SCIENCE SIFTINGS

New Zealand Tablet, 11 October 1917, Page 46

SCIENCE SIFTINGS

T' ♦ . " - ■ By “Volt.”

A cable from Ottawa states that the central'; span of the new Quebec bridge has been placed in position £ after the greatest engineering feat of the kind, involv- v ing a three days' lift of the span from pontoons. The .;. work was carried out without a hitch. The bridge was 7 the scene of * disasters in 1907 and 1916. . . The widespread impression that people living in a primitive condition possess more acute vision than civilised men enjoy receives a little support from the investigations of Dr. Rivers during the expedition to Torres Straits and New Guinea. The visual powers ; of the people there were found to be superior to those of :'■]* normal Europeans, although the degree of superiority ;}; was not great. The natives of Torres Straits could v, see better in the dark than most Europeans can. Their sense of touch was also slightly superior, and in the 7 discrimination of weight they were more accurate than <v a practiced European. . Dr. Rivers ascribes their acuteness of vision to their habits of constant observation. The largest and most beautiful opals in the world are found in Australia, but, according to Mr. Percy : Marks, of Hunter Street, Sydney, who has specialised in opals, the gigantic specimen which has been discovered in South Australia is probably the largest of \ its quality ever found. The opal, which is of the harlequin variety, comes from new opal fields in the | Stewart Ranges. When it is considered that a piece of ;| opal of this quality weighing an ounce or so is a big lump, the present find, weighing 44foz, or 6600 carats, fc. is a wonderful size. Even in the rough state, un- |&§ touched by the wheel, the stone seems a mass of opalescent color. Until the opal is cut it is difficult to say what it will be worth. * Modern Artillery. '-',.{ The actual horse-power developed during the firing \ of a projectile of modern artillery is truly astounding. 'f In the case of a cannon of moderate size, projecting a "■■■_.s projectile weighing 7 kilogrammes with an initial 'J velocity of 500 metres, the deflagration of the explosive I lasting about one hundredth of a second, we have, ■'s during that time, work done to the extent of 115,000 •— M horse-power. For larger artillery, where the weight of || the projectile reaches and surpasses 500 kilogrammes, : M the. initial velocity being 900 metres, we have no less y | than 25 million horse-power developed during the ex- || plosion. ,v! Possibilities of Wireless. -.-• |p| As an illustration of the wonderful results which v can now be obtained from the use of wireless telegraphy, if Commander Ores well, of the Australian Navy, mentioned rJ] when lecturing before the members of the United Ser- ;.| vice Institute in Melbourne recently, that messages sent out from Germany were being daily intercepted at . v-v: : receiving stations at Perth and Sydney. The distanceto the Perth station was, approximately, 7000 miles, while to Sydney via America, across which it was presumed the sound waves travelled,- the " distance, was about 12,000 miles. The receipt of messages at this 7 ; i range, it was stated by Commander Creswell, consti- . -, tuted a world's record. He explained that owing Ho'*: >; the effect which light had upon wireless waves, German, messages only reached Sydney when they were trans-'.;'■./?? mitted at night. The distance :to Perth being, how- ; ever, some thousands of miles shorter; ; the West Australian station caught and recorded messages sent out ,<: from. Germany either by night or day.' Commander ~ Creswell added that while these remarkable -achievements had become possible solely as the result of the . >; great developments which had taken place in the science - \< of wireless telegraphy", an important part was played v J by the operators, iand it \ was largely due to their skill that German messages were being intercepted and interpreted 'by Australian stations.