SCIENCE NOTES.

New Zealand Herald, Volume LXIII, Issue 19382, 17 July 1926, Page 4 (Supplement)

SCIENCE NOTES.

OLD AND NEW DYES. RELICS IN POMPEII RUINS. SUPREMACY OP GERMANY. Among the ruins of Pompeii one may see the remains of a workshop, .with l vats, utensils, and ovens. It was a Roman dyer's .shop, for from the earliest period of history men have loved to stain their farments and the fabrics that made their omes beautiful with red, blue,, purple, and yellow dyes. Bat until 1856, when Perkin discovered how to procure beautiful, Jast dyes from coal-tar products, all dyes'came from vegetable substances. All modern dyes are derived from coal-tar products, and give the minutest shades of every colour of the spectrum. Once all dyeing was done at home, and even to-day, in the Highlands of Scotland, there are old wives who still possess the secret of it. • But the epochmaking discovery of coal-tar dyes started a vast industry. The raw material is subjected to many delicate tests by the chemist in search of a new tint. He tries, patiently, day after day, the reactions of the black odoriferous substance to alkalis and acids; he washes it with ether, cleans it with benzine, cooks it, Stools it, and so on, until at length be sees appearing a new and beautiful tint—a new dye. It was in England that coal-tar or, as they are now called, aniline dyes, were first discovered. France grasped tbe idea and started large dyeworks. But, both England and France, were outstripped when German scientists, working from the groundwork of the English chemist, Perkin, entered the field and made German dyes world-famous. During the war an attempt was made to wrest from Germany the supremacy she had. won in the dye industry. But the clever, hard-working, if not original, chemists of Germany still lead the world in the line they have made their own. MAN'S WEAKEST SENSE. Of the five senses possessed by man, that of smell is the least developed. Many objects give ont odours that can be detected by animals and insects, but which cannot be smelt by human beings.

WARMTH BY WIRELESS. That it is no more improbable to broad- , cast heat waves than, it is to broadcast sound waves is the view of Professor S. E.' Dibble, of the Carnegie Institute of Technology. But, he states, much research work must be done to discover instruments capable of controlling heat waves, and a detector that will anticipate the waves, hold them, and amplify'them. It is known that heat travels through space and through • solids, says Professor Dibble, and when once we learn how to pick up these waves and control them, heating throughout the world will be revolutionised. Heat broadcasting will mean better health to the public,- because it may remove from the air the impurities of modern heat-making systems. A SILENT AIRSCREW. i Tests have just been completed in England of a new metal airscrew which is claime to be silent. This is the latest type of Fairey-Reed airscrew, and the design and methods of construction are entirely novel. It is a solid forging in light alloy and is said to represent a constructional advance on other types. But the most important feature of the new airscrew is its silence. This makes possible the construction of bombing aircraft immeasurably more deadly than any that have been produced hitherto and on long-distance commercial air expresses, giving -the passengers a much higher degree of comfort. The exhaust noises in aero-engines are not difficult to silence, but so far the airscrew noises have been predominant and have baffled all efforts at silencing.