FLEURY, CLAUDE FLYGARE-CARLEN, EMILIE
FLIEDNER, THEODOR FLYING BUTTRESS
FLIGHT and FLYING FLYING COLUMN
FLINCK, GOVERT "FLYING DUTCHMAN,"
FLINDERS, MATTHEW FLYING-FISH
FLINSBERG FLYING-FOX
FLINT, AUSTIN FLYING-SQUIRREL
FLINT, ROBERT FLYSCH
FLINT, TIMOTHY FOCA
FLINT (Michigan, U.S.A.) FOCHABERS
FLINT (county of North Wales) FOCSHANI
FLINT (town of North Wales) FOCUS
FLINT (crystalline substance) FOG
FLINT IMPLEMENTS AND WEAPONS FOGAZZARO, ANTONIO
FLOAT FOGELBERG, BENEDICT ERLAND
FLOCK FOGGIA
FLODDEN FOHN
FLODOARD FOHR
FLOE FOIL
FLOOD, HENRY FOIL-FENCING
FLOOD FOIX, PAUL DE
FLOOD PLAIN FOIX
FLOOR FOLARD, JEAN CHARLES
FLOORCLOTH FOLD
FLOQUET, CHARLES THOMAS FOLENGO, TEOFILO
FLOR, ROGER DI FOLEY, JOHN HENRY
FLORA FOLEY, SIR THOMAS
FLORE AND BLANCHEFLEUR FOLI, ALLAN JAMES
FLORENCE, WILLIAM JERMYN FOLIGNO
FLORENCE OF WORCESTER FOLIO
FLORENCE (Alabama, U.S.A.) FOLIUM
FLORENCE (capital of Tuscany) FOLKES, MARTIN
FLORES (Atlantic Ocean island) FOLKESTONE
FLORES (East Indies island) FOLKLAND
FLOREZ, ENRIQUE FOLKLORE
FLORIAN, SAINT FOLLEN, AUGUST LUDWIG
FLORIAN, JEAN PIERRE CLARIS DE FOLLEN, KARL
FLORIANOPOLIS FOLLETT, SIR WILLIAM WEBB
FLORIDA FONBLANQUE, ALBANY WILLIAM
FLORIDABLANCA, DON JOSE FOND DU LAC
FLORIDOR FONDI
FLORIN FONNI
FLORIO, GIOVANNI FONSAGRADA
FLORIS, FRANS FONSECA, MANOEL DEODORO DA
FLORUS FONSECA, BAY OF
FLORUS, JULIUS FONT
FLORUS, PUBLIUS ANNIUS FONTAINE, PIERRE FRANCOIS LEONARD
FLOTOW, FRIEDRICH ADOLF VON FONTAINEBLEAU
FLOTSAM, JETSAM and LIGAN FONTAN, LOUIS MARIE
FLOUNDER FONTANA, DOMENICO
FLOUR and FLOUR MANUFACTURE FONTANA, LAVINIA
FLOURENS, GUSTAVE FONTANA, PROSPERO
FLOURENS, MARIE JEAN PIERRE FONTANE, THEODOR
FLOWER, SIR WILLIAM HENRY FONTANES, LOUIS
FLOWER FONTENAY-LE-COMTE
FLOWERS, ARTIFICIAL FONTENELLE, BERNARD LE BOVIER DE
FLOYD, JOHN FONTENOY
FLOYD, JOHN BUCHANAN FONTEVRAULT
FLOYER, SIR JOHN FOOD
FLUDD, ROBERT FOOD PRESERVATION
FLUGEL, GUSTAV LEBERECHT FOOL
FLUGEL, JOHANN GOTTFRIED FOOLS, FEAST OF
FLUKE FOOLSCAP
FLUME FOOL'S PARSLEY
FLUMINI MAGGIORE FOOT
FLUORANTHENE FOOT-AND-MOUTH DISEASE
FLUORENE FOOTBALL
FLUORESCEIN FOOTE, ANDREW HULL
FLUORESCENCE FOOTE, MARY HALLOCK
FLUORINE FOOTE, SAMUEL
FLUOR-SPAR FOOTMAN
FLUSHING (New York, U.S.A.) FOOTSCRAY
FLUSHING (Zeeland, Holland) FOOT-STALL
FLUTE FOPPA, VINCENZO
FLUX FORAGE
FLY FORAIN, J. L.
