NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



49 



up if the slightest trace of oxygen were present, so he heated the 

 lamp while it was still on the exhaust pump after a high degree of 

 vacuum had been obtained. This was accomplished by passing a 

 small amount of current through the " filament," as he called it, gently 

 heating it. Immediately the gases started coming out, and it took eight 

 hours more on the pump before they stopped. The lamp was then 

 sealed and ready for trial. 



On October 21, 1879, current was turned into the lamp and it 

 lasted forty-five hours before it failed. A patent was applied for 



Demonstration of Edison's Incandescent Lighting System. 

 Showing view of Menlo Park Laboratory Buildings, 1880. 



on November 4th of that year and granted January 27, 1880. All 

 incandescent lamps made today embody the basic features of this 

 lamp. Edison immediately began a searching investigation of the best 

 material for a filament and soon found that carbonized paper gave 

 several hundred hours life. This made it commercially possible, so 

 in December, 1879. it was decided that a public demonstration of his 

 incandescent lighting system should be made. Wires were run to 

 several houses in IMenlo Park, N. J., and lamps were also mounted on 

 poles, lighting the country roads in the neighborhood. An article 

 appeared in the New York Herald on Sunday, December 21, 1879, 

 describing Edison's invention and telling of the public demonstration 

 to be given during the Christmas holidays. This occupied the entire 

 first page of the paper, and created such a furor that the Pennsylvania 

 Railroad had to run special trains to Menlo Park to accommodate 



