The Tesla Patents

Sweeping Decision in Favor of These Patents by the United States Circuit Court

Judge Townsend of the United States Circuit Court of Connecticut, recently handed down the decision sustaining the three Tesla patents of May 1, 1888. These patents are numbered 381,968, 382,280 and 382,279. The suit was that of the Westinghouse Electric and Manufacturing Company against the New England Granite Company.

The decision is a very sweeping and interesting one to the entire electrical fraternity, and we present it almost in full herewith.

Townsend, District Judge.

The patents in suit relate to the art of electrical transmission of power by the use of mechanically generated alternating electric currents.

It is, of course, understood that the real nature of electricity is still unknown, and that the nomenclature used herein, such as “currents,” “flowing,” etc., are merely convenient technical terms to indicate certain known results.

The electric current induced by a mechanical generator - a dynamo - is necessarily alternating in character; that is, alternating in direction, so that the current, acting on an armature, first tends to actuate it in one direction and then reverses said effect and neutralizes such actuation. Such a current flows uninterruptedly and regularly, but rises in intensity from zero to maximum and falls from maximum to zero, and then repeats said variations in the opposite direction. Its curve of increase or decrease of strength is indicated by a wave line or sine curve.

Every mechanically generated current is naturally and originally an alternating current. Formerly it was not considered practicable to use mechanically generated currents until their alternations were straightened out by means of commutators which reversed the direction of the current so as to make it flow continually through the conductors. A current which is periodically reversed by a commutator which thus breaks the current between the changes in direction and takes off the current in sections, is known as a reversed or alternating current. This distinction between an alternating and an alternated current should be carefully noted. An alternating current continues to act in opposite directions as originally generated. An alternated current has been so reversed that the whole flows in one direction and is then known as a continuous current. When so reversed by commutators as to become continuous, the current loses certain characteristics essential to its highest efficiency.

Prior to the Tesla inventions, only reversed or alternated electric currents were used for the transmission of power. The application of this system for the transmission of power was limited, for various reasons; among others because a large current could not be safely used at sufficiently high pressure for long distances. On the other hand, the pure alternating current was practically unlimited in volume and pressure, and a change of pressure could be economically effected by the use of a transformer.

Prior to Tesla’s inventions, however, these rapid alternations of the alternating current prevented the motor from starting its revolution and interfered with its continuing in operation, except when in synchronism with the generator. It was therefore impracticable for varying loads.

The problem which was presented to Nikola Tesla, and which he successfully solved was: How to overcome the difficulties attendant upon the use of the alternating currents so that their inherent vitality and untrammeled energy might be utilized for the unlimited transmission of power.

In an electric motor, the tendency of the armature is always toward the pole or point of maximum magnetic intensity. If a loosely-pivoted or freely-moving magnetic bar or armature be suspended midway between two coils of insulated wire wound in opposite directions on a soft-iron bar, and one of the coils is electrically energized, north and south poles will be formed at the ends of the soft iron bar - their location depending upon which coil is energized; but if both coils be equally energized, the two poles will neutralize each other and cause a resultant north pole midway between the coils. If, now, the current in one coil be made weaker than in the other, said pole will move toward the coil of greater electrical energy. The magnetic bar or armature will follow the shifting position of the pole, and by thus gradually varying the energy in the coils, the armature may be alternately caused to move from the pole of one coil along toward the pole of the other coil.

The alternating current generated by an electrical machine, as before stated, constantly varies from maximum intensity to zero in one direction, and then from zero to maximum intensity in the opposite direction.

In the invention of the patents in suit, Tesla availed himself of this characteristic feature of alternating currents in the following way:

In constructing a motor, he arranged on an annular soft-iron core, two pairs of magnetizing coils, each pair at right angles to the other, that is, one coil of one pair at the top and one at the bottom, and one coil of the other pair at each opposite side of said core, and mounted an armature in the centre. Then, connecting them with an alternating-current generator, he caused a current from one pole of said generator to pass through one pair of coils and a current from the other to pass through the other pair.

