Lights for Blackouts
U.S. gets ready for air raids.
"Glare barrage" or invisible light
may replace blackouts
If air-raids come to America, the right kind of lighting may save us from much of the devastation that the Luftwaffe has wrought on London, or conversely, that R. A. F. is carrying to Berlin and other centers of the Reich.
Perhaps we never shall have air raids over here. We all hope not. But if planes of some enemy do reach our shores, it will then be too late to think about protection. Fortunately, we have time and we have the experience of England to guide us.
"Will we have blackouts?"
That is a question everyone wants answered. Perhaps not say the illuminating engineers. Possibly "dim-outs" or a "glare barrage" may take their place, and prove more effective.
Total blackouts, it was found in England in the early days of the war, were not an entire success. Some people, some vehicles, had to move around regardless, and the accidents resulting from the darkness were sometimes as great as the damage done by the enemy.
For many big cities, a blackout is no concealment from the air, especially if the city is on a river, which can hardly be moved. The twists of the Thames, for example, are well known. On a night when there is any moonlight at all they show up clearly from the air. Or the enemy can drop a few parachute flares to reveal them. In the same way, around New York, the Hudson River, the East River, the lower bay, and the rest of the intricate pattern of waterways that surround Manhattan would serve as a guide to a bomber pilot even if city lights were off.
Many other cities, too, have such characteristic patterns. Washington has it with the Potomac, the Anacostia River, and the Tidal Basin: Pittsburgh with the Allegheny and Monongahela Rivers joining to form the Ohio. Chicago, Philadelphia, St. Louis, San Francisco, New Orleans, all are similiarly "watermarked."
An American who was living in a Scottish city in the early days of the war tells a story of German raiders dropping bombs which set fire to the brush on a heath outside the city limits. Apparently thinking they had started a blaze among warehouses, the raiders proceeded to waste their bombs on the heath. So later, fires were set deliberately to fool the Germans by distracting marauding planes.
A similar idea is suggested by A. F. Dickerson, head of the General Electric illuminating laboratory. He proposes that the effect of glaring headlights be applied on a large scale.
To do this, numerous small, powerful searchlights would be placed on the roofs of large buildings and on top of high places, pointing upwards. Such a glare of light, he says, would tend to blind enemy flyers, prevent them from seeing through the curtain of light, and locating vulnerable targets.
This canopy of light would also silhouette bomber's for the eyes of defending fighters, flying well above the heavy attacking craft. And, as in the case of the heath fire, the lights might be placed in open fields about a city, and used to decoy the enemy flyers away.
Viewed from the air, the limits of the city might seem to he extended. Also, if the lights were set to the south of a vital area one night, to the north another, the raiders would never be sure of the location of their target.
Of course, bombers could use glare-reducing spectacles, or the windows of the planes could be made with similar materials, and then the intensity of the lights shining upwards would be greatly reduced. But the same reduction in light would reduce the visibility of other things on the ground.
In the case of automobile headlights, the use of Polaroid film, which "polarizes" light, making it vibrate in a single instead of many planes, has been suggested to reduce glare. There would be placed over a headlight such a film. A similar film would be contained in the windshield of an approaching car, except that the angle of its polarizing plane would be at 90 degrees to that of the headlight. Thus, the direct light from the headlight would be practically eliminated, but the driver could see the road plainly.
This system would not help the raider, however. While he might use polarizing spectacles, the ground defenders would hardly be obliging enough to put the proper screens on their searchlights. Probably the chief objection to the scheme would be the need for so many lighting units and perhaps portable power plants.
The first demonstration of blackout lighting in the United States was made recently at Lynn, Mass., when General Electric engineers showed 12 specially designed illuminating units spaced 100 feet apart along Parkland Avenue.
These lights, of about one candle-power each, replaced the usual 4000-candlepower street lights, but still it was possible to see persons or objects at distances of 25 feet.
The units are shaped like an admiral's hat, and use a 2.5 watt argon (gas-filled) lamp. The light they give off cannot be seen more than a few hundred feet above ground. A whole city so lighted would be invisible to bombers, which have to operate at a minimum of 20,000 foot to escape antiaircraft fire.
Another advantage is that these argon lamps give off invisible ultraviolet light. When these rays fall on certain materials, called phosphors, they cause them to glow with "fluorescent" light. Fence posts could be covered with such paints. Signs, curbs, and even vehicles might he treated the same way. Their ghostly glow would warn of their coming, yet they would not show very far away.
The use of these gas lamps, of low power, differs some from the British practice. There, lighting units employ incandescent lamps, perhaps of 15 watts, and screen them so that only a small part of the total light is used, and that is directed the proper way. The main thing is not to let the light shine upwards. A light of half a candlepower can be seen easily a mile away. The observers in planes on night raids, selected for their ability to see in the dark, have been in darkness for many hours. Their eyes are adapted to the dark. They could see a half-candlepower lamp many miles away.
Another method of lowering the intensity of street lights has been suggested by Samuel G. Hibben, Director of Applied Lighting for the Westinghouse Company, and a member of the British Illuminating Engineers Society.
This is the "dim-out" which would reduce the normal lighting to the low level of moonlight. Immediately after the raid, normal lighting could be resumed. This would he done, suggests Hibben, by the use of voltage-regulating devices in the power stations, where all the lights over a given area could be reduced at once.
"The main objective of a 'dim-out,' " says Hibben, "is to remove definite map patterns. For this reason, the primary street lights would be extinguished on main boulevards, long avenues, and on peculiar winding roadways rather than the blackout of business or residential areas. There is the possibility of applying temporary shields to dim street and automobile lights to take care of emergencies with much less risk than would result from radical reduction of lighting."
