SCIENCE SIFTINGS

New Zealand Tablet, 25 April 1918, Page 46

SCIENCE SIFTINGS

By “Volt: m

Ingenious French Invention. One of the best defences against the attack of modern infantry has proved to be wire entanglements,' thousands of miles of which guard the fronts of opposing armies in the present war. Whenever a good defence is found, however, the human brain sets to work to find some means of overcoming it. So well made and so intricate have been the entanglements that the highest explosives have sometimes failed to clear a way, and the French have hit. on an invention. This is a gun which fires a special heavy four-bladed knife. The knife revolves when fired, and cuts a way through the strongest entanglements, so opening a way for a bayonet charge. It has the great advantage over all other methods that it does not involve any risk to the soldiers, who formerly had to place the explosive bombs beneath the wire, with every chance of being shot while doing so. Clock Which Times Speeches. On the Speaker’s desk in the United States House of Representatives is a little clock-like machine; with a dial graduated in minutes from one ■=■ to six and a single hand that goes once round the dial in six minutes. This is started and stopped by a tiny lever, at the top. The Speaker uses it in timing members in a debate wherein the speeches are limited. The inventor, Mr. C. H. Graves, of Philadelphia designed it for keeping time on long-distance telephone calls, which are limited to three minutes. At the bottom of the dial is a scarlet mark. When you-get .your connection over the wire you press the little lever, which stands at O, and set the machine going. When the pointer is approaching the red mark you know your time is rapidly drawing to a close. It is astonishing how few persons have any idea how long three minutes are. Nine out of ten will hurry their long-distance calls so that they use far less time than they pay for. Mr. Graves has calcu-. lated that of the .£23,200,000 spent annually for longdistance calls £12,400,000 is wasted, for in the average call only 1J minutes are used, while three minutes are paid for. Old Iron at the Front. Considerable speculation has been going the rounds as to the amount of scrap iron and steel that is accumulating on the battlefields of Europe, and how it is to be disposed of. American companies which regularly deal in such old material have for some time been looking forward to the harvest to be reaped from these battlefields after the war. These hopes have now been rather rudely shocked by observers recently returned from the Front, who state that this matter is now being handled by the respective Governments. According to the systems now established in modern warfare, it is stated, a salvage corps is daily going over all the ground near the battle front exposed to fire, and is gathering all the debris discarded by the contending armies. None of the scrap is neglected, with steel worth Id to lid per pound, and copper and other metals in proportion. All the metals are taken to shops in the rear, and there worked into the various munitions that a modern army uses. All the lead that is fired is practically lost, as a bullet travelling at , a velocity of 2000 feet or more per second buries itself so deep into any object it hits as to be lost entirely. Other metals, however, such as tangled steel from wrecked motor-cars, large pieces of shells, bits of copper, pieces of aluminium, etc., are carefully collected and later turned into usable condition. . * * . - - '