is, and many other places.
It does not appear that Dr. Papin tried the direct pressure of a body of air upon the water; in a manner similar to the pressure of steam upon the surface of the water in the so-called steam-engines of Baptista Porta, 1600; De Caus, 1620; Marquis of Worcester, 1655; Savery, 1698.
See steam-engine. For many years past — probably a century or more — water-elevators operating by condensed air have been used at the mines of Chemnitz in Hungary.
A high column of water is used to condense a column of air in a pipe, so that the power of the apparatus is proportioned to the vertical height of the fall which is available.
In the mountainous districts of Central Europe some remarkable falls are thus utilized, some of which are referred to under turbine. In the Black Forest of Baden turbines are running with falls of 72 and 354 feet, and having diameters of from 20 to 13 inches respectively.
In the figure, the vertical elevation i