Now that the study of flight is so much to the fore, some may turn to these pages in the hope of gaining useful information on the theme of mechanical flight. Some help they may find. But it was not for this that they were written. The flight of an aeroplane and the flight of a bird have little in common--at present; though something may be learned by the study of gliding flight and soaring, which of course have their place in this book. But anatomical details and mechanical formulæ, necessary to the serious student of flight, would have been entirely out of place here, and they have been omitted. My task has been by no means easy. But it has been enormously helped by the extremely skilful and beautiful work of the artist, Mr. Roland Green. Where birds are concerned, few artists in the past, and very few in the present, have shown any ability to combine accuracy in drawing with ingenuity of composition and faithfulness in colouring. Mr. Green has shown this rare combination; his coloured plates and line-drawings speak for themselves. W. P. PYCRAFT. _London_, _September, 1922_ CHAPTER I. Concerning Wings. "Divinity within them breeding wings wherewith to scorn the earth."--_Milton._ What a wing is--The quill feathers and their function--The skeleton of the wing--The muscles of the wing--The great air-chambers of the body--The Bat's wing--The wing of flying Dragons--The wings of Dragon-flies and beetles. The flight of birds has always aroused man's envy and stirred his imagination. David longed for the wings of a dove: the writer of the Book of Proverbs tells us that "the way of an eagle" surpasses his understanding. Icarus, spurred on by dire necessity, actually, we are told, contrived to fly--but his maiden effort ended in disaster! To-day we have, in a sense, succeeded where he failed. But only because we have given up the idea of flight by personal effort, and make our aerial journeys in a flying machine. That we owe much of our success to a study of the flight of birds is common knowledge, but the machine which has evolved as a consequence of this study pursues its way through the air after a very different fashion from that of the birds, for its vast body is thrust, or drawn, through the air by means of a propeller, driven at incredible speed, its immobile wings sustaining the weight. The wings of the bird, on the other hand, not only lift the body from the earth, but they sustain it in the air by their marvellously complex movements. And this is true, in varying degrees of bird, and bat, and butterfly: of dragon-fly and beetle.