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THE POPULAR SCIENCE MONTHLY.
nearly to its extreme upper position. The air in contact with the water-jacket becoming cooled contracts, and the pressure is reduced below the power-piston, which then descends by the force of the atmosphere. As it reaches the end of its downward stroke and begins
Fig. 10.
to ascend, the plunger comes down and the operation is repeated. When the air passes from the heater to the cool cylinder A, it heats the plates of the regenerator and this heat is given off to the cool air, when it is again forced into the heater. The utmost of the heat is thus utilized that is possible. The start in this as in all hot-air and gas
