Nikola Tesla's Achievements In the Electrical Art

“In the interval since Tesla did his really great creative work his name has been associated with 80 many projects of questionable scientific quality that I imagine they may have raised doubts in the minds of many as to his real achievements” (Doctor Frank B. Jewett in a letter dated January 1943). The Edison Medal (1916) was awarded by the AlEE to Tesla “for his early original work in polyphase and high frequency alternating currents.”₁₈ To record his “real achievements,” the accompanying two articles have been prepared by authors selected for their qualifying experience and professional standing.

I — Tesla's Contribution to Electric Power

Charles F. Scott
Honorary Member AIEE

Faraday's principle of electromagnetic induction discovered in 1831 after some 40 years of incubation resulted in practical forms of dynamo machines. Electricity from mechanical power (instead of costly batteries) stimulated invention of apparatus and the development of various methods or “systems” for distributing and utilizing the electric current. The evolution of “systems” culminated in Tesla's polyphase alternating current, with its unique induction motor. His system has dominated the development of electric service during a half century and continues today as our method of using electric power.

That was Tesla's contribution to electric power. Tesla's death in January last occurred in the semicentennial year of the demonstration of his polyphase system at the Chicago World's Fair and its adoption for the great Niagara project. It is the method in universal use today. We know no other. But the story of the pioneer years of electric light and power is needed to give perspective and reveal the real significance of the polyphase method.

Charles F. Scott, past president AlEE (1902-03), was with Westinghouse Electric Company, 1888-1911; then professor of electrical engineering (now emeritus) at Yale University. He was assistant to Tesla, 1888-89. In Tesla's original type of motor with primary coils around individual poles he effected radical improvement by devising a slotted secondary with specially distributed winding. Motors of this type (about five horsepower) successfully operated coal-mining machines as de- scribed in his paper in January 1891 before the Engineers Society of Western Penn- sylvania, its first paper on mining. His AlEE paper describing two single-phase installations, for lighting at Portland, Oreg., and for power at Telluride, Colo. (for the latter he made the general plan) presented in June 1892 was the institute's first paper on long-distance transmission. He participated in planning and prepa- ration of apparatus for the Chicago World's Fair and for the original hydroelectric development at Niagara Falls. His two-phase-three-phase transformer connection, more commonly known as the Scott T connection ("Polyphase Transmission," National Electric Light Association, March 1894), was used in the transmission of three-phase current to Buffalo from the original two-phase generators. He was technical advisor to Edward Dean Adams in his preparation of the two volumes "Niagara Power" and has made a special study of the state of the art in the period when Niagara plans were crystallizing. He was chairman of section D, electric power transmission, of the International Electrical Congress, St. Louis, Mo., 1904. His recent interest in electrical developments just preceding and during his own con- tact with them in the 1890 period have given a perspective view which he presents in the present paper.

After two score years, the dynamo; then in two eventful decades the trivial beginnings of the commercial electric light developed through the efforts of many workers and came to fruition in Niagara power, where the Tesla polyphase system achieved “the great step in the transition from mechanical power in industry to electric power everywhere”¹ and made possible our 20th-century power development. The years 1876, 1886, and 1896, serve as milestones marking these eventful decades.

1876

On Professor Elihu Thomson's 80th birthday anniversary (1933), I asked him just what electrical apparatus was at the Centennial Exposition in Philadelphia in 1876. “Well, I'll tell you,” he said. “There was a Gramme machine from France that ran one arc lamp, and another wound for electroplating, and a Wallace dynamo that operated a lamp on top of the building.” There was also at the exposition a dynamo designed by Professor W. A. Anthony.²

In 1928 the Franklin Institute celebrated the 50th anniversary of the first tests on the efficiency of a dynamo. Among the speakers were Charles F. Brush, whose dynamo was tested; Professor Thomson,³ a teacher of science in the Philadelphia High School, who conducted the test; and his student assistant, E. W. Rice, later head of the General Electric Company. Brush, a Michigan graduate who had been keenly interested in the making of electrical apparatus from his high school days, had invented a new type of dynamo which could supply four arc lamps by four independent circuits, commercial sales of which had started early in 1878. He said, “It was in that year that I had the good fortune to invent and develop the modern series arc lamp with its regulating shunt coil. It made arc lighting from central stations commercially possible; and I think it may be regarded as marking the birth of the electric lighting industry.” Dynamo and lamps were adapted to a constant-current series system; the usual current was about ten amperes, and the voltage increased about 50 volts as each lamp was added.

