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mounting forward as far as the cable extends; 500 metres of cable can be carried, though only 50 metres are normally used. The advantage of this system is that the gun-mounting is simplified and lightened by the absence of the motor, and that it is easier to find room for the gun between the sides of the mounting. The trailer carries a load of ammunition nearly equal in weight to the gun.

The most recent equipment of this type is the U.S.A. Mark IV. carriage for the 1918 pattern 9-45-in. howitzer, built to St. Chamond designs. The trailer carries a ISO-H.P. petrol engine driving a 70 K.W. 4OO-volt compound-wound dynamo, which supplies the cur- rent to 2 independent 400- volt motors, each driving one track of the gun-mount, and to similar motors on the trailer.

This howitzer is 2if cals. long and fires a356-lb. shell ranging 17,- 500 yd. ; it weighs 97 cwt. The mounting gives 60 elevation, but no traverse; this is given by traversing the whole caterpillar mounting with a small auxiliary motor. The mounting is 30 ft. long, 8 ft. 6 in. wide, and 13 ft. high, including the ammunition crane. It weighs 13 tons complete; the trailer is of the same size and weight, and carries 42 rounds of ammunition. The average speed of the com- bination is 6-5 m. an hour.

This type of power-trailer mounting has great capabilities, but has not been tried thoroughly enough to warrant its general ac- ceptance. It would appear difficult to steer across bad ground when mechanically connected; however, there is the possibility of sending the gun-mount forward across a bad place, and then halting it while the trailer follows. One advantage claimed for it is that the trailer can be used to bring up ammunition while the gun is in action.

Super-heavy Guns and Howitzers. The British regulations now apply this term to all guns heavier than the 8-in. and all howitzers heavier than the 9-2-in. Super-heavy pieces are now fired almost exclusively from railway mountings, and therefore are not trans- ported by road. The Germans in 1914 transported n-in., 12-in. and even i6J-in. howitzers by road, but the increased range of modern pieces of this calibre renders it possible to bring them up by rail to within effective distance of any target that they are likely to be required to engage. The types of super-heavy, road-travelled equipments evolved during the World War were very numerous, and only certain representative models can be described.

FIG. 37. Austrian 12-in. howitzer on its way through Belgium.

The n-in. Howitzer. The Krupp 28-cm. (n-in.) howitzer was broughtout in 1912. It was remarkable in its day as being the heaviest weapon that could be fired from its wheels without a permanent platform. This was due to the long recoil of 6 ft., and to the weight of the howitzer itself, which reduced the recoil-energy. Girdles of linked plates were fixed round the wheels to enlarge the surface bearing on the ground, and mats of sandwiched layers of wickerwork and steel plates were laid under the wheels. The howitzer fired a 750-lb. shell ranging 11,200 yd., M.V. 1,130 f.s.; it weighed6-3 tons, and the weight in action was 14-8 tons. The carriage had hydro- pneumatic constant recoil gear, and gave elevation up to 65 de- grees. This piece could be divided into loads easily transportable by road, the heaviest, 9-27 tons, being the howitzer itself on its special vehicle. It was very effective in its day, but a modern I i-in. howitzer would be expected to range at least 18,000 yd., and would probably be on a railway mounting.

The 12-in. Howitzer. A number of pieces of this calibre were used on railway mountings by the different nations. The British 12-in. ^howitzer was used both on railway and on road mobile mountings. Of those transported by road, the most notable was the Austrian 12-in. howitzer (fig. 37). Several of these pieces were bor- rowed by the Germans to assist m the sieges of Belgium and northern France, and in Sept. 1914 they travelled 150 km. from Givet to the Moselle in a day. This howitzer fired an 8s8-lb. shell, M.V. 1,100 f.s., range 10,600 yd. The_weight of the piece was only 5-9 tons, or lighter than the Krupp n -in. howitzer, which was made extra heavy to reduce the recoil. The weight in action was 21} tons. This piece could only be fired from a platform. It was easily transportable by road. In addition to the borrowed Austrian pieces, the Germans had 305-mm. mortars of their own, the first pattern dating from 1898. _ The French 37O-mm. (i4-6-in.) Howitzer. This equipment, de- signed by Colonel Filloux, was brought out during the war. It is remarkable for its extreme simplicity and the ease with which it can be manufactured.

