Originally published by Ives Washburn, New York, 1944; Published in Great Britain by Neville Spearman Ltd., 1968; Reprinted in the United States by Angriff Press, Los Angeles, 1973

(C)1994 Brotherhood of Life, Inc., 110 Dartmouth, SE, Albuquerque, New Mexico 87106 USA

New Typeset Edition - First printing, 1994, Reprinted 1996

Uploaded to the Internet October, 1996

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, without permission in writing from the publisher. Reviewers may quote brief passages.

ISBN 0-914732-33-1

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second part

FAME AND FORTUNE

EIGHT

RETURNING to his laboratory in March, 1893, after his European and American lectures, Tesla banished all social activities from his life program, and, bursting with energy, pitched headlong into experimental work in connection with his wireless system. He made repeated experiments in working out the reWnement of his principle of tuning circuits to resonance with each other. He built more than one hundred coils covering a wide range of electrical tuning characteristics. He also built numerous oscillators for producing high-frequency currents, and condensers and inductances for tuning both sending and receiving coils to any desired frequency or wavelength.

He demonstrated that he could cause any one of hundreds of coils to respond selectively and powerfully to its particular wavelength emitted by an oscillator while all others remained inert; but he discovered that tuned electrical coils have, to a further extent, the same properties as tuned musical string, in that they vibrate not only to the fundamental note but also to a wide range of upper, and particularly lower, harmonics. This characteristic could be usefully employed in connection with the design of sending- and receiving-station antennas, but it militated against the sharp, exclusive response tuning of coils. At close range, and with the powerful currents Tesla used in his laboratory, the harmonics were a handicap--when greater distance separated sending and receiving coils, this trouble became a minor one.

It became obvious to Tesla that it was going to be diYcult to arrange an early demonstration of his worldwide system of intelligence and of power, so he planned a compromise system in which he would use a smaller central transmitter and smaller relay stations at certain distances.

In an interview with Arthur Brisbane, the famous editor, Tesla announced in The World of July 22, 1894, the certainty of his plans. He said:

You would think me a dreamer and very far gone if I should tell you what I really hope for. But I can tell you that I look forward with absolute conWdence to sending messages through the earth without any wires. I have also great hopes of transmitting electric force in the same way without waste. Concerning the transmission of messages through the earth I have no hesitation in predicting success. I must Wrst ascertain exactly how many vibrations to the second are caused by disturbing the mass of electricity which the earth contains. My machine for transmitting must vibrate as often to put itself in accord with the electricity in the earth.

During the following winter he designed and built his transmitting station and a receiving station for this purpose. It worked well within the close range of the laboratory and between points in the city. Like the artist who is never willing to declare a picture Wnished but must continue to apply an unending series of slight improvements, Tesla continued to add reWnements so that he would be assured of a perfect test in the spring, when he planned to take his receiving set up the Hudson River on a small boat to test its response at extended distances.

With Tesla, as with Cæsar, though, came tragedy on the Ides of March. For Tesla it was the unlucky 13th of March, 1895, when Wre broke out during the night in the lower part of the building in which his laboratory was located and swept through the entire structure. The two Xoors on which his equipment was located dropped to the basement, their entire contents destroyed. Not a single article was saved. The major portion of Tesla's fortune was invested in the apparatus in that building. He carried no insurance on it. The loss was total.

The monetary loss was the least important factor in the shock which Tesla sustained. The apparatus and the countless experiments in scores of subjects with which they were associated were part of Tesla's self. His work of a lifetime was swept away. All of his records, papers, mementos, his famous World's Fair exhibit were gone. His laboratory, in which he had demonstrated his wonders to the élite and intelligentsia of New York, to the most famous men and women of the country and the world, was no more. And this tragedy had come just when he was ready to make his Wrst distance demonstration of his wireless system.

Tesla was in a tough spot Wnancially. The laboratory was the property of the Tesla Electric Company, owned by Tesla and A. K. Brown who had, with an associate, put up the funds to Wnance Tesla's demonstration of his polyphase alternating-current system prior to its sale to Westinghouse for $1,000,000. Some of that money was divided as cash among the associates, as stated; and the remainder had gone into the laboratory for further developments. The resources of the company were now wiped out and Tesla's individual resources were almost at the vanishing point. He was receiving some patent royalties from Germany on his polyphase motors and dynamos. This income would be adequate to take care of his living expenses but not suYcient to enable him to maintain an experimental laboratory.

Mr. Adams, active head of the Morgan group that had developed the hydroelectric station at Niagara Falls, using Tesla's polyphase system, now came to the inventor's rescue. He proposed and arranged for the formation of a new company which would Wnance the continuation of Tesla's experiments, and he oVered to subscribe one hundred thousand dollars of the proposed half-million dollars of capital stock of the company.

With this support Tesla proceeded to set up a new laboratory. He secured quarters at 46 East Houston Street, and started operations there in July, 1895, four months after his South Fifth Avenue laboratory had been destroyed.

Adams paid forty thousand dollars as the Wrst installment of his subscription. He took an active personal interest in Tesla's work, and spent a great deal of time in the laboratory. Knowing from the successful operation of the Niagara Falls plant that Tesla, technically, was extremely practical, Adams was deeply impressed by the plans for wireless transmission of intelligence and of power. He declared he was willing to go still further than his original plan of Wnancial support, and he proposed that the plan include the taking in of his son as an active partner in Tesla's work.

Such an arrangement would amount to an alliance for Tesla with the powerful Morgan Wnancial group. It was the support of J. P. Morgan that gave Wnancial guidance to the formation of the General Electric Company and made possible the building of the Waterside Station, the Wrst big Edison powerhouse in New York, and it was a Morgan group that, by making possible the development of Niagara, had given the Tesla system a tremendous boost. The prestige that would come from a Morgan association would probably be even more potent than the actual monetary aid involved. With this alliance Tesla's Wnancial future was assured. There would come to his aid, through it, the support of the world's greatest organizational genius and practical promotion powers. The tragedy of the Wre that brought about this situation could yet prove a great blessing.

Tesla made his decision. What inXuenced him to reach the determination that guided him, no one ever learned. He rejected Mr. Adams' oVer. From a practical point of view there is no way of explaining his action. But no one could ever successfully demonstrate that Tesla was practical in a commercial and Wnancial sense.

With the forty thousand dollars that Adams subscribed, Tesla was able to keep actively engaged in research for about three years. He probably could have secured subscriptions of many times that amount if he had been willing to put forth even a slight eVort in that direction, but he was interested mainly in getting his experiments well under way rather than worrying about future Wnancial needs. He had full faith that the future would bring him many millions of dollars as a token of the many billions of value he would give it through his inventions.

It took Tesla about a year to get his laboratory equipped and to build an array of experimental apparatus. Almost nothing that he used could be purchased in the market; everything had to be specially made by his workmen under his direction. In the spring of 1897 he was ready to make, on his wireless transmitter and receiver, the distance tests which had been interrupted by the Wre two years before.

The success of these tests were announced by Tesla in an interview with a representative of the Electrical Review which was published in the issue of July 9, 1897, of that journal. It stated:

Nearly every telegraphic inventor has for years dreamed in his waking hours of the possibility of communicating without wires. From time to time there has appeared in the technical journals a reference to the experiments showing the almost universal belief among electricians that, some day, wires will be done away with. Experiments have been made attempting to prove the possibilities, but it has remained for Mr. Nikola Tesla to advance a theory, and experimentally prove it, that wireless communication is a possibility and by no means a distant possibility. Indeed, after six years of careful and conscientious work, Mr. Tesla has arrived at a stage where some insight into the future is possible.

A representative of the Electrical Review receives the assurance personally from Mr. Tesla who, by the way, is nothing if not conservative, that electrical communication without wires is an accomplished fact and that the method employed and the principles involved have nothing in them to prevent messages being transmitted and intelligibly received between distant points. Already he has constructed both a transmitting apparatus and an electrical receiver which at distant points is sensitive to the signals of the transmitter, regardless of earth currents or points of the compass. And this has been done with a surprisingly small expenditure of energy.

Naturally, Mr. Tesla is averse to explaining all details of his invention, but allows it to be understood that he avails himself of what, for the present, may be termed the electrostatic equilibrium; that if this be disturbed at any point on the earth the disturbance can with proper apparatus be distinguished at a distant point and thus the means of signalling and reading signals becomes practicable once the concrete instruments are available. Mr. Tesla announced his belief in the possibilities, but he did so after having satisWed himself by actual test of apparatus designed by him. Much work has yet to be done, and he has since then given close attention and study to the problem.

Details are not yet available, for obvious reasons, and we now merely chronicle Mr. Tesla's statement that he has really accomplished wireless communication over reasonably long distances with small expenditure of energy and has only to perfect apparatus to go to any extent. Morse's 40 mile experiment in the old days was on a far less certain basis than the wireless possibilities of today.

Tesla's work with high frequency and high potential currents has been notable. As long ago as 1891 he foretold the present results, both as to vacuum tube lighting and intercommunication without wires. The former has in his hands assumed a condition capable of a public demonstration of the phenomena of the electrostatic molecular forces. Numberless experiments were carried out, and from what then was a startling frequency of 10,000 per second Mr. Tesla has advanced to what now is a moderate rate at 2,000,000 oscillations per second

This announcement recorded the birth of modern radio--radio as it is in use today--born on a boat traveling up the Hudson River, carrying the receiving set twenty-Wve miles from the Houston Street laboratory, a distance which was a small fraction of the range of the set but enough to demonstrate its capabilities. Such an accomplishment was worthy of a Xamboyant smash announcement instead of Tesla's very modest statement and the even more conservative manner in which the Electrical Review treated the news. Tesla had to protect not only his patent rights, which would be jeopardized by premature disclosure, but also had to be on guard against invention invaders and patent pirates, with whom he had previously had unpleasant experiences. The Electrical Review, naturally enough, was fearful of the consequences of ``sticking its neck out'' by too enthusiastic a reception before full details were available.

The fundamental patents on Tesla's system were issued on September 2, 1897, just two months after his announcement. They are numbered 645,576 and 649,621. In these patents he describes all the fundamental features of the radio broadcasting and receiving circuits in use today. Once patent protection was secured, Tesla did not long delay in letting the public in on his discoveries. His presentation took the form of a spectacular demonstration at Madison Square Garden.