Following the Franklin Institute tests the Thomson-Houston arc-light system appeared; soon there were many others in vigorous competition for the lighting of streets and factories. To a limited extent motors were operated in series with arc lamps.

The constant-current (voltage varying with the load) system for operating motors is the method used in installations listed in Kapp's “Electric Transmission of Energy,” 1890. Usually a generator and a single distant motor constituted the power transmission. At the Comstock mine in Nevada six 80-horsepower Brush motors received constant current over independent circuits from six generators and were belted to a single shaft for operating a stamp mill.⁴

Incandescent lamps could be operated on constant-current circuits if they had heavy filaments adapted to large currents and a few volts, or were connected in series-multiple. Practical difficulties inherent in the series connection were many. Edison saw the merits of a constant-potential circuit and the parallel connection of lamps, enabling them to be turned on and off like gas lights. He set about to make a high-resistance filament that would take a small current and thereby make possible conductors of permissible size. In 1879 he achieved a lamp and also the constant potential system which is the method in universal use today. His Pearl Street station in New York City opened September 4, 1882.

Ensign Frank J. Sprague, a few years out of Annapolis, was American member, and secretary of the jury of awards for electrical machines and lamps at the Crystal Palace Electrical Exhibition, London, 1882. In his elaborate report to the Navy⁵ he describes about a dozen types of dynamos; evidently Edison's with “high- resistance” shunt field was the one particularly adapted to produce constant potential. Sprague says: “The Edison machines were designed to form part of a distinct and complete system of lighting and as such they possess some peculiar features not noted in other machines.” In a paper before the British Association for the Advancement of Science on “Demands of a System of Electrical Distribution” he presents the new constant- potential system as best meeting these demands. In his painstaking report he describes many forms of arc and of incandescent lamps on exhibit, but no motors. There were none. On his return he pioneered the construction and introduction of motors on Edison circuits.

Electric cars were attempted by many pioneers in the '80's. Trial roads of a mile or so with one or more cars were followed by Sprague and his Richmond road calling for 40 cars, doubling the existing total in the United States.

1886

At Thanksgiving time in 1886 at Buffalo, N. Y. came a radical innovation — operation by alternating current. The new kind of current in small amount was transmitted at 1,000 volts and then transformed to 20 times the current for 50-volt incandescent lamps. While the Edison three-wire system was commercially limited by the cost of copper to about a half-mile radius, the new a-c system greatly extended the area that could be served.

Westinghouse had acquired the Gaulard and Gibbs alternating-constant-current system in 1885. At Pittsburgh what came from abroad was completely revamped, electrically and mechanically. William Stanley, the Westinghouse electrical expert, recognized the desirability of changing from constant-current to constant- potential operation; he was familiar with counterelectromotive force (he is said to have coined that term). His aim was a primary winding with sufficient counter electromotive force to permit transformers to be connected in parallel to a high-voltage circuit; for this he obtained an important patent.⁶ Westinghouse, however, was concerned with securing a mechanical construction suited to manufacture. The form used in the early transformers was patented by him.⁷

The new transformer inspired confidence and Stanley proposed continuing the a-c development at Great Barrington, Mass. His successful demonstration of an operating system in March 1886⁸ was followed by the design and manufacture at Pittsburgh of commercial apparatus and the inauguration of a-c service in Buffalo.

While alternating current overcame the distance handicap of direct current for incandescent lighting, it had no successful motor.

In May 1888 Tesla, in a paper before the American Institute of Electrical Engineers, announced his new system of a-c motors. In the new system polyphase currents produced in the motor a rotating magnetic field which induced currents in the closed motor secondary circuit, producing mechanical rotation. The rotative effect of alternating currents succeeding one another in time is analogous to two or three cylinders for producing continuous torque in an engine.

Westinghouse realized what this motor would mean for a-c service, and he acquired patent rights and Tesla's services. A serious situation was encountered. Commercial circuits were single-phase at a frequency of 133 cycles. Strenuous efforts to adapt the Tesla motor to this circuit were in vain. The little motor insisted in getting what it wanted, and the mountain came to Mahomet. Lower-frequency polyphase generators inflicted obsolescence on their predecessors in a thousand central stations — such was the potency of the Tesla motor.

