18 



ANIMAL MECHANICS. 



two groups, which have fixed upon CCC and DDP, respec- 

 tively, as the note of their susurrus — that is to say, two octaves 

 below bass C and D. 



3i 



These notes are found on the new pianos only ; and several of 

 my friends informed me that the C or D, the lowest on their 

 piano, was an octave above the susurrus ; but, on inquiry, 

 there was no difficulty in ascertaining what note was really 

 indicated. The tuning of the pianos was carefully tested with 

 a standard CC diapason, of 64 double vibrations per second, 

 used for acoustical experiments, and corresponding with 4265 

 vibrations in the second for the note, treble A. 



i 



Four of the observers, of whom two were ladies, found CCC, 

 and five, of whom three were ladies, found DDD, which notes 

 correspond, respectively, to thirty-two and thirty-six vibra- 

 tions in the second. 



To my own ear, the susurrus has constantly the sound 

 of CCC ; and the tinnitus had, on the morning of 30th June, 

 1862, the sound of the octave above treble C, that is to 



it was ^1 



l* five octaves above the susurrus, 



and therefore corresponding to a rate of vibration thirty-two 

 times faster than that of the muscle, or 1024 times in the 

 second.f 



* This is the note given out by a well-formed hand bell, of four inches di- 

 ameter. 



f Although the tinnitus aurium is caused by the molecular vibrations of the 

 nerve particles, and takes its note from them, yet I believe it to be influenced by 