Wireless transmission of intelligence is a modern satisfaction of one of the oldest cravings of man, who has always sought the annihilation of distance by communication through space without material linkage over the intervening expanse. Early experimenters with the telephone, particularly, were enthusiastic seekers of a method of wireless electrical communication that would convey the voice through space in the manner in which the air conducted sound. David Edward Hughes had noted, in 1879, that when an electric spark was produced anywhere in his house he heard a noise in his telephone receiver. He traced the eVect to the action of the carbon granules in contact with a metal disk in his telephone transmitter which acted as a detector of the space waves by sticking together slightly, reducing the resistance of the mass, and producing a click in the receiver.

Prof. A. E. Dolbear, of Tufts College, ampliWed this observation and set up, in 1882, a demonstration set using the principle but eliminating the telephone set. He used a spark coil for creating waves and a mass of carbon granules for detecting them. This is exactly the ``wireless'' system which Marconi ``discovered'' fourteen years later.

Edison, engaged by the Western Union Telegraph Company to break the monopoly which Bell held by his invention of the telephone, had succeeded, in 1885, in sending a message from a moving train by ``wireless.'' A wire strung on the train paralleling a telegraph wire strung on poles along the track made it possible to bridge the intervening few feet by an inductive eVect--the same eVect which causes annoyance by creating ``cross talk,'' or a mixing of conversations over two telephone circuits located close to each other. W. M. Preece, in England, made a similar experiment about the same time. The extremely short distances over which such systems worked prevented them from having any practical usefulness.

An entirely diVerent type of wireless communication had been developed by Alexander Graham Bell in 1880 and 1881. This was given the name radiophone, but Bell insisted on calling it the photophone. The photophone transmitted the voice over a beam of light. The transmitter consisted of a very thin glass or mica mirror, which could be vibrated by the voice. This reXected a beam of light, usually sunlight, to a distant receiving device. The simple receiver consisted of a chemist's test tube, into which a selected material was placed. The top of the tube was closed by a cork through which two small rubber tubes were inserted, the other ends being placed in the ears. A very great variety of materials could be placed in the test tube as detectors. When the beam of light, vibrated by the voice, impinged on the material in the tube, an absorption of heat took place which set the air in the tube in vibration, thus reproducing the voice that was carried by the light beam. Bell also used selenium as a detector. It responded to the visible rays and produced an electrical eVect. The experiments, obviously, were of little practical value as the basis for a system of wireless communication.

Michael Faraday, in London, had described in 1845 his theory of the relationship between light and the electromagnetic lines of force; and in 1862 James Clerk Maxwell published an analysis of Faraday's work which gave a mathematical basis for the theory that light waves were electromagnetic in nature, and that it was possible for such waves to exist very much shorter and very much longer than the known wavelength of visible light. This was a challenge to scientists to prove the existence of such waves.

Prof. Heinrich Hertz, at Bonn, Germany, from 1886 to 1888, undertook the search for the waves longer than light or heat. He produced them by the spark discharge of an induction coil and recaptured them from space, at short distances, in the form of a tiny spark that jumped the gap in a slotted ring of wire. Sir Oliver Lodge, in England, was simultaneously seeking to measure equally small electrical waves in wire circuits.

This, then, had been the situation in the scientiWc world when Tesla began his work in 1889. The plan for wireless communication which he presented in 1892 and 1893, as will be described in a moment, shows how his magniWcent concept and tremendously advanced knowledge towered mountain high over all contemporaries.

When Tesla left the Westinghouse plant in the fall of 1889, he had immediately turned to the next phase of his development of the alternating-current Weld--a new system of distributing energy by means of high-frequency alternating currents which would be a far more magniWcent discovery than his polyphase system. Within the next two years he had explored the principles by which energy could be distributed broadcast without the use of wires, and these he had demonstrated with powerful coils in his laboratory. The distribution of intelligence, later called ``wireless,'' was but a single phase of the larger project.

Tesla described, in 1892, the Wrst electronic tube designed for use as a detector in a radio system, and demonstrated its characteristics in his lectures in London and Paris in February and March of that year. (The tube, however, had been developed in 1890.) He described in February and March of the following year, 1893, his system of radio broadcasting, presenting its principles in detail, in lectures before the Franklin Institute in Philadelphia and at the convention of the National Electric Light Association held in St. Louis.

Tesla's electronic tube, his 1890 invention, was the ancestor of the detecting and amplifying tubes in use today. His demonstration of this tube is a matter of record in the archives of four societies before which he exhibited it in February and March of 1892--the Institute of Electrical Engineers and the Royal Society of London and the Physical Society of France and the International Society of Electrical Engineers in Paris. He stated in these lectures:

If there is any motion which is measurable going on in space, such a brush ought to reveal it. It is, so to speak, a beam of light, frictionless, devoid of inertia.

I think it may Wnd practical applications in telegraphy. With such a brush it would be possible to send dispatches across the Atlantic, for instance, with any speed, since its sensitiveness may be so great the slightest changes will aVect it.

The ``brush'' in Tesla's tube was a beam of electrons. The electron, however, had not yet been discovered. Nevertheless, Tesla gave an accurate description of its nature, demonstrating the remarkable accuracy of his interpretation of strange phenomena. So sensitive was this electronic beam that a small horseshoe magnet an inch wide at a distance of six feet caused movement of the electron beam in either direction, depending on the position in which the magnet was held.

If anyone approached the tube from a distance of many feet the beam, or brush, would swing to the opposite side of the tube. If one walked around the tube even at a distance of ten feet, the beam would move likewise, keeping its center end always pointed at the moving object. The slightest movement of a Wnger, or even the tensing of muscle, would bring a swinging response from the beam.

In the same 1892 lecture in which he described this Wrst electronic tube, Tesla demonstrated lamps which were lighted without wire connections (wireless light) and also a motor which operated without wire connections to the energizing coils (wireless power); and he had again presented these developments at his exhibition at the Chicago Columbian Exposition early in 1893.

It was with all this experience behind him, giving him full assurance that his system was entirely practical and operative, that Tesla presented at the Franklin Institute and at the convention of the National Electric Light Association in February and March, 1893, a very cautious and conservative statement concerning his plan. Even at these 1893 lectures, Tesla could have staged a demonstration of wireless transmission of intelligence by placing one of his resonant coils, surmounted by one of his electronic ``brush'' tubes, or one of his low-pressure air lamps, in the lecture hall and causing it to respond to signals sent out by an energized coil of similar wavelength but located at a considerable distance from the building. The experiment was a standard procedure in his laboratory.

This, however, would be a purely local eVect, whereas his radio transmission system was one planned on a world-wide basis requiring much more powerful apparatus than he had thus far built. To pass oV a purely local eVect as a demonstration of a world-wide system, even though the observed results would have been identical, would have been a case of intellectual dishonesty to which Tesla would not stoop; yet this demonstration of wireless would have been more spectacular and powerful than any staged by any other inventor in more than a half-dozen years following.

Describing his world-wide system at the 1893 National Electric Light Association meeting, he said:

In connection with resonance eVects and the problems of transmission of energy over a single conductor, which was previously considered, I would say a few words on a subject which constantly Wlls my thoughts, and which concerns the welfare of all. I mean the transmission of intelligible signals, or, perhaps, even power, to any distance without the use of wires. I am becoming more convinced of the practicability of the scheme; and though I know full well that the great majority of scientiWc men will not believe that such results can be practically and immediately realized, yet I think that all consider the developments in recent years by a number of workers to have been such as to encourage thought and experiment in this direction. My conviction has grown so strong that I no longer look upon the plan of energy or intelligence transmission as a mere theoretical possibility, but as a serious problem in electrical engineering, which must be carried out some day.

The idea of transmitting intelligence without wires is the natural outcome of the most recent results of electrical investigations. Some enthusiasts have expressed their belief that telephony to any distance by induction through air is possible. I cannot stretch my imagination so far, but I do Wrmly believe that it is practical to disturb, by means of powerful machines, the electrostatic conditions of the earth, and thus transmit intelligible signals, and, perhaps, power. In fact, what is there against carrying out such a scheme?

We now know that electrical vibrations may be transmitted through a single conductor. Why then not try to avail ourselves of the earth for this purpose? We need not be frightened by the idea of distance. To the weary wanderer counting the mileposts, the earth may appear very large; but to the happiest of all men, the astronomer, who gazes at the heavens, and by their standards judges the magnitude of our globe, it appears very small. And so I think it must seem to the electrician; for when he considers the speed with which an electrical disturbance is propagated through the earth, all his ideas of distance must completely vanish.

A point of great importance would be Wrst to know what is the capacity of the earth, and what charge does it contain if electriWed. Though we have no positive evidence of a charged body existing in space without other oppositely electriWed bodies being near, there is a fair probability that the earth is such a body, for by whatever process it was separated--and this is the accepted view of its origin--it must have retained a charge, as occurs in all processes of mechanical separation. . . .

If we can ever ascertain at what period the earth's charge, when disturbed, oscillates, with respect to an oppositely charged system or known circuit, we shall know a fact possibly of the greatest importance to the welfare of the human race. I propose to seek for the period by means of an electrical oscillator or a source of alternating currents.

One of the terminals of this source would be connected to the earth, as, for instance, to the city water mains, the other to an insulated body of large surface. It is possible that the outer conducting air strata or free space contains an opposite charge, and that, together with the earth, they form a condenser of large capacity. In such case the period of vibration may be very low and an alternating dynamo machine might serve for the purpose of the experiment. I would then transform the current to a potential as high as it would be found possible, and connect the ends of the high tension secondary to the ground and to the insulated body. By varying the frequency of the currents and carefully observing the potential of the insulated body, and watching for the disturbance at various neighboring points of the earth's surface, resonance might be detected.

Should, as the majority of scientiWc men in all probability believe, the period be extremely small, then a dynamo machine would not do, and a proper electrical oscillator would have to be produced, and perhaps it might not be possible to obtain such rapid vibrations. But whether this be possible or not, and whether the earth contains a charge or not, and whatever may be its period of vibration, it is certainly possible--for of this we have daily evidence--to produce some electrical disturbance suYciently powerful to be perceptible by suitable instruments at any point on the earth's surface. . . .