The typical method of the '80's was the invention of a useful device such as an arc or incandescent lamp, or a railway motor, and the development of a “system” to operate it, which usually carried the name of the originator. In a decade there appeared a score of systems — technical or commercial — for each type of lighting and a dozen for street railways. The initiative lay with inventors and manufacturers; what they achieved was accepted and used. But in 1890 came a challenge to solve an unprecedented problem.

In our milestone year, 1886, a charter was obtained for a great power development at Niagara Falls. By the initial Evershed plan many canals at right angles from the upper river were to supply separate wheel pits, each with a 500-horsepower turbine which would discharge its water into a tunnel system terminating at the foot of the falls. The project floundered until taken up by a New York group which entrusted its development to Edward Dean Adams. It was soon found that the cost of the proposed excavation of wheel pits and discharge tunnels for water wheels at points along 2½ miles of river front for the prospective industrial city would be far too great. Economy called for location of the water wheels at one point, but the production of enormous power at one point called for transmission both for local industries and for greater distances. Commercial electrical methods for arc and incandescent lighting either by direct or single-phase alternating current or for street railways when few electric machines exceeded 100 horsepower — all were inadequate for the great project. A world-wide quest for methods and apparatus was conducted by the International Niagara Commission of experts from several countries, headed by Lord Kelvin.⁹ It invited and received plans. A copy of the original record of the commission in five volumes — much in longhand — and 12 rolls of plans is in the Engineering Societies Library in New York. It shows the state of the art in 1890. The 17 projects from 20 representatives of six countries dealt with hydraulic equipment and with transmission. Of the best-presented plans for transmission, six were nonelectrical and four of these employed compressed air; of the six electrical plans, four used direct current. Typical of the latter was the connection of ten generators of 1,000 volts in series for 10,000-volt transmission to a similar arrangement of motors at Buffalo for driving generators for local distribution. Another plan proposed single phase, but “details were not fully described.” The remaining plan by Professor George Forbes advocated a polyphase installation. He said: “It will be somewhat startling to many, as I confess it was at first to myself, to find as the result of a thorough and impartial examination of the problem, that the only practical solution for Buffalo and the best solution for the new industrial city which it is proposed to build near Niagara lies in the adoption of alternating-current generators and motors.” He further stated: “The only non-synchronizing motor which has been developed in a practical form is the Tesla motor manufactured by the Westinghouse Electric Company and which I have myself put through various tests at their works at Pittsburgh.... The torque on starting is considerable... the largest I have tested was five horsepower... they have no commutator or even brushes or other collectors.” He proposed generators of 500 horsepower (in a 50,000-horsepower station) and transformers of 100 horsepower, as he advocated only sizes already assured.

The commission found no proposal acceptable; “no prize was awarded for system of distribution”; it looked favorably on electrical methods but was not convinced that alternating current was adequate. (Lord Kelvin persisted in his opposition to alternating current until he was proved wrong by its successful operation.)

That was the status of power transmission in 1890, when construction of the tunnel for 100,000 horsepower was under way.

The polyphase system gained fame through the 100- mile transmission from Lauffen to the Frankfort Exposition in 1891 in which a 30,000-volt circuit delivered power to a 100-horsepower three-phase motor designed by Dobrovolsky. The project had been proposed by C. E. L. Brown, eminent engineer and designer, to test transmission at high voltage by bare wires. He comments: “The three-phase current as applied at Frankfort is due to the labors of Mr. Tesla.”¹⁰

The Niagara project was alluring and the Tesla method promising. The leading American electrical companies, Westinghouse, Thomson-Houston, and Edison General, did not present plans in 1890. Shortly afterward, the latter two united in the General Electric Company, which continued the development of polyphase apparatus already begun by Professor Thornson. Westinghouse prepared for Niagara, delegating general engineering leadership to L. B. Stillwell and generator design to B. G. Lamme. As a preliminary, the lighting of the Chicago World's Fair, 1893, was undertaken by polyphase current. In an exhibit a 500-horsepower induction motor (pinchhitting for a prime mover) drove a two-phase generator for supplying power to motors and lamps, and, via rotary converters and motor generators, to all types of d-c operation — from one source all services.¹¹

The Niagara engineers had invited proposals and, when the two American companies indicated their readiness to proceed, visits were made to their works early in 1893 to inspect apparatus and discuss plans. Following successive presentations from both companies, a contract was awarded in October 1893 to the Westinghouse Company for three 5,000-horsepower Tesla polyphase generators-several times larger than any predecessor. (Later seven more completed the 50,000-horsepower equipment of powerhouse 1. The plans designated powerhouse 2 as “compressed air,” but later it was electrically equipped by the General Electric Company.)

