Nikola Tesla and His Work * (by Nelson W. Perry, E. M.)

It is not often that it is in good taste to estimate the character of a man while he is living, or safe to weigh his works or to estimate their proper place in any science while it is still in an embryotic state. There are exceptions, however, as in the case of political and other celebrities who, by reason of their eminence, have become in a sense public characters, or whose work has already revolutionized the science in the interest of which it has been undertaken. Under both of these exceptions it seems altogether proper to speak of Mr. Nikola Tesla, for if a man by taking two continents by storm may be called a public character in the sense in which the expression is here used, Mr. Tesla is one, and if the discovery of a new system such as the rotary magnetic field which in a few years has largely revolutionized our methods of conversion of electrical into mechanical energy, and which has formed the basis of the greatest attempt at power-transmission ever made, partakes of the nature of a revolution of the science, then for this reason, may Mr. Tesla's work be reviewed with propriety while their author is still in the flesh.

Mr. Tesla was born in 1857, and therefore is still quite a young man, but he has crowded within his thirty-seven years of life an experience that would be considered ripe for any one of a dozen other men if it were divided equally among them. While foreign-born (at Smiljan-Lika on the borderland of Austro-Hungary), he is an American by adoption. Though proud of his adopted country he is not so intensely American as some foreigners become who adopt this country as their home.

The one discovery of Mr. Tesla which among practical men stands out most prominently to-day, because of the practical results already obtained, is his discovery of what is generally known as the rotating magnetic field. The alternating current, as the name would imply, means a current which changes its direction periodically. It possesses many characteristics peculiar to itself. The distinct advantage of an alternating or undulating current over a steady current such as heretofore used in arc-lighting is, that one is able to dispense with a large resistance in the dynamos and lamps which are necessary in order to obtain a steady light. This produces a greater economy in the circuit all along. For transmission purposes its advantages so far outweigh its disadvantages as to make it the method par excellence. Alternating-current motors enable us to obtain results which are not possible with motors heretofore used, namely: the motor may be made to run in perfect synchronism with the generators. In the ordinary motors the speed as is known falls below this increase, but not so in the motors just mentioned. But if one desires it is possible also to exactly imitate an ordinary direct-current motor and produce a machine which will have a great effort on the start.

Mr. Tesla conceived an idea which has entirely overcome the shortcomings of the alternating current as applied to motors. Every one knows — or at least is easy of demonstration — that if the north and south poles of a small horseshoe magnet be suspended over a bar of soft iron free to revolve in a horizontal plane, or be placed over an ordinary compass-needle, the latter will be attracted at either end by the poles of the magnet and take up a position parallel to a straight line drawn between the two poles of the magnet. Now if the latter be revolved through any angle the soft iron or needle will follow, being dragged around by the magnet, and if the magnet be caused to revolve regularly the iron will also revolve, being pulled around by the full force of the magnet. It was not feasible, however, to cause the magnet to revolve in this way, and Tesla's invention consisted in obviating this trouble and, in fact, in greatly simplifying the problem. He conceived the idea that if he took an iron ring and used two alternating currents, one of which had its maximum value at the instant that the other had a zero value — or, in other words, two currents whose periods were such that one waned. as the other increased — he could produce in that iron ring by winding these circuits in alternate coils surfaces that without any mechanical movement of the parts would travel around that ring with a rapidity equal to the number of changes of direction of the currents employed. He thus had a ring, the north and south poles of which were rapidly revolving just as would the poles of the horseshoe magnet were it tied at its middle to a twisted string and allowed to revolve. A piece of iron pivoted at its middle placed concentric with this ring would therefore be dragged around by the changing poles of the ring. He had thus discovered what is somewhat awkwardly expressed by the expression, the rotary magnetic field," and also the use of what have been termed "polyphased currents" — the one referring to the magnetism and the other to the combination of currents by which this changing magnetism was produced. This discovery is undoubtedly one of the most important that has ever been made within the domain of alternating currents, and marks a most important step in applied electricity; in fact, it may be said to have been epoch-making, for without this method the experiment of transmitting 100 horse-power, 108 miles from Lauffen on the falls of the Neckar to the Frankfort Exposition grounds, in 1891, would have been impracticable.

If two separate currents are employed as Tesla employs them, we have what is called a "diphased" system; if three are employed it is called a "triphased system; but in speaking of the employment of more than one current the generic term "polyphased" is used. Tesla's discovery is the basis of them all. The Frankfort-Lauffen experiment referred to was operated on the three-phased system. The great scheme of transmitting Niagara's power to distant points, which in magnitude far surpasses the former experiment, will employ the original Tesla diphased system. 

