See also:

• PUMICE (Lat. purnex, spumex, spuma, froth)

PUMICE (See also:

• LAT

Lat. purnex, spumex, spuma, froth)  , a very porous, froth-like, volcanic 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 . It is an igneous See also:

• ROCK
• ROCK (O.Fr. rake, Sp. rota, Ital. rocca; possibly from a Lat. form rupica, from rupes, rock)
• ROCK, DANIEL (1799–187t)

rock which was almost completely liquid at the moment of effusion and was so rapidly cooled that there was no See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time for it to crystallize . When it solidified the vapours dissolved in it were suddenly released and the whole See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass swelled up into a froth which immediately consolidated . Had it cooled under more pressure it would have formed a solid glass or See also:

• OBSIDIAN

obsidian (q.v.); in fact if we take fragments of obsidian and See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat them in a crucible till they fuse they will suddenly See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change to See also:

• PUMICE (Lat. purnex, spumex, spuma, froth)

pumice when their dissolved gases are set See also:

• FREE

free . Hence it can be understood that pumice is found only in See also:

• RECENT

recent volcanic countries . Artificial substances resembling pumice can be produced by blowing See also:

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

steam through molten glass or slag, and when a mass of slag is suddenly cooled by being tipped into the See also:

• SEA (in O. Eng. sae, a common Teutonic word; cf. Ger. See, Dutch Zee, &c.; the ultimate source is uncertain)
• SEA, COMMAND OF THE

sea (as is the See also:

• CASE
• CASE, JOHN (d. 1600)

case at the blast furnaces of See also:

• WHITEHAVEN

Whitehaven in See also:

• CUMBERLAND
• CUMBERLAND, DUKES AND EARLS OF
• CUMBERLAND, RICHARD (1632-1718)
• CUMBERLAND, RICHARD (1732-1811)
• CUMBERLAND, WILLIAM AUGUSTUS

Cumberland) it swells up into a pumiceous See also:

• FORM (Lat. forma)

form so See also:

• LIGHT

light and full of vesicles that it will See also:

• FLOAT (in O. Eng. floc and flota, in the verbal form f eotan; the Teutonic root is flut-, another form of flu-, seen in " flow," cf. " fleet "; the root is seen in Gr. a-M e, to sail, Lat. pluere, to rain; the Lat, fluere and fluctus, wave, is not connect

float on See also:

• WATER

water . Any type of See also:

• LAVA

lava, if the conditions are favourable, may assume the pumiceous See also:

• STATE
• STATE, GREAT OFFICERS OF

state; but basalts and andesites removing the See also:

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

air or other See also:

• GAS

gas from a See also:

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

vessel, whilst a See also:

• COMPRESSION

compression See also:

• PUMP

pump compresses the air . The simplest forms of pumps employed for forcing liquids are " plunger pumps," consisting essentially of a See also:

• PISTON (through Fr. from Ital. pistone or pestone, a great pestle, from Late Lat. pistare, to pound, a frequentative form of classical Lat. pinsere)

piston moving in a See also:

• CYLINDER (Gr. KvAwSpos, from KvXivaety, to roll)

cylinder, provided with inlet and outlet pipes, together with certain valves . The disposition of these valves divides this type of pump into suction pumps and force pumps . Fig . I shows the arrangement in a suction pump . A is the cylinder within which the piston B is moved up and down by the See also:

• ROD (O.E. rodd, probably related to Norw. rudda, stick, rodda, stake)
• ROD, EDOUARD (1857-1910)

rod C .

