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of the three pairs of muscles upon the direction of the pip 

 or pupil. 



II. Can Double Vision be produced when the Eyes move 

 freely together? 



METHOD. Set up a stick vertically about 3 feet from the 

 eyes, and another at about 10 feet. Look at the near one 

 and see what happens to the image of the far one. Close one 

 eye and observe what happens. Now look at the far one and 

 notice the image of the near, and again close one eye. Make 

 a diagram of the experiment, and explain the result. 



V. HEARING. 

 Revise your knowledge of the physics of sound vibrations. 



I; What Qualities of Sounds are perceived ? 



1. Loudness. 



2. Pitch. Is the perception of pitch limited ? Using 

 tuning forks for the lower limit and the steel cylinders supplied 

 for the upper limit, determine the range of perception of 

 musical sounds. 



3. Quality, (a) Sound the tuning fork Ut 4 strongly, and 

 note the character of the resulting sensation. 



(6) Repeat the experiment, and immediately after sounding 

 the fundamental tone, sound the three partials me, soh and 

 doh above, and note the character of the resulting sensation. 



Formulate your conclusions as to the influence of overtones 

 upon the quality of musical tones. 



II. Do Sound Vibrations influence the Internal Ear only through 

 the External? 



METHODS. Sound a tuning fork lightly, and hold it to 

 the ear until the sound has quite died away. Now place the 

 end of the fork against the closed teeth. Describe the resulting 

 sensation. What CONCLUSION do you draw ? 



