388 DR PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



knows that these Grallatorial animals are excellent birds of flight. Of all travel- 

 ling birds they undertake the longest and most remote journeys. They are, 

 in addition, the eagle excepted, the birds which elevate themselves the highest, 

 and the flight of which is the longest maintained." 



Flight of Gannet as witnessed at the Bass Rock. — But to return to the gannet, 

 the flight of which, as witnessed from the Bass, I was about to describe. 



The wings and body of the bird, as I fully satisfied myself, can be moved 

 in all their parts. The wings and body are, moreover, thoroughly under control. 

 The body can be twisted about in a remarkable manner — sideways and in 

 an upward and downward direction. The individual feathers of the wing are 

 likewise under control. In fact, the muscular movements can be seen extend- 

 ing along the pinion to the roots of the rowing feathers, the muscular influence 

 spreading thence to the tips. This could readily be ascertained, as the birds 

 wheeled round and round right overhead, and within a very few yards of where I 

 was standing. 



When the gannet throws itself from a cliff it makes a large curve, the con- 

 vexity of which is directed downwards. It acquires speed and momentum by 

 a few gentle flappings of the wings, or it holds the wings comparatively motion- 

 less, and sails for a great distance without effort — the weight of the trunk doing 

 the principal portion of the work." In the sailing movement the body is forced 

 into an upward or downward curve, according to circumstances. 



When the bird has acquired momentum, either by flapping its wings or by 

 projecting itself from a cliff, it has the air perfectly under control. If it wishes 

 to turn to the right it elevates the left wing and depresses the right one, the 

 head and neck bending in the direction of the curve to be described. If it 

 would turn to the left the movements are reversed.! If it desires to ascend, 

 the head, neck, body, and wings are elevated hi an upward direction, so as to 

 increase the angle made by them with the horizon, the angle referred to being 

 decreased or reversed when the bird wishes to descend. If the bird aims at 

 horizontal flight, the head, neck, body, and wings are arranged so as to be nearly 

 parallel with the surface of the sea. The gannet wheels and skims about with 

 all imaginable ease and grace — now oscillating on the long axis of the body as 

 a centre, and now upon the long axes of the wings as a centre. In all these 

 movements the head, neck, tail, and body perform an important part. 



When the gannet throws itself from a rock it rises to nearly the same level 

 as that from which it precipitated itself, without any apparent effort, thus showing 

 that the friction experienced in flight must be almost nil. 



The neck, body, and tail, of the gannet are exceedingly flexible, and admit 



* Compare with mechanical experiment described at pages 355 and 356. 



t The swallow and crane, which dart along at a very high speed, tilt their bodies in turning; but, 

 in addition, flap their wings and fly round the curve they wish to describe. 



