BUFFINGTON, Circuit Judge.
In the court below the General Electric Company charged the De Forest Radio Company with the infringement of four patents. On final hearing that court held one of the patents valid and infringed and the other three invalid. By appropriate steps its so holding was brought before this court for review. Without entering into detail, we may say that, save as to patent No. 1,558,436, the reasoning, conclusion, and decree of the court below commend themselves to us, and we affirm the same. In the ease of patent No. 1,558,436, we feel the court below committed error in holding the patent invalid and dismissing the bill.
As usual in litigation over a patent of great commercial value, the vast mass of expert speculation, the protracted argument covering days, and with briefs that in the aggregate covered several hundred pages, the case, on reargument, narrowed to the simple question of the patent paternity of what is known commercially as the Langmuir tube. The court below held the tube had no patent paternity, and to that question we now address ourselves. The subject-matter of the patent and the general features of the pertinent art are set forth at length in the comprehensive opinion of the judge below, and by reference thereto we avoid the necessity of present restatement.
Laying aside for the present technical langmage and scientific discussion, and confining ourselves to simple statement, the Langmuir tube is a tube in which, for example, the gaseous conductor incident to a Fleming valve and a De Forest audion is dispensed with and a vacuum substituted therefor.
In the patent sued on, No. 1,558,436, granted October 20, 1925, to Irving Langmuir, assignor to the General Electric Company for “electrical discharge apparatus and process of preparing and using the same,” the specification states:
“The present invention relates to electrical vacuum discharge devices, and it comprises devices in which the electrical current is carried by negative charges called electrons, emanating from the cathode, independently of gaseous ionization such as occurring, for example, in the ordinary Roentgen tube.
“My present invention comprises improvements in electron-discharge apparatus which make possible a high load capacity and operation with the highest voltages, but the invention is also applicable and useful for moderate loads and moderate voltages.”
Existing objectionable incidents to the use of gassy tubes and the erratic, nondeterminable action of gas are pointed out as follows :
“In order to distinguish electron discharge devices made in accordance with my invention from the prior art, I will explain briefly the character of a pure electron discharge as distinguished from a discharge through ionized gas. In a Geissler tube, and in a Roentgen or Crookes tube the conduction of current is accompanied by and depends upon gas ionization. Without a certain minimum amount of gas a Roentgen X-ray tube ceases to operate and as this minimum is approached the resistance of the tube steadily increases.
“The passage of an electric current across a tube ordinarily involves the movement of negative charges called electrons which, under the influence of the impressed voltage, pass from the cathode to the anode through the vacuous space. If these electrons when [933]*933moving above a certain velocity collide with gas molecules they tend to ionize the molecules, splitting them up into electrons and larger and more slowly moving ions. Under these circumstances the phenomena of conduction across the tubes are the result of the action and interaction of the electrons and the ions; these phenomena are in general erratic and non-reproducible. The cathode under these conditions is disintegrated, technically it is ‘sputtered,’ which causes its rapid destruction. As gas ionization continues at higher voltages a blue glow may appear. The bombardment of the cathode by positive ions also causes heating of the cathode. The ionization of gases at low pressures by collision with electrons occurs at definitely determinable voltages, these voltages being known as the ionization voltages. These voltages are different for different gases. In the case of gases such as nitrogen, hydrogen, oxygen, argon, helium and neon, they are of the order of magnitude of fifteen to twenty-five volts.”
Describing the De Forest audion, and differentiating it from the alleged invention of the patent, the specification says:
“The phenomena above described as being characteristic of devices involving gas ionization are taken advantage of in an incandescent cathode device with three electrodes known as the ‘Audion.’ This device has been used as a receiver for radio-telegraphy and depends in its operation upon the rapid change of the discharge current when gas ionization begins. This point depends upon various accidental conditions which cause such irregularities in the operation of various devices apparently identical that sometimes only one of a considerable number can be used. Ordinarily the gas ionization in the audion begins to be important somewhere between 20 and 30 volts.”
Describing the Fleming valve and its limitations, the specification states:
“Another discharge device previously used to some extent was the Fleming valve. This was a two-electrode tube which, so far as I am aware, was always used at voltages well below the voltages at which positive ionization by collision occurs. It was not evacuated in such a manner as to permit it to be used at voltages materially above these ionization voltages without manifesting substantial positive ionization effects.”
