Fire!

Most automatic fire alarms are set off by a fire's heat ; by then the fire is usually blazing merrily. A Socony-Vacuum physicist named Paul B. Weisz thought he could do better. Last week, in Electronics magazine, he announced an ingenious ray-catching tube so sensitive that it can detect a match flame at 60 feet in broad daylight. The basic idea of Weisz's gadget is the detection of minute quantities of ultra violet radiation. In the earth's absorbent atmosphere most natural and electric light rays, except clear sunlight, contain almost no radiation in the far ultraviolet (below 3,000 angstroms*); but an open flame or spark radiates appreciable amounts in that range. Weisz developed a photoelectric adaptation of the Geiger-Miiller counter (usually used for detecting radio activity), which responds to a flame or spark but not to ordinary light. Its likely first use: in airplanes -- to give warning of flaming motors.

*A minute unit of length, named for Swedish Physicist A. J. Angstrom. One angstrom is one hundred millionth of a centimeter.

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