FLYCATCHER FORAKER, JOSEPH HENSON
FLEURY, CLAUDE (1640-1723), French ecclesiastical historian, was born at
Paris on the 6th of December 1640. Destined for the bar, he was educated
at the aristocratic college of Clermont (now that of Louis-le-Grand). In
1658 he was nominated an advocate to the parlement of Paris, and for
nine years followed the legal profession. But he had long been of a
religious disposition, and in 1667 turned from law to theology. He had
been some time in orders when Louis XIV., in 1672, selected him as tutor
of the princes of Conti, with such success that the king next entrusted
to him the education of the count of Vermandois, one of his natural
sons, on whose death in 1683 Fleury received for his services the
Cistercian abbey of Loc-Dieu, in the diocese of Rhodez. In 1689 he was
appointed sub-preceptor of the dukes of Burgundy, of Anjou, and of
Berry, and thus became intimately associated with Fenelon, their chief
tutor. In 1696 he was elected to fill the place of La Bruyere in the
French Academy; and on the completion of the education of the young
princes the king bestowed upon him the rich priory of Argenteuil, in the
diocese of Paris (1706). On assuming this benefice he resigned, with
rare disinterestedness, that of the abbey of Loc-Dieu. About this time
he began his great work, the first of the kind in France, and one for
which he had been collecting materials for thirty years--the _Histoire
ecclesiastique_. Fleury's evident intention was to write a history of
the church for all classes of society; but at the time in which his
great work appeared it was less religion than theology that absorbed the
attention of the clergy and the educated public; and his work
accordingly appealed to the student rather than to the popular reader,
dwelling as it does very particularly on questions of doctrine, of
discipline, of supremacy, and of rivalry between the priesthood and the
imperial power. Nevertheless it had a great success. The first edition,
printed at Paris in 20 volumes 4to, 1691, was followed by many others,
among which may be mentioned that of Brussels, in 32 vols. 8vo, 1692,
and that of Nismes, in 25 vols. 8vo, 1778 to 1780. The work of Fleury
only comes down to the year 1414. It was continued by J. Claude Fabre
and Goujet down to 1595, in 16 vols. 4to. In consulting the work of
Fleury and its supplement, the general table of contents, published by
Rondel, Paris, 1758, 1 vol. 4to, will be found very useful. Translations
have been made of the entire work into Latin, German and Italian. The
Latin translation, published at Augsburg, 1758-1759, 85 vols. 8vo,
carries the work down to 1684. Fleury, who had been appointed confessor
to the young king Louis XV. in 1716, because, as the duke of Orleans
said, he was neither Jansenist nor Molinist, nor Ultramontanist, but
Catholic, died on the 14th of July 1723. His great learning was equalled
by the modest simplicity of his life and the uprightness of his conduct.
Fleury left many works besides his _Histoire ecclesiastique_. The
following deserve special mention:--_Histoire du droit francois_
(1674, 12mo); _Moeurs des Israelites_ (1681, 12mo); _Moeurs des
Chretiens_ (1682, 12mo); _Traite du choix et de la methode des etudes_
(1686, 2 vols. 12mo); _Les Devoirs des maitres et des domestiques_
(1688, 12mo). A number of the smaller works were published in one
volume at Paris in 1807. The Roman Congregation of the Index condemned
his _Catechisme historique_ (1679) and the _Institution du droit
ecclesiastique_ (1687).
See C. Ernst Simonetti, _Der Character eines Geschichtsschreibers in
dem Leben und aus den Schriften des Abts C. Fleury_ (Gottingen, 1746,
4to); C.F.P. Jaeger, _Notice sur C. Fleury, considere comme historien
de l'eglise_ (Strassburg, 1847, 8vo); Reichlin-Meldegg, _Geschichte
des Christentums, i._
FLIEDNER, THEODOR (1800-1864), German Protestant divine, was born on the
21st of January 1800 at Epstein (near Wiesbaden), the small village in
which his father was pastor. He studied theology at the universities of
Giessen and Gottingen, and at the theological seminary of Herborn, and
at the age of twenty he passed his final examination. After a year spent
in teaching and preaching, in 1821 he accepted a call from the
Protestant church at Kaiserswerth, a little town on the Rhine, a few
miles below Dusseldorf. To help his people and to provide an endowment
for his church, he undertook journeys in 1822 through part of Germany,
and then in 1823 to Holland and England. He met with considerable
success, and had opportunities of observing what was being done towards
prison reform; in England he made the acquaintance of the philanthropist
Elizabeth Fry. The German prisons were then in a very bad state. The
prisoners were huddled together in dirty rooms, badly fed, and left in
complete idleness. No one dreamed of instructing them, or of collecting
statistics to form the basis of useful legislation on the subject.
