416 POPULAR LECTURES AND ADDRESSES. 



But the slow beat on the 8, 9, 10 (with vibrational 

 frequencies 256, 288, 320), with an}- one of 

 the three notes slightly flattened, is very re- 

 markable. The sound is like that of a wheel 

 going round with decided roughness of motion 

 in ever}' part of its revolution, but much rougher 

 in one part than another, with a loudly per- 

 ceptible periodic return of the roughness in the 

 theoretical period of the approximate harmony. 



The beats on the harmony C E G (vibrational 

 frequencies 256, 320, 384), with any one of the 

 three notes slightly flattened, arc very perceptible ; 

 untrained ears hear them instantly the first time 

 without any education, and the beat is heard 

 almost to the very end of the sound when three of 

 Kocnig's forks, one of them, the C, for example, 

 being slightly flattened by a brass sliding piece 

 screwed to it, arc excited by the bow to well-chosen 

 loudncsscs, and arc then left free. The sound 

 dies beating, the beats being distinctly heard all 

 through a large room as long as the faintest breath 

 of the sound is perceptible. The smooth melodious 

 periodic moaning of the beat is particularly beau- 



