ON BEATS OF IMPERFECT HARMONIES. 409 



Koenig's tuning-forks are much superior to Mar- 

 loye's, because of the greater quantity of metal in 

 each fork, in virtue of which it gives a louder and 

 more enduring sound. The sound proceeding 

 from such a source is essentially a simple tone, 

 or very nearly so. I have tested that in every 

 case the number of beats counted is the smallest 

 that could be according to the preceding theory ; 

 for it is to be remarked that the theory only gives 

 the whole period of the phenomenon, but does not 

 answer the question Does the ear perceive a 

 gradual variation of quality through the whole 

 period, or does it fail to distinguish the difference 

 of quality between two halves of the period, or 

 between three-thirds of it, and so on ? My ex- 

 periments demonstrate that in every case the ear 

 does distinguish the two halves of the period of 

 each beat. Thus, for example, in the beat on an 

 approximation to the harmony (1:2) in which the 

 variation of air-pressure on the ear is represented 

 by the preceding curves l for four instants of the 

 period noted, I find that the ear distinguishes the 

 1 Sec page 401. 



