the placenta), and the micropyle is at the opposite extremity, there
being a short funicle, the ovule is _orthotropous_. This form is well
seen in Polygonaceae (fig. 112), Cistaceae, and most gymnosperms. In
such an ovule a straight line drawn from the hilum to the micropyle
passes along the axis of the ovule. Where, by more rapid growth on one
side than on the other, the nucellus, together with the integuments, is
curved upon itself, so that the micropyle approaches the hilum, and
ultimately is placed close to it, while the chalaza is at the hilum, the
ovule is _campylotropous_ (fig. 110). Curved ovules are found in
Cruciferae, and Caryophyllaceae. The inverted or _anatropous_ ovule
(fig. 111) is the commonest form amongst angiosperms. In this ovule the
apex with the micropyle is turned towards the point of attachment of the
funicle to the placenta, the chalaza being situated at the opposite
extremity; and the funicle, which runs along the side usually next the
placenta, coalesces with the ovule and constitutes the _raphe_ (r),
which often forms a ridge. The anatropous ovule arises from the placenta
as a straight or only slightly curved cellular process, and as it grows,
gradually becomes inverted, curving from the point of origin of the
integuments (cf. figs. 106, 107). As the first integument grows round
it, the amount of inversion increases, and the funicle becomes adherent
to the side of the nucellus. Then if a second integument be formed it
covers all the free part of the ovule, but does not form on the side to
which the raphe is adherent. These may be taken as the three types of
ovule; but there are various intermediate forms, such as
_semi-anatropous_ and others.
The position of the ovule relative to the ovary varies. When there is a
single ovule, with its axis vertical, it may be attached to the placenta
at the base of the ovary (_basal placenta_), and is then _erect_, as in
Polygonaceae and Compositae; or it may be inserted a little above the
base, on a parietal placenta, with its apex upwards, and then is
_ascending_, as in _Parietaria_. It may hang from an apicilar placenta
at the summit of the ovary, its apex being directed downwards, and is
_inverted_ or _pendulous_, as in _Hippuris vulgaris_; or from a parietal
placenta near the summit, and then is _suspended_, as in _Daphne
Mezereum_, Polygalaceae and Euphorbiaceae. Sometimes a long funicle
arises from a basal placenta, reaches the summit of the ovary, and there
bending over suspends the ovule, as in _Armeria_ (sea-pink); at other
times the hilum appears to be in the middle, and the ovule becomes
_horizontal_. When there are two ovules in the same cell, they may be
either _collateral_, that is, placed side by side (fig. 92), or the one
may be erect and the other inverted, as in some species of _Spiraea_ and
_Aesculus_; or they may be placed one above another, each directed
similarly, as is the case in ovaries containing a moderate or definite
number of ovules. Thus, in the ovary of Leguminous plants (fig. 91), the
ovules, o, are attached to the extended marginal placenta, one above the
other, forming usually two parallel rows corresponding to each margin of
the carpel. When the ovules are _definite_ (i.e. are uniform, and can be
counted), it is usual to find their attachment so constant as to afford
good characters for classification. When the ovules are very numerous
(_indefinite_), while at the same time the placenta is not much
developed, their position exhibits great variation, some being directed
upwards, others downwards, others transversely; and their form is
altered by pressure into various polyhedral shapes. In such cases it
frequently happens that some of the ovules are arrested in their
development and become abortive.
[Illustration: From Strasburger's _Lehrbuch der Botanik_, by permission
of Gustav Fischer.
FIG. 112.--Ovary of _Polygonum Convolvulus_ in longitudinal section
during fertilization. (X 48.)
fs, Stalk-like base of ovary,
fu, Funicle.
cha, Chalaza.
nu, Nucellus.
mi, Micropyle.
ii, inner, ie, outer integument,
e, Embryo-sac.
ek, Nucleus of embryo-sac.
ei, Egg-apparatus.
an, Antipodal cells.
g, Style.
n, Stigma.
p, Pollen-grains.
ps, Pollen-tubes.]
[Illustration: FIG. 113.--Vertical section of the ovule of the Scotch
Fir (_Pinus sylvestris_) in May of the second year, showing the enlarged
embryo-sac b, full of endosperm cells, and pollen-tubes c, penetrating
the summit of the nucellus after the pollen has entered the large
micropyle.]
Fertilization.
When the pistil has reached a certain stage in growth it becomes ready
for fertilization. Pollination having been effected, and the
pollen-grain having reached the stigma in angiosperms, or the summit of
the nucellus in gymnosperms, it is detained there, and the viscid
secretion from the glands of the stigma in the former case, or from the
nucellus in the latter, induce the protrusion of the intine as a
pollen-tube through the pores of the grain. The pollen-tube or tubes
pass down the canal (fig. 112), through the conducting tissue of the
style when present, and reach the interior of the ovary in angiosperms,
and then pass to the micropyle of the ovule, one pollen-tube going to
each ovule. Sometimes the micropyle lies close to the base of the style,
and then the pollen-tube enters it at once, but frequently it has to
pass some distance into the ovary, being guided in its direction by
various contrivances, as hairs, grooves, &c. In gymnosperms the
pollen-grain resting on the apex of the nucellus sends out its
pollen-tubes, which at once penetrate the nucellus (fig. 113). In
angiosperms when the pollen-tube reaches the micropyle it passes down
into the canal, and this portion of it increases considerably in size.
Ultimately the apex of the tube comes in contact with the tip of the
embryo-sac and perforates it. The male cells in the end of the
pollen-tube are then transmitted to the embryo-sac and fertilization is
effected. Consequent upon this, after a longer or shorter period, those
changes commence in the embryo-sac which result in the formation of the
embryo plant, the ovule also undergoing changes which convert it into
the seed, and fit it for a protective covering, and a store of nutriment
for the embryo. Nor are the effects of fertilization confined to the
ovule; they extend to other parts of the plant. The ovary enlarges, and,
with the seeds enclosed, constitutes the fruit, frequently incorporated
with which are other parts of the flower, as receptacle, calyx, &c. In
gymnosperms the pollen-tubes, having penetrated a certain distance down
the tissue of the nucellus, are usually arrested in growth for a longer
or shorter period, sometimes nearly a year. Fruit and seed are discussed
in a separate article--FRUIT. (A. B. R.)
FLOWERS, ARTIFICIAL. Imitations of natural flowers are sometimes made
for scientific purposes (as the collection of glass flowers at Harvard
University, which illustrates the flora of the United States), but more
often as articles of decoration and ornament. A large variety of
materials have been used in their manufacture by different peoples at
different times--painted linen and shavings of stained horn by the
Egyptians, gold and silver by the Romans, rice-paper by the Chinese,
silkworm cocoons in Italy, the plumage of highly coloured birds in South
America, wax, small tinted shells, &c. At the beginning of the 18th
century the French, who originally learnt the art from the Italians,
made great advances in the accuracy of their reproductions, and towards
the end of that century the Paris manufacturers enjoyed a world-wide
reputation. About the same time the art was introduced into England by
French refugees, and soon afterwards it spread also to America. The
industry is now a highly specialized one and comprises a large number of
operations performed by separate hands. Four main processes may be
distinguished. The first consists of cutting up the various fabrics and
materials employed into shapes suitable for forming the leaves, petals,
&c.; this may be done by scissors, but more often stamps are employed
which will cut through a dozen or more thicknesses at one blow. The
veins of the leaves are next impressed by means of a die, and the petals
are given their natural rounded forms by goffering irons of various
shapes. The next step is to assemble the petals and other parts of the
flower, which is built up from the centre outwards; and the fourth is to
mount the flower on a stalk formed of brass or iron wire wrapped round
with suitably coloured material, and to fasten on the leaves required to
complete the spray.
