354 Prof. A. M. Mayer's Researches in Acoustics, 



ear. I now replaced the Ut 2 resonator and fork by an Ut 4 reso- 

 nator and its corresponding fork, and again rotated the disk 

 with the same velocity that it had during the above-described 

 experiment. In these circumstances I no longer experienced a 

 continuous sensation, but one which reminded me somewhat of 

 the clatter of frogs in a marsh, This fact at once showed that 

 a greater number of beats per second were required to blend the 

 separated pulses of a sound of higher pitch ; and this blending 

 I actually obtained on sending into my ear abou£ one hundred 

 beats per second of Ut 4 . 



I now prepared a series of disks adapted to four octaves of 

 resonators and forks, and made many experiments to determine 

 the durations of the residual sonorous sensations of several simple 

 sounds — Utj of 64 vibrations per second being the lowest note of 

 the series, and the highest being Ut 5 of 1024 vibrations. I was 

 not able to use an Ut 1 fork and resonator; so I substituted for the 

 former an Utj closed wooden organ-pipe, gently blown, and for the 

 latter a small funnel of gutta percha, whose mouth was placed 

 close to the perforated disk, while a rubber tube connected the 

 funnel with the ear. I will here remark that in some series of 

 experiments the resonators were replaced by this funnel of gutta 

 percha, and the determinations thus made were the same as 

 those reached by the use of the resonators. 



The above-mentioned determinations I published in the Ame- 

 rican Journal of Science for October 1874, and embraced them 



in a law which has for its expression D = ( -^ — — + 24 j'OOOl, in 



which D equals the duration of the residual sonorous sensation 

 corresponding to N number of vibrations per second. 



The precise determinations of the durations of the residual 

 sonorous sensations are difficult, by reason of the complex cha- 

 racter of the sound perceived when vibrations of a tuning-fork 

 are sent intermittently into a resonator by means of a revolving 

 perforated disk ; and the difficulty of the determinations is in- 

 creased by the fatigue and deadening of the ear, caused by the 

 beats which enter it from the resonator. 



The important applications of this law in the physiology of 

 audition and in the elucidation of the fundamental facts of mu- 

 sical harmony, demanded that I should have my determinations 

 reviewed by ears more highly cultivated than mine in the appre- 

 ciation of pitch and of musical intervals, and more skilled in the 

 direct oral analysis of composite sounds into their simple tones. 

 Since my publication in October 1874, I have had the good 

 fortune to elicit in Madame Emma Seiler, and in her son 

 Dr. Carl Seiler, a profound interest in my researches. They 

 have spent considerable time in the redetermination of the dura- 



