them is likely to bring out a new equipment, except on a small scale, for some years to come. Experimental models, to meet the anticipated requirements of the future, are being designed. The ruling considerations are:
(a) Railway mountings for all mobile heavy guns, motor transport for all medium guns, and, in a few years' time, for field guns as well. This allows of a considerable increase of weight and power, but a field gun must still be light enough to manhandle and small enough to conceal.
(b) Heavy flat-trajectory guns will be superseded to a great extent by heavy howitzers, throwing a shell to the same distance with less effort, and consequently less wear of the bore.
(c) The range of field guns and of howitzers will be materially increased, partly by the introduction of high-angle gun-carriages (such as the split-trail carriage described below), partly by lengthen- ing the barrel, and partly by the use of streamline shell for long- range fire.
(d) All artillery will be designed principally for use from the covered position, and will have all-round panorama sights for the purpose of indirect laying.
(e) All high-velocity guns, even field guns, will use reduced charges as well as full charges, in order to avoid excessive wear of the bore. They will also use " super-charges " when extra long range is required. Practically, therefore, every gun will require three sets of sighting graduations, and three range tables, like a howitzer. This will probably imply either separate or separable ammunition. Powder must be flashless as well as smokeless.
(/) Calibres will be as few as possible, and ammunition, component parts, sights, and fittings will be standardized wherever practicable to facilitate supply.
(g) Equipments will be designed with a view to mass production under war conditions.
(h) Shrapnel shell will be used only in field guns, field howitzers, and mountain guns, on account of the difficulty of manufacturing shrapnel shell and time fuzes on a war scale. Practically all land service pieces will fire H.E. shell with percussion fuzes, and special projectiles such as gas shell (if their use is admitted), smoke shell, and incendiary shell.
All new equipments have panorama sights. In the graduation of these sights, degrees and minutes are being superseded by " mils," the mil being the angle subtended by i/iooo of the range. Since all guns will have to fire two charges, and in most cases three charges, the range-drums will require several sets of graduations, masked so that only the set in use is visible. The French have set the example of deciding that all sights in the service are to be uniform as regards the method of setting, so that a layer from a field battery will be able to lay a i4-in. gun without special instruction. This is necessary in view of the constant interchange of personnel in time of war.
Artillery Motors. Artillery of all calibres up to, and even including, 8-in. guns is now moved by road and across country by motor transport. The Austrians even moved i6-s-in. howitzers by road, as will be seen. But it is considered that in future all guns over 8 in. will be transported by rail. Although horse draught is still maintained for field artillery, at any rate in part, the post-war field guns are being designed to weigh 32 cwt. in action, which is some 10 cwt. more than was con- sidered permissible in a gun which had to be drawn across country by horses at a trot. That is to say, they are designed primarily for motor transport. Artillery motors are described here only from the technical artillery point of view.
Motor Tractors. The old-fashioned steam traction engine with its 8-ft. wheels was used at the beginning of the war for slow road draught, notably in the transport of the heavy German howitzers to Antwerp. This was practically incapable of moving anywhere off the road. A more generally useful type was the F.W.D. (four-wheel drive) petrol tractor, with each wheel separately driven. This was capable of moving over easy ground, but could not cross obstacles. This type is by no means extinct ; and a good specimen of it is the small Pavesi tractor. The Austrians used a xoo-H.P. Daimler F.W.D. tractor, and they afterwards used 8-wheeled carriers with every wheel driven by electricity generated by a I5O-H.P. petrol engine and dynamo on a separate vehicle. The French used the ordinary petrol-driven motor lorry for the rapid transport of field guns for long distances by road. In some instances the gun was car- ried on the lorry, but latterly the men and ammunition were carried on the jorry, and the gun was limbered up to it. As the gun-carriage, on ordinary artillery wheels, soon broke up when drawn at a fast pace over paved roads, they fitted special wheels with thick rubber tires. No success has yet been attained in fitting road springs to a gun-carriage, as these will not stand the strain of firing and travel- ling across country. The Russians, however, in their 1903 equip-
ment, fitted india-rubber block springs to their limbers and ammuni- tion wagons. The method of drawing guns behind motor lorries was used by the French for reinforcing troops in the fighting line, and the divisional artillery limbers and teams were used to transport the guns from the road to their positions. The principal artillery transport motor used during the war was the caterpillar tractor, with two linked steel belts called " tracks " bearing on the road instead of wheels. These were mostly of the Holt pattern. They were efficient tractors, both on the road and across country, but they were subject to the disadvantage that they cut up the road surface badly; if all artillery vehicles were of this pattern, the roads would soon be- come impassable.