FLOYD, JOHN (1572-1649), English Jesuit, was born in Cambridgeshire in
1572. He entered the Society of Jesus when at Rome in 1592 and is also
known as Daniel a Jesu, Hermannus Loemelius, and George White, the names
under which he published a score of controversial treatises. He had
considerable fame both as a preacher and teacher, and was frequently
arrested in England. His last years were spent at Louvain and he died at
St Omer on the 15th of September 1649. His brother Edward Floyd was
impeached and sentenced by the Commons in 1621 for speaking
disparagingly of the elector palatine.
FLOYD, JOHN BUCHANAN (1807-1863), American politician, was born at
Blacksburg, Virginia, on the 1st of June 1807. He was the son of John
Floyd (1770-1837), a representative in Congress from 1817 to 1829 and
governor of Virginia from 1830 to 1834. After graduating at South
Carolina College in 1826, the son practised law in his native state and
at Helena, Arkansas, and in 1839 settled in Washington county, Virginia,
which in 1847-1849 and again in 1853 he represented in the state
legislature. Meanwhile, from 1849 to 1852, he was governor of Virginia,
in which position he recommended to the legislature the enactment of a
law laying an import tax on the products of such states as refused to
surrender fugitive slaves owned by Virginia masters. In March 1857 he
became secretary of war in President Buchanan's cabinet, where his lack
of administrative ability was soon apparent. In December 1860, on
ascertaining that Floyd had honoured heavy drafts made by government
contractors in anticipation of their earnings, the president requested
his resignation. Several days later Floyd was indicted for malversation
in office, but the indictment was overruled on technical grounds. There
is no proof that he profited by these irregular transactions; in fact he
went out of the office financially embarrassed. Though he had openly
opposed secession before the election of Lincoln, his conduct after that
event, especially after his breach with Buchanan, fell under suspicion,
and he was accused of having sent large stores of government arms to
Southern arsenals in anticipation of the Civil War. In the last days of
his term he apparently had such an intention, but during the year 1860
the Southern States actually received less than their full quota of
arms. After the secession of Virginia he was commissioned a
brigadier-general in the Confederate service. He was first employed in
some unsuccessful operations in western Virginia, and in February 1862
became commander of the Confederate forces at Fort Donelson, from which
he fled with his second in command, General Gideon J. Pillow, on the
night of February 18, leaving General Simon B. Buckner to surrender to
General Grant. A fortnight later President Davis relieved him of his
command. He died at Abingdon, Virginia, on the 26th of August 1863.
FLOYER, SIR JOHN (1649-1734), English physician and author, was born at
Hinters in Staffordshire, and was educated at Oxford. He practised in
Lichfield, and it was by his advice that Dr Johnson, when a child, was
taken by his mother to be touched by Queen Anne for the king's evil on
the 30th of March 1714. He died on the 1st of February 1734. Floyer was
an advocate of cold bathing, introduced the practice of counting the
rate of the pulse-beats, and gave an early account of the pathological
changes in the lungs associated with emphysema.
His writings include:--[Greek: Pharmako-Basanos]: _or the Touchstone
of Medicines, discovering the virtues of Vegetables, Minerals and
Animals, by their Tastes and Smells_ (2 vols., 1687); _The
praeternatural State of animal Humours described by their sensible
Qualities_ (1696); _An Enquiry into the right Use and Abuses of the
hot, cold and temperate Baths in England_ (1697); _A Treatise of the
Asthma_ (1st ed., 1698); _The ancient_ [Greek: Psychrolousia]
_revived, or an Essay to prove cold Bathing both safe and useful_
(London, 1702; several editions 8vo; abridged, Manchester, 1844,
12mo); _The Physician's Pulse-watch_ (1707-1710); _The Sibylline
Oracles, translated from the best Greek copies, and compared with the
sacred Prophecies_ (1st ed., 1713); _Two Essays: the first Essay
concerning the Creation, Aetherial Bodies, and Offices of good and bad
Angels; the second Essay concerning the Mosaic System of the World_
(Nottingham, 1717); _An Exposition of the Revelations_ (1719); _An
Essay to restore the Dipping of Infants in their Baptism_ (1722);
_Medicina Gerocomica, or the Galenic Art of preserving old Men's
Healths_ (1st ed., 1724); _A Comment on forty-two Histories described
by Hippocrates_ (1726).
FLUDD, or FLUD, ROBERT [ROBERTUS DE FLUCTIBUS] (1574-1637), English
physician and mystical philosopher, the son of Sir Thomas Fludd,
treasurer of war to Queen Elizabeth in France and the Low Countries, was
born at Milgate, Kent. After studying at St John's College, Oxford, he
travelled in Europe for six years, and became acquainted with the
writings of Paracelsus. He subsequently returned to Oxford, became a
member of Christ Church, took his medical degrees, and ultimately became
a fellow of the College of Physicians. He practised in London with
success, though it is said that he combined with purely medical
treatment a good deal of faith-healing. Following Paracelsus, he
endeavoured to form a system of philosophy founded on the identity of
physical and spiritual truth. The universe and all created things
proceed from God, who is the beginning, the end and the sum of all
things, and to him they will return. The act of creation is the
separation of the active principle (light) from the passive (darkness)
in the bosom of the divine unity (God). The universe consists of three
worlds; the archetypal (God), the macrocosm (the world), the microcosm
(man). Man is the world in miniature, all the parts of both
sympathetically correspond and act upon each other. It is possible for
man (and even for the mineral and the plant) to undergo transformation
and to win immortality. Fludd's system may be described as a
materialistic pantheism, which, allegorically interpreted, he put
forward as containing the real meaning of Christianity, revealed to Adam
by God himself, handed down by tradition to Moses and the patriarchs,
and revealed a second time by Christ. The opinions of Fludd had the
honour of being refuted by Kepler, Gassendi and Mersenne. Though rapt in
mystical speculation, Fludd was a man of varied attainments. He did not
disdain scientific experiments, and is thought by some to be the
original inventor of the barometer. He was an ardent defender of the
Rosicrucians, and De Quincey considers him to have been the immediate,
as J.V. Andrea was the remote, father of freemasonry. Fludd died on the
8th of September 1637.
See J.B. Craven, _Robert Fludd, the English Rosicrucian_ (1902), where
a list of his works is given; A.E. Waite, _The Real History of the
Rosicrucians_ (1887); De Quincey, _The Rosicrucians and Freemasons_;
J. Hunt, _Religious Thought in England_ (1870), i. 240 seq. His works
were published in 6 vols., Oppenheim and Gouda, 1638.
FLUGEL, GUSTAV LEBERECHT (1802-1870), German orientalist, was born at
Bautzen on the 18th of February 1802. He received his early education at
the gymnasium of his native town, and studied theology and philology at
Leipzig. Gradually he devoted his attention chiefly to Oriental
languages, which he studied in Vienna and Paris. In 1832 he became
professor at the _Furstenschule_ of St Afra in Meissen, but ill-health
compelled him to resign that office in 1850, and in 1851 he went to
Vienna, where he was employed in cataloguing the Arabic, Turkish and
Persian manuscripts of the court library. He died at Dresden on the 5th
of July 1870.
