THE STOP-THIEF RAY

Evening Star, Issue 20132, 23 March 1929, Page 20

THE STOP-THIEF RAY

'Hie way of the burglar is bard. The way of the cat-burglar is very bard. 'The way of the burglar who steps into the new ray will be hardest of all. It will end in’lhe arms of the policeman. The new ray is invisible. No burglar tiptoeing in the darkness toward the safe will see it. If be turns on bis own flashlight the ray will still be stealthily waiting for him, and be will not be able to avoid it. He will step across the room, but as soon as he passes across the ray that stretches like an invisible spider’s web from wall to wall—click! ping!—an.d all the burglar alarms in the room arc ringing! if by chance be searched with bis flashlight for the lamp which sends the ray ami found it be would be no better off. B be tampered with it the burglar alarms would go off as before; the lamp is so touchy that mere approach to it sets off the alarm. The secret of its behaviour is this: It sends out rays<of light which arc invisible because they are on the invisible side of the light spectrum. (Everyone has beard of these rays, some ultra-vio-let, some infra-red.) These rays fall on a screen, which is so sensitive to all kinds of light rays, visible as well as invisible, that when any solid body (a burglar's leg or arm, for example) interrupts them by crossing the patli of the rays, the sensitive screen gives who’ is equivalent to a loud cry of alarm. It cries “Stop, thief!” in light language and rings the electric alarm bell.