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Papin’s Experiments on Steam. [Book IV.

duce a vacuum. His apparatus consisted of a small cylinder, in which apiston like that of a common pump-sucker (viz. with an aperture coveredby a valve) was fitted to move. The bottom of the cylinder was closed,and when the piston was near the top he exploded a small charge ofpowder below it, with the hope that the sudden blast of flame would expelall the air through the valve, which instantly closing would prevent itsreturn. A vacuum being thus formed, the pressure of the atmospherewould be excited and might be used as a source of power. He couldnot however succeed in driving out all the air by the explosion, andthe pressure on the piston, (ascertained by attaching weights to a ropepassed over a pulley and connected to the piston rod) instead of being13 or 14 pounds on the square inch, seldom exceeded six or seven. Hepublished an account of these experiments the following year in the ActaEruäitorum, a journal published at Leipsic, and which was toGermany whatthe Journal des Savans was to France and the Philosophical Transactions to England. It was commenced in 1682, and both the latter in 1665.

In 1690, Papin, unable to obtain a sufficient vacuum with gunpowder,turned his attention to steam. In one of his first essavs he raised thepiston by its expansive force; and then allowing it time to cool and returnto its former bulk as.a liquid, the pressure of the air forced the piston back.His cylinder was inches diameter, and closed at the bottom. A smallquantity of water was introduced through a hole in the piston, which waspushed down to exclude the air below it, and the hole then stopped by aplugt A brasier of burning coals was now applied to the bottom of thecylinder, and the piston consequently raised by the accumulating vapor.When the piston reached nearly to the top of the cylinder, it was retainedthere by a latch slipped into a noteh in the piston rod : the fire was nowremoved, and the steam quickly Condensed by the lower temperature ofthe surrounding air: the latch was removed, and the atmosphere pressedthe piston down and raised a load of 60 pounds, which was attached by arope and pulley to the piston rod, being an effective force of 12J poundsupon every square inch on the upper surface of the piston.® A device ofthis kind Papin thought was applicable to draw water from mines, and torow boats against wind and tide.

it d oes not appear that Papin made any essential improvement on theapparatus during the four following years; for when he published his“ Recueil des diverse Pieces touchant quelques Nouvelles Machines, etautres Sujets Philosophiques, par M. D. Papin, Dr.en Med. ACasel, 1695,”he still contemplated generating the steam in the cylinders; and at everystroke these were either moved from the fire, or the fire from them. It isastonishing that the idea of a fixed and separate boiler did not occur to him.His plan was never tried except as an experiment; and he subsequentlyabandoned the use of cylinders and pistons, and applied steam to raisewater on the plan of Worcester ’s 6Sth proposition. This was unfortunatefor his fame ; for in his experiments with the piston and cylinder he wasin possession of every principle of the low-pressure steam-engine, and hadhe followed up the device he would have borne off the palm from all hiscontemporaries. Even the high-pressure engine, and all the glory of itsdevelopment, was then within his reach; but he was no practical me-chanic, and his thoughts became diverted into other channels. One of the

a It is impossible to contemplate the various attempts of Papin to move a piston byatmospheric pressure, without notieing the analogy between his contrivances and thatofGuerricke, and without thinking that the apparatus of this philosopher was presentto his mind.