[D8734AAK], Letter from Dyer and Seely to Edison Lamp Co, April 12th, 1887

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Title

[D8734AAK], Letter from Dyer and Seely to Edison Lamp Co, April 12th, 1887

Editor's Notes

Enclosed with D8734AAJ. "In answer to your letter of the 7th inst., we have to report as follows: ## The method of joining the carbon filament of an electric lamp to the leading in wires, by electrically heating the parts while they are immersed in a hydrocarbon fluid, either a liquid or a vapor, seems to be fully covered by the United States patent to J. W. Swan, No. 260,235, dated June 27th, 1882. This was patented in England by patent No. 4202 of 1881. ## The patent has broad claims for the process, and for the lamp having its wires and filament so united. ## As to the validity of the patent we of course cannot give a decided opinion without making an examination into the prior state of the art. We have however, understood that Mr. Edison employed the process before the date of the Swan patent. What Mr. Edison did was to form enlarged ends of carbon filaments by a carbon deposit while the ends were electrically heated. In doing this he, necessarily as we understand, joined by the deposit the ends of the filament to the wires which conveyed the heating curren to it. This is shown in Mr. Edison's patent No. 239,151, dated March 28th, 1881. In the process described in this patent the wries and filament are held in a support, and after the enlarged ends are formed the filament is removed from the wires, by breaking it off. But Mr. Edison has said that he did the same thing with the ordianry inside part and leading in wires of a lamp, in which case the filament was of course left in connection with the wires and the whole placed as usual in a lamp globe. What Mr. Edison used a carbon vaopr, but Swan's patent describes the use of both liquid and vapor and his claims cover both. ## This, in our opinion, was a clear anticipation of Swan's claims, but whether it could be used with effect against the Swan patent would depend upon what testimony could be brought to prove the facts. If it can be clearly proved that Mr. Edison did what we have above described, we think you have nothing to fear from the Swan patent. ## You ask us also as to how this matter stands in other countries. In England we suppose Swan's patent is owned by the Edison-Swan Company. ## As to other countries we can only say that Edison has no patents upon it. Whether or not Swan has could probably be determined by investigation.

Recipient

Date

1887-04-12

Type

Folder/Volume ID

D8734-F

Microfilm ID

119:971

Document ID

D8734AAK

Publisher

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