THE CISTERN BAROMETER

BAROMETER. [A, 876.] eter devised by Regnault for measuring gaseous pre ures of le than one atmosphere. It consists of a cistern b. into the reservoir of which two tubes dip, one closed at the top, the other communicating with a ve el containing the gas under observation. The difference in the height of the ey in the two tubes, measured with a cathetometer, indicates the difference between the tension of the gas and the atmospheric pre ure, [B.|—Dosenb’ (Ger.). See Aneroid b.—Fahrenheit’s b. A form of b. in which the height FAHRENHEIT'S BAROMETER. [A, 376.] ‘The top of the tube. [A, 876.] of the barometric column is reduced by the device of employ in; number of alternate columns of mercury and of water or any ot FORTIN’S BAROMETER. liquid, usually colored. A gla tube with bulbous expansions at regular intervals is bent several times upon itself. The lower bulbs contain mercury, and the upper bulbs the other liquid. The atmospheric pre ure is balanced by:the sum of the differences of level of the columns of mercury, minus the sum of the corresponding differences for the columns of the other liquid. The instrument is not sensitive enough for ordinary use, but a similar device is used for measuring very high pre ures. [A, 376.]—Federb? (Ger.). See A nevoid b.—Flaschenb’ (Ger.). See Cistern b.—Fortin’s b. A form of the cistern b. constructed with a view to portability and facility of accurate reading. e bottom of the reservoir is made of leather, and can be raised or lowered by means of a screw, so that the mercury in it can always be brought to a constant ievel, or, when the instrument is not in use, can be made to fill the reservoir completely, thus preventing the admi ion of air and the danger of breaking the instrument by a sudden movement of the ma of mercury, The column of mercury bears a cylindrical float furnished with a vernier. [A, 376; B.]|—Gay-Lu ac’s b. See “siphon b._Gefii b’ (Ger.)., See Cistern b.— ‘eberb’ (Ger.). See Siphon b.—Kapselb’ (Ger.). See Cistern b.—Mercurial b. Ger. Quecksilberb’. Ab. in which a column of mercury is sustained by atmospheric pre ure, as distinguished from a. metallic b. and from one in which another liquid than mereury is used. [B.]—Metal lie b. See Aneroid b. and Bourdon’s metallic b.—Morland’s b. See Counterpoised b.—Quecksilberb’ (Ger.). See Mercurial b.—Radb’ (Ger.). See Wheel b.—Registering b. Fr, baromètre enregistreur. Ger.,reg is tri ren des THE SIPHON BAROME- B. See BAROGRAPH and Counterpoised b— TER. [A, 376.) Reiseb’ (Ger.). A portable b. [B,49.] See Fortin’sb.—Siphon b. Fr., baromètre à siphon. Ger., Heberb’. It., barometro a sifone. Sp, barômetro de sif on. A modification of the cistern b. in which the reservoir is replaced by the shorter of the two arms of a U-shaped tube containing dut In Gay-Lu ac's siphon b. the two arms of the U are connected by a capillary tube. The difference in height of the columns in the two arms indicates THE WHEEL BAROMETER. [B.]-Thermo-b; See Boiling-point rimitive form of the cistern b., consist led with mercury and inverted into an [B.J=Wageb* Ger). See Ger., Wa erb’. A cistern b. con the atmospheric pie b.—Torr i cell i’s b. The ing only of a gla tube open ve el also containing mercury. ‘ounterpoised b.—Water b. taining water instead of mercury. Such b's must be at least 33 feet long. [B.]—Wheel b. Fr., baromètre à cadran. Ger., Radb’. A form of the siphon b. invented by Hooke in 1683, in which a float placed in the short arm of the tube rises and falls with the mercury, and turns a needle pivoted at the centre of a dial. [A,376; B.] BAROMETRE (er, n. Baër-o-me?tr. 1. A-barometer. [B. 2 A provincial name for the Carlin a a caulis. [B, 121.]—B. cadran. See Wheel BAROMETER.—B. à cuvette. See Cistern BAROMETER. —B. à siplion, B. de Gay-Lu ac. See Siphon BAROMETER.—B. de Regnault. See Diffcrential BAROMETER. BAROMETRIC, BAROMETRICAL, cat he Ba?r-o-me?t’- ritk, -ri°k-a?l. Lat., barometric us. Fr, barométrique. Ger., barometrisch. It, barometrico. Sp., barométrico. Pertaining to a barometer, to barometry, or to atmospheric pre ure: BAROMETROGRAPH, bn. Ba*r-o-me*t/ro-gra%f. Lat.. barometrographium (from Bépos, weight, nézpov, a measure, and yodbeur, h. to write). Fr., barométrographe. Ger., Barometrograp! see BAROGRAPH.