so expose himself to the effect of green-cross. The blue-cross irritant acted as a fine cloud, with which it was very difficult for the filter of the gas-mask to deal. Blue-cross also combined gas and H.E. effect, and the beginning of the gas attack was covered by the use of a diaphragm, as in the yellow-cross H.E. shells.
The German experience with gas-ammunition was excellent. On their side no instance is known of the enemy being able to advance over ground infected with yellow-cross. No attack ever made with " parti-coloured-cross " (blue- and green-cross) in a favourable wind failed to paralyse the enemy artillery either entirely or in great part, even when they were under cover, during the critical hours.
Special Ammunition. At first the gas shells were also reckoned as "special" ammunition. Later on, however, they came to be con- sidered as part of the ordinary artillery ammunition. The extent of their employment, at all events, in the case of the Germans, often equalled or even exceeded that of the ordinary explosive ammunition. The ricochet shells were used to obtain a specially retarded action.
Against tanks the German artillery used a shell with an armour- piercing head, rather more effective than the ordinary nose-fuzed shell. The projectile had a massive armoured-steel head which was fitted with the steel shell body, and was set in motion by a fuze placed beneath this-^i.e. a central fuze.
For anti-aircraft purposes projectiles with tracers were used ; experiments with these had been made in peace-time. Krupp pro- duced a model which proved very satisfactory, especially in certain small anti-aircraft guns. The path of a 2-cm. shell was clearly vis- ible from the gun muzzle, that of a 3'7-cm. to 1,500 metres. Tracers were not, however, much used with field guns and large calibres, and were not greatly liked by the anti-aircraft batteries.
Against airships and balloons inflated with gas, a balloon incen- diary shell, also of Krupp manufacture, was employed. The pro- jectile which acted like shrapnel and was provided with a time-fuze, shot lumps of incendiary composition out of the shell-case. The old incendiary shrapnel was little used. For signal purposes e.g. to demand the opening of fire on particular points shrapnel with various-coloured-smoke producers were used.
In accordance with the demand of the troops message-carrying shells were made. These shells contained written communications, and, on exploding, gave off conspicuous smoke and flame ; the mes- sage came to ground either by means of a parachute or in a recep- tacle which broke as it fell. They served to connect points cut off from one another by enemy fire or otherwise.
Minenwerfer Munitions. The Wurf mine (thrown mine), i.e. the trench-mortar shell which was already included in Germany's equipment at the beginning of the war, differed from the artil- lery-shell principally in its considerably increased explosive charge. The " efficiency " rose from 30 to 40% of its total weight. Con- sequently the wall of the shell was thinner as the small propel- lant charge made less demands on its strength. The shape of the projectile was similar to that of the artillery-shell, except that the shape of the head was not of great importance. The shell material was, generally speaking, similar to that of artillery munitions, but economy was more in evidence here. Thus constant use was made of cast-iron in certain types of shells to the detriment of the essential feature, viz. the increased proportion of explosive. In order to econ- omize the most valuable explosives for the artillery-shells, use was soon made of ammonium-nitrate explosive, "safety" explosives, and such like. In Austria-Hungary, for instance, hardly anything but dynamon was used. In Germany perdit for heavy bombs and perchforate for light was resorted to. Such explosives answered very well for these projectiles. Unlike the artillery-shell, owing to then- less accurate flight, they required a fuze which would be effective in every position of fall. This was a very difficult problem to solve, but eventually the Papenberg fuze used in both countries and the Skoda fuze in Austro-Hungary were evolved. In the first and simpler types of mortar a cord friction-lighter was used as time-fuze. The German standard pre-war minenwerfer had percussion fuzes.
The explosive charge was started in much the same way as in artillery-shell with picric-acid filling. Later on, to economize steel, the gaine was made of cardboard cases of several thicknesses. As the minen were not air-tight, the great hygroscopicity of the ammo- nium-nitrate explosive caused a dampness after a time, which affected the cardboard casing and caused a mixing of the two explosives, with the consequent danger of spontaneous explosion.
According to the type of mining weapon pneumatic, smooth- bore, rifled muzzle-loader or rifled breech-loader as the case might be the method of obtaining rotation was similar to that in the artil- lery-gun, or to old types of " stud " rotation, or were simply gas checks which had only to seal. Some types of muzzle-loader bombs had concertina-like compressible plates of thin iron which were forced or discharged through the grooves. Some few projectiles obtained stability in the flight by means of vanes. In the end it was the rifled mortar and, 'for the heaviest calibres, the rifled muzzle-loader which held the field. But a substitute material was always used for the driving-bands of minen mortar bombs for a short time zinc-aluminium, and then only soft iron, less injurious to the bore.