His first successful experiment was in 1883, but the first practical motor that showed good efficiency was only obtained in 1887. Ferraris published a pamphlet bearing on the broad principles and some features of the discovery in May, 1888, but six months prior to this, that is in October, 1887, Tesla's first fundamental applications were filed in the Patent Office in Washington.

There is no conflict between Ferraris and Tesla, each according to the other full honor and credit for the work individually done.

As before stated, the discovery of the rotary field has nearly revolutionized the practice of tranmission of energy by alternating currents and the practical value of the invention is fully attested by the adoption by the most eminent experts in the world of the Tesla system for the Niagara electrical plant, by which it is proposed to transmit eventually at least 100,000 horse-power from the falls to various points along the Erie canal, as far as such transmission may prove economical. This invention at once attracted the eyes of the scientific world to Mr. Tesla, who was until then comparatively unknown. He has, however, been an indefatigable worker and has made many inventions which have attracted little attention, often only because of their lesser importance. Mr. T. Commerford Martin, in his exhaustive work on the "Inventions, Researches, and Writings of Nikola Tesla," catalogues 137 inventions or discoveries made by this man. There is not room here for even this catalogue and in discussing his work it will be necessary for me to confine myself strictly to a few of his accomplishments upon which his fame chiefly depends.

Mr. Tesla early turned his attention to phenomena of alternating currents of high frequency and high potential. These brilliant effects which have so much interested scientific men are obtained in his experiments by a peculiar arrangement of condensers and coils, which enables him to obtain enormous potentials of a million volts or more which are alternated in direction many million times a second, if necessary. In the reports of his lectures his apparatus is minutely described, but limited space does not permit me to dwell upon it here. Others had experimented with currents of several thousand volts and as many reversals or more per minute. The phenomena thereby produced were so interesting as to lead Mr. Tesla to explore the field further. He employed currents of hundreds of thousands of volts and having more than 2,000,000 reversals per minute. With these elements at hand he possessed the key with which he unlocked entirely unexplored avenues and produced effects, especially of light, that literally dazzled the scientific world.

Maxwell had taught the world to believe that ordinary light was due to electromagnetic waves of the ether, having a frequency per second of 5 with 14 ciphers after it. He did not prove this, but arrived at his conclusions through mathematical logic. Later Heinrich Hertz proved the truth of these deductions experimentally. This meant that if, by any possible means, we could artificially produce ether waves of this frequency, we would have light without heat and a useful efficiency for the energy expended of about 99 per cent. instead of an efficiency of less than I per cent. as obtained in our best gas-burners. We can readily produce etheric waves of a frequency of some hundreds of thousands and even millions, but these fall far short of the requirements in the case, and there were practical obstacles in the way preventing the slightest hope of our ever being able to produce the required frequency or to transmit them if we could produce them. It was Tesla's idea that the desired results were possible of attainment by means of powerful electro-static effects which, by the way, he was able to produce by his peculiar methods and apparatus invented for this purpose and high potentials.

Of course the general bearing of these experiments is upon the problem of an efficient production of light, but in his lectures many scientific facts are pointed out, which contributed to a radical change in scientific opinion in regard to a number of phenomena. So for instance it was demonstrated that a gaseous medium like air, when electric stress of great intensity and frequency were made to act through it, becomes rigid. The agitation produced by the stress in the molecules of the air is such as to render the air luminous, and he produced in some experiments streams of light by merely charging the body. In fact it appears possible from some experiments that a flame might be produced which would appear to be ordinary gas-flame and yet it 

the sun. would be a solid. The phenomenon of the aurora borealis and of the electric storms are usually attributed to the changes of the potential of A very important fact was demonstrated that in an electrical condenser and in any insulating material, the air must be kept away. As long as this fact was not known it was not possible to properly insulate parts of high tension.

I give here a paragraph on this subject in his own words: **

But powerful electro-static effects are a sine qua non of light-production on the lines indicated by theory. Electromagnetic effects are primarily unavailable, for the reason that to produce the required effects we would have to pass current impulses through a conductor, which, long before the required frequency of the impulses could be reached, would cease to transmit them. On the other hand, electromagnetic waves many times longer than those of light, and producible by sudden discharge of a condenser, could not be utilized.... We could not affect by means of such waves the static molecular or atomic charges of a gas, cause them to vibrate and emit light.

To produce such luminous effects, straight electro-static thrusts are required; these, whatever be their frequency, may disturb the molecular charges and produce light.

