The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . s inside the form of mano-meter is very conveni-ent forrough practical work, but haa no pre- « ^ ?„ . j ..^-,7 ,.tensions to seientifio ^^^ Metaihc Manometer,accuracy, as changes of temperature aflect the elasticity of the tubein a way which is diflTicult to discover and allow for. Various formsof metallic mauoraetei-s have been recently invented, the bes
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . s inside the form of mano-meter is very conveni-ent forrough practical work, but haa no pre- « ^ ?„ . j ..^-,7 ,.tensions to seientifio ^^^ Metaihc Manometer,accuracy, as changes of temperature aflect the elasticity of the tubein a way which is diflTicult to discover and allow for. Various formsof metallic mauoraetei-s have been recently invented, the best-knownof which are perhaps those of Bomdon and Schiifer, in which theindex is moved by a train of wheels actuated by the free end of theclastic tube. /Iir-pump Manometer.—Yor measuring pressures less than thntof the atniOsphere, as in the receiver of an air-pump, a special formof. mercury manometer is employed, consisting of a glass [J tubewith each leg over 30 inches long and half filled with leg communicates by an Air-tight communication with the re-ceiver of the air-pump, and tlie other is left open. As the exh^.ustionproc€eds,-jthe mercury falls iu the o|icn le^; and rises in the When only considerable degrees of exhaustion are to be measured,the instrument taka; iae form of a short U tube closed at one endand open at the other, and has its closed leg completely filled witlimercury, the mercury being heldmp by the atmospheric whole is enclosed in a wide glass tube closed at the top-ardhermetically fixed at the lower end to a brass piece, provided witha stop-cock, whereby it can be screwed on to the sole plate of the:iir-pump. The difference of level in the two legs gives the degreeof exhaustion obtained. See Ganoia Fhi/sics; y^iWhieTs Lckrbnchder E3^c7ime7italphT/sil;Amagat in Annalcs de Chemie ei de PhysiqitCy March 1880; JUportof Challenger, in regard to pressure correcfions supplied bythermometers, liy Professor Tait. ? (J.
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Keywords: ., bookauthorbaynesth, bookcentury1800, bookdecade1890, bookyear1892
