THE EDISON PHONOGRAPH 



were projected into the upper end of the cylinder the 

 vibrations thus set up caused the diaphragm to vibrate 

 back and forth. This vibration, producing upward and 

 downward movements of the needle, caused it to make 

 indentations on the rotating cylinder of tin-foil be- 

 neath, recording precisely the vibrations made by 

 the sounds in the cylinder. These sounds could then 

 be reproduced by setting back the cylinder and rotating 

 it at the same rate of speed as before, causing the 

 needle to pass over the indentations in the grooves made 

 while recording, thus reproducing the vibrations of the 

 diaphragm. This was the principle of Edison's first 

 phonograph, and this is the underlying principle of his 

 own later perfected instruments as well as of all other 

 forms of "talking machines," although the details of 

 the operating mechanism have been greatly modified. 



Between 1877 and 1888 Edison was constantly ma- 

 king improvements in his invention until he had per- 

 fected the phonograph practically as we know it to-day. 

 In the newer instruments the parchment diaphragm 

 of the older instrument has been replaced by a thin 

 glass plate; and the cylinders are no longer made of 

 tin-foil but of a dark-brown waxy substance familiar 

 as phonograph "records." Clockwork or electricity 

 has been applied for rotating the cylinder, so that the 

 old winding movement of the crank is now done 

 mechanically. 



A great improvement has been made in the pointed 

 marker or recorder, and the corresponding instrument 

 for reproducing the records. In place of the steel 

 needle used on the first instruments, the marker is now 



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