Fliedner, at first singly, undertook the work. He applied for permission
to be imprisoned for some time, in order that he might look at prison
life from the inside. This petition was refused, but he was allowed to
hold fortnightly services in the Dusseldorf prison, and to visit the
inmates individually. Those interested in the subject banded themselves
together, and on the 18th of June 1826 the first Prison Society of
Germany (_Rheinisch-Westfalischer Gefangnisverein_) was founded. In 1833
Fliedner opened in his own parsonage garden at Kaiserswerth a refuge for
discharged female convicts. His circle of practical philanthropy rapidly
increased. The state of the sick poor had for some time excited his
interest, and it seemed to him that hospitals might be best served by an
organized body of specially trained women. Accordingly in 1836 he began
the first deaconess house, and the hospital at Kaiserswerth. By their
ordination vows the deaconesses devoted themselves to the care of the
poor, the sick and the young; but their engagements were not final--they
might leave their work and return to ordinary life if they chose. In
addition to these institutions Fliedner founded in 1835 an infant
school, then a normal school for infant school mistresses (1836), an
orphanage for orphan girls of the middle class (1842), and an asylum for
female lunatics (1847). Moreover, he assisted at the foundation and in
the management of similar institutions, not only in Germany, but in
various parts of Europe.
In 1849 he resigned his pastoral charge, and from 1849 to 1851 he
travelled over a large part of Europe, America and the East--the object
of his journeys being to found "mother houses," which were to be not
merely training schools for deaconesses, but also centres whence other
training establishments might arise. He established a deaconess house in
Jerusalem, and after his return assisted by counsel and money in the
erection of establishments at Constantinople, Smyrna, Alexandria and
Bucharest. Among his later efforts may be mentioned the Christian house
of refuge for female servants in Berlin (connected with which other
institutions soon arose) and the "house of evening rest" for retired
deaconesses at Kaiserswerth. In 1855 Fliedner received the degree of
doctor in theology from the university of Bonn, in recognition rather of
his practical activity than of his theological attainments. He died on
the 4th of October 1864, leaving behind him over 100 stations attended
by 430 deaconesses; and these by 1876 had increased to 150 with an
attendance of 600.
Fliedner's son FRITZ FLIEDNER (1845-1901), after studying in Halle and
Tubingen, became in 1870 chaplain to the embassy in Madrid. He followed
in his father's footsteps by founding several philanthropic institutions
in Spain. He was also the author of a number of books, amongst which was
an autobiography, _Aus meinem Leben. Erinnerungen und Erfahrungen_
(1901).
Theodor Fliedner's writings are almost entirely of a practical
character. He edited a periodical, _Der Armen und Kranken Freund,_
which contained information regarding the various institutions, and
also the yearly almanac of the Kaiserswerth institution. Besides
purely educational and devotional works, he wrote _Buch der Martyrer_
(1852); _Kurze Geschichte der Entstehung der ersten evang.
Liebesanstalten zu Kaiserswerth_ (1856); _Nachricht uber das
Diakonissen-Werk in der Christ. Kirche_ (5th ed., 1867); _Die evangel.
Martyrer Ungarns und Siebenburgens; and Beschreibung der Reise nach
Jerusalem und Constantinopel_. All were published at Kaiserswerth.
There is a translation of the German life by C. Winkworth (London,
1867). See also G. Fliedner, _Theodor Fliedner, kurzer Abriss seines
Lebens und Wirkens_ (3rd ed., 1892). See also on Fliedner and his work
_Kaiserswerth Deaconesses_ (London, 1857); Dean John S. Howson's
_Deaconesses_ (London, 1862); _The Service of the Poor_, by E.C.
Stephen (London, 1871); W.F. Stevenson's _Praying and Working_
(London, 1865).
FLIGHT and FLYING. Of the many scientific problems of modern times,
there are few possessing a wider or more enduring interest than that of
aerial navigation (see also AERONAUTICS). To fly has always been an
object of ambition with man; nor will this occasion surprise when we
remember the marvellous freedom enjoyed by volant as compared with
non-volant animals. The subject of aviation is admittedly one of extreme
difficulty. To tread upon the air (and this is what is really meant) is,
at first sight, in the highest degree utopian; and yet there are
thousands of living creatures which actually accomplish this feat. These
creatures, however varied in form and structure, all fly according to
one and the same principle; and this is a significant fact, as it tends
to show that the air must be attacked in a particular way to ensure
flight. It behoves us then at the outset to scrutinize very carefully
the general configuration of flying animals, and in particular the size,
shape and movements of their flying organs.
