SCIENCE NOTES.

Otago Witness, Issue 2310, 9 June 1898, Page 48

SCIENCE NOTES.

• . • Perchoid is a new product, and a substitute for gutta percha, the supply of which has, of late shown such disquieting signs of collapse. Perchoid, the invention of Dr Napier Ford, is oil which has undergone a high degree of. oxidation. Dr Ford experimented tor many years to produce a method whereby oil could be fully oxidised, and at last he succeeded. The result is perchoid. The oil is heated with/litharge, stirred long and continuously, and then allowed to cool. Specially prepared tow is then dipped in it, and, placed in wire baskets, subjected to currents of air. The oil adhering to the filament* of the hemp becomes wholly oxidised. Under the microscope the hempen threads appear sheathed with a coating of amber. This is done through rollers and comes out as a leathery material, closely allied to, if not identical with, rubber. Its tenacity is increased by mixing it with sulphur. It can be rolled as thin as a piece of tissue paper and any fabric, and it makes leather impervious to moisture, though not to air. It is said to be eight times cheaper than rubber and more durable. One of its great fields will probably be the making of pneumatic tyres. It is stated that a chemical manufacturer in London, whose hydrochloric acid tank need to be lined with gutta percba at a cost of £10, had a lining made of perchoid for 6s, which serves just as well. Perchoid should be a godsend to the electrician, as it never becomes brittle, and never leaves the wire, two moßt valuable qualities in an insulator.

• . • A new process for preventing the decay of wood baa recently been introduced and extensive works set up at Millwall for treating timber. The inventor, Mr Samuel Edward Haskin, has been engaged for the last 20 years in experimenting and perfecting the process in America. Hitherto the method adopted for preventing wood from decay has been by the withdrawal of the sap and the injection of creosote or other antiseptic substanoes. The Haskin procjeas, on the contrary, retains the sap, bat destroys its germinative principle. To procure this result the wood to be treated is placed in a cylindrical heating chamber and submitted to a medium of superheated air at a pressure 14 times as great as the normal pressure of the air. The substances composing the sap are by this means chemically changed and form a powerful antiseptic mixture, which becomes consolidated with the fibre, thus strengthening and preserving the wood. * . ■ A cold obisel for heavy chipping should be sharpened vligbtty oral in round*

ing. A tool sharpened thus will stand harder usage than when the cutting edge is concave, or even straight. The reason for this is based upon the strength of the arch. The engineer builds a dam across a stream in the shape of a curve for the same reason, and both the engineer and the beaver, in his native stream, obey the same law in regard to thi9 matter. Aside from the principle of the arcb, there ie less danger of breaking the cornern off of a chisel when the edge is cuived, for then the force of the blow is supported in a brace-like manner by the metal in the curved corners, whereas in the concave point the same bracing action, applied in the opposite direotion, tends to split off the corners of the tool. The matter is so simple that every machinist shonld take advantage of it to add strength and durability to bis tools. The same chape can be given "to screwdrivers when they are to be used in chuck? ow work like that of putting screws into shoemakers' lasts. • Thousands of screws are thus put in, and it is found that if the end of the screwdrivei is rounded off the least possible amount it is much easier to make the too) bit eßgage the slot in, the screw, Whet? the bit is the least amount concave on the end, it is impossible to make the screwdrive; take bold when running .even at a lovr working speed. Make, the end of the tool convex one- f .hirty-s6cond of an inch, and the speed at which the tool can be put into a screw slot wiU be doubled.

