[LB011276], Letter from Thomas Alva Edison to Edward Hibberd Johnson, February 15th, 1882


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[LB011276], Letter from Thomas Alva Edison to Edward Hibberd Johnson, February 15th, 1882

Editor's Notes

Your letter 16th Jany I now understand the value of claims in English Patent but what you say does not in any affect my agreement at all I only asked about it as a matter upon which I discuss information more particularly with reference to the Gramme patent.##I send you some notes of Dyers relating more particularly oscluded gas taken out of carbon in vacuuo. You will remember that I used platinum clamps with platinum wire running through glass to connect with the carbon and in subsequent patents you will find that I made special devices to more effectively get the occluded gases out of the clamps then was possible by mere heating. Now you will see that when I bring up one of [--] filaments in vacuuo I heat the carbon to a higher incandescence for the sake of heating the clamps and get out the occluded gases which is especially necessary where metalic plated clamps are used as plated metal has an immense quantity of occluded gases So you see I am still carrying out my first patent in so getting out these gases and the others are infringing this patent as the act of heating up the carbon must necessarily throw out gases from the clamps which then all use and this statement is backing up by my subsequent patent Dyer gives expression to this view in his above referred paper.##with reference to my Patent no 5 as to my using carbon having a specific high resistance I still maintain what I before stated and Dyer has made an argument on this subject which I send you herewith. Of course if the patent can be sustained for a carbon filament having a high resistance as compared to previous statements in this line all right but if not the patent will admit of the other construction. If you will read it again carefully in the light of Dyers argument you will see that it fairly bristles with allusions to the specific kind of carbon of high resistance and that making this kind of carbon into a filament gives a filament composed of carbon of high resistance and that the sailing of the carbon was for an entirely different object; that is to say if the carbon was of very high resistance and made straight there would be such a small mass of matter and such a small amount of energy at any one given second that the slightest change in the strength of the current or at the commutator brushes would cause the loop to show it by vibration of light. That is its mass being so small it would loose its heat almost instantly while if the carbon was made a little more homogenious i.e. made of a little lower resistance a greater length to compensate for this the coiling of the same would keep the radiating surface down and the specific heat of the whole being then raised by increasing the mass it would not be so sensitive to slight changes in the current. You will see that this is clearly set out in the Provisional as well as the final Specification.##It is quite impossible for me to send Dyer over to you as he is attending to all the foreign business & is far more valuable to me here than he would be in England. He is now preparing Foreign Cases which will be sent to you to be filed as a communication from me through the channels you think best. no patent will be sent without pretty good examination of all previous patents by Dyer who has gone over the whole of them and has made a Digest for reference a copy of which is enclosed herewith as it may be useful to you.##Regarding the Radical Bar Disc Dynamo I have the one which was intended for the Paris Exposition just finished. I have not tried it yet. They need not get scared on the Dynamo question. I cabled you several days ago to know whether the Gramme patent in view of the Paccinotti and Elias machines is valued in England.##Please change your [---] on figures 7 7 8 in the English Patent showing the radial bar disc Dynamo which you speak about. Say what you think about Seimens claim for winding [over] the whole of the cylinder. In this patent I neither go over the ends of the cylinder like Seimens or through the cylinder like gramme. I enclose you Dyers report to me as to the Seimens patent. I think you will find that he has made a closer analysis than Hopkinson & that he throws new light uon the subject. I am strongly of the impression that I remember reading a number of years ago of the old Seimens armature which was covered with several coils. I think it was in an Electro motor. Do not lose sight of the fact that an Electro motor is reversible & this becomes a Dynamo machine & that the English Patents contain thousands & thousands of such motors and that it would be a mistake to examine magneto or Dynamo machines only. In England it will only be a difference in the manufacturing cost of the machine no matter what point I am betting on as I have so many ways of accomplishing the same result with [more] equally efficient and only differing as to cost.##Dyer is going into Bidwells final report and I will send his comments on it as soon as possible.##Did you find that little squib about a lecture delivered by some person I think named Fleming on the Swan lamp published in the Journal of the Chemical Society in January February March or April 1880 which I told you about. You should get a copy of the Proceedints of the newscasteron [Tyne] Chemical Society in which perhaps the full paper is to be found. If the paper is as I think it is it might be as well to show it to Sir William Thompson as well as it show Swans lecture in which he already sets forth that he did not [know] the object of high resistance lamps but merely expressed the idea that what [wanted] was carbon made out of paper.##we have tested the bar and little end Disc "Z" Dynamo - the same style as Batchelor had but with end discs a little thinner. It was intended to run 150 B lamps but it is so very economical and is of such very low resistance that we actually over 300 B lights at 9 or 10 candle power on it and it was only 158 degrees Fahrenheit after running one hour and a half, I propose to send this armature which will fit any of your machines by the next steamer. You can then have Hopkinson test it as Howell did whose paper I sent you and also Sir William Thompson and I think it will be found that when fifty horse power is taken out of the machine it will be a 97% machine of which 91 or 92% is available outside of it.##In case you might order those for light machiines for Covent Garden Dean is going ahead to make three or four different sizes to strike the size. We are going to wind these with wire as the connections of the bar and Disc machines are somewhat expensive in the absence of special tools the making of which can only be warranted on our receiving large orders.##In a few weeks we expect to start putting together six large Dynamos simultaneously for the Down Town Station.##Francis Jehl as I have already written you left yesterday on the Arizona with 20 Twenty Light meters and 5 Fifty Light meters. These meters are remarkably accurate. they beat anything ever got up. They are cheap & reliable. You will have to provide him with a pair of accurate assay balance [seates] and some sundries. Also a good man for him to instruct in the way I think a German Chemist would be as good a man as could be got and I think you will find many of them in London who will work for a moderate salary.