Flugel's chief work is an edition of the bibliographical and
encyclopaedic lexicon of Haji Khalfa, with Latin translation (7 vols.,
London and Leipzig, 1835-1858). He also brought out an edition of the
Koran (Leipzig, 1834 and again 1893); then followed _Concordantiae
Corani arabicae_ (Leipzig, 1842 and again 1898); _Mani, seine Lehren
und seine Schriften_ (Leipzig, 1862); _Die grammatischen Schulen der
Araber_ (Leipzig, 1862); and _Ibn Kutlubugas Krone der
Lebensbeschreibungen_ (Leipzig, 1862). An edition of
_Kitab-al-Fihrist_, prepared by him, was published after his death.
FLUGEL, JOHANN GOTTFRIED (1788-1855), German lexicographer, was born at
Barby near Magdeburg, on the 22nd of November 1788. He was originally a
merchant's clerk, but emigrating to the United States in 1810, he made a
special study of the English language, and returning to Germany in 1819,
was in 1824 appointed lector of the English language in the university
of Leipzig. In 1838 he became American consul, and subsequently
representative and correspondent of the Smithsonian Institution at
Washington and several other leading American literary and scientific
institutions. He died at Leipzig on the 24th of June 1855.
The fame of Flugel rests chiefly on the _Vollstandige
englisch-deutsche und deutsch-englische Worterbuch_, first published
in 2 vols. (Leipzig) in 1830, which has had an extensive circulation
not only in Germany but in England and America. In this work he was
assisted by J. Sporschil, and a new and enlarged edition, edited by
his son Felix Flugel (1820-1904), was published at Brunswick
(1890-1892). Another edition, in two volumes, edited by Prof. Immanuel
Schmidt and S. Tanger appeared (Brunswick, London & New York) in 1906.
Among his other works are--_Vollstandige engl. Sprachlehre_
(1824-1826); _Triglotte, oder kaufmannisches Worterbuch in drei
Sprachen, Deutsch, Englisch und Franzosisch_ (1836-1840); _Kleines
Kaufmannisches Handworterbuch in drei Sprachen_ (1840); and
_Praktisches Handbuch der engl. Handelscorrespondenz_ (1827, 9th ed.
1873). All these have passed through several editions. In addition,
Flugel also published in the English language: _A series of Commercial
Letters_ (Leipzig, 1822), a 9th edition of which appeared in 1874
under the title _Practical Mercantile Correspondence_ and a _Practical
Dictionary of the English and German Languages_ (2 vols., Hamburg and
Leipzig, 1847-1852; 15th ed., Leipzig, 1891). The last was continued
and re-edited by his son Felix.
FLUKE (probably connected with the Ger. _flach_, flat), a name given to
several kinds of fish, flat in shape, especially to the common flounder;
also the name of a trematoid worm, resembling a flounder in shape, which
as a parasite infects the liver and neighbouring organs of certain
animals, especially sheep, and causes liver-rot. The most common is the
_Fasciola hepatica_ (see TREMATODES). It is also the name of a species
of kidney potato. Probably from a resemblance to the shape of the fish,
"fluke" is the name given to the holding-plates, triangular in shape, at
the end of the arms of an anchor, and to the triangular extremities of
the tail of a whale. The use of the word as a slang expression for a
lucky accident appears to have been first applied in billiards to an
unintentional scoring shot.
FLUME (through an O. Fr. word _flum_, from the Lat. _flumen_, a river),
a word formerly used for a stream, and particularly for the tail of a
mill-race. It is used in America for a very narrow gorge running between
precipitous rocks, with a stream at the bottom, but more frequently is
applied to an artificial channel of wood or other material for the
diversion of a stream of water from a river for purposes of irrigation,
for running a sawmill, or for various processes in the hydraulic method
of gold-mining (see AQUEDUCT).
FLUMINI MAGGIORE, a town of the province of Cagliari, Sardinia, 10 m. by
road N. of Iglesias, and 5 m. from the W. coast. Pop. (1901) town 3908;
commune 9647. It is the centre of a considerable lead and zinc mining
district. Three miles to the S. are the ruins of a temple erected
probably in the time of Commodus (_Corpus inscr. Lat._ x., Berlin, 1883,
No. 7539). They seem to mark the site of Metalla (mines), a station on
the coast road from Sulci to Tharros, and the centre of the mining
district in Roman times. At Flumini Maggiore itself were found two
ingots of lead, one bearing a stamp with Hadrian's name.
FLUORANTHENE, C15H10, also known as idryl, a hydrocarbon occurring with
phenanthrene, pyrene, diphenyl, and other substances in "Stupp" fat (the
fat obtained in working up the mercury ores in Idria), and also in the
higher boiling fractions of the coal tar distillate. It was discovered
by R. Fittig in 1878, who, with Gebhard and H. Liepmann, elucidated its
constitution (see _Ann._, 1879, 200, p. 1). The hydrocarbons are
separated from the "Stupp" by means of alcohol, the soluble portion on
distillation giving first phenanthrene and then a mixture of pyrene and
fluoranthene. From the tar distillate, the chrysene can be fractionally
precipitated, and the fluoranthene can be separated from most of the
pyrene by fractional distillation in a partial vacuum. In either case
the two hydrocarbons are finally separated by fractional crystallization
of their picrates, which are then decomposed by ammonia. Fluoranthene
crystallizes in large slender needles or monoclinic tables, melting at
109-110 deg. C. and boiling at 250-251 deg. C. (60 mm.). It is easily
soluble in hot alcohol, ether and carbon bisulphide. On oxidation with
chromic acid it forms a quinone, C15H8O2, and an [alpha]-diphenylene
ketocarboxylic acid
C6H4 \
. > CO
C6H3 / -- CO2H.
The picrate melts at 182-183 deg. C.
FLUORENE ([alpha]-diphenylene methane), C13H10 or (C6H4)2CH2, a
hydrocarbon found in coal-tar. It is obtained from the higher boiling
fractions, after separation of naphthalene and anthracene, by fractional
distillation, the portion boiling between 290-340 deg. C. being taken.
The fluorene is separated from this by placing it in a freezing mixture,
and is then redistilled or crystallized from glacial acetic acid, or
purified by means of its picrate. It may be prepared by distilling
diphenylene ketone over zinc dust, or by heating it with hydriodic acid
and phosphorus to 150-160 deg. C.; and also by passing the vapour of
diphenyl methane through a red hot tube. It crystallizes in colourless
plates, possessing a violet fluorescence, melting at 112-113 deg. and
boiling at 293-295 deg. C. By oxidation with chromic acid in glacial
acetic acid solution, it is converted into diphenylene ketone
(C6H4)2.CO; whilst on heating with hydriodic acid and phosphorus to
250-260 deg. C. it gives a hydro derivative of composition C18H22.