It is to be regretted that lack of space here prevents the elucidation of the terms used, but the fact will be well understood without this, that the production of light practically without heat is within the bounds of possibility. This was Tesla's grand discovery and it was this that dazzled the mental vision of the scientific world. It only remained for him to illustrate his theory by experiments that the physical vision of the world should also be dazzled. He further says:

It has occurred to me, however, that electro-static effects 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 more or less 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 manner, with trillions of invisible hammers, pound it until it gets incandescent; or we may place a body in a very highly exhausted globe, in a non-striking vacuum, and by employing very high frequencies and potentials, transfer sufficient energy from it to other bodies in the vicinity, or in general to the surroundings, to maintain it at any degree of incandescence, or we may, by means of such rapidly alternating high potentials, disturb the ether carried by the molecules of a gas or their static charges, causing them to vibrate and to emit light.

Here are clearly enunciated three distinct methods of producing light by electro-static action, any one of which would have startled the scientific world if founded solely on hypothesis. Tesla's announcement was based on no such unstable basis as this, however; it was based on Some of experimental data which he reproduced before his audiences. these effects had in fact been produced in a feeble way by previous investigators in a somewhat different manner, but it remained for Tesla to bring them out in a far more brilliant way than any of his predecessors and thereby to call attention to their importance that they had not previously attracted. In regard to this, he says:

But electro-static effects being dependent upon the potential and frequency, to produce the most powerful action it is desirable to increase both as far as practicable. [Tesla was the first to realize and practise this.] It may be possible to obtain quite fair results by keeping either of these factors small provided the other is sufficiently great; but we are limited in both directions. My experience demonstrates that we cannot go below a certain frequency, for, first the potential then becomes so great that it is dangerous; and secondly, the light production is less efficient.

Speaking of what has been termed the bombardment method (the first of the three above mentioned), he says:

There is no difficulty in reaching such high degrees of incandescence that ordinary carbon is to all appearance melted and volatilized. If the vacuum could be made absolutely perfect, such a lamp, although inoperative with apparatus ordinarily used, would, if operated with currents of the required character, afford an illuminant which would never be destroyed, and which would be far more efficient than an ordinary incandescent lamp.

In lamps constructed on this principle, the filament or button of refractory material was connected to but one terminal of the circuit instead of to both as necessary in present practice.

In regard to the second method, Mr. Tesla says:

The use of alternating currents of very high frequency makes it possible to transfer, by electro-static or electromagnetic induction through the glass of the lamp, sufficient energy to keep a filament at incandescence and so do away with the leading in wires. Many forms of lamps on this principle with continuous and broken filaments have been constructed by me and experimented upon.

Thus far he had used in the first case a single connection to the source of energy and in the second no connection at all, but in both cases some refractory material within the globe was brought to incandescence and served as the light-giving body. In the third method, however, he used neither connections nor filaments or buttons, but merely exhausted tubes having no electrodes whatever. Such tubes when grasped in the hands of the experimenter standing near an induction coil became luminous themselves. This seems to be a most remarkable phenomenon, as there is nothing from which the light can emanate. It would seem that the tubes were filled with a luminous substance which was light itself. Speaking of this phenomenon he says:

In all cases, then, when we excite luminosity in exhausted tubes by means of such a coil, the effect is due to the rapidly alternating electro-static potential and furthermore it must be attributed to the harmonic alternation produced by the machine and not to any superposed vibration which might be thought to exist..... .In all the last-described experiments, tubes devoid of any electrodes may be used and there is no difficulty in producing by their means sufficient light to read by. The light effect is, however, considerably increased by the use of phosphorescent bodies such as yttria, uranium glass, etc.

But he caps the climax of this brilliant series of experiments by producing conditions whereby a vacuum tube without electrodes may be moved anywhere within the room and, with no connection whatever to the walls, still remain luminous. He says:

For this purpose I suspend a sheet of metal a distance from the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal being preferably connected with the ground; or else I suspend two sheets, each being connected to one terminal of the coil, and their size being carefully determined. An exhausted tube may then be carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond them; it remains always luminous.