Theoretically, then, it could not require a great amount of energy to produce a disturbance perceptible at a great distance, or even all over the surface of the globe. Now, it is quite certain that at any point within a certain radius of the sources, a properly adjusted self induction and capacity device can be set in action by resonance. But not only this can be done, but another source, s 1, similar to s, or any number of such sources, can be set to work in synchronism with the latter, and the vibration thus intensiWed and spread over a large area, or a Xow of electricity produced to or from source s 1, if the same or of opposite phase to the source s.

I think that, beyond doubt, it is possible to operate electrical devices in a city, through the ground or pipe system, by resonance from an electrical oscillator located at a central point. But the practical solution of this problem would be of incomparably smaller beneWt to man than the realization of the scheme of transmitting intelligence, or, perhaps, power, to any distance through the earth or environing medium. If this is at all possible, distance does not mean anything. Proper apparatus must Wrst be produced, by means of which the problem can be attacked, and I have devoted much thought to this subject. I am Wrmly convinced it can be done, and I hope we shall live to see it done.

The lecture before the Franklin Institute contained a similar statement. An additional paragraph from it can be quoted:

If by means of powerful machinery, rapid variations of the earth's potential were produced, a grounded wire reaching up to some height would be traversed by a current which could be increased by connecting the free end of the wire to a body of some size. . . . The experiment, which would be of great scientiWc interest, would probably best succeed on a ship at sea. In this manner, even if it were not possible to operate machinery, intelligence might be transmitted quite certainly.

Tesla thus presented in these lectures the principles which he had learned in his laboratory experiments, during the previous three years, were necessary for successful wireless communication.

Several fundamental requirements were presented which will be understood by any non-technical person who has had even slight experience with radio receiving sets: 1. An antenna, or ærial wire; 2. A ground connection; 3. An ærial-ground circuit containing inductance and capacity; 4. Adjustable inductance and capacity (for tuning); 5. Sending and receiving sets tuned to resonance with each other; and 6. Electronic tube detectors. He had still earlier invented a loud speaker.

These embody the fundamental principles of radio, and are used in every sending and receiving set today.

Radio as it exists today is, therefore, the product of the genius of Nikola Tesla. He is the original inventor of the system as a whole and of all the principal electrical components. The man who, next to Tesla, is entitled to the greatest amount of credit is Sir Oliver Lodge, the great English scientist. Even Lodge, however, failed to grasp the fundamental picture that Tesla presented.

Lodge, early in 1894, had put a Hertz spark gap in a copper cylinder open at one end; and in this way he produced a beam of ultra-short-wave oscillations which could be transmitted in any direction. He did the same for the receiving set. Since the incoming waves could be received from only one direction, this receiving set was able to locate the direction from which the transmitted waves came. With this set he completely anticipated Marconi by two years. In the summer of that year, in a demonstration before the British Association for the Advancement of Science at Oxford, he sent Morse signals, with an improved set, between two buildings separated by several hundred feet.

It is little wonder, then, that Marconi, who started his studies of wireless in 1895, created no stir in the scientiWc circles in England when he came from Italy to London in 1896 with a wireless set that in every essential feature was the same as that demonstrated by Lodge in 1894. He used a parabolic reXector, so his set was little more than an electrical searchlight. He did, however, bring an alternative feature to replace the parabolic beam reXector. This was a ground connection and antenna, or ærial wire, for both sending and receiving set. This was exactly what Tesla had described in his plan published three years before.

When Hertz made his experiments to demonstrate the identical nature of light and longer electromagnetic waves, he intentionally sought to use the shortest waves it was practicable to produce. They were measured in inches--much less than a yard long. They were entirely satisfactory for his experiment. When the wireless experimenters copied his methods they took over the short-wave plan without ever asking a question as to what wavelength should be used for wireless communication; the thought seems not to have dawned on them that there were other wavelengths that could be produced and used--all except Tesla.

Tesla took the trouble, with the spirit of a real scientist to repeat exactly the experiments of Hertz; and he published his results, stating that he found a number of important diVerences and calling attention to the inadequacies of Hertz's experimental methods.

Having experimented with a wide gamut of wavelengths of high-frequency currents and studied the properties of each section of the spectrum, he knew that the short wavelengths were totally unsuitable for communication purposes. He knew that the useful wavelengths ranged from 100 meters to many thousands of meters. He knew that the combination of induction coil and Hertz ball-type spark-gap oscillator could never have any practical usefulness in producing the kind of electrical pulsations required. Even with the highly eYcient apparatus available today, scientists have been unable to use in communication (except for special purposes) the ultra-short waves which Tesla in his wisdom condemned and Marconi, owing to his inexperience, tried to use.

The history of the succeeding years in wireless is the story of the failure of the short waves of Lodge and Marconi and their followers, and the shifting over to the longer waves described by Tesla; and the dropping of their crash method of signaling and its replacement by the reWned and highly eYcient method of tuning to each other the sending and receiving stations by the methods discovered by Tesla; and adoption of Tesla's continuous waves.

In addition, these groping workers saw in wireless only a point-to-point or station-to-station method of signaling. None of them foresaw the broadcasting system which Tesla described in 1893. The system invented and discovered by Tesla is the one in use today; but who ever heard anyone giving Tesla the slightest credit?

NINE

TESLA was proliWc in opening up vast new empires of knowledge. He showered his discoveries on the world at such a rapid rate and in such a nonchalant manner that he seems to have benumbed the minds of the scientists of his age. He was too busy to spend time developing the technical or commercial applications of each new discovery--there were too many other new and important revelations within his vision that must be brought to light. Discoveries were not happenstance events to him. He visualized them far in advance of their unfolding in the laboratory. He had a deWnite program of pioneering research in virgin Welds of investigation; and when this was accomplished he would, he felt, have a long lifetime still ahead of him in which he could return to the practical utilization of those already revealed.

Meanwhile, he had found a whole new world of interesting eVects in the discharges produced by his coils when energized with the currents of extremely high frequency. He built larger and larger coils and experimented with a variety of shapes as constructions. From the common cylindrical type of coil he developed the cone-shaped coil, and this development he carried still further by designing the Xat helix, or pancake-shaped coil.

The extremely high-frequency currents furnished a mathematical paradise in which Tesla could develop his equations to his heart's content. Through his mathematical abilities and his strange power of visualization he could frequently make, very quickly, whole series of discoveries that it took a long time to catch up with in actual laboratory constructions. This was true of the phenomena of resonance, or tuned circuits.

Because of their relatively short wavelength, it was comparatively easy to build condensers for tuning the circuits. When a circuit is tuned the electric current that Xows in it oscillates rhythmically, just as does a musical string which, when struck or plucked, vibrates and builds up loops of even lengths with motionless points between them. There may be only one of these loops, or there can be many.

Tesla did not invent the idea of electrical resonance. It was inherent in the mathematical description of the condenser discharge as developed by Lord Kelvin, and in the physical nature of alternating currents; but Tesla changed it from a buried mathematical equation to sparking physical reality. It is the analogy of acoustical resonance which is a natural property of matter. However, there were no practical circuits in which resonance could manifest itself until Tesla developed alternating currents, particularly the high-frequency currents. He put the master's touch to the research in this Weld by developing the principle of resonance in individual circuits through adjustment of capacity and inductance; the ampliWcation of eVects by inductive coupling of two tuned circuits, and the peculiar manifestations of resonance in a circuit tuned to a quarter of the wavelength of the energizing current. This latter development was a stroke of pure genius.

In the vibrating string, two loops measure a complete wavelength and one loop measures half a wavelength, since one of the loops is up when the other is down. Between the two loops is a nodal point which does not move. From the nodal point to the top of a loop is a quarter wavelength. Taking the quarter wavelength as a unit, one end is motionless and the other end swings through the greatest amplitude of vibration.

By tuning his coils to quarter wavelengths, one end of the coil, Tesla found, would be entirely inactive while the other end would swing through tremendous electrical activity. Here was a unique situation, one end of a small coil inert and the other end spouting a Xood of sparks of hundreds of thousands or even millions of volts. In a physical analogy it seemed like the Niagara River reaching the edge of the precipice--and then its waters shooting mountain high in a gigantic fountain instead of falling into the chasm.

The quarter-wavelength coil is the electrical counterpart of the vibrating tine of the tuning fork, the ordinary clock pendulum, or the vibrating reed. Once accomplished, it was a simple thing--but its discovery was a work of genius. It was a development that could have come with certainty to a master mind working on broad principles, as Tesla was doing all his life, and only by the most improbable chance to those who without illumination were tinkering with gadgets and hoping to stumble on something out of which they could make a fortune.

A high-voltage coil with one dead end greatly simpliWed many problems. One of Tesla's big problems had been the Wnding of means to insulate the high-voltage secondary coil of transformers from the low-voltage primary which energized it. Tesla's discovery eliminated the voltage entirely from one end of the secondary so it could be connected directly to the primary or to the ground, while the other end continued to spout its lightning. It was for utilizing this situation that he developed the conical and pancake-shaped coils.

Tesla's laboratory was Wlled with a variety of coils. He discovered early in his researches that while operating a coil of a given wavelength, other coils in the laboratory, tuned either to this wavelength or one of its harmonics, would respond sympathetically by spouting a crown of sparks although not connected in any way to the operating coil.

Here was an example of transmission of energy to a distance through space. It was not necessary for Tesla to make a series of experiments to understand the implications of this situation. He was never lost in a new territory which he opened. His mind rose to such heights of understanding that he could survey a revealed world in a glance.

Tesla planned a spectacular demonstration of the new principle. He had his workmen string a wire on insulating supports on all four walls near the ceiling of the largest room in his laboratory. The wire was connected to one of his oscillators.

It was late at night when the installation was ready for the experiment. In order to make the test, Tesla prepared two tubes of glass about three feet long and a half-inch in diameter. He sealed one end of each, slightly evacuated the air from the tubes and then sealed the other ends.

Tesla told the workmen he wanted the room completely darkened for the test, all lights out; and when he gave the signal he wanted the switch of his oscillator closed. ``If my theory is correct,'' he explained, ``when you close the switch these tubes will become swords of Wre.''

