DP PETTIGEEW ON THE PHYSIOLOGY OF WINGS. 371 



of the body. The space through which the body descends when the wings 

 ascend is very trifling, from the fact that the body is situated at the roots of 

 the wings — a very slight movement at the roots of the pinions necessitating an 

 extensive movement at the tips. This explains the very small waved track made 

 by the body in progressive flight as compared with that made by the wings. 

 (Contrast 1, 2, 3, 4, 5 of figure 14 page 344, with ac eg i of the same figure.) 



The Wings of the Bird form a Natural Parachute from which the Body 

 Depends both during the Doivn and Up Strokes. — The falling downwards of the 

 body, and the gradual expansion and elevation of the wings during the up 

 stroke, is seen at Plate XIII. figures 13, 14, and 15. At figure 13 the wings 

 and the body are in the position peculiar to them at the end of the down stroke, 

 i.e., the body is elevated and the wings depressed. The up stroke is com- 

 menced, and the body falls, while the wings are somewhat expanded and 

 elevated, as at Plate XIII. figure 14. The body falls still more, and the wings 

 are further elevated and expanded, as seen at Plate XIII. figure 15. The 

 wings are now on a level with the body of the bird, and mark how beautifully 

 the latter is buoyed up. The body is attached to, and suspended from, a wide- 

 spread finely arched parachute. The body goes on falling, and the wings rising, 

 till the body is depressed and the wings elevated, as seen at 2, 2' and 3, 3' of 

 figure 18, Plate XIV. This terminates the up stroke, and it will be observed 

 that the position of the body is just the reverse of what it was at the beginning 

 of the up stroke. At the beginning of the up stroke, the body was highest and 

 the wings lowest (vide figure 13, Plate XIII.) At the end of the up stroke, 

 the body is lowest and the wings highest (vide 3, 3' of figure 18, Plate XIV.) 

 That the body is supported and carried forward during the up stroke of the wings 

 is proved beyond doubt by the experiment described at pages 355, 356, and 

 illustrated by figure 23. If the quill feathers a, b, of figure 23 (p. 356) be compared 

 with the two wings 3, 3' of figure 18, Plate XIV., and the cork c of figure 23 

 with the body of the bird in figure 18, Plate XIV., it will be found that the con- 

 ditions are the same in both, and that both are to a great extent sustained and 

 carried forward in space, the one by the overarching feathers and the other by 

 the overarching wings. 4 ' Perhaps the simplest illustration that can be given of 



: Weight necessary to Flying Animals as at present constructed — Weight and Levity relatively 

 'onsidered with regard to Aerial and Subaquatic Flight (Diving). — Captain W. F. Hutton, in a recent 

 pamphlet (On the Sailing Flight of the Albatros, Phil. Mag., August 1869), contends, that whereas a 

 bird lighter than the water can fly in it, so, in like manner, a bird lighter than the air could fly in this 

 medium, and that therefore loeight is not necessary to aerial flight. Captain Hutton, however, forgets 

 that a hird destined to fly above the Water is provided with travelling surfaces so fashioned and so 

 applied (they strike from above dowmoards and forwards), that if it was lighter than the air, they would 

 carry it off into space without the possibility of a return ; in other words, the action of the wings would 

 carry the bird obliquely upwards, and render it quite incapable of flying either in a horizontal or down- 

 ward direction. In the same way a bird destined to fly under the water (auk and penguin), if it was 

 not lighter than the water, such is the configuration and mode of applying its travelling surfaces 

 (they strike from below upwards and backwards), they would carry it in the direction of the bottom 



VOL. XXVI. PART II. 5 D 



