In his earliest consideration of the problem of subdividing the electric current, he had decided that the only possible solution lay in the employment of a lamp whose incandescing body should have a high resistance combined with a small radiating surface, and be capable of being used in what is called "multiple arc," so that each unit, or lamp, could be turned on or off without interfering with any other unit or lamp.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin
An artificial compound of one kind or another has indeed been universally adopted for the purpose by all manufacturers; hence the incandescing conductors in all carbon-filament lamps of the present day are made in that way.
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin
Nov 23, 1880 239,149 incandescing Electric Lamp .
"Edison, His Life and Inventions"
Frank Lewis Dyer and Thomas Commerford Martin