Water Lute—Sqfety Valves.

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Chap. 7.J

most pleasing and honorable circumstances connected with the history ofPapin’s labors, is the candid admission of several English writers of hisgreat merits, and their generously expressing regret that his attentionshould have been diverted when he was so near realizing the most splen-did reward. His name is however inseparably connected with the steam-engine, and as long as the safety-valve shall be used the World will be hisdebtor.

It should not however be supposed that safety-valves were wholly un-known before Papin’s time ; on the contrary, they were frequently used,although this fact bas not been noticed by any writer on the steam-engine. The liability of stills and retorts to be rent asunder led old che-mists to apply plugs to openings in those vessels, that the vapor mightraise or drive them out and escape ere its tension exceeded the strengthof the vessels : such were the plugs in ancient steam deities, see page 399.In some old works on distilling, conical plugs or valves are shown as fittedinto cavities on the tops of boilers, and in some cases they were loaded.In the “ Maison Rustique de Maistres Charles Estienne et Jean Liebault ,Docteurs en Medecine, ” Paris , 1574, folio 196, 197, are figures of twodose boilers in which the distilling vessels were heated : one formed awater, the other a vapor bath. On the top of each is a conical valve open-ing upwards. These served both to let out the superfluous steam and tointroduce wäter. Glauber, who contributed several valuable additions tothe mechanical department of chemistry, has figured and described, in hisTreatise on Philosophical Furnaces, the modes by which he preventedglass retorts or stills from being burst by the vapor. A long stopple orconical valve was fitted to the neck of each, being ground air-tight to itsseat, and loaded with a “ cap of lead,” so that when the steam became too“ high ” it slightly raised the valve and a portion escaped ; the valve thenclosed again of itself, “ being pressed down with the leaden cap and sostopt close.” (English Translation , Lond. 1651, p. 306.) The valve onNewcomen’s first engine was of this description. In the satte work Glau-ber describes the most philosophical of all safety-valves, viz. a column ofmercury enclosed in a bent tube which communicates with the boiler orstill, somewhat like the modern mercurial gauge. He also describes thatbeautiful modification of it known among chemists as the water lute, orquicksilver lute : that is, around the mouth or neck of a vessel a deepcavity is formed and partly filled with water or mercury, as the case maybe. A cylindrical vessel, open at top and closed at bottom, forms thecover: it is inverted, the open end being placed in the cavity and dippingas far into the liquid as the internal pressure may require. In “ The Artof Distillation, or a Treatise of the choisest Spagyrical Experiments,” &c.by John French , Doctor of Physiq, Lond. 1651, the author describes thesame devices for preventing the explosion of vessels as those mentionedby Glauber. Speafcing of the action of such safety-valves he observes,(page 7) “ upon the top of a stopple [valve] there may be fastened somelead, that if the spirit be too strong, it will only heave up the stopple andlet it fall down again.” Papin’s claim therefore is not to the valve itself,but to its improvement, or rather to the mode of applying it by means ofa lever and moveable weight; thereby not only preventing the valve frombeing blown entirely out of its place, but regulating the pressure at will,and rendering the device of universal application.

It was not tili some years after Savery had introduced his steam machinethat Papin proposed the following one, which he announced in a workentitled “ Nouvelle maniere pour lever l’eau par la force du feu, mise enlumiere, par M D. Papin, Docteur en Med. Prof, en Mathem. a Casel,