lbs. (in.), the second one being watertight. The double bottom extends over the length of the engine and boiler rooms, or rather less than half length.

For the transverse framing, the outer bar is 7 in. × 3 in., and is continuous from the keel to the protective deck, about 4 ft. apart. Within the double bottom, flanged bracket plates are worked as shown, with watertight frames and solid plate frames as

necessary. A large 10-lb. (in.) bracket is worked at the sides of the double bottom to ensure proper continuity of the transverse strength. Between the second longitudinal and the protective deck, a reverse bar, 2 in. x 2 in. (inadvertently omitted in Fig. 25), is worked on the back of the frame bar, and there is also a longitudinal girder, as shown. Above the protective deck the frame is formed by a 6-in. zed bar. The framing at the ends is

generally similar in character to that of battle-ships with floors, etc. This framing is worked every 3 ft.

The protection is obtained by a protective deck 1 in. on the flat, 3 in. on the slope, and the disposition of the coal is arranged to afford as much protection as possible.

The second class cruisers of the Arrogant class are intended for use as Fleet Cruisers, and these vessels are not sheathed. The protection is obtained by a thick deck and side coal bunkers as usual. An extra longitudinal bulkhead is worked below at the

1 Arrogant, Vindictive, Furious, Gladiator.