Prof. A. M. Mayer's Researches in Acoustics. 519 



loaded and when the wax was removed. This fact I have 

 repeatedly confirmed by testing the intensities of the two 

 sounds by different hearers who were placed so that they could 

 not see when the fork was loaded or unloaded. Now E. H. 

 Weber has found that only the most accomplished musical ears 

 ean distinguish between the pitch of two notes whose vibrations 

 are as 1000 to 1001 ; but by the above method we can readily 

 detect a departure from unison in the two notes amounting to 

 the interval of 2000 to 2001, or to the T Jg- of a semitone. 



In connexion with the preceding observations the following 

 experiments on resonators and sympathetic vibrations may be of 

 interest. I substituted for the ear the manometric flames of 

 Konig, viewed in a revolving mirror, and tested the response of 

 the resonators to sounds not in accord with their proper notes. 

 The results agreed with those previously obtained on placing 

 the resonator to the ear. I now mounted an Ut 3 fork on its 

 resonant case ; and sounding it strongly before all the resonators 

 of the harmonic series of Ut 2 , I caused all the manometric 

 flames connected with these resonators to vibrate, each giving 

 the same number of serrations as when the Ut 3 fork was brought 

 near its own resonator. The same result was obtained when 

 the fork was separated from its case, with this important differ- 

 ence, however, that when the face of fork Ut 3 was brought near 

 the mouth of the Ut 4 resonator, the flame connected with this 

 resonator gave at the same time serrations belonging both to 

 Ut 3 and to Ut 4 ; and this result accords with the following 

 experiment. If one sounds the Ut 3 fork on its box, and 

 brings the mouth of the latter near the mouth of the box of the 

 Ut 4 fork, the Ut 4 fork will covibrate ; and after Ut 3 has ceased 

 to vibrate, Ut 4 will sound out quite clearly. If, however, Ut 4 

 be lowered in tone by weighting it with a piece of wax so that 

 it gives two beats per second with its proper tone, then the 

 Ut 4 fork cannot be set into sympathetic vibration by impulses 

 from Ut 3 . Also if forks Ut 3 and Ut 4 be detached from their 

 boxes and fork Ut 3 be strongly vibrated while the face of 

 one of its prongs remains quite close and parallel to the face of 

 a prong of fork Ut 4 , the latter is set in vibration by the im- 

 pulses of Ut 3 sent through the intervening air. Fork Ut 3 was 

 now loaded so that it successively made 1, 2, 3, and 4 beats per 

 second with the true Ut s pitch. When it made 3 beats per 

 second, it caused Ut 4 to vibrate so feebly as to be barely audible, 

 while 4 beats per second departure of Ut s from unison produced 

 no effect on Ut 4 . 



The following experiment was now made to show the want of 

 precision in the determination of the exact pitch of sonorous 



