SCIENCE SIFTINGS

New Zealand Tablet, 3 April 1919, Page 46

SCIENCE SIFTINGS

The Diving Tank.

A new species of diving-bell which has been invented in America for salvage operations is described in Engineering.. It is intended for deep-water work, where the existing diving apparatus is useless, and it is a pear-shaped steel shell 9ft long and 7jft in diameter, which can stand a tremendous pressure. It accommodates two men, who have air sufficient for twenty-four hours stored in bottles under pressure. In some respects the diving-bell may be compared to a submarine “tank,” for by an ingenious -arrangement of electric magnets the machine can attach itself to the side of a sunken, vessel, and it can also creep over its surface. These magnets, which have each a holding power of two and a-half tons, are mounted on pairs of horizontal or vertical screws, the power supply for operating them being obtained through a flexible cable from the surface. By cutting out one set of magnets the remainder can be used as an abutment and the machine warped backwards or forwards or up and down by turning the screws, and when the latter are at the limit of their travel the magnets previously cut out are energised again, and when they have attached themselves in turn to the hull, they serve as an abutment for another movement. The amount of motion in any direction is registered inside the hull, so that holes can be drilled accurately in desired positions, and then, by warping the machine, another tool can be brought to register accurately with a hole thus drilled. The machine can put a steel plate over a hole, can drill and tap holes through both plate and hull, and screw in set-bolts. On the outside of the hull four 3000 candle-power electric lamps are mounted in globes fitted with strong guards. Windows and bull's-eyes allow the crew to examine their surroundings by the light of these lamps. The machine has been tested in New York harbor at a depth of 105 feet.

Spotting Big Guns.

As the British air pilot on gun-spotting work flies from his aerodrome to cross the lines, he may or may not be able to identify the battery which will receive his wireless messages. Its queerly-painted guns are covered with brushwood, the up-turned earth has. been resodded and levelled, and the battery is so placed that tracks to and from it do not show. But if he does not know his battery the pilot at once recognises its target, which has been precisely located in advance on his map, and circles high above it. The observer signals to the battery that he is in position over the target, and the battery opens fire, at irregular intervals, so as to confuse enemy detection of the source of the bombardment. At last comes the wished-for message from the air, “O.K.” —a direct hit—and the battery continues its fire till word comes along from the observer that its work is done. By preparing his message with the special code-letters which identify him to the battery he is addressing, the pilot on artillery reconnaissance is able to communicate full instructions to the gunners ip the minimum of tiipo-