One of the most progressive branches of our military service is the Department of Coast Defenses, which, under the far-seeing guidance of General E. M. Weaver, holds our shores and harbors in a state of alert preparedness against foreign aggression. At Hampton Roads sits the Coast Artillery Board, composed of officers and consulting engineers to whom are referred all problems relating to coast artillery, and who have the responsibility of testing all new instruments proposed for artillery use. The purpose of this article is to describe one among several notable achievements of the Hampton Roads Coast Artillery School, this particular work having been done by Captain F. J. Behr of the Coast Artillery Corps, who, after years of effort, has recently developed a system that makes it possible to take pictures of the swiftest moving bodies, the great steel projectiles of our biggest guns--to seize them with the camera’s eye as they hurl through the air at enormous velocities or at the very moment of their emergence from the gun muzzles, and to preserve these images, never seen before, for military study and comparison. Captain Behr was ably assisted in this work by Engineer J. A. Wilson. [Illustration: THE FASTEST CAMERA IN THE WORLD The big gun, equipped with the fastest camera shutter in the world, about to be fired and the shell photographed. For years a young officer of the Coast Artillery has been trying to devise a camera so incredibly swift that it will record every stage of this lightning flight from the gun-barrel to the target. At last he has succeeded. His photographs--some of them taken one hundred thousandth of a second apart--have revealed remarkable and unsuspected facts to the military world. The story of his invention had never before been told.] Reckoning in Millionths of a Second. Some of the increments and decrements of time involved in the series of photographs herewith published (several of them for the first time) are as small as one ten-thousandth part of a second. And Captain Behr has devised a method of taking photographs of projectiles as they arrive at a steel target and penetrate the target, inch by inch, that involves increments or decrements of time as small as the one hundred-thousandth part of a second. To the uninitiated it seems incredible that such infinitesimal divisions of time can be used in practical calculations; but every trained physicist knows that in wireless work scientists of to-day speak casually of experiments that take account of _two-tenths or one-tenth of a millionth part of a second_! [Illustration: THE PROJECTILE EMERGING FROM MORTAR