THE PHONOGRAPH 



305 



against a delicate disk and throws it into vibration, and the 

 metal point attached to it traces on the wax of a moving 

 cylinder a groove of varying shape and appearance called 

 the " record." Every variation in the speaker's voice is 

 repeated in the vibrations of the metal disk and hence in the 

 minute motion of the pointer and in the consequent record 



FIG. 196. A phonograph. 



on the cylinder. The record thus made can be placed in any 

 other phonograph and if the metal pointer of this new phono- 

 graph is made to pass over the tracing, the process is reversed 

 and the Speaker's voice is reproduced. The sound given out 

 in this- way is faint and weak, but can be strengthened by 

 means of a trumpet attached to the phonograph. 



CL. GEN. SCI. 20 