Referring to high voltage, the specification makes this statement:
“No prior hot cathode devices are known to me operating with currents as great as above 5 milliamperes with voltages as high as about 200 volts; indeed no prior discharge devices are known to me operating in a practically usable manner and without substantial positive ionization effects with currents as great as about one-tenth of a milliampere with voltages as high as about forty volts.”
Specifying some of the differences and advantages of the alleged invention, the specification states:
“In devices made in accordance with my invention gas ionization is either entirely absent or is negligible and a discharge takes place which is (distinct in its characteristics from the described discharge taking place in an ionized gas. The cathode is not heated by the discharge itself. Blue glow glass fluorescence and in fact all readily visible indications of a discharge are ordinarily absent.”
Referring to the evacuation of the tube, the specification sets forth:
“For the evacuation of the device the glass walls of the tube are carefully heated to as high a temperature as the glass will stand without softening and in general the most approved methods of incandescent lamp exhaust are used. The evacuation of the tube preferably while still heated is carried out by moans of a suitable evacuating means, for example, a Gaede molecular pump, which removes vapors as well as gases. * * *
“The evacuation of the device should be preferably carried to a pressure as low as a few hundredths of a micron, or even lower, but no definite limits can be assigned. * * *
“It is also true that when the anode has been carefully freed from gas, residual free gas, even if present in a sufficient amount to cause some gas ionization when the apparatus is first started, does little harm, as it is quickly removed by the gas clean-up effect when the device is operated.”
Claim 12, which is, “An electrical discharge device, comprising a gas-tight-envelope, an elcctronemitting cathode, an anode deprived of ionizable, gas and a discharge controlling conductor, the space in the envelope being evacuated to a pressure not substantially in excess of a few hundred thousandths of a millimeter of mercury, said device being characterized by the fact that when operated below saturation and materially above the ionization voltages, the current is controlled by space charge substantially unaffected by positive ionization,” is typical in character of the alleged invention.
[934]*934Does the defendant use a tube answering this general description? We think it does, and that in giving up the old gaseous tube and using one of the “very high vacuum,” a change which it announced in its statements to the public, we have a virtual admission of the essential difference between the two tubes. The tube of this disclosure is aptly described as “non gaseous” and “of .a very high vacuum” by the defendant when putting it on the market, as follows:
“The tube consists of a highly evacuated vessel, cylindrical, rather than bulbular, in shape enclosing the three elements, grid, plate and filament in the form o£ the old type T tubular DeForest tube with which amateurs are familiar. The plate is of nickel, cylindrical in shape and surrounds a helical grid also of nickel. The filament is a crimped tungsten wire passing through the center of the grid exactly as it did in the old style.type DeForest tube. The chief difference between this tube and the type T tube of similar mechanical construction is in its evacuation. The old style type T was an ionic or gaseous tube very unstable in operation and requiring a variable ‘B’ battery. It had the decided disadvantage that after continued use the tube would get ‘hard’ and require more ‘B’ battery until it reached such a state as to be inoperative. ' The new ‘VT’ tube, like the DeForest standard tubes to-day, is purely an electronic tube exhausted to a very high vacuum, so that it is non-gaseous and will stand very high plate potentials-. When used as a detector, however, a battery of 20 to 40 volts is sufficient to give the proper plate current although voltages of 80 to 100 may be used without detrimental effect upon the tube. The ‘B’ battery moreover, is not critical in adjustment and, therefore, a fixed battery may be used and is used for all practical work. * * * The gaseous type tubes are, however, no longer being manufactured.”
Turning next to the question on which the validity of the patent depends, we inquire first as to its usefulness, for the constitutional power to create the monopoly of a patent in that regard conditioned “to promote the progress of * * * useful arts” and the Congressional enactment in pursuance of the Constitution is that “any person who has * * * discovered any new and useful,” etc. For in the final analysis, use, usefulness, is the acid test, the sine qua non of patent grant.
The unusual degree of usefulness of the tube may be assumed. The defendant by its use evidences its usefulness, and has, we have seen, adopted it and ceased making “gaseous type tubes-,” and the court below, after its exhaustive study of the art, aptly described the tube, and we agree with its estimate, as an agency which “because of its stability, reproducibility and power has made possible radio broadcasting, modern radio reception and long distance telephony.”
