Wing (anatomy)

“ How to apply Artificial Wings to the Air.—Borelli, Durckheim, Marey, and all the writers with whom I am acquainted, assert that the wing should be made to vibrate vertically. I believe that if the wing be in one piece it should be made to vibrate obliquely and more or less horizontally. ”

“ Although it is perfectly true that a wing could be of no use as a wing until sufficiently developed to serve the purpose of flight, this is merely to say that until it has become a wing it is no use as a wing. ”

“ Curves in the Wing of a Partridge in Flight.
The wings, when flexed and extended in flight, assume curved surfaces, which change at each instant and carve the air, as does the tail of the fish the water, into complex wave-lines; and such is the structure of the wing that these results are inevitable when it is put in motion. "The muscles, bones, ligaments, and feathers, are so adjusted with reference to each other that, if the wing is moved at all, it must move in the proper direction." The bird no more thinks of its motions in flying than we do of ours in walking ”

“ THE WING STRUCTURE.—The wing structure of every flying creature that man has examined, has one universal point of similarity, and that is the manner of its connection with the body. It is a sort of universal joint, which permits the wing to swing up and down, perform a gyratory movement while doing so, and folds to the rear when at rest. ”

“ In birds which glide or skim, it has appeared to me that the wing is recovered much more quickly, and the down stroke delivered more slowly, than in ordinary flight—in fact, that the rapidity with which the wing acts in an upward and downward direction is, in some instances, reversed; and this is what we should naturally expect when we recollect that in gliding, the wings require to be, for the most part, in the expanded condition. ”

“ To meet this difficulty, the wing is so shaped that it is concave or hollow upon its lower surface, so that it gathers the air together and prevents it from escaping; while the upper surface is convex or bulging, so that the air slides off from it when the wing is moved upward. ”

“ They afford an opportunity only of admiring at a distance the extraordinary agility and the stateliness likewise of their motions, the richness of their plumage, and the great propriety there was of ascribing to them ‘an expanded, quivering wing.’ Nothing certainly can be more beautiful and entertaining than such a sight! the wings, by their repeated though unwearied vibrations, equally serving them for sails and oars; while their feet, no less assisting in conveying them out of sight, are no less insensible of fatigue. ”

“ The compound rotation of the wing is greatly facilitated by the wing being elastic and flexible. It is this which causes the wing to twist and untwist diagonally on its long axis when it is made to vibrate. ”

“ The Wing during its Vibration produces a Cross Pulsation.—The oscillation of the wing on two separate axes—the one running parallel with the body of the bird, the other at right angles to it (fig. 80, a b, c d) —is well worthy of attention, as showing that the wing attacks the air, on which it operates in every direction, and at almost the same moment, viz. from within outwards, and from above downwards, during the down stroke ”

“ The way in which the natural wing rises and falls on the air, and reciprocates with the body of the flying creature, has a very obvious bearing upon artificial flight. In natural flight the body of the flying creature falls slightly forward in a curve when the wing ascends, and is slightly elevated in a curve when the wing descends. The wing and body are consequently always playing at cross purposes, the wing rising when the body is falling and vice versa. ”

“ The time, power, and space occupied in reversing the wing alone, according to this theory, are such as to render flight impossible. That the wing does not act as stated by Borelli, Marey, and others may be readily proved by experiment. ”

“ Hence the whole mass of the bird rebounds, making a fresh leap through the air; whence it follows that flight is simply a motion composed of successive leaps accomplished through the air. And I remark that a wing can easily beat the air in a direction almost perpendicular to its plane surface, although only a single one of the corners of the humerus bone is attached to the scapula, the whole extent of its base remaining free and loose, while the greater transverse feathers are joined to the lateral skin of the thorax. ”

“ The Wing at all times thoroughly under control.—The wing is moveable in all parts, and can be wielded intelligently even to its extremity; a circumstance which enables the insect, bat, and bird to rise upon the air and tread it as a master—to subjugate it in fact. The wing, no doubt, abstracts an upward and onward recoil from the air, but in doing this it exercises a selective and controlling power; it seizes one current, evades another, and creates a third; it feels and paws the air as a quadruped would feel and paw a treacherous yielding surface. ”

“ As will be seen from this figure, the wing advances both when it rises and when it falls. It is a peculiarity of natural wings, and of artificial wings constructed on the principle of living wings, that when forcibly elevated or depressed, even in a strictly vertical direction, they inevitably dart forward. If, for instance, the wing is suddenly depressed in a vertical direction, as at a b of fig. 29, it at once darts downwards and forwards in a double curve (see continuous line of figure) to c, thus converting the vertical down stroke into a down, oblique, forward stroke. ”

