254 



PHYSIOLOGY 



CHAP. 



agreeable uniform perceptions are combined. But it cannot be 

 denied that the euphony, the sweetness or harshness, of the chords 

 are influenced not only by the degree of fusion, but also by the 

 different quality and colour of the concurring tones and the 



Augd. Fourth 



7 :5 

 c sharp - - 



FIG. 102. Optical images of five intervals arranged in order of decreasing consonance. (Zambiasi.) 

 The vibrations of the two tones were combined vertically to obtain Lissajou's figures ; these 



were traced by a luminous point on a sensitive plate moving uniformly at such a rate that the 

 entire course of the curve was traced in one-tenth of a second. The tones were produced by 

 the vibrations of two tuning-forks, one of which had a small aperture brightly illuminated by 

 the sun, while the other had a lens through which the image of the slit was projected on to 

 the photographic plate. 



number of the resultant beats. It is thus easy to explain why 

 the three notes, c, e, g, which are partial tones of one and the same 

 fundamental note, and have no beats, form the most harmonious 

 and perfect chord. 



