Comparatively few persons realize, I suppose, that fireworks almost identical with those we used to set off on the Fourth of July in the good old days before the safe-and-sane laws went into effect are utilized in aerial warfare and form a valuable and often vital asset for the aviator. Most of these aerial pyrotechnics resemble in their effects the colored lights and the Roman candles of our childhood and are used for signalling from the airplane to the ground and vice versa, or from one plane to others in the air at the same time. For this purpose every active service airplane carries one or more signalling pistols, depending upon the number of the crew. These rather formidable-appearing weapons, which look not unlike the big-barrelled affairs the pirates were wont to carry in their scarlet sashes, are similar to the Very pistols used in the trenches; their ammunition consists of cartridges very similar to shotgun shells, but larger, containing stars of various colors, like those in Roman candles, and the necessary powder charge to eject the stars. Three colors, red, green, and white, are furnished, the color of the star being indicated on the base of the cartridge, which is also serrated in such a manner that the aviator can tell the color by touch when flying at night. By different combinations of these colors an almost endless variety of signals can be conveyed. One of the strangest and most fascinating night sights on the Western Front was to see these countless stars, scarlet, yellow, emerald, shot from invisible airplanes, drifting across the purple velvet of the sky. The stars are clearly visible in the daytime and were used for many purposes, such as indicating the position of enemy troops, the presence of hostile aircraft, requests for assistance from other planes, and as a means of transmitting orders from the leader of a squadron to other machines in formation. At night the signalling pistol is of exceptional value in aiding the aviator to effect a safe landing. When approaching his home-field the pilot fires a light of a prearranged color, and if answered by a light of a proper color from the ground, he knows that the field is clear of obstructions and other machines and safe to land on. Pilots have also used their signalling pistols for firing into their gasoline-tanks and thus setting fire to their machines when forced to land in enemy territory. There are also a few cases on record of the pilot being able to hold enemy soldiers at bay with his signalling pistol long enough to prevent them from extinguishing the fire.