FLUORESCEIN, or RESORCIN-PHTHALEIN, C20H12O5, in chemistry, a compound
discovered in 1876 by A. v. Baeyer by the condensation of phthalic
anhydride with resorcin at 195-200 deg. C. (_Ann._, 1876, 183, p. 1). The
two reacting substances are either heated alone or with zinc chloride for
some hours, and the melt obtained is boiled out with water, washed by
dilute alcohol, extracted by means of sodium hydrate, and the solution so
obtained is precipitated by an acid. The precipitate is well washed with
water and then dried. By repeating this process two or three times, the
fluorescein may be obtained in a very pure condition. It forms a yellow
amorphous powder, insoluble in water but soluble in alcohol, and
crystallizing from the alcoholic solution in small dark red nodules. It
is readily soluble in solutions of the caustic alkalis, the solution
being of a dark red colour and showing (especially when largely diluted
with water) a brilliant green fluorescence. It was so named on account of
this last character. By brominating fluorescein in glacial acetic acid
solution, _eosin_ (tetrabromfluorescein) is obtained, the same compound
being formed by heating 3.5-dibrom-2.4-dioxybenzoylbenzoic acid above its
melting point (R. Meyer, _Ber._, 1895, 28, p. 1576). It crystallizes
from alcohol in yellowish red needles, and dyes silk, wool, and mordanted
cotton a fine pink colour. When heated with caustic alkalis it yields
dibromresorcin and dibrommonoresorcin-phthalein. The corresponding iodo
compound is known as _erythrosin_. Fluorescein is readily nitrated,
yielding a di- or tetra-nitro compound according to conditions. The
entrance of the negative nitro group into the molecule weakens the
central pyrone ring in the fluorescein nucleus and the di-and tetra-nitro
compounds readily yield hydrates (see J.T. Hewitt and B.W. Perkins,
_Jour. Chem. Soc._, 1900, p. 1326). By the action of ammonia or amines
the di-nitro fluoresceins are converted into yellow dyestuffs (F.
Reverdin, _Ber_., 1897, 30, p. 332). Other dyestuffs obtained from
fluorescein are safrosine or eosin scarlet (dibromdinitrofluorescein) and
rose Bengal (tetraiodotetrachlorfluorescein).
On fusion with caustic alkali, fluorescein yields resorcin, C6H4(OH)2,
and monoresorcin phthalein (dioxybenzoylbenzoic acid), (HO)2C6H3.CO.C
H4.COOH. With zinc dust and caustic soda it yields fluorescin. By
warming fluorescein with excess of phosphorus pentachloride it yields
fluorescein chloride, C20H10O3Cl2 (A. Baeyer), which crystallizes from
alcohol in small prisms, melting at 252 deg. C. When heated with
aniline and aniline hydrochloride, fluorescein yields a colourless
anilide (O. Fischer and E. Hepp, _Ber_., 1893, 26, p. 2236), which is
readily methylated by methyl iodide and potash to a
fluoresceinanilidedimethyl ether, which when heated for six hours to
150 deg. C. with acetic and hydrochloric acids, is hydrolysed and
yields a colourless fluoresceindimethyl ether, which melts at 198 deg.
C. On the other hand, by heating fluorescein with caustic potash,
methyl iodide and methyl alcohol, a coloured (yellow) dimethyl ether,
melting at 208 deg. C. is obtained (Fischer and Hepp). By heating the
coloured dimethyl ether with caustic soda, the monomethyl ether is
obtained (O. Fischer and E. Hepp, _Ber_., 1895, 28, p. 397); this
crystallizes in triclinic tables, and melts at 262 deg. C. It is to be
noted that the colourless monomethyl ether fluoresces strongly in
alkaline solution, the dimethyl ether of melting point 208 deg.
fluoresces only in neutral solution (e.g., in alcoholic solution), and
the dimethyl ether of melting point 198 deg. C. only in concentrated
hydrochloric or sulphuric acid solution (Fischer and Hepp).
Considerable discussion has taken place as to the position held by the
hydroxyl groups in the fluorescein molecule, C. Graebe (_Ber_., 1895,
28, p. 28) asserting that they were in the ortho position to the
linking carbon atom of the phthalic anhydride residue. G. Heller
(_Ber_., 1895, 28, p. 312), however, showed that
monoresorcin-phthalein when brominated in glacial acetic acid gives a
dibrom derivative which, with fuming sulphuric acid, yields
dibromxanthopurpurin (1.3-dioxy-2.4-dibromanthraquinone), a reaction
which is only possible if the fluorescein (from which the
monoresorcin-phthalein is derived) contains free hydroxyl groups in
the para position to the linking carbon atom of the phthalic anhydride
residue.
FLUORESCENCE. In a paper read before the Royal Society of Edinburgh in
1833, Sir David Brewster described a remarkable phenomenon he had
discovered to which he gave the name of "internal dispersion." On
admitting a beam of sunlight, condensed by a lens, into a solution of
chlorophyll, the green colouring matter of leaves (see fig. 1), he was
surprised to find that the path of the rays within the fluid was marked
by a bright light of a blood-red colour, strangely contrasting with the
beautiful green of the fluid when seen in moderate thickness. Brewster
afterwards observed the same phenomenon in various vegetable solutions
and essential oils, and in some solids, amongst which was fluor-spar. He
believed this effect to be due to coloured particles held in suspension.
A few years later, Sir John Herschel independently discovered that if a
solution of quinine sulphate, which, viewed by transmitted light,
appears colourless and transparent like water, were illuminated by a
beam of ordinary daylight, a peculiar blue colour was seen in a thin
stratum of the fluid adjacent to the surface by which the light entered.
The blue light was unpolarized and passed freely through many inches of
the fluid. The incident beam, after having passed through the stratum
from which the blue light came, was not sensibly enfeebled or coloured,
but yet it had lost the power of producing the characteristic blue
colour when admitted into a second solution of quinine sulphate. A beam
of light modified in this mysterious manner was called by Herschel
"epipolized." Brewster showed that epipolic was merely a particular case
of internal dispersion, peculiar only in this respect, that the rays
capable of dispersion were dispersed with unusual rapidity.
[Illustration: FIG. 1.]
The investigation of this phenomenon was afterwards taken up by Sir G.G.
Stokes, to whom the greater part of our present knowledge of the subject
is due. Stokes's first paper "On the Change of the Refrangibility of
Light" appeared in 1852. He repeated the experiments of Brewster and
Herschel, and considerably extended them. These experiments soon led him
to the conclusion that the effect could not be due, as Brewster had
imagined, to the scattering of light by suspended particles, but that
the dispersed beam actually differed in refrangibility from the light
which excited it. He therefore termed it "true internal dispersion" to
distinguish it from the scattering of light, which he called "false
internal dispersion." As this name, however, is apt to suggest
Brewster's view of the phenomenon, he afterwards abandoned it as
unsatisfactory, and substituted the word "fluorescence." This term,
derived from fluor-spar after the analogy of opalescence from opal, does
not presuppose any theory. To examine the nature of the fluorescence
produced by quinine, Stokes formed a pure spectrum of the sun's rays in
the usual manner. A test-tube, filled with a dilute solution of quinine
sulphate, was placed just outside the red end of the spectrum and then
gradually moved along the spectrum to the other extremity. No
fluorescence was observed as long as the tube remained in the more
luminous portion, but as soon as the violet was reached, a ghost-like
gleam of blue light shot right across the tube. On continuing to move
the tube, the blue light at first increased in intensity and afterwards
died away, but not until the tube had been moved a considerable distance
into the ultra-violet part of the spectrum. When the blue gleam first
appeared it extended right across the tube, but just before disappearing
it was confined to a very thin stratum on the side at which the exciting
rays entered. Stokes varied this experiment by placing a vessel filled
with the dilute solution in a spectrum formed by a train of prisms. The
appearance is illustrated diagrammatically in fig. 2. The greater part
of the light passed freely as if through water, but from about half-way
between the Fraunhofer lines G and H to far beyond the extreme violet,
the incident rays gave rise to light of a sky-blue colour, which
emanated in all directions from the portion of the fluid (represented
white in fig. 2) which was under the influence of the incident rays. The
anterior surface of the blue space coincided, of course, with the inner
surface of the glass vessel. The posterior surface marked the distance
to which the incident rays were able to penetrate before they were
absorbed. This distance was at first considerable, greater than the
diameter of the vessel, but decreased with great rapidity as the
refrangibility of the incident light increased, so that from a little
beyond the extreme violet to the end, the blue space was reduced to an
excessively thin stratum. This shows that the fluid is very opaque to
the ultra-violet rays. The fixed lines in the violet and invisible part
of the solar spectrum were represented by dark lines, or rather planes,
intersecting the blue region. Stokes found that the fluorescent light is
not homogeneous, for on reducing the incident rays to a narrow band of
homogeneous light, and examining the dispersed beam through a prism, he
found that the blue light consisted of rays extending over a wide range
of refrangibility, but not into the ultra-violet.
