GOLDEN EAGLE. 15 



old Black Cock was sprung, and was instantly pursued 

 by the Eagle (which must have been on a neighbouring 

 rock unperceived) across the glen, the breadth of which 

 was at least two miles. The Eagle made several 

 pounces in view, without success ; but as there was no 

 wood nor cover on the opposite mountain sufficient to 

 conceal so large a bird as a Black Grouse, he doubtless 

 forfeited his life to the merciless tyrant of the rocks." 



Dr. Fleming, who had opportunities of observing 

 these birds when residing in Zetland, says that they are 

 general depredators, and in the breeding-season rob the 

 rock birds of their young, especially the Gulls and 

 Cormorants. This habit is probably common to each 

 of the British Eagles. 



The power of vision in birds is observed to be very 

 extraordinary; and in none is it more conspicuous than 

 in the Eagles, and the Falconidce generally. It has 

 been stated that, probably in the whole range of anato- 

 mical structure, no more perfect or more conclusive 

 proofs of design could be adduced than are to be found 

 in the numerous and beautiful modifications in the form 

 of various parts of the eyes of different animals, des- 

 tined to exercise vision in media of various degrees of 

 transparency as well as density. The figure on the right 

 hand of the vignette at the end of this article represents 

 the circle, composed of fifteen bony plates, by which 

 the orb of the eye of the Golden Eagle is supported. 

 These bony plates are capable of slight motion upon 

 each other. The figure on the left hand in the vignette 

 represents the crystalline lens of the same bird ; the lens 

 being subject to great variety of form in different birds. 

 In the Eagle, the proportion of the axis to the diameter 

 of the lens is as three and eight-tenths to five and seven- 

 tenths ; in the Great Owl, which seeks its prey at twi- 



