An entirely different principle was used in the construction of the incendiary bullet. This bullet was also incased in cupronickel; but the incendiary chemical, which was phosphorus, was contained in a chamber in the nose of the bullet. A serrated plug held the phosphorus in its chamber, and behind this plug was a solid plug of lead coming flush with the base of the bullet and soldered thereto. On one side of the missile was a hole drilled through the cupronickel into one of the grooves of the serrated plug. This hole was stopped by a special kind of solder. The heat of friction developed in the infinitesimal space of time while the projectile was passing through the gun barrel served the double purpose of melting out the solder from the hole and igniting the phosphorus within the chamber. Thereafter the centrifugal force of the revolving bullet whirled the burning phosphorus out through the unplugged hole. Seen in the air the fire of the phosphorus could not be discerned, but the burning chemical threw off considerable smoke, so that the eye of the gunner could follow the blue spiral to its mark. Our incendiary bullet had an effective range of 350 yards, after which distance the phosphorus was burned out. [Illustration: 8-MILLIMETER FRENCH CARTRIDGE, .303 BRITISH CARTRIDGE--(MACHINE GUN), 11-MILLIMETER FRENCH INCENDIARY BULLET, AND A SHOTGUN SHELL.] [Illustration: LEFT TO RIGHT--ARMOR PIERCING, TRACER, INCENDIARY, ORDINARY.] [Illustration: UPPER ROW--.30 CALIBER RIFLE CARTRIDGES WITH BULLETS FROM LEFT TO RIGHT, AS FOLLOWS: ARMOR PIERCING, TRACER, INCENDIARY, ORDINARY. LOWER ROW--.45 CALIBER AMMUNITION IN CLIP FOR REVOLVER--.45 CALIBER AMMUNITION FOR PISTOL.] Equally interesting was the construction of the armor-piercing bullet. Heavy and solid as the jacketed lead bullet used in our service guns seems to be, when fired against even light armor plate it leaves only a small mark upon its objective. As soon as the cupronickel jacket strikes the armor plate it splits and the lead core flattens out and flies into fragments. The armor plate may not even be dented by this impact. Yet change the core of this missile from lead to hardened steel and an entirely different result is produced. Our armor-piercing bullet was made with a cupronickel jacket for the sake of the gun barrel. The inner side of this jacket was lined with a thin coat of lead which was made thicker in the nose of the bullet. Finally a core of specially heat-treated steel completed the construction of the projectile. When this missile is fired against armor plate the jacket splits and the lead lining virtually disappears from the impact, but the pointed steel core keeps on and bores a hole through the plate as it might through soft wood.