[Illustration: FIG. 2.]
Another method, which Stokes found especially useful in examining
different substances for fluorescence, was as follows. Two coloured
media were prepared, one of which transmitted the upper portion of the
spectrum and was opaque to the lower portion, while the second was
opaque to the upper and transparent to the lower part of the spectrum.
These were called by Stokes "complementary absorbents." No pair could be
found which were exactly complementary, of course, but the condition was
approximately fulfilled by several sets of coloured glasses or
solutions. One such combination consisted of a deep-blue solution of
ammioniacal copper sulphate and a yellow glass coloured with silver. The
two media together were almost opaque. The light of the sun being
admitted through a hole in the window-shutter, a white porcelain tablet
was laid on a shelf fastened in front of the hole. If the vessel
containing the blue solution was placed so as to cover the hole, and the
tablet was viewed through the yellow glass, scarcely any light entered
the eye, but if a paper washed with some fluorescent liquid were laid on
the tablet it appeared brilliantly luminous. Different pairs of
complementary absorbents were required according to the colour of the
fluorescent light. This experiment shows clearly that the light which
passed through the first absorbent and which would have been stopped by
the second gave rise in the fluorescent substance to rays of a different
wave-length which were transmitted by the second absorbent. Scattered
light, with which the true fluorescent light was often associated, was
eliminated by this method, being stopped by the second absorbent.
[Illustration: FIG. 3.--Spectrum of Chlorophyll.]
[Illustration: FIG. 4.--Spectrum of Aesculin.]
Stokes also used a method, analogous to Newton's method of crossed
prisms, for the purpose of analysing the fluorescent light. A spectrum
was produced by means of a slit and a prism, the slit being horizontal
instead of vertical. The resulting very narrow spectrum was projected on
a white paper moistened with a fluorescent solution, and viewed through
a second prism with its refracting edge perpendicular to that of the
first prism. In addition to the sloping spectrum seen under ordinary
circumstances, another spectrum due to the fluorescent light alone, made
its appearance, as seen in figs. 3 and 4. In this spectrum the colours
do not run from left to right, but in horizontal lines. Thus the dark
lines of the solar spectrum lie across the colours. The spectra in figs.
3 and 4 were obtained by V. Pierre with an improved arrangement of
Stokes's method. It will be seen that, in the case of chlorophyll, the
whole spectrum, far into the ultra-violet, gives rise to a short range
of red fluorescent light, while the effective part of the exciting light
in the case of aesculin (a glucoside occurring in horse-chestnut bark)
begins a little above the fixed line G and the fluorescent light covers
a wide range extending from orange to blue.
Besides the substances already mentioned, a large number of vegetable
extracts and some inorganic bodies are strongly fluorescent. Stokes
found that most organic substances show signs of fluorescence. Green
fluor-spar from Alston Moor exhibits a violet, uranium glass a
yellowish-green fluorescence. Tincture of turmeric gives rise to a
greenish light, and the extract of seeds of _Datura stramonium_ a pale
green light. Ordinary paraffin oil fluoresces blue. Barium
platinocyanide, which is much used in the fluorescent screens employed
in work with the Rontgen rays, shows a brilliant green fluorescence with
ordinary light. Crystals of magnesium platinocyanide possess the
remarkable property of emitting a polarized fluorescent light, the
colour and plane of polarization depending on the position of the
crystal with respect to the incident beam, and, if polarized light is
used, on the plane of polarization of the latter.
_Stokes's Law._--In all the substances examined by Stokes, the
fluorescent light appeared to be of lower refrangibility than the light
which excited it. Stokes considered it probable that this lowering of
the refrangibility of the light was a general law which held for all
substances. This is known as Stokes's law. It has been shown, however,
by E. Lommel and others, that this law does not hold generally. Lommel
distinguishes two kinds of fluorescence. The bodies which exhibit the
first kind are those which possess strong absorption bands, of which
only one remains appreciable after great dilution. These bodies are
always strongly coloured and show anomalous dispersion and (in solids)
surface colour. In such cases, the maximum of intensity in the
fluorescent spectrum corresponds to the maximum of absorption. Stokes's
law is not obeyed, for a fluorescent spectrum can be produced by means
of homogeneous light of lower refrangibility than a great part of the
fluorescent light. The second kind of fluorescence is the most common,
and is exhibited by bodies which show absorption only in the upper part
of the spectrum, i.e. they are usually yellow or brown or (if the
absorption is in the ultra-violet) colourless. The absorption bands also
are different from those of substances of the first kind, for they
readily disappear on dilution. A third class of bodies is formed by
those substances which exhibit both kinds of fluorescence.
_Nature of Fluorescence._--No complete theory of fluorescence has yet
been given, though various attempts have been made to explain the
phenomenon. Fluorescence is closely allied to phosphorescence (q.v.),
the difference consisting in the duration of the effect after the
exciting cause is removed. Liquids which fluoresce only do so while the
exciting light is falling on them, ceasing immediately the exciting
light is cut off. In the case of solids, on the other hand, such as
fluor-spar or uranium glass, the effect, though very brief, does not die
away quite instantaneously, so that it is really a very brief
phosphorescence. The property of phosphorescence has been generally
attributed to some molecular change taking place in the bodies
possessing it. That some such change takes place during fluorescence is
rendered probable by the fact that the property depends upon the state
of the sensitive substance; some bodies, such as barium platinocyanide,
fluorescing in the solid state but not in solution, while others, such
as fluorescein, only fluoresce in solution. Fluorescence is always
associated with absorption, but many bodies are absorbent without
showing fluorescence. A satisfactory theory would have to account for
these facts as well as for the production of waves of one period by
those of another, and the non-homogeneous character of the fluorescent
light. Quite recently W. Voigt has sought to give a theory of
fluorescence depending on the theory of electrons. Briefly, this theory
assumes that the electrons which constitute the molecule of the
sensitive body can exist in two or more different configurations
simultaneously, and that these are in dynamical equilibrium, like the
molecule in a partially dissociated gas. If the electrons have different
periods of vibration in the different configurations, then it would
happen that the electrons whose period nearly corresponded with that of
the incident light would absorb the energy of the latter, and if they
then underwent a transformation into a different configuration with a
different period, this absorbed energy would be given out in waves of a
period corresponding to that of the new configuration.