D is the inlet See also:

• PIPE

pipe (the See also:

• LOWER

lower extremity of which J C is placed beneath the See also:

• SURFACE

surface of the liquid to be G removed), and G is the outlet pipe . E is a See also:

• VALVE (Lat. valva, a leaf of a double or folding door, allied to volvere, to roll, as of a door on its hinges)

valve A in the inlet pipe opening into the cylinder ; and the piston is perforated by one or more holes, F each fitted with valves opening outwards on its B upper surface . On raising the piston, the valve "~//////A F remains closed and a vacuum tends to be ~~ created in the cylinder, but the pressure of the See also:

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

atmosphere forces the liquid up the See also:

• TUBE (Lat. tuba)

tube D and it raises the valve E and passes into the cylinder . On See also:

• REVERSING

reversing the See also:

• MOTION (Lat. motio, from movere, to move)
• MOTION, LAWS OF

motion the valve E closes and the liquid is forced through the valve F to the upper See also:

• PART

part of the cylinder . On again D raising the piston, more liquid enters the lower part of the cylinder, whilst the previously raised FIG . I. liquid is ejected from the delivery pipe . Obviously the See also:

• ACTION

action is intermittent . Moreover, the height of the lift is conditioned by the atmospheric pressure, for this is the See also:

• DRIVING (from " to drive," i.e. generally to propel, force along or in, a word common in various forms to the Teutonic languages)

driving force; and since this equals 34 ft. of water, the lift cannot be theoretically more than this distance when water is being pumped . In practice it may be considerably less, owing to leakage at the valves and between the piston and cylinder . In the force pump (fig . 2) there is no such See also:

• LIMITATION, STATUTES OF

limitation to the lift . In this case the piston is solid, and the outlet pipe, G which is placed at the bottom of the cylinder, has a valve F opening outwards, the inlet pipe and valve are the same as before .

On raising the piston the liquid rises in the cylinder, the H valve E opening and F remaining shut . On reversing the motion the valve E closes and the liquid is driven past the valve F . On again raising the piston the valve E opens admitting more liquid whilst F re-mains closed . It is seen that the action is intermittent, liquid only being discharged during a down stroke, but since the driving force is that which is supplied to the See also:

• CON

con-FIG . 2. piston rod, the lift is only con- ditioned by the See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power available and by the strength of the pump . A continuous See also:

• SUPPLY (through Fr. from Lat. supplere, to fill up)

supply can be obtained by leading the delivery pipe into the See also:

• BASE

base of an air chamber H, which is fitted with a See also:

• DISCHARGE (adapted from the O. Fr. discharge, modern decharge, from a med. Lat. discargare, to unload, dis- and earn care, to load, cf. " charge ")

discharge pipe J of such a See also:

• DIAMETER (from the Cr. &a, through, µErpov, measure)

diameter that the liquid cannot See also:

• ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

escape from it as fast as it is pumped in during a down stroke . The air inside is compressed in consequence and during an upstroke of the piston this air tends to regain its See also:

• ORIGINAL

original See also:

• VOLUME

volume and so expels the water, thus bringing about a continuous supply . For a' description of See also:

• MODERN

modern pumps, see See also:

• HYDRAULICS (Gr. iS&,p, water, and ai,Xos, a pipe)

HYDRAULICS . Air-pumps.—Pumps for evacuating vessels may be divided into three classes: (I) See also:

• MECHANICAL

mechanical, (2) See also:

• MERCURIAL

mercurial, and (3) See also:

• JET (Fr. jais, Ger. Gagat)

jet Mechanical.pumps; the last named are treated in HYDRAULICS . The invention of the mechanical air-pump is generally attributed to See also:

• OTTO

Otto von See also:

• GUERICKE, HEINRICH ERNST FERDINAND (1803-1878)
• GUERICKE, OTTO VON (1602-1686)

Guericke, See also:

• CONSUL
• CONSUL (in Gr. generally ihraros,ashortened form of errpavgybs 8hraeos, i.e. praetor maximus)

consul of See also:

• MAGDEBURG

Magdeburg, who exhibited his See also:

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

instrument in 1654; it was first described in 1657 by Gaspar Schott, See also:

• PROFESSOR (the Latin noun formed from the verb profiteri, to declare publicly, to acknowledge, profess)

professor of See also:

