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shell ranging 26,000 yd. at 40 elevation. The weight with mounting is 92 tons. The Armstrong railway mounting for this gun is shown in fig. 41. The gun has no cradle; to adapt it for the railway mount- ing a trunnion ring is shrunk on and a balance weight added to the breech. It is mounted on a small upper carriage, recoiling on the main carriage; the recoil is checked by a hydraulic buffer, and the upper carriage returned to the firing position by springs.

The main carriage traverses on a roller ring on the upper surface of the platform girder which is of the usual type, supported at each end on a pivot carried by a six-wheeled bogie truck, the centre pair of wheels being flangeless.

Four outriggers, which are shown in the raised position in the plate, are pivoted to the sides of the main girder. Before firing, the main girder, with the gun and carriage, is lowered by means of hy- draulic jacks which are embodied in the pivots which support the ends of it, so that it rests upon the sleepers of the permanent way. The outriggers are swung out, stayed, and bedded in the ground, and the gun is ready to fire. The operation takes half an hour.

This mounting requires no preparation of the permanent way; the gun can be fired from any point in the open line, at the rate of about one round in 50 seconds. The outrigger system would require modification to admit of heavier guns than the 9-2-in. being fired from it; even with this gun reduced charges have to be used when firing across the rails at angles of elevation below 15 degrees.

It should be noted that all outrigger mountings block both lines of rail when in position, so that no traffic can pass. This is one argu- ment in favour of the curved-siding system.

The largest all-round railway mounting used in the war was a St. diamond mounting, originally made for a 12-in. gun, but as this proved too violent, actually issued for service with the 24O-mm. " Colonies " coast-defence gun. The gun is 40 cals. long, with trunnions, and fires a shell of 356 lb., M.V. 2,800 f.s. The mounting consists of an upper carriage recoiling against gravity and a buffer.

FIG. 42. British 12-in. howitzer, on railway mounting.

The slide is pivoted on the main girder and traverses through a complete circle; it is extended to the rear to form a loading platform. The track requires preparation in the form of extra sleepers, to which are bolted 4 longitudinal baulks, these forming the bed to which the main girder is firmly secured. The horizontal stress due to the recoil is taken by long outriggers, 2 on each side and 2 at each end, which abut on massive shoes buried in the ground.

The British 12-in. howitzer on railway mounting is shown in fig. 42. The howitzer is 18-6 cals. long, weighs loj tons, and throws a 75O-lb. shell about 16,000 yd. The mounting is very similar to that of the 9-2-in. gun, but has a. cradle with hydro-pneumatic recoil gear. In this plate the outriggers are seen bedded in the ground.

The 274-mm. (lo-f-m.) French Gun. This gun is shown in fig. 43 on a Schneider sliding railway mounting. This is a good specimen of the French mountings designed early in the war. The French had a number of coast-defence guns with trunnions, mounted on slides, with no cradles or hydraulic buffers. It would have taken a long time to make hydro-pneumatic recoil gear for these guns, and the Schnei- der sliding mounting enabled them to be used at once. The gun fires a 5&i-lb. shell, M.V. 2,717 f.s., and ranges 29,000 yd. It is mounted on its trunnions on a girder supported at both ends by trucks. The mounting gives 40 elevation, and no traverse; the gun is layed for direction by shifting the whole mounting along a curved siding. For this purpose a winch actuating the two leading axles is fitted on the_ front truck. The gun weighs 38-4 tons, and the whole mount- ing with the gun weighs 152 tons. The curved siding is specially laid for firing. The sleepers are extra long, and are at half the usual distance apart. Four extra rails or I-shaped girders are laid. The siding is built to a radius of 100 metres; 1 if the mounting is shifted approximately too metres along the siding, this gives a change of direction of 60 degrees. Under the main girder is a set of heavy

'For heavier calibres, Schneider lays down 150 m. as the radius.

transverse baulks (the ends of which can be seen in the illustration). Before firing these are jacked down on to the rails so that the weight of the system rests on the rails and the truck-springs are eased. On firing, the whole truck mounting slides back along the rails for about 2 metres. Its motion is checked by the transverse baulks.

This type of mounting has the advantage of ease and simplicity of manufacture; it can be made in any engineering works, and there is no complicated hydro-pneumatic recoil gear, which requires special tools and experienced workmen to make. The siding is an ordinary piece of railway construction. Once it is built, no special preparation for coming into action is required, and the gun can take up its position and open fire within one hour. Tactically this mounting is inferior to one which allows firing from the open line.

FIG. 43. French 274-mm. gun, on Schneider sliding railway mounting.

The JO'5-COT. (i2-in.) French Gun on Batignolles Railway Mount- ing. -This mounting is of a type intermediate between the all round and the curved siding mounting. The gun recoils in a cradle, with hydro-pneumatic gear; the characteristic feature is that it traverses 5 each way on the mounting. A special platform is laid for it, consisting of a framework of which the transverse members (with spades on their under-sides) rest on and bite into the ballast between sleepers, and the longitudinals come under the main girders of the carriage. The mounting being run over the platform, wooden wedges are then driven between the beams and the bottom of the girders, so that the mounting is firmly supported on the platform. Recesses are formed in the lower edges of the mounting and the upper edges of the platform, to prevent the wedges from shifting. The platform provides a base nearly 10 ft. wide, this being the limiting width of the main girders of the mounting, imposed by the railway loading gauge.

The platform does not, it is stated, interfere with ordinary traffic when laid. It is therefore possible to provide several plat- forms on the open line for the same gun, provided that places can be found where the line points within 5 of the target.

Where a definite target is to be engaged, and where consequently only a small amount of traverse is required, the Batignolles mount- ing has great advantages over the type requiring a curved siding, which takes a week or more to build.

When worn, the gun is bored out to 370 mm., mounted on almost the same way as before and used as a howitzer.

FIG. 44. British 14-in. gun, on Armstrong

jnting.

The French Schneider 52O-mm. (2O\-in.) Howitzer. This fired the heaviest shell used in the war, weighing I ton 8 cwt. The muzzle velocity is only 1,640 f.s., and the range 20,000 yd. Unlike the French heavy guns, this piece was specially made as a railway gun. The mounting is of the Schneider sliding type above described, but the gun has a ring cradle and hydro-pneumatic recoil gear, for with- out this the downward blow on firing would have been too severe on the mounting and the rails. It has electric gear and the breech block is worked by a cylinder containing air which is compressed by the recoil. The' howitzer weighs 44 tons and the mounting with howitzer weighs 265 tons.

The British 14-in. Gun. This gun fires a i,4OO-lb. shell ranging 35,000 yd. Fig. 44 shows it on an Armstrong rolling mounting. The whole mounting rolls back along the rails on firing, and is hauled