21)0 LETTERS ON NATURAL MAGIC. 



hearing to total want of perception occasions a degree of 

 surprise, which renders an experiment on this subject with 

 a series of small pipes among several persons rather 

 amusing. It is curious to observe the change of feeling 

 manifested by various individuals of the party, in succes- 

 sion, as the sounds approach and pass the limits of their 

 hearing. Those who enjoy a temporary triumph are often 

 compelled in their turn to acknowledge to how short a 

 distance their little superiority extends." In concluding 

 his interesting paper on this subject, Dr. Wollaston con- 

 jectures that animals, like the grylli (whose powers of 

 hearing appear to commence nearly where ours terminate), 

 may have the power of hearing still sharper sounds which 

 at present we do not know to exist, and that there may be 

 other insects having nothing in common with us, but who 

 are endowed with a power of exciting, and a sense of per- 

 ceiving vibrations which make no impression upon our 

 organs, while their organs are equally insensible to the 

 slower vibrations to which we are accustomed. 



With the view of studying the class of sounds inaudible 

 to certain ears, we would recommend to the young 

 naturalist to examine the sounds emitted by the insect 

 tribe, both in relation to their effect upon the human ear, 

 and to the mechanism by which they are produced. The 

 CicadaB or locusts in North America appear, from the 

 observations of Dr. Hildreth,* to be furnished with a 

 bagpipe on which they play a variety of notes. " When 

 any one passes," says he, " they make a great noise and 

 screaming with their air-bladder or bagpipes. These bags 

 are placed under, and rather behind, the wings in the 

 axilla, something in the manner of using the bagpipes 

 with the bags under the arms, I could compare them to 

 nothing else ; and, indeed, I suspect the first inventor of 

 the instrument borrowed his ideas from some insect of 



* Edinburgh Journal of Science, No. xvii. p. 158. 



