International projectionist (Oct 1931-Sept 1933)

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February 1933 INTERNATIONAL PROJECTIONIST 23 at a rate that the eye and mind can f(jllow. Consider, however, an indefatigable tennis player who repeats his stroke, identically, one thousand times a minute in a darkened room. If the light be flashed on him at a constant rate, exactly equal to his stroking rate, he will appear as though motionless under continuous illumination. If the flash speed be slightly slower than his stroking rate, his arm will be illuminated a little farther along in the stroke each time the light flashes and. as the eye retains the image between flashes, the madly stroking player will seem leisurely, and a single stroke can be spread over a minute if desired. Humans, tennis playing or otherwise, cannot repeat uniform cycles at any such speed. Machines can, and wherever complicated machines are designed, built, or used, the ability to watch their operation in slow motion without photography is a boom. Varied Applications The stroboscope permits stopping the motion of the ma<;hine (visually), for examination of machine or product at any part of its operating cycle while the grommets flow into the hoppers at undiminished speed. Or, perhaps, a squeaking clutch, a vibrating shaft, or a chattering valve spring stands between a new model and a waiting public — which will not wait long. A slow-motion study will show the trouble, or the primary motion may be stopped and the vibrating member made as conspicuous as a mosquito-brushing hand at formal guard mount. Sometimes the transient movement or ■vibration takes place at too high a speed for the eye even with the primary motion stopped. Here photography is restored to for a second slowing down of the transient. Operating Requisites A little consideration of what is being done by the stroboscope is sufficient to set up the requirements of a satisfactory one. An accurate means of timing the flash and a prompt and accurate response to the flash control are essential, otherwise the object will be viewed at irregular intervals, and vibrations not present in the object viewed will be introduced. The flash must be of extremely short duration. Otherwise appreciable motion will take place during illumination, and blurring of detail will result. The light must be brilliant. Otherwise the room must be made entirely dark, and details will not be seen clearly. ARTIFICIAL LIGHTING HELD BETTER FOR SEEING ARTIFICIAL lighting is actually better than daylight on the basis of good seeing conditions, according to Westinghouse engineers. In factories and offices particularly, the advantages of artificial light come to the fore. During the day, sunlight changes in color, direction, and intensity, resulting in conditions that produce a strain on worker's eyes. Under similar applications, artificial light remains constant. Because of this difference, lighting engineers have been advocating artificial in preference to natural lighting for a number of years. Already a factory has been constructed without windows, and several offices built after the design. It is common knowledge that direct sunlight is too intense for comfortable reading. The same is true in painting, hence the reason artists and photographers prefer "north light," the reflection from the north sky. It is indirect and diffused. It is possible with modern lighting equipment to control artificial light so that it simulates "north" light. The reflection breaks up the particles of light and makes soft illumination, protecting eyesight. NEUTRONS AS ELEMENTARY UNITS OF MATTER NEUTRONS are elementary particles of matter and not combinations of electrons and protons as has been hitherto thought, experiments conducted at Yale University indicate, Dr. Franz N. D. Kurie, Sterling Research Fellow, announced recently. The neutron, whose presence was suspected by physicists for many years, was not discovered until a year ago by Dr. James Chadwick, working in the Cavendish Laboratory at Cambridge, England. The difficulty lay in the fact that the neutron does not carry an electrical charge; hence it can pass through various materials without affecting its particles and without leaving a trail, as do electrons or protons when they are shot through a medium. This led to the assumption that the neutron must be a combination of an electron and a proton bound together, the electrical charge thus being neutralized. Two Views of Neutron Two views of the neutron are held: That it is either like a dumbbell, with a positive charge and a negative charge, separated by a small distance so that their effects are neutralized, or it is like an onion, with a small sphere of one kind of electricity surrounded by a layer of the other kind, so that again the charge is neutralized. Dr. Kurie's experiments with neutrons do not conform either of these theories. He concludes that the neutron is not built according to either of the accepted models. His experiments indicate that the neutron is an elementary particle of matter on a par with the electron and proton, possessing its own individuality. THE SUBTLE BACILLUS 'From Whom Did He Get It? To Whom Did He Give It?" A. J. Schaeffer Published as a gesture of thanks on the part of projectionists everywhere to the National Tuberculosis Association in recognition of the latter's Early Diagnosis Campaign which opens on April 1 NOT so many years ago smallpox marks were so common that the person who did not have them was almost a curiosity, diphtheria and typhoid snatched hundreds from the bosoms of of their families, and cholera and the bubonic plague were a recurring feature of community life. Deadly as these scourges were, they had one thing in common — the symptoms of each were recognizable very shortly after the onset of the disease and the victory or defeat of the ever-threatening Reaper was decided in a few days. Today medical science knows not only how to battle such enemies successfully but has even developed means to prevent most of them from ever beginning. The fantastic realm of microbes has other methods of striking at mankind, however. Among its most subtle weapons is the disease, tuberculosis. Tuberculosis, like all affections, has its own peculiar symptons, but unlike those of other ailments they are not usually recognizable until the disease has made considerable headway. Nor is its course determined in a week. It frequently demands years of treatment during which the patient must remain in bed. So subtly do tubercle bacilli work that a whole family can become infected from a single member before he shows even the first symptom of illness. Obviously the only sensible step to take when a case of tuberculosis is discovered is to have every member of the family examined to make sure no one else has it. It is especially important that children be examined, and for this purpose a good doctor will use the tuberculin test and, if necessary, the X-ray. A Family Problem Why should all members of a family be examined when a case of tuberculosis is discovered? The reason lies in the fact that tuberculosis is not an overnight disease. Modern knowledge tells us that practically every person has the germs of tuberculosis — tubercle bacilli — in his body, and that these bacilli were acquired in small doses usually during early childhood. If the youthful body is strong enough to withstand these small doses of infection the bacilli remain quietly in the body like a sleeping dog. waiting for an opportunity to crash through the delicate defenses. That opportunity usually comes during the teen age, when the body is run down. iContiued on page 26)