SCIENCE SIFTINGS

New Zealand Tablet, 23 October 1919, Page 46

SCIENCE SIFTINGS

(By ? "Volt.")

'.-■': World's Biggest Flagstaff. . ; ~ The flagstaff, measuring' 215 ft in height, which is to be erected shortly in Kew Gardens (London) : , is almost, though not quite, the biggest thing of its kind. The tallest flagstaff stands in San Francisco, where it was a feature of the Exposition in that city four years ago. It stands 222 ft above the ground, and was floated down the Pacific from Astoria, Oregon, whose citizens presented it to the Exposition. It) carries at its summit a Stars and Stripes 1058 square feet in area—the biggest flag ever flown. Lake that Disappears. In Georgia, near Vladosta, there is a lake which disappears every three or four years and then comes back again, no matter what the weather is like. The lake is three miles long and three-quarters of a mile wide, with an average depth of 12ft of water. There are natural subterranean passages beneath it, through which the water passes off. It takes two or three weeks to disappear, when a mammoth basin is left in its place, which furnishes a beautiful sandy beach. After a month or so the water begins to return, and then in a couple of weeks it is the same magnificent stretch of water as it was before. Why Does a Locomotive Engine Puff? Why does a locomotive engine puff? And why do some seem more asthmatical than others and puff more? It all depends on the size of the driving wheels, which govern tho number of puffs which the engine gives in a certain distance. For every turn of the wheel it gives four separate puffs. It has been reckoned that if the circumference of the driving wheels is 20ft and the train is going at 50 miles an hour, an engine, on an average, gives 880 puffs a minute. The puff is really due to the abrupt emission of waste steam from the smoke-stack. When there are more than 18 puffs a second the human ear cannot distinguish them separately. Stainless Steel. It was an accident which led to the invention of rustless steel. A certain Sheffield expert was experimenting to find a means of preventing erosion—or wearing away in gun tubes. After some experiments lie noticed that certain pieces of steel had not suffered from corrosive influences under conditions which would have rusted ordinary steel. Ho followed up this clue, and stainless steel was thus evolved. This new metal, with a bright surface, is able to resist the corroding effect of air, water, and acids without staining. It was immediately commandeered by the Government for use in aeroplane construction and for purposes where strength and durability, combined with rust-resisting qualities, were invaluable. Diving Dangers. Owing to the extension of salvage operations, divers have been in great demand during the war. t It is risky work, for the diver has to cope with pressure and its effects, with dangers to his airpipe, which, though very stout and strong, can be sawn through without his perceiving that it is rubbing against, say, a jagged plate or other rough surface. There is also the danger of coming up too quickly in case of emergency. On any accident to the airpipe, the diver has to get to the surface inside two minutes. This means that the change of pressure is very rapid and the effect on the blood very dangerous. In the ordinary way the diver comes up in stages, pausing at intervals to accustom himself to the new conditions. There have been attempts to turn him into a sort of submarine by the use of rigid suits. The drawback is that he is thus unable to work, and so far the problem of combining movement with something which will resist pressure does not appear to have been solved.