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cluded without disparagement to that which remains. Hailes v. Albany Stove Co., 123 U. S. 582, 8 Sup. Ct. 262, 31 L. Ed. 284. But the right to disclaim is a beneficial provision, and is entitled to a certain liberality of treatment, and may be made use of to avoid the effect of having embraced more devices than could properly be the subject of one patent (Sessions v. Romadka, 145 U. S. 29, 12 Sup. Ct. 799, 36 L. Ed. 609); or even to remove an ambiguity (Carnegie Steel Co. v. Cambria Iron Co., 185 U. S. 403, 22 Sup. Ct. 698, 46 L. Ed. 968). Matters duly disclaimed thus cease to be a part of the invention, and the patent is to be construed as though they never had been included in it. 22 Am. & Eng. Encycl. Law (2d Ed.) 402; Dunbar v. Meyers, 94 U. S. 187, 24 L. Ed. 34; Schwarzwalder v. New York Filter Co., 66 Fed. 152, 13 C. C. A. 380. In the present instance the complainants merely disclaim that Baker, their assignor, was the original inventor of a regulating reactance device, such as is covered by the patent, as applied to a single arc lamp. That is to say, no claim is laid to this as a part of the invention. There is no admission, however, in this that the subject of the disclaimer appears in the prior art, which may not by any means be the case, nor is there any justification for so construing it. It merely takes out of the patent the excided matter, leaving it as though it had never been there. This does not, of course, prevent that which is disclaimed from being identified with anything to be found in the prior art-such as the Spencer lamp, for instance, in the case in hand -with whatever argument may be legitimately drawn therefrom. But there is no sanction for using the disclaimer as evidence that there is any such device in fact, which is the effect sought to be given it here, as to which it does not undertake to speak.

The most important reference has yet to be considered, and that is the General Electric Constant Current Transformer, to which allusion has already been incidentally made, which was installed at Hartford, Conn., in the early spring of 1898, somewhat less than a year prior to the Baker invention. This was the first successful attempt at complete regulation, and it is to-day, in its perfected form, the only kind outside the Baker which has gone into extensive commercial use. As already stated, it is based on the Thomson patent, No. 516,846, and, as observed in that connection, it was not at first provided with anything to vary the force of the counterweight, a detail which was subsequently worked out, but not till after the Baker regulator had made its appearance. Except in this superadded feature it makes use of no principle which is not to be found in the patent referred to, and as that did not anticipate the Baker neither does it. Granting that both are reactance regulating devices, in which a magnetic force is opposed to a mechanical one, and that the two are so correlated in each as to accomplish a generally similar result, the difference between them is nevertheless marked; being one not simply of mechanical construction, but of mode of operation and of type. In the General Electric Transformer, the main or primary current remaining unchanged, regulation is effected, partially, it is true, by reactance or the choking of the current, through increased self-induction in the transforming coils, but principally by varying the pressure of the induced current through a change in the ratio of transformation, as the primary and secondary coils are

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repelled from each other under the force of the accumulated voltage. It is to facilitate this result, rather than to secure constancy of current, that the counterbalancing weights, hung upon adjustable eccentric winding surfaces, are employed, the transformer being actually set to give a varying current in the lamp circuit, at different loads, instead of a constant one, increasing or decreasing to meet the changing conditions by the cutting in or out of lamps; while, in the Baker, regulation is accomplished by a direct choking of the current, by means of a reactance interposed in the lamp circuit itself, the whole purpose being to maintain a constant current in the face of a constant potential, all the way from full load to no load, which it effectively does. In matters of detail, also, the two differ materially. In the Baker the choking of the current depends on the relative position of the coil and core, such choking increasing as they are drawn together by the increased magnetic pull produced by the accumulated energy of the current, and decreasing as this is otherwise taken up, and the two are forced apart by the counterbalancing weight; while in the General Electric Transformer the relation between the coils and core does not change, but only that of the coils to each other, the function of the core, which remains equally in the magnetic field of both, being simply to increase their influence upon each other. This influence, moreover, being one of repulsion and not of attraction, requires a delicacy of adjustment, because of its weakness, which is not necessary where the many times stronger force of attraction is employed; and its effective range is correspondingly limited. Where, therefore, the Baker regulator is simple and compact, and, with a marked economy of material, is able to cope with the entire situation from no load to full load, the General Electric Transformer has a tank huge in size, and bursting with mechanism, and still only undertakes to regulate up to 72 per cent. of the number of lamps in circuit. Incidentally also it is to be noted that the variable weight, the original purpose of which was merely to serve as a counterpoise to the coils, is at its maximum effect at full load, where it is at its minimum under the same conditions in the Baker, the two thus working functionally to secure diametrically opposite results. Nor at the outstart