Flying animals differ entirely from sailing ships and from balloons,
with which they are not unfrequently though erroneously compared; and a
flying machine constructed upon proper principles can have nothing in
common with either of those creations. The ship floats upon water and
the balloon upon air; but the ship differs from the balloon, and the
ship and the balloon differ from the flying creature and flying machine.
The water and air, moreover, have characteristics of their own. The
analogies which connect the water with the air, the ship with the
balloon, and the ship and the balloon with the flying creature and
flying machine are false analogies. A sailing ship is supported by the
water and requires merely to be propelled; a flying creature and a
flying machine constructed on the living type require to be both
supported and propelled. This arises from the fact that water is much
denser than air, and because water supports on its surface substances
which fall through air. While water and air are both fluid media, they
are to be distinguished from each other in the following particulars.
Water is comparatively very heavy, inelastic and incompressible; air, on
the other hand, is comparatively very light, elastic and compressible.
If water be struck with violence, the recoil obtained is great when
compared with the recoil obtained from air similarly treated. In water
we get a maximum recoil with a minimum of displacement; in air, on the
contrary, we obtain a minimum recoil with a maximum of displacement.
Water and air when unconfined yield readily to pressure. They thus form
_movable fulcra_ to bodies acting upon them. In order to meet these
peculiarities the travelling organs of aquatic and flying animals
(whether they be feet, fins, flippers or wings) are made not of rigid
but of elastic materials. The travelling organs, moreover, increase in
size in proportion to the tenuity of the fluid to be acted upon. The
difference in size of the travelling organs of animals becomes very
marked when the land animals are contrasted with the aquatic, and the
aquatic with the aerial, as in figs. 1, 2 and 3.
The peculiarities of water and air as supporting media are well
illustrated by a reference to swimming, diving and flying birds. A bird
when swimming extends its feet simultaneously or alternately in a
backward direction, and so obtains a forward recoil. The water supports
the bird, and the feet simply propel. In this case the bird is lighter
than the water, and the long axis of the body is horizontal (a of fig.
4). When the bird dives, or flies under water, the long axis of the body
is inclined obliquely downwards and forwards, and the bird forces itself
into and beneath the water by the action of its feet, or wings, or both.
In diving or sub-aquatic flight the feet strike upwards and backwards,
the wings downwards and _backwards_ (b of fig. 4). In aerial flying
everything is reversed. The long axis of the bird is inclined obliquely
upwards and forwards, and the wings strike, not downwards and backwards,
but downwards and _forwards_ (c of fig. 4). These changes in the
direction of the long axis of the bird in swimming, diving and flying,
and in the direction of the stroke of the wings in sub-aquatic and
aerial flight, are due to the fact that the bird is heavier than the air
and lighter than the water.
[Illustration: FIG. 1.--Chillingham Bull (_Bos Scoticus_). Small
travelling extremities adapted for land. r, s, t, u, figure-of-8
described by the feet in walking.]
[Illustration: FIG. 2.--The Turtle (_Chelonia imbricata_). Enlarged
travelling extremities (flippers) adapted for water.]
[Illustration: FIG. 3.--The Bat (_Phyllocina gracilis_). Greatly
expanded travelling extremities adapted for air.]
[Illustration: FIG. 4.--The King Penguin in the positions assumed by a
bird in (a) swimming, (b) diving, and (c) flying.]
