See also:

• ANEMOMETER (from Gr. aveµos, wind, and . rpov, a measure)

ANEMOMETER (from Gr. See also:

• AVE, or FIRN

aveµos, See also:

• WIND
• WIND (a common Teut. word, cognate with Skt. vats, Lat. ventus, cf. " weather," to be of course distinguished from to " wind," to coil or twist, O.Eng. windan, cf. "wander," "wend," &c.)

wind, and . rpov, a measure)  , an See also:

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

instrument for measuring either the velocity or the pressure of the See also:

• WIND
• WIND (a common Teut. word, cognate with Skt. vats, Lat. ventus, cf. " weather," to be of course distinguished from to " wind," to coil or twist, O.Eng. windan, cf. "wander," "wend," &c.)

wind . Anemometers may be divided into two classes, (1) those. that measure the velocity, (2) those that measure the pressure of the wind, but inasmuch as there is a See also:

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

close connexion between the pressure and the velocity, a suitable See also:

• ANEMOMETER (from Gr. aveµos, wind, and . rpov, a measure)

anemometer of either class will give See also:

• INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

information about both these quantities . Velocity anemometers may again be subdivided into two classes, (I) those which do not require a wind See also:

• VANE (formerly spelt " fane," i.e. pennon, flag; cf. Ger. Feline, Du. vaan, Fr. girouette, Ital. banderuola, Ger. Wellerfahne)
• VANE, SIR HENRY (1589-1654)
• VANE, SIR HENRY (1613-1662)

vane or See also:

• WEATHER (O. Eng. weder; the word is common to Teutonic languages; cf. Du. weder, Dan. veir, Icel. ve8r, and Ger. Wetter and Gewitter, storm; the root is wa- to blow, from which is derived " wind ")

weather-See also:

• COCK, EDWARD (1805-1892)

cock, (2) those which do . The See also:

• ROBINSON, EDWARD (1794–1863)
• ROBINSON, HENRY CRABB (1777–1867)
• ROBINSON, JOHN (1575–1625)
• ROBINSON, JOHN (1650-1723)
• ROBINSON, JOHN THOMAS ROMNEY (1792–1882)
• ROBINSON, MARY [" Perdita "] (1758–1800)
• ROBINSON, SIR JOHN BEVERLEY, BART
• ROBINSON, SIR JOSEPH BENJAMIN (1845– )
• ROBINSON, THEODORE (1852-1896)

Robinson anemometer, invented (1846) by Dr See also:

• THOMAS
• THOMAS (c. 1654-1720)
• THOMAS (d. 110o)
• THOMAS, ARTHUR GORING (1850-1892)
• THOMAS, CHARLES LOUIS AMBROISE (1811-1896)
• THOMAS, GEORGE (c. 1756-1802)
• THOMAS, GEORGE HENRY (1816-187o)
• THOMAS, ISAIAH (1749-1831)
• THOMAS, PIERRE (1634-1698)
• THOMAS, SIDNEY GILCHRIST (1850-1885)
• THOMAS, ST
• THOMAS, THEODORE (1835-1905)
• THOMAS, WILLIAM (d. 1554)

Thomas See also:

• ROMNEY (NEw ROMNEY)
• ROMNEY, GEORGE (1734-1802)
• ROMNEY, HENRY SIDNEY, EARL OF (1641-1704)

Romney Robinson, of See also:

• ARMAGH

Armagh See also:

• OBSERVATORY

Observatory, is the best-known and most generally used instrument, and belongs to the first of these . It consists of four hemispherical cups, mounted one on each end of a pair of See also:

• HORIZONTAL

horizontal arms, which See also:

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

lie at right angles to each other and See also:

• FORM (Lat. forma)

form a See also:

• CROSS

cross . A See also:

• VERTICAL (from Lat. vertex, highest point)

vertical See also:

• AXIS (Lat. for " axle ")

axis See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round which the cups turn passes through the centre of the cross; a See also:

• TRAIN (M. Eng. trayn or trayne, derived through Fr. from Late Lat. trahinare, to drag, draw, Lat. trahere, cf. trail, trace, ultimately from the same source)

train of See also:

