Beschreibung:

EDISON, Thomas Alva (1847-1931). Autograph letter signed ("T.A. Edison"), to Isaac Norris of the Franklin Institute, Philadelphia; Menlo Park, N.J., 22 January 1880. One full page, large 8vo, on lined "T.A. Edison" stationery. Boldly signed, with a dramatic "umbrella" signature. Fine condition. A MONTH AFTER HIS SUCCESSFUL TEST OF THE ELECTRIC INCANDESCENT LAMP A polite letter from the young inventor, who had just, after 14 months' unsuccessful experiments, perfected a workable incandescent light bulb, which was successfully demonstrated in the Menlo Park lab less than a month before, on 31 December. The letter is likely to embody one of Edison's first references in correspondence to the invention. Norris, associated with the Franklin Institute, had clearly expressed interest in obtaining a prototype of Edison's revolutionary electrical device. Edison writes: "Your letter as well as one from Mr. Outerbridge was received but was slipped in with many other letters, and in working off the pile tonight I came across them when it was too late to comply with your requests. In a short time I shall have a supply of lamps, and can spare one or more better than now..." The incandescent lamp, as Edison conceived it, was not merely a new application of electrical science and engineering, but was intended to be commercially viable and ultimately, to replace the existing system of gaslights. It required a new type of circuit (parallel circuitry), special safety devices and a constant voltage dynamo. The final breakthrough was the discovery of the carbonized cotton filament, first tested on 21 October 1879. Edison applied for a patent on the carbon filament lamp on 1 November, and it was granted 5 days after the present letter. At this early date, Edison possessed a single generator and a few dozen working lamps. "It was not the 'first' electric light, nor even the first incandescent electric lamp. It was the first practical and economic electric light for universal domestic use...It opened the way to the electrification of men's dwellings throughout the world and introduced the large-scale production and sale of electric power itself." Jacobson, Edison , p.222 and Chapter, "The Breakthough."