the progressive motion of a bird, or other winged animal, in the air.

The parts of birds chiefly concerned in flying are the wings, by which they are sustained or wafted along. The tail, Messrs Willoughby, Ray, and many others, imagine to be principally employed in steering and turning the body in the air, as a rudder; but Borelli has put it beyond all doubt, that this is the least use of it, which is chiefly to assist the bird in its ascent and descent in the air, and to obviate the oscillations of the body and wings: for, as to turning to this or that side, it is performed by the wings and inclination of the body, and but very little by the help of the tail. The flying of a bird, in effect, is quite a different thing from the rowing of a vessel. Birds do not vibrate their wings towards the tail, as oars are struck towards the stern, but waft them downwards; nor does the tail of the bird cut the air at right angles, as the rudder does the water; but is disposed horizontally, and preserves the same situation whatever way forever the bird turns.

In effect, as a vessel is turned about on its centre of gravity to the right, by a brisk application of the oars to the left; so a bird, in beating the air with its right wing alone, towards the tail, will turn its fore-part to the left. Thus pigeons changing their course to the left, would labour it with their right wing, keeping the other almost at rest. Birds of a long neck alter their course by the inclination of their head and neck; which altering the course of gravity, the bird will proceed in a new direction.

The manner of FLYING is thus: The bird first bends his legs, and springs with a violent leap from the ground; then opens and expands the joints of his wings, so as to make a right line perpendicular to the sides of his body; thus the wings, with all the feathers therein, constitute one continued lamina. Being now raised a little above the horizon, and vibrating the wings with great force and velocity perpendicularly against the subject air, that fluid resists those succussions, both from its natural inactivity and elasticity, by means of which the whole body of the bird is protruded. The resistance the air makes to the withdrawing of the wings, and consequently the progress of the bird, will be so much the greater, as the width or stroke of the fan of the wing is longer: but as the force of the wing is continually diminished by this resistance, when the two forces continue to be in equilibrium, the bird will remain suspended in the same place; for the bird only ascends so long as the arch of air the wing describes makes a resistance equal to the excess of the specific gravity of the bird above the air. If the air, therefore, be so rare as to give way with the same velocity as it is struck withal, there will be no resistance, and consequently the bird can never mount. Birds never fly upwards in a perpendicular line, but always in a parabola. In a direct ascent, the natural and artificial tendency would oppose and destroy each other, so that the progress would be very slow. In a direct descent they would aid one another, so that the fall would be too precipitate.

Artificial Flying, that attempted by men, by the assistance of mechanics.

The art of flying has been attempted by several persons in all ages. The Leucadians, out of superstition, are reported to have had a custom of precipitating a man from a high cliff into the sea, first fixing feathers, variously expanded, round his body, in order to break the fall.

Friar Bacon, who lived near 500 years ago, not only affirms the art of flying possible, but affirms us, that he himself knew how to make an engine wherein a man fitting might be able to convey himself through the air like a bird; and further adds, that there was then one who had tried it with success. The secret consisted in a couple of large thin hollow copper-globes, exhausted of air; which being much lighter than air, would sustain a chair, wherein a person might sit. Fa. Francisco Lana, in his Prodromus, proposes the same thing, as his own thought. He computes, that a round vessel of plate-brass, 14 foot in diameter, weighing three ounces the square foot, will only weigh 1848 ounces; whereas a quantity of air of the same bulk, will weigh 2153½ ounces; so that the globe will not only be sustained in the air, but will carry with it a weight of 373½ ounces; and by increasing the bulk of the globe, without increasing the thickness of the metal, he adds, a vessel might be made to carry a much greater weight.—But the fallacy is obvious: a globe of the dimensions he describes, Dr Hook shews, would not sustain the pressure of the air, but be crushed inwards. Besides, in whatever ratio the bulk of the globe were increased, in the same must the thickness of the metal, and consequently the weight, be increased: so that there would be no advantage in such augmentation.

The same author describes an engine for flying, invented by the Sieur Beinier, a smith of Sable, in the county of Maine. Vid. Philosophae Collegi, No. 1.

The philosophers of king Charles the second's reign were mightily baffled about this art. The famous bishop Wilkins was so confident of success in it, that he says, says, he does not question but, in future ages, it will be as usual to hear a man call for his wings, when he is going a journey, as it is now to call for his boots.

FLYING Bridge. See BRIDGE.

FLYING Fish, a name given by the English writers to several species of fish, which, by means of their long fins, have a method of keeping themselves out of water a long time. See EXOCOLUS.

FLYING Pinion, is part of a clock, having a fly, or fan, whereby to gather air, and so bridle the rapidity of the clock's motion, when the weight descends in the striking part.