MUSIC AND SOUND INSTRUMENTS 



433 



shape, a hard substance must be made. The soft wax is copper 

 plated, the plate taking all the impressions which were made on 

 the soft wax. Duplicates of this plate are now used to stamp 



FIG. 323. FIG. 324. 



FIG. 323. A diamond point for the reproducer. 

 FIG. 324. A needle attached to the reproducer. 



Courtesy of Scientific American. 



or print records in material which is warm and soft, but which 

 upon cooling will become very hard. 



Records look like rubber, of which they were originally made, but 



FIGS. 325. and 326. The figure at the left shows a new steel needle. The 

 figure at the right shows a steel needle used once (magnified 25 times). 

 Why must the needle be changed for each time a record is played? Area 

 of needle-end is 36000 sq. in. (average). About 5-5-0 of the thickness of 

 the needle is worn off for a large record. Notice the knife-edge, which 

 will do a great deal of harm to a record. 



Courtesy of 'he Scientific American. 



are now made from "mud." Shellac, china clay, talcum powder, 

 coloring matter, barium, asphalt and cotton flock are the prin- 

 cipal materials used in making a record. Some manufacturers 

 use earth, rotten stone, powdered silica, and metallic oxides. 



