HISTORY OF 



southward, still nearer the Line. They again 

 appear in the fields of Pisa regularly about the 

 twentieth of February, to anticipate the spring. 



In these journeys it is amazing to conceive the 

 heights to which they ascend when they fly. 

 Their note is the loudest of all other birds ; and 

 that is often heard in the clouds, when the bird 

 itself is entirely unseen. As it is light for its 

 size, and spreads a large expanse of wing, it is 

 capable of floating at the greatest height, where 

 the air is lightest; and as it secures its safety, 

 and is entirely out of the reach of man, it flies in 

 tracts which would be too fatiguing for any other 

 birds to move forward in. 



In these aerial journeys, though unseen them- 

 selves, they have the distinctest vision of every 

 object below. They govern and direct their 

 flight by their cries ; and exhort each other to 

 proceed or to descend, when a fit opportunity 

 offers for depredation. Their voice, it was ob- 

 served, is the loudest of all the feathered tribe ; 

 and its peculiar clangour arises from the very ex- 

 traordinary length and contortion of the wind- 

 pipe. In quadrupeds the windpipe is short, and 

 the glottis, or cartilages that form the voice, are 

 at that end of it which is next the mouth : in 

 water fowl the windpipe is longer, but the car- 

 tilages that form the voice are at the other end, 

 which lies down in their belly. By this means 

 they have much louder voices, in proportion to 

 their size, than any other animals whatever ; for 

 the note, when formed below, is reverberated 

 through all the rings of the windpipe till it 



