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aft, was constructed. The secondary armament, which had con- sisted originally of II si-in. guns, was retained, with the exception of one gun; the remaining 10 guns being rearranged. Four sets of triple 2i-in. torpedo tubes were fitted on the upper deck aft, and one pair each side on the upper deck forward.

After these alterations were completed, the ship was tried and commissioned in July 1917, a speed of 31^ knots being obtained with 94,000 S.H.P. at 330 revolutions. From the speed point of view the great advantage of size and length is clearly shown in these ships compared to T.B.D.s, since with about three times the H.P. of a destroyer it is possible to drive a ship of nearly 20 times the displacement at the same speed. This in smooth water; in anything of a head sea the T.B.D.s are left behind altogether by the great ships (see Table V.).

Light Cruisers. Following upon the previous light cruisers of the town classes, a very important departure was made in the light cruiser design in the programme 1912-3, when the " Arethusa " class (see fig. 14) was designed by Sir Philip Watts. The importance attached to speed was specially brought out in this design, and it was decided to install very powerful machinery of 40,000 S.H.P. and this could only be achieved by adopting engines and boilers closely approximating to those hitherto used only for destroyers.

In conjunction with high speed a good armament was provided, consisting of two 6-in. and six 4-in. guns, though in the original design the armament consisted entirely of 4-in. guns. The ship's sides up to the level of the upper deck were protected by a high tensile plating varying from 2-in. to ij-in. and i-in. in addition to the i-in. shell plating. This arrangement of plating also greatly added to the strength and stiffness of the ship. Further particulars of the class are given in Table V.

The " Arethusa " and other light cruisers were in the action off Heligoland on Aug. 28 1914.

In the 1913-4 programme the " Calliope " class, slightly larger vessels than the " Arethusas," but with the same power, were decided upon, the designs being made by Sir E. d'Eyncourt. After considerable discussion regarding the merits of mixed or homogeneous armament, it was decided to give these vessels two 6-in. guns, both on the centre line placed aft, and eight 4-in. guns. The protection consisted, as in the previous design, of a belt with a total thickness of approximately 3 inches. Most of this class had practi- cally the same machinery as the " Arethusa," but Parsons geared turbines were installed in two of them, the " Calliope " having four shafts and the " Champion " two shafts. This was at the time a very important experiment, the putting of 20,000 H.P. through gearing being a very bold departure from anything which had been hitherto contemplated. The final results obtained with "Champion" were, however, excellent, and she obtained a speed of 295 knots with 337 revolutions and about 41,000 S.H.P., this speed being slightly in excess of any of the other vessels of the class at corresponding displacement.

The " C " class are the first ships, other than battleships, to have superposed guns on the middle line, a sort of spoon-shaped bulwark being fitted to protect the crew of the lower from the blast of the upper gun firing over them.

For the subsequent vessels of the " C " class reference should be made to the tables, which show a gradual growth in size and power of armament; "Ceres" class (fig. 14) finally having a length of 425 ft. and a beam of 43 ft. 6 in., and a normal displacement of about 4,200 tons. These vessels carried five 6-in. guns, all on the centre line.

FIG. 15.

The next class were the " D's " (figs. 15 and 16), the general arrangement and protection of which followed that of the " Ceres," except that six 6-in. guns were carried on the centre line instead of five. The power was only slightly increased in these ships over the previous classes, but the revolutions were reduced to 275, all these later classes having the twin-screw geared arrangement, and ajthough the displacement of the " D's " increased to 4,650 tons, tfie addi- tional length and the reduction of revolutions enabled the speed of close upon 30 knots of the whole class of light cruisers " C's " and " D's " to be maintained.

In addition to these light cruisers, which were all to Admiralty design, two vessels the " Birkenhead " and " Chester " built at Messrs. Cammell, Laird's for the Greek Government, were pur-

chased in 1915. These vessels were considerably heavier than the "C " class and more closely resembled the British " Chatham " class. They carried an armament of ten sJ-in. guns. The boilers were modified to burn only oil in the " Chester," instead of coal and oil as in the " Birkenhead," and the resulting increase in power to 31,000 gave the former a speed of 26 J knots.

Designs were prepared in 1915 of the " Raleigh " class (figs. 17 and 1 8), a considerably heavier type of light cruiser, more especially suited for ocean work in any part of the world. They were to have a speed of 30 knots and a large radius of action. Various armaments were considered, and it was finally decided to adopt an armament of seven 7'5-in. guns with twelve 3-in. (four being on high-angle mountings). Five of the big guns were placed on the centre line,

FIG. 17.

and the other two were on the broadsides amidships. The bow and stern guns were superposed, thus giving a fire of four guns, both ahead and astern, and six guns on either broadside. These ships were originally designed to burn oil and coal, but the coal-burning boilers were subsequently altered in three ships of the class to burn a larger amount of oil, the original power of 60,000 S.H.P. on a four- shaft geared turbine arrangement being thus considerably increased up to about 70,000 shaft horse power.

These vessels also differed from the light cruisers referred to above in having modified bulges as protection against under-water attack. The protective plating was similar to that of the other light cruisers. One of these ships, the " Cavendish," was altered into an aircraft- carrier, and renamed " Vindictive."

Monitors (see Table V.). The first vessels of this type to be added (or reintroduced) to the British navy were the three ex- Brazilian river monitors built by Messrs. Vickers, Ltd., and taken over by the British Government in Aug. 1914^, and renaned " Hum- ber," " Mersey " and " Severn." The particulars of these vessels are given in the table, from which it will be seen that the armament consisted of medium-calibre guns, viz. 6-in. and 4'7-inches. These vessels, though designed for river service, did very good work in the war, both on the E. -African and Belgian coasts.

The need for vessels of the monitor type mounting heavy guns soon became apparent, and in Nov. 1914 it was decided to prepare designs of monitors of more substantial structure for sea-going service, but of light draught, with good protection and carrying some heavy guns, the light draught combining the advantages of being able to go close inshore and greatly reducing the risk of being struck by a torpedo.

The earliest design was that of the 14-in. gun monitors, four in number, which was commenced in 1914. Four twin-mounted 14-in. guns and mountings were available, and with the very simple form of structure adopted, these vessels were designed and built in six months. They were quickly followed by the 12-in. monitors, which were of similar design but carried pairs of 12-in. guns, taken from older battleships. These vessels were also built in about six months. They all had a complete bulge of a form which was of simple con- struction, with an air space outboard and a water space between that and the ship proper.

Following on the 12-in. monitors, early in Jan. 1915 two more vessels were ordered, mounting a pair of 15-m. guns. For these ships, internal-combustion engines, which were well under way, but designed for another purpose, were installed. These vessels were named the " Marshal Ney " and " Marshal Soult."

In Sept. 1915 two improved 15-in. monitors were ordered and named the "Erebus" and "Terror" (figs. 19 and 20). These were of finer form, of more horse power and a speed of 14 knots.

Following the earlier 15-in. monitors, some much smaller vessels, each carrying a g-2-in. gun, were designed, and others again which carried 6-in. guns. A good many of both large and small monitors went out to the Dardanelles in the early part of the war, and did very good work, and for a long time they seemed to bear a charmed life, as they enioyed complete immunity from torpedo attack. Later, however, the " Erebus " and " Terror " were both torpedoed ; the latter received three torpedoes, two hitting forward of the bulge with severe damage resulting; the third, which hit the bulge itself, did very little damage. The former ship was hit full amidships by a distance-controlled boat carrying a very heavy charge, but the bulge gave her complete protection and both ships were quickly re- paired. It is interesting to note in this connexion that some of the old