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vol. 40.
tween the two applications. The controversy raised on this interrerence related principally to carbon made from paper, which Edison claimeu in his appJication. The case was not finally decided until the beginning of 1885. Mr. Broadnax was examined as a witness in this suit, and testified as follows: "After the decision of the commissioner of patents of the interference, awarding priority of invention to Sawyer and Man, I resumed the prosecution of the application, insisting upon our right to the claims that had been once rejected by the examiner, among which was one for the U.shapf'd or loopcarbon illurninant. My attention was then called for the first time by the Elxaminer to the British patent of Konn, in which is shown an arch-shaped carbon ilIuminant, and Vlhich, as I thought.'anticipated broadly the claim for the U-shaped or arch-shaped carbon illuminant; and then, in the discussion of the case with the examiner, my attention was called to t,he patentability of the fibrous carbon illuminant, as such, on account of the properties such carbon possessed, which made it available for electric lighting above all other carbons." BeinJl; asked when this was, he said it followed soon after the decision of the commissioner of patents upon the question of priority, or as soon as he could, in the ordinary course, get the case before the primary examiner again. His best recollection was that it occurred in February, 1885. This testimony of Mr. Broadnax, which is undoubtedly to be relied on, in connection with the letter just quoted, shows that the idea of claiming carbons made from fibrous and textile materials was an after-thought, and was no pilrt of the purpose of the original application. The amendments relating to this new and broad claim were made afterwards, in February and March, 1885. We are of opinion that the changes made in the application in this regard were not justifiable, and that the claim in question cannot be sustained'; There are other aspects of the case, to which we might refer, which operate strongly against the claim of the complainants. Weare not at all satisfied that Sawyer and Man ever made, and reduced to practical operation, any such invention as ,is set forth and claimed in the patent in suit. Their principal experiments were made in 1878, and perhaps the begltming of 1879. The evidence as to what they accomplished in the construction ofelectric lamps is so contradictory and suspicious that we can with difficulty give credence to the conclusions sought to be drawn from it. We are not satisfied that they ever produced an electric lamp with a burner of carbon made from fibrous material, or any material, which was a success. During the year referred to, 1878, and the beginniug of 1879, they applied for and obtained ten different patents (besides An English patent) on the subject of electric lamps; but not one of them contains a suggestion or a hint of any such invention as is claimed in the patent in suit, which was not applied for until 1880. They al11"elate to lamps with straight pencil burners, generally of carbon, butwithout any preference given tJ one kind of carbon over another. The application for the patent in suit was not,made until January 1880,,-nearly or quite a year after all their experiments had and after the inventions of Edison had been published to the
CONSOLmATED ELECTRIC LIGHT CO· .,. U'.B:EESPORT LIGHT
co.
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world. One cannot read the patents before applied for by Sawyer and Man, with all their detail of apparatus and process for constructing and managing the straight stem conductors, without distinction of carbons,-apparatus and processes, many of which would be needless in the lam p now claimed,-without indulging some degree of astonishment at the pains and ingenuity gratuitously expended or wasted, if it was true that, all the time, they had in their possession a secret invention which would take the place of those complicated contrivances. The explanations made by the complainants for the delay in applying for the patent in suit fail to satisfy our minds that Sawyer and Man, or their assignees for them, have not sought to obtain a patent to which they were not legitimately entitled. But suppose it to be true, as the supposed inventors and some of the other witnesses testify, that, they did in 1878 construct some lamps with burners of carbon made of fibrous material, and of an arched shape, which continued to give light for days or weeks or months, still, were they a successful invention? Would anyone purchase or touch them now? Did they not lack an essential ingredient which was necessary to their adoption and use? Did they go any further in p1'inciple, if they did in degree, than did other lamps which had been constructed before? It seems to us that they were following a wrong principle,-the principle of small resistance in an incandescing conductor, and a strong current of electricity; and that the great discovery in the art was that of adopting high resistance in the conductor, with a small illuminating surface, and a corresponding diminution in the strength of the current. This was accomplished by Edison in his filamental, thread-like conductors, rendered practicable by the perfection of the vacuum in the globe of the lamp. He abandoned the old method of making the globe in separate pieces, cemented together, and adopted a globe of one entire piece of