The howitzer is 8 cals. long, with plain interrupted screw breech- mechanism ; it fires a lo-cwt. shell ranging 8,900 yd. or an 8-cwt. shell ranging 11,500 yd. It is mounted on trunnions in a small upper car- riage or saddle, which slides on guides inclined at 6 degrees. The saddle rests on spring-supported rollers, so arranged that the springs give under the downward blow of discharge, allowing the saddle to come down on the guides. In checking the recoil, the friction of the

guides is assisted by 2 plain hydraulic buffers. The lower carriage of which the slides form part is a single steel casting which traverses 12 on rollers on the platform. This is of steel, raised at the rear end, and has 4 rows of spades fixed to its lower surface ; the whole plat- form is sunk in the ground, and the spades prevent it from moving. The howitzer is loaded " down-hill " from the raised end of the plat- form, by means of a small shell-trolley which runs on rails fixed in continuation of the saddle guides.

The equipment can be transported by road, rail, or narrow-gauge railway. Whichever is used, the 3 parts of the equipment (howitzer, carriage, and platform) are each suspended from an arched girder, called a " transporter." For road transport, the ends of this rest on two 4-wheeled road trucks, one following the other, which are drawn by a tractor. For ordinary rail transport, the transporter rests upon a single 2o-ton truck, and for narrow-gauge transport the ends rest on 2 trucks.

For mounting and dismounting the howitzer the narrow-gauge railway is always used. A line is laid past the rear of the emplace- ment, parallel to the front. Two short lengths of rail are laid at right angles to the first line, connected to it by turntables. On ar- riving at these, the trucks carrying the ends of the transporter are each turned through a right angle, so that they can now move forward abreast, carrying the transporter between them. On reaching the emplacement, the platform is lowered from its transporter into the hole dug for it, and the process is repeated for the carriage and for the howitzer. The weights are : howitzer, 9-27 tons ; carriage, 9-4 tons ; platform, 9-9 tons; transporter, average, 2-5 tons. The transporter is 26 ft. long; the time required to mount the piece, not including lay- ing the lines of rail, is under 2 hours.

FIG. 38. German 3O5-mm. mortar, 1911-6.

Road-mobile Super-heavy Guns. In the World War few long guns above 8-in. calibre were provided with road-mobile mountings, and most if not all of these were old, short guns (say, 25 cals. in length) which at the present day must be regarded rather as long howitzers than as guns. Perhaps the heaviest serviceable gun on a road- mobile mounting is the Schneider 22O-mm. of 1917 above described.

The Austrian j8-cm. (i$-in.) Howitzer. This weapon was brought out in 1916, and the Austrians achieved remarkable results in trans- porting it by road. The howitzer was 17 cals. long, and weighed 20-7 tons. The breech action was the Skoda wedge. It fired a shell weighing 1,320 lb., M.V. 1,530 f.s., ranging 16,700 yd. It had a ring cradle with the usual hydro-pneumatic recoil gear. The upper carriage, which weighed 16-6 tons, was fixed to a base plate which turned 360 on a central pivot and roller ring, which formed part of the top plate of a caisson platform. This was 22 ft. long, 17 it- wide, and 4 ft. 6 in. deep, and weighed 43-4 tons empty before it was bolted together and filled with earth or concrete.

The interesting feature of this equipment was the means of trans- porting it. The howitzer was carried on a platform wagon mounted on 2 bogies of 2 axles, or 8 wheels in all. Each wheel was driven separately by an electric motor, the current being furnished by a I5O-H.P. petrol engine driving a dynamo giving 90 K.W. at 300 volts. This engine and dynamo were carried by a power vehicle weighing 9-7 tons complete, which either preceded or followed the platform wagon. The latter weighed 15 tons, or 35-7 tons with the howitzer. The equipment consisted of 5 power vehicles and 5 platform wagons, carrying respectively the howitzer, upper carriage, sections of the platform, and 16 rounds of ammunition. The average gross weight was 35 tons.

Each of these 10 vehicles was fitted for transport by rail as well as by road. The wheels were composite, consisting of an inner railway