(Communicated to the Thirtieth Anniversary Number of the Electrical World and Engineer, March 5, 1904.)
BY NIKOLA TESLA.
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It is impossible to resist your courteous request extended on an occasion of such moment in the life of your journal. Your letter
has vivified the memory of our beginning friendship, of the first imperfect attempts and undeserved successes, of kindnesses
and misunderstandings. It has brought painfully to my mind the greatness of early expectations, the quick flight of time, and
alas the smallness of realizations. The following lines which, but for your initiative, might not have been given to the world for
a long time yet, are an offering in the friendly spirit of old, and my best wishes for y6ur future success accompany them.
Towards the close of 1898 a systematic research, carried on for a number of years with the object of perfecting a method of
transmission of electrical energy through the natural medium, led me to recognize three important necessities: First, to develop
a transmitter of great power; second, to perfect means for individualizing and isolating the energy transmitted; and, third, to
ascertain the laws of propagation of currents through the earth and the atmosphere. Various reasons, not the least of which was
the help proffered by my friend Leonard E. Curtis and the Colorado Springs Electric Company, determined me to select for my
experimental investigations the large plateau, two thousand meters above sea-level, in the vicinity of that delightful resort,
which I reached late in May, 1899. I had not been there but a few days when I congratulated myself on the happy choice and I
began the task, for which I had long trained myself, with a grateful sense and full of inspiring hope. The perfect purity of the
air, the unequaled beauty of the sky, the imposing sight of a high mountain range, the quiet and restful-ness of the place--all
around contributed to make the conditions for scientific observation ideal. To this was added the exhilarating influence of a
glorious climate and a singular sharpening of the senses. In those regions the organs undergo perceptible physical changes. The
eyes assume an extraordinary limpidity, improving vision; the ears dry out and become more susceptible to sound. Objects can
be clearly distinguished there at distances such that I prefer to have them told by someone else, and I have heard--this I can
venture to vouch for--the claps of thunder seven and eight hundred kilometers away. I might have done better still, had it not
been tedious to wait for the sounds to arrive, in definite intervals, as heralded precisely by an electrical indicating apparatus--
nearly an hour before.
Experimental Laboratory, Colorado Springs.
In the middle of June, while preparations for other work were going on, I arranged one of my receiving transformers with the
view of determining in a novel manner, experimentally, the electric potential of the globe and studying its periodic and casual
fluctuations. This formed part of a plan carefully mapped out in advance. A highly sensitive, self-restorative device, controlling
a recording instrument, was included in the secondary circuit, while the primary was connected to the ground and an elevated
terminal of adjustable capacity. The variations of potential gave rise to electric surgings in the primary; these generated
secondary currents, which in turn affected the sensitive device and recorder in proportion to their intensity. The earth was
found to be, literally, alive with electrical vibrations, and soon I was deeply absorbed in this interesting investigation. No better
opportunities for such observations as I intended to make could be found anywhere. Colorado is a country famous for the
natural displays of electric force. In that dry and rarefied atmosphere the sun's rays beat the objects with fierce intensity. I
raised steam, to a dangerous pressure, in barrels filled with concentrated salt solution, and the tin-foil coatings of some of my
elevated terminals shriveled up in the fiery blaze. An experimental high-tension former, carelessly exposed to the rays of the
setting sun, had most of its insulating compound melted out and was rendered useless. Aided by the dryness and rarefaction of
the air, the water evaporates as in a boiler, and static electricity is developed in abundance. Lightning discharges are, ac-
cordingly, very frequent and sometimes of inconceivable violence. On one occasion approximately twelve thousand discharges
occurred in two hours, and all in a radius of certainly less than fifty kilometers from the laboratory. Many of them resembled
gigantic trees of fire with the trunks up or down. I never saw fire balls, but as a compensation for my disappointment I
succeeded later in determining the mode of their formation and producing them artificially.
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Tesla's tower at Wardenclyffe for sending messages across the Atlantic and
electricity into the atmosphere as it appeared in 1904.
