THE NUTMEG BIRD 55 



moving nineteen to the dozen with scarcely a sound 

 issuing, you are inclined to think that he is either play- 

 ing dumb crambo or that he has taken leave of his 

 senses. Nothing of the kind. The bird is singing his 

 top notes, which are doubtless greatly appreciated by 

 his mate. Sound is, as we all know in this scientific age, 

 vibration appreciable to the ear. Air is the usual vibrat- 

 ing medium. Only certain vibrations are perceptible 

 to the human auditory organ. Those having a recur- 

 rence of below thirty or above sixteen thousand per 

 second do not produce the sensation of sound to the 

 average human ear. There are thus numbers of vibra- 

 tions continually going on which are lost to us; to this 

 category belong the vibrations in the air produced by 

 the vocal cords of the spotted munia. The ear of a 

 bird is constituted very differently from that of man, 

 so that it is not surprising if birds can hear certain 

 sounds imperceptible to us human beings. I may here 

 say that the range of the human ear varies greatly in 

 different individuals. Some men can hear vibrations 

 of which the recurrence is but fifteen in the second, 

 while others are said to appreciate notes caused by forty 

 thousand vibrations per second. I have a friend who 

 cannot hear a black partridge when it is calling ; its 

 notes are too high for the unusually limited range of his 

 ear. I do not know if there are any people to whom 

 the note of the nutmeg bird sounds quite loud ; if 

 there be, and these lines meet their eye, I hope they will 

 give their brethren of more limited capacity the benefit 

 of their experience. 