The 2|-ton Holt tractor used for the American field guns during the war was 9 ft. 6 in. long and 4 ft. 10 in. wide, the extreme height being 6 feet. It was driven by an 8-cylinder motor giving 70 H.P. at 2,500 revolutions, and traversed 15 m. an hour on a good road.
In Italy, the lack of draught horses suitable for artillery has caused the authorities to take the lead in converting the field artil- lery, both of the divisions and the reserve army formations, to motor artillery. The divisional artillery is to be drawn by agricultural tractors; that at present favoured is the Pavesi tractor. This is shown in fig. 7, but the military pattern has smooth wheels with " grousers " which can be attached for cross-country work. The tractor has a 4-wheel drive, and weighs 2-35 tons only. The motor gives 25 H.P. ; the road speed is 4 m. an hour and the cross-country speed about 2 miles. This is a much less powerful machine than the American 7O-H.P. 2j-ton tractor, but it is intended to draw a gun weighing only 20 cwt. against 32 cwt. for the new American gun.
The reserve army field artillery will be drawn by fast motor lorries, and the present proposal is to carry the gun on a low travel- ling platform with road springs, rubber-tired wheels, and a spring draw-bar. This platform is to be drawn by a road lorry, which can on emergency draw two such platforms. On the battlefield the divisional artillery tractors will convey the army batteries from the road to their positions in action.
FIG. 7. Pavesi tractor.
A problem now being studied in all countries is that of producing a caterpillar tractor or carrier that shall be able to work across country and shall travel on the road without injuring the surface. The most probable solution lies in the production of smooth-faced, preferably india-rubber-faced, caterpillar tracks which shall have sufficient adhesion not to slip on wet ground. The United States is now trying smooth-centred bands made of steel scales curved so that only the centre bears upon the road. The sides of the scales are cockled or indented so as to form a gripping surface; in soft ground the centre sinks in and the sides take hold of the ground and prevent the track from slipping.
Another possible means of combining a road carriage and cross- country carriage is to fit the caterpillar with road wheels. It is possible to extend the axles of the drums which drive the caterpillar tracks, and to mount road wheels on these extensions outside the tracks. The mechanical difficulties could be overcome, but this solution is not viewed with favour by motor designers. The resulting vehicle would be cumbrous. Thus the Schneider automobile mount- ing for the 22O-mm. gun is 9 ft. wide; if fitted with road wheels the width would be n ft. 6 in., and even with the wheels removed the projection of the axletree arms would be such as to render it impossible for another vehicle to pass it on a narrow road. If the road wheels were fitted in front of the vehicle and behind it instead of outside the caterpillar tracks, they could not well be motor-driven, and the whole vehicle would have to be towed by another motor. Power-driven road wheels inside the caterpillar tracks are possible but entail considerable complication in the mechanism, and would be too close together for stability.
Some of the French caterpillar vehicles were fitted with railway wheels inside the tracks, so that they could be drawn along the rail- way to a point near their destination. This was not a satisfactory solution as the vehicles were not strong enough to be included in a train. Conversely, the 24O-mm. railway-truck mounting was fitted with lorry wheels to enable the truck to be conveyed by road. , The Austrian motor carriers for heavy guns, driven by electricity from a separate power vehicle, had railway wheels as well as road
