Leopold’.i Engine.

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Chap. 9.]

Leopold, to whom we have frequently referred, reflecting on Papin’sexperiments, suggested the following application of steam to move pistonsand to raise water:—

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No. 197. Leopold’s High Pressure Engine. A. D. 1720.

Two steam cylinders, open at top and provided with pistons a b, wereplaced over the boiler c, from the upper part of which a four-way cock dadmitted steam alternately into the bottom of each. The pistons wereconnected by inflexible rods to the ends of two working beams, and to theopposite extremities of the beams were connected, by similar rods, thepistons f g of two forcing pumps, whose lower parts were placed m thewater to be raised. An attendant turned the plug of the cock to admitsteam under one piston, which was pushed up by the expansive force ofthe fluid, and consequently the piston of the pump connected to the samebeam was forced down, and the water in its chamber driven up the risingmain i. The cock was then turned to admit steam into the other cylinder,whose piston was raised in like manner; at the same time one passage ofthe cock opened a communication with the interior of the first cylinderand the external air, so as to allow the steam within to escape.—(See thefigure.)

This is the first high-pressure piston engine figured in books. It has beengreatly admired, and yet as represented it is useless and impracticable ;for when the steam pistons were once raised the whole would remain im-moveable, there being no means for causing them to descend. Had Leo-pold used one beam instead of two, and placed a pump and steam cylinderunder each end, the device would have been complete and very effective.

It is singulär that the researches of Leopold had not made him ac-quainted with the fact that four-way cocks were used long before Papin,to whom he attributes them.

With this device of Leopold, we take leave of steam machines. Hithertothey had been employed only to raise water, but the period was now ap-proaching when the agency of this fluid as a first mover of machinery ingeneral, was to become indefinitely extended. The engines of Newcomen