The physical properties of water and air explain in a great measure how
the sailing ship differs from the balloon, and how the latter differs
from the flying creature and flying machine constructed on the natural
type. The sailing ship is, as it were, immersed in two oceans, viz. an
ocean of water and an ocean of air--the former being greatly heavier and
denser than the latter. The ocean of water buoys or floats the ship, and
the ocean of air, or part of it in motion, swells the sails which propel
the ship. The moving air, which strikes the sails directly, strikes the
hull of the vessel indirectly and forces it through the water, which, as
explained, is a comparatively dense fluid. When the ship is in motion
it can be steered either by the sails alone, or by the rudder alone, or
by both combined. A balloon differs from a sailing ship in being
immersed in only one ocean, viz. the ocean of air. It resembles the ship
in floating upon the air, as the ship floats upon the water; in other
words, the balloon is lighter than the air, as the ship is lighter than
the water. But here all analogy ceases. The ship, in virtue of its being
immersed in two fluids having different densities, can be steered and
made to tack about in a horizontal plane in any given direction. This in
the case of the balloon, immersed in one fluid, is impossible. The
balloon in a calm can only rise and fall in a vertical line. Its
horizontal movements, which ought to be the more important, are
accidental movements due to air currents, and cannot be controlled; the
balloon, in short, cannot be guided. One might as well attempt to steer
a boat carried along by currents of water in the absence of oars, sails
and wind, as to steer a balloon carried along by currents of air. The
balloon has no hold upon the air, and this consequently cannot be
employed as a _fulcrum_ for regulating its course. The balloon, because
of its vast size and from its being lighter than the air, is completely
at the mercy of the wind. It forms an integral part, so to speak, of the
wind for the time being, and the direction of the wind in every instance
determines the horizontal motion of the balloon. The force required to
propel a balloon against even a moderate breeze would result in its
destruction. The balloon cannot be transferred with any degree of
certainty from one point of the earth's surface to another, and hence
the chief danger in its employment. It may, quite as likely as not,
carry its occupants out to sea. The balloon is a mere lifting machine
and is in no sense to be regarded as a flying machine. It resembles the
flying creature only in this, that it is immersed in the ocean of air in
which it sustains itself. The mode of suspension is wholly different.
The balloon floats because it is lighter than the air; the flying
creature floats because it extracts from the air, by the vigorous
downward action of its wings, a certain amount of upward recoil. The
balloon is passive; the flying creature is active. The balloon is
controlled by the wind; the flying creature controls the wind. The
balloon in the absence of wind can only rise and fall in a vertical
line; the flying creature can fly in a horizontal plane in any given
direction. The balloon is inefficient because of its levity; the flying
creature is efficient because of its weight.
Weight, however paradoxical it may appear, is necessary to flight.
Everything which flies is vastly heavier than the air. The inertia of
the mass of the flying creature enables it to control and direct its
movements in the air. Many are of opinion that flight is a mere matter
of levity and power. This is quite a mistake. No machine, however light
and powerful, will ever fly whose travelling surfaces are not properly
fashioned and properly applied to the air.
It was supposed at one time that the air sacs of birds contributed in
some mysterious way to flight, but this is now known to be erroneous.
The bats and some of the best-flying birds have no air sacs. Similar
remarks are to be made of the heated air imprisoned within the bones of
certain birds.[1] Feathers even are not necessary to flight. Insects and
bats have no feathers, and yet fly well. The only facts in natural
history which appear even indirectly to countenance the flotation theory
are the presence of a swimming bladder in some fishes, and the existence
of membranous expansions or pseudo-wings in certain animals, such as the
flying fish, flying dragon and flying squirrel. As, however, the animals
referred to do not actually fly, but merely dart into the air and there
sustain themselves for brief intervals, they afford no real support to
the theory. The so-called floating animals are depicted at figs. 5, 6
and 7.
[Illustration: FIG. 5.--The Red-throated Dragon (_Draco haematopogon_).]
[Illustration: FIG. 6.--The Flying Colugo (_Galeopithecus volans_); also
called flying lemur and flying squirrel.]
[Illustration: FIG. 7.--The Flying Fish (_Exocoetus exiliens_).]
It has been asserted, and with some degree of plausibility, that a fish
lighter than the water might swim, and that a bird lighter than the air
might fly: it ought, however, to be borne in mind that, in point of
fact, a fish lighter than the water could not hold its own if the water
were in the least perturbed, and that a bird lighter than the air would
be swept into space by even a moderate breeze without hope of return.
Weight and power are always associated in living animals, and the fact
that living animals are made heavier than the medium they are to
navigate may be regarded as a conclusive argument in favour of weight
being necessary alike to the swimming of the fish and the flying of the
bird. It may be stated once for all that flying creatures are for the
most part as heavy, bulk for bulk, as other animals, and that flight in
every instance is the product, not of superior levity, but of _weight_
and _power_ directed upon properly constructed flying organs.
