.J40 »HILOSOPHICAI. TRANSACTIONS. [anNO 1685. 



rock, forces the water to rise through those two extreme parts that are not at all 

 clogged, or covered with water. 



Observations on a French Paper, concerning a perpetual Motion. By Dr. Papin, 



F.R.S. N° 177, p- 1240. 

 The paper printed in French, and containing a contrivance for a perpetual 

 motion, being expressed in such a manner, that can hardly be understood but 

 by those who are well acquainted with such descriptions, I have endeavoured to 

 explain it as follows. 



Let DEF, fig. 16, pi. 7, be a pair of bellows, 40 inches long, which may 

 be opened by removing the part F from E: let them be exactly shut every 

 where but at the aperture E; and let a pipe E G, 20 or 22 inches long, be sol- 

 dered to the aperture E, having its other end in a vessel G, full of mercury, 

 and placed near the middle of the bellows. A is an axis for the bellows to 

 turn upon. B is a counterpoise fastened to the lower end of the bellows. C, 

 a weight with a clasp to keep the bellows upright. 



Now if we suppose the bellows opened only to -^ or -J-, standing upright as in 

 the figure, and full of mercury, it is plain that the mercury, being 40 inches 

 high, must fall, as in the Torricellian experiment, to the height of about 29 

 inches, and consequently the bellows must open towards F, and leave a vacuity 

 there : this vacuity must be filled with the mercury ascending from G, through 

 the pipe G E, the pipe being but 22 inches long : by this means the bellows 

 must be opened more and more till the mercury, continuing to ascend, makes 

 the upper part of the bellows so heavy, that the lower part must get loose from 

 the clasp C, and the bellows turn quite upside down ; but the vessel G, being 

 set in a convenient place, keeps them horizontal, as fig. 17, pi. 7> and the part 

 F engages there in another clasp C ; then the mercury by its weight runs out 

 from the bellows into the vessel G, through the pipe E G, and the bellows 

 tnust shut closer and closer, till the part EF comes to be so light, that the 

 counterpoise B is capable of freeing the part F from the clasp C ; then the bel- 

 lows come to be upright again, as fig. 16; the mercury left in them falls again 

 to the height of 29 inches, and consequently all the other effects will follow as 

 before, and the motion continue for ever. Thus much the French author. 



Upon this it is to be observed, that the bellows can never be opened by the 

 internal pressure, unless the said pressure be stronger than the external : now 

 in this case, the weight of the atmosphere freely presses on the outward part of 

 the bellows, but it cannot come at the inward part except through the pipe G E 

 which, containing 22 perpendicular inches of mercury, counterpoise so much 



