SCIENCE SIFTINGS

New Zealand Tablet, 3 July 1919, Page 46

SCIENCE SIFTINGS

(By "Volt.")

World's Fastest Submarine. . \ The fastest submarine vessels in the world were designed and constructed for'the British: Navy during the war. They were evolved in response to the demand for submersible craft which could keep station with the fleet when cruising, and also, undertake long voyages without the aid of "mother craft." Many new features were embodied in this class, which has proved itself a conspicuous triumph of British engineering. Unlike other submarines, they are fitted with steam turbines, ■which! are used during operations at a high speed on the surface. Secondary propelling power is obtained from a heavy-oil engine of 800 brake horse-power, which drives a dynamo supplying electricity either to electric motors geared to the propeller' shafts (for surface cruising at moderate speeds), or to electric batteries which store energy for propulsion under water. When submerged, these vessels have a displacement of 2570 tons. They are nearly 340 ft long, and have a double hull except at the ends. An exceptionally powerful wireless telegraph installation is fitted for long-distance work; the aerials are carried on long telescopic masts operated by a telemotor system. Electricity is also used for driving the air compressors and bilge pumps, while the steering gear and the hydroplane driving gears are controlled by a special hydro-electric system.

Examining Metals by X-Rays. The rapid development of electric welding in Great Britain, fostered by the Admiralty for ship construction and other purposes, has led to some highly important improvements in this useful means of forming a close union between plates and other sections of iron or steel. The British experts who carried out successful work of a novel kind have made excellent use of "flux-covered" metal electrodes. In this system the metal electrodes between which the arc for melting purposes is struck are covered with certain materials which flow under the heat of the arc and protect the metal from oxidation during the process. In welding steels alloyed with special substances, a flux can be used containing the alloys, thus supplying them to the weld as it is being made. By this means the weld is made uniform in composition with the remainder of the metal. Special attention is also being given by British engineers to the testing of welds by "radiometallography." The weld is examined under the X-rays much as a portion of the human body might be, and internal imperfections are thereby revealed, although they may be covered by a solid close-grained surface. Many British men of science are devoting themselves to research in this direction, which is calculated to be of great practical value to all users of metals. It may be recalled that Great Britain led the way in the microscopic study of the structure of metals— a study which laid the foundations of modern scientific metallurgy. ,