12 FACULTIES OF BIRDS. 



adaptation of the eye to distance by its muscularity or 

 extension, its vessels being injected to extend it, and 

 emptied to contract it. This is also mere supposition. 

 The muscular power of the fringes of the ciliary ring 

 in drawing the crystalline forwards or backwards 

 is another supposition, as is proved by the want of 

 contractile power in these fringes, the very point on 

 which the opinion is founded. 



We have not a doubt it is by the eye alone that the 

 carrier pigeon (Columba tabellaria, RAY) performs 

 those extraordinary aerial journeys which have from 

 the earliest ages excited astonishment. We have 

 frequently witnessed the experiment made with other 

 pigeons of taking them to a distance from the dove- 

 cot, expressly to observe their manner of rinding their 

 way back, and we feel satisfied that their proceedings 

 are uniformly the same. On being let go from the 

 bag, in which they have been carried in order to conceal 

 from their notice the objects on the road, they dart 

 off on an irregular excursion, as if it were more to 

 ascertain the reality of their freedom than to make an 

 effort to return. When they find themselves at full 

 liberty, they direct their flight in circles round the spot 

 whence they have been liberated, not only increasing 

 the diameter of the circle at every round, but rising 

 at the same time gradually higher. This is continued 

 as long as the eye can discern the birds, and hence we 

 conclude that it is also continued after we lose sight 

 of them, a constantly increasing circle being made, till 

 they ascertain some known object enabling them to 

 shape a direct course*. 



It is not a little interesting to contrast the proceedings 

 just described with those of a pigeon let off from a 

 balloon elevated abo've the clouds. Instead of rising 

 in circles like the former, the balloon pigeon drops 

 perpendicularly down like a plummet, till it is able to 

 * J. R. 



