447
Chap. 7.]
There seems however to be some mistake respecting the date just men-tioned, which is the one generally assigned; for in the second volume ofBoyle’s Works (by Shaw, Lon. 1725) are details of experiments on boilingbeef &c. “ in screw’d vessels or digestors,” in the beginning of the year1679 —thus : “ January 29. Eight days ago I fill’d a screw’d vessel withbeef and water together, and when it had continued over a moderate firefor 8 or 9 hours in balneo marice [a water bath] stopp’d also with a screw,I took the flesh out,” &c. “ Feb. 10. I boil’d a cow heel after the same
rnanner as I had done the flesh above mention’d, but left it for four hoursor more upon a moderate fire ; then the vessels being unstopp’d, we foundthe flesh exceedingly well boiled, and the bones so soft that they might beeasily cut with a knife and eaten.” “ Feb. 12. I repeated the experimentand let the vessel remain exposed to the fire for 12 hours,” &c. - - - - -“ Henee it appears that many bones and hard tendons, which we dailythrow away as unprofitable, may, by the help of a balneo marice stopp’dwith a screw, be converted into good nourishment.” pp. 550, 551.
Papin’s first digesters were as liable to be rent asunder as eolipilesplaced on a fire with their orifices stopped. They are figured in detail inPoliniere’s Experiences de Physique, 2d ed. Paris 1718. Each consistedof a short but very thick tube, of bell-metal, about a foot in lenglh andfive inches in diameter, with one end closed. The open end had a collarcast on it, to which the cap or cover was secured.by clamps and a screw.The cover and end of the tube were ground together so as to fit air-tight,like a valve to its seat. A few bones and a little water were put in, andthe cover screwed down ; the vessel was then laid in a horizontal positionon a bed of charcoal in a long iron grate. The almost unavoidable rup-ture of these vessels, led Papin to the invention of the lever safety-valve,which he first applied to them, and afterwards to machines for raisingwater by steam.
Notwithstanding the practical knowledge of the properties of steamacquired by the employment of digesters, Papin does not appear to havehad any idea of using it as a mechanical agent tili some years after. Hisfirst paper on the subject of raising water is dated July, 1685, (Phil. Trans,vol. xv, page 1093; Abridgment, vol. i, page 539) entitled “ A New Wayof Raising Water, enigmatically proposed.” Three different Solutionswere sent in, after which he explained. The device was a small fountain,in which the liquid was raised by a piston bellows “ put in some secretplace, where a body may play the same.” The application of the devicewas then pointed out, viz. to draw water from mines, by means of a run-ning stream located “ far distant ” from them : in other words, to transmitpower to a considerable distance by means of air.
His plan was this : a series of air-tight receivers were to be placed, 12feet above each other, in the shaft; the highest on a level with the ground,and the lowest 12 feet above the bottom of the pit. The water was to betransferred by the pressure of the atmosphere from one receiver to ano-ther, tili it was discharged above. For this purpose a pipe extended fromthe water to the bottom of the lowest vessel; another pipe from the lowerpart of this to the next one, and so on to the top ; and to prevent the waterfrom running back, the upper orifice of each pipe was covered by a valve.4 he mode by which he alternately withdrew air from and admitted itintothe receivers, constitutes the main feature of the plan. The upper partsof every two receivers were connected by branch pipes to a long one at-tached to the bottom of a separate air-pump, which was to be placed near awater-wheel impelled by the current; and the piston was to be worked bya crank formed on the shaft of the wheel. The Operation of two pumps