Science and Invention.

Alexandra Herald and Central Otago Gazette, Issue 440, 1 September 1904, Page 3

Science and Invention.

—«•— COMPRESSED AIR AS A CLEARER. THE efficiency of compressed air as a cleaner of electrical machinery, particularly machinery in motion, is not sufficiently appreciated. By no other means is it possible to remove oil-soaked copper or carbon dust without wiping or scraping the coated part. Great care must, of course, be taken to prevent grit or dust being drawn through the pump, as this would work havoc with the surface against which the blast is directed. As this is so easily prevented, it cannot be urged as a practical objection to the use of compressed air for cleaning purposes. OXIDISING METALS. Many ingenious processes have been developed for intensifying the oxidising action of air on metals by submitting the latter to reaction in the form of a finely-divided spray. The latest proposal, that of M. Harmet, has for its object, the treatment of cast iron, producing a refined iron or steel. Molten ore is caused to flow through a fine" channel surrounded by an annular air-blast which thus forms a tuyere, driving the metal forward in a fine spray. The spray is collected and allowed to flow together again in a receiving chamber, from which the molten steel can be tapped. WIRELESS AUTOMATIC SIGNALS.

In the new fire-alarm system of Emile Guarini of Brussels, automatic signals are given by wireless telegraphy. The rise of the mercury in a thermometer acts upon a relay and sets in motion a wheel, Which makes and breaks the electric circuit by a series of contacts. Impulses are thus sent through an induction coil and the usual transmitting apparatus. The receiver at the engine-house includes air and earth conductors, coherer, battery and Morse instrument. The same receiver can serve many transmitters, and, as the contracts on the wheel can be varied, the exact location of the fire can be indici^d. THE PHOTOGRAPHS ACTIOJ* OF RADIUJff. The results of an investigation into the photographic action of radium radiation were laid before the Physical Society's meeting by Mr. S. Skinner. It was found that when ordinary photographic plates were exposed to the influence of radium bromide the intensity of the image produced increased rapidly with a longer time of exposure, then decreased gradually until a stage was reached when practically no dark image was formed on development. A striking resemblance is here found to ordinary photography, where, as is well-known, over-exposure involves a fainter image. Further, there seemed little doubt that the impression was produced by the Beta and Gamma rays only, for the Alpha rays must have been absorbed by the mica plate that was interposed. A still further resemblance in the radium influence and that of ordinary light lay in the observation that a plate that had been exposed to the bright light of an electric spark, if further exposed to radium bromide, underwent a complete reversal in the image. I JHODEL OF A NEW AIRSHIP.

There was on view in London recently the model of Mr T. L. Andersen's new airship. The principal feature of the vessel lies in the use of twin balloons and the placing of the power exactly in the centre of the frame supported by them. In this way the machine neither rolls nor dips when it is travelling. The balloons are of the usual shape, and so made that it is possible to transfer gas from one balloon to another, while in the case of an accident to one balloon it would be possible for the aeronaut to descend by the" other without accident. The model is 7ft. in length, and weighs about 30 ozs. The two propellors are made slightly pliable, the idea being, of course, to imitate the texture of a bird's wing ac closely as possible. The airship is steered from the centre by a wheel. The model is made to scale, and it is estimated that the complete vessel would be 75ft. by 30. The propellers would measure 30ft. from tip to tip, and a 50 h.-p. motor would enable the aeronaut to travel from fourteen to twenty miles an hour. The estimated cost of the complete ship—which would be capable of carrying a weight of 4,0001bs. — is £2,000. POWELLISED WOOD. Filling the pores with sugar has somewhat surprising effects upon wood. The process, as devised by W. Powell of Liverpool consists in immersing the wood in heated sugar solution for some hours, the time varying with the wood, and then drying it in an oven. No previous seasoning is necessary. The spongy fibre is converted into a compact ligneous substance, and it acquires greatly increased durability and strength, with resistance to changes of temperature and moisture, and even to fire. A special advantage is that the softer and cheaper—and even defective—woods can be made to serve many purposes in place of expensive hard woods. The sugar does not dissolve out, and it does not promote fermentation and the growth of destructive organisms, but it produces some remarkable chemical or physical transformation in a manner not yet understood.