86 



ON THE PHYSIOLOGICAL CAUSES OF 



different lengths. The longest of these simple waves 

 has the same length as that of the given form of wave, 

 the others have lengths one-half, one-third, one-fourth, &c. 

 as great. 



By the different modes of uniting the crests and 

 hollows of these simple waves, an endless multiplicity of 

 wave-forms may be produced. 



For example, the wave-curves A and B, Fig. 9, represent 

 Fig. 9. 



.^4 



waves of simple tones, B making twice as many vibrations as A in 

 a second of time, and being consequently an octave higher in pitch. 

 C and D, on the other hand, represent the waves which result 

 from the superposition of B on A. The dotted curves in the 

 first halves of C and D are repetitions of so much of the figure A. 

 In C, the initial point e of the curve B coincides with the initial 

 point do of A. But in D, the deepest point bg of the first hollow 

 in B is placed under the initial point of A. The result is two 

 different compound-curves, the first C having steeply ascending 



