o GRAMINIVOKJE. 



rapidly in proportion to the whole quantity of flight, the 

 song is partially suppressed, and it swells as the spiral widens, 

 and sinks as it contracts ; so that though the notes may be 

 the same, it is only when the lark sings poised at the same 

 height, that it sings in an uniform key. It gives a swelling" 

 song as it ascends, and a sinking one as it comes down ; and 

 even if it take but one wheel in the air, as that wheel 

 always includes either an ascent or a descent, it varies the 

 pitch of the song. 



The song of the lark, besides being a most accessible and 

 delightful subject for common observation, is a very curious 

 one for the physiologist. Every one in the least conversant 

 with the structure of birds must be aware that, with them, 

 the organs of intonation and modulation are inward, deriving 

 little assistance from the tongue, and none, or next to none, 

 from the mandibles of the bill. The windpipe is the musical 

 organ, and it is often very curiously formed. Birds require 

 that organ less for breathing, than other animals ' having a 

 windpipe and lungs, because of the air-cells and breathing- 

 tubes with which all parts of their bodies (even the bones) 

 are furnished. But those diffused breathing organs must act 

 with least freedom when the bird is making the greatest 

 efforts in motion; that is, when ascending or descending; 

 and in proportion as these cease to act, the trachea is the 

 more required for the purposes of breathing. The sky-lark 

 thus converts the atmosphere into a musical instrument of 

 many stops, and so produces an exceedingly wild and varied 

 song, a song which is, perhaps, not equal either in power 

 or compass, in the single stave, to that of many of the 

 warblers, bub one which is more varied in the whole suc- 

 cession. All birds that sing ascending or descending have 

 similar power, but the sky-lark has it in a degree superior 

 to any other. 



Every body knows the sky-lark, so that it hardly needs to 