If the cycles of alternating currents be regarded as divided into 360 degrees, then, as shown in the Tesla illustrations, they will have a relative displacement of 90 degrees. In such position the lines of magnetic force traversing the two coils will be at maximum in one while at minimum in the other. This relative displacement marks the differing phase or time relation of the two currents.

The effect of passing two equal currents through said coils would be to cause the pole of maximum intensity to pass midway between the poles of the respective pairs of coils. But the effect of the ordinary operation of the generator as before explained was to cause the current in each pair of coils to vary from zero to maximum and to zero and then to shift in the opposite direction, the intensity of the current flowing to one pair of coils being at maximum while that of the other was at zero and one increasing while the other decreased, and the result being to shift said poles so as to make them travel entirely around said core.

Fifteen days after the issue of the patents in suit, Tesla read before the American Institute of Electrical Engineers a paper entitled “A New System of Alternate-Current Motors and Transformers,” in which inter alia, he said:

“The transmission of power, on the contrary, has been almost entirely confined to the use of continuous currents, and, notwithstanding that many efforts have been made to utilize alternate currents for this purpose, they have, up to the present, at least as far as known, failed to give the result desired.”

“The subject which I now have the pleasure of bringing to your notice is a novel system of electric distribution and transmission of power by means of alternate currents, affording peculiar advantages, particularly in the way of motors, which I am confident will at once establish the superior adaptability of these currents to the transmission of power and will show that many results heretofore unattainable can be reached by their use; results which are very much desired in the practical operation of such systems and which can not be accomplished by means of continuous currents.

“Before going into a detailed description of this system, I think it necessary to make a few remarks with reference to certain conditions existing in continuous-current generators and motors, which, although generally known, are frequently disregarded.

“In our dynamo machines, it is well known, we generate alternate currents which we direct by means of a commutator, a complicated device, and, it may be justly said, the source of most of the troubles experienced in the operation of the machines. Now, the currents so directed can not be utilized in the motor, but they must - again by means of a similar unreliable device - be reconverted into their original state of alternate currents. The function of the commutator is entirely external, and in no way does it affect the internal working of the machines. In reality, therefore, all machines are alternate-current machines, the currents appearing as continuous only in the external circuit during their transit from generator to motor. In view simply of this fact, alternate currents would commend themselves as a more direct application of electrical energy, and the employment of continuous currents would only be justified if we had dynamos which would primarily generate, and motors which would be directly actuated by such currents.

“But the operation of a commutator on a motor is two-fold; firstly, it reverses the currents through the motor; and, secondly, it effects, automatically, a progressive shifting of the poles of one of its magnetic constituents. Assuming, therefore, that both of the useless operations in the system, that is to say, the directing of the alternate currents on the generator and reversing the direct currents on the motor be eliminated, it would still be necessary, in order to cause a rotation of the motor, to produce a progressive shifting of the poles of one of its elements, and the question presented itself: How to perform this operation by the direct action of alternate currents? I will now proceed to show how this result was accomplished.

The claims in issue in Patent No. 381,968 are as follows:

“1. The combination, with a motor containing separate or independent circuits on the armature or field magnet, or both, of an alternating-current generator containing induced circuits connected independently to corresponding circuits in the motor, whereby a rotation of the generator produces a progressive shifting of the poles of the motor, as herein described.

“3. The combination, with a motor having an annular or ring-shaped field magnet and a cylindrical or equivalent armature, and independent coils on the field magnet or armature, or both, of an alternating-current generator having correspondingly independent coils, and circuits including the generator coils and corresponding motor coils in such manner that the rotation of the generator causes a progressive shifting of the poles of the motor in the manner set forth.”

That of Patent No. 382,280, is as follows:

“The method herein described of electrically transmitting power, which consists in producing a continuously-progressive shifting of the polarities of either or both elements (the armature or field magnets or magnets) of a motor by developing alternating currents in independent circuits, including the magnetizing coils of either or both elements, as herein set forth.”

The claims in issue of Patent No. 382,279, are as follows:

“1. The combination, with a motor containing independent inducing or energizing circuits and closed induced circuits, of an alternating-current generator having induced or generating circuits corresponding to and connected with the energizing circuits of the motor, as set forth.