• MATHEMATICS (Gr. /saBnµar1Kil, Sc. vOcvn or E7rlQTt'µn; from p iN.La, "learning" or "science ")

mathematics at See also:

• WURTTEMBERG

Wurttemberg, in his Mechanica hydraulico-pneumatica, and afterwards (in 1672) by Guericke in his Experimenta nova Magdeburgica de vacus spatia . It consisted of a spherical glass vessel opening below by means of a stop-See also:

• COCK, EDWARD (1805-1892)

cock and narrow nozzle into the cylinder of an " exhausting See also:

• SYRINGE (Gr. ovpryE, reed, pipe)

syringe," which inclined upwards from the extremity of the nozzle . The cylinder, in which a well-fitting piston worked, was provided at its lower end with two valves .

One of these opened from the nozzle into the cylinder, the other from the cylinder into the outside air . During the down-stroke of the piston the former was pressed See also:

• HOME
• HOME, DANIEL DUNGLAS (1833-1886)
• HOME, EARLS OF

home, so that no air entered the nozzle and vessel, while the latter was forced open by the air which so escaped from the cylinder . During the return- stroke the latter was kept closed in virtue of the partial vacuum formed within the cylinder, while at the same time the former was forced open by the pressure of the denser air in the vessel and nozzle . Thus, at every See also:

• COMPLETE

complete stroke of the piston, the air in the vessel or See also:

• RECEIVER

receiver was diminished by that fraction of itself which is expressed by the ratio of the volume of the avail-able cylindrical space above the outward opening valve to the whole volume of receiver, nozzle and cylinder . The action is essentially that of the See also:

• COMMON

common suction pump . The construction was subsequently improved by many experimenters, notably by See also:

• BOYLE
• BOYLE, JOHN J
• BOYLE, ROBERT (1627-1691)

Boyle, Hawksbee, See also:

• SMEATON, JOHN (1724–1792)

Smeaton and others; and more recently two pump barrels were employed, so obtaining the same degree of exhaustion much more rapidly . This type of pump is, however, not very efficient, for there is not only leakage about the valves and between the piston and cylinder, but at a certain degree of exhaust the air within the vessel is insufficient to raise the inlet valve; this last defect has been met in some measure by using an See also:

• EXTENSION (Lat. ex, out ; tendere, to stretch)

extension of the piston to open and See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

close the valve . The so-called oil air-pumps are much more efficient; the valve difficulty is avoided, and the See also:

• RISK

risk of leakage minimized; whilst in addition there is no air clearance between the piston and the base of the cylinder as in the older mechanical forms . The Fleuss pump may be taken as an example . The piston, provided with a valve opening upwards, is packed in the cylinder by a See also:

• LEATHER (a word which appears in all Teutonic languages; cf. Ger. Leder, Dutch leer or leder, Swed. leder, and in such Celtic forms as Welsh llader)
• LEATHER, ARTIFICIAL

leather See also:

• CUP (in O.E. cuppe; generally taken to be from Late Lat. cuppa, a variant of Lat. cupa, a cask, cf. Gr. KuaeXXov)

cup which is securely pressed against the sides of the cylinder by the atmospheric pressure . The piston rod passes through a valve in the upper part of the cylinder which is held to its seat by a See also:

• SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

spring . The inlet pipe enters an elliptical vessel which communicates with the cylinder a little way up from its base, whilst at the base there is a See also:

• RELIEF

relief tube leading into the elliptical vessel already mentioned .

