[LB011001], Letter from Thomas Alva Edison to Edward Hibberd Johnson, January 2nd, 1882


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[LB011001], Letter from Thomas Alva Edison to Edward Hibberd Johnson, January 2nd, 1882

Editor's Notes

Your favour of [Dec] [20]th comes duly to hand.##Big Dynamo. It is a great [pity] that Batchelor has not informed me of the fact that the business in the [--- --- ---] brush holder [--- ---] carbonized. We will [enclose] the insulation. The carbonisation [would] not have been due to the heating of the Journals as we had no trouble about that after the first three or four days running. The insulation must have been very thin and [---] [and] oil provided a surface con[dustion] which tended to [-----ance] them.##I do not know whether it is a good plan to run both Dynamos at once. I am under the impression that it would be best to [connect] both dynamos up in such a manner that one only should be doing the work at full speed while the other could be running say [33] revolutions a minute with [dynamo] disconnected and if the one doing the work should break down I think the machine could be disconnected and the wires connected to the other and full speed obtained in something less than 20 seconds, if your man wwere properly trained. This would be such a short stoppage of light that no complaint would arise and it would not be liable to occur very often any way. The reason that the spare Dynamo should be run [slowly] (80 revolutions) is so that you can start up quickly having its cylinders all hot and withouot any fear of [---] You can rely on Hood more than you can on Porter. Porter [set] the valvew on our Engine here and we had to alter them.##I have not heard from Batchelor what he is going to do with his big Dynamo [or [f--] I got no information at all from him. I suppose he [did not] find time to satisfy my curiousity by writing.##We are having the [shacks] made for your telephones. Insull has sent you some more of those Instruction Books##i believe in selling lamps [----] in large quantities a thousand or upwards but you must be careful not to sell them for foreign use as even I have not got patents I have contract for my interests such as my contract with Gouraud.##Patents. In my subsequent patent as to getting the air out of the carbon of course you must read the claim by the specification & when they are [eeen] in that light I do not see that theya re too broad. You say you cannot bring your patent expert to the opinion that the claim for a filament of certain of high resistance is good. Can you bring them to the point of rendering an opinion as to whether a filament carbon for giving light by incandescence placed in a sealed glass chamber from which the air has been [removed] would be a good claim. By [leaving] out high resistance that is to say disclaiming high resistance you would then have a filament of [carbon] in connection with the rest of the claim. In the patent for a [proposed] carbon filed, sometime in Decemer you will notice that I stated that the carbon is flexible. Now there is one point about the English law that I am not certain about i.e. I understand that it is not necessary to make claims that youa re entitled to everything in the specification as long as it conforms to the law and is new & [novel] & useful. Gramms patent has no claims. If this is so then the paper carbon patent would be held to cover a flexible carbon. You say that the reports say that the filament of carbon of high resistance is anticipated in detail in so many directions that there is nothing [---pt] the degree pure & simple for [which] to lay hold of. Now I shuld like to know where a filament of [carbon] of high or low resistance has even been used before my patent. I would also like to know whether a filament of carbon of high resistance has been used. Also whether a filament of carbon has been used in high vacuo in a chamber made entirely of glass through which platinum wires are secured. I should also like to know if a claim taken not in its broad sense but as a combinatin claim is not good. Combination claims are good even if all the parts are old. You will notice that our claim is really a combinatin claim. I think abandoning all else and seeking only to make good a claim for carbonised fibre is a mistake. While carbonized fibre is the best and would probably how it would let too many people in.##Memo. Be careful and dont disclaim the coil carbon for diminishing the radiating surface as it is on this line that the high resistance lamp will be obtained. [----] I believe can be held against anybody. I think that there is no immediate hurry about bringing any suit; the longer you are at their patent the more thoroughly the experts will get to understand our system and the better the patent will appear. You know that Betts & Dickinson both said at first that we could not claim a difference in degree but after a while when they became more familiar with the results produced by this change in degree their opinion altered and we now have [strong] opinions from them that there is not a shadow of a doubt but that the Court will sustain the patent what I want to know where and by whom before my patent was a a'filamentary carbon for giving light by electrical incandescence in a glass chamber from which the air has been exhausted" used. Now I maintain that if no reference can be found were any person did this before and that I was consequently the first to produce it and it is acknowledged to be useful and great advance in the art of electric lighting then I must be entitled to it. That is to say that I am entitled to a lamp for giving light by incandescence consisting of a filament of carbon in high cacuo maintained under conditions that said vacuo is stable. Filament of carbon might have been produced before: [vacuums] have been produced before but who has used or combined in a vacuum a filament of carbon and I think that the November Patent and the Coiled Carbon is clear and explicit and not complicated. If your people are afraid of the words high resistance why not make the claim thus:##An Electric lamp for giving light by incandescence consisting of a filament of carbon##The second, third, & fourth claims to be the same.##If this patent will not hold as thus amended then it seems to me to be absolutely useless to take out english patents.##I should like to ask if the second patent wherein paper carbon is spoken of and claimed is not good or is it rendered negatoryby the patent of Nov 10th speaking of fibrous material such as paper thread wood &c and if so you would probably have to disclaim claim 1[c]. The third claim ought to be good and is important on account of the broadened ends. The fourth claim does not amount to anything The second claim might be good in so much as it describes a method of carbonizing filament in a definite shape. You are certainly wrong about this fibre claim business Yours would be an excessively narrow view of the matter and could be very readily got around You say that the process as applied to Swan becomes public property when speaking of Swans patent. It may be very clear to you but it is not clear to me why getting air out of carbon by means of Electrical Incandescence in vacuo is thrown open to the public by the actin of a subsequent inventor when another inventor has shown it and claimed it in a patent several months prior Do I understand that the June 79 patent in which a process is described of eliminating the air from carbon by electrical Incandescence in vacuo is public property and invalid. If so is it by reason of prior publicatin of some other inventors an why:!##You say that I clearly set forth the value of high resistane in patent No 5. Hence is Patent no 4 good? If so will not that patent hold a high resistance lamp?##Regarding taking out these patents you know that up to June 1880 Serrell prepared these patents and they were sent to Brewer & Jensen who filed them just as they were received from Serrell, after that Willard prepared the patents sent them to Serrell, who merely copied them and then forwarded them to Brewer & Jensen who filed them. So Serrell is to blame previously to June 80 & Wilbur after. You must consider that owing to the enormous number of applications for patents that to have got the patents in any good kind of shape it would have taken the time of one man continuously. it would have had to have been done on this side because I fail to see how an imperfect application from this side could have been [mdee] perfect by solicitors on the other side who could have no knowledge of the system. However hereafter we will send forward the applications through our person whom you may designate. No improvement however, can be expected in the old way without a man is hired to attend expressly to [letters] to that business.##Can you tell me how to make an inch of platinum wire of a certain size any greater resistance than it naturally is. Is not the resistance of a definite piece of platinum wire always the same. Hence how could one claim, a platinum look of wire of high resistance. Now it is a very easy matter to make an inch of carbon wire of any kind of resistance you want by selecting out a carbonizing material whose cells are either large or small hence it is possible to have a claim on a carbon wire loop of high resistance I merely make this little note just as it comes to my mind as you may possibly be able to make use of this fact. When you speak of my previous patents detailing the necessity of high resistance you are correct. The method however adopted for obtaining the high resistance was not by specifically increasing the resistance of the material or conductor employed but by employing greater lengths of it, while in the carbon patent the claim is for a p[eculiar] kind of carbon that is to say a filament of carbon aggregated together in such a manner that it shall give high resistance.##You say "Had your patent for the application of the process not been
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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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