• . • One of the difficulties which water engineers have to face is the unpleasant odour which sometimes characterises surface waters "stored in open reservoirs. Such odours are frequontly supposed to be due to the decomposition of organic matter in the water, but, although sach be the case, io many instances they have been found to be attributable to the growth of microscopical organisms, and quite a long list has now been furnished of vegetable growths which impart disagreeable tastes .and smells to water. Messrs Jack?cn and Ellms bave just published a memoir describing their investigations upon one of the Cynophycfje or blue-green Aigse which, when growing in water, impregnates the latter with a most unpleasant mouldy grassy smell. Pure cultures of AnabEena circinalis, an importaat offender in this particular, were obtained and numerous experiments were carried out. As in the case of other microscopical waterorganisms, the odour emitted during growth ■ was found to be due to the presence of certain compounds of the nature of essential oils, which make their appearance at a particular stage of growth. The investigation was also extended to &n ax*taisa.tion of these AnAhsana. daring decay, a most offensive odour being given off during decomposition. This the writers' tfaiuk is probably due to the high percentages of nitrogen which these growths contaiu. The gas given off. during decomposition was analysed, and was found to contain a large percentage of hydrogen and a considerable proportion of snlpbur compounds, Analyses of the decayed gelatinous material te^ulting from cne decomposition of Anabssaa revealed the presence of a large amount of sulphar ard a considerable amount of phosphorus: The subject is of such importance in connection with fehe storage of surface waters that the closer study of the chemical composition of these organisms, and of the organic and mineral contents of the waters wbich the various genei'a infest, is well worthy of attention, for by extending our knowledge in thiß manner we should be better able to judge beforehand of the likelihood of particular waters becoming gubjecs to these unpleasant changes on storage. — Technology Quarterly, Massachusetts.

• . • The phonograph is now used to teach foreign languages. With each phonograph the pupil receives a text-fceok and 20 loaded cylinders. Each lesson in the book is arranged in the form of questions and answers. The pupil, ready to begin, puts the cylinder of the first lesson in the machine, the tubes in his ears, and starts the phonograph. Keeping his eys on the bookfhe hears the words and phrases repeated, with their proper accent, just as if the professor stood at his side. There is the additional advantage that the Issgon can be repeated 20 or 100 times if necessary, until every sound is familiar to the pupil.

• . • Nothing among the many marvels of modern invention is more astounding than the recent discovery by Herr Johann Mayer, an Austrian lieutenant, of a method by which the moon can be brought within a distance of 100 yds, and all her secrets explored more thoroughly than , the map of London from the top of St. Paul's. Professor Gates's combined microECope and telescope, which brought the moon as near to him as Brighton is to London, was considered a marvellous advance in telescopic science, but within a few months Herr Mayer has put the professor's discovery quite in the 3hade. Herr Mayer has made a startling departure from recognised methods, and the monster telescope, with its 403n lens, has no part in his apparatus. Without entering into lengthy and technical detail, the novel part of Herr Mayer'6 apparatus is an enormous parabolic mirror, 50jds in diameter, which revolves on a fixed axis. This concave mirror, which is of the ordinary " silvered" glass, has a small convex parabolic mirror suspended at its focus ; and this small mirror focuses the rays received from the larger one, and throws them on the lens of an immensely powerful microscope. In ' this way a clear and brilliantly-lighted picture of the moon or star is brought immediately under the microscope, which has a magnifying power of many million diameters. It will thus be possible almost to see the time by the watch of the " man in the moon," or to see the barges (if any) on the canals of Mars.

— There are at the present moment 875 commission ad officers in the British Army who have risen from the ranks.

Advice to Mothers I—Are1 — Are you broken in your rest by a sick child suffering with the pain of cutting teeth ? Go at once to a chemist and get a bottle of Mrs Winslow's Soothing Syrup. It will relieve the poor sufferer immediately. It is perfectly harmless, and pleasant to the taste ; it produces natural quiet sleep by relieving the child from pain, and the little cherub awakes "as bright as a button." It soothes the child, it softens the gums, allays all pain, relieves wind, regulates the bowels, and is the best known remedy for dysentery and diarrhoea whether arising from teething or other causes. Mrs Winslow's soothing Syrup is sold by medicine dealers every, where at Is lid per bottle.— [Ajm ]