Science Siftings

New Zealand Tablet, 31 March 1910, Page 515

Science Siftings

BY • VOLT*

A Problem Explained. - The deep sea is bine because it reflects the blue rays of light j but shallow bodies of water seem green because this blue light is mixed with yellow reflections from the sand and stones at the bottom, green being a mixture of tints. - Match-using Expensive. The American people use up the enormous total of 700.000. 000,000 matches a year, but a statement of the number of cubic feet of wood actually converted into matches conveys a very indefinite idea of the number of trees required for the industry. It is the general belief that matches are' the by-product of planing-mills and other wood-working factories, but as a matter of fact the best grade of two-inch lumber is used for matches, while sash, doors, and blinds are the by-products of the match-timber sawmills. In a single year the manufacturers cut 225.000. feet (board measure) of pine in the great lakes region and one of the one hundred and fifty odd factories used up 200,000 feet of sugar or yellow pine logs every day. The deduction is that, in common with other industries of the United States depending upon existing forests, the match-makers are within sight of a shortage in the wood supply. When the present timber holdings have been depleted they, of course, cannot be duplicated in a generation, and the people of the United States may have to get along with fewer than 25 or 30 matches a day each as at present. In their insistent way they will probably demand that the practice of Germany and France be followed, that foresters plant and grow timber especially for matches. This could readily be done if forests were placed under management and were no longer left to run wild, and produce cordwood and brush to fall before the devastating forest fires, instead of growing merchantable timber. A Giant Shed for Dirigibles. Says Alfred Gradenwitz in La Nataire (Paris, November 20): .‘The new balloon-house of the Zeppelin Company at Friedrichshafen, which is notable for its huge size, is destined to serve, not as a garage for aerostats, as has been frequently affirmed, but as an aerial workshop for aerial construction. Thus it has as an annex a great factory where the various parts of dirigible balloons will be made. ‘ The house is intended to shelter, during construction, two dirigibles of the largest type, and it has imposing lines (650 feet long, 100 feet wide in the lower part, and 65 feet high in the centre). Its form was selected with a view to reducing interference with the contents to a minimum, without endangering the stability of the building. ‘To keep the space within, as far as possible, from the influence of the sun’s rays and other meteorologic factors, which might cause rapid alterations of volume in the balloons and promote leakage of gas, the builders have chosen a covering for roof and walls, a substance of slight conductivity for heat, and So.light as not: to overweight the structure. The roof is made of a layer of cement 3 inches thick covered with rubberoid; the walls are of iron network. The longitudinal walls have a doub’e layer of masonry with a non-conducting -layer of air between. The transverse walls, which are made to operate as gates and are consequently of extreme lightness, are erf galvanised iron on the outside and of cloth within, with .an air layer between. ‘ln order to draw off quickly the gas that escapes while a balloon is being, filled, there has been built at the top of the structure a lantern extending for its whole length, and, having a ventilator for geting rid of the interior air. 1 That access to all points of a balloon in process of construction or repair may be as easy as possible, there have been placed at the sides of the structure portable working galleries extending along its whole length, and stationary bridges fixed on both sides of the hall. ‘The Zeppelin Company required as an indispensable condition that the two ends of the building should be constructed as to give clear passage, in as brief a time as possible, to the balloon within. The portals were thus built large enough to permit the rapid opening and closing of a section 65 feet by 140 feet. This condition was the most formidable • part of the work. ‘ The gates are operated by electricity; the surface of each include four sections, 65 feet high. The two central sections have the form of sliding doors and the two lateral ones that of folding doors.’