INVISIBLE RAYS

Gisborne Times, Volume LXXII, Issue 11404, 3 January 1931, Page 12

INVISIBLE RAYS

AMAZING PROPERTIES

;■ Some of the amazing properties and commercial possibilities of selenium, an element which is .extremely sensitive to light, are discussed by Mr. W. . Seymour in an article entitled, Making Light Perform New Wonders,” in Pearson’s Magazine. “Positively the most uncanny thing I ever have seen is the selenium burglar alarm,” writes Mr. Seymour.

“So extremely sensitive to light is this stuff that it is affected by rays which are invisible to the human eye. The burglar alarm consists of a. special lamp on one side of the room and a selenium bridge on the other. The lamp is screened by glaks which filters out all the rays except the in-fra-red. These cannot be.seen whether the room is. lit up or in darkness, •hut so Jong as they shine upon the bridge a circuit is kept going and nothing happens. Immediately the invisible ray is interrupted—even though it be for a fraction of a second only—the circuit is broken and bells start ringing. , “From , actual experience I can say that the effect is unnerving. The experimental room was thrown into darkness, and I tried my hardest many times to cross from-one side to the other. Invariably I interrupted that ray. and set up an unearthly din. Even when I swung my walking "stick through the intangible barrier the alarm was operated. . “The applications of the idea are almost endless, and it is hardly an exaggeration to say that it will revolutionise our systems of railway working. A model railway- has been built and equipped with apparatus which makes collisions impossible. “The safety device is fitted at the foot of every signal and the lamp and bridge are placed one on either side of a single rail. Across this'rail tlm light shines on to the selenium. “Immediately the first wheel of an engine passes through that rav it breaks a circuit, and the result is that the signal above goes to 'danger.’ At the same time a. small lamp—which might he called the 'stopping lamp’—is also switched on. This shines backwards along tlio track. • “If an overtaking driver attempted to run past that signal the stopping lamp would affect a selenium bridge fitted to the front of liis engine, and' operate a circuit which would automatically apply the brakes ’and stop, tlio train.” ,■ " V ‘ ■’