was it a matter of design that, as in the Everest patent, where it is given no function, there should be an upward bend to the arm of the lever which carries the adjustable quadrant or sector, on which in the larger sizes of the transformer the weight is hung, the original purpose of this being so that the sector should avoid striking the tank at its lowest position. Not till afterwards, and after it had been made use of by Baker, was it appreciated that in this form it aided the quadrant in varying the leverage of the weight. Without dwelling further upon the subject, it is thus abundantly established that, as already stated, the General Electric Transformer differs radically from the Baker regulator, however much in a general way, they may seem to proceed along similar lines. The problem presented to each was no doubt the same, but it has been worked out in distinctly different ways; nor is this to be obscured by the fact that magnetic and mechanical forces bearing a resemblance to each other have been made use of and correlated in both, the manner of doing so being by no means the same. Accepting the General Electric Constant Current Transformer as the best product of the prior art, the increased range of effectiveness of the Baker regulator, as well as its simplicity of construction in comparison with the great complexity of the other, is proof of itself of the advance to be found in the latter, even if there were nothing else. Sessions v. Romadka, 145 U. S. 29, 12 Sup. Ct. 799, 36 L. Ed. 609; Hobbs v. Beach, 180 U. S. 383, 21 Sup. Ct. 409, 45 L. Ed. 586; National Brake Beam Co. v. International Brake Beam Co., 106 Fed. 693, 45 C. C. A. 544; Boyer v. Keller Tool Co., 127 Fed. 130, 62 C. C. A. 244.

The General Electric Reactive Coil-based in part on the Thomson patent, No. 516,847, supra, and in part on the Everest patent, No. 710,050 goes one step further, and adopts as the mechanical force employed a counterbalance lever and variable weight, the reactance device being also in series with the lamps. But the latter consists of two oppositely wound coils, set one above the other, surrounding and movable upon a common core, the repulsion between the coils, the same as in the constant current transformer, being the magnetic force made use of, the core being merely an intermediary between them. But even if this device approached more nearly to the Baker than it does, it adds nothing to the case against it, because it clearly is later in date. The earliest form which it assumed was a small apparatus built for the purpose of experiment, in March or April, 1899, which as late as September of the same year, when the paper of Prof. Robb was read and discussed before the American Institute of Electrical Engineers, had not yet been put into what was considered a successful commercial shape. It is a question just when afterwards this was accomplished, but it is not important to decide; for its first beginnings were admittedly prompted by the coming out of the Baker regulator early in 1899, which the engineers of the General Electric Company endeavored to meet with something of a correspondingly inexpensive character. The visit of Mr. Baker to Hartford at the instance of Mr. Westinghouse, at which time it is claimed that he got his ideas, was prior to this, in November or December, 1898. But even though the conceded purpose of this visit was to inspect the plant of the General Electric Company,

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and see how to get around their constant current transformer which was there installed and being displayed, the fact remains that he did so, with a device of his own of distinct character, which, as shown by his letter and sketch to Mr. Westinghouse of December 26, 1898, was almost immediately conceived, and was put into commercial shape, substantially as it now appears, about March 1st following. As the General Electric Reactive Coil was subsequent to and consequent upon this, it needs no further notice here.