_Applications of Fluorescence._--The phenomenon of fluorescence can be
utilized for the purpose of illustrating the laws of reflection and
refraction in lecture experiments since the path of a ray of light
through a very dilute solution of a sensitive substance is rendered
visible. The existence of the dark lines in the ultra-violet portion of
the solar spectrum can also be demonstrated in a simple manner. In
addition to the foregoing applications, Stokes made use of this property
for studying the character of the ultra-violet spectrum of different
sources of illumination and flames. He suggested also that the property
would in some cases furnish a simple test for the presence of a small
quantity of a sensitive substance in an organic mixture. Fluorescent
screens are largely used in work with Rontgen rays. There appears to be
some prospect of light being thrown on the question of molecular
structure by experiments on the fluorescence of vapours. Some very
interesting experiments in this direction have been performed by R.W.
Wood on the fluorescence of sodium vapour.
REFERENCES.--Sir G.G. Stokes, _Mathematical and Physical Papers_,
vols. iii. and iv.; Muller-Pouillet, _Lehrbuch der Physik_, Bd. ii.
(1897); A. Wullner, _Lehrbuch der Experimentalphysik_, Bd. iv. (1899);
A.A. Winkelmann, _Handbuch der Physik_, Bd. vi. (1906); R.W. Wood,
_Physical Optics_ (1905). (J. R. C.)
FLUORINE (symbol F, atomic weight 19), a chemical element of the halogen
group. It is never found in the uncombined condition, but in combination
with calcium as fluor-spar CaF2 it is widely distributed; it is also
found in cryolite Na3AlF6, in fluor-apatite, CaF2.3Ca3P2O8, and in
minute traces in sea-water, in some mineral springs, and as a
constituent of the enamel of the teeth. It was first isolated by H.
Moissan in 1886 by the electrolysis of pure anhydrous hydrofluoric acid
containing dissolved potassium fluoride. The U-shaped electrolytic
vessel and the electrodes are made of an alloy of platinum-iridium, the
limbs of the tube being closed by stoppers made of fluor-spar, and
fitted with two lateral exit tubes for carrying off the gases evolved.
Whilst the electrolysis is proceeding, the apparatus is kept at a
constant temperature of -23 deg. C. by means of liquid methyl chloride.
The fluorine, which is liberated as a gas at the anode, is passed
through a well cooled platinum vessel, in order to free it from any acid
fumes that may be carried over, and finally through two platinum tubes
containing sodium fluoride to remove the last traces of hydrofluoric
acid; it is then collected in a platinum tube closed with fluor-spar
plates. B. Brauner (_Jour. Chem. Soc._, 1894, 65, p. 393) obtained
fluorine by heating potassium fluorplumbate 3KF.HF.PbF4. At 200 deg. C.
this salt decomposes, giving off hydrofluoric acid, and between 230-250
deg. C. fluorine is liberated.
Fluorine is a pale greenish-yellow gas with a very sharp smell; its
specific gravity is 1.265 (H. Moissan); it has been liquefied, the
liquid also being of a yellow colour and boiling at -187 deg. C. It is
the most active of all the chemical elements; in contact with hydrogen
combination takes place between the two gases with explosive violence,
even in the dark, and at as low a temperature as -210 deg. C; finely
divided carbon burns in the gas, forming carbon tetrafluoride; water is
decomposed even at ordinary temperatures, with the formation of
hydrofluoric acid and "ozonised" oxygen; iodine, sulphur and phosphorus
melt and then inflame in the gas; it liberates chlorine from chlorides,
and combines with most metals instantaneously to form fluorides; it does
not, however, combine with oxygen. Organic compounds are rapidly
attacked by the gas.
Only one compound of hydrogen and fluorine is known, namely
_hydrofluoric acid_, HF or H2F2, which was first obtained by C. Scheele
in 1771 by decomposing fluor-spar with concentrated sulphuric acid, a
method still used for the commercial preparation of the aqueous solution
of the acid, the mixture being distilled from leaden retorts and the
acid stored in leaden or gutta-percha bottles. The perfectly anhydrous
acid is a very volatile colourless liquid and is best obtained,
according to G. Gore (_Phil. Trans._, 1869, p. 173) by decomposing the
double fluoride of hydrogen and potassium, at a red heat in a platinum
retort fitted with a platinum condenser surrounded by a freezing
mixture, and having a platinum receiver luted on. It can also be
prepared in the anhydrous condition by passing a current of hydrogen
over dry silver fluoride. The pure acid thus obtained is a most
dangerous substance to handle, its vapour even when highly diluted with
air having an exceedingly injurious action on the respiratory organs,
whilst inhalation of the pure vapour is followed by death. The anhydrous
acid boils at 19.5 deg. C. (H. Moissan), and on cooling, sets to a solid
mass at -102.5 deg. C, which melts at -92.3 deg. C. (K. Olszewski,
_Monats. fur Chemie_, 1886, 7, p. 371). Potassium and sodium readily
dissolve in the anhydrous acid with evolution of hydrogen and formation
of fluorides. The aqueous solution is strongly acid to litmus and
dissolves most metals directly. Its most important property is that it
rapidly attacks glass, reacting with the silica of the glass to form
gaseous silicon fluoride, and consequently it is used for etching. T.E.
Thorpe (_Jour. Chem. Soc._, 1889, 55, p. 163) determined the vapour
density of hydrofluoric acid at different temperatures, and showed that
there is no approach to a definite value below about 88 deg. C. where it
reaches the value 10.29 corresponding to the molecular formula HF; at
temperatures below 88 deg. C. the value increases rapidly, showing that
the molecule is more complex in its structure. (For references see J.N.
Friend, _The Theory of Valency_ (1909), p. 111.) The aqueous solution
behaves on concentration similarly to the other halogen acids; E.
Deussen (_Zeit. anorg. Chem._, 1905, 44, pp. 300, 408; 1906, 49, p. 297)
found the solution of constant boiling point to contain 43.2% HF and to
boil at 110 deg. (750 mm.).
The salts of hydrofluoric acid are known as _fluorides_ and are easily
obtained by the action of the acid on metals or their oxides,
hydroxides or carbonates. The fluorides of the alkali metals, of
silver, and of most of the heavy metals are soluble in water; those of
the alkaline earths are insoluble. A characteristic property of the
alkaline fluorides is their power of combining with a molecule of
hydrofluoric acid and with the fluorides of the more electro-negative
elements to form double fluorides, a behaviour not shown by other
metallic halides. Fluorides can be readily detected by their power of
etching glass when warmed with sulphuric acid; or by warming them in a
glass tube with concentrated sulphuric acid and holding a moistened
glass rod in the mouth of the tube, the water apparently gelatinizes
owing to the decomposition of the silicon fluoride formed. The atomic
weight of fluorine has been determined by the conversion of calcium,
sodium and potassium fluorides into the corresponding sulphates. J.
Berzelius, by converting silver fluoride into silver chloride,
obtained the value 19.44, and by analysing calcium fluoride the value
19.16; the more recent work of H. Moissan gives the value 19.05.
