SEEING THROUGH METALS.

Manawatu Herald, Volume XLVIII, Issue 3554, 26 October 1926, Page 4

SEEING THROUGH METALS.

STRANGE USES OF INVISIBLE LIGHT.

Can anyone tell whether the heart of an apple is good or bad without cutting the rind? Most people would say no. Yet it is done every, day in South Africa, where fruit from the large farms is passed through an X-ray instrument. Looking through a small eye-piece, the operator sees the shadows of the bad parts on a screen as if they were projected by a magic lantern.

Some time ago a valuable picture attributed to a famous artist was put up for auction, but a discriminating buyer suspected that it was a fake, so he had the alleged old master subjected to X-rays. A third eye Suddenly appeared between "the two eyes of the painting, showing that the present picture was painted over another. Leather is like glass to those wonderful rays, and many of the largest boot shops in London use an instrument by which buyers can actually see their toes lying in a new pair of boots. This is particularly valuable in the ease of small children, upon whose description of shoe comfort little reliance can be placed. Working off the ordinary mains, the electric pressurq in the instrument is increased to about 90,000 volts. The machine costs about £IOO. PREVENTING ACCIDENTS. Seeing through steel by X-rays is usually possible only to a depth of three inches, but up to twelve inches of aluminium are quite transparent, and by the use of X-rays flaws or blow-holes in metal castings are distinctly visible. 1 A serious accident took place at •Shanghai recently owing to the explosion of a turbine disc. Some deaths were caused, and the roof of the building was knocked out. It is very necessary that these turbine discs, that revolve at very high speed, should be flawless, and Xrays are applied to their testing; but the used is very elaborate, costs about £1,500, and works at a voltage

Whether he has screwed his screws in straight is a vitally important matter to an aeroplane woodworker. By X-raying the parts the screws can be seen through the wood, anl often it is foum( that the wood has been split internally without any outward sign. Weakness that might cause terrible accidents is thus detected.

The welding of metals, that is so important in engineering work, is tested in a similar manner, and the long lenghts of fibre from which cotton is made are also scrutinised in this mysterious light. Any small particles of metal are shown up clearly as shadows on the screen, and the same process is now applied to their products by some manufacturers of tobacco to detect metallic dust.

Whether a pearl is a real one or a lake can be found out in the same way. The genuine article has a kernel in the middle, round which the oyster makes the pearl, and the X-ray camera reveals a clear o\ffline with nothing in the middle in the case of the manufactured pearl. X-RAYS IN INDUSTRY.

Even thermometers are X-rayed nowadays to make sure they arc made of the correct kind of glass. Lead glass shows up differently on the screen to soda glass, and if any vapour is given off by the glass of a clinical thermometer the resulting loss of accuracy might'lead to fatal results.

The most curious application of X-rays to industry is their use in connection with large consignments of Havanna cigars shipped to Great Britain. Tiny microbes make their home in the heart of the cigars, and get hungry on their journey across the ocean, and eat the centre of the cigars.

Thousands of expensive cigars were formerly ruined in this way, but it has recently been discovered that if cigars are subjected to powerful X-rays prior to despatch all these little pests are destroyed.