There can be no question from this review of the prior art as to the entire novelty and validity of the Baker invention. It is true that the whole field was not open to him, but only an as yet unoccupied and somewhat restricted place in it. There were undoubtedly existing devices of kindred and suggestive character; nor can it be contended that reactance regulation, even as applied to an alternating current for arc lamps in series, and on a continuous as well as a transferred current, was altogether new, nor yet the correlation of mechanical and magnetic forces. What was new, however, was the particular forces selected, taken in conjunction with the way in which they were co-ordinated and combined; and especially in the discovery that a varying gravitational or other like mechanical force could be successfully opposed to the magnetic pull, at different positions of the coil and core of the choking device, and the two so adjusted as to afford with exactness the reactance required to meet changes in the resistance in the circuit, and thus maintain the current constant. This had been only partially and cumbrously accomplished by others previously, the efforts of the inventor producing that which not only differed in degree of effectiveness but ir type. To the extent that he has thus brought about that which is novel and useful he is entitled to the protection of the law, and the only remaining question is whether the defendants infringe.

If the fourth claim on which the complainants rest their case is to be taken as it reads, they certainly do. They clearly make use-in an alternating current circuit, in series with translating devices-of a regulating reactance device, consisting of a coil and core, the coil being suspended at the end of a pivoted arm or pendulum in proximity to the core, which is set above and at an angle to it, the two being so located relatively that the one is calculated to be drawn upward upon the other under the influence of magnetic attraction; the coil or moving part being thus adapted, when moved into different positions by the magnetic pull exerted by the varying energy of the electric current passing through it, to cause varying choking effects, and being itself acted upon in turn by the force of gravity, opposed to the magnetic pull, the one being so adjusted throughout its effective range of operations as to counterbalance the other, when the coil, by the greater or less reactance established by its position on the core, is calculated to produce a constancy of current. This which is exactly descriptive of the defendants' device, is at the same time descriptive also of the invention in suit, as expressed in the claim referred to. Aside, however, from any technical adherence to terms, it requires but little observation to perceive that the inherent principle of the invention has been appropriated by the defendants, with only slightly varying features. That the two are

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closely allied is established by one of the defendants' own bulletins, where, after speaking of the Constant Current Transformer, it is said: "There is still another type of regulator which consists of an impedance coil, in which the impedance is varied automatically by changing its relation to an iron core, this impedance being in series with the lamps. This form of regulator has many things to recommend it. ... It can be used directly upon the primary circuit without any transformation, if so desired, which would give the system a greater efficiency, and it can be made extremely simple in construction. The Helios-Upton Company's Regulator is of the last-named type. It consists simply of two coils, which are supported on a pivot above them, so that they can swing up on an inclined U-shaped iron core. These coils are drawn up by their own attraction to such a point that their impedance always keeps the current constant. This is accomplished largely by the weight of the coil as an opposing force, a small weight being used only for adjustment."

Undoubtedly the invention under discussion is to be regarded as residing in a structure of the same general character as that which is described in the specifications, to which the inventor is to be confined. Diamond Match Co. v. Ruby Match Co. (C. C.) 127 Fed. 341. But even on the basis that, as the result of this, a lever is a necessary component, this is to be found in the defendants' regulator in the rigid arm on which the coil is hung, the weight of which is practically located between the pivot as a fulcrum and the opposing magnetic and mechanical forces by which it is swung up or down. This makes out a lever of the second class, and it is to be noted with regard to it that it is by the operation of the two forces mentioned upon each other, through it as an intermediary, that the changes in the position of the coil, and its consequent varying reactive effect, is brought about, the same as in the invention in suit. This establishes in both form and function the substantial equivalency of the two. It is only as a critical angle in one arm of the lever is made an essential feature that the defendants are able to escape. This, no doubt, is the form to which prominence is given by the inventor in the specifications, but there is nothing there which of necessity restricts him to it. As was observed with regard to the method patent-although the two stand somewhat differently-all that is shown in the specifications may well be taken as illustrative merely, and not as intended to impose a limitation, other than as just indicated.

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