“2. An electro-magnetic motor having its field magnets wound with independent coils and its armature with independent closed coils, in combination with a source of alternating currents connected to the field coils and capable of progressively shifting the poles of the field magnet, as set forth.

“3. A motor constructed with an annular field magnet wound with independent coils and a cylindrical or disk armature wound with closed coils, in combination with a source of alternating currents connected with the field-magnet coils and acting to progressively shift or rotate the poles of the field, as herein set forth.”

Complainant’s theory of the Tesla invention is shown in the following citation from the brief:

“It will be observed that to produce a shifting of the magnetic pole in one case, and a consequent movement of an armature corresponding thereto, each coil A and B must be traversed by a current of variable strength, and in order to secure uniformity of the movement of the pole or resultant it follows that the variations in strength of current in the two coils must be gradual and preserve definite relations to each other, throughout the cycle of variation in strength which the two currents undergo.

“This principle lies at the foundation of Tesla’s brilliant discovery, the gist of which was the utilization of the alternating currents generated by an alternating-current dynamo or generator for effecting such shifting of the magnetic poles or resultant attractive forces upon the armature of a motor, and thus causing such armature to rotate in response thereto.

“His broad invention, expressed in a few words, was the production in a motor of a progressively-shifting magnetic field (or pole) by means of two or more independent alternating currents, differing in phase, and circuits which preserve the independent character and phase relation of such currents.”

Defendant’s position is shown by the following extract from their briefs:

“Referring further to the apparatus of Tesla, Waterman says (Rec., p. 52): ‘Briefly then, the apparatus consists of a ring held magnet having one set of coils tending to magnetize it on one
diameter and another tending to magnetize it on a diameter at right angles to the first, and these sets of coils or circuits are so connected to a proper generator as to be traversed by currents such as would be generated by two coils at right angles to one another rotating in a two-pole field.’ It will be seen from this that complainants claim a broad discovery and a broad invention based thereon. Defendants, on the other hand, contend that the alleged discovery was old, that its application was old, and that, since the days of Arago, there was never any room for a broad invention in the ‘obvious’ application of the alleged discovery;’ and that the present state of the art has been developed from the earlier art including Arago’s rotation by the mere application of engineering skill possessed by skilled electricians who have applied their knowledge as the progressive demands of the times called for it, supplemented by inventions special to the motor or the generator or the connecting circuits severally, and in no way entitling Tesla or any other patentee to prevent the sale of generators and motors through the ownership of an all-controlling patented ‘system.’”

The well-known Arago rotation is described as follows:

“Arago’s method of producing rotation in a copper disk consists of suspending it by its centre so as to make it lie horizontally above the poles of a horseshoe magnet and then rotating the magnet about a vertical axis. The rotation of the disk is due to that of the magnetic field in which it is suspended; and we should expect that if a similar motion of the field could be produced by any other means the result would be a similar motion of the disk.”

The chief contention of the defendants is that there is no substantial difference in character between alternating and reversed currents and that the art of electric lighting illustrated in the alleged anticipations showed such an analogous use of reversed currents that the substitution of alternating for reversed currents did not involve invention.

Defendant further contends that the principle of reversibility was well known in the art, and as the inventors of electric lighting apparatus state that by a reversal of their action, power may be produced, Tesla is deprived of all claim to the exercise of the inventive faculty. That is, that the same apparatus may be used as a generator or dynamo-electric machine or may be reversed and used as a motor or electro-dynamic machine.

(This word “reversibility” has no relation in this connection to the word “reversed” as applied to currents.)

In support of their contentions defendants chiefly rely upon four prior publications, namely, the Baily article, of 1879; the Siemens patents, of 1878; Deprez’s article of 1880-1884, and the Bradley application of May 9, 1887.