Walking to the middle of the room Tesla gave orders to turn out all lights. The laboratory was in pitch darkness. A workman stood with his hand on the switch of the oscillator.

``Now!'' shouted Tesla.

Instantly the great room was Xooded with brilliant but weird blue-white light and the workmen beheld the tall, slim Wgure of Tesla in the middle of the room waving vigorously what looked like two Xaming swords. The two glass tubes glowed with an unearthly radiance, and he would parry and thrust with them as if he were in a double fencing match.

To the workmen in the laboratory, it was a common experience for Tesla to perform spectacular feats; but this went beyond all limits. He had previously lighted his electric vacuum lamps but they were always connected to coils that supplied them with electricity. Now they lighted without being connected to any source of electricity.

This demonstration, made in 1890, led to Tesla's adopting the technique as the permanent method of lighting his laboratories. The loop around the ceiling was always energized; and if anyone wished a light at any position, it was only necessary to take a glass tube and place it in any convenient location.

When tesla undertook the development of a new kind of electric light, he went to the sun for his model. He saw in the photo- sphere, or outer gaseous layer of the sun, light being created by the vibration of molecules. That was the theory then prevalent; and he sought to use the same method.

In the tremendous burst of revelation which he received in the park at Budapest as he gazed into the Xaming orb of the setting sun, there had Xashed into his mind, as we have seen, not only the marvelous invention of the rotary magnetic Weld and the many uses of multiple alternating currents, but also the grand generalization that everything in Nature operated on the principle of vibrations that corresponded to alternating currents. The host of inventions and discoveries which he made in all succeeding years had their roots, too, in that sublime experience.

In the sun, it was believed, light was created when the molecules were vibrated by heat. Tesla sought to improve on this method by vibrating the molecules by electrical forces. The sparks and electrical Xames created by his high-voltage coils were associated, he believed, with molecular vibrations in the air. If he could bottle the gases of the air and set them in vibration electrically, they should produce light without heat, since the energy was supplied by cold electric currents.

Sir William Crookes, who, long before Edison, produced an incandescent electric light by sealing an electrically heated wire in a vacuum tube, had carried out an extended series of experiments in conducting electricity through the gases in glass vessels under a variety of conditions ranging from atmospheric pressure to the highest vacuum obtainable, and had produced some strange eVects. Crookes used the high-voltage current produced by the old-fashioned induction coil.

Tesla expected that when he bottled the strange eVects he had observed with his currents of extremely high frequency, he would produce manifestations radically diVerent from those found by Crookes, or Geissler, who also worked in this Weld. In this he was not disappointed.

Four types of an entirely new kind of electric light were produced by Tesla, using electrically activated molecules of gas: 1. Tubes in which a solid body was rendered incandescent; 2. Tubes in which phosphorescent and Xuorescent materials were caused to luminesce; 3. Tubes in which rareWed gases became luminous, and 4. Tubes in which luminosity was produced in gases at ordinary pressures.

Like Crookes, Tesla passed his high-frequency currents through gases at all pressures, from lowest-pressure vacuum to normal atmospheric pressure, and obtained brilliant luminous eVects exceeding anything previously attained. He substituted for air in his tubes other gases, including mercury vapor, and observed the peculiar color and other eVects they yielded.

Noting the variety of colors the various gases, and even air, showed under diVerent pressures, Tesla suspected that not all of the energy radiated was given oV as visible light, but that some of it emanated as black light. Testing this hypothesis, he placed sulphide of zinc and other phosphorescent and Xuorescent materials in his tubes and caused them to glow. In these experiments (they were made in 1889) Tesla laid the foundation for our most recently developed type of highly eYcient lamps used in Xuorescent lighting which are generally believed to have been invented in recent years. This system of utilizing the wasted ultra-violet or invisible black light by changing it to visible light by means of phosphorescent substances is Tesla's invention. Roentgen was using similar tubes, but of plain glass and the Xuorescent substance on a table in his laboratory when, a half-dozen years later, he discovered X-rays. Tesla invented, also, the neon-tube type of lamp, and even bent his tubes to form letters and geometrical shapes, as is done in neon-tube signs. This is true in spite of some antecedent and concurrent laboratory experiments by Crookes and J. J. Thompson, neither of whom developed any lamps or practical applications.

Tesla had discovered early in 1890 that his high-frequency currents had properties so diVerent from the ordinary induction-coil, or spark-coil, currents, that he was able to light his tubes just as well, and sometimes even better, with only one wire connecting them with the high-tension transformer, the return circuit being eVected wirelessly through space.

In working with types of lamps consisting of tubes in the center of which there was a conducting wire, and with the tube Wlled with air under a partial vacuum, Tesla discovered that the gas would serve as a better conductor of the high-frequency current than the wire. From this observation he was able to develop many spectacular experiments which appeared to violate the most fundamental laws of electricity. He was able to short circuit lamps and other apparatus with heavy bars of metal which, with ordinary currents, would completely deprive the devices of electricity so they would be unable to operate. However, with his high-frequency currents, the lamps would light and the devices operate just as if the short-circuiting bar were not present.

One of his startling experiments consisted of placing a long glass tube partially evacuated of its air inside a slightly longer copper tube with a closed end. A slit was cut in the copper tube in its central section so the tube inside would be seen. When the copper tube was connected in the high-frequency circuit, the air in the tube was brilliantly illuminated; but no evidence could be found of any current Xowing through the short-circuiting copper shell. The electricity preferred to pass through the glass tube, by induction, to the enclosed partially evacuated air, pass through the low-pressure air for the full length of the tube, and then pass out the other end by induction, rather than traverse the complete metal path in the surrounding metal tube.

We have then, [said Tesla], as far as we can now see, in the gas a conductor which is capable of transmitting electric impulses of any frequency which we may be able to produce. Could the frequency be brought high enough, then a queer system of distribution, which would be likely to interest gas companies, might be realized; metal pipes Wlled with gas--the metal being the insulator and the gas the conductor--supplying phosphorescent bulbs, or perhaps devices not yet invented.

This remarkable conductivity of gases, including the air, at low pressures, later led Tesla to suggest, in a published statement in 1914, a system of lighting on a terrestrial scale in which he proposed to treat the whole earth, with its surrounding atmosphere, as if it were a single lamp.

The atmosphere is under the greatest pressure at the surface of the earth, owing to the weight of the overlying air. As we go higher in the air there are increasing amounts below us and less above, so, the greater the elevation, the lower is the pressure of the air.

At higher altitudes the gases in the atmosphere are in the same condition as the air in the partially evacuated tubes he prepared in his laboratory, Tesla explained, and therefore it would serve as an excellent conductor of high-frequency currents. The aurora borealis is a natural example of the eVect Tesla sought, and it is produced by Nature as Tesla planned; but this was not known when he evolved his idea.

The Xow of a suYcient amount of the electricity in the right form through the upper regions of the atmosphere would cause the air to become luminous. The whole earth would be transformed into a giant lamp, with the night sky completely illuminated. It would be unnecessary, he pointed out, to use any lamps along streets, roads or other outdoor areas, except during periods in which storms or low clouds prevailed. Ocean travel would be made safer and more pleasant, for the sky over the whole ocean would be illuminated, making the night as bright as day.

The methods by which Tesla intended to conduct his high-frequency currents to the upper air have not been published. When he outlined the project, he stated that the plan did not present any diYculties that could not be handled in a practical way. This meant that he had deWnite means for accomplishing his purpose.

The air, he stated, possesses a high degree of conductivity for high-frequency currents at an altitude of 35,000 feet, but could be used eVectively at lower altitudes. The accuracy of Tesla's prediction with respect to the conductivity of the upper air is attested by one of the problems encountered today in the operation of airplanes at altitudes even lower than 25,000 feet. The ignition system, carrying high-voltage currents to the spark plugs in the airplane engines, which explodes the gas in the cylinders, has been giving trouble at the higher altitudes because the electricity escapes with a great deal of freedom into the surrounding air. At lower altitudes the air is an excellent insulator, especially for direct current and low-frequency currents, but, as Tesla discovered, at the higher altitudes where low pressures prevail it becomes an excellent conductor for the high-frequency currents. The wires leading to spark plugs become surrounded by a corona, or electrical halo, which indicates the escape of the current. This interferes with the eYciency, if it does not entirely prevent the operation, of devices employing high-frequency or high-potential currents, such as radio apparatus. (Since Tesla discovered that metal wires and rods which act as excellent conductors for direct and low-frequency currents can act as excellent insulators for his high-frequency currents, it is obvious that the common suggestion made for delivering a current to the upper air by means of metal cables suspended from balloons is entirely impractical.)

This proposal by Tesla to transform the earth into a giant lamp was again referred to by him in the twenties. At this time he was without funds for carrying on experimental work, and, as he never announced details until after he had tested them in practice, he withheld a disclosure of his methods. He was hopeful, however, that he would soon secure money enough to permit him to test his plan.

The author bombarded Tesla with questions in an eVort to learn the general plan he had in mind. Tesla was adamant.

``If I should answer three more of your questions you would know as much about my plan as I do,'' he replied.

``Nevertheless, Dr. Tesla,'' I replied, ``I am going to outline in my article the only plan that appears to me to be feasible under our known physical laws, and you can deny or aYrm it. Your molecular bombardment tubes are proliWc producers of ultra-violet and X-rays and could produce a powerful beam of this radiation which would ionize the air through great distances. When these rays pass through the air they ionize it, making it a good conductor of electricity of all kinds at suYciently high voltages. By producing such a beam on a high mountain and directing it upward this would provide a conducting path through the air to any height desired. You could then send your high-frequency currents to the upper air without leaving the ground.''

``If you publish that,'' said Tesla, ``it must appear as your plan, not mine.''

The article was published with the foregoing speculation in it; but neither aYrmation nor denial was forthcoming from the inventor, and nothing more can be said in its favor. Tesla may have had a simpler and more practical plan in mind. (Since completing this volume the author has learned that Tesla planned to install a bank of powerful ultra-violet lamps on top of his tower at WardencliV (cf. p. 207), and had the upper Platform designed to receive them.)

