Читать книгу Inventors at Work, with Chapters on Discovery - George Iles - Страница 35

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The screw, an inclined plane wound about an axis, forms the propeller for steamships and many steamboats. There is a good deal of debate as to the principles which should decide its best lines. Here evidently is a field which will handsomely repay thorough investigation. The power expended in steamships, whether fast or slow, is prodigious; any marked improvement in the contour of screws will mean either a saving of fuel or an increase of speed. Of equal importance with water-propulsion is the setting in motion of air. In blast furnaces enormous volumes of air are forced at high pressure into the fuel and ore: the fans are carefully molded in screw form, any departure from the best curves entailing serious loss. Fans for less important services are seldom shaped with care and usually waste much energy.