Oil is placed both above the upper valve seating, and also in the cylinder up to the height of the lower edge of the inlet pipe . The action is as follows: On raising the piston it cuts off communication with the inlet pipe and then compresses the air above, forcing it through the upper valve and oil into the atmosphere . Some of the oil is also driven out, but as the valve does not close until the piston has descended a See also:

• SHORT, FRANCIS JOB (1857– )

short distance, a certain amount of oil returns . On lowering the piston its valve opens and air passes in from the vessel to be exhausted; this is further rarefied on the next stroke and so on . The Max See also:

• KOHL

Kohl pumps are based on the same principle, but are constructed with more elaborate detail, leading to a greater efficiency, an exhaust of o•0008 mm. being claimed as readily obtainable . The invention of the See also:

• BAROMETER (from Gr. (3apoc, pressure, and µETpov, measure)

barometer and See also:

• TORRICELLI, EVANGELISTA (1608—1647)

Torricelli's explanation of the vacuity above the See also:

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

mercury See also:

• COLUMN (Lat. columna)

column placed before the members of the Florentine See also:

• ACADEMY, GREEK
• ACADEMY, ROYAL

academy a ready method Mer,cudar of obtaining vacua; for to exhaust a vessel it was only necessary to join, by means of a tube provided with stop-cocks, the vessel to a barometer tube, fill the See also:

• COMPOUND
• COMPOUND (from Lat. componere, to combine or put together)

compound vessel with mercury and then to invert it 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 containing this liquid, whereupon the mercury column See also:

• FELL
• FELL, JOHN (1625-1686)

fell, leaving a Torricellian vacuum in the vessel, which could be removed after shutting off the stop-cocks . This was the only method known until the invention of the mechanical air-pumps; it was subsequently employed by See also:

• COUNT (Lat. comes, gen. comitis, Fr. comte, Ital. conte, Span. conde)

Count See also:

• RUMFORD, BENJAMIN THOMPSON, COUNT (1753-1814)

Rumford, and as See also:

• LATE

late as 1845, See also:

• EDWARD

Edward A . See also:

• KING
• KING (O. Eng. cyning, abbreviated into cyng, cing; cf. O. H. G. chun- kuning, chun- kunig, M.H.G. kiinic, kiinec, kiinc, Mod. Ger. Konig, O. Norse konungr, kongr, Swed. konung, kung)
• KING [OF OCKHAM], PETER KING, 1ST BARON (1669-1734)
• KING, CHARLES WILLIAM (1818-1888)
• KING, CLARENCE (1842–1901)
• KING, EDWARD (1612–1637)
• KING, EDWARD (1829–1910)
• KING, HENRY (1591-1669)
• KING, RUFUS (1755–1827)
• KING, THOMAS (1730–1805)
• KING, WILLIAM (1650-1729)
• KING, WILLIAM (1663–1712)

King patented filament electric lamps exhausted by the same methods . Although modern mercurial pumps have assumed a multiplicity of forms, their actions can be reduced to two principles, one statical, the other hydrodynamical—at the same time See also:

• INSTRUMENTS

instruments have been devised utilizing both these principles . Statical Pumps.—The earliest mercurial pump, devised by See also:

• SWEDENBORG (or SWEDBERG), EMANUEL (1688-1772)

Swedenborg and described in his Miscellanea observata circa res naturales (1722), was statical in action, consisting essentially in replacing the solid piston of the mechanical pump by a column of mercury, which by being alternately raised and lowered gradually exhausted a vessel . A more complicated pump, but of much the same principle, was devised in 1784 by See also:

• JOSEPH
• JOSEPH, COMTE DE (1785-1870)
• JOSEPH, FATHER (FRANCOIS LECLERC DU TREMBLAY) (1577-1638)

Joseph See also:

• BAADER, FRANZ XAVER VON (1765–1841)

Baader, to be improved by C . F .