There was one other plan which Tesla discussed on a number of occasions when considering terrestrial electrical conditions, and which he may have had in mind in this connection. He pointed out that the earth is a good conductor of electricity and the upper air is also a good conductor, while the intervening lower stratum of air is an insulator for many kinds of current. This combination provides what is known as a condenser, a device which will store and discharge electricity. By charging the earth, the upper air would become charged by induction. When our spinning earth was so transformed into a terrestrial Leyden jar, it could be alternately charged and discharged, so that a current would Xow both in the upper air and in the ground, producing the electrical Xow which would cause the upper air to become self-luminous. Tesla, however, never became quite so speciWc in applying the condenser plan to this problem as the preceding sentence indicates. His plan may still exist in his papers, which, at the present writing, are sealed against inspection except by Government oYcials.

Out of the almost empty space in a six-inch vacuum tube Tesla

succeeded in extracting at least Wve epoch-making discoveries. Tesla's lamp was more proliWc in producing wonders than the Aladdin's lamp of the Arabian Nights. He gave his ``magic'' lamp to science Wfty years ago. This magic talisman was Tesla's carbon-button lamp which, apart from the other discoveries that came of it, was in itself, just as a lamp, a brilliant scientific discovery--and still remains unused. Edison developed the practical incandescent Wlament electric lamp and was entitled to, and receives, a tremendous amount of credit for his accomplishment. Tesla invented an absolutely original type of lamp, the incandescent-button lamp, which gives twenty times as much light for the same amount of current consumed; and his contribution remains practically unknown.

The carbon-button type of lamp was described by Tesla in his lecture before the American Institute of Engineers in New York in May, 1891, and further developments were presented in the lectures which he gave in England and France in February and March, 1892. In his New York lecture he said:

Electrostatic eVects are in many ways available for the production of light. For instance, we may place a body of some refractory material in a closed, and preferably in a more or less air exhausted, globe, connect it to a source of high, rapidly alternating potential, causing the molecules of the gas to strike it many times a second at enormous speeds, and in this way, with trillions of invisible hammers, pound it until it gets incandescent. Or we may place a body in a very highly exhausted globe, and by employing very high frequencies and potentials maintain it at any desired degree of incandescence.

He made a vast number of experiments with this carbon-button lamp and gave a description of the most signiWcant ones in his lecture before the English and French scientiWc societies in the spring of 1892. It was, however, only one of the many new types of lamps and other important developments which he included in this spectacular presentation of his work.

The carbon-button lamps were of very simple construction. Basically they consisted of a spherical glass globe three to six inches in diameter, in the center of which was a piece of solid refractory material mounted on the end of a wire which protruded through the globe and served as a single-wire connection with the source of high-frequency currents. The globe contained rareWed air.

When the high-frequency current was connected with the lamp, molecules of the air in the globe, coming in contact with the central button, became charged and were repelled at high velocity to the glass globe where they lost their charge and were then repelled back at equally high velocity, striking the button. Millions of millions of such processes each second caused the button to become heated to incandescence.

In these simple glass globes Tesla was able to produce extremely high temperatures, the upper limit of which seemed to be determined by the amount of current used. He was able to vaporize carbon directly into a gas, observing that the liquid state was so unstable it could not exist. Zirconia, the most heat-resistant substance known, could be melted instantly. He tried diamonds and rubies as buttons--and they too were vaporized. When using the device as a lamp it was not his desire to melt the substances; but he always carried experiments to their upper and lower limits. Carborundum, he observed, was so refractory that it was possible when using buttons made of this material (calcium carbide) to run the lamps at higher current densities than was possible with other substances. Carborundum did not vaporize so readily, nor did it make deposits on the inside of the globe.

Tesla thus evolved a technique in operating the lamps whereby the incandescent button transferred its heat energy to the molecules of the very small amount of gas in the tube so that they became a source of light, thus causing the lamps to function like the sun, the button being the massive body of the sun and the surrounding gas like the photosphere, or atmospheric light-emitting layer, of that body.

Tesla had a keen sense of dramatic values, but quite apart from this he undoubtedly enjoyed a unique satisfaction when he was able to light this miniature sun in the currents that he passed through his body--high-frequency currents of hundreds of thousands of volts. With one hand grasping a terminal of his high-frequency transformer and the other holding aloft this bulb containing an incandescent miniature sun which he had created--posing like the Statue of Liberty--he was able to make his new lamp radiate its brilliant illumination. Here, you might say, was the superman manifesting his ultramundane accomplishments. In addition, there was a satisfaction which was associated purely with the plane of ordinary mortals. Edison had laughed at his plan for developing the alternating-current system, and had declared that these currents were not only useless but deadly. Surely, this was an adequate answer; Tesla would let Nature make his replies.

Observing this working model of the incandescent sun which he could hold in his hand, Tesla was quick to see many of the implications of its phenomena. Every electrical wave that surged through the tiny central bead caused a shower of particles to radiate from it at tremendous velocity and strike the surrounding glass globe, only to be reXected back to the bead. The sun, Tesla reasoned, is an incandescent body that carries a high electrical charge and it, too, will emit vast showers of tiny particles, each carrying great energy because of its extremely high velocity. In the case of the sun, and other stars like it, there was no glass globe to act as a barrier, so the showers of particles continued out into the vast realms of surrounding space.

All space was Wlled with these particles and they were continually bombarding the earth, blasting matter wherever they struck, just as they did in his globes. He had seen this process take place in his globes, where the most refractory carbon beads could be shattered into atomic dust by the bombardment of the electriWed particles.

He sought to detect these particles striking the earth: one of the manifestations of this bombardment, he declared, was the aurora borealis. The records of the experimental methods by which he detected these rays are not available; but he published an announcement that he had detected them, measured their energy, and found that they moved with tremendously high velocities imparted to them by the hundreds of millions of volts potential of the sun.

Neither the scientists nor the general public in the early nineties were in a mood for such fantastic Wgures, or for any claim that the earth was bombarded by such destructive rays. It would be describing the situation in very conservative fashion to state that Tesla's report was not taken seriously.

When, however, the French physicist, Henri Becquerel, in 1896, discovered the mysterious rays emitted by uranium, and subsequent investigations, culminating with the discovery by Pierre and Marie Curie, in Paris, of radium, whose atoms were exploding spontaneously without apparent cause, Tesla was able to point to his cosmic rays as the simple cause of the radioactivity of radium, thorium, uranium and other substances. And he predicted that other substances would also be found to be made radioactive by bombardment with these rays. The victory for Tesla, however, was only temporary, for the scientiWc world did not accept his theory. Nevertheless, Tesla was a better prophet than he knew, or anyone else suspected.

Thirty years later Dr. Robert A. Millikan rediscovered these rays, believing them to be vibratory in character like light, and was followed by Dr. Arthur H. Compton, who proved the existence of cosmic rays consisting of high-velocity particles of matter, just as Tesla described them. They started by Wnding energies of ten million volts; and today the energies are far up in the billions and even trillions of electron volts. And these and other investigators describe these rays as shattering atoms of matter producing showers of débris--just as Tesla predicted.

In 1934, Frederick Joliot, son-in-law of the Curies, discovered that artiWcial radioactivity was produced in ordinary materials by bombarding them with particles in just the manner which Tesla described. Joliot received the Nobel Prize for his discovery; no one gives any credit to Tesla.

Tesla's molecular-bombardment lamp was the ancestor of another very modern development--the atom-smashing cyclotron. The cyclotron, developed by E. O. Lawrence, of the University of California, during the past twenty years, is a device in which electriWed particles are whirled in a magnetic Weld in a circular chamber until they reach a very high velocity, and are then led out of the chamber in a narrow stream. The giant machine, with a magnet as high as a house, partially completed at present writing, will emit so powerful a beam of charged particles that, according to Prof. Lawrence, if allowed to impinge on a building brick they will totally disintegrate it. The smaller models were used to bombard a variety of substances to render them radioactive, to disintegrate them or transmute their atoms into those of other elements.

The small glass globe, six inches or less in diameter, holding Tesla's molecular-bombardment lamp produced exactly this same disintegrating eVect on solid matter, probably with a more intensiWed eVect than any atom-smashing cyclotron now in existence despite their tremendous size. (Even small ones weigh twenty tons.)

In describing one of the experiments with his lamp, one in which a ruby was mounted in a carbon button, Tesla said:

It was found, among other things, that in such cases, no matter where the bombardment began, just as soon as a high temperature was reached there was generally one of the bodies which seemed to take most of the bombardment upon itself, the other, or others, being thereby relieved. This quality appeared to depend principally on the point of fusion, and on the facility with which the body was ``evaporated,'' or, generally speaking, disintegrated--meaning by the latter term not only the throwing oV of atoms, but likewise of larger lumps. The observation made was in accordance with generally accepted notions. In a highly exhausted bulb electricity is carried oV from the electrode by independent carriers, which are partly atoms, or molecules, of the residual atmosphere, and partly the atoms, molecules, or lumps thrown oV from the electrode. If the electrode is composed of bodies of diVerent character, and if one of these is more easily disintegrated than the others, most of the electricity supplied is carried oV from that body, which is then brought to a higher temperature than the others, and this the more, as upon an increase of the temperature the body is still more easily disintegrated.

Substances which resisted melting in temperatures attainable in laboratory furnaces of that day were easily disintegrated in Tesla's simple-lamp disintegrator, which provided a powerful beam of disintegrating particles by having them concentrated from all directions by a spherical reXector (the globe of his lamp), a kind a three-dimension burning glass, but operating with electriWed particles instead of heat rays. It accomplished the same eVect as the heavy atom disintegrators of today, but much more eYciently in a globe so light in weight it almost Xoated oV in air. Its simplicity and eYciency is further increased by the fact that it causes the substance that is being disintegrated to supply the particles by which the disintegration is eVected.

There is one more very modern discovery of great importance embodied in Tesla's molecular-bombardment lamp--the point electron miscroscope, which provides magniWcations of a million diameters, or ten to twenty times more powerful than the better known electron microscope which in turn is capable of magniWcations up to Wfty times greater than the optical microscope.

