INCENDIARY SHELL Incendiary shell have been successfully used against aircraft and to some extent in bombardments of inflammable ground targets. Anti-aircraft shell are of small caliber and are usually tracer-incendiary. Such shell are filled with pyrotechnic mixtures which ignite at the moment of firing, or by time fuse, and are effective against highly inflammable material. Shell filled with thermit which explode and scatter the molten iron have been used against aircraft and ground targets, but with rather poor results. Large shell, which burst upon impact and scatter units of burning materials, have been used with some success against ground targets. Tracer shell contain such mixtures as barium nitrate, magnesium and shellac, or red lead and magnesium. INCENDIARY BULLETS Incendiary bullets are only effective against highly inflammable material, and are therefore used principally in aerial warfare against aircraft, either for the purpose of igniting the hydrogen of the gas bag, or the gasoline. The present tendency is towards the use of the large size (11 mm.) bullet, because of its greater incendiary action. The incendiary material is either white phosphorus or a special incendiary mixture consisting of an oxidizing agent and some combustible or mixture of combustibles. The white tracer bullet contains a mixture of barium peroxide and magnesium. A red bullet contained in addition, strontium nitrate and chloride, or peroxide. INCENDIARY HAND GRENADE While the use of incendiary grenades and other small incendiary devices is limited, such armament is considered very valuable in trench warfare. They can be used to set fire to inflammable material, either in offensive or defensive operations. Phosphorus grenades, while used principally for producing smoke (see page 302), have considerable value as an incendiary weapon. Thermit grenades are very useful in rendering unserviceable guns and other metallic equipment which must be abandoned. They permit aviators to destroy planes which motor troubles oblige to land in enemy territory. They are also used to ignite inflammable liquids, thrown into a dugout, or sprayed over an objective by a flame projector. The Mark I hand grenade was developed for burning enemy ammunition dumps, for clearing away brush or other material in front of trenches and for use in dugouts. The standard H.E. grenade body was half-filled with thermit and half with a celluloid container filled with a solidified fuel oil. The grenade is fired by the spit of the fuse of the bouchon firing mechanism. This, through the booster, lights the thermit igniter, which in turn fires the main charge of thermit. The resulting molten iron readily penetrates the grenade case, at the same time igniting the celluloid case and its contents. The oil burns for about 3.5 minutes. This grenade was never used since it was considered that an all thermit grenade would be of more value. TRENCH MORTAR EQUIPMENT