SCIENCE SIFTINGS

New Zealand Tablet, Volume LI, Issue 43, 15 October 1924, Page 54

SCIENCE SIFTINGS

j /.■■raajp By ~VOLTr >

Clock as Money-Box. A- savings bank in the United States is making a present of a clock to every new depositor. It is a timepiece of a peculiar kind, "and is. really a combination of a clock and a safe. It needs re-winding every twenty-four hours, but before it can be re-wound a coin must be inserted. The owner is thus compelled to add something to his savings every day. Water You Can't Sink In. >•■■" Everyone who has swum in a lake or pond as well as in the sea knows the extra buoyancy of salt water as compared with fresh. This effect of salt'on water is demonstrated strikingly at Droitwich, the Worcestershire spa, where there is water in which it is impossible to sink. You can float on the water, sit on it, and even go to sleep on it, without fear of drowning. The better the swimmer you are, indeed, the worse you will fare, because the moment you try to strike out your feet fly upwards, to give you an unpleasant emetic! So high is the percentage of salt that the crystals completely coat the skin, unless drying is resorted to immediately on leaving the water. Some of the cures effected by the baths are remarkable. Anaemia, neuralgic ailments, and rheumatism sometimes yield as if by magic under the treatment, which is becoming increasingly popular. ■Engineering Feats That Bring Prosperity. In view of the work now being undertaken by the Dunedin City Council to construct a lake or huge reservoir for the additional storage of water for its electrical power and lighting system on the site of the old Waipori mining township (built on the hillsides and valley of the selected locality), the following extract from Tit-Bits, London, describing similar (although on a much larger scale) undertakings, should prove interesting: Among modern engineering feats the building of the great dam of Tirso, Sardinia, opened recently by the King of Italy, sanks as one of the most imposing. The second largest dam in the world, it is 722 ft long and over 200 ft in height, the artificial lake formed by it containing 30,000 million gallons. The'" biggest of all dams is that at Assuan, in Egypt, where, after years of failure, a great wall, nearly a mile and a quarter long, was built across the Nile by a British firm, at a cost of £2,000,000. The building of this wall created a mighty lake nearly 200 miles in length, containing 10,000,000 million cubic feet of water, which _is emplayed for irrigation purposes, converting into rich soil land that was formerly useless. Valley Becomes a Reservoir. In the United Kingdom the best-known dam is that forming Lake Vyrnwy, North Wales, which covers what, up to a few years ago, was a beautiful valley containing several villages and hamlets. The need for storing water for use in certain big industrial centres of the North resulted in the conversion of the peaceful valley into a vast sheet of water, having an area of over a thousand acres and a capacity exceeding 12,000 million gallons. Considering the enormous pressure imposed upon them, it is astonishing how few dams have failed. One of tho worst disasters of the kind occurred -near Epihal, France, where a great dam slipped from its foundations and actually overturned, causing great loss of life. The exact cause of the catastrophe was never determined. T Although big dams are being built almost every month, we still know surprisingly little about the factors that govern their safety. -..-