14 



THE PHILOSOPHY OF BIOLOGY 



physical cause of the increasing loudness of the sound 

 by space-magnitudes, and then we transfer these 

 magnitudes to the states of consciousness concomitant 

 with the vibrating molecules of air. Suppose that we 

 knew nothing at all about the cause of the differences 

 of pitch of musical sounds and that we listen to the 

 notes of the octave, C, D, E,- -C, sounded by an 

 organ ; all that we should experience would be that 

 the sounds were different. If we were to sing the 



notes we might 

 attain the intui- 

 tion that the 

 notes G, A, B were 

 "higher" than 

 the notes C, D, E, 

 because a greater 

 effort was re- 

 quired in order 

 to produce these 

 sounds, but ob- 

 viously this 



FIG. 2. 



is 



a different thing 



from saying that 



the notes themselves were ' higher ' or ' lower." 

 But let us match the notes by striking tuning-forks, 

 and then having selected forks which give the notes 

 of the octave let us fix them so that they will 

 make a tracing, while still vibrating, on a revolving 

 strip of paper. We shall then find that the fork 

 emitting the note C makes (say) 256 vibrations per 

 second, the fork D I 256 vibrations, the fork E 

 I 256 vibrations, and so on. Thus we associate the 

 notes of the octave together and we say that their 

 quality was the same but that their pitch differed, 

 and since the pitch depends on the frequency of 