This fact is important as bearing on the construction of flying
machines. It shows that a flying machine need not necessarily be a
light, airy structure exposing an immoderate amount of surface. On the
contrary, it favours the belief that it should be a compact and
moderately heavy and powerful structure, which trusts for elevation and
propulsion entirely to its flying appliances--whether actively moving
wings, or screws, or aeroplanes wedged forward by screws. It should
attack and subdue the air, and never give the air an opportunity of
attacking or subduing it. It should smite the air intelligently and as a
master, and its vigorous well-directed thrusts should in every instance
elicit an upward and forward recoil. The flying machine must be _multum
in parvo_. It must launch itself in the ocean of air, and must extract
from that air, by means of its travelling surfaces--however fashioned
and however applied--the recoil or resistance necessary to elevate and
carry it forward. Extensive inert surfaces indeed are contra-indicated
in a flying machine, as they approximate it to the balloon, which, as
has been shown, cannot maintain its position in the air if there are air
currents. A flying machine which could not face air currents would
necessarily be a failure. To obviate this difficulty we are forced to
fall back upon _weight_, or rather the structures and appliances which
weight represents. These appliances as indicated should not be
unnecessarily expanded, but when expanded they should, wherever
practicable, be converted into actively moving flying surfaces, in
preference to fixed or inert dead surfaces.
The question of surface is a very important one in aviation: it
naturally resolves itself into one of active and passive surface. As
there are active and passive surfaces in the flying animal, so there
are, or should be, active and passive surfaces in the flying machine.
Art should follow nature in this matter. The active surfaces in flying
creatures are always greatly in excess of the passive ones, from the
fact that the former virtually increase in proportion to the spaces
through which they are made to travel. Nature not only distinguishes
between active and passive surfaces in flying animals, but she strikes a
just balance between them, and utilizes both. She regulates the surfaces
to the strength and weight of the flying creature and the air currents
to which the surfaces are to be exposed and upon which they are to
operate. In her calculations she never forgets that her flying subjects
are to control and not to be controlled by the air. As a rule she
reduces the passive surfaces of the body to a minimum; she likewise
reduces as far as possible the actively moving or flying surfaces.
While, however, diminishing the surfaces of the flying animal as a
whole, she increases as occasion demands the active or wing surfaces by
wing movements, and the passive or dead surfaces by the forward motion
of the body in progressive flight. She knows that if the wings are
driven with sufficient rapidity they practically convert the spaces
through which they move into solid bases of support; she also knows that
the body in rapid flight derives support from all the air over which it
passes. The manner in which the wing surfaces are increased by the wing
movements will be readily understood from the accompanying illustrations
of the blow-fly with its wings at rest and in motion (figs. 8 and 9). In
fig. 8 the surfaces exposed by the body of the insect and the wings are,
as compared with those of fig. 9, trifling. The wing would have much
less purchase on fig. 8 than on fig. 9, provided the surfaces exposed by
the latter were passive or dead surfaces. But they are not dead
surfaces: they represent the spaces occupied by the rapidly vibrating
wings, which are actively moving flying organs. As, moreover, the wings
travel at a much higher speed than any wind that blows, they are
superior to and control the wind; they enable the insect to dart
through the wind in whatever direction it pleases.
The reader has only to imagine figs. 8 and 9 cut out in paper to realize
that extensive, inert, horizontal aeroplanes[2] in a flying machine
would be a mistake. It is found to be so practically, as will be shown
by and by. Fig. 9 so cut out would be heavier than fig. 8, and if both
were exposed to a current of air, fig. 9 would be more blown about than
fig. 8.
[Illustration: FIG. 8.--Blow-fly (_Musca vomitoria_) with its wings at
rest.]
[Illustration: FIG. 9.--Blow-fly with its wings in motion as in flight.]
It is true that in beetles and certain other insects there are the
elytra or wing cases--thin, light, horny structures inclined slightly
upwards--which in the act of flight are spread out and act as sustainers
or gliders. The elytra, however, are comparatively long narrow
structures which occupy a position in front of the wings, of which they
may be regarded as forming the anterior parts. The elytra are to the
delicate wings of some insects what the thick anterior margins are to
stronger wings. The elytra, moreover, are not wholly passive structures.
They can be moved, and the angles made by their under surfaces with the
horizon adjusted. Finally, they are not essential to flight, as flight
in the great majority of instances is performed without them. The elytra
serve as protectors to the wings when the wings are folded upon the back
of the insect, and as they are extended on either side of the body more
or less horizontally when the insect is flying they contribute to flight
indirectly, in virtue of their being carried forward by the body in
motion.
