VOCAL ORGANS, 243 



sipation of force to be attributed to the cause already 

 assigned, the sound is propagated in the higher 

 regions as from a centre in all directions, and only a 

 part of it reaches the ground ; but, when made at the 

 surface, the aerial waves are reflected as they roll 

 along, and the lateral and vertical effect is aug- 

 mented. It is hence that a person on the top of a 

 tower hears one better at the bottom than the person 

 below hears from above *.'' 



With respect to the bittern, an opinion is popularly 

 held, that this bird *' thrusts its bill into a reed that 

 serves it as a pipe for swelling the note above its 

 natural pitch ;" the supposition of some being, " from 

 the loudness and solemnity of the note, that the bird 

 made use of external instruments to produce it, and 

 that so small a body could never eject such a quantity 

 of tone; while others, and in this number we find 

 Thomson, the poet, imagine that the bird puts its 

 head under water, and then, violently blowing, pro- 

 duces its boomingsf." Thomson says 



-So that scarce 



The bittern knows his time, with bill ingulph'd, 

 To shake the sounding marsh J." 



Had Thomson, however, been acquainted with the 

 Ornithology of Aldrovand, he might there have found 

 a correct account of the vocal organs by which the bird 

 produces the sound, and which we shall now trans- 

 late. " It has not," he says, " like the wild swan 

 and many others, a double larynx, namely, one at the 

 base of the tongue, and another where the windpipe 

 begins to divaricate. In the bittern the windpipe is 

 continuous, having no larynx nor anything analogous 

 to one. But Nature appears to have wished to com- 

 pensate for this deficiency, by constructing two canals 



* Wood's Buffon,xi. 12. 



j- Goldsmith, Anini. Nat. iii. 263. 



J Seasons, Spring. 



