Science Siftings

New Zealand Tablet, 5 August 1915, Page 51

Science Siftings

By ‘ Volt.’

World’s Strongest Cable. All records for cable strength are said to have been surpassed when a 3iu steel cable withstood a prilling test of 751,6001 b, or practically 376 tons. This cable is to form part of the longest and strongest hoisting cable in the world, and is to be used in a mine in Cuba.. It weighs 15.71 bto the foot, and is made in lengths of 8000 ft. This cable has a hemp centre, around which are wound six strands consisting of nineteen steel wires each. Making Aeroplane Wings. Various kinds of material, including linen, silk, cotton, celluloid films, and aluminium foil, have been tried for covering the wings of aeroplanes, but none has proved so satisfactory so far as linen covered with several coats of a rubber solution. This coating increases the strength of the linen about 5 per cent., makes it more enduring under varying weather conditions, and causes it to stretch to an absolutely smooth surface, a feature that is of the utmost advantage in fast flights. Silk, which would seem to make an ideal covering on account of its lightness and strength, has been found unsatisfactory, as it does not withstand exposure to sun and rain, and does not lend itself readily to the application of coating compounds. Old Time Sealing-Wax. Interesting results have been obtained by the Government chemist by making analysis of old wax impressions on documents in the Public Record Office. The seals examined dated from the thirteenth to the eighteenth century, and differed but little from modern sealing-wax. Most of them consisted of a mixture of beeswax and resin, others of pure beeswax. Two seals, of the dates 1399 and 1423 respectively, were composed of wax the characteristics of which agreed more nearly with those of East Indian than of European beeswax. The wax composing an impression from the Great Seal of 1350 agreed, in chemical and physical characters, with pure beeswax of to-day. The pigment in the red seals was vermilion, while the green seals contained verdigris. Decoy Periscopes Used. Such things exist as decoy periscopes —short lengths of pipe held upright on a float and looking exactly like the real periscope. The submarine sets them adrift for you to find -sometimes scatters several of them'. When one is sighted you cannot stop to consider whether the little object dancing on the sea. half a mile or so distant does or does not mean 2501 b of high explosive coming straight at you. Maybe you will see an aeroplane manoeuvring over it in a way that carries conviction that it does. You don’t dare to take any chances, and so you train all the guns at it. Then the real submarine slinks up on the other side of the ship, and with the swift rush of its torpedo the latest of sea tragedies comes to an end. How Panamas Are Made. About 15,000 Panama hats are made annually by the women of Santa Barbara, Honduras. The most tender palm leaves, called ' junco ’ leaves, are selected and exposed to sulphur smoke, moisture, and the rays of the sun, and two dozen leaves, costing 9d are needed for each hat. A round block, called ‘ horma,’ is used as a form for making the crown. After this part, is finished a table is used, provided with one or more holes, into which the crown is dropped and the rim woven on top of the table. These hats are sold at from 4s fid to =£2, according to their quality. They are made during the wet season, as the straw breaks during the dry. Even in the wet season a damp, cloth is con-, stantly used to moisten the straw whileweaving. When they are finished they are placed in a large box, and again subjected to sulphur fumes, after which they are ready for the market. It generally takes about two weeks to make an ordinary Panama, and a month for a fine one.