THE EAR. 501 



its unbroken glassy surface like a bulged mirror, to the 

 ploughed, choppy waves of the English Channel or Irish 

 Sea. He has noticed how the surface of a big wave is 

 sometimes covered with smaller waves, and these individual 

 smaller waves, in turn, roughened with ridges upon them. 

 It is not difficult to see how the form of a wave on L,ake 

 Michigan might differ materially from the form of a wave 

 on another body of water, even though the height of the 

 waves and the lengths of them be the same. This differ- 

 ence in form produces the quality of the wave, and if we 

 had special senses to take cognizance of such water waves, 

 probably one would have no difficulty in distinguishing be- 

 tween a Lake Michigan wave and a wave from the Gulf of 

 Mexico, or another from the middle of the Atlantic. 



Leaving this analogy and defining quality in the terms 

 of sound waves it is this: The quality of the sound de- 

 pends upon the number of secondary waves or secondary 

 sounds which are super-imposed upon the first fundamental 

 wave or sound. This was conclusively shown by the ex- 

 periments of Helmholtz, who, by means of properly com- 

 bined tuning-forks was actually able to produce the qual- 

 ities of different instruments. To use the analogy of light, 

 quality would be produced by taking a fundamental color 

 and then tinting or shading that color within narrow limits 

 by the addition of secondary colors. If, therefore, the 

 quality of a sound is due to its compounding, the question 

 naturally arises, what would be the quality of a sound per- 

 fectly pure without the admixture of secondary waves. 

 Such sounds are produced with relative purity by tuning- 

 forks, and any one who has heard a high-grade tuning-fork 

 must have been struck by its mellow, pure, unmixed qual- 

 ity. If, now, to such a fundamental pure sound other 

 tuning-forks in varying strength and of proper pitch be 

 added it would be possible to reproduce the piano note, or 

 tone of the violin, and we may add even the quality of the 

 human voice. 