Hindenburg in 1787, by A . N . Edelcrantz in 1804 and by J . H . See also:

• PATTEN (adapted from Fr. patin, in modern usage meaning a " skate "; Med. Lat. patinus, Ital. pattino, of unknown origin; cf. patte, paw)

Patten in 1824; whilst in 188r See also:

• RANKINE, WILLIAM JOHN MACQUORN (182o-1872)

Rankine See also:

• KENNEDY
• KENNEDY, BENJAMIN HALL (1804-1889)
• KENNEDY, THOMAS FRANCIS (1788-1879)
• KENNEDY, WALTER (c. 1460–c. 1508)

Kennedy resuscitated the See also:

• IDEA (Gr. Ibia, connected with i&eiv, to see; cf. Lat. species from specere, to look at)

idea for the purpose of exhausting filament electric lamps . The pump devised by A H . See also:

• GEISSLER, HEINRICH (1814-1879)

Geissler of See also:

• BONN

Bonn, and first described in 1858 by W . H . Theo . See also:

• MEYER, CHRISTIAN ERICH HERMANN VON (18or-1869)
• MEYER, HEINRICH AUGUST WILHELM (1800-1873)
• MEYER, JULIUS LOTHAR (183o-1895)
• MEYER, KONRAD FERDINAND (1825-1898)
• MEYER, VICTOR (1848-1897)
• MEYER, [MARIE] PAUL HYACINTHE (184o- )

Meyer in a pamphlet Ueber das geschichtele electrische Licht surpassed all previous forms in both simplicity and efficiency . The See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general See also:

• SCHEME (Lat. schema, Gr. oxfjya, figure, form, from the root axe, seen in exeiv, to have, hold, to be of such shape, form, &c.)

scheme of Geisler's pump is shown in fig . 3 .

A and B are See also:

• PEAR (Pyrus communis)

pear-shaped glass vessels connected by a See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long narrow See also:

• INDIA
• INDIA, FRENCH

india-See also:

• RUBBER, INDIARUBBER

rubber tube, which must be sufficiently strong" in the See also:

• BODY

body (or strengthened by a See also:

• LINEN

linen coating) to stand an outward pressure of 1 to 11 atmospheres . A terminates below in a narrow See also:

• VERTICAL (from Lat. vertex, highest point)

vertical tube c which is a few inches longer than the height of the barometer, and to the lower end of this tube the india-rubber tube is attached which connects A with B . At the upper end of A is a glass two-way stop-cock, by turning which the vessel A can either be made to communicate with the vessel to be exhausted, or with the atmosphere, or can be shut off from both when the cock holds an inter-mediate position . The apparatus, after having been carefully cleaned and dried, is charged with pure and dry mercury which must next be worked backwards and for-wards between A and B to remove all the air-bells . The air is then driven out of A by and letting the mercury flow into A until it gets to the other See also:

• SIDE
• SIDE (mod. Eski Adalia)

side of the stop-cock, which is then placed in the intermediate position . Supposing the vessel to be exhausted to have already been securely connected to the pump, we now lower the See also:

• RESERVOIR

reservoir B so as to reduce the pressure in A sufficiently below the tension in the gas to be sucked in, and, by turning the cock so as to connect A with the vessels to be exhausted, cause the gas to expand into and almost fill A . The cock is now shut against both communications, the reservoir lifted, the gas contents of A discharged and so on, until, when after an exhaustion mercury is let into A, the See also:

• METAL
• METAL (through Fr. from Lat. metallum, mine, quarry, adapted from Gr. µATaXAov, in the same sense, probably connected with ,ueraAAdv, to search after, explore, µeTa, after, aAAos, other)

metal strikes against the See also:

• TOP (cf. Dan. top, Ger. Topf, also meaning pot)

top without inter-position of a gas-See also:

• BELL
• BELL, ALEXANDER MELVILLE (1819—1905)
• BELL, ANDREW (1753—1832)
• BELL, GEORGE JOSEPH (1770-1843)
• BELL, HENRY (1767-1830)
• BELL, HENRY GLASSFORD (1803-1874)
• BELL, JACOB (1810-1859)
• BELL, JOHN (1691-178o)
• BELL, JOHN (1763-1820)
• BELL, JOHN (1797-1869)
• BELL, ROBERT (1800-1867)
• BELL, SIR CHARLES (1774—1842)

bell . In a well-made apparatus the pressure in the exhausted vessel is now reduced to 1'a or $ of a milli-See also:

