[LB007487], Letter from Thomas Alva Edison to Edison Electric Light Co Ltd, Arnold Henry White, June 15th, 1882


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[LB007487], Letter from Thomas Alva Edison to Edison Electric Light Co Ltd, Arnold Henry White, June 15th, 1882

Editor's Notes

I have received Mr. E.H. Johnson's letter of 27th ult inclosing five English patents marked to [short] the disclaimers which it is proposed to file. I understand from Mr Johnson's letters that when this reaches you, the disclaimer will have been already filed, but may be withdrawn and amended if I find that any point of primal importance has been overlooked.##The following will show my news upon this matter.##[--] 578 [dated 10th --- may] 1880.##The proposed disclaimer in this case has my approval, with the exception of the excision of the fifth (5th) claim. This I think a mistake of grasve importance, since a lamp of this character is in the direction of future improvement in the art of lighting by electrical incandescence. am working on lamps of this [kind] myself. The use of several separate carbon [conductors] connected in series in one lamp. I am quite sure is new, and it is certainly very useful. The [current] [of] [generator] or invention would seem to be sufficient when we consider that to make such a lamp successful the process of manufacturing incandescing carbon conductors must have reached such a state of perfection that all the conductors will have the [same] resistance and radiating surface, and will require the same number of volts to process a certain degree of incandescence. This is a difficulty which is met with when carbon conductors or lamps are connected in series and does not apply to conductors or lamps worked in multiple arc.##Lamps may vary in radiating surface [----] resistances but if they give the same light at the same volts they may be worked in multiple arc. This is not so however with lamps in series since these same lamps that would give the same candle power at certain volts in multiple arc will show great differences in series, and while one may be at normally high incandescence another lamp may only give a candle of light. This imperfection in carbon conductors would greatly diminish the life of a lamp having several conductors in series, and if insurmountable, would make such a lamp very imperfect and practically valuless.##My prior patents however show how this can be done, and explain the proper methods and materials for producing practically perfect carbon incandesing conductors This patent then would be tributory to them.##The following furnishes a good illustration of the practical difficulty of working carbon incandescing conductors in series before refined to##If we had, for instance 2 lamps each giving 16 candles at 100 volts; one might have a resistance of say 100, while the other light have a higher resistance, say 100 ohms, but a smaller radiating surface, to compensate for the [lessened] energy there to the higher resistance. If these two lamps were put across multiple arc, both would give 16 candles, but the 100 ohm lamp would require, in round numbers, 4400 feet lbs, and the 110 ohm lamp only 4000 ft lbs. Now, it will be seen, that, if it is attempted to put these two lamps in series with a pressure of 200 volts on the line, the 100 ohm lamp will only get 4000 ft lbs and hence will not give 16 candles, while the 110 ohm lamp will get 4400 ft lbs, or 400 ft lbs more than is necessary to give 16 candles.##In view of the facts I have stated, I think it will be found that the invention set forth in the 5th claim is supported by sufficient in-[--gem-tes] to make the claim a valid one.##The 6th. claim stands somewhat although not as strongly upon the same footing. However the device set forth in that claim is not in my opinion wholly practicable, and I do not therefore ask that this claim be retained.##If the 5th claim is retained, I think the following should be the only matter erased on 5th page of specn. In line 9. [evase] words "I have discovered that"; also [evase] commencing with words "In one form" in 26th line, through the 31st line On 7th page [evase] sentences commencing on 5th line, and insert "Figures 6, 7 and 8 show a lamp in which the resistance is increased by the use of several incandescent arcs in series." On same page, evase commencing with 20th line through word "half" in 30th line.##No 1385, dated 5th April 1880.##On going over the whole ground in this case, I cannot see that any serious mistake has been made. As I understand, plates have been used in the core of the Gramme machine, but since the claim retained is specific in its nature I think it should hold. the U.S. Patent Office [refemeous] in this connection to [Douglass'] Polytechnuclus Jurnal vol. 22[3] pp. 587 and 588. Whether this Journal formed a publication in England or not of course I do not know, but I wish to call your attention to the matter so that you will have all the light that can be known upon the subject.##No. 3880 dated 24th September 1880. I am satisfied with the claims that one retained in this case. I wish however to call your attention to the 11th and 12th claims which have been erased. The 9th and 10th claims (both retained) cover the construction shown in figures 16 and 17, while the 11th and 12th claims cover that shown in [figures] 18 to [21] inclusive. From the fact that the [description] of figures 18 to 21 is allowed to remain, and that no objection hs been advanced to the 11th and 12th claims, I am led to believe that it was not intended to [erase] both of those claims, but that the 9th and 11th or the 10th and 12th were intended to be cancelled. If that is so, I would prefer to retain the specific claims, the 10th and 12th.##On 7th page of the specification don't you think the words "or feeding" should be inserted before "conductor" in the sentence inserted in 14th line?##No. 3964, dated [30th] September 1880.##It strikes me that claim 7 might remain in as a feature of the steam dynamo. The claim is a limited combination, the essential feature of which is the non-magnetic supports. If it is retained the specification (pp. [98--]) should be amended somewhat differently from what is is marked.##I would like very much to see the 6th and 9th claims of this patent maintained, since they cover a highly important, and, in my opinion, novel construction; but my views on this subject having been fully considered, I cannot do otherwise than submit to the judgment of the legal advisers of the Company##No. 7 & 8, dated 23d February 1881.##In this case, I see nothing to change in the proposed disclaimer.




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