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Pneumatic expel it with this velocity. The weight of this column This table extends far beyond the limits of ordinary Pneumatic
is the least force that can be exerted by the engine : but use, very few blast-furnaces having a force exceeding Engines.
quantity of air by the feeding pipe PQ; this expels the
nitz in Hungary, for raising water from the bottom of
linder will be filled with water, because it is sunk so
deep that its top is below the usual surface of the mine-
waters. Now shut the cocks F, E, M, K, and open
by the orifice D, and rise in the upper cylinder, com-
pressing the air above it and along the pipe GHH', and
thus acting on the surface of the water in the lower 2.791 437 3.05 40
cylinder. It will therefore cause it to rise gradually 457 3.17 518 3.60 54
in the pipe IN, where it will always be of such a height 2 500 3.48 584 | 4.2 68
that its weight balances the elasticity of the compressed 3 544 | 3.76 653 4.53
air. Suppose no issue given to the air from the upper
cylinder, it would be compressed into one-fifth of its
bulk by the column of 136 feet high ; for a column of
34 feet nearly balances the ordinary elasticity of the air.
Therefore, when there is an issue given to it through
the pipe GHH', it will drive the compressed air along
When the upper cylinder is full of water, there bullet. This rapid congelation is a remarkable instance Pneumatis Engines. will be 34 cubic feet of water expelled from the lower of the general fact, that air by suddenly expanding, ge- Fegins
cylinder. If the pipe IN had been more than 136 feet nerates cold, its capacity for heat being increased. Thus
seven-eighths of its bulk; and a pipe leading from a And thus every thing is brought into its first condi- very large vessel inverted in it, may be used for raising tion; and when the attendant sees no more water come the water from a vessel of one eighth of its capacity 17 out at E, be shuts the cocks E and M, and opens the feet high; or if this vessel has only to of the capacity cock C, and the operation is repeated.
of the large one set in the tide way, two pipes may be led There is a very surprising appearance in the working from it, one into the small vessel and the other into an equal of this engine. When the efflux at N has stopped, if vessel 16 feet higher, which receives the water from the the cock F be opened, the water and air rush out toge- first. Thus one sixteenth of the water may be raised 34 ther with prodigious violence, and the drops of water feet, and a smaller quantity to a still greater beight; and are changed into hail or lumps of ice. It is a sight this with a kind of power that can hardly be applied in usually shown to strangers, who are desired to hold their any other way. Machines of this kind are described hats to receive the blast of air: the ice comes out with by Schottus, Sturmius, Leupold, and other old writers; such violence as frequently to pierce the hat like a pistol and they should not be forgotten, because opportunities