The rifle grenade, which was fired by a rod fixed to the base of the grenade and running down the barrel of a rifle, being blown out by a cartridge without a bullet, was also fitted up for signalling purposes. Upon opening, a series of lights, arranged to code, were suspended from a parachute. Recognition and illuminating lights were constructed for use from aeroplanes, and were ignited by dropping through a launching tube fixed to the machine, which made contact and fired them electrically as they passed through. Landing lights and wing-tip lights, electrically ignited, were other stores used in connection with aerial warfare. Another was the incendiary bomb. Until the outbreak of war the incendiary composition for use as stars in incendiary shells was of a most primitive nature, and even during the war incendiary compositions were used which were ridiculous in comparison with those produced later. The construction also of some of the earlier efforts was quite as absurd. Projectiles were devised in a thin paper case, intended to be dropped from heights of many thousand feet, and ignite on impact, whereas the impact produced by the velocity of a projectile after such a fall was sufficient to scatter the case and its ingredients in all directions. It was the use of aluminium in pyrotechny which pointed the way to real incendiary composition, composition which exceeds the temperature of these primitive pitch and other elementary compositions by many times more than the flame of a candle exceeds the temperature of ice. Bombs containing thermit, and later on thermalloy (a composition which set hard, and did away with the necessity of a case), were terrible weapons, giving a temperature which has hardly been exceeded by other means. These compositions were almost identical with some of those containing aluminium used in pyrotechny for a considerable time before the war, but of course not for incendiary purposes. The intense heat is naturally accompanied by brilliant light, which was of great value to the pyrotechnists, the more so as aluminium compositions do not deteriorate on being kept as do those containing magnesium, and although the light is not quite so brilliant, and has less actinic value, the fact that it is considerably cheaper, combined with its keeping qualities, renders it a very satisfactory substitute for that rather expensive metal, in very many cases at least. CHAPTER XI THE CIVIL USE OF FIREWORKS The utility of fireworks and the number of purposes to which they have been applied are far greater than most people imagine, both at sea, where possibly their usefulness is most fully exploited, on land, and since the war and its consequent developments of aeronautics, in the air.