THE CARBON BUTTON. 



19 



ing drawing and description, given with the sanction and approval of 

 Mr. Edison, the writer is indebted to the courtesy of Mr. S. D. Mott, 

 of Edison's laboratory : 



" The course and action of the currents in Edison's loud-speaking 

 telephone are as follows : Reference is made to the accompanying dia- 



FlG. 5. 



