ADVANCED EXPERIMENTAL PHYSIOLOGY 387 



EXPERIMENT II. Take two tuning-forks which produce beats when 

 simultaneously caused to vibrate. Place one at such a distance from 

 the ear that it can scarcely be heard. Bring the other fork gradually 

 closer to the ear and the beats will be recognised. 



6. Compound Tones. The tones produced by musical instruments 

 are not simple tones, but blended with other so called overtones. The 

 lowest tone of the group gives the fundamental tone. 



EXPERIMENT. Stretch a violin string between two fixed points. 

 Set this into vibration by pulling it near one end, and immediately 

 touch it in the centre with the finger. The tone will seem to be pitched 

 an octave higher. The fundamental tone of the original group is 

 obliterated, and the lowest tone now is an octave higher, and thus a 

 new fundamental with other less evident overtones give the tone to the 

 group. 



7. Location of Tones. EXPERIMENT I. Sound a large tuning-fork 

 and press it against the vertex. The sound will appear to come from 

 inside the head. Then close one ear, and the sound will seem to be 

 localised in the other ear. 



EXPERIMENT II. Sound a tuning-fork as above and note the effect 

 of placing it on different parts of the head. 



EXPERIMENT III. Sound a tuning-fork and let its foot rest upon the 

 teeth. Close one ear and localise the apparent change in position of 

 the sound. 



