126 EXPERIMENTS OP M. SAVART. SKCT. XVI. 



animals like the Grylli, whose powers appear to com- 

 mence nearly where ours terminate, may have the fac- 

 ulty of hearing still sharper sounds which we do not 

 know to exist, and that there may be other insects hear- 

 ing nothing in common with us, but endowed with a 

 power of exciting, and a sense which perceives vibrations 

 of the same nature indeed as those which constitute our 

 ordinary sounds, but so remote that the animals who 

 perceive them may be said to possess another sense, 

 agreeing with our own solely in the medium by which 

 it is excited. 



M. Savart, so well known for the number and beauty 

 of his researches in acoustics, has proved that a high 

 note of a given intensity being heard by some ears and 

 not by others, must not be attributed to its pitch, but to 

 its feebleness. His experiments, and those more re- 

 cently made by Professor Wheatstone, show, that if the 

 pulses could be rendered sufficiently powerful, it would 

 be difficult to fix a limit to human hearing at either end 

 of the scale. M. Savart had a wheel made about nine 

 inches in diameter with 360 teeth set at equal distances 

 round its rim, so that while in motion each tooth suc- 

 cessively hit on a piece of card. The tone increased in 

 pitch with the rapidity of the rotation, and was very 

 pure when the number of strokes did not exceed three 

 or four thousand in a second, but beyond that it became 

 feeble and indistinct. With a wheel of a larger size a 

 much higher tone could be obtained, because the teeth 

 being wider apart the blows were more intense and 

 more separated from one another. With 720 teeth on 

 a wheel thirty-two inches in diameter, the sound pro- 

 duced by 12,000 strokes in a second was audible, which 

 corresponds to 24,000 vibrations of a musical chord. So 

 that the human ear can appreciate a sound which only 

 lasts the 24,000th part of a second. This note was dis- 

 tinctly heard by M. Savart and by several people who 

 were present, which convinced him that with another 

 apparatus still more acute sounds might be rendered 

 audible. 



For the deep tones M. Savart employed a bar of iron, 

 two feet eight inches long, about two inches broad, and 

 half an inch in thickness, which revolved about its center 



