THE COMPOSITION OF MIND 



scious sensations by the compounding of un- 

 conscious or sub-conscious psychical changes, but 

 in every sensation of sound, colour, odour, taste 

 or touch which the adult receives, there is a 

 precisely similar formation of a conscious state 

 by the compounding of unconscious or sub-con- 

 scious psychical states. In the case of sound, 

 the evidence for this statement amounts to com- 

 plete demonstration ; the evidence is hardly less 

 strong in the case of sight ; and in the case of 

 the other senses, all the evidence thus far ob- 

 tained points toward the same conclusion. Let 

 us first examine the composition of a sensation 

 of sound, as admirably elucidated by M.Taine 

 in his recent treatise on "Intelligence." 



In musical sounds three characteristics are to 

 be distinguished — loudness, pitch, and quality 

 or timbre. The first of these, the loudness, de- 

 pends upon the amplitude of the atmospheric 

 waves by which the sensation of sound is caused. 

 A series of sound-producing waves, like any 

 other series of waves, has its elevations and de- 

 pressions, and the height of the elevation above 

 the depression is called the amplitude of the 

 wave. The loudness of the sound varies as the 

 square of the wavers amplitude. From this it 

 follows that every elementary sound has a period 

 of minimum intensity, answering to the wave's 

 minimum amplitude when it is just beginning 

 to rise ; secondly, a period of maximum inten- 

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