[The decision at this point quotes from different authorities at some length, from Siemen’s British patent of 1878 for improvement in apparatus for dynamical production of electricity and its regulation when applied for illumination. The statement is also made that on May 9, 1887, about six months before the filing of the Tesla patents, Charles S. Bradley filed his application for his dynamo-electric machine, a generator for converting power into electricity. Judge Townsend continues as follows:]

A comparison of the Bradley application prior to Tesla with the Bradley patent issued subsequent to Tesla shows that in the former he described a method and illustrated an apparatus designed to obviate the objections to a two-phase alternating current by combining both currents in one by means of a transformer, while from the latter he omitted this description and method and inserted figures which, while strikingly suggestive of the apparatus shown by Tesla, failed to show that he conceived the Tesla idea or sought to secure the object of Tesla’s invention.

For this reason, and further because Bradley’s application is limited in scope, and ambiguous and indefinite; because it fails to show that he had any conception of the Tesla idea of “the utilization of the motor for the purpose of progressively shifting the magnetic poles of a plurality of alternating currents by circuits which preserved the independence and differing time relation of their phases;” because, even if the idea had been first conceived by Bradley, it was not sufficiently described to disclose the principle or method of operation; because Tesla was the first to reduce this principle to practice, Bradley does not anticipate or limit.

Defendants’ chief reliance is on the Marcel Deprez publications of 1880-1884, and rightly so, for Deprez not only disclosed the principle which Tesla utilized, but he gave a mathematical demonstration of the rotating field. Complainant’s expert’s admission on this point is as follows:

“The article demonstrated mathematically the fact, which is also stated in the Tesla patents, that the polar line of an annular magnet may be shifted about through the entire circumference of the ring by the action of two magnetizing forces properly related.”

[Judge Townsend here quotes from Deprez’s writings, and then says:]

All that Deprez demonstrated, therefore, was that if a field was made in which the field magnet varied relative to the brushes, or vice versa, the angle of variation would be indicated by the needle in another machine which would move quickly or slowly as the brushes and magnets shifted relative to each other and would indicate the new angle subtended between the brushes and the magnet. The only useful, practical application of this device was to attach it to a machine which would produce currents, and to use the earth or a ship to indicate the shift of position by means of a needle on top of the mast. This apparatus failed to teach any one that alternating currents could be used as a source of power in a motor. It was a mere indicator. It did not involve the utilization of two alternating currents differing in phase as a source of power in producing a continuous magnetic field. It did not depend upon any constant, regular, progressive currents, and, so far as the evidence shows, it was like the apparatus of Baily, confessedly a mere laboratory experiment. That Deprez did not conceive of the Tesla idea of utilizing regular, progressive, constant alternations of current is conclusively shown by his own statement in 1884, after the publication of this paper and after the invention of the Gaulard and Gibbs alternating-current systems for lighting, when he published another paper in which he criticised the system and stated that one of the most serious objections to it was that it was not applicable to the transmission of power, and adds: “I must further remark that alternating currents are of no use in the transmission of power; they are suitable only for lighting purposes.”

In fine, the evidence shows that, as Professor Silvanus Thompson says in his work on this general subject: “Deprez’s theorem bore no fruit; it remained a geometrical abstraction.”

The underlying thought disclosed and applied in the Tesla patents is such a use of the rapidly successive opposing alternations of the alternating current regularly and constantly recurring in such differing phases as would not only prevent the alternations from stopping the armature, but would become a source of power. It was essential to the practical development of this idea that the alternations should rise and fall and succeed each other progressively and constantly should be arranged, as counsel for complainant puts it, “like the crank on a locomotive in which there is no dead centre, but one crank is always pushing forward.” Tesla’s invention, considered in its essence, was the production of a constantly rotating or whirling field of magnetic forces for power purposes by generating two or more displaced or differing phases of the alternating current, transmitting such phases, with their independence preserved, to the motor, and utilizing the displaced phases as such in the motor.

Baily does not describe the use, with alternating currents, of displaced phases. He only describes the producing of intermittently shifting poles by means of a commutator or reverser which is just what Tesla disclaims. Neither Siemens nor Bradley describes the utilization of such displaced phases of alternating currents with their independence preserved in a motor.