“ Some experimenters place the center of gravity far below the wings in the belief that the wings would naturally seek to remain at the lowest point. A more satisfactory system, especially for lateral balance, was that of arranging the wings in the shape of a broad V to form a dihedral angle, with the center low and the wing-tips elevated. ”

“ In starting, the wing, except at the very beginning of the stroke, pushes against air which is already in motion in the same direction as the wing itself; but in swift flight the whole stroke is against dead air, for the air beneath the wing is continually renewed by the motion of the bird. ”

“ That the wings invariably strike forwards during the down and up strokes in aerial flight is proved alike by observation and experiment. If any one watches a bird rising from the ground or the water, he cannot fail to perceive that the head and body are slightly tilted upwards, and that the wings are made to descend with great vigour in a downward and forward direction. The dead natural wing and a properly constructed artificial wing act in precisely the same way. ”

“ 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. ”

“ 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 wing to act efficiently must be driven at a certain speed, and in such a manner that the down and up strokes shall glide into each other. It is only in this way that the air can be made to pulsate, and that the rhythm of the wing and the air waves can be made to correspond. ”

“ They nearly all, however, use some slightly gliding force at the same time; a single stroke of the wing, with forward intent, seeming enough to enable them to glide on for half a minute or more without stirring a plume. ”

“ The Wing, when advancing with the Body, describes a Looped and Waved Track.—Although the figure-of-8 represents with considerable fidelity the twisting of the wing upon its long axis during extension and flexion, and during the down and up strokes when the volant animal is playing its wings before an object, or still better, when it is artificially fixed, it is otherwise when it is free and progressing rapidly. ”

“ This mechanical impediment is followed by serious consequences as far as power and speed are concerned—the slowing of the wing at the end of the down and up strokes involving a great expenditure of power and a disastrous waste of time. The wing, to be effective as an elevating and propelling organ, should have no dead points, and should be characterized by a rapid winnowing or fanning motion. ”

“ The pectoral muscles of a bird are reproduced by two strong springs which are extended by the upward motion of the wings and store up energy for the down-stroke. Close attention is also being paid to the actual shape of a bird’s wing, which is not flat but hollow on its under side, and at the front has a slightly downward dip. “Aerocurves” are therefore likely to supersede the “aeroplane,” for Nature would not have built bird’s wings as they are without an object. ”

“ The wing is so constructed that the posterior margin yields freely in a downward direction during the up stroke, while it yields comparatively little in an upward direction during the down stroke; and this is a distinguishing feature, as the wing is thus made to fold and elude the air more or less completely during the up stroke, whereas it is made to expand and seize the air with avidity during the down stroke. ”

“ The Artificial Wing propelled at various degrees of speed during the Down and Up Strokes.—The tendency which the artificial wave wing has to rise again when suddenly and vigorously depressed, explains why the elevator muscles of the wing should be so small when compared with the depressor muscles—the latter being something like seven times larger than the former. ”

“ No less admirable is nature’s cunning in unfolding and folding the wings upwards, for she folds them not laterally, but by moving upwards edgewise the osseous parts wherein the roots of the feathers are inserted; for thus, without encountering the air’s resistance the upward motion of the wing surface is made as with a sword, hence they can be uplifted with but small force. ”

“ Very often the same effect is produced by allowing the force of gravity to act, and when the downward momentum has brought the bird close to the ground or to the sea, that force is again converted into an ascending impetus by a change in the angle at which the wing is exposed to the wind. ”

“ From observation he gathered how a bird checks its own speed by opposing tail and wing surface to the direction of flight, and thus alights at the proper ‘landing speed.’ He proved the existence of upward air currents by noting how a bird takes off from level earth with wings outstretched and motionless, and, in order to get an efficient substitute for the natural wing, he recommended that there be used something similar to the membrane of the wing of a bat—from this to the doped fabric of an aeroplane wing is but a small step, for both are equally impervious to air. ”

“ The muscles that work a bird’s wing are wonderfully powerful and strong, far stronger in proportion than the muscles of a man’s arm. To sustain his great weight in the air, a man of eleven stone would require a pair of wings nearly twenty feet in span. But the possession of such mighty wings alone is not enough. ”

“ It will be very convenient also to have a wing dissected from the body and the wing itself held in about the soaring curve by a bit of light stick balanced on a pencil point, which will give the CG of the wing as distinct from that of the body. ”