• WHEEL (0. Eng. hweol, hweohl, &c., cognate with Icel. hjol, Dan. hiul, the Indo-European root is seen in Sanskrit chakra, Gr. r in Aos, circle, whence " cycle ")
• WHEEL, BREAKING ON THE

wheel-See also:

• WORK

work See also:

• COUNTS

counts up the number of turns which this axis makes, and from the number of turns made in any given 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 the velocity of the wind during that time is calculated . The cups are placed symmetrically on the end of the arms, and it is easy to see that the wind always has the hollow of one 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 presented to it; the back of the cup on the opposite end of the cross also faces the wind, but the pressure on it is naturally less, and hence a continual rotation is produced; each cup in turn as it comes round providing the necessary force . The two See also:

• GREAT

great merits of this anemometer are its simplicity and the See also:

• ABSENCE (Lat. absentia)

absence of a wind vane; on the other See also:

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

hand it is not well adapted to leaving a See also:

• RECORD (Lat. recordari, to recall to mind, from cor, heart or mind)

record on See also:

• PAPER
• PAPER (Fr. papier, from Lat. papyrus)

paper of the actual velocity at any definite instant, and hence it leaves a See also:

• SHORT, FRANCIS JOB (1857– )

short but violent gust unrecorded . Unfortunately, when Dr Robinson first designed his anemometer, he stated that no See also:

• MATTER

matter what the See also:

• SIZE

size:of the cups or the length of the arms, the cups always moved with one-third of the velocity of the wind . This result was apparently confirmed by some See also:

• INDEPENDENT

independent experiments, but it is very far from the truth, for it is now known that the actual ratio, or See also:

• FACTOR (from Lat. facere, to make or do)

factor as it is commonly called, of the velocity of the wind to that of the cups depends very largely on the dimensions of the cups and arms, and may have almost any value between two and a little over three . The result has been that wind velocities published in many See also:

• OFFICIAL (Late Lat. QJicialis, for class. Lat. apparitor, from officium, office, duty)

official publications have often been in See also:

• ERROR (Lat. error, from errare, to wander, to err)

error by nearly 5o % . The other forms of velocity anemometer may be described as belonging to the See also:

• WINDMILL

windmill type .

In the Robinson anemometer the axis of rotation is vertical, but with this subdivision the axis of rotation must be parallel to the direction of the wind and therefore horizontal . Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfil the See also:

• SARI

sari.: purpose must be employed . This type of instrument is very little used in See also:

• ENGLAND
• ENGLAND, THE CHURCH OF

England, but seems to be more in favour in See also:

• FRANCE
• FRANCE, ANATOLE (1844– )

France . In cases where the direction of the See also:

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

air See also:

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

motion is always the same, as in the ventilating shafts of mines and buildings for instance, these anemometers, known, however, as air meters, are employed, and give most satisfactory results . Anemometers which measure the pressure may be divided into the See also:

• PLATE

plate and See also:

• TUBE (Lat. tuba)

tube classes, but the former See also:

• TERM

term must be taken as including a See also:

• GOOD, JOHN MASON (1764-1827)

good many See also:

• MISCELLANEOUS

miscellaneous forms . The simplest type of this form consists of a See also:

• FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat plate, which is usually square or circular, while a wind vane keeps this exposed normally to the wind, and the pressure of the wind on its See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

face is balanced 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 distortion of the spring determines the actual force which the wind is exerting on the plate, and this is either read off on a suitable See also:

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

gauge, or leaves a record in the See also:

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

ordinary way by means of a See also:

• PEN (Lat. penna, a feather, pen)

pen See also:

• WRITING
• WRITING (the verbal noun of " to write," O. Eng. writan, to inscribe)

writing on a See also:

• SHEET

sheet of paper moved by clockwork . See also:

• INSTRUMENTS

Instruments of this See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind have been in use for a See also:

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

long See also:

• SERIES (a Latin word from serere, to join)

series of years, and have recorded pressures up to and even exceeding 6o lb per sq. ft., but it is now fairly certain that these high values are erroneous, and due, not to the wind, but to faulty See also:

• DESIGN (Fr. desiin, drawing; Lat. designare, to mark out)

design of the anemometer . The fact is that the wind is continually varying in force, and while the ordinary pressure plate is admirably adapted for measuring the force of a steady and See also:

