PHOTOGRAPHS OF FLYING SHOT.

Oamaru Mail, Volume XXXVIII, Issue 10580, 8 October 1910, Page 3 (Supplement)

PHOTOGRAPHS OF FLYING SHOT.

That it is possible to photograph a projectile in flight has been known since the German physicist Mach. suggested the use of the electric spark as a source, of light for the purpose —a suggestion of which Vernon Boys made practical use in 1893. Recent interesting N studies of the behavior of shot when fired from a gun, investigated photographically hi this'way; are described and illustrated in the Scientific American (New York, July 16) by its German correspondent. We learn that in Germany Albert Preuss, an' expert with the shotgun, was. tlio firsu to introduce the photography of projectiles for' the" purpose of studying" the action of shot. We read:— . . - "In tho neighborhood of 'Zorndorf, at tho-place where about 150 years ago Seidlitz's cuirassiers rested before the Preuss in 1900 ~founded a scientific instituto for the examination of arms and ammunition. Tho testingstation is named Neumannswaldc, for Trade Councillor I. Neumann, Preuss' financial backer,' is situated upon a small lake in a lonely locality, far from .habitations and railways. - ."The experiments made at Neumannswalde for photographing shot arc carried out in a dark cellar. An electriclight plant enables white or ruby lamps to be switched on in this room. At the right there is a static electric machine, in the centre two Leyden jars, and at the left a peculiar combination of gun and photographic apparatus. By turning, the crank at the right, electricity is produced, which is collected in the two Leyden jars and then passes to the photographic apparatus through the two wires connecting. The construction of thia apparatus is of the utmost simplicity-. The photographic plate is fastened upon a board -in a vertical position. There is no plate-holder and no camera, but the photographic plate is suspended openly in the dark cellar which is lighted only dimly with a photographic dark-room lamp at the time of getting the apparatus ready. Opposite the plate is located the socalled spark-gap, that is, two points between which the spark is produced, their distance being adjustable. The electricity stored in the Leyden jars will not be able to jump the spark-gap unlc&s the two vertical shect-mctal strips shown at the extreme loft touch each other.- In the normal position, the strips are separated. When, however, a shot is fired from the gun clamped opposite them, the two strips are pressed together. At this moment a vivid light flashes in the dark space between the points .of the spark-gap and produces on the plate an image of everything which at that time lies between the spark-gap and the photographic plate." y The .plates used : for the first shotphotographs, we are told, were often 28 inches long and show every individual :grain. : of shot. ~ Some grains travel in advance "of the main body and thus make the contact that takes the electric "snapshot" when the mass of shot is still itf front of the plate. It is thus possible to find out how various kinds and makes of cartridges behave as reI gards scattering. The most interesting ! phenomenon, however, is the strong air-wave in front of each grain. On account of its greater density, the air compressed in advance of the shot is pictured on the photographic plate. If several grains, are photographed close together, the plate shows how the sev"eral air-waves overlap. Behind the entire charge we see many small airwaves and eddies which break and flow into one another. To quote again: ' 'ln. tho photograph the two contact strips appear clearly at the right, also the grains of shot and the- air-waves.

At the left we see the wad, of the cartridge which follows the charge of shot at.reduced speed. The few dark spots visible in the neighborhood of the wad arc unconsumed grains. One of the shot grains has passed through the two contact strips, and has been noticeably flattened by the. impact. In the rear of this grain fly some fragments of the contact strips, and it can be observed plainly how the air spurts out of the perforation made by the shot. In front of the grain of shot we see a large circle which represents the air-wave produced by the grain. The strong light in the rear of the contact strips is caused by the spark formed when they touch each other. If desired, the effect may be screened ;by interposing a piece of cardboard between the strips and the plate. The electric machine must of course be placed in a separate room, in order that its spark may not disturb the perfect darkness of the room in which the exposure is to be made.. The "apparatus is provided with ■ a push-button for ringing" an electric bell as a signal to the assistant that ho should operate the electric machine. "Only photography can secure clear information as to the widening of the charge, the length of the space it will occupy, the scattering of the individual grains . and their deformation. Some of the grains in the photograph show plainly how far their orginally spherical form has been, altered by the pressure of the powder gases. A few of them seem to be almost cube-shaped. The bevelling off of some grains causes them to deviate considerably from the line of sight, since they are deflected in the air by surfaces inclined to the trajectory. Up to the.present it has been found impossible to photograph shot in flight at any considerable distance from the muzzle, and exposures are now. generally made at distances'of from 5 to' 17 feet from the muzzle."