n the year 1882, Edwin A. Scribner, assignor to the United States Electric Lighting Company, applied for, and was issued, a patent for a carbon filament incandescent lamp with a chlorine addition. The drawing of the lamp, scanned from the patent, is shown to the left. The filament design, in the shape of the letter "M", is that due to Hiram S. Maxim. The patent granted to Scribner is dated March 7, 1882 and numbered 254,780. In Scribner's words:
"When electric lamps containing a stem of carbon in a vacuum receiver are rendered incandescent it is found that the interior surface of the globe becomes clouded by a thin deposit, which disfigures the lamp and intercepts a great part of its light. I have found that under certain conditions the presence within the globe of chlorine effectually prevents this clouding, this being probably due to a chemical combination, under very high temperatures, of chlorine and carbon protoxide, resulting in the formation of a vapor or liquid rather than a solid deposit. The conditions under which this result is best attained are that the globe should contain no atmospheric air and only a very small quantity of chlorine, and in order to obtain these conditions at least approximately, the following is the method pursued.
"It is usual to attach a number of lamps to the same exhaust apparatus and to exhaust them simultaneously. To the same apparatus, and in direct communication with the lamps, a small retort capable of being filled with pure chlorine gas is also attached, and provided with a stop-cock, by which communication with the lamps may be shut off. This retort being filled with chlorine and disconnected from the lamps, the latter are exhausted of air as completely as possible, when the stop-cock is opened and the gas allowed to enter the lamps. By the diffusion of the gas the lamps become filled with an attenuated atmosphere of chlorine, and in this condition they are tested and sealed.