glass, into which he introduced small platinum conductors, fastened by fusion of the glass around them; thus being able to procure and maintain, perhaps, the most perfect vacuum known in the arts. In such a vacuum the slender filaments of carbon, attenuated to the last degree of fineness, may be maintained in a state of incandescence, without deterioration, for an indefinite time, and with a small expenditure of electric force. This was really the grand discovery in the art of electric lighting, without which it could not have become a practical art for the purposes of general use in houses and cities. It is unimportant to trace the various steps by which this great discovery was arrived at. It is well indicated and shown in Edison's patent applied for in April, 1879, and issued May 4, 1880, No. and is more fully described in nJnt which he applied· for No227 vember 4, 1879, and issued January 27, 1880, No. 223,898. An extract from the latter will serve to explain the principles of this invention. Edison there says: .. Heretofore light by incandescence has been obtained from rods of carbon of one to fuur ohms resistance, placed in closed vessels, in which the atmospheric air has been' repiaced by gases that do not combine chemically with carbon.'; The vessel holding the burner has been composed of glass, cemented
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to a metallic base. - The connection between the leading wires and the carbon hasbeenobtailled by clamping the carb()D to the metat The leading wires have always been large, so that their re.sistance shall be many times less than the burnei'; and, ,ibgt:llleral" the attempfs of previous persons have been to reduce the resistance of the cal'bon rod. 'fbe disadvantages of following this practice are that a lamp having but one ·tofonr ohms resistance cannot be worked in greatllumbersin; multiple arc without the employment of mail), conductors pf enorJPous dimensions.; That, owing to the low resistance of the lamp, the leading wires must be oflarge dimensions and good conductors, and a glass globe canpot be kept tight at the place were the wires pass in and are cemented; hence the carbon is consumed, because there must be almost a perfect vacuum to render the carbonistable, especially when such carbon is small in mass, and high in electrical resistance. The use ofa gas in the receiver at the atmospheric pressure, although not attacking the carbon,serves to destroy it in time by air-washing, or the attrition produced by the rapid passage of the air over the slightly coherent, highly heated surface of the carbon. I have re\'ersed this practice. 1 bave discovered that even a cotton thread, properly carbonized, and placed ina sealed glass bUlb, exhausted to onemi.llionthof an atmosphere, offers from 100 to 500' ohms resistance to the passage oithe cnrrent, and that- it is absolutely stable at very high temperatures; that if the thread be coiled as a spiral, and cal'bonized, or if anyfibrous vegetable substance which will leave a carbon residue after !.leating in a dos,ed chamber be so coiled,.it offers as much as 2,000 ohms resistance, without presenting a radiating surface greater than thre&osixteenths of an inch; that, if such fibrous material be with a plastic composed of lamp-black and tar, its resistance 'may be made high or low, according to the amount of lamp,black placed upon it; that carbon filaments may be made by a combination of tar and lamp-black, the latter being previously ignited in a closed crucible for several hours, and afterwards moistened and kneaded until it assumes the consistency of thick putty. Small pieces of this material may be rolled out in the form of wire as small as seven one-thousandths of an inch in diameter, i and over ,a foot in length, and the same may be coated with a non-conducting, non-carbonizirig substance, and wound on a bobbin, or as a spiral, and the tar carbonized in a closed chamber by subjecting it to high heat. the spiral after carbonization retaining its form. All these forms lue fragile, and cannot be clamped to the leading wires with:sufficient force to insure good contact and prevent heating. I have that if platinum wires are used, and the plastic lamp-black and tar material be moulded around it, in the act of carbonization. there is an intimate union by combination and by pressure between . the carbon and platina, and nearly perfect contact is obtained without the necessity of clamps; lience the burner and the leading wires are connected to the carbon, ready to be plaeed inthe vacuum bulb. When fibrous material is ul;led, the plastic lilmp-black and, tar, are used to secure it to a platina before carbonizing. By using the carbon of such high resistance, I amenabled to use fine platinum wires for leading wires, as they will have a small resistance compared with the burners; and hence will not beat and crack the sealed bUlb. Platina can ottlybe used, as its expansion is nearly the same as that of glass. III Ill, III I have carbonized and used cotton and linen thread. Wood splints, papers coiled in variQus ways; also lamp-black, plumbago, jlnd in variolls mixed withtar, and kneaded so that the same may be rolled out into wires of various lengths and diameters. Each wire, however, is to be uniform in size throughout." ' The first claimofthis electric lamp for giving light by incandescence, consisting of.a·. filament of carbon of high resistance, madeaa ,described, and secured to metallic wires, as set forth. . The
