See also:

• MANOMETER (Gr. µavos, thin or loose; µerpov, a measure)

MANOMETER (Gr. µavos, thin or loose; µerpov, a measure)  , an See also:

• INSTRUMENT (Lat. instrumentum, from insincere, to build up, furnish, arrange, prepare)

instrument for measuring the pressures exerted by gases or vapours . An alternative name is pressure See also:

• GAUGE, or GAGE (Med. Lat. gauja, jaugia, Fr. jauge, perhaps connected with Fr. jale, a bowl, galon, gallon)

gauge, but this See also:

• TERM

term may conveniently be restricted to manometers used in connexion with See also:

• STEAM
• STEAM (0. Eng. steam, vapour, smoke, cf. Du. steam; the origin is unknown)

steam-boilers, &c . The principle of hydro-See also:

• STATICS (from Gr. root am-, stand, or cause to stand)

statics suggest the most See also:

• COMMON

common forms . Suppose we have a U See also:

• TUBE (Lat. tuba)

tube (fig . 1), containing a liquid: if the pressures on the surfaces of the liquid be equal, then the surfaces will be at the same height . If, on the other See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand, the pressure in one See also:

• LIMB

limb be greater than the pressure in the other, the surfaces will be at 2 Manoeuvres incidentally afford an excellent opportunity of testing new patterns of equipment, transport or other materiel under conditions approximating to those of active service . different heights. the difference being directly proportional to the difference of pressures. and inversely as the specific gravity of the liquid used . Two forms are in use: (I) the " open-tube," in which the pressure in one limb is equal to the atmospheric pressure, and (2) the' closed-tube," in which the experimental pressure is balanced against the liquid See also:

• COLUMN (Lat. columna)

column and the See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

air compressed into the upper See also:

• PART

part of a closed limb of the tube . In the " open tube " See also:

• FORM (Lat. forma)

form (fig . I) the pressure on the See also:

• SURFACE

surface a is equal to the pressure on the surface at b (one atmos1,here) plus the hydrostatic pressure exerted by the liquid column of height a b . The liquid commonly used is See also:

• MERCURY
• MERCURY (MERCU1uus)
• MERCURY (symbol Hg, atomic weight = 2oo)

mercury . If a See also:

• SCALE
• SCALE (1) A

scale be placed behind the limbs of the tube, so that the difference a b can be directly determined, then the pressure in a is at once expressible as P + a b in millimetres or inches of mercury, where P is the atmospheric pressure, known from an See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary barometric observation .

In the " closed tube " form (fig . 2) the calculation is not so See also:

• SIMPLE

simple, for the variation of pressure on the mercury surface in the closed limb has to be taken into See also:

• ACCOUNT
• ACCOUNT (through O. Fr. acont, Late Lat. comptum, cornputare, to calculate)

account . Suppose the length of the air column in the closed limb be h when the mercury is at the same height in both tubes . Applying the experimental pressure to the open end, if this be greater than atmospheric pressure the mercury column will rise and the air column diminish in the closed limb . I.et the length of the air column be h', then its pressure is h/h' atmospheres . The difference in height of the mercury columns in the two limbs is 2 (h-h'), and the pressure in the open limb is obviously equal to that of a column of mercury of length 2(h-h'), plus h/h' atmospheres . These See also:

• INSTRUMENTS

instruments are equally serviceable for deter-See also:

• MINING

mining pre. sores less than one See also:

• ATMOSPHERE (Gr. fir µ6r, vapour; orkaipa, a sphere)

atmosphere . In laboratory practice, e.g. when it is required to determine the degree of exhaust of a See also:

• WATER

water See also:

• PUMP

pump, a common form consists of a See also:

• VERTICAL (from Lat. vertex, highest point)

vertical See also:

• GLASS
• GLASS (O.E. glees, cf. Ger. Glas, perhaps derived from an old Teutonic root gla-, a variant of glo-, having the general sense of shining, cf. " glare," " glow ")
• GLASS, STAINED

glass tube having its See also:

• LOWER

lower end immersed in a See also:

• BASIN, or BASON (the older form bacin is found in many of the Romanic languages, from the Late Lat. baccinus or bacchinus, probably derived from bacca, a bowl)
• BASIN, THOMAS (1412—1491)

basin of mercury, and its upper end connected by means of an intermediate See also:

• VESSEL (O. Fr. vaissel, from a rare Lat. vascellum, dim. of vas, vase, urn)

vessel to the exhaust . The mercury rises it the tube, and the difference between the barometric height and the length of the mercury column gives the pressure attained .