The Birmingham age-herald., 1924-08-03


 ond, as clearly and accurately as record the progress of an incomin Its takes snapshots of high power rifle bullet at 2,700 feet a second so fast that it's victim would never hear the sound of the explosion that sent the fatal pellet on it's way to his heart.
 It records every minute step in the bursting of a soap bubble.
 The possibilities of this remarkable camera, or of others conceived on the same principle, stagger the imagina- tion of the layman. In a number of fields of everyday life the apparatus is likely to prove not only sensational, but exceedingly. useful.
 It is stated authoritatively, photo- graphs could be taken easily showing how long golf balls retain dents after lusty brassie or mashie strokes. For the ordinary player, of course, this would be no great advantage. His ball retains its dents for all time anyway. But to the expert it would make pos sible, it is likely, the fractional closer figuring on stroke, stance and dis tance which wins matches when every thing else is even.
 Is Exceedingly Intricate
 The spark camera is. of course, ex- ceedingly intricate and delicate. It has been brought to it's present efficacy by Philip P. Quayle of the Bureau of Standards, who designed and operated the apparatus.
 The principle upon which this meth cd of photography is based can be described as follows:
 A bullet is fired past a photographic plate and an intensely bright electric spark is discharged which causes the shadow to be impressed upon the sen- sitive plate. No lens nor shutter is used. The plate is placed openly in dark room after the apparatus has been adjusted, No. ray of light can reach the plate except that proceeding from the spark which is set off automa- tically when the gun is fired A potential of about 100000 volts is used taAsupply fhe sparkswhich is so potent that it will jump across a gap four or five inches wide like a minia- ture flash of lightning. The apparatus by which such potential is developed consists of static electric generator and a large battery of Leyden jars The static generator is driven by an electric motor and is equipped with safety valve whereby the current is cut off when the battery is sufficiently charged.
 The operation of the apparatus is ntierely automatic. When the opera tor IS prepared to take picture he starts the electric motor which operates the static machine. When a sufficiently high charge has been built up a lever arm,. operated on the principle of an eleetrometer, is swung around. auto atically closing switch which pre- vents an additional charge from being impressed on the battery, and a small, red electric lamp is lighted, signifying that the apparatus is all ready.
 Fired Past Plate
 The bullet is then fired past the photographic plate. As it approaches a certain point in it's trajectory, the bow wave from the nose of the projectile starts the works going by triggering Jolie interrupter, device something like q radio microphone. Within the next six thOusandth of a second, lever swings around, the spark flashes and the projectile imbeds itself in sand box behind the camera. It all goes so fast it seems like one action. From the time the projectile leaves the gun until the picture is completed is scarcely six thousandths of a second. The greatest accuracy is necessary in setting off the spark at the right time as the pulled, passes across the plate, which IS eight inches wide, in about ten thousandths of second.
 The image of the bullet is impressed upon the plate in two milliontbs of a second. So accurately can it be timed that a succession of pictures of bull lets leaving a gun have been obtained showing every stage of the firing from the moment, the first air is forced from the barrel to the time when the projectile has leaped we'll beyond reach of the gas blast Special care is taken to make the electric spark as nearly instantaneous as possible, as an ord inary electric spark, sucR as is used for automobile ignition or even a flash of lightning, is not fast enough One of the principal aims of this method of photography is to discover the behavior of bullets in flight and during impact, although it is capable of many ramifications. The War de- partment has been endeavoring for some time to ascertain the position taken by different types of bullets while in flight. The department has tried to do this by measuring the holes made in sheets of paper when the bullet passes through them, but it has been aues- tloned by scientists as to whether the paper itself does not contribute to the deflection of the bullet. In spark photog- raphy the bullet need touch nothing in its flight but the air, so this meth cd has been suggested as a possible solution of that problem. It is also pos sible to obtain clear photograph of bullet while piercing an obstacle and observe its behavior, from which yalua- ble information might be obtained for the construction of armOr piercing bull lets. This method of photography also furnishes method of measuring the speed of bullets at and above the speed of sound, at which speed some interest ing phenomena are observed which may be cleared up by spark photo- graphs.
 Present Method Employed
 The method employed at present for measuring the speed of bullets is by electrically recording the time they pass certain points along their tra ice tory. Experimentation has led to some interesting disclosures. When the speed of the bullet going faster than sound decreases to the speed of sound very cratic behavior is noticed in its flight. It seems that tremendous power is expended by the bullet in building up the bow wave. When it goes slower