When Thomas Edison was born in Ohio in 1847, local transportation was horse-drawn, inter-city railroads were new, and oil lamps or sometimes gaslights were used for illumination. At the end of his life in 1931, public transportation included the automobile and the airplane and there was widespread availability of electric power. Edison's innovative approach to invention propelled the development of the electric light plus the generation and distribution system to make it work.
Edison improved upon previous designs to produce the first reliable, commercial electric light bulb. The basic design was a sealed, evacuated glass bulb containing a filament connected by wires to an outside source of electric current. By devoted effort, Edison and his team solved problems with the filament material and improved the vacuum quality, preventing the presence of oxygen that would cause the filament to burn up at the high temperature created by the electric current. The best filament material needed to have high durability for long bulb life and high electrical resistance to provide the brightest light with the least required electrical consumption.
Over a two-year period, Edison tested thousands of filament materials from the prosaic (metals) to the exotic (tropical vegetation) in a worldwide search. A coiled carbon filament is shown in his landmark invention, named the Edison Incandescent Lamp and given U. S. Patent No. 233,898 on January 27, 1880. The final result was an inexpensive, easily manufactured 16-watt lamp bulb running on DC current for up to 1500 hours.
R.B. Owens Letter (1.6M)
To Wikoff Smith, Pointing out problems in the diploma engraving proof, 4/29/1915