In this photograph--the first of a remarkable series showing five stages of a moving projectile--the half-ton projectile seems to be standing still, but really it is traveling at the rate of 900 miles an hour. The gunners here work in concrete pits 34 feet high. Underneath the mounts are the powder magazines. Each pit has four mortars usually served by an entire Coast Artillery Company. The projectiles are the same as those used in the twelve-inch guns, but less powder is required because mortar projectiles are hurled high in the air, not straight at a vessel, and deliver their destructive blows downward from a great height.] [Illustration: THE SMOKE RINGS WHICH APPEAR This second photograph shows the projectile almost entirely out of the mortar. Its sharp nose may be seen above the “gas-ring” forming at its upper end. These “gas-rings,” or “smoke-rings,” come without warning, and only occasionally, perhaps once in eight or ten shots. They rise swiftly to the height of fifty or a hundred feet, growing larger and larger, and giving forth a weird, shrieking sound like a second projectile. Some insist that these “smoke-rings” are as hard as steel, owing to the enormous compression of their composing gases, and the story is told of a bird caught in the path of one of them and torn to pieces.] What happened to the projectile after it leaves the gun, or after the discharge of the gun, and before the projectile has had time to issue from the gun-barrel? What is the action at the muzzle of gases generated? What shape do these gases assume as they leave the gun? What causes the much-discussed “gas-rings” that sometimes form when a mortar is fired, and oftener do not form? What phenomena attend the arrival of the projectile at a solid steel target? Is the steel actually fused by the heat of impact? Is it vaporized? Or what? These are some of the questions that Captain Behr set himself to solve, or to help in solving, as he worked out his methods of rapid photography. His aims were strictly military, but his results make fascinating appeal to the general imagination. Fancy doing anything in the one hundred-thousandth part of a second! [Illustration: THE PROJECTILE HIDDEN BY THE SMOKE CONE In the third photograph the smoke-cone is almost perfect and gives the famous “powder-puff” effect. It still hides the projectile, although the latter is traveling at a velocity that would take it from New York to Chicago in one hour. At night the “gas-rings” present a startling and fascinating appearance, burning with a reddish orange glow, and whirling with a complicated double motion, strange opalescent balls, like rings of Saturn. A study of these photographs--the first record ever made of the “gas-rings”--has led some experts to the conclusion that the cause of the rings is defective ramming of the projectile.] [Illustration: THE PROJECTILE EMERGING FROM SMOKE CONE