6 FACULTIES OP BIRDS. 



and it might be for this reason, perhaps, that he was 

 induced to separate it from the eagles and class it 

 with the owls. There can be no doubt Aristotle 

 was in error in making this remark, as the distance 

 from which it is observed to dart upon its prey 

 proves its sight to be very acute rather than deficient. 

 Aldrovand examined the eye of this bird with minute 

 attention, in order to verify or disprove Aristotle's 

 observations. He accordingly discovered, what Aris- 

 totle probably meant by a shade or cloud, that the 

 opening of the pupil, commonly covered only by the 

 transparent cornea, is in the osprey lined with a very 

 delicate membrane, having the appearance of a small 

 spot. Any apparent inconvenience of structure that 

 might arise from this circumstance is compensated by 

 the great transparency of the circle round the pupil, 

 which in most other birds is dull and opaque. It 

 does not therefore follow that its sight is fainter than 

 that of other birds, because the light can pass easily 

 and largely through the small circle which bounds 

 the pupil, though it is probable the middle of the 

 image will be marked with a small obscure spot, and 

 that the lateral vision ought to be more distinct than 

 the direct. It does not however appear that it sees 

 worse than other birds. It may not perhaps soar 

 quite so high as the golden eagle (Aquila chrysaetas, 

 ALDROVAND), nor descry and pursue its prey from 

 such remote distances, nor have quite so acute vision ; 

 but it is not, like the owls, blinded by dazzling light, 

 and it searches for victims as well by day as by night. 

 Willughby thinks it " partly false or uncertain," 

 that the golden eagle *' doth so excel in quick-sight- 

 edness, soaring so high in the air that she can very 

 hardly be discerned by us in all that light, yet she can 

 espy a hare lying under a bush, or a little fish 

 swimming in the water ; though I grant," he adds, 



