Science Siftings

New Zealand Tablet, 6 April 1916, Page 45

Science Siftings

By ‘ Volt.’

Life of. a-. Battleship.

Naval experts*, put the active : life of a modern battleship at ‘ about fifteen years. - A hundred years ago battleships ’ lasted - nearly six times as long, and were on active service nearly the whole time of their commission. The Victory,- for instance, was forty years old when she acted as Nelson’s flagship at the memorable Battle of Trafalgar. A line-of-battleship, the Royal William, was built at Chatham in 1670, and was not broken up until 1813, being ‘ rebuilt ’! several times before her final demise. , Why the Stars Twinkle. Although the twinkling of the stars is commonly' referred to, they do not twinkle at all. . The stars are really suns that throw out light, just as our , sun V lights the earth. When the rays of light from the stars strike* the air which surrounds the earth they have to pierce many little particles which are always floating about in the atmosphere. It is this interference between us and the source of light which gives the appearance of twinkling. On certain nights the light of the stars will appear so bright and clear as to attract particular attention. This is because the air is so clear .there is less interference than usual with the rays of light in reaching the earth. 7 Your Wrist-Watch. Your wrist-watch is a marvel of minute workmanship. It is one of the most wonderful things the human hand fashions (says an exchange). The pivot of the balance-wheel has a diameter measured by the twohundredth part ,of an inch, and, more marvellous still, in order that the pivot may have free play, the jewelhole into which it fits is exactly one five-thousandth part of an inch larger.'; 'The gauge which enables this to be done measures to J the ten-thousandth part of an inch. But not only are the screws of a watch as minute as its bolts, but they have a thread just like the big screws you drive into the door, but the thread of the watch’s screw has as many as 260 turns to the inch. What is called a pallet jewel in a watch weighs a pound when there are 150,000 of them, and of the roller jewel it would need 256,000. ' The largest round hair-spring stud in your watch is the four-hundredth of an inch in diameter and nine-hundredths of an inch in length. Submarine Rescue ■ Device. V One of the recently-invented submarine-rescue devices is designed to furnish the imprisoned crew a supply of air and also extend a line to the surface of the water for facilitating the rising of the disabled craft. An important part of the apparatus consists of a collapsible box containing an air bag, which when inflated rises to the-surface; carrying with it a swivel-join pipe $ within which is a hose. The air for this lifting chamber is taken from the submarine, but as soon as it . reaches the surface the pumps in the submerged boat may be set at work sucking in oxygen. A cord which is tied to a cable attached to one end of the craft is fastened to the box. By pulling this up the rescuers are able to obtain a heavy line with which the submarine may be raised. ? Wires carried by the box establish telephonic communication between those under the water and the rescuers. . 5 ■ , ; i! ; ’ S; How Italy Prevents Frost-Bite. ! f Many problems have had ,to be faced by the army in Italy, one of the most pressing being the prevention, of frost-bite amongst the thousands of men exposed to ; the .rigors of the alpine winter. An interesting experiment 7 which gave good results was as follows. A soldier,, whose feet had been well smeared-with sterilised fat, put on a double sock of cotton, having an interlining ?of I paper’ also- prepared, with fat,’ and over this ; an: ordinary woollen sock. 5 He' then stood 'in a pail of ice 7 for forty minutes, and at the end of the time his feet

are said to have been normal in appearance; nor did he complain of any unusual sensations. Another footcovering which is proving of, great value in resisting the bold is. a square of linen,- prepared in a solution of salicylic acid and - sterilised fat, over which may be worn either a woollen or a cotton sock. The prepared squares are enclosed in small waterproof envelopes, and are thus easily carried in the pocket. Thousands of these squares have been sent to ; the front. - '