242 THE BOOK OF MIGRATORY BIRDS 



wheels high out of shot, leaving his enemy disappointed 

 and vexed at having crept in vain through bog and over 

 rock in expectation of carrying home so glorious a trophy 

 of his skill." 



The measurements of an eagle of average size are as 

 follow: Length from tip of beak to end of tail, 35in.; 

 from the surface of the rock on which he sits to top of 

 head, 2oin. ; width of partially expanded tail, i5in. ; length 

 of wing from shoulder to end of flight feathers, 24in. 



The eagle is admirably adapted to perform the duties 

 assigned to him. The anatomy of the eye alone is a 

 perfect study, and this wonderful organ has a power of 

 vision of which men have not the slightest idea, even 

 though our sight might be aided by a telescope. The 

 brain is large and well developed, the convolutions of grey 

 matter dipped deep down into the white matter, thus show- 

 ing a considerable amount of intelligence in the bird. The 

 lens of the eye is very peculiar ; it is flattened on each side 

 and as brilliant as a diamond. A fish's lens is round. It 

 is commonly believed that the eagle has a muscular 

 apparatus connected with his eye, by means of which he 

 can convert it, as it were, into a telescope for seeing long 

 distances, and can so adapt his powers of vision as to see 

 clearly at shorter distances. He must, indeed, have the 

 most perfect organs of sight of any created thing. When 

 he is soaring so high in the air that he can hardly be seen 

 by the human eye it is said that he can easily detect a 

 hare or a lamb on the ground. 



The appearance of the bird in high air is very interesting, 

 and its average height is such as to make it appear as 

 merely a swallow. That eagles usually hunt for prey in 

 couples is well known, and it is observed that they invari- 

 ably describe the figure of eight in their peculiarly graceful 

 curves, whilst their general motion in flight is elegance 

 itself. It is also noticed how one flap of the wing serves 

 to carry the bird on for many minutes without any more 

 exertion on his part. The great power of the eagle is 

 concentrated in the hind claw. When the bird strikes his 