See H. Moissan, _Le Fluor et ses composes_ (Paris, 1900).
FLUOR-SPAR, native calcium fluoride (CaF2), known also as FLUORITE or
simply FLUOR. In France it is called fluorine, whilst the term fluor is
applied to the element (F). All these terms, from the Lat. _fluere_, "to
flow," recall the fact that the spar is useful as a flux in certain
metallurgical operations. (Cf. its Ger. name _Flussspat_ or _Fluss_.)
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
Fluor-spar crystallizes in the cubic system, commonly in cubes, either
alone or combined with the octahedron, rhombic dodecahedron, four-faced
cube, &c. The four-faced cube has been called the fluoroid. In fig. 1, a
is the cube (100), d the rhombic dodecahedron (110), and f the
four-faced cube (310). Fig. 2 shows a characteristic twin of
interpenetrant cubes. The crystals are sometimes polysynthetic, a large
octahedron, e.g., being built up of small cubes. The faces are often
etched or corroded. Cleavage is nearly always perfect, parallel to the
octahedron.
Fluor-spar has a hardness of 4, so that it is scratched by a knife,
though not so readily as calcite. Its specific gravity is about 3.2. The
colour is very variable, and often beautiful, but the mineral is too
soft for personal decoration, though it forms a handsome material for
vases, &c. In some fluor-spar the colour is disposed in bands, regularly
following the contour of the crystal. As the colour is usually expelled,
or much altered, by heat, it is believed to be due to an organic
pigment, and the presence of hydrocarbons has been detected in many
specimens by G. Wyrouboff, and other observers. H.W. Morse (_Proc. Amer.
Acad._, 1906, p. 587) obtained carbon monoxide and dioxide, hydrogen
and nitrogen and small quantities of oxygen from Weardale specimens by
heating. He concluded that the gases are due to the decomposition of an
organic colouring matter, which has, however, no connexion with the
fluorescence or thermo-luminescence of the mineral. Certain crystals
from Cumberland are beautifully fluorescent, appearing purple with a
bluish internal haziness by reflected light, and greenish by transmitted
light. Fluor-spar, though cubic, sometimes exhibits weak double
refraction, probably due to internal tension. Many kinds of fluor-spar
are thermo-luminescent, i.e. they glow on exposure to a moderate heat,
and the name of chlorophane has been given to a variety which exhibits a
green glow. The mineral also phosphoresces under the Rontgen rays.
Cavities containing liquid occasionally occur in crystals of fluor-spar,
notably in the greasy green cubes of Weardale in Durham. A dark violet
fluor-spar from Wolsendorf in Bavaria, evolves an odour of ozone when
struck, and has been called antozonite. Ozone is also emitted by a
violet fluor-spar from Quincie, dep. Rhone, France. In both cases the
spar evolves free fluorine, which ozonizes the air.
Fluor-spar is largely employed by the metallurgist, especially in
lead-smelting, and in the production of ferro-silicon and
ferro-manganese. It is also used in iron and brass foundries, and has
been found useful as a flux for certain gold-ores and in the reduction
of aluminium. It is used as a source of hydrofluoric acid, which it
evolves when heated with sulphuric acid. The mineral is also used in the
production of opal glass and enamel ware. In consequence of its low
refractive and dispersive power, colourless pellucid fluor-spar is
valuable in the construction of apochromatic lenses, but this variety is
rare. The dark violet fluor-spar of Derbyshire, known locally as "Blue
John," is prized for ornamental purposes. It occurs almost exclusively
at Tray Cliff, near Castleton. The dark purple spar, called by the
workmen "bull beef," may be changed, by heat, to a rich amethystine
tint. Being very brittle, the spar is rather difficult to work on the
lathe, and is often toughened by means of resin. F. Corsi, the eminent
Italian antiquary, held that fluor-spar was the material of the famous
murrhine vases.
Fluor-spar is a mineral of very wide distribution. Some of the finest
crystals occur in the lead-veins of the Carboniferous Limestone series
in the north of England, especially at Weardale, Allendale and Alston
Moor. It is also found in the lead and copper-mines of Cornwall and S.
Devon, notably near Liskeard, where fine crystals have been found, with
faces of the six-faced octahedron replacing the corners of the cube. In
Cornwall fluor-spar is known to the miners as "cann." Fine yellow
fluor-spar occurs in some of the Saxon mines, and beautiful rose-red
octahedra are found in the Alps, near Goschenen. Many localities in the
United States yield fluor-spar, and it is worked commercially in a few
places, notably at Rosiclare in southern Illinois.
FLUSHING, formerly a township and a village of Queens county, New York,
U.S.A., on Long Island, at the head of Flushing Bay, since the 1st of
January 1898 a part of the borough of Queens, New York City. Flushing is
served by the Long Island railroad and by electric lines. It was settled
in 1644 by a company of English non-conformists who had probably been
residents of Flushing in Holland, from which the new place took its
name. Subsequently a large number of Quakers settled here, and in 1672
George Fox spent some time in the township. Before the War of
Independence Flushing was the country-seat of many rich New Yorkers and
colonial officials.
FLUSHING (Dutch _Vlissingen_), a fortified seaport in the province of
Zeeland, Holland, on the south side of the island of Walcheren, at the
mouth of the estuary of the western Scheldt, 4 m. by rail S. by W. of
Middelburg, with which it is also connected by steam tramway and by a
ship canal. There is a steam ferry to Breskens and Ter Neuzen on the
coast of Zeeland-Flandres. Pop. (1900) 18,893. An important naval
station and fortress up to 1867, Flushing has since aspired, under the
care of the Dutch government, to become a great commercial port. In 1872
the railway was opened which, in conjunction with the regular day and
night service of steamers to Queenborough in the county of Kent, forms
one of the main routes between England and the east of Europe. In 1873
the great harbour, docks and canal works were completed. Yet the
navigation of the port remains far behind that of Rotterdam or Antwerp,
the tonnage being in 1899 about 7.9% of that of the kingdom. As a summer
resort, however, Flushing has acquired considerable popularity,
sea-baths and a large modern hotel being situated on the fine beach
about three-quarters of a mile north-west of the town. It possesses a
town hall, containing a collection of local antiquities, a theatre, an
exchange, an academy of sciences and a school of navigation. The
Jakobskerk, or Jacob's church, founded in 1328, contains monuments to
Admiral de Ruyter (1607-1676) and the poet Jacob Bellamy (1757-1786),
who were natives of Flushing. The chief industries of the town are
connected with the considerable manufacture of machinery, the state
railway-workshops, shipbuilding yards, Krupp iron and steel works'
depot, brewing, and oil and soap manufacture. The chief imports are
colonial produce and wine, wood and coal. The exports include
agricultural produce (wheat and beans), shrimps and meat.
FLUTE, a word adapted from O. Fr. _fleute_, modern _flute_; from O. Fr.
have come the Span. _flauta_, Ital. _flauto_ and Ger. _Flote_. The _New
English Dictionary_ dismisses the derivations suggested from Lat.
_flatuare_ or _flavitare_; ultimately the word must be referred to the
root seen in "blow," Lat. _flare_, Ger. _blasen_, &c.