Seeing then we are here dealing with a progressive step which, next to the telegraph, the telephone, and the wireless, is probably one of the most far-reaching and beneficent in human progress, there can be no question of a nongaseous, vacuum tube’s usefulness. Such being the case, is it novel? The simple fact is that we see such a tube in universal use to-day; we know in the quoted language of the court below of its ’“stability”; of its “reproducibility”; of its “power.” We know that these elements have, as stated by the court below, made “possible radio broadcasting, modem radio reception and long distance telephony.” Indeed, the fact that a nongaseous vacuum tube makes possible the present improved practice shows that such practice did not exist before the Langmuir tube, and that no other device or devices, all-important as they may have been in their spheres, did either singly or collectively produce the present practice. The Patent Office recognized that. In the opinion of The Board of Examiners they found, in affirming the decision of the Examiner of Interferences, that “Langmuir was the first "to conceive and the first to reduce.”
While all the vast mass of knowledge testified to in these records was open to everyone to use, the simple fact remains that the nongaseous tube of modern use did not occur to scientists. Every one of the two hundred and sixty-six words in Lincoln’s Gettysburg Speech is found in the dictionary; most of them in the Bible. But it remained, not for Noah Webster or even the prophets of old, but for Abraham Lincoln, to take these isolated words and so use them conjointly as to produce the most remarkable combination in literature.
We do not disregard or minimize the all-important part of De Forest’s audion and Fleming’s valve play in the utilization of them in the Langmuir tube, but, in spite of such high value, neither of them, in isolation or conjoint use, gave the world the tube here in question, and it remained for Langmuir to so couple and co-ordinate the two by means of eliminating gas and using vacuum [935]*935as to produce the tube here involved. What scientific credit is due to De Forest or Langmuir or to what patent tribute Langmuir subjected himself in thus using their devices are questions not before us.
Moreover, the statement in the commercial circular of the De Forest Company that gas was an element of operation was in accord with the then scientific belief. In 1911 Gemsback, an experienced savant, wrote that in the audion “the operating principle is the shattering of a column of conducting gas by a received electrical impulse.”
The function of a gaseous tube as a conductor was stated by the Circuit Court of Appeals of the Second Circuit in Marconi Wireless T. Co. v. De Forest Radio T. & T. Co., 243 F. 560, 565, where Fleming’s valve and De Forest’s audion were considered, in these words: “The ‘gaseous medium’ of the audion is nothing but the commercial vacuum of the ordinary electric light bulb — air being a gas, and the bulb containing some residual air. In other words, defendant uses the same ‘vacuous vessel’ that Fleming does.” And in its opinion it stated that it was asserted in that case that the audion was “an apparatus in which the bulb contains ‘a substantial amount of gaseous medium’ essential to operation of the device.” To the same effect is the testimony of Langmuir, of which we find no contradiction, that:
“In the devices of the old art, in the De Forest audion, the pressure was continually changing. It sometimes increased and it sometimes decreased. Both things went on and there was an evolution of gas, water vapor would come off the bulb and be decomposed by the filament and it would generate gas. Gases would come out of the electrodes. Positive ions would bombard the walls and the electrodes would drive gas off.”
It will also be noted this court in its able and exhaustive statement of the art in Westinghouse Electric & Mfg. Co. v. De Forest Radio T. & T. Co., 21 F.(2d) 918, 927, said: “We observe that at the time of both the De Forest and Armstrong inventions, the only audion tubes in use were ‘gasey’ or ‘soft.’ ”
That its action was eccentric is shown by De Forest’s statement:
“In the first place, anyone who has had considerable experience with numerous audion bulbs must admit that the behavior of different bulbs varies in many particulars, and to an astonishing degree. The wing potential wing current curves for different bulbs, or even for the same bulb at different times, under different conditions (filament temperature, etc.) vary widely.
“What may appear to be a fixed law for one bulb may not hold for another.”
On the other hand, the current in Langmuir is practicable, steady, reproducible at any particular voltage.
It further appears that the Langmuir tube has a great advantage when it comes to re<placement. When a tube is defective, another of the same type can be bought and placed in the same socket. Not so with the audion. It required frequent replacement, and, where replacements were made, it was necessary to readjust throughout the circuit. In that respect the proof is:
“XQ. 35. What practical effect would harmful ionization have upon an audion amplifier such as, for example, is used in the telephone line?
“A. The worst immediate effect would be as to uniformity of operation, which would make continued adjustments necessary and would interfere with the replacement of one device by another, that is to say, when one tube burned out and another were put in an amount of ionization that would interfere with uniformity of operation would make it necessary to readjust throughout the circuit to take care of the substitute tube.”