• METRE ((terpuc?, sc. rFxvf, from Gr. Or poi', measure)

metre, or even less . An See also:

• ABSOLUTE (Lat. absolvere, to loose, set free)

absolute vacuum cannot be produced on See also:

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

account of the unavoidable air-film between the mercury and the walls of the apparatus . As it takes a height of about 30 in. of mercury to See also:

• BALANCE (derived through the Fr. from the Late Lat. bilantia, an apparatus for weighing, from bi, two, and lanx, a dish or scale)

balance the pressure of the atmosphere, a Geisler pump necessarily is a somewhat long-legged and unwieldy instrument ; in addition, the long tube is liable to breakage . It can be considerably shortened, the two vessels A and B brought more closely together, and the somewhat objectionable india-rubber tube be dispensed with, if we connect the air-space in B with an See also:

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

ordinary air pump, and by means of it do the greater part of the sucking and the whole of the lifting See also:

• WORK

work . An instrument thus modified was constructed by See also:

• POGGENDORFF, JOHANN CHRISTIAN (1796-1877)

Poggendorff in 1865 .

Even a Geisler's stop-cock requires to be lubricated to be absolutely gas-tight, and this occasionally proves a See also:

• NUISANCE (through Fr. noisance, nuisance, from Lat. nocere, to hurt)

nuisance . Hence a number of attempts have been made to do without stop-cocks altogether . In the pump generally attributed to Topler, but which was previously devised by J . Mile of See also:

• WARSAW
• WARSAW (Polish Warszawa, Ger. Warschau, Fr. Varsovie)

Warsaw in 1828, who termed it a ' hydrostatic air-pump without cylinders, taps, lids or stoppers," this is attained by using, both for the inlet and the outlet, vertical capillary glass tubes, soldered, the former to somewhere near the bottom, the latter to the top of the vessel . These tubes, being more than 30 in. high, obviously See also:

• ACT (Lat. actus, actum)

act as efficient mercury-traps; but the already considerable height of the pump is thus multiplied by two . This See also:

• CONSIDERATION (from Lat. considerare, to look at closely, examine, generally taken to be from con-, and the base seen in sidus, sideris, a star, the word being supposed to be originally an astrological or astronomical term)

consideration led See also:

• ALEXANDER
• ALEXANDER (1461-1506)
• ALEXANDER (ALEXANDER OF BATTENBERG) (1857-1893)
• ALEXANDER (ALEXANDER OsxENOVici) (1876-1903)
• ALEXANDER, ARCHIBALD (1772—1851)
• ALEXANDER, FRANCIS (1800—1881)
• ALEXANDER, GEORGE (1858— )
• ALEXANDER, JOHN WHITE (1856- )
• ALEXANDER, JOSEPH ADDISON (18o9—186o)
• ALEXANDER, SIR JAMES EDWARD (1803—1885)
• ALEXANDER, WILLIAM (1824— )
• ALEXANDER, WILLIAM LINDSAY (1808—1884)

Alexander See also:

• MITSCHERLICH, EILHARDT (1794–1863)

Mitscherlich, F . Neisen and others to introduce glass valves in lieu of stop-cocks . A pump similar to Topler's construction was devised by Mendeleeff, and the original See also:

• DEVICE

device has been much improved by See also:

• WIEDEMANN, GUSTAV HEINRICH (1826-1899)

Wiedemann, See also:

• BESSEL, FRIEDRICH WILHELM (1784-1846)

Bessel-See also:

• HAGEN
• HAGEN, FRIEDRICH HEINRICH VON DER (178o-1856)

Hagen and others . The best-known pump of this type was invented in 1865 by H . See also:

• SPRENGEL, KURT (1766-1833)

