SCIENCE SIFTINGS

New Zealand Tablet, 31 March 1921, Page 46

SCIENCE SIFTINGS

(By “Volt.”)

Photographs of Air. A new method of photographing rapid currents of air, their size, shape, and direction has been worked out at the Cook Aviation Field, Ohio, and a newly-found means of rendering air visible to the camera makes it possible to obtain pictures of many of the air currents connected with aeroplane flight which have been up to the present chiefly a matter of surmise. By means of a wind tunnel, through which air is forced by a 200-horse-power motor, gales of wind rushing along at a rate of 500 miles an hour can be generated. Not only are instantaneous photographs of wind and air currents obtained, but also cinematograph pictures, which reveal secrets likely to prove of great value in helping with the safer construction of aircraft. The secret of making air visible to the camera is a simple one. Moist air is used, and, by causing it to expand rapidly through suction, the moisture condenses and appears like a cloud. The minute particles of water condense owing to the presence of dust, and fine dust is accordingly introduced into the wind tunnel. Getting clear photographs, once the air is made “cloudy,” is an easy matter, thanks to the recent advances in the preparation of photographic plates. The Camphor Tree. There are still large tracts of virgin camphor forests in Formosa. Camphor trees grow best on moderate well-drained slopes, not over 4000 feet in elevation, when the sun’s rays can reach them. Nowhere else in the world have these trees attained such height and girth. In the past, trees with a basal circumference of from 35 to 40 feet have been noted, but these have inevitably fallen victims of the woodman’s axe. Perhaps, in the uncharted forests, where the savage still holds sway, more of these noble specimens still grow unscathed. At present a camphor tree with a basal circumference of 20 feet is considered a very ample specimen. In point of view of value (explains a writer in the National Geographic Magazine), few trees can rival the camphor. An average tree, say with a basal circumference of 12 feet, will yield about 50 piculo of camphor (approximately 66G0i, which, at the present market price, is worth about £IOOO. Strictly speaking, there are no camphor forests, as the camphor laurel is only one of a number of trees growing together. hiative stills are scattered here and there throughout the districts, where crude camphor is collected, packed in tins, and carried down precipitous mountain paths on coolies’ backs to the nearest railway line, whence it goes to the refinery at Tahoku. The camphor trees are unusually beautiful, with shapely trunks and widespreading branches profusely covered with graceful leaves of a soft green. According td an article appearing recently in a semi-official pub-* lication of Formosa, the camphor produced in the island at the present time is obtained entirely from naturalgrown camphor trees, the supply of which, it is anticipated, will be exhausted within ten years. For more than a decade, however, the camphor monopolygbureau has been planting camphor trees at the rate of more than 3000 acres a year. In 1919 its programme was expanded to more than 12,000 acres, and this will be the annual acreage planted in future. The adze is used in reducing the camphor trees to chips, which can be placed in retorts for the distillation process, as the camphor vaporises, it passes through pipes into submerged vats, which are so arranged that cool water from a mountain spring can flow over them to hasten crystallisation!In recent months the demand for Formosa camphor has been exceedingly heavy, especially among celluloid manufacturers. For the three months of 1920 the Japanese Government allotted to the United States 379,6351 b.