• UNIFORM

uniform wind, it is entirely unsuitable for following the rapid fluctuations of the natural wind . To make matters worse, the pen which records the motion of the plate is often connected with it by an extensive See also:

• SYSTEM

system of chains and levers . A violent gust strikes the plate, which is driven back and carried by its own momentum far past the position in which a steady wind of the same force would See also:

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

place it; by the time the motion has reached the pen it has been greatly exaggerated by the springiness of the connexion, and not only is the plate itself driven too far back, but also its position is wrongly recorded by the pen; the combined errors See also:

• ACT (Lat. actus, actum)

act the same way, and more than See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

double the real maximum pressure may be indicated on the See also:

• CHART (from Lat. carta, charta, a map)

chart . A modification of the ordinary pressure-plate has recently been designed .

In this arrangement a catch is provided so that the plate being once driven back by the wind cannot return until released by hand; but the catch does not prevent the plate being driven back farther by a gust stronger than the last one that moved it . Examples of these plates are erected on the See also:

• WEST
• WEST, BENJAMIN (1738-1820)
• WEST, NICHOLAS (1461-1533)

west See also:

• COAST (from Lat. costa, a rib, side)

coast of England, where in the See also:

• WINTER, JOHN STRANGE
• WINTER, PETER (c. 1755-1825)

winter fierce See also:

• GALES (mod. Calvi)

gales often occur; a pressure of 30 lb per sq. ft. has not been shown by them, and instances exceeding 20 lb are extremely rare . Many other modifications have been used and suggested . Probably a See also:

• SPHERE (Gr. vclsa?pa, a ball or globe)

sphere would prove most useful for a pressure anemometer, since owing to its symmetrical shape it would not require a weathercock . A small See also:

• LIGHT

light sphere See also:

• HANGING

hanging from the end of 30 or 40 ft. of See also:

• FINE

fine sewing See also:

• COTTON
• COTTON (Fr. coton; from Arab. qutun)
• COTTON, CHARLES (163o–1687)
• COTTON, GEORGE EDWARD LYNCH (1813–1866)
• COTTON, JOHN (1585–1652)
• COTTON, SIR ROBERT BRUCE

cotton has been employed to measure the wind velocity passing over a See also:

• KITE

kite, the tension of the cotton being recorded, and this See also:

• PLAN
• PLAN (from Lat. planes, flat)

plan has given satisfactory results . See also:

• LIND, JENNY

Lind's anemometer, which consists simply of a lJ tube containing liquid with one end See also:

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

bent into a horizontal direction to face the wind, is perhaps the See also:

• ORIGINAL

original form from which the tube class of instrument has sprung . If the wind blows into the mouth of a tube it causes an increase of pressure inside and also of course an equal increase in all closed vessels with which the mouth is in air-tight communication . If it blows horizontally over the open end of a vertical tube it causes a decrease of pressure, but this fact is not of any See also:

• PRACTICAL

practical use in anemometry, because the magnitude of the decrease depends on the wind striking the tube exactly at right angles to its axis, the most trifling departure from the true direction causing great See also:

• VARIATIONS
• VARIATIONS, CALCULUS
• VARIATIONS, CALCULUS OF

variations in the magnitude . The pressure tube anemometer (fig . 1) utilizes the increased pressure in the open mouth of a straight tube facing the wind, and the decrease of pressure caused inside when the wind blows over a See also:

• RING (O.E. hring; a word common to Teutonic languages; and probably cognate with the Lat. circus, Gr. KtpKOS or KpLKOS, Skt'. chakra, wheel, circle, cf. also " harangue "); in art, a band of circular shape of varying sizes, made of any material and used f

ring of small holes drilled through 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 of a vertical tube which is closed at the upper end . The pressure See also:

• DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences on which the See also:

• ACTION

action depends are very small, and See also:

• SPECIAL

special means are required to See also:

• REGISTER

register them, but in the ordinary form of recording anemometer (fig . 2), any wind capable of turning the vane which keeps the mouth of the tube facing the wind is capable of See also:

• REGISTRATION

registration .