In the point electron microscope, electriWed particles shoot out in straight lines from a tiny active spot on a piece of substance kept at a high potential, and reproduce on the spherical surface of a glass globe the pattern of the microscopically small area from which the particles are issuing. The size of the glass sphere furnishes the only limit to the degree of magniWcation that can be obtained; the greater the radius, the greater the magniWcation. Since electrons are smaller than light waves, objects too small to be seen by light waves can be tremendously enlarged by the patterns produced by the emitted electrons.

Tesla produced on the surface of the spherical globe of his lamp phosphorescent images of what was taking place on the disintegrating button when he used extremely high vacuum. He described this eVect in his lectures in the spring of 1892, and his description will stand with hardly a change in a word for a description of the million-magniWcation point electron microscope. Quoting from his lecture:

To the eye the electrode appears uniformly brilliant, but there are upon it points constantly shifting and wandering about, of a temperature far above the mean, and this materially hastens the process of deterioration. . . . Exhaust a bulb to a very high degree, so that with a fairly high potential the discharge cannot pass--that is, not a luminous one, for a weak invisible discharge occurs always, in all probability. Now raise slowly and carefully the potential, leaving the primary current no more than for an instant. At a certain point, two, three or half a dozen phosphorescent spots will appear on the globe. These places of the glass are evidently more violently bombarded than the others, this being due to the unevenly distributed electric density, necessitated, of course, by sharp projections, or, generally speaking, irregularities of the electrode. But the luminous patches are constantly changing in position, which is especially well observed if one manages to produce very few, and this indicates that the conWguration of the electrode is rapidly changing.

It would be an act of simple justice if in the future scientists would extend credit to Tesla for being the one who discovered the electron microscope. There is no reduction in the glory due him because he did not speciWcally describe the electron, then unknown, in its operations, but assumed the eVect was due to electrically charged atoms.

When Tesla studied the performance of various models of this and his other gaseous lamps, he observed that the output of visible light changed under various operating conditions. He knew they gave oV both visible and invisible rays. He used a variety of phosphorescent and Xuorescent substances for detecting the ultra-violet or black light. Usually, the changes in the visible and ultra-violet light about balanced each other; as one increased the other decreased, with the remainder of the energy accounted for by heat losses. In his molecular-bombardment lamp he found, he reported in his 1892 lectures, ``visible black light and a very special radiation.'' He was experimenting with this radiation which, he reported, produced shadowgraph pictures on plates in metal containers, in his laboratory when it was destroyed by Wre in March, 1895.

This ``very special radiation'' was not further described at that time in published articles; but when Prof. Wilhelm Konrad Roentgen, in Germany, in December, 1895, announced the discovery of X-rays, Tesla was able immediately to reproduce the same results by means of his ``very special radiation,'' indicating that these and X-rays had very similar properties although produced in somewhat diVerent ways. Immediately upon reading Roentgen's announcement, Tesla forwarded to the German scientist shadowgraph pictures produced by his ``very special radiation.'' Roentgen replied: ``The pictures are very interesting. If you would only be so kind as to disclose the manner in which you obtained them.''

Tesla did not consider that this situation gave him any priority in the discovery of X-rays, nor did he ever advance any claims; but he immediately started an extensive series of investigations into their nature. While others were trying to coax out of the type of tube used by Roentgen enough X-rays to take shadow photographs through such thin structures as the hands and feet held very close to the bulb, Tesla was taking photographs through the skull at a distance of forty feet from the tube. He elsewhere described at this time an unidentiWed type of radiation coming from a spark gap, when a heavy current was passed, that was not a transverse wave like light, or Hertzian waves, and could not be stopped by interposing metal plates.

Tesla, thus, in one lecture reporting his investigations covering a period of two years, oVered to the world--in addition to his new electric vacuum lamps, his highly eYcient incandescent lamp, and his high-frequency and high-potential currents and apparatus--at least Wve outstanding scientiWc discoveries: 1. Cosmic rays; 2. ArtiWcial radioactivity; 3. Disintegrating beam of electriWed particles, or atom smasher; 4. Electron microscope; and 5. ``Very special radiation'' (X-rays).

At least four of these innovations, when ``rediscovered'' up to forty years later, won Nobel Prizes for others; and Tesla's name is never mentioned in connection with them.

Yet Tesla's lifetime work was hardly well started!

TEN

TESLA had a remarkable ability for carrying on simultaneously a number of widely diVerent lines of scientiWc research. While pursuing his studies of high-frequency electrical oscillations with all of their ramiWcations from vacuum lamps to radio, he was also investigating mechanical vibrations; and he had a rare foresight into the many useful applications to which they could be put, and which have since been realized.

Tesla never did things by halves. Almost everything he attempted went oV like a Xash of lightning with a very satisfactory resounding clap of thunder following. Even when he did not so plan events, they appeared to fashion themselves into spectacular climaxes. In 1896 while his fame was still on the ascendant he planned a nice quiet little vibration experiment in his Houston Street laboratory. Since he had moved into these quarters in 1895, the place had established a reputation for itself because of the peculiar noises and lights that emanated from it at all hours of the day and night, and because it was constantly being visited by the most famous people in the country.

The quiet little vibration experiment produced an earthquake, a real earthquake in which people and buildings and everything in them got a more tremendous shaking than they did in any of the natural earthquakes that have visited the metropolis. In an area of a dozen square city blocks, occupied by hundreds of buildings housing tens of thousands of persons, there was a sudden roaring and shaking, shattering of panes of glass, breaking of steam, gas and water pipes. Pandemonium reigned as small objects danced around rooms, plaster descended from walls and ceilings, and pieces of machinery weighing tons were moved from their bolted anchorages and shifted to awkward spots in factory lofts.

``It was all caused, quite unexpectedly, by a little piece of apparatus you could slip in your pocket,'' said Tesla.

The device that precipitated the sudden crisis had been used for a long time by Tesla as a toy to amuse his friends. It was a mechanical oscillator, and was used to produce vibrations. The motor-driven device that the barber straps on his hand to give a patron an ``electric massage'' is a descendant of Tesla's mechanical oscillator. There is, of course, nothing electric about an ``electric massage'' except the power used to produce vibrations which are transmitted through the barber's Wngers to the scalp.

Tesla developed in the early nineties a mechanical-electrical oscillator for the generation of high-frequency alternating currents. The driving engine produced on a shaft simple reciprocating motion that was not changed to rotary motion. Mounted on either end of the shaft was a coil of many turns of wire that moved back and forth with high frequency between the poles of electromagnets, and in this way generated high-frequency alternating currents.

The engine was claimed by Tesla to have a very high eYciency compared to the common type of engine, which changed reciprocating to rotary motion by means of a crank shaft. It had no valves or other moving parts, except the reciprocating piston with its attached shaft and coils, so that mechanical losses were very low. It maintained such an extremely high order of constancy of speed, he stated, that the alternating current generated by the oscillator could be used to drive clocks, without any pendulum or balance-wheel control mechanisms, and they would keep time more accurately than the sun.

This engine may have had industrial possibilities but Tesla was not interested in them. To him it was just a convenient way of producing a high-frequency alternating current constant in frequency and voltage, or mechanical vibrations, if used without the electrical parts. He operated the engine on compressed air and also by steam at 320 pounds and also at 80 pounds pressure.

While perfecting this device, he had opportunity to observe interesting eVects produced by vibration. These were objectionable in the engine when it was used as a dynamo, so he adopted suitable measures to eliminate or suppress them. The vibrations as such, however, interested him. Although they were detrimental to the machine, he found their physiological eVects were, at times, quite pleasant. Later he built a small mechanical oscillator driven by compressed air which was designed for no other purpose than to produce vibrations. He built a platform insulated from the Xoor by rubber and cork. He then mounted the oscillator on the under side of the platform. The purpose of the rubber and cork under the platform was to keep the vibrations from leaking into the building and thereby reducing the eVect on the platform. Visitors found this vibrating platform one of the most interesting of the great array of fascinating and fantastic exhibits with which he dazzled the society folk who Xocked to his laboratory.

Great hopes were entertained by Tesla of applying these vibrations for therapeutic and health-improving eVects. He had opportunity to observe, through his own experience and that of his employees, that they produce some very deWnite physiological actions.

Samuel Clemens, better known to the public as ``Mark Twain,'' and Tesla were close friends. Clemens was a frequent visitor to the Tesla laboratory. Tesla had been playing with his vibratory mechanism for some time, and had learned a good deal about the results that followed from varying doses of vibration, when one evening Clemens dropped in.

Clemens, on learning about the new mechanism, wanted to experience its vitalizing vibrations. He stood on the platform while the oscillator set it into operation. He was thrilled by the new experience. He was full of adjectives. ``This gives you vigor and vitality,'' he exclaimed. After he had been on the platform for a while Tesla advised him: ``You have had enough, Mr. Clemens. You had better come down now.''

``Not by a jugfull,'' replied Clemens. ``I am enjoying myself.''

``But you had better come down, Mr. Clemens. It is best that

you do so,'' insisted Tesla.

``You couldn't get me oV this with a derrick,'' laughed Clemens.

``Remember, I am advising you, Mr. Clemens.''

``I'm having the time of my life. I'm going to stay right up here and enjoy myself. Look here, Tesla, you don't appreciate what a wonderful device you have here to give a lift to tired humanity. . . . Clemens continued along this line for several minutes. Suddenly he stopped talking, bit his lower lip, straightened his body and stalked stiZy but suddenly from the platform.

``Quick, Tesla! Where is it?'' snapped Clemens, half begging, half demanding.

``Right over here, through that little door in the corner,'' said Tesla. ``And remember, Mr. Clemens, I advised you to come down some time ago,'' he called after the rapidly moving Wgure.

The laxative eVect of the vibrator was an old story to the members of the laboratory staV.

Tesla pursued his studies of mechanical vibrations in many directions. This was almost a virgin Weld for scientiWc research. Scarcely any fundamental research had been done in the Weld since Pythagoras, twenty-Wve hundred years before, had established the science of music through his study of vibrating strings; and many of the wonders with which Tesla had startled the world in the Weld of high-frequency and high-potential currents had grown out of his simple secret for tuning electrical circuits so that the electricity vibrated in resonance with its circuit. He now visualized mechanical vibrations building up resonance conditions in the same way, to produce eVects of tremendous magnitude on physical objects.