Sprengel, although the idea had been previously conceived The by See also:

• MAGNUS, HEINRICH GUSTAV (1802-1870)

Magnus and See also:

• BUFF (from Fr. bu.ffie, a buffalo)

Buff . The instrument, in its original Dynamic (simplest) form (fig . 4), consists of a vertical capillary Pump. glass tube a of about 1 mm. See also:

• BORE

bore, provided with a lateral See also:

• BRANCH (from the Fr. branche, late Lat. branca, an animal's paw)

branch b near its upper end, which latter, by an india-rubber See also:

• JOINT (through Fr. from Lat. junctum, jungere, to join)

joint governable by a See also:

• SCREW (O.E. scrue, from O. Fr. escroue, mod. ecrou; ultimate origin uncertain; the word, or a similar one, appears in Teutonic languages, cf. Ger. Schraube, Dan. skrue, but Skeat, following Diaz, finds the origin in Lat. scrobs, a ditch, hole, particularl

screw-clamp, communicates with a See also:

• FUNNEL (through an O. Fr. founil, found in Breton, from Lat. infundibulum, that through which anything is poured, from fundere, to pour)

funnel .

The lower end is See also:

• BENT
• BENT (E1. BENI)
• BENT, JAMES THEODORE (1852–1897)

bent into the shape of a See also:

• HOOK, JAMES CLARKE (1819-1907)
• HOOK, THEODORE EDWARD (1788-1841)
• HOOK, WALTER FARQUHAR (1798-1875)

hook, and dips into a pneumatic trough . The vessel to be exhausted is attached to b, and, in See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

order to See also:

• EXTRACT (from Lat. extrahere, to draw out)

extract its gas contents, a properly regulated stream of mercury is allowed to fall through the vertical tube . Every drop of mercury, as it enters from the funnel, entirely closes the narrow tube like a piston, and in going past the See also:

• PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place where the side tube enters entraps a portion of air and carries it down to the trough, where it can be collected . If the vertical tube, measuring from the point where the branch comes in, is a few inches greater than the height of the barometer, and the glass and mercury are perfectly clean, the apparatus slowly but surely produces an almost absolute vacuum . The See also:

• GREAT

great advantages of Sprengel's pump See also:

• LIE, JONAS LAURITZ EDEMIL (1833—1908)
• LIE, MARIUS SOPHUS (1842–1899)

lie in the simplicity of its construction and in the readiness with which it adapts itself to the See also:

• COLLECTING

collecting of the gas . It did excellent service in the hands of See also:

• GRAHAM, SIR GERALD (1831–1899)
• GRAHAM, SIR JAMES ROBERT GEORGE
• GRAHAM, SYLVESTER (1794-1851)
• GRAHAM, THOMAS (1805-1869)

Graham for the extraction of gases occluded in metals . Many improvements upon the original construction have been FIG . 4 . proposed . Sprengel's Air-Pump . Many other devices have been introduced for facilitating the See also:

• PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of vacua . For example Raps in 1893 described an automatic arrangement to be used in connexion with a Topler pump; whilst in 1893 Schulze-Berge devised a rotary form .

For the description of these forms see See also:

• WINKELMANN, EDUARD (1838-1896)

Winkelmann, Handbuch der Physik (19(36), i . 1316 . The See also:

• HISTORY

history of mercurial pumps is treated by S . P . See also:

• THOMPSON
• THOMPSON, FRANCIS (1860-1907)
• THOMPSON, LAUNT (1833-1894)
• THOMPSON, SIR HENRY, BART
• THOMPSON, SIR JOHN SPARROW (1844-1894)
• THOMPSON, THOMAS PERONNET (1783-1869)
• THOMPSON, WILLIAM HEPWORTH (18ro–1886)

Thompson, The Development of the Mercurial Air Pump (1888) . For the production of high vacua, see VACUUM TUBE; LIQUID GASES .