During this lecture Mr. Tesla performed all of the experiments referred to and many more before his audience and then, summing up his own belief as to their value, he said:

How far the results here borne out are capable of practical applications will be decided in the future. As regards the production of light, some results already reached are encouraging and make me confident in asserting that the practical solution of the problem lies in the direction I have endeavored to indicate. Still, whatever may be the immediate outcome of these experiments I am hopeful that they will only prove a step in further development towards the ideal and final perfection. The possibilities which are opened by modern research are so vast that even the most reserved must feel sanguine of the future. Eminent scientists consider the problem of utilizing one kind of radiation without the others a rational one. In an apparatus designed for the production of light by conversion from any form of energy into that of light, such a result can never be reached, for no matter what the process of producing the required vibrations, be it electrical, chemical, or any other, it will not be possible to obtain the higher light vibrations without going through the lower heat vibrations. It is the problem of imparting to a body a certain velocity without passing through all lower velocities. But there is a possibility of obtaining energy not only in the form of light, but motive power, and energy of any other form, in some more direct way from the medium. The time will be when this will be accomplished, and the time has come when one may utter such words before an enlightened audience without being considered a visionary. We are whirling through endless space with an inconceivable speed; all around us everything is spinning, everything is moving, everywhere is energy. There must be some way of availing ourselves of this energy more directly. Then, with the light obtained from the medium, with the power derived from it, with every form of energy obtained without effort, from the store forever inexhaustible, humanity will advance with giant strides. The mere contemplation of these magnificent possibilities expands our minds, strengthens our hopes, and fills our hearts with supreme delight.

While none of these experiments on light have developed into practical processes, they constitute one of the most remarkable contributions to physical science since the days of Faraday. In the brilliancy of their conception and the beauty of the results obtained we are apt to lose sight of the great inventive genius that was required to devise and prepare apparatus suitable for their public production. Nowhere has the genius of Tesla been displayed to better advantage than in the production of suitable means to the desired ends, and the last public announcement he has made was a description of a mechanical and electrical oscillator by which his investigations of alternating currents would be facilitated.

His lecture of May 20, 1891, echoed around the world and attracted the attention of the gray-haired savants of Europe. He was at once besieged by invitations to repeat his lecture abroad and, on February 3, 1892, he delivered his lecture with some additions before the most learned men of England, and received at their hands an ovation such as has perhaps never before been accorded to a scientific man. The last public appearance of Mr. Tesla was in a lecture during the Electrical Congress at the World's Fair, which was attended by the principal savants of Europe and America.

But Mr. Tesla is having the experience of all pioneers whose work does not show immediate practical results. One of the leading savants of Europe said to me after Tesla's last lecture: "His work is brilliant, but of what use is it? I would rather see him devote his energies to something more practical." At this lecture Mr. Tesla exhibited and described a mechanical oscillator in which he had great confidence. He believed that its future possibilities in a practical way were great. He is still of that opinion and, notwithstanding the criticism just quoted, Mr. Tesla says that this invention contains the germ of the most practical work he has ever done. He probably knows best about this and we shall await the outcome with great interest. We are not at liberty to speak freely concerning this invention at this time, but when Mr. Tesla is ready to make an announcement we may hear something startling.

I believe that this sentiment finds considerable response among the scientists abroad. Faraday was constantly met with the question, cui bono? and Tesla cannot hope to escape the same experience. Faraday's minute electric spark obtained by electromagnetic induction was his baby. The question was reiterated, cui bono ? That baby has now grown to man's estate and appears in the form of the 5000 horse-power Tesla generators now nearly completed for the great Niagara Falls transmission plant. The experiments in light, a few of which I have briefly referred to, are Tesla's babies. Who knows how they may appear in mature development?

My own estimate of Tesla is that his is one of the most vigorous and original minds the world has ever produced. Whether he will ever rank with Faraday, whom he resembles in many ways, I do not know, but there is no one in history whose work and character so closely resembles Faraday's to my mind as Tesla's. But Tesla's work is not finished. He is now engaged on something which he tells me he regards as the best work that he has ever done. What it may be the near future will disclose. It is unfair to write one's eulogium until his work is done. Tesla's work, perhaps, has only commenced.

* In the publisher's announcement, some months ago, of a series of papers on "Electrical Science up to Date," was included the promise of a paper in this volume of THE ENGINEERING MAGAZINE, by Mr. Nikola Tesla, on "Electric-Lighting Without Heat." Only the unfortunate condition of the health of Mr. Tesla has postponed his compliance with his engagement in this connection. In order to keep faith, so far as possible, with the readers of the Magazine, there is presented herewith a paper by an electrical engineer who enjoys the acquaintance of Mr. Tesla, reviewing the discoveries of the latter gentleman which it was hoped that the inventor himself would be able to describe for us. The paper thus prepared has received the approval of Mr. Tesla, who, indeed, furnished personally some of the suggestions upon which it is based. - THE EDITOR.

** Tesla's lecture before the American Institute of Electrical Engineers, delivered at the School of Mines, Columbia College, May 20, 1891.