120 CLASS AVES. 



cease to wonder at their compass and power of voice. More- 

 over, they possess a tracheal artery, composed of rings entirely 

 cartilaginous, destitute of epiglottis, and which does not carry 

 its vocal chords towards the pharynx, but which forms a 

 lower larynx towards the bifurcation of this same tracheal 

 artery. The upper part of this canal, which surmounts this 

 lower larynx, serves it in some measure as a speaking-trumpet. 

 Besides, the sound of the voice, coming in collision with the 

 circular fibres and the demi-osseous rings of this tracheal 

 artery, resounds with force, especially in the males, who are 

 often provided with a sort of tendinous drums towards the 

 glottis, while the females are destitute of such appendages. 

 This musical apparatus in birds may be compared to the French 

 horn, for that instrument is formed nearly on the same prin- 

 ciples. These organs of song are considerably less perfect in 

 the females, for they are without those demi-osseous and re- 

 sounding cavities which the males possess, inasmuch as they 

 are not designed for singing. " The bird," says Buffon, 

 " which makes itself heard at the distance of a league in high 

 air, (as do storks, wild geese, &c.) and produces sounds in a 

 medium which considerably diminishes their intensity, and 

 more and more abridges their extension (in consequence of its 

 rarefaction,) must possess a voice four times the strength of 

 those of men or quadrupeds, which can only be heard half a 

 league at furthest on the surface of the earth. This calcula- 

 tion, too, is probably rather under than over the reality ; for, 

 independently of what has been now advanced, there is ano- 

 ther point which adds weight to our conclusions, and that is, 

 that the sound produced in the midst of the air must, in being 

 propagated, fill a sphere of which the bird is the centre, while 

 the sound produced on the surface of the earth fills only a 

 demi-sphere ; and that portion of the sound which is reflected 

 against the earth, aids and furthers the propagation of that 

 which is heard vertically and laterally." 

 In truth, the song of the blackbird is heard at least at as great a 