As to the replacement, the proof is that:
“Another consequence of this uniformity is that replacement of the tubes without changing the apparatus becomes possible. That is particularly important in telephone repeaters and in radio devices both of the receiving and transmitting type. One wants to know that he can replace a burned-out tube with a new tube without having to make substantial changes in the apparatus.”
It will also be noted that the whole trend of the art was against the use of a vacuum, and, even after Langmuir had shown its use, it was deemed impractical. Thus in a paper of 1914 Wehnelt and Loibreieh said that ionization persisted in the best vacuum they could get.
Moreover, it is of great present significance that the then view of De Forest himself was against Langmuir’s use of the vacuum; he then stating in a paper read by him before a scientific body: “I believe, however, Dr. Langmuir has, by working into these high vacua and the high potentials necessitated thereby, pursued the less promising of the two paths of research.” The record shows no explanation, comment, or retraction by him of this statement.
[936]*936Such being the general state of the ease, has the defendant by evidence overcome the prima facies of the patent? We think not. As said by this court in Penn Electrical & Mfg. Co. v. Conroy, 159 F. 943, 948, citing the Barbed Wire Case, 143 U. S. 275, 12 S. Ct. 443, 36 L. Ed. 154, “The burden of proof upon this part of the ease rests upon the defendant, and every reasonable doubt should, be resolved against it.”' And in our view the crux of the ease is one of fact, namely, whether the use of a vacuum in the combination of the claim was Langmuir’s novel disclosure. We are not concerned with scientific theories and speculations as to what might have been done or what could possibly have been done, for, as well said by the Circuit Court of Appeals of the Second Circuit in General Electric Co. v. P. R. Mallory & Co., 298 F. 579, 582, we sit “not as scientists, but as weighers of evidence.” But we are concerned with the fact whether the combination of the claim which Langmuir disclosed was new. That some had bombarded anodes of X-ray tubes to get some of the gas out of them, that others had heated bulbs or used pumps to lessen the gas, may all be true, but none of them had produced the commercial tube which Langmuir gave to the public. And such actual contribution in use and not theory and possibility of speculation is, and of right should be, the decisive factor in patent reward. As was said by the Circuit Court of Appeals of the Second Circuit in O’Rourke Engineering Court Co. v. McMullen, 160 F. 939:
“The keynote of all the decisions is the extent of the benefit conferred upon mankind. Where the court has determined that this benefit is valuable and extensive it will, we think, be difficult to find a well considered case where the patent has been overthrown on the ground of non-patentability.”
We regard as of high evidential significance the statements made by the defendant in its circular to the public, already quoted. It will not do to brush aside and ignore it on the suggestion it was the work of some enthusiastic subordinate or sales agent. It was a deliberate statement of a great mechanical company of its ceasing to make and market a superseded article and to thereafter make and market a new and different one. No such change would in business practice be made by subordinates, but was, in the nature of things, the mechanical, scientific, and commercial determination of a great business organization. In this statement the defendant recognized a “non-gaseous,” highly vacuum tube as new. As we have seen, it differentiated it from its “gaseous” tubes up to then made, and publicly announced that such gaseous type tubes would no longer be manufactured. And, indeed, that no such non-gaseous, highly vacuum tube existed is shown by the fact that the testimony of experts and the laborious research by the judge below, whose industry is proverbial, did not disclose any such tube, as both parties to this litigation now make and contend for the right to make, existed, or had advanced the arts in question to this new standard of theretofore nonattained efficiency.
Such being the case, the defendant is driven to take the position — which found favor with the court below — that, in view of what existed in the prior art, it required no invention to so utilize these things in the prior art to produce a nongaseous, highly vacuum tube, and that this great progressive step was due simply to the art’s natural advance and improvement.
But in point of fact no such advance toward a nongaseous tube, as we are now told was to be looked for in the art, was actually made by the art. We would not be misunderstood. Advance, inventive and noninventive, was being made in the art, but their efforts were in other directions. We would not detract from the great advance made by De Forest and exemplified by his audion and by Fleming with his valve, but great as these steps were, both separately and collectively —and we regard them as the foremost in the advance of the art in the Sphere here involved —the gaseous tubes still continued to be used and the art generally regarded gas as incident, if not, indeed, indispensable, to their use.