For the propellant charge smokeless cube and flake powders were used, and in some types for a short time black powder. The charges were comparatively small. To meet the demand of the troops a
propellant charge of compressed air was used in some types up to 20- cm. calibre. By this means all smoke flash was avoided and the re- port considerably lessened. Results, however, with regard to rapidity of fire and the weight of the bombs were not satisfactory, and the supply of compressed air was also very tiresome. In 1917 pneumatic mortars were therefore abandoned. Towards the end of the war an attempt was made to get full value out of the gas pressure by using a stepped chamber and stepped shell body.
While Germany even before the war had included both light and heavy minenwerfer in her equipment, it was some considerable time before Austria-Hungary adopted them as a normal weapon. The bombs were at first intended for the destruction of barbed- wire entanglements, but in the course of the campaign their true function came to be that of meeting the demand for additional artillery effect and for great mine effect at short distances. In the first instance various improvised models were made in the Pioneer Parks to meet these needs, particularly in Austria-Hungary at the beginning of the Italian campaigns. Improvised types were also used in Germany at the beginning to supplement the insufficient supply of standard trench-mortars. These types all disappeared when the regular types began to be produced in sufficient numbers. Nevertheless, the experience was a guide to future development.
Later on, trench-mortar bombs were charged with gas. In view of the small results gained by this form of gassing it was abandoned in 1917 in favour of gas " projectors." In the case of some special projectiles e.g. illuminant and message-carrying trench-mortar types proved more suitable than gun types.
The diminished strain on the body, smaller impact energy and comparatively large space available in the shell facilitated the fitting- in of the necessary components for these purposes. Another special bomb was the strongly built armour-piercing bomb which was effec- tive against a 2o-cm. armour plate. The difficulties experienced in the production of artillery-shell due to lack of raw materials were in- tensified in the case of the trench-mortar bomb, which in the table of priority for assignment of material was considerably behind the artillery munitions. And yet, although the conditions were com- paratively less exacting as regards quality of material, flight condi- tions, precision of shooting and effect, their design involved com- prehensive work in order to meet the very varied requirements with the simplest ballistic means, manufactured with the simplest tools. The employment of substitutes aggravated the difficulty. For this reason the help of private inventors, which had not answered in the case of artillery munition, here had most successful results.
Hand Grenades were practically unknown during the first months of the war; with the institution of trench warfare the need of a simple high-angle projectile was immediately recognized. Both in Germany and in Austria-Hungary the troops improvised hand bombs of a very varied character in the Pioneer Parks. All were time grenades.
Early in the autumn of 1914 the German Army Administration turned out a simple' cast-iron ball grenade, which could be produced in any foundry. Later on, to secure improved range, a change was made to the " egg " hand grenade of similar construction. The lat- ter, together with some other types, were in use until the end of the war. At the same time Austria-Hungary produced the " universal " hand grenade, which as early as October 1914 was used by the troops in trench warfare in Serbia. It consisted of a cast-iron body, serrated for fragmentation, and filled with ekrasit. Ignition was by means of a friction lighter and fuze length and detonation. This hand grenade could be conveniently thrown to a good distance by means of a stirrup-shaped wire " thrower," which could be attached to the waist belt. Later on the hand grenade was the chief weapon of the infantry " assault troops," and to a large extent deposed the rifle from its supremacy. The demand therefore was enormous and production had to meet it. In view of the great burden already placed upon the whole armament industry their design had to be of the sim- plest so as to bring fresh factories into the effort of production. The classes of explosive employed were the same as those of trench- mortar bombs. In addition to the ever-increasing numbers of " egg " hand grenades Germany also supplied her troops with the " Stiel " (handled) grenades. These stood the test right to the end. Austria- Hungary too proceeded to improve her " universal " hand grenade, and produced from 1915-7 two types of tubular hand grenade. A cardboard tube which served at the same time as a handle carried the friction-lighter, time-fuze length, detonator and burster cartridge. The top was surrounded by a heavy ring of cast-iron for fragmenta- tion. These grenades were all timed for 7-8 seconds.
In March 1917 Austria-Hungary began to use the handled grenade, which formed part of her equipment until the end of the war. It was similar in principle to the German (separate transport of the detonator was, however, not considered necessary). The endeavour to absolutely safeguard the bomber from the effects of a premature explosion of the grenade led in Germany, for instance, to various methods of igniting the fuze length, including designs in which ignition took place after leaving the hand. On the other hand it was desirable to relieve the operator from the disturbing sensation of the burning grenade in his hand. The time-fuze hand grenade, moreover, on account of its slow combustion, allowed of a return throw by a specially adroit adversary. Both countries, accordingly, experimented with a succession of percussion grenades. The diffi- culty lay in stabilizing the flight to guarantee the right impact and