Deprez describes a parallelogram of forces and its application to indicate at any given moment the angle between two parts of a source of current. He did not contemplate the use of alternating currents nor utilize their continuous and constant movement nor did he utilize said current to produce power, nor did he have any idea of a whirling field of forces to propel a motor.

What then was the status of the art in 1887 when Tesla filed these applications?

Nine years had elapsed since the grant of the Siemens patent which, according to counsel for defendants, “is a full disclosure of the subject matter in issue in Patents Nos. 381,968 and 382,280,” and its “references ... at the hands of the skilled electrician ... would naturally, and as a matter of course, have resulted in an organization of elements constituting a system for the electrical transmission of power and embodying essentially the system” of said patents. Eight years had elapsed since Baily. It was four years since Marcel Deprez’s article, according to defendant’s counsel, “described the very thing that complainant claims is Tesla’s discovery and explained the theory of operation,” of an apparatus which “is an operative two-phase alternating-current generator supplying two-phase alternating currents to produce a rotating field in a motor” similar to the Tesla motor.

Prior to Tesla’s invention no alternating-current motors were in use.

Although there has been an urgent demand for some practical means of utilizing alternating currents for transmission of power none had been found.

The continuous and unparalleled development of the electric art had for years increasingly emphasized the want of an electric motor capable of distributing power for long distances and had vainly called for the solution of the problem of the use of alternating currents for this purpose; the leading electricians of the day concurred with Deprez in his declaration after he had devised his comparateur that alternating currents could not be utilized in the transmission of power and that the future belonged to continuous currents.

In these circumstances Tesla patented his invention and thus first disclosed the method and apparatus, now generally known as the Tesla polyphase inventions, and introduced a new method, a new means and a new terminology into the art. Six months later he read his paper before the American Institute of Electrical Engineers and announced that previous efforts to utilize alternate currents had failed; that he had brought forth a novel system for the transmission of power, and explained its theory and demonstrated its operation by exhibiting a working motor; and no one of the electricians present questioned his claim or criticised his apparatus.

The statements made by electricians at said meeting are supported by abundant quotations from the contemporaneous literature of the day, and it does not appear that the recognition of Tesla as an original inventor of said system and of the means for its practical application was ever disputed until this suit was brought.

There is nothing in the record to detract from the claims then made. Tesla did not discover the parallelogram of forces; he did not discover the rotary field; but he was the first to explain how to do practically what Baily had said could be done by an impracticable infinity of magnets, and others had said it could be done, but without showing how it could be done. He harmonized the hitherto opposing alternations, while preserving their character and power.

Since the date of the Tesla patents in suit there has been a revolution in the art due to the utilization of the means therein described. The contention that the transfer from the electric light art to the electric power art did not involve invention can not be maintained.

Even if it be assumed that the art of electric lighting is in a sense analogous to that of electrical transmission of power, the result was new and unexpected. It has been already shown in what respects a reversed current differs from an alternating current. The question as to how far they are alike is of minor importance because it is admitted that the reversed or broken current is not the same for the practical purposes to which this invention is especially adapted. Therefore, although Deprez, in one of his publications, suggested that his system might be used for an impracticable and almost infinitesimal amount of power, the fact that these currents had never been practically used for any such purpose and can not, even now, be practically used for currents of high potential, shows that it required invention to select from an art that particular kind of current which was necessary for the production of the best results, and to adapt the mechanism of an art analogous or non-analogous, to its practical application.

The very fact that all the earlier electricians assumed or asserted that reversed and alternating currents were the equivalents of each other, was one of the errors which retarded the Tesla discovery, and the practical application of the polyphase principle.

The view most favorable to the contention of the defendants upon all the evidence presented, may be fairly stated thus:

Prior inventors had stated that electric light machines could be so reversed as to furnish power, although it is not proved that any one had shown a method for their use or the practical application thereof, or had ever made such practical application.

No prior publication explained how to utilize this alleged well-known reversibility and no prior machine applied it.

To the question why, if it was so obvious that the operation of the apparatus might be reversed and alternating currents then used, such method was not put in practical operation, the only answer of defendants is that “there had been up to 1885 no commercial system of distribution of alternating currents.” But if this is so, is it not because the foremost electrical experts throughout the world had united in the opinion after repeated futile experiments that alternating currents were useless for the transmission of power and that the future belonged to continuous currents?

