[D8814AAR], Letter from Charles J Reed to Thomas Alva Edison, January 23rd, 1889


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[D8814AAR], Letter from Charles J Reed to Thomas Alva Edison, January 23rd, 1889

Editor's Notes

If you will place an Edison lamp under mercury and break off the tip, the globe will nearly fill with mercury but will leave a small bubble. You are doubtless aware that this bubble of residual gas is what finally destroys the filament. You are also aware of the great difficulty of its removal. I have recently worked out a process of completely and quickly removing this final bubble and have invented an apparatus to be used in connection with the process, for which I have made application for a patent. The Jenney Co is a small company and the lamp factory (of which I have charge) has a capacity of only about 150 lamps per day. I consider my invention of too much value to give to a small concern and intend to offer it to the highest bidder. What I want is a permanent situation where I can have facilities for pursuing my researches, with a moderate salary and a small royalty on my process. ## I have all necessary formulae, deduced mathematically and proved experimentally for calculating the length and diameter of filaments for any voltage, candle power and efficiency that may be required (the efficiency being an inverse function of the life). Having given a lamp of any candle power voltage and efficiency I can determine with absolute correctness the length and diameter (or area) of the filament to be used for the same efficiency, but to have any required candle power and voltage. ## I am making a filament now which, at a temperature which require only three watts per candle, burns 1000 hours without showing any discoloration of the globe. I inclose for your examination a few filaments and will ask you to hold one of them in a Bunsen gas flame until it shows signs of alterations. ## I can refer you to H. Ward Leonard of Chicago also to Paul D. Dyer of Denver with whom I was once associated as agent for the Edison United Co. [new name mention: The Jenney Co.]




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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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