Indeed, had the art followed the caution of De Forest heretofore quoted, we would have no .vacuum tube, a situation akin to that referred to by this court in the Turbine Case, 202 F. 932, 952, where we said:
“Finding, then, as we do, that the disclosures of the Moorhouse patent had no helpful bearing or practical effect on the impulse turbine art, and supported in that conclusion by the fact that its vagueness is such that fair-minded witnesses in this record greatly differ as to what its disclosures really are, we are not warranted in attributing to it any effect in the way of vitiating, or even minimizing, the work of Curtis.”
Now, as it seems to us, the art, although it did not exactly know how the gas in gaseous tubes acted and just why it was able to [937]*937so conduct, nevertheless continued to use it, and regarded it as the indispensable means of conducting. As against this firmly entrenched teaching and practice of the art, Langmuir’s suggestion of eliminating gas as a conductor was a radical change, and even more so was not the substitution of some other tangible conductor but the disclosure of supplanting the tangible gaseous conductor by the intangible conductor of a vacuum. Vacuums, per se, were of course known. De Forest’s audion and Fleming’s valve were equally known, but the suggestion of dispensing with gas and utilizing a vacuum between the two was as novel in practice as it was unlookcd for in result. Indeed, shortly before the patent in suit was applied for, and even though the use of a vacuum may possibly have been suggested, the director of the Research Laboratory stated in a paper read before the American Institute of Engineers: “In connection with this work of Fleming’s, we have studied the effect of vacuum on the current, and also found that the presence of gas is necessary for this negative discharge.” And that Langmuir’s use of high vacua did not appeal to so practical and eminent a scientist as De Forest was evidenced by his statement, heretofore quoted, made even after Langmuir had made known his process publicly: “I believe, however, that Dr. Langmuir has, by working into these extremely high vacua and the high potentials necessitated thereby, pursued the less promising of two paths of research.” For the defendant to now contend that the use of these extremely high vacua by Langmuir was simply the natural and to be expected growth of the art is to credit the ordinary art with a scientific capacity which a master of the art like Do Forest did not himself possess. If it was an obvious thing, as the court below believed and decided, for the ordinary art to do away with gas and gaseous tubes and substitute high vacua therefor, surely such an extraordinary mind in that art as De Forest, when confronted with the substitution, would not have pronounced high vacua a mistaken path. Had the ordinary art followed the advice of this superordinary adviser and leader, and discarded the suggestion of high vacua, it would seem, so far as the universally used nongaseous tube is concerned, it would not be in use to-day.
But it is contended by the defendant, and the court below so held, that all that Langmuir did was simply to vary in degree the prior use of the vacuum, and that a mere difference in degree does not constitute invention, or, to use the defendant’s contention, the Langmuir tube is “nothing more or less than the identical thing of the prior art with possibly a little higher vacuum, depending on the specific use to which the device is to be put.” Assuming the correctness of this general proposition, we think it is not applicable to the present ease. In considering change in degree, the test is not the quantum or minimum of change made, but the quantum of change in function and result which such change, great or small, effects. A great change may effect but a slight change in function and result, while a slight change may effect a radical difference in function and effect. The effect, the practical progress and use in the arts, are the aim and end of patent grants, and, where great results follow a change, the slightness of the change tends to emphasize and make all the more remarkable, unexpected, and inventive the disproportionate result the slight change effects. It was the slight turn of a screw and the closer proximity of the diaphragm that made the telephone diaphragm the carrier of speech and gave Bell the due reward — not for the slight turn of the screw but for the great effect it wrought. But a vacuum, or, indeed, change of vacuum, isolated and standing by itself, is not the Langmuir invention, but it is a working tube in which all the elements, cathode, plate, vacuum, so co-ordinate and interwork that current flow is not affected by gas. We say not affected by gas because of necessity an absolute-vacuum is an impossibility, but the degree of vacuum is such the current flow is no longer objectionably affected by gas. Just what the degree of vacuum shall be is dependent on several elements, and, as stated in the patent, cannot be exactly stated. In that regard the specification says: “The evacuation of the device should be preferably carried to a pressure as low as a few hundredths of a micron, or even lower, but no definite limits can be assigned.”
So regarding what we believe to be the basic question in the case, we limit ourselves to the foregoing statement of our reasons for our conclusion. But, in thus limiting our discussion, we deem it proper to s-ay that the numerous questions and considerations advanced in the case in other particulars have been duly considered.
The decree of the court below holding this patent invalid is reversed, and the record remitted, with instructions to enter a decree that the patent is valid and infringed.