_Natural Flight_.--The manner in which the wings of the insect traverse
the air, so as practically to increase the basis of support, raises the
whole subject of natural flight. It is necessary, therefore, at this
stage to direct the attention of the reader somewhat fully to the
subject of flight, as witnessed in the insect, bird and bat, a knowledge
of natural flight preceding, and being in some sense indispensable to, a
knowledge of artificial flight. The bodies of flying creatures are, as a
rule, very strong, comparatively light and of an elongated form,--the
bodies of birds being specially adapted for cleaving the air. Flying
creatures, however, are less remarkable for their strength, shape and
comparative levity than for the size and extraordinarily rapid and
complicated movements of their wings. Prof. J. Bell Pettigrew first
satisfactorily analysed those movements, and reproduced them by the aid
of artificial wings. This physiologist in 1867[3] showed that all
natural wings, whether of the insect, bird or bat, are screws
structurally, and that they act as screws when they are made to vibrate,
from the fact that they twist in opposite directions during the down and
up strokes. He also explained that all wings act upon a common
principle, and that they present oblique, kite-like surfaces to the air,
through which they pass much in the same way that an oar passes through
water in sculling. He further pointed out that the wings of flying
creatures (contrary to received opinions, and as has been already
indicated) strike downwards and _forwards_ during the down strokes, and
upwards and _forwards_ during the up strokes. Lastly he demonstrated
that the wings of flying creatures, when the bodies of said creatures
are fixed, describe _figure-of-8 tracks_ in space--the figure-of-8
tracks, when the bodies are released and advancing as in rapid flight,
being opened out and converted into _waved tracks_.
It may be well to explain here that a claim has been set up by his
admirers for the celebrated artist, architect and engineer, Leonardo
da Vinci, to be regarded as the discoverer of the principles and
practice of flight (see Theodore Andrea Cook, _Spirals in Nature and
Art_, 1903). The claim is, however, unwarranted; Leonardo's chief work
on flight, bearing the title _Codice sul Volo degli Uccelli e Varie
Altre Materie_, written in 1505, consists of a short manuscript of
twenty-seven small quarto pages, with simple sketch illustrations
interspersed in the text. In addition he makes occasional references
to flight in his other manuscripts, which are also illustrated. In
none of Leonardo's manuscripts, however, and in none of his figures,
is the slightest hint given of his having any knowledge of the spiral
movements made by the wing in flight or of the spiral structure of the
wing itself. It is claimed that Leonardo knew the direction of the
stroke of the wing, as revealed by recent researches and proved by
modern instantaneous photography. As a matter of fact, Leonardo gives
a wholly inaccurate account of the direction of the stroke of the
wing. He states that the wing during the down stroke strikes downwards
and _backwards_, whereas in reality it strikes downwards and
_forwards_. In speaking of artificial flight Leonardo says: "The wings
have to row downwards and _backwards_ to support the machine on high,
so that it moves forward." In speaking of natural flight he remarks:
"If in its descent the bird rows _backwards_ with its wings the bird
will move rapidly; this happens because the wings strike the air which
successively runs behind the bird to fill the void whence it comes."
There is nothing in Leonardo's writings to show that he knew either
the anatomy or physiology of the wing in the modern sense.
Pettigrew's discovery of the figure-of-8 and waved movements made by the
wing in stationary and progressive flight was confirmed some two years
after it was made by Prof. E.J. Marey of Paris[4] by the aid of the
"sphygmograph."[5] The movements in question are now regarded as
fundamental, from the fact that they are alike essential to natural and
artificial flight.
The following is Pettigrew's description of wings and wing movements
published in 1867:--
"The wings of insects and birds are, as a rule, more or less
triangular in shape, the base of the triangle being directed towards
the body, its sides anteriorly and posteriorly. They are also conical
on section from within outwards and from before backwards, this shape
converting the pinions into delicately graduated instruments balanced
with the utmost nicety to satisfy the requirements of the muscular
system on the one hand and the resistance and resiliency of the air on
the other. While all wings are graduated as explained, innumerable
varieties occur as to their general contour, some being falcated or
scythe-like, others oblong, others rounded or circular, some
lanceolate and some linear. The wings of insects may consist either of
one or two pairs--the anterior or upper pair, when two are present,
being in some instances greatly modified and presenting a corneous
condition. They are then known as elytra, from the Gr. [Greek:
elytron], a sheath. Both pairs are composed of a duplicature of the
integument, or investing membrane, and are strengthened in various
directions by a system of hollow, horny tubes, known to entomologists
as the neurae or nervures. These nervures taper towards the extremity
of the wing, and are strongest towards its root and anterior margin,
where they supply the place of the arm in birds and bats. The neurae
are arranged at the axis of the wing after the manner of a fan or
spiral stair--the anterior one occupying a higher position than that
farther back, and so of the others. As this arrangement extends also
to the margins, _the wings are more or less twisted upon themselves_
and present a certain degree of convexity on their superior or upper
surface, and a corresponding concavity on their inferior or under
surface,--their free edges supplying those fine curves which act with
such efficacy upon the air in obtaining the maximum of resistance and
the minimum of displacement. As illustrative examples of the form of
wings alluded to, those of the beetle, bee and fly may be cited--the
pinions in those insects acting as _helices_, or _twisted levers_,
and elevating weights much greater than the area of the wings would
seem to warrant" (figs. 10 and 11).... "To confer on the wings the
multiplicity of movements which they require, they are supplied with
double hinge or compound joints, which enable them to move not only in
an upward, downward, forward and backward direction, but also at
various intermediate degrees of obliquity. An insect with wings thus
hinged may, as far as steadiness of body is concerned, be not inaptly
compared to a compass set upon gimbals, where the universality of
motion in one direction ensures comparative fixedness in another."...