The simultaneous development of the Niagara project and the Tesla system was a fortuitous coincidence. No adequate method of handling large power was available in 1890; but, while the hydraulic tunnel was under construction, the development of polyphase apparatus justified the official decision on May 6, 1893, five years and five days after the issuing of Tesla's patents, to use his system. The polyphase method brought success to the Niagara project; and reciprocally Niagara brought immediate prestige to the new electric system.

Power was delivered in August 1895 to the first customer, the Pittsburgh Reduction Company (now Aluminum Company of America) for producing aluminum by the Hall process, patented in the eventful year 1886. Thus the demonstration of alternating current by Stanley, the charter of the power company, and the beginning of aluminum, all occurred in the early months of 1886. Each evolved in its own devious way and then joined in less than a decade in initiating a new era in power, in electrical service, and in the light metal.

1896

In 1896, transmission from Niagara Falls to Buffalo, 22 miles, was inaugurated. Compare this gigantic and universal system capable of uniting many power sources in a superpower system, with the multiplicity of Lilliputian “systems” which previously supplied electrical service. As Mr. Adams aptly explained: Formerly the various kinds of current required by different kinds of lamps and motors were generated locally; by the Niagara-Tesla system only one kind of current is generated, to be transmitted to places of use and then changed to the desired form.

The Niagara demonstration of current for all purposes from large generators led immediately to similar power systems in New York City — for the elevated and street railways and for the subway; for steam-railway electrifications; and for the Edison systems, either by operating substations for converting alternating current to direct current or by changing completely to a-c service.¹²

The culminating year 1896 inaugurated two far-reaching developments for the extension of polyphase power, one commercial and the other engineering. By exchange of patent rights, the General Electric Company obtained license rights under the Tesla patents, later made impregnable by nearly a score of court decisions. Also the Parsons turbine, accompanied by its foremost engineer, was transplanted to America and enabled George Westinghouse to bring to fruition by a new method the ideal of his first patent, a “rotary steam engine.” The acme of the reciprocating engine came in the early 1900's; a century's development produced the great engines that drove 5,000- to 7,500-kw alternators for New York's elevated and subway. But the rapidly growing steam turbine of different types soon doomed the engine to obsolescence; single units with the capacity of a score of the largest engines are now supplying power to the metropolis.¹³ Single powerhouses now supply more power than all of the thousands of central stations and isolated plants of 1890.

At the turn of the century George S. Morison, eminent engineer, heralded manufactured power — engine power — as “The New Epoch”¹⁴ in human progress, most significant event since the invention of the written alphabet marked the step from barbarism to civilization. He reviewed the contribution of power to the industrial revolution and the 19th century development, notably through mills and factories, locomotives and steamships. He foresaw its accelerating expansion through new types of prime movers and electrical methods of distribution and application. Further, he indicated the profound influence of these physical agencies on our ways of life.

Much of what was predicted 40 years ago has already come to pass — including conflict and war. In our present strenuous war effort, both in the making of materials and in industrial production the sine qua non is electric power, and more electric power. The output of central stations during the first year of the present war was nearly ten times that of 25 years ago; it was greater than the immediately preceding year by 20 billion kilowatt-hours, the total output for the first year of World War I.¹⁵

Power and transportation have brought the nations of the world together as a unit. True, the development of physical facilities already moves faster than our ability to direct them to the social good. But the new epoch of power allows indefinite expansion in the progress of civilization and its contribution to the better life.

The coming of manufactured power marked the beginning of the new epoch in the progress of mankind. Electric power indefinitely amplifies the usefulness of mechanical power, through transmission and reincarnation in many motors, and by its production of light and heat and its contribution to chemical industry.

The evolution of electric power from the discovery of Faraday in 1831 to the initial great installation of the, Tesla polyphase system in 1896 is “undoubtedly the most tremendous event in all engineering history.”¹⁶

II — Tesla's Contribution to High Frequency

L. P. Wheeler

During the early part of the last decade of the 19th century the attention of the whole scientific world was challenged by Nikola Tesla's public demonstrations of the effects of high-frequency alternating currents. It was then very early in the commercial age of electricity. The incandescent light had not yet become commonplace, electric traction was just being introduced, and the controversy over the relative advantages of the a-c and d-c systems was at its height. Tesla's own contribution to this controversy — one destined to be largely influential in the ultimate establishment of the low-frequency a-c system of distribution — was fresh in mind. The scientific world, stimulated by the brilliant investigations of Hertz in the latter part of the previous decade, was just beginning to adjust itself to the actuality of electrical effects at a distance without the use of wires and to the explanation of them as due to electromagnetic radiation. Further, it must be remembered that the beautiful and curious phenomena of conduction through low-pressure gases at that time had neither lost their novelty nor received any convincing explanation.

L. P. Wheeler, is chief, technical information division, engineering department, Federal Communications Commission, Washington, D. C.; and president (1943), Institute of Radio Engineers. Doctor Wheeler graduated from the Sheffield Scientific School of Yale University (bachelor of philosophy, 1894; doctor of philosophy, 1902); and was a member of its physics staff from graduation until 1926. Three of his former students, DeForest, Hogan, and Van Dyck, are past presidents of the Institute of Radio Engineers. He had an active part in the organization of instruction in the Signal Corps School for Officer Candidates at Yale in 1918 and of graduate instruction in communications for Army and Navy officers, at Yale, 1919-26. From 1926 to 1936 he was associated with the United States Naval Research Laboratory, first as physicist, then as consulting physicist concerned particularly with radio communication. From 1936 to the present he has been with the FCC. He is coauthor of the book “Principles Underlying Radio Communication.” One of his student predecessors as president of the IRE, J. V. L. Hogan, says of him: “There are few men as well qualified to appraise Tesla's contributions to today's high-frequency techniques. Being well grounded in basic physics, and having been engaged in instruction, university and governmental research, and administration, he is able to view Tesla's work with a perspective not available to those more closely associated with industry.”

Thus the brilliant experimental demonstrations of Tesla in which the then customary limits both of frequency and voltage were far exceeded, coming at a time when the phenomena within those customary limits were not understood thoroughly, aroused extraordinary inter- est and stimulated research along several lines to a considerable extent. The lectures were literally as well as figuratively brilliant, as the effects of the high frequencies produced by his oscillation transformer were demonstrated chiefly by those luminous discharges in low-pressure gas tubes which may be regarded as giving the first impetus to the development of the modern methods of gas-discharge display lighting. By 1895 almost every physics laboratory in the country had built a “Tesla” coil, and much work immediately suggested by the lectures was under way. As far as the physicists were concerned, interest in such developments was, however, quite short-lived. This was due I think to two things:

1. There was a growing conviction (never shared completely by Tesla himself) that the distance effects were fundamentally attributable to electromagnetic radiation, and hence there was offered small hope of discovering any essential novelty. If there still remained some question as to the existence of some novel effect dependent on the very high voltages or frequencies or to their combination (a thesis maintained by Tesla himself throughout his life), the very general lack of existing equipment for dealing with the problems of insulation involved effectually discouraged any research in that direction.

2. That extraordinary series of discoveries (the electron, the X rays, radioactivity), which featured the second half of the 1890's and which almost overnight transformed physics from a striving for the next decimal place to an exciting exploration of new worlds, offered fields of research far more inviting and promising than that of high-frequency and high-voltage phenomena.

If, however, the lack of any effective follow-up of the Tesla phenomena on the part of physicists is understandable, it is more difficult to unravel 'the causes of the neglect of Tesla's procedure and devices in the commercial developments that followed, particularly those in the field of radio communication. One reason may lie in the fact that the industrial-research laboratory with equipment adequate to the problems involved was yet to be born. Another probably stemmed from Tesla's emphasis on the power rather than on the signal- transmission potentialities of his devices. The infant electric-power industry had too many difficulties on its hands in working out its destiny in the light of known principles and practices to spend much time or money or energy on totally untried projects or those involving little understood principles. Still another reason may be that the early successes of the Marconi and Slaby-Arco systems of wireless telegraphy without the use of the excessive voltages on which Tesla was so insistent, together with the (apparently) necessary connection between relatively low frequencies and long-distance transmission, created the impression that Tesla's techniques had nothing to offer the new art.

As to his own development of high-frequency applications, it is apparent from a study of his patent specifications that, while he was perfectly aware of the possibilities of his high-frequency devices for space cornmunications and understood that signals for this purpose might be propagated as electromagnetic waves (see, for example, the patent specification 613,809, of 1898), nevertheless he seems to have assumed that such propagation would be effective only for relatively short distances. He apparently thought that world-wide communications would be effected either by some form of corpuscular or electronic convection in the stratosphere or through the earth by alteration of its charge. If his knowledge of electrical science outside of the domains of a-c circuits had been more adequate, or if he had followed up experimentally the communication potentialities of his earlier inventions, his great talents would probably have led to much more fertile results.

Whatever may have been the cause, it is nevertheless the fact that, in comparison with the effect of his development of the induction motor on the electric-power industry, Tesla's contributions to the high-frequency field have been remarkably sterile. Of the well-known earlier treatises on radio, that of Fleming refers to Tesla's high-frequency alternator and oscillation transformer, those of Pierce and Zenneck refer only to the oscillation transformer among the Tesla inventions, and in any text published since about 1915 there is rarely even the mention of his name. The young radio engineer of today may very well complete his formal education without ever having heard of Tesla, except in connection with the induction motor and the rotating field, or possibly as the “father” of the neon-tube lamp.

This seems somewhat unfortunate, for a perusal of his pertinent patent specifications would appear to indicate that, although not exploited effectively for communication purposes, there are at least three matters of prime importance to the radio art today on which Tesla's ideas were clearer than those of his contemporaries and on which he is entitled to either distinct priority or independent discovery. These are:

1. The idea of inductive coupling between the driving and the working circuits.

2. The importance of tuning both circuits, that is, the idea of an “oscillation transformer.”

3. The idea of a capacitance loaded open secondary circuit.

It seems incontestable that all three of these fundamental ideas are clearly revealed in Tesla's patent specifications and lectures prior to 1894, although their application to communication purposes, while mentioned, is made incidental to the power-transmission objective. As none of these ideas appear in the specific literature of the radio art prior to the patent specifications of Marconi, Lodge, and F. Braun of the years 1897-1900, it would seem that Tesla's name is worthy of perpetuation as a pioneer of these ideas which have been so basic in the radio art down to the present. He never succeeded, however, in translating these ideas into an operative system for the transmission either of signals or power. A study of the group of patents issued to him at the turn of the century would seem to indicate that he did not realize the importance of the effect of antenna capacitance on the tuning of its circuit. Thus his proposed system was highly inefficient, if not inoperative. Hence, while he fairly may be considered a pioneer of the fundamental ideas already mentioned, he cannot be rated as the progenitor of their useful application, except as his work was a stimulus to others.

In addition to this major pioneering activity, Tesla made at least two contributions specifically in the communications field that are not generally known. The first is that embodied in the patent specification 613,809, dated November 8, 1898 (application July 1, 1898), entitled “Method of and apparatus for controlling mechanism of moving vessels or vehicles.” This method of remote control operates on a succession of radio impulses whose incidence on a receiving antenna energizes through relays the battery-powered steering and propelling motors of the moving vessel and whose sequency and duration (at the will of the operator) determine the direction and amount of rudder rotation.

The inventor states that any method of producing the radio impulses (whether invented by himself or others) may be used, and that their propagation may be by means of Hertzian waves or by the mechanisms (previously mentioned) that he favored. Without passing on the operative merits of the proposed system, it would seem to the author that this invention deserves mention as the earliest radio remote-control system with which he is acquainted. A minor matter of interest in this specification is the very ingenious decohering device employed — one quite different from those in common use at the time and perhaps more certain in its action.

The second of these less known contributions is contained in patent specifications 685,957 and 685,958 of November 5, 1901 (application March 21, 1901), entitled “Apparatus for the utilization of radiant energy” and “Method of utilization of radiant energy,” respectively. These describe a scheme which, in so far as it would be actually operative, depends on the changes in the charge on a capacitor produced by the incidence of the radiation (light) on an elevated-capacitance plate antenna connected to one of the capacitor terminals. It is thus seen to embody an application of the photo-electric effect discovered by Hertz in 1887, although Tesla seems to have been ignorant of that fact, and the explanation he offers is largely fallacious. It is not necessary to go into any of the details of these specifications. They are mentioned here only as illustrative of the experimental keenness which independently rediscovered the Hertz effect and the ingenuity involved in finding a possible application for it. As far as the author is aware, this is the only suggestion of such an application on record.

After studying his patent specifications and the record of his public lectures, the author, in attempting to integrate and evaluate his impressions of Tesla and his work in the high-frequency field, has arrived at a mental picture of an immensely energetic personality possessing great skill in a-c techniques and great ingenuity in their practical utilization. There also emerges the image of a man unable to realize the limitations of his knowledge in other fields of science and the futility of mere ingenuity to overcome that handicap. These characteristics, combined with intense tenacity of purpose, resulted in the perversion of great talents into a largely unproductive direction. Nevertheless, his earlier accomplishments mentioned herein, together with the inspiration given to many through his public lectures,¹⁷ would seem to justify a place in the history of radio engineering not so very far below that due to his accomplishments in the field of low-frequency alternating currents.

III — Addenda

Tesla's Early Papers and Lectures

1888 — A New System of Alternate-Current Motors and Transformers. AlEE Transactions, volume 5, 1888, page 305.

1891 — Experiments With Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination (AlEE lecture at Columbia University). AlEE Transactions, volume 8, 1891, page 267.

1892 — Experiments With Alternate Currents of High Potential and High Frequency. Journal, Institution of Electrical Engineers (London, England), 1892, page 51.

1893 — Light and Other High-Frequency Phenomena. (Delivered twice.) (1) Franklin Institute, Journal, July 1893; (2) National Electric Light Association Proceedings, 1893.

Books

1892 — Experiments With Alternate Currents of High Potential and High Frequency (Tesla's London lecture). W. J. Johnston Company, New York, N. Y., 1892. 146 pages. Out of print.

1894 — The Inventions, Researches, and Writings of Nikola Tesla; with special reference to his work in polyphase currents and high-potential lighting, Thomas Commerford Martin (past president AlEE). 493 pages. Out of print.

1932 — Nikola Tesla und Sein Werk, DipI.-lng. Slavko Boksan, Copyright 1932 by Deutscher Verlag fur Jund und Volk, Gesellshaft M Blf, Vienna I Burgring 9. Printed in Austria, Buchrrucherei Carl Gerold's Sohn, Vienna, VIII, Hamerling, platz 10. 344 pages. An encyclopaediac treatise.

1936 — Nikola Tesla-Memorandum Book on the Occasion of his 80th Birthday, Edition de la Societe pour la Fondation de I'lnstitut Nikola Tesla. 520 pages, Belgrade, 1936. The sponsoring foundation was established by the government for research. Sixty delegates from scientific institutions in 13 foreign countries joined the officers and members of the Yugoslav nation in conferences at Belgrade, May 26 to 31, 1936, followed by one-day celebrations at Zagreb (University) and Smiljane [sic] (Tesla's birthplace). Subsequent meetings were held in Paris, Vienna, and other European cities. Papers are printed in the seven languages in which they were written. Tables and reprints add to completeness. Tesla is credited (1936) with 113 United States patents: polyphase currents, 41; high-frequency currents and high voltage, 29; wireless systems, 18; others 25.

Among Anniversary Greetings in the “Memorandum Book” are the following:

Robert A. Millikan: “When I was a student in Columbia University I attended a downtown public lecture in New York at which you made one of the first demonstrations of your Tesla coil and its capabilities. Since then I have done no small fraction of my research work with the aid of the principles I learned that night.”

Arthur H. Compton: “To men like yourself, who have learned first hand the secrets of nature and who have shown us how her laws may be applied in solving our every- day problems, we of the younger generation owe a debt that cannot be paid.”

Lee De Forest: “No one so excited my youthful imagination, stimulated my inventive ambition, or served as an outstanding example of brilliant achievement in the field I was eager to enter, as did yourself. Your simple statement that you knew I could succeed, renewed my courage and gave me new faith in myself at a time when I was sorely tried.”

Cano Dunn: “My contact as your assistant at the historic Columbia University high-frequency lecture and afterward has left an indelible impression and an inspiration which has influenced my life.”

D. McFarlan Moore: “You fanned into a never-dying flame my latent interest in gaseous conduction.”

E. F. Northrup: “When I began to give consideration to electrical methods for melting metal, my mind at once went back to those early demonstrations by you and the electric circuits which you described.”

Tesla said in his London lecture that his aim was “to advance ideas which I am hopeful will serve as starting points for new departures.” His success is attested by his followers.