“The apparent simplicity of a new device often leads an inexperienced person to think that it would have occurred to any one familiar with the subject, but the decisive answer is that with dozens and perhaps hundreds of others laboring in the same field, it had never occurred to any one before.” Potts vs. Creager, 155 U. S., 597.

Siemens, chiefly relied on to support this contention, does not describe any mode of using alternating currents, does not refer to the use of commutators, and only refers to the use of said apparatus as an electro-dynamic machine “with suitable modifications” which are nowhere described.

The impracticability as motors of reversed currents induced by commutators, shows that Siemens, Baily and others did not discover the Tesla invention; they were discussing electric light machines with commutators.

Tesla first stated the discovery how these alternations could be thus utilized and showed the machine and method adapted for this purpose. He is entitled to a patent for this discovery as were the discoverers of the use of anthracite coal instead of bituminous coal, or of the hot blast instead of the cold blast, in the manufacture of iron, or of the practical application of electricity to the telegraph or telephone. Judge Blatchford once sustained a patent for insulating electric wires by means of gutta-percha, and said:

“The gist of the invention is the discovery of the fact that gutta-percha is a non-conductor of electricity, and the application of the fact to practical use. The claim is valid, even though a metallic wire covered with gutta-percha existed before the plaintiff’s invention, if it was not known that gutta-percha was a non-conductor of electricity, and could be used to insulate the wire.” Colgate vs. Western Union Telegraph Company, 6 Fed. Cases, 86.

It is not necessary to go to this extent in sustaining these patents. The complainant may safely rest its case on the general principles laid down in the various decisions of the Supreme Court and extended and developed in Potts vs. Creager, supra.

But if the evidence already considered be disregarded, and it should be assumed that alternating and alternated currents were theoretically-known equivalents, even then the argument for counsel for defendants does not appear to be sound. They contend that a superior result, by reason of the substitution of one known equivalent for another, does not constitute invention. But the first substitution or application of such theoretical equivalent to produce a new or non-analogous or unexpected result, may involve invention. Tesla applied the alternating current to do what the alternated current had never before done; namely, to produce a new, unexpected and practical system of transmission of power.

A careful study of the evidence has led to the conclusion that Tesla made a new and brilliant discovery. But even if this be incorrect, it is proved that by a new combination and arrangement of known elements, he produced a new and beneficial result never attained before.

The technical defense of non-infringement by reason of the fact that defendants use only a motor, and that there is no allegation or proof of conspiracy with the owners of the plant which supplies the power, was not pressed on the argument, and, as six days were spent in the discussion of the questions on the merits, this point will not be discussed.

If any amendment is necessary to cover these points it should be allowed.

The contention of defendants that Tesla does not describe an operative machine, is not satisfactorily proved. It is proved that, in fact, several practical motors have been manufactured according to his invention.

The model of the particular patented construction selected for this proof, claimed to correspond most nearly to defendants’ construction, failed to show a capacity of self-starting, and, when once started, revolved in either direction; but complainant showed on the hearing various differences between the construction shown in the drawing of the patent and the model, which, it was claimed, accounted for the failure.

The defendants use a three-phase transmitting system comprising a three-phase generator, three transformers and a three-phase motor. The argument based on the use of transformers was not pressed. ...

The serious question raised in this branch of the case is as to the construction of the word “independent” in the patents. Counsel for defendants contends that “the word used in the patent evidently refers to the physical relations which exist and not to any result produced.” Counsel for complainant contends that Tesla’s “broad invention ... was the production in a motor of a progressively shifting magnetic field by means of ... independent alternating currents differing in phase, and circuits which preserve the independent character and phase relation of such currents.”

The specifications and drawings of said patents describe and show six independent transmitting wires which are repeatedly referred to as constituting independent circuits, and the claims emphasize this independency. In defendants’ motor the coils of generator and motor are so interconnected that each line wire not only serves as a conductor for its own phase, but also for the other currents.

Defendants’ contention is fairly stated by counsel for complainant as follows:

“The defendants contend that currents of electricity belonging to each of the circuits are, therefore, at times all flowing in the same wire or wires, and that at certain instants in the operation of the same; i. e., when each of the single transmission wires is, for an incredibly short period, transmitting no potential (i. e., change from plus to minus) - two of the coils of the motor are supplying current to the third. ... They cite the admission of Mr. Waterman that ‘analytically’ it is perfectly true that currents of electricity of differing phase may be at times regarded as simultaneously flowing in the same circuit.”

This statement of Waterman, however, should be read in connection with his further statement, as follows:

“The net result of it all is that in a manner more or less complex to follow, these electromotive forces so cancel out that there is in each circuit a current differing in phase by 120 degrees from the current in each of the others, so that in the motor it is not possible to tell how the current got there, or over what kind of a circuit. (i. e., whether over a three-wire or a six-wire circuit.)”

Counsel for defendants argue:

“That the term independent as used by Tesla means such separation as is consistent with having the complete circuits traversed by the same currents - currents which at any and every point are of the same quantity, intensity and phase, so that, as Mr. Clarke puts it, each motor circuit receives its current from a corresponding generator circuit and from no other. It can not refer to circuits which are interdependent in such sense that two of the circuits are at times strictly in series with one another and in multiple with the third, and so are not ‘independent’ in any sense. The whole system is an interdependent and not an independent system.”

The following significant statement, however, is found near the end of the specification of the first patent, No. 381,968:

“By ‘independent’ I do not mean to imply that the circuits are necessarily isolated from one another, for, in some instances there might be electrical connections between them to regulate or modify the action of the motor without necessarily producing a new or different action.”

The claims, therefore, confessedly can not be read as requiring isolation of the circuits but at most only such independence as is necessary for the purpose of producing a rotary field; that is, the connections must be such as not to interfere with the independency of the circuits which operate to shift the poles.

The only practical result from defendants’ use of three conductors instead of six is an improvement “to regulate the action of the motor,” which result was anticipated by Tesla as above, and it is proved that it was known in the prior art that one of these arrangements was a substitute for the other.

Inasmuch as the defendants have not invented any new idea, but have adopted an old contrivance which performs the same result in substantially the same way by a formal and unsubstantial change in means, and by circuits which, while in some sense interdependent, are operatively independent, and which preserve and utilize the vital element independence of phase, these circuits must be held to be the equivalents of the independent circuits of the patent, the word independent being interpreted to mean operatively independent, so as to embrace the true spirit and essence of the Tesla invention.

This conclusion is supported by a great number of illustrations of similar uses of such independent conductors in the general field of the arts. As the expert for complainant has pointed out, in railroads, cash carriers, electric telegraphs, the tracks, the earth or a single wire, will serve as common but independently-acting conductors.

It does not seem necessary to further discuss this contention based on a technical verbal distinction.

Defendants’ three wires are operatively independent; they are actually independent while in action; they are independent enough to do the required work.

This case involves a diversity of complicated questions of the scope and effect of certain language, of the prior art, and of the operation of electrical apparatus. All these questions have been exhaustively discussed with singular ability and learning by the able counsel herein.

If the contentions of defendants as to the scope of the patents in suit are proved the question of infringement of the patented independent circuits is not free from difficulty. If independence means isolation the patents are valueless. But if complainant’s contention is correct, and if Tesla is entitled now to the broad claim which no one denied when he announced it to the American Institute of Electrical Engineers as his “novel system of electrical distribution and transmission of power by means of alternate currents ... which will at once establish the superior adaptability of these currents to the transmission of power and will show that many results heretofore unattainable can be reached by their use,” then there can be no question that defendants have infringed. The foregoing language has been again quoted in order to emphasize how consistently at the end of 10 years after a review of all possible questions Tesla stands upon his original statement of invention.

Infringement of the first claim of Patent No. 381,968, necessarily implies infringement of the method Patent No. 382,280. The finding that the circuits of the defendants are independent, in the sense of the Tesla patents, is decisive against the defendants as to the infringement of the first and second claims of Patent No. 382,279; and the field magnet of defendants’ motor, while differing in some respects from that of the third claim of No. 381,968, is annular or ring-shaped within the meaning of said claim and infringes it.

