Air-engine

Using the elastic tension of air as source of power. The air must be first compre ed to a high tension, and will then be used partly by expansion in the cylinder of this engine. The air can be carried a considerable distance in pipes, so as to avoid the inconveniences of escaping steam and of products of combustion in contracted spaces underground, etc. It is impo ible to carry expansion very far on account of the low temperature of the exhaust, which would be enough to freeze any moisture in the air and clog the engine. The combined efficiency of the compre or and air-engine is le than 40 percent when the compre ed air is cooled between the two machines to the temperature of the surrounding air and objects. IMG:content-0068.png:[graphic] Air-lock. At Vincennes, near Paris, on a pa enger tramway 12 miles long, an air-engine is used, the air being compre ed at the ends of the line. and carried in steel cylinders beneath the cars. The pre ure is 45 atmospheres. The low temperature of expansion is obviated by injecting hot water. Eric on's hot air engine for light powers, three or four horse powers, has been succe fully used. The furnace is within the cylinder. Tests made in Paris showed that it consumes nine lbs. of coal per horse power, twice as much as a good steam engine. Air-gun. Invented by Guter of Nuremberg ab. 1656.