The letterhead for his stationary, promising "ten million Horsepower" of
"Electrical oscillator activity."
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In the latter part of the same month I noticed several times that my instruments were affected stronger by discharges taking
place at great distances than by those near by. This puzzled me very much. What was the cause? A number of observations
proved that it could not be due to the differences in the intensity of the individual discharges, and I readily ascertained that the
phenomenon was not the result of a varying relation between the periods of my receiving circuits and those of the terrestrial
disturbances. One night, as I was walking home with an assistant, meditating over these experiences, I was suddenly staggered
by a thought. Years ago, when I wrote a chapter of my lecture before the Franklin Institute and the National Electric Light
Association, it had presented itself to me, but I had dismissed it as absurd and impossible. I banished it again. Nevertheless, my
instinct was aroused and somehow I felt that I was nearing a great revelation.
It was on the third of July--the date I shall never forget-- when I obtained the first decisive experimental evidence of a truth
of overwhelming importance for the advancement of humanity. A dense mass of strongly charged clouds gathered in the west
and towards the evening a violent storm broke loose which, after spending much of its fury in the mountains, was driven away
with great velocity over the plains. Heavy and long persisting arcs formed almost in regular time' intervals. My observations
were now greatly facilitated and rendered more accurate by the experiences already gained. I was able to handle my
instruments quickly and I was prepared. The recording apparatus being properly adjusted, its indications became fainter and
fainter with the increasing distance of the storm, until they ceased altogether. I was watching in eager expectation. Surely
enough, in a little while the indications again began, grew stronger and stronger and, after passing through a maximum,
gradually decreased and ceased once more. Many times, in regularly recurring intervals, the same actions were repeated until
the storm which, as evident from simple computations, was moving with nearly constant speed, had retreated to a distance of
about three hundred kilometers. Nor did these strange actions stop then, but continued to manifest themselves with
undiminished force. Subsequently, similar observations were also made by my assistant, Mr. Fritz Lowenstein, and shortly
afterward several admirable opportunities presented themselves which brought out, still more forcibly, and unmistakably, the
true nature of the wonderful phenomenon. No doubt whatever remained: I was observing stationary waves.
As the source of disturbances moved away the receiving circuit came successively upon their nodes and loops. Impossible as it
seemed, this planet, despite its vast extent, behaved like a conductor of limited dimensions. The tremendous significance of
this fact in the transmission of energy by my system had already become quite clear to me. Not only was it practicable to send
telegraphic messages to any distance without wires, as I recognized long ago, but also to impress upon the entire globe the faint
modulations of the human voice, far more still, to transmit power, in unlimited amounts, to any terrestrial distance and almost
without any loss.
Experimental Laboratory, Colorado Springs.
With these stupendous possibilities in sight, with the experimental evidence before me that their realization was henceforth
merely a question of expert knowledge, patience and skill, I attacked vigorously the development of my magnifying
transmitter, now, however, not so much with the original intention of producing one of great power, as with the object of
learning how to construct the best one. This is, essentially, a circuit of very high self-induction and small resistance which in
its arrangement, mode of excitation and action, may be said to be the diametrical opposite of a transmitting circuit typical of
telegraphy by Hertzian or electromagnetic radiations. It is difficult to form an adequate idea of the marvelous power of this
unique appliance, by the aid of which the globe will be transformed. The electromagnetic radiations being reduced to an
insignificant quantity, and proper conditions of resonance maintained, the circuit acts like an immense pendulum, storing
indefinitely the energy of the primary exciting impulses and impressions upon the earth and its conducting atmosphere uniform
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harmonic oscillations of intensities which, as actual tests have shown, may be pushed so far as to surpass those attained in the
natural displays of static electricity.
Simultaneously with these endeavors, the means of individualization and isolation were gradually improved. Great importance
was attached to this, for it was found that simple tuning was not sufficient to meet the vigorous practical requirements. The
fundamental idea of employing a number of distinctive elements, cooperatively associated, for the purpose of isolating energy
transmitted, I trace directly to my perusal of Spencer's clear and suