He was not approaching an entirely unknown realm in which he would have to feel his way in darkness in the hope of stumbling upon something of value, although anyone else at that time would have been in that position. On that fateful afternoon in February in Budapest in 1882, when he was given the vision of the rotating magnetic field, there had come with it an illumination that revealed to him the whole cosmos, in its infinite variations and its myriad of forms of manifestations, as a symphony of alternating currents. For him, the harmonies of the universe were played on a scale of electrical vibrations of a vast range in octaves. In one of the lower octaves was a single note, the 60-cycle-per second alternating current, and in one of the higher octaves was visible light with its frequency of billions of cycles per second.

Tesla had in mind a course of experimentation in which he would explore this region of electrical vibration between his alternating current and light waves. He would increase the frequency of the alternating current through the unknown intervening regions. If one note in a lower octave produced such a magnificent invention as the rotating magnetic field and the polyphase system, who could imagine the glorious possibilities that lay hidden on other notes in higher octaves? And there were thousands of octaves to be explored. He would construct an electrical harmonium by producing electrical vibrations in all frequencies, and study their characteristics. He would then, he hoped, be able to understand the motif of the cosmic symphony of electrical vibrations that pervaded the entire universe.

Tesla, at the age of thirty-three, was now wealthy. He had received $1,000,000 from the Westinghouse Company for his first crop of inventions. Of this, $500,000 went to A. K. Brown and his associate who had financed his experiments. Still greater inventions were to follow. He would never need money. He would, he then believed, have royalties in the millions from his alternating-current patents. He could spend as freely as he wished, penetrating the secrets of Nature and applying his discoveries to human welfare. It was his responsibility to be so engaged. He knew he was gifted as no other man had been blessed with vision, talent and ability; and he in turn would endow the world with supernal treasures of scientific knowledge which he would extract from the secret recesses of the universe and, through the activities of his mighty mind, transform into agencies to brighten the lives, lighten the labors and increase the happiness of the human race.

Was he a superegoist in his attitude? If so, he was not activated by selfish motives. To him it mattered not what he thought, so long as he remained objective in his thinking and his thoughts could be translated into demonstrable facts. What if he did consider himself greater than other men: did not this viewpoint conform to the facts? Suppose he did consider himself a man of destiny. Could he not bring evidence to support the contention? It was not necessary for Tesla actually to see an event occur in order to enjoy its realization. Had he not as a youth declared that he would make a practical alternating-current motor, only to be told by his professor that the goal was impossible of attainment--and had he not already accomplished this "impossibility"? Had he not taken the direct-current dynamos of Edison, whom all the world looked upon as a great genius, and had he not greatly improved their design and operation; and in addition, had he not produced a vastly superior system for producing, distributing and using electricity? To all of these inquiries Tesla could answer in the affirmative without going beyond the bounds of modesty concerning his achievements.

His attitude was not that of an egoist. It was an attitude of supreme faith in himself and in the vision that had been given him. To a man of ability, with such supreme faith in himself, and necessary financial resources to advance his purposes, the world of accomplishments is without limits. This was the picture of Tesla as he returned to his laboratory in lower Fifth Avenue, New York, in the latter part of 1889.

Tesla had studied a wide range of frequencies of alternating current in order to select the frequency at which his polyphase system would operate most efficiently. His calculations indicated important changes in characteristics and effects as the frequency of the current was increased; and his observations with the electrical machinery he built confirmed his calculations. He noted that ever smaller quantities of iron were required as the frequencies were increased, and he now wished to explore the very high frequencies at which unusual effects should be produced without any iron in the magnetic circuit.

When, back in Budapest following his rotating magnetic-field discovery, he had played with mental calculations of the properties of alternating currents all the way from the very lowest frequency up to that of light, no one had yet explored this region. James Clerk Maxwell, at Cambridge University, England, had, however, nine years before, in 1873, published his beautiful presentation on an electromagnetic theory of light, and his equations indicated that there was a vast range of electro-magnetic vibrations above and below visible light--vibrations of much longer and much shorter wavelengths. While Tesla was engaged in making models of his polyphase system in 1887, too, Professor Heinrich Hertz, in Germany, put the Maxwell theory to test in the range of waves a few meters long. He was able to produce such waves by the spark discharge of an induction coil, and was able to absorb such waves from space and change them back to a small spark at some distance from the coil.

Hertz's work gave support to Tesla's theory that there was an interesting discovery to be made on almost every note of the whole gamut of vibrations between the known ones of the electrical current and those of light. Tesla felt sure that if he could continually increase the frequency of electrical vibrations until they equaled that of light, he would be able to produce light by a direct and highly efficient process instead of the extremely wasteful process used in the Edison incandescent lamp, in which the useful light waves were a very small fraction of the wasted heat waves emitted in the process, and only five per cent of the electrical energy was effectively utilized.

Tesla started his investigations by building rotary alternating-current dynamos with up to 384 magnetic poles, and with these devices he was able to generate currents up to 10,000 cycles per second. He found that these high-frequency currents presented many fascinating possibilities for even more efficient power transmission than his very practical 60-cycle polyphase system. He therefore carried on a parallel line of research into transformers for raising and lowering the voltage of such currents.

High-frequency alternating-current dynamos, similar to those designed by Tesla in 1890, were subsequently developed by F. W. Alexanderson into the high-power wireless transmitters which put transatlantic wireless transmission, more than two decades later, on such a sound practical basis that the Government would not permit control of it to go to a foreign country and preserved for the United States its predominant position in world wireless.

The high-frequency current transformers which Tesla developed proved to be spectacular performers. They contained not a trace of iron; as a matter of fact, the presence of iron was found to interfere with their operation. They were air-core transformers and consisted merely of concentric primary and secondary coils. The voltages he was able to produce with these transformers, which became known as Tesla coils, were very high. In the early experiments he attained potentials that would spark across a couple of inches of air, but in a short time he made tremendous progress and was producing flaming discharges. In working with these voltages he encountered difficulties in insulating his apparatus, and so he developed the technique that is now in universal use in high-tension apparatus: that of immersing the apparatus in oil and excluding all air from the coils, a discovery of great commercial importance.

There was a limit, however, above which the use of rotary generators of high-frequency currents was not practicable, so Tesla set about the task of developing a different type of generator. There was nothing novel about the basic idea he employed. In rotary dynamos, current is generated by moving a wire in a circle past a number of magnetic poles in succession. The same effect can be attained by moving the wire back and forth with an oscillating motion in front of one magnetic pole. No one, however, had as yet produced a practical reciprocating dynamo. Tesla produced one that was extremely practical for his particular purpose; but otherwise it had little utility, and he later felt that he could have employed much better the time he spent on it. It was an ingenious single-cylinder engine without valves, and could be operated by compressed air or steam. It was supplied with ports like a small two-cycle marine engine. A rod extended from the piston through the cylinder head at either end, and at each end of the rods was attached a flat coil of wire which, by the reciprocating action of the piston, was caused to move back and forth through the field of an electromagnet. The magnetic field through its cushioning effect served as a flywheel.

Tesla was able to obtain a speed of 20,000 oscillations per minute, and to maintain such a remarkable degree of constancy in operation that he proposed the maintenance of equally constant speed of operation for his 60-cycle polyphase system and the use of synchronous motors, geared down to the proper extent, as clocks which would furnish correct time wherever alternating current was available. This proposal furnished the foundation for our modern electric clocks. As with many another of his practical and useful suggestions, he did not take out a patent on the idea, and gained no financial advantage from it.

In working with his polyphase system, Tesla gained a thorough understanding of the part played by the two factors, capacity and inductance, in alternating-current circuits; the former acting like a spring and the latter like a storage tank. His calculations indicated that with currents of sufficiently high frequency it would be possible to produce resonance with relatively small values of inductance and capacity. Producing resonance is tuning a circuit electrically. The mechanical effects analogous to electrical resonance are the causing of a pendulum to swing through a wide arc by giving it a series of very light but equally timed touches, or the destruction of a bridge by soldiers marching in unison over it. Each small vibration re-enforces its predecessors until tremendous effects are built up.

In a tuned electrical circuit a condenser supplies the capacity and a coil of wire supplies the inductance. A condenser ordinarily consists of two parallel metal plates separated from each other a short distance by an insulating material. Each plate is connected to either end of the inductance coil. The size of the condenser and the coil is determined by the frequency of the current. The coil-condenser combination and the current are tuned to each other. The current can be pictured as flowing into the condenser until it is fully charged. It then flows elastically into the inductance coil, which stores the energy by building up its magnetic field. When the current ceases to flow in the coil, the magnetic field collapses and gives back to the coil the energy previously used in building up the magnetic field, thus causing a current to flow back into the condenser to charge it up to overflowing again, so that it is ready to repeat the process. This flow back and forth between the condenser and coil takes place in step with the periodic reversal of the alternating current which supplies the energy when resonance is established. Each time it takes place, the charging current comes along at the right instant to give it a boost, so that the oscillations build up to tremendous values.

Tesla, in discussing this plan of electrical tuning of circuits in a lecture, given several years later, said:

The first question to answer then is whether pure resonance effects are producible. Theory and experiment show that such is impossible in nature for, as the oscillations become more vigorous, the losses in vibrating bodies and environing media rapidly increase, and necessarily check the vibrations, which would otherwise go on increasing forever. It is a fortunate circumstance that pure resonance is not producible for, if it were, there is no telling what dangers might lie in wait for the innocent experimenter. But, to a certain degree, resonance is producible, the magnitude of the effects being limited by the imperfect conductivity and imperfect elasticity of the media, or, generally stated, frictional losses. The smaller these losses the more striking are the effects.

Tesla applied the electrical tuning principles to his coils and discovered that he was able to produce tremendous resonance effects and build up very high voltages. The tuning principles he developed in 1890 are those which have made our modern radio, and the development of the earlier art, "wireless," possible. He had been working with, and demonstrating, these principles before others who received credit had begun to learn the first lessons in electricity.

Seeking a new source of high-frequency currents, higher than could be produced by any mechanical apparatus, Tesla made use of a discovery that had been made the year in which he was born, by Lord Kelvin, in England, in 1856, and for which no use had thus far been found. Up to the time of Kelvin's discovery it had been believed that when a condenser was discharged the electricity flowed out of one plate into the other, like water being poured from a glass, thus establishing equilibrium. Kelvin showed that the process was far more interesting and complex; that its action was like the bobbing up and down that takes place when a weighted stretched spring is released. The electricity, he showed, rushes from one plate into the other and then back again, the process continuing until all of the stored up energy is used up in overcoming frictional losses. The back-and-forth surges take place at a tremendously high frequency, hundreds of millions a second.

The combination of condenser discharges and tuned circuits opened a new realm in electrical science as significant and as important as Tesla's polyphase system. He worked out remarkably simple and automatic methods for charging the condensers by low voltage (direct and alternating currents), and discharging them through his new air-core transformers, or Tesla coils, to produce currents of enormously high voltages that oscillated at the tremendously high frequency of the condenser discharge. The properties of these currents were unlike anything that had been seen before. He was again pioneering in an entirely new field, with tremendous possibilities. He labored feverishly in his laboratory; and as he lay in bed at night for his five-hours' rest, which included two hours of sleep, he formulated new experiments.

Tesla announced the heating effect of high-frequency currents on the body in 1890 and proposed their use as a therapeutic device. In this he was a pioneer, but soon had many imitators here and abroad who claimed to be originators. He made no effort to protect his discovery or prevent the pirating of his invention. When the same observation was made thirty-five years later in laboratories using vacuum-tube oscillators as the source of the high-frequency currents, it was hailed as a new discovery and developed as a modern wonder. Tesla's original discovery is, however, the basis of a vast array of very recent electronic applications in which high-frequency currents are used to produce heat for industrial purposes.

When he gave his first lecture on the subject before the American Institute of Electrical Engineers at Columbia College, in May, 1891, he was able to produce spark discharges five inches long, indicating a potential of about 100,000 volts, but, more important, he was able to produce phenomena which included, electrical sheets of flame, and a variety of new forms of illumination--electric lamps the like of which had never been seen before, nor dreamed of in the wildest imagination of any experimenter.

This lecture produced a sensation in engineering circles. He was already famous in this field for the astounding revelations he had made before the same organization on that earlier occasion when he described his discovery of the polyphase alternating current system. That discovery was an intellectual accomplishment of bewildering brilliance, made impressive by the tremendous commercial importance of the discovery. The experiments with the high-frequency and high-potential currents, however, were spectacular; the crackling of the high-voltage sparks, the flashing of the high-potential sheets of electrical flame; the brilliant bulbs and tubes of electrical fire, the amazing physical effects he produced with the new currents, made a profound emotional appeal to the startled beholders.

The man who could produce these two pioneering developments within two years must be more than a genius! The news of his new accomplishment flashed quickly throughout the world, and Tesla's fame now rested on a double foundation.

The world-wide fame that came to him at this time was unfortunate. Tesla would have been entirely superhuman had he not derived a great deal of satisfaction out of the hero-worshiping adulation that now came to him. It was only five years ago that he had been hungry and penniless in the streets of New York, competing with equally hungry hordes of unemployed for the few existent jobs calling for brute labor, while his head bulged with important inventions which he was anxious to give to the world. No one would listen to him then--and now the intellectual élite of the nation were honoring him as an unrivaled genius.

Tesla was a spectacular figure in New York in 1891. A tall, dark,

handsome, well-built individual who had a flair for wearing clothes that gave him an air of magnificence, who spoke perfect English but carried an atmosphere of European culture which was worshiped at that time, he was an outstanding personality to all who beheld him. Hidden behind his quiet, self-effacing demeanor, and an extreme modesty that manifested itself as an exaggerated shyness, was the mind of a genius which had worked electrical wonders that fired the imagination of all and exceeded the understanding of the vast majority of the population. In addition Tesla was a young man, not yet thirty-five, who had recently received a million dollars and was a bachelor.

A bachelor with a million dollars, culture and fame, could not avoid being a shining mark in New York in the early years of the gay nineties. Many were the designing matrons with marriageable daughters who cast envious eyes in the direction of this eligible young man. The social leaders looked upon him as a fascinating decoration for their salons. The big men of business looked upon him as a good man to know. The intellectuals of the day found his almost unbelievable accomplishments a source of inspiration.

Except at formal dinners Tesla always dined alone, and never under any circumstances would he dine with a woman at a two-some dinner. No matter how much a woman might gush over him or strive to gain his favor, Tesla, in most adamant fashion, maintained a thoroughly impersonal attitude. At the Waldorf-Astoria and at Delmonico's he had particular tables which were always reserved for him. They occupied secluded positions in the dining rooms because when he entered either room he was the cynosure of all eyes and did not enjoy being on exhibition.

In spite of all of the adulation that was heaped upon him, Tesla had but one desire--to continue his laboratory experiments undisturbed by outside distractions. There was a tremendous empire of new knowledge to be explored. He was fired with a potential of enthusiasm for the work that was as high as the voltage of the currents with which he was working, and new ideas were coming to him with almost the rapidity of the cycles in his high-frequency current.

There were three broad fields in which he wished to develop applications which were now clearly outlined in his mind: a system of wireless power transmission that would excel his own polyphase system, a new type of illumination, and the wireless transmission of intelligence. He wished to work on them all simultaneously. They were not separate and isolated subjects but all closely intermeshed, all notes on that vast cosmic scale of vibration represented by his beloved alternating currents. He did not wish to play on one note at a time, as would a violinist; he preferred to play as a pianist, striking many notes at once and weaving them into beautiful chords. Were it possible to occupy the position of leader and simultaneously play all of the instruments in a great symphony orchestra, he would have been still better pleased. The instruments in his orchestra, however, would be electrical devices oscillating in tune with their energizing currents or with their environment. To the extent that he was unable to realize his most expansive desires, he was under mental pressure that drove him to a working pace which no individual of ordinary strength could withstand without a resulting complete physical breakdown.

The spectacular lecture and demonstration on high-frequency and high-potential currents which he gave before the American Institute of Electrical Engineers in February, 1891, at Columbia College, created as profound a sensation as did his earlier one. Each opened an entirely new realm of scientific investigation and practical discoveries. The discoveries contained in either lecture would have been sufficient to stand as the fruit of a lifetime's work and bring lasting fame. Two such events in rapid succession seemed almost unbelievable--yet Tesla seemed to be scarcely well launched on his career, with more important work still to come.

Requests that he give lectures came from learned societies throughout this country and Europe, but he begged to be excused because of the tremendous pressure on his time which his work entailed. Equally insistent were the social demands that were being made upon him. Social groups sought in every way to honor him, and incidentally to shine in his reflected glory. Tesla was not vulnerable to the importunings of the socialites who sought him merely as a scintillating satellite, but the clever "lion hunters" of that day soon discovered his Achilles' heel--an intelligent interest in his accomplishments and a sympathetic ear for his dreams of wonders still to come.

With this technique in successful operation, Tesla was captured and soon completely lionized. He was guest of honor at a continuous round of functions and he met the social obligations involved in them by staging, in return, elaborate dinners at the Waldorf-Astoria followed by demonstration parties at his laboratory on South Fifth Avenue. Tesla never did a halfway job on anything. When he staged a dinner he left nothing to chance in the matter of cuisine, service and decorations. He sought rare fish and fowl, meats of surpassing excellence, and choicest liquors and exquisite wines of the best vintages. His dinners were the talk of the town and having been a guest at a Tesla dinner was a mark of social distinction, proof of membership in the inner group of the élite within Ward MacAllister's "400." At these dinners Tesla presided as a most meticulous host, or more accurately, as an old-world absolute monarch, for he would sample all food brought to the dining room; and rarely did an event pass without the grandiose host sending back some sauce or wine of unquestioned excellence as unworthy of his guests.

Following each of these meals Tesla would escort his guests to his laboratory below Washington Square; and here his demonstrations were even more spectacular than his dinners. He had a flair for the dramatic; and the strange-looking devices with which his laboratory was furnished provided a grotesque and bizarre background for the fantastic displays of seemingly unearthly forces that with invisible fingers set objects whirling, caused globes and tubes of various shapes to glow resplendently in unfamiliar colors as if a section of a distant sun were suddenly transplanted into the darkened room, and crackling of fire and hissing sheets of flame to issue from monster coils to the accompaniment of sulfurous fumes of ozone produced by the electrical discharges that suggested this magician's chamber was connected directly with the seething vaults of hell. Nor was this illusion dispelled when Tesla would permit hundreds of thousands of volts of electricity to pass through his body and light a lamp or melt a wire which he held.

The amazing feat of harmlessly passing through his body currents of tremendously high voltage and high frequency was one which Tesla evolved by his mental experiments long before he had an opportunity to test them in his laboratory. The low-frequency alternating currents, such as are now used on home-lighting circuits, would, he knew from unpleasant experiences, produce a painful shock if passed through the body. When light waves impinged on the body, however, no such painful sensation was produced. The only difference between the electric currents and light waves, he reasoned, was a matter of frequency, the electric currents oscillating at the rate of 60 per second and the light waves at billions per second.

Somewhere between these two extremes the shock-producing property of electromagnetic vibrations must disappear; and he surmised the point would be near the lower end of the gap. Damage done to the body by electric shock he divided into two factors, one--the destruction of tissues by the heating effect which increased or diminished as the amperage of the current was raised or lowered; and two--the sensation of acute pain which varied with the number of alternations of the current, each alternation producing a single stimulus which was transmitted by the nerves as a pain.

Nerves, he knew, could respond to stimuli up to a rate of about 700 per second, but were unable to transmit impulses received at a more rapid rate. In this respect they acted very much like the ear, which is unable to hear air vibrations above a frequency of about 15,000 per second, and the eye, which is blind to color vibrations of a frequency higher than that in violet light.

When he constructed his high-frequency alternating-current dynamos, he had frequencies up to 20,000 per second with which to test his theory; and by finger tests across the terminals he was able to demonstrate that the nerves were unable to perceive the individual vibrations at this rapid rate. The amperage, which carried the tissue-destroying power, was still too high in the output of these machines to pass safely through his body, even though the sensation of pain was lacking.

By passing these currents through his newly invented air-core transformers, he could increase their voltage ten-thousand fold and reduce the amperage proportionately. The current density would thereby be reduced below the point at which it would injure tissues. He would then have a current which would not produce sensation and would not harm the tissues. He cautiously tested the theory by passing the currents through two fingers, then his arm, next from hand to hand through his body and finally from his head to his feet. If a spark jumped to or from his body, there was a pin-prick sensation at the point of contact, but this could be eliminated by holding a piece of metal to and from which the spark could jump while the current passed through the tissues without producing any sensation.

The energy content of these currents, which is proportionate to the current multiplied by the voltage, could be very high and produce spectacular effects such as melting metal rods, exploding lead disks, and lighting incandescent or vacuum-tube lamps after passing painlessly through his body.

The European scientific societies were persistent in their efforts to induce Tesla to accept their invitations to lecture before them, and finally he acceded. He set extravagantly high standards for the contents of his lectures, and their preparation entailed a tremendous amount of labor. All of the material had to be entirely new. He would never repeat an experiment previously presented. Every technical statement had to be tested at least twenty times to insure complete accuracy. His lectures would last two or three hours; and every minute of the time was crowded with new and awe-inspiring demonstrations of his constant stream of discoveries. He used a great array of devices fashioned by himself and built in his own laboratories to illustrate his talks. A Tesla lecture, therefore, was an extremely important event in the scientific world and a most impressive occasion to those who were fortunate enough to be able to attend.

Tesla arranged to give a lecture before the Institution of Electrical Engineers in London on February 3, 1892, and one before the International Society of Engineers in Paris on February nineteenth. His decision to give the European lectures was influenced to some extent by the fact that they would afford him an opportunity to visit his home in Gospic, for recent letters had indicated that his mother's health was failing.

The lecture before the Institution of Electrical Engineers was a great success. English engineering journals, as will be seen, had been niggardly in extending recognition to Tesla for priority in the discovery of the rotating magnetic field, and had belittled the practical value of his polyphase alternating-current system, but in this attitude they were not representative of the great body of engineers, who were most generous in their praise and enthusiasm; and the attitude of the engineers was shared by the English scientists.

When Tesla arrived in London he was entertained at many places by famous men. At the Royal Institution, where the immortal Michael Faraday had carried on his fundamental researches in magnetism and electricity, Sir James Dewar, and a committee of equally famous scientists, sought to prevail upon Tesla to repeat his lecture before that organization. Tesla could be plain stubborn in sticking to his plans, and in this case was exhibiting his usual firmness. The famous Scottish scientist matched Tesla's stubbornness with an equal persuasive persistence. He escorted Tesla to Faraday's chair, an almost sacred relic to English science, seated him in this throne, and then brought out an almost equally precious heirloom, a portion of a bottle of whiskey, the remainder of Faraday's personal supply, untouched for nearly a quarter of a century. Out of this he poured a generous half glass for Tesla. Sir James won. Tesla relented and gave the lecture the following evening.

Lord Rayleigh, the eminent English physicist, was chairman of the meeting at the Royal Institution, which was attended by the élite of the scientific world and a generous representation of the nobility of the realm. Rayleigh, after witnessing the performance of Tesla's experiments, which were none the less awe inspiring to scientists than to laymen, showered words of praise on the inventor.

Rayleigh declared that Tesla possessed a great gift for the discovery of fundamental scientific principles, and urged that he concentrate his efforts on some one big idea.

Tesla, in his conversation after the meeting, disclaimed ability as a great discoverer; but in this he was merely being modest, for he knew that he was unique among men in his ability to discover fundamental truths. He did, however, give very serious consideration to Rayleigh's suggestion that he concentrate on some one big idea. It is doubtful, however, whether Rayleigh's suggestion was good advice. Tesla's mind had a range that was cosmic in magnitude and adjusted to broad slashing advances through unknown regions. Rayleigh's advice was like suggesting to an explorer who had unique ability for penetrating an unknown continent and opening it to civilization that he settle down and cultivate a homestead, since that would give more definite and specific returns for efforts expended.

Two weeks later Tesla gave his scheduled lecture before the Physical Society in Paris and repeated it before the International Society of Electrical Engineers. This was his second visit to Paris since he had quit his job with the Continental Edison Company in that city eight years before. Immediately after leaving the Westinghouse Company in the autumn of 1889--at which time, too, he completed his U.S. citizenship requirements--he had made a brief visit to Paris to attend the International Exposition. In the meantime, the fame of his polyphase system had spread to Europe; and to this was added the glory for his spectacular work with the new high-frequency currents. He was given a hero's reception in Paris, as well as in London.

It would be interesting to know what thoughts passed through the minds of the executives of the Continental Edison Company as they observed the tremendous contributions to science and industry by the engineer whose services they had lost through their penny-wise tactics when they were offered in 1883, and could undoubtedly have purchased for a relatively small amount, the polyphase system for which Westinghouse paid Tesla $1,000,000 five years later.

A tesla lecture was an avalanche of new and fascinating electrical

knowledge. He completely overwhelmed his listeners with a wealth of spectacular original experiments, and as a result almost every individual contribution lost its identity in the dazzling concentration of the whole galaxy of startling developments.

In the 1892 lectures, entitled "Experiments with Alternating Currents of High Potential and High Frequency," Tesla described many of his discoveries which are only coming into general use today and are being hailed as modern inventions. Among these are the "neon" and other gas-filled lamps, and phosphorescent lamps. Many of the discoveries described are still unutilized, including, as will be seen, the carbon or metallic-button incandescent lamp, requiring but a single wire connection; and still others, which he later discovered, were rich producers of the mysterious X-rays.

The transcript of these lectures runs to 40,000 words. Scores of pieces of apparatus were used and usually several experiments were performed with each. He described "wireless" lamps, glowing glass tubes that required no wire connection for their operation. He described motors which operated on one wire, and "wireless" or "no wire" motors. But perhaps the most important development he described was the sensitive electronic tube--the original of all our modern radio and other electronic tubes--which, he predicted, was the device that would permit receiving wireless telegraph messages across the Atlantic. Of all these discoveries we shall presently have more to say in detail.

It had been Tesla's intention to make a short visit to his early home in Gospic when his lectures were out of the way, but circumstances forced him to make the trip sooner than he expected. Returning to his hotel after delivering the second Paris lecture, he received word that his mother was gravely ill. He rushed to the railroad station, arriving in time to board a train just about to pull out. He telegraphed ahead for special transportation facilities to shorten his trip, and succeeded in reaching Gospic in time to see his mother alive. He arrived in the afternoon and she died that night.

The great anxiety from which Tesla suffered during his sleepless rush from Paris to Gospic caused a patch of hair on the right side of his head to turn white over night. Within a month its jet black color was restored naturally.

Almost immediately after his mother's death, Tesla contracted an illness which incapacitated him for many weeks. When he recovered, he visited his sister Marica, in Plaski, for two weeks. From there he went to Belgrade, the capital of Serbia, where he arrived in May and was received as a national hero.

During the weeks of enforced physical inactivity imposed on him by his illness, Tesla took stock of himself and became thoroughly dissatisfied with the manner in which he had been conducting his life. No human being could feel anything but a pleasurable reaction in response to the adulation that had been heaped upon him during the past two years. Tesla, however, prided himself upon his wisdom in having so designed his life that he would not become a victim of human frailties, but would function far above the normal human level of physical limitations and intellectual activities. Now Tesla saw, in retrospect, that insofar as he had adhered to his superman plan of life, he had succeeded in achieving his goal of producing the works of a superman at a rate which astounded the world. When, however, he submitted to the first blandishments of the lion hunters after his New York lecture in May, 1891, he observed, social activities had cut into his available time and had interfered with his creative activities. He had let the "man magnificent" supersede his "superman," and two years of valuable time had been largely lost. In addition, he had spent that totally unproductive year at the Westinghouse plant. At the close of that period, he had vowed he would never again work for anyone. He now vowed that he would put an end to the vacuous social activities into which he had been inveigled.

It was not easy for Tesla to live up to his good resolutions, for his European trip had greatly enhanced his fame and triumphant celebrations were scheduled on his reappearance in New York. Nevertheless, he rejected all invitations. He returned to the Hotel Gerlach, where he lived a solitary existence. With a pent-up reserve of physical energy owing to his long abstinence from his heavy daily routine of work, he plunged with great vigor into his new program which was to open up new and enchanting realms of scientific wonders.