SCIENCE SIFTING

New Zealand Tablet, 10 May 1917, Page 47

SCIENCE SIFTING

By ‘Volt.’ At a range of 1000 yards a bullet arrives at least a second, and sometimes more, in advance of the report. The sound of the flying bullet is caused by a vacuum at its rear. The air thrown fiercely back from the nose of the projectile travels round and rushes to the rear, as water to the stern of a fast-moving boat. Thus a crash is produced — or, in certain cases, a kind of whining snarl, like no other sound on earth.

Concrete holds its own in the construction of our houses, or public buildings, our bridges, our monuments, and now even in our ships. Harbored safely in Norwegian water is an enormous thousand-ton barge, built entirely of concrete ; a 70-year-old skiff of stone floats merrily on the waters of the River Seine, while a concrete barge is daily towed up and down a certain portion of the River Thames. Utilising Sawdust. The Scientific Anu rican says that over 300,000 cords of slabs, sawdust, edgings, and other mill waste were used for making paper pulp last year. Several of the largest sawmills in New York State are installing special apparatus to save material which was formerly wasted or sent to the burner. The price of paper has risen so greatly since the outbreak of the European war that paper pulp manufacturers are becoming more and more interested in the utilisation of wood waste. When it is realised that more wood is wasted than actually utilised in the American great lumber industry, which uses 40,000,000,000 board feet a year, it is seen that there are great opportunities to save this waste. Guns that Fire Knives. 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 the opposing armies. Whenever a good defence is found, however, then human brains set to work to find some means of overcoming it. So well made and so intricate have been the entanglements, however, 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 rapidly when fired, and cuts a way through the strongest entanglements, so opening a way for a bayonet charge. ft has the great advantage over all other methods that it does not involve a risk to the soldiers, who formerly had to place the explosive bombs beneath the wire, with every chance of being shot while doing so. An Ingenious Device. An interesting description of the working of an American fruit-grading machine which has just been installed in the Nelson Co-operative Fruit Company’s packing shed at Tasman, is given by the Nelson Mail. The machine grades fruit into six sizes. A case of apples is emptied on to the head of the machine and the fruit is carried along a table on which there are travelling canvasses, the speed of which can be regulated. An attendant stands at each side of the table, and as the apples pass along they are sorted into ‘special’ and ‘good,’ and placed on other canvasses. The rejects are put on a third canvas and drop into bags underneath the table. -The special and good apples are carried along to a thrower, worked by powerful springs and projected into canvas bags. The fruit is thrown from 4ft to 14ft, according to weight, and from the bags the apples fall into binsspecial on one side and good on the other, and each class in six sizes. The machine is worked by a one horse-power Dandy petrol engine, and can put through well over 500 cases a day. There is absolutely no bruising— in fact, it is claimed that the machine could deal with eggs without breakages.