In order to carry out what he expected to be some minor and very small-scale experiments, he screwed the base of one of his small mechanical oscillators to an iron supporting pillar in the middle of his laboratory and set it into oscillation. It had been his observation that it took some time to build up its maximum speed of vibration. The longer it operated the faster the tempo it attained. He had noticed that all objects did not respond in the same way to vibrations. One of the many objects around the laboratory would suddenly go into violent vibration as it came into resonance with the fundamental vibration of the oscillator or some harmonic of it. As the period of the oscillator changed, the Wrst object would stop and some other object in resonance with the new rate would start vibrating. The reason for this selective response was very clear to Tesla, but he had never previously had the opportunity to observe the phenomenon on a really large scale.

Tesla's laboratory was on an upper Xoor of a loft building. It was on the north side of Houston Street, and the second house east of Mulberry Street. About three hundred feet south of Houston Street on the east side of Mulberry Street was the long, four-story red-brick building famous as Police Headquarters. Throughout the neighborhood there were many loft buildings ranging from Wve to ten stories in height, occupied by factories of all kinds. Sandwiched between them were the small narrow tenement houses of a densely packed Italian population. A few blocks to the south was Chinatown, a few blocks to the west was the garment-trades area, a short distance to the east was a densely crowded tenement-house district.

It was in this highly variegated neighborhood that Tesla unexpectedly staged a spectacular demonstration of the properties of sustained powerful vibrations. The surrounding population knew about Tesla's laboratory, knew that it was a place where strange, magical, mysterious events took place and where an equally strange man was doing fearful and wonderful things with that tremendously dangerous secret agent known as electricity. Tesla, they knew, was a man who was to be both venerated and feared, and they did a much better job of fearing than of venerating him.

Quite unmindful of what anyone thought about him, Tesla carried on his vibration and all other experiments. Just what experiment he had in mind on this particular morning will never be known. He busied himself with preparations for it while his oscillator on the supporting iron pillar of the structure kept building up an ever higher frequency of vibrations. He noted that every now and then some heavy piece of apparatus would vibrate sharply, the Xoor under him would rumble for a second or two--that a window pane would sing audibly, and other similar transient events would happen--all of which was quite familiar to him. These observations told him that his oscillator was tuning up nicely, and he probably wondered why he had not tried it Wrmly attached to a solid building support before.

Things were not going so well in the neighborhood, however. Down in Police Headquarters in Mulberry Street the ``cops'' were quite familiar with strange sounds and lights coming from the Tesla laboratory. They could hear clearly the sharp snapping of the lightnings created by his coils. If anything queer was happening in the neighborhood, they knew that Tesla was in back of it in some way or other.

On this particular morning the cops were surprised to feel the building rumbling under their feet. Chairs moved across Xoors with no one near them. Objects on the oYcers' desks danced about and the desks themselves moved. It must be an earthquake! It grew stronger. Chunks of plaster fell from the ceilings. A Xood of water ran down one of the stairs from a broken pipe. The windows started to vibrate with a shrill note that grew more intense. Some of the windows shattered.

``That isn't an earthquake,'' shouted one of the oYcers, ``it's that blankety-blank Tesla. Get up there quickly,'' he called to a squad of men, ``and stop him. Use force if you have to, but stop him. He'll wreck the city.''

The oYcers started on a run for the building around the corner. Pouring into the streets were many scores of people excitedly leaving near-by tenement and factory buildings, believing an earthquake had caused the smashing of windows, breaking of pipes, moving of furniture and the strange vibrations.

Without waiting for the slow-pokey elevator, the cops rushed up the stairs--and as they did so they felt the building vibrate even more strongly than did police headquarters. There was a sense of impending doom--that the whole building would disintegrate--and their fears were not relieved by the sound of smashing glass and the queer roars and screams that came from the walls and Xoors.

Could they reach Tesla's laboratory in time to stop him? Or would the building tumble down on their heads and everyone in it be buried in the ruins, and probably every building in the neighborhood? Maybe he was making the whole earth shake in this way! Would this madman be destroying the world? It was destroyed once before by water. Maybe this time it would be destroyed by that agent of the devil that they call electricity!

Just as the cops rushed into Tesla's laboratory to tackle--they knew not what--the vibrations stopped and they beheld a strange sight. They arrived just in time to see the tall gaunt Wgure of the inventor swing a heavy sledge hammer and shatter a small iron contraption mounted on the post in the middle of the room. Pandemonium gave way to a deep, heavy silence.

Tesla was the Wrst to break the silence. Resting his sledge hammer against the pillar, he turned his tall, lean, coatless Wgure to the cops. He was always selfpossessed, always a commanding presence--an eVect that could in no way be attributed to his slender build, but seemed more to emanate from his eyes. Bowing from the waist in his courtly manner, he addressed the policemen, who were too out of breath to speak, and probably overawed into silence by their fantastic experience.

``Gentlemen,'' he said, ``I am sorry, but you are just a triXe too late to witness my experiment. I found it necessary to stop it suddenly and unexpectedly and in an unusual way just as you entered. If you will come around this evening I will have another oscillator attached to this platform and each of you can stand on it. You will, I am sure, Wnd it a most interesting and pleasurable experience. Now you must leave, for I have many things to do. Good day, gentlemen.''

George ScherV, Tesla's secretary, was standing nearby when Tesla so dramatically smashed his earthquake maker. Tesla never told the story beyond this point, and Mr. ScherV declares he does not recall what the response of the cops was. Imagination must Wnish the Wnale to the story.

At the moment, though, Tesla was quite sincere in his attitude. He had no idea of what had happened elsewhere in the neighborhood as a result of his experiment, but the eVect on his own laboratory had been suYciently threatening to cause him to halt it suddenly. When he learned the details, however, he was convinced that he was correct in his belief that the Weld of mechanical vibrations was rich with opportunities for scientiWc investigation. We have no records available of any further major experiments with vibration in that laboratory. Perhaps the Police and Building Departments had oVered some emphatic suggestions to him concerning experiments of this nature.

Tesla's observations in this experiment were limited to what took place on the Xoor of the building in which his laboratory was located, but apparently very little happened there until a great deal had happened elsewhere. The oscillator was Wrmly Wxed to a supporting column and there were similar supporting columns directly under it on each Xoor down to the foundations. The vibrations were transmitted through the columns to the ground. This section of the city is built on deep sand that extends down some hundreds of feet before bed rock is reached. It is well known to seismologists that earthquake vibrations are transmitted by sand with much greater intensity than they are by rock. The ground under the building and around it was, therefore, an excellent transmitter of mechanical vibrations, which spread out in all directions. They may have reached a mile or more. They were more intense, of course, near their source and became weaker as the distance increased. However, even weak vibrations that are sustained can build up surprisingly large eVects when they are absorbed by an object with which they are in resonance. A distant object in resonance can be thrown into strong vibration whereas a much nearer object not in resonance will be left unaVected.

It was this selective resonance that was, apparently, operating in Tesla's experiment. Buildings other than his own came into resonance with the increasing tempo of his oscillator long before his own building was aVected. After the pandemonium was under way for some time elsewhere and the higher frequencies were reached, his immediate surroundings started to come into resonance.

When resonance is reached the eVects follow instantly and powerfully. Tesla knew this, so when he observed dangerous resonance eVects developing in his building he realized he had to act fast. The oscillator was being operated by compressed air supplied by a motor-driven compressor that fed the air into a tank, where it was stored under pressure. Even if the motor were shut oV, there was plenty of air in the tank to keep the oscillator going for many minutes--and in that time the building could be completely wrecked and reduced to a pile of debris. With the vibrations reaching this dangerous amplitude, there was no time to try to disconnect the vibrator from the air line or to do anything about releasing the air from the tank. There was time for only one thing, and Tesla did that. He grabbed the near-by sledge hammer and took a mighty swing at the oscillator in hopes of putting it out of operation. He succeeded in his Wrst attempt.

The device was made of cast iron and was of rugged construction. There were no delicate parts that could be easily damaged. Tesla has never published a description of the device, but its construction was principally that of a piston which moved back and forth inside a cast-iron cylinder. The only way to stop it from operating was to smash the outer cylinder. Fortunately, that is what happened from the Wrst blow.

As Tesla turned around after delivering this lucky blow and beheld the visiting policemen, he could not understand the reason for their visit. The dangerous vibrations had developed in his building only within the preceding minute, and the policemen would not have had time to plan a visit in connection with them, he Wgured, so they must have come for some other less critical purpose, and therefore he proposed to dismiss them until a more opportune moment.

Tesla related this experience to me when I asked the inventor's opinion of a plan that I had suggested some time previously to Elmer Sperry, Jr., son of the famous inventor of many gyroscope devices. When a heavy gyroscope, such as is used in stabilizing ships, is forced to turn on its axis, it transmits a powerful downward thrust through the bearings in which the supporting gimbal is mounted. If a battery of such gyroscopes were mounted in regions where severe earthquakes take place it would transmit thrusts to the ground at equally timed intervals and build up resonance vibrations in the strata of the earth that would cause earthquake strains to be released while they were of small magnitude, thus producing very small earthquakes instead of letting the strains build up to large magnitudes which, when they let go, would cause devastating earthquakes.

The idea made a strong appeal to Tesla; and in his discussion, after telling me of the experience here related, he further declared that he had so far developed his study of vibrations that he could establish a new science of ``telegeodynamics'' which would deal not only with the transmission of powerful impulses through the earth to distant points to produce eVects of large magnitude--in addition, he could use the same principles to detect distant objects. In the later thirties, before the outbreak of the war, he declared that he could apply these principles for the detection of submarines or other ships at a distance, even though they were lying at anchor and no engines operating on them.

His system of telegeodynamics, using mechanical vibrations, Tesla declared, would make it possible to determine the physical constant of the earth and to locate ore deposits far beneath the surface. This latter prediction has since been fulWlled, for many oil Welds have been discovered by studying the vibrations reXected from sub-surface strata.

