MUSICAL INSTRUMENTS 



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the Gettysburg address of Lincoln, so that we could listen 

 to the voices of these great men. 



The phonograph was invented by Thomas A. Edison in 

 1877. The first machine consisted of a mouthpiece, across 

 which was stretched a thin membrane, to the under surface 

 of which was attached a sharp point. Just beneath this 

 was a cylinder covered with tinfoil, which was rotated by 

 hand. As one spoke into the mouthpiece, the membrane 

 with the point attached vibrated and the point made inden- 

 tations on the tinfoil beneath. 

 These holes varied according to 

 the intensity of the sound. A 

 loud sound made a relatively 

 deep indentation, while a soft 

 sound made a shallow indenta- 

 tion. When the record on the 

 tinfoil was finished, the point 

 on the membrane was set back 

 on the first part of the groove 

 and the cylinder turned by hand. 

 As this point followed these in- 

 dentations, it reproduced the 

 same vibrations in the membrane 

 that had made the indentations ; 

 and it thus reproduced the same 

 sounds that had been spoken into it. The words first spoken 

 into the mouthpiece by Mr. Edison and first reproduced by 

 the phonograph were the lines of the poem, " Mary had 

 a little lamb." 



Since that time a great many improvements have been 

 made in the phonograph, but the essential principles are the 

 same as those used in that first crude machine. The modern 

 phonograph has a device by which the record is kept rotating. 

 This is usually done by means of a spring which is wound 

 up by a crank on the side of the machine. It is necessary 



To Sounding 

 Chamber 



Soft Rubbe, 

 Kings 



Need/e Point 

 I 



FIG. 37. Section of a phonograph. 