At the close of the defendants’ brief is printed the “Decision of the Imperial Court of Germany on Tesla Patent.” The only reference thereto in said brief is in the statement that in said suit “brought to obtain a cancellation of Tesla’s patents, that a German patent to one Haselwander (including the rotary-current system employed by defendants) was partially annulled because of the publication of this American patent to Bradley” and in the following statement:

“It should also be mentioned that the Imperial Court held that the system employed by defendants does not infringe the German Tesla patent corresponding to the patents involved in this suit - that court holding with us that our system is a dependent system and not having the independent circuits of the Tesla patents and inventions.”

It is somewhat difficult to determine, from said opinion, the scope of the issues involved, but it appears that some German firm had applied to have two Tesla German patents canceled on the ground that they have not been worked, but “have only been used to the disturbance of the electro-technical industry in Germany.” Tesla, as defendant, admitted that he had not actually worked his invention, but had fulfilled his duty by a license to a firm which had pledged itself to work the patents, and, furthermore, that certain alleged infringers, by using a rotary-current, three-wire system, which seems to have been substantially like that of defendants herein, had “worked” his invention, and thereby saved him from the statutory penalty. The court held as follows:

“‘By independent is not meant to be expressed that the circuits are necessarily insulated from each other, since in single cases electrical connections can exist between them in order to regulate the working of the motor, without necessarily producing a new or another manner of working, then also nothing is gained for him thereby. Entirely disregarding the fact that after the striking out of the sentence, which clearly occurred in order to avoid unclearness, the independence of the circuits is only so to be understood as is shown from the drawing and description - namely, as conditioned by a completely independent outgoing and return conductor - there would also never be able to be read into the stricken-out sentence that therein the linking of the circuits in the meaning of the rotary-current system had been thought of, for this linking removes the independence of the circuits, while the erased sentence will only admit such connections as permit the independence of the circuits to exist.”

But this statement is a mere obiter dictum. The explanatory language relied upon by complainant in the patent here in suit has been stricken out of said German patent. The decision was upon two patents not shown to be the same as those herein in suit; the applications therefor were not filed until May, 1888, and not until after the Tesla invention had been described in a printed publication. But even this decision is to be construed as insisting upon a construction unfavorable to that here contended for by complainant, it should only be considered in connection with the foregoing facts. Here, the question of independence is directly presented, on a different issue, in view of a different state of the art, upon a different patent, from which the explanation of the word “independent” has not been erased. No sufficient reason has been shown why the conclusion of the German court should be followed in determining the question of infringement herein.

The search lights shed by defendants’ exhibits upon the history of this art only serve to illumine the inventive conception of Tesla. The Arago rotation taught the schoolboy 50 years ago to make a plaything which embodied the principle that a “rotating field could be used to rotate an armature.” Baily dreamed of the application of the Arago theory by means of a confessedly impossible construction. Deprez worked out a problem which involved the development of the general theory in providing an indicator for a ship’s compass. Siemens failed to disclose the “suitable modifications” whereby his electric light machine might be transferred into a motor, and Bradley is almost equally vague. Eminent electricians united in the view that by reason of reversals of direction and rapidity of alternations an alternating-current motor was impracticable, and the future belonged to the commutated continuous current.

It remained to the genius of Tesla to capture the unruly, unrestrained and hitherto opposing elements in the field of nature and art and to harness them to draw the machines of man. It was he who first showed how to transform the toy of Arago into an engine of power; the “laboratory experiment” of Baily into a practically successful motor; the indicator into a driver; he first conceived the idea that the very impediments of reversal in direction, the contradictions of alternations might be transformed into power-producing rotations, a whirling field of force.

What others looked upon as only invincible barriers, impassable currents and contradictory forces, he seized, and by harmonizing their directions utilized in practical motors in distant cities the power of Niagara.

A decree may be entered for an injunction and an accounting as to all the claims in suit.