``So powerful are the eVects of the telegeodynamic oscillator,'' said Tesla in reviewing the subject in the thirties, ``that I could now go over to the Empire State Building and reduce it to a tangled mass of wreckage in a very short time. I could accomplish this result with utmost certainty and without any diYculty whatever. I would use a small mechanical vibrating device, an engine so small you could slip it in your pocket. I could attach it to any part of the building, start it in operation, allow it twelve to thirteen minutes to come to full resonance. The building would Wrst respond with gentle tremors, and the vibrations would then become so powerful that the whole structure would go into resonant oscillations of such great amplitude and power that rivets in the steel beams would be loosened and sheared. The outer stone coating would be thrown oV and then the skeleton steel structure would collapse in all its parts. It would take about 2.5 (This Wgure may have been .25 or 2.5 horsepower. The notes are old and somewhat indistinct. Memory favors the latter Wgure.) horsepower to drive the oscillator to produce this eVect''

Tesla developed his inventions to the point at which they were spectacular performers before they were demonstrated to the public. When presented, the performance always greatly exceeded the promise. This was the case with his Wrst public demonstration of ``wireless,'' but he complicated the situation by coupling with his radio invention another new idea--the robot.

Tesla staged his demonstration in the great auditorium of Madison Square Garden, then on the north side of Madison Square, in September, 1898, as part of the Wrst annual Electrical Exhibition. He had a large tank built in the center of the arena and in this he placed an iron-hulled boat a few feet long, shaped like an ark, which he operated by remote control by means of his wireless system.

Extending upward from the center of the roof of the boat was a slender metal rod a few feet high which served as an antenna, or ærial, for receiving the wireless wave. Near the bow and stern were two small metal tubes about a foot high surmounted by small electric lamps. The interior of the hull was packed with a radio receiving set and a variety of motor-driven mechanisms which put into eVect the operating orders sent to the boat by wireless waves. There was a motor for propelling the boat and another motor for operating the servo-mechanism, or mechanical brain, that interpreted the orders coming from the wireless receiving set and translated them into mechanical motions, which included steering the boat in any direction, making it stop, start, go forward or backward, or light either lamp. The boat could thus be put through the most complicated maneuvers.

Anyone attending the exhibition could call the maneuver for the boat, and Tesla, with a few touches on a telegraph key, would cause the boat to respond. His control point was at the far end of the great arena.

The demonstration created a sensation and Tesla again was the popular hero. It was a front-page story in the newspapers. Everyone knew the accomplishment was a wonderful one, but few grasped the signiWcance of the event or the importance of the fundamental discovery which it demonstrated. The basic aspects of the invention were obscured by the glamor of the demonstration.

The Spanish American War was under way. The success of the U.S. Navy in destroying the Spanish Xeets was the leading topic of conversation. There was resentment over the blowing up of the U.S.S. Maine in Havana Harbor. Tesla's demonstration Wred the imagination of everyone because of its possibilities as a weapon in naval warfare.

Waldemar KaempVert, then a student in City College and now Science Editor of the New York Times, discussed its use as a weapon with Tesla.

``I see,'' said KaempVert, ``how you could load an even larger boat with a cargo of dynamite, cause it to ride submerged, and explode the dynamite whenever you wished by pressing the key just as easily as you can cause the light on the bow to shine, and blow up from a distance by wireless even the largest of battleships.'' (Edison had earlier designed an electric torpedo which received its power by a cable that remained connected with the mother ship.)

Tesla was patriotic, and was proud of his status, which he had acquired in 1889, as a citizen of the United States. He had oVered his invention to the Government as a naval weapon, but at heart he was opposed to war.

``You do not see there a wireless torpedo,'' snapped back Tesla with Wre Xashing in his eyes, ``you see there the Wrst of a race of robots, mechanical men which will do the laborious work of the human race.

The ``race of robots'' was another of Tesla's original and important contributions to human welfare. It was one of the items of his colossal project for increasing human energy and improving the eYciency of its utilization. He visualized the application of the robot idea to warfare as well as to peaceful pursuits; and out of the broad principles enunciated, he developed an accurate picture of warfare as it is being carried on today with the use of giant machines as weapons--the robots he described.

``This evolution,'' he stated in an article in the Century Magazine of June, 1900, ``will bring more and more into prominence a machine or mechanism with the fewest individuals as an element of warfare. . . . Greatest possible speed and maximum rate of energy delivery by the war apparatus will be the main object. The loss of life will become smaller. . . .''

Outlining the experiences that led him to design the robots, or automatons, as he called them, Tesla stated:

I have by every thought and act of mine, demonstrated, and do so daily, to my absolute satisfaction that I am an automaton endowed with power of movement, which merely responds to external stimuli beating upon my sense organs, and thinks and moves accordingly. . . .

With these experiences it was only natural that, long ago, I conceived the idea of constructing an automaton which would mechanically represent me, and which would respond, as I do myself, but, of course, in a much more primitive manner, to external inXuences. Such an automaton evidently had to have motive power, organs for locomotion, directive organs, and one or more sensitive organs so adapted as to be excited by external stimuli.

This machine would, I reasoned, perform its movements in the manner of a living being, for it would have all of the chief elements of the same. There was still the capacity for growth, propagation, and, above all, the mind which would be wanting to make the model complete. But growth was not necessary in this case since a machine could be manufactured full-grown, so to speak. As to capacity for propagation, it could likewise be left out of consideration, for in the mechanical model it merely signiWed a process of manufacture.

Whether the automaton be of Xesh and bone, or of wood and steel, mattered little, provided it could perform all the duties required of it like an intelligent being. To do so it would have to have an element corresponding to the mind, which would eVect the control of its movements and operations, and cause it to act, in any unforeseen case that might present itself, with knowledge, reason, judgement and experience. But this element I could easily embody in it by conveying to it my own intelligence, my own understanding. So this invention was evolved, and so a new art came into existence, for which the name ``telautomatics'' has been suggested, which means the art of controlling the movements and operations of distant automatons.

In order to give the automaton an individual identity it would be provided with a particular electrical tuning, Tesla explained, to which it alone would respond when waves of that particular frequency were sent from a control transmitting station; and other automatons would remain inactive until their frequency was transmitted. This was Tesla's fundamental radio tuning invention, the need for which other radio inventors had not yet glimpsed although Tesla had described it publicly a half-dozen years earlier.

Tesla not only used in the control of his automaton the long waves now used in broadcasting--which are very diVerent from the short waves used by Marconi and all others; for those could be interfered with by the imposition of an intervening object--but he was explaining the use, through his system of tuning, of the spectrum of allocations for individual stations that now appears on the dials of radio receiving sets. He continued:

By the simple means described the knowledge, experience, judgement--the mind, so to speak--of the distant operator were embodied in that machine, which was thus enabled to move and perform all of its operations with reason and intelligence. It behaved just like a blindfolded person obeying directions received through the ear.

The automatons so far constructed had ``borrowed minds,'' so to speak, as each formed merely part of the distant operator who conveyed to it his intelligent orders; but this art is only in the beginning.

I purpose to show that, however impossible it may now seem, an automaton may be contrived which will have its ``own mind,'' and by this I mean that it will be able, independently of any operator, left entirely to itself, to perform, in response to external inXuences aVecting its sensitive organs, a great variety of acts and operations as if it had intelligence.

It will be able to follow a course laid out or to obey orders given far in advance; it will be capable of distinguishing between what it ought and ought not to do, and of making experiences or, otherwise stated, of recording impressions which will deWnitely aVect its subsequent actions. In fact I have already conceived such a plan.

Although I evolved this invention many years ago and explained it to my visitors very frequently in my laboratory demonstrations, it was not until much later, long after I had perfected it, that it became known, when, naturally enough, it gave rise to much discussion and to sensational reports.

But the true signiWcance of this new art was not grasped by the majority, nor was the great force of the underlying principle recognized. As nearly as I could judge from the numerous comments which then appeared, the results I had obtained were considered as entirely impossible. Even the few who were disposed to admit the practicability of the invention saw in it merely an automobile torpedo, which was to be used for the purpose of blowing up battleships, with doubtful success. . . .

But the art I have evolved does not contemplate merely the change of direction of a moving vessel; it aVords means of absolutely controlling in every respect, all the innumerable translatory movements, as well as the operations of all the internal organs, no matter how many, of an individualized automaton.

Tesla, in an unpublished statement, prepared Wfteen years later, recorded his experience in developing automata, and his unsuccessful eVort to interest the War Department, and likewise commercial concerns, in his wirelessly controlled devices.

The idea of constructing an automaton, to bear out my theory, presented itself to me early but I did not begin active work until 1893, when I started my wireless investigations. During the succeeding two or three years, a number of automatic mechanisms, actuated from a distance by wireless control, were constructed by me and exhibited to visitors in my laboratory.

In 1896, however, I designed a complete machine capable of a multitude of operations, but the consummation of my labors was delayed until later in 1897. This machine was illustrated and described in my article in the Century Magazine of June 1900, and other periodicals of that time and, when Wrst shown in the beginning of 1898, it created a sensation such as no other invention of mine has ever produced.

In November 1898, a basic patent on the novel art was granted to me, but only after the Examiner-in-Chief had come to New York and witnessed the performance, for what I claimed seemed unbelievable. I remember that when later I called on an oYcial in Washington, with a view of oVering the invention to the Government, he burst out in laughter upon my telling him what I had accomplished. Nobody thought then that there was the faintest prospect of perfecting such a device.

It is unfortunate that in this patent, following the advice of my attorneys, I indicated the control as being eVected through the medium of a single circuit and a well-known form of detector, for the reason that I had not yet secured protection on my methods and apparatus for individualization. As a matter of fact, my boats were controlled through the joint action of several circuits and interference of every kind was excluded. Most generally I employed receiving circuits in the form of loops, including condensers, because the discharges of my high tension transmitter ionized the air in the hall so that even a very small ærial would draw electricity from the surrounding atmosphere for hours.

Just to give an idea, I found, for instance, that a bulb 12'' in diamater, highly exhausted, and with one single terminal to which a short wire was attached, would deliver well on to one thousand successive Xashes before all charge of the air in the laboratory was neutralized. The loop form of receiver was not sensitive to such a disturbance and it is curious to note that it is becoming popular at this late date. In reality it collects much less energy than the ærials or a long grounded wire, but it so happens that it does away with a number of defects inherent to the present wireless devices.

In demonstrating my invention before audiences, the visitors w