SOUND AND HEARING 275 



4. 1803 : 343-344. Sources of Sound. 



5. 1803 : 351-352. Musical Sounds and Noises. 



a. 1506 : 241-244. The Sense of Hearing the Ear. 



6. 1507 : 362-373. The Ear and Sound. 



c. 1509 : 252-256. Hearing and Sound. 



d. 1801 : 140-152. Sound ; its Transmission and Velocity. 



e. 1804 : 186-197. Origin of Sound and its Transmission. 

 /. 1805 : 169-180. Waves Sounds ; its Transmission. 

 g. 1805 : 192-195. Characteristics of Sound. 



h. 1806 : 441-444. Sound ; its Sources and Transmission. 



i. 1808 : 163-165. The Nature of Sound. 



j. 1808 : 180. Properties of Musical Tones. 



Experiment 90. The Origin of Sound. Music. 



Apparatus: A vise or clamp, piece of clock spring, pins, 

 hammer, piece of wood. 



a. Fasten the piece of clock spring in the vise so that a six- 

 inch section of it is free to move. Cause it to vibrate. Does 

 it produce a musical tone? Shorten the free end of the spring, 

 and vibrate again. What is the result? Continue to shorten 

 the spring. What happens, and what is the final result? 

 What is the origin of sound? 



6. Drive a pin into a piece of wood, and make it vibrate. 

 Note the tone. Now drive another pin a little deeper into 

 the wood, trying to cause the pin to give forth the . next 

 higher note in the ordinary musical scale. In this manner 

 drive six more pins, completing the scale. 



c. After the practice in (6) try driving in a row of pins 

 which will play some simple air when they are caused to 

 vibrate in succession. 



Experiment 91. The Megaphone and Mechanical Tele- 

 phone. 



Apparatus: Two tin vegetable cans, or baking powder tins, 

 string, brass rivets for paper, scissors. 