##The Dynamo that went yesterday will stand all the lamps you can put on it that the Engine will take care of or the brush man can handle Francis will show you some of the [--acks] about these new brushes - they are very nice the whole arrangement is very handy and brushes may be put on and taken off with the greatest ease when the machine is running. All that it requires is a little practice in setting the brushes. Francis will [man] your amalgrams when he arrives as we have found that zinc amalgram is preferable to copper. Expense will dictate to you whether to run both machines connected together at full [alacity] and allow the whole load to be distributed over two machines or whether to run one machine at full capacity and run the other slowly ready to [take] over in case of any accident to the first machine. I think the latter is preferable as with proper arrangement it would only make a slight dip not more than four seconds, and that only when an accident occurs which should not occur more than once [--] two or three weeks. It may be possible that you can so arrange it when an accident occurs and you are compelled to stop the first machine that yiou can speed up the [second] machine and throw over without making a dip in the light. That is supposing one machie was running full speed the other one slowly before you stop the first machine speed up the second machine connect it accross the line let it take half the load then disconnect the first machine and thus it will take the whole load. This would only make a slight variation in the candle power which couold be instantly brought back by the regulator. I do not think it would make more than three or four candle power difference in the light. In this way you would only require one engineer and the whole attention could be passed to one machine. I do not know whether I mentioned it before but I think it would be a good idea to have a flexible hose to run to the machine with cold water so that it can be put in any bearings. In our [---] Central station machines we are having water jackets put on all of our bearings. Ebery three or four days it would be a good idea before starting on the regular run to run the machine slowly and with a coarse cut fill smooth off the commutator and reamalgamate it. In this way you will wear your commutator down very smoothly. In our Central Station machines we are arranging the commutator [strips] so that they can be screwed and unscrewed so that the whole commutator can be changed by receiving in new strips and made entirely new in about three hours and so we can have machines idle at all times in the Central Station we shall not have any trouble about the commutator business.##The reason why this last [machine] sent you will spark more with a quick load is because it is such an exceedingly low internal resistance in fact it is a 200 horse power Dynamo. Hence when two bars are short circuited by the Commutator Brush it means a very great deal. It is almost equal to three of the Paris machines multiple arc'd together the resistance of the Paris being ten thousandths while this is only thirty eight ten thousandths or eight ten thousandths more than three Paris machines multiple arc'd together.##The Piston was not sent on the Arizona as it made a little knock and Porter when we took the Engine down took it to Philadelphia to fix it and promised to send it to you by express it will doubtless reach you before you need it. Before testing the machine the last time we had our chimney fixed and while the Engine was [indicating] 250 h.p. the Boiler which is the same as yours actually ran up from 125 to 138 lbs boiler pressure whereas previously with a small chimney it would run down from 135 to 90 lbs inside of two minutes. If you have a good draught you can get two hundred horse power out of this Porter Engine. You will have plenty of volts to regulate on when you [ran] 1200 lights on & when you have a man to keep a constant electromotive force you will find that the breakage of lamps will be excessively small.##We have made a number of experiments at the Lamp Factory and have ascertained that 16 candle lamps giving 5 36/100 horse power in the current will last 35000 hours that if the economy be increased to 8 1/2 per horse power in the current the life reduced away down to 2200 hours & if you take 10 p. h. p. in the current line in 800 hours providing the electromotive force is left constant. So you see if in certain places economy is no object lamps can be made that will last almost indefinitely.##The lamps we are now making and which I have written you about and am sending you some are [ten] per horse power in the current I do not know whether I have [resistance] before what we did with some of them [--] I have what I [give] below is the latest. 26 of them were set up in the Lamp Factory, where a man sits night and day & keeps a constant electromotive force Last Saturday night, the average of all the lamps was 1220 hours twenty were still running. We made a number of 100 candlepower lamps but found the lamps were but found the lamps were not thick enough to carry the current at the point of contact between the copper and the clamps. They give a very fine light. I hope in a few days to have. some fibres with sufficiently [thick] ends.##I have not had good success with the method of getting high resistance on coiling owing to the fact that the fibre filament being excessively fine the whole of the surface was exposed to radiation except when each convolution [almost] [touch] the other but I am now working on a new line which promises to give us exactly what we want.##Your letter Jany 29th. Letters to Preece & Sir John Lubbock were sent you some time back.##we have shipped Dynamos to you as follows:##Oct 4th 3 "Z" machines##Oct 4th 2 C (Central Station)Oct 25th Nov 2nd 20 Z machines##Jany 11th 4 Z machines##Jany 13 6 Z machines##Jany 19 2 Z machines for motors##Feb 13 1 C (Central Station)##We have shipped to [Col] G. E. Gouraud for his own account the following:##Nov 4th 3 Z Dynamos##Nov 10 & 11th 17 Z Dynamos##I think this will give you the information you desire##I see from Mr. [Aouveries] letter that he thinks I am like all the rest of the Inventors that I am flighty and have no idea of practical financial questions &c &c. He might consult with Mr. Pierpont Morgan as to whether that point when he arrives in London. He should put the square question to Pierpont Morgan as to whether I have ideas of business and whether I can conduct several large manufacturing establishments besides superintending the installation of the Light here, having no small say in the policy of the various Companies & conducting experiments on half a dozen widely different subjects all at the same time. Drexal Morgan & Co do not hold such views as Mr [Aouveries] or they would certainly not have put into the Electric Light the amouont of money they have simply on my statements as to ultimate success. They do not usually go into business on the wild assertions of a flighty inventor.##Written in great haste to catch mail will write in a day or so Serrell




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