1. In music "flute" is a general term applied to wood-wind instruments
consisting of a pipe pierced with lateral holes and blown directly
through the mouthpiece without the intervention of a reed. The flute
family is classified according to the mouthpiece used to set in
vibration the column of air within the tube: i.e. (1) the simple lateral
mouth-hole or embouchure which necessitates holding the instrument in a
transverse position; (2) the whistle or fipple mouthpiece which allows
the performer to hold the instrument vertically in front of him. There
is a third class of pipes included among the flutes, having no
mouthpiece of any sort, in which the column of air is set in vibration
by blowing obliquely across the open end of the pipe, as in the ancient
Egyptian nay, and the pan-pipe or syrinx (q.v.). The transverse flute
has entirely superseded the whistle flute, which has survived only in
the so-called penny whistle, in the "flute-work" of the organ (q.v.),
and in the French flageolet.
_The Transverse Flute_ or _German Flute_ (Fr. _flute traversiere_,
_flute allemande_: Ger. _Flote_, _Querflote_, _Zwerchpfeiff_,
_Schweitzerpfeiff_; Ital. _flauto traverso_) includes the _concert
flute_ known both as flute in C and as flute in D, the piccolo (q.v.) or
octave flute, and the fife (q.v.). The modern flute consists of a tube
open at one end and nominally closed at the other by means of a plug or
cork stopper: virtually, however, the tube is an open one giving the
consecutive harmonic series of the open pipe or of a stretched string.
The primitive flute was made in one piece, but the modern instrument is
composed of three adjustable joints. (1) The head-joint, plugged at the
upper end and containing at about one-third of the length the mouth-hole
or embouchure. This embouchure, always open when the instrument is being
played, converts the closed tube into an open one, in an acoustical
sense. (2) The body, containing the holes and keys necessary to produce
the scale which gave the flute its original designation of D flute, the
head and body together, when the holes are closed, giving the
fundamental note D. Before the invention of keys, this fundamental note
and the notes obtained by the successive opening of the six holes
produced the diatonic scale of D major. All other semitones were
obtained by what is known as cross fingering (Fr. _doigte fourchu_; Ger.
_Gabelgriffe_). It became usual to consider this the typical fingering
nomenclature, whatever the fundamental note given out by the flute, and
to indicate the tonality by the note given out when the six lateral
holes are covered by the fingers. The result is that the tonality is
always a tone lower than the name of the instrument indicates. Thus the
D flute is really in C, the F flute is E[flat], &c. (3) The foot-joint
or tail-joint containing the two additional keys for C[sharp] and C
which extend the compass downwards, completing the chromatic scale of C
in the fundamental octave.
The compass of the modern flute is three octaves with chromatic
semitones from [notes] to [notes]. The sound is produced by holding the
flute transversely with the embouchure turned slightly outwards, the
lower lip resting on the nearer edge of the embouchure, and blowing
obliquely across, not into, the orifice. The flat stream of air from the
lips, known as the air-reed, breaks against the sharp outer edge of the
embouchure. The current of air, thus set in a flutter, produces in the
stationary column of air within the tube a series of pulsations or
vibrations caused by the alternate compression and rarefaction of the
air and generating sounds of a pitch proportional to the length of the
stationary column, which is practically somewhat longer than the length
of the tube.[1] The length of this column is varied by opening the
lateral finger-holes. The current or air-reed thus acts upon the air
column within the flute, without passing through the tube, as a plectrum
upon a string, setting it in vibration. The air column of the flute is
the sound-producer, whereas in instruments with reed mouthpieces the
vibrating reed is more properly the sound-producer, while the air
column, acting as a resonating medium, reinforces the note of the reed
by vibrating synchronously with it. If the angle[2] at which the current
of air is directed against the outer edge of the embouchure be made less
acute and the pressure of the breath be at the same time increased, the
frequency of the alternate pulses of compression and rarefaction within
the tube will be increased two, three or fourfold, forming a
corresponding number of nodes and loops which results in harmonics or
upper partials, respectively the octave, the twelfth, the double octave.
By this means sounds of higher pitch are produced without actually
shortening the length of the column of air by means of lateral holes.
The acoustic theory of sound-production in the flute is one on which
there is great diversity of opinion. The subject is too vast to be
treated here, but readers who wish to pursue it may consult the works of
Rockstro,[3] Helmholtz,[4] and others.[5] The effect of boring lateral
holes in pipes is to shorten the vibrating length of the air column,
which may be regarded as being effective only between the hole in
question and the mouthpiece. In order to obtain this result the diameter
of the hole should be equal to that of the bore; as long as the holes
were covered by the fingers, this was obviously impossible. The holes,
therefore, being smaller than the laws of acoustics demand, have to be
placed proportionally nearer the mouthpiece in order to avoid deepening
the pitch and deadening the tone. This principle was understood by
wind-instrument makers of classic Greece (see AULOS and CLARINET), and
has been explained by Chladni[6] and Gottfried Weber.[7]
The bore of the early flute with six finger-holes was invariably
cylindrical throughout, but towards the end of the 17th century a
modification took place, the head joint alone remaining cylindrical
while the rest of the bore assumed the form of a cone having its
smallest diameter at the open end of the tube. The conoidal bore
greatly improved the quality of tone and the production of the higher
harmonics of the third octave. Once the conical bore had been adopted,
the term flute was exclusively applied to the new instruments, the
smaller flutes, then cylindrical, used in the army being designated fife
(q.v.). At the present day in England, France and America, the favourite
mode of construction is that introduced by Theobald Boehm, and known as
the "cylinder flute with the parabolic head," of which more will be said
further on. The successive opening of the holes and keys on the flute
produces the chromatic scale of the first or fundamental octave. By
increasing the pressure of the breath and slightly altering the position
of the lips over the mouth-hole, the same fingering produces the notes
of the fundamental octave in the next octave higher. The third octave of
the compass is obtained by the production of the higher harmonics (Fr.
_sons harmoniques_; Ger. _Flageolettone_), of the fundamental scale,
facilitated by the opening of certain of the finger-holes as "vent
holes." The quality of tone depends somewhat on the material of which
the flute is made; silver and gold produce a liquid tone of exquisite
delicacy suitable for solo music, cocus-wood and ebonite a rich mellow
tone of considerable power suitable for orchestral music. The tone
differs further in the three registers, the lowest being slightly rough,
the medium sweet and elegiac, and the third bird-like and brilliant. The
proportions, position and form of the stopper and of the air chamber
situated between it and the embouchure are mainly influential in giving
the flute its peculiar slightly hollow timbre, due to the paucity of the
upper partials of which according to Helmholtz[8] only the octave and
twelfth are heard. Mr Blaikley[9] states, however, that when the
fundamental D is played, he can discern the seventh partial. The
technical capabilities of the flute are practically unlimited to a good
player who can obtain sustained notes diminuendo and crescendo, diatonic
and chromatic scales and arpeggios both legato and staccato, leaps,
turns, shakes, &c. By the articulation with the tongue of the syllables
_te-ke_ or _ti-ke_ repeated quickly for groups of double notes, or of
_te-ke-ti_ for triplets, an easy effective staccato is produced, known
respectively as _double_ or _triple tonguing_, a device understood early
in the 16th century and mentioned by Martin Agricola,[10] who gives the
syllables as _de_ for sustained notes, di-ri for shorter notes, and
_tel-lel-lel_ for staccato passages in quick tempo.[11]
[Illustration: From Captain Day's _Catalogue, &c._, by permission of
Messrs. Eyre & Spottiswoode.