References

1. Niagara Power — History of The Niagara Falls Power Company, 1886-1918. — Evolution of its Central Power Station and Alternating-Current Power System (two volumes), Edward Dean Adams (John Fritz medalist). Privately printed for Niagara Falls Power Company, 1926, Page ix,
2. On an Electromagnetic Machine Constructed at the Cornell University Work Shop, W. A. Anthony (Past president AlEE). American Journal of Science and Arts, October 1876, page 251.
3. Some Reminiscences of Early Electric Lighting, Charles F. Brush (Past president, AlEE. Edison Medalist); The Pioneer Investigations on Dynamo Machines Fifty Years Ago, Elihu Thomson (Past president AlEE; Edison medalist). Professor Thomson refers to assistance by one of his “most promising pupils.” E. W. Rice (Past president, AlEE. Edison Medalist). Journal of the Franklin Institute, volume 206, number 1231, July 1928.
4. Electrical World, May 25, 1889, page 293.
5. Report on the Exhibits at the Crystal Palace Electrical Exhibition, 1882, Ensign Frank J. Sprague (Past president AlEE, Edison medalist). Navy Department, Bureau of Navigation, Office of Naval Intelligence, 1884. Washington Government Printing Office (His British Association for the Advancement of Science paper is on page 448 of its 1882 Proceedings).
6. Patent 469,809; William Stanley — “I conceived the idea of so proportioning the converter as to secure a variation of the counterelectrornotive force in the primary proportional to the current abstracted from the secondary.” Object, parallel operation. Specification for “Induction Patent,” sent to attorney November 26, 1885. Application for patent, August 15, 1888. In interference with Slatterly patent 269,750, dated July 31, 1888. Patent issued March 1, 1892.
7. Patent 342,553; George Westinghouse — Transformer (H plate). .Patent application made February 16, 1886; issued May 28, 1886. See Mechanical Development of Transformer by Westinghouse, Charles F. Scott. Electrical Engineering, December 1936, p. 1403. Contains description of the H plate, with drawing from patent. See also “Early Days of the Transformer,” interview with Reginald Belfield, Electrical World, November 1,1930, page 918.
8. Early History of A-C System in America. C. C. Chesney, C. F. Scott. Electrical Engineering, March 1936, page 228. In the introduction we find: “As part of the Institute's celebration of the 50th anniversary of the establishment of the a-c system in America ... the early history has been prepared by two past presidents of the Institute, both of whom were actively identified with the early development of the system.” (Westinghouse, Stanley, Chesney, and Scott are Edison medalists.)
9. Niagara Power (see reference 1). The International Niagara Commission, Volume I; organization, page 181; report on projects, page 401. “Niagara Power” describes the evolution of plans and apparatus culminating in the adoption of the Tesla polyphase system. It elaborates many of the condensed statements in the present paper.
10. Electrical World, November 7, 1891, page 346.
11. Exhibit of Polyphase System at the World's Fair, Charles F. Scott. Proceedings, International Electrical Congress, Chicago, 1893, page 417. Published by AlEE, 1894.
12. New York Electrical Handbook (one of 11 handbooks). A guide for foreign visitors to the International Electrical Congress, St. Louis, Mo. AlEE, 1904.
13. George Westinghouse Commemoration. A forum on the 90th Anniversary (t 936) of his birth. American Society of Mechanical Engineers. 78 pages; also Mechanical Engineering, April 1937. Includes contributions on the steam turbine by Keller, Hodgkinson, and Smith, and alternating current by Berresford, Stillwell, and Beardsley.
14. The New Epoch as Developed by the Manufacture of Power, George S. Morison. Houghton Mifflin and Company, 1903. 134 pages. Out of print. A recast of his presidential address (American Society of Civil Engineers), 1895, and other ad- dresses. Reviewed by Colonel Prout in Electric Journal, September 1906, page 494; also in his “A Life of George Westinghouse,” page 325. The latter recounts the development of alternating current, including the World's Fair and Niagara installations.
15. Electrical World, January 23, 1943, page 90.
16. Edwin H. Armstrong (Edison Medalist 1942) in a letter to the author commenting on a draft of, “Tesla's Contribution to Electric Power.”
17. See anniversary greetings, in “Nikola Tesla — Memorandam Book on the Occasion of His 80th Birthday,” listed under “Books.”
18. Nikola Tesla. For items on presentation of Edison Medal, see Proceedings AlEE, June 1917, and current issues of Electrical World and of Western Electrician. A biographical obituary item appears in Electrical Engineering; volume 62, February 1943, page 76.