The great See also:

• ADVANTAGE

advantage of the tube anemometer lies in the fact that the exposed See also:

• PART

part can be mounted on a high See also:

• POLE (FAMILY)
• POLE, REGINALD (1500-1558)
• POLE, RICHARD DE LA (d. 1525)
• POLE, WILLIAM (1814—1900)

pole, and requires no oiling or See also:

• ATTENTION (from Lat. ad-tendo, await, expect; the condition of being " stretched " or " tense ")

attention for years; and the registering part can be placed in any convenient position, no matter how far from the See also:

• EXTERNAL

external part . Two connecting tubes are required . It might appear at first sight as though one connexion would serve, but the differences in pressure on which these instruments depend are so See also:

• MINUTE
• MINUTE (Lat. minutes, small; minuere, to make less)

minute, that the pressure of the air in the See also:

• ROOM

room where the recording part is placed has to be considered . Thus if the instrument depends on the pressure or suction effect alone, and this pressure or suction is measured against the air pressure in an ordinary room, in which the doors and windows are carefully closed and a newspaper is then burnt up the See also:

• CHIMNEY (through the Fr. cheminee, from caminata, sc. camera, a Lat. derivative of caminus, an oven or furnace)

chimney, an effect may be produced equal to a wind of ro m. an See also:

• HOUR

hour; and the opening of a window in rough weather, or the opening of a See also:

• DOOR (corresponding to the Gr. Bbpa,. Lat. fores or valvae; the English word, with other forms common in allied languages, comes from the same Indo-European stem as the Gr. Obpa and Lat. fares)

door, may entirely alter the registration . The connexion between the velocity and the pressure of the wind is one that is not yet known with See also:

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

absolute certainty . Many See also:

• TEXT (Lat. textum, woven fabric, from texere, to weave)

text-books on See also:

• ENGINEERING

engineering give the relation P= •005 v2 when P is the pressure in lb per sq. ft. and v the velocity in See also:

• MILES, NELSON APPLETON (1839— )

miles per hour . The See also:

• HISTORY

history of this untrue relation is curious . It was given about the end of the 18th See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

century as based on some experiments, but with a footnote stating that little reliance could be placed on it . The statement without the qualifying See also:

• NOTE
• NOTE (Lat. nota, mark, sign, from noscere, to know)

note was copied from See also:

• BOOK

book to book, and at last received See also:

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

general See also:

• ACCEPTANCE (Lat. acceptare, frequentative form of accipere, to receive)

acceptance . There is no doubt that under See also:

• AVERAGE

average conditions of atmospheric See also:

• DENSITY (Lat. densus, thick)

density, the .005 should be replaced by •003, for many independent authorities using different methods have found values very close to this last figure . It is probable that the wind pressure is not strictly proportional to the extent of the See also:

• SURFACE

surface exposed . Pressure plates are generally of moderate size, from a See also:

• HALF

half or See also:

• QUARTER (through Fr. from Lat. quartarius, fourth part)

quarter of a sq. ft. up to two or three sq. ft., are round or square, and for these sizes, and shapes, and of course for a flat surface, the relation P= .003 V2 is fairly correct .

In the tube anemometer also it is really the pressure that is measured, although the See also:

• SCALE
• SCALE (1) A

scale is usually graduated as a velocity scale . In cases where the density of the air is not of average value, as on a high See also:

• MOUNTAIN (0. Fr. montaigne; popular Lat. montanea, an adjectival form from the classical mons, montis, whence Eng. " mount," a form usually used along with the name of an individual mountain, e.g. Mt Everest)
• MOUNTAIN, THE (La Montagne)

mountain, or with an exceptionally See also:

• LOW, SETH (1850- )
• LOW, WILL HICOK (1853- )

low See also:

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

barometer for example, an See also:

• ALLOWANCE (from "allow,' derived through 0. Fr. alouer from the two Lat. origins adlaudare, to praise, and allocare, to assign a place; so that the English word combined the general idea of "assigning with approval")

allowance must be made . Approximately 11% should be added to the velocity recorded by a tube anemometer for each See also:

• ROOD (O.E. rod, a stick, another form of " rod, O.E. rodd, possibly cognate with Lat. rudis, a staff)

rood ft. that it stands above 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-level . (W . H .