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tube bent as reprefented, and with a bulbblown in that part of the tube that lies be-tween the upper and lower flexure. It hasalfo a {mail funnel at the top, which, however,is not very eflential. This tube is fometimesemployed as a ftopper to the tubuiure of theretort, or to a feparate opening in the receiver,and fometimes, as at/Fig. 59,it is cemented,by melting, into the tube patting from thereceiver to the firft bottle. Before ufmg it, alittle mercury is dropped down through thefunnel, about fufficient to occupy the fpace ofthe tube that lies between the two lower flex-tires, which completely flints up the accefs ofthe external air whillt the diftillation is goingon. But as foon as any vacuum is formed inthe veflel to which it is attached, the mercuryis forced up by the prefiure of the atmofphereInto the bulb, and not being in fufficient quan-tity to fill it, the external air paffes by it in thisplace, and rufties into the apparatus. Thisvery ingenious contrivance unites every conve-nience, for it fupplies air to the vacuum pre-cifely in the place where abforption begins, andin fa£t it renders ufelefs all other contrivance toprevent abforption in any diflant part of theapparatus. The only objection to the Welter’stube is its great fragility, more efpecially whenconnected with a conducing tube as in Fig. 59,which when firmly ftoppered or luted in itsplace is liable to fnap with the leaft fhake, andbefidcs a great many are broken in the makingand grinding even by fkilful artifts. The otherparts of Fig. 59 are obvious by mere infpection.a is an iron ftand generally furnifhed with threeAiding rings of different diameter, one of whichis here reprefented ; b is a fmall Argand lamp,very convenient for chemical purpofes, beingflat and low; c is a tubulated retort; d, a tubu-lated receiver, Handing on a convenient woodentripod e \ f is the conducing tube with theWelter’s tube affixed to it. The receiver d isleft empty in the beginning of the diftillation,and the vapour which does not condenfe therepaffes through f into the bottle g, and throughh into the bottle u To make the apparatuscomplete for experiments of refearch, a benttube may be fattened in the lateral opening of i,condu&ing to a pneumatic trough.

Fig. .57 is a fmall apparatus nearly fimilar toone that has been lately fuggefted, of a feries.ofWoulfe bottles without luting, in which thefeveral parts have confiderable play, fo as toavoid any ftrefs on the thin brittle tubes ofwhich it is compofed. Only a fingle fpeci-.men of the principle, aCted, on is here introduced^

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which is in the veflel d. a is a matrafs Handingon one of the rings of an iron ftand ; b is abent tube, one leg of which is cemented irto thecork of a, the -other paffes down into tl e fhcrt-jar d, through a much wider glafs -tube c. Thelower end of b fhould be a little curved, fothat any bubble of gas palling out of it mayclear the edge of the tube c and pafs up intothe jar d, and both b and c dip a little waybelow the level of the liquor in d. The gasthen paffes out through e into the bottle f andfo on, which may alfo be furnifhed with a widetube fimilar to r, -through which the lower partof e may pafs. In all the common Woulfe’sapparatus there is a perpetual rifk of breakingthe thin conducting tubes from the circurn-ftance of having both of their lower extremitiestightly fattened down either by lutes or bygrinding, which gives a great ftrefs to themiddle of the tube unlefs the bottles remainperfectly upright, and exactly at the properdiftance from each other. Whereas in thisapparatus only one end of the conducting tubeis fixed, and the other moves at eafe within thelarger tube that ferves as its cafe, and any partof it may be inftantly withdrawn and put onagain without deranging the reft. The largertube in this cafe alfo ferves to prevent abforp-tion as the tube e in Fig. 58.

Thus, for example, if it is wifhed to makeliquid oxymuriatic acid by this apparatus, putthe manganefe and other materials in the ma-trafs a, and a fmall quantity of water in d andfill / two-thirds full. The oxymuriatic gaspaffes along b into the fmall jar d where thecommon muriatic acid which it contains is de-tained by the fmall quantity of water in d, andthe reft of the gas iffues out through e, andgoes to impregnate the water in f. If thematerials in the matrafs a are not fufficient, itmay he drawn away by lifting out the tube b, andthe veflel returned to its place without movingany other part of the apparatus. It fliould beobferved, that wherever there is an open tubecommunicating with the bottles as at c, thegreater prefiure produced in the veffel by theinflux of gas, and the refiftance of the water intowhich the conducting tube t immerges, willcaufe the liquor in d to rife in the open tube r,and it will overflow, unlefs care is taken to pro-portion the height of the open tube to the pref-iure which it is to counteract.

Another variety of Woulfe’s apparatus isgiven in PI. HI. Fig. 42. in which the abtorp--tion is prevented by a glafs valve inftead of atube of fafety. The conitruCUon of this valve