"All wings obtain their leverage by presenting oblique surfaces to the
air, the degree of obliquity gradually increasing in a direction from
behind, forwards and downwards, during extension when the sudden or
effective stroke is being given, and gradually decreasing in an
opposite direction during flexion, or when the wing is being more
slowly recovered preparatory to making a second stroke. The effective
stroke in insects, and this holds true also of birds, is therefore
delivered _downwards and forwards_, and not, as the majority of
writers believe, vertically, or even slightly backwards.... The wing
in the insect is more flattened than in the bird; and advantage is
taken on some occasions of this circumstance, particularly in
heavy-bodied, small-winged, quick-flying insects, _to reverse the
pinion more or less completely during the down and up strokes_."...
"This is effected in the following manner. The posterior margin of the
wing is made to rotate, during the down stroke, in a direction from
above downwards and from behind forwards--the anterior margin
travelling in an opposite direction and reciprocating. The wing may
thus be said to attack the air by a _screwing movement_ from above.
During the up or return stroke, on the other hand, the posterior
margin rotates in a direction from below upwards and from before
backwards, so that by a similar but _reverse screwing motion_ the
pinion attacks the air from beneath."... "_A figure-of-8_, compressed
laterally and placed obliquely with its long axis running from left to
right of the spectator, represents the movements in question. _The
down and up strokes_, as will be seen from this account, _cross each
other_, the wing smiting the air during its descent from above, as in
the bird and bat, and during its ascent from below as in the flying
fish and boy's kite" (fig. 12).
[Illustration: FIG. 10.--Right Wing of the Beetle (_Goliathus micans_)
when at rest; seen from above.]
[Illustration: FIG. 11.--Right Wing of the Beetle (_Goliathus micans_)
when in motion; seen from behind. This figure shows how the wing
twists and untwists when in action, and how it forms a true screw.]
[Illustration: FIG. 12 shows the figure-of-8 made by the margins of
the wing in extension (continuous line), and flexion (dotted line). As
the tip of the wing is mid-way between its margins, a line between the
continuous and dotted lines gives the figure-of-8 made by the tip. The
arrows indicate the reversal of the planes of the wing, and show how
the down and up strokes _cross each other_.]
... "The figure-of-8 action of the wing explains how an insect or bird
may fix itself in the air, the backward and forward reciprocating
action of the pinion affording support, but no propulsion. In these
instances the backward and forward strokes are made to counterbalance
each other. Although the figure-of-8 represents with considerable
fidelity the twisting of the wing upon its axis during extension and
flexion, when the insect is playing its wings before an object, or
still better when it is artificially fixed, it is otherwise when the
down stroke is added and the insect is fairly on the wing and
progressing rapidly. In this case the wing, in virtue of its being
carried forward by the body in motion, describes an undulating or
spiral course, as shown in fig. 13."
... "The down and up strokes are compound movements--the termination
of the down stroke embracing the beginning of the up stroke, and the
termination of the up stroke including the beginning of the down
stroke. This is necessary in order that the down and up strokes may
glide into each other in such a manner as to prevent jerking and
unnecessary retardation."[6]...
[Illustration: FIG. 13.--Wave track made by the wing in progressive
flight. a, b, Crests of the wave; c, d, e, up strokes; x, x, down
strokes; f, point corresponding to the anterior margin of the wing,
and forming a centre for the downward rotation of the wing (a, g); g,
point corresponding to the posterior margin of the wing, and forming a
centre for the upward rotation of the wing (d, f).]
[Illustration: FIG. 14.--a, b, line along which the wing travels
during extension and flexion. The arrows indicate the direction in
which the wing is spread out in extension and closed or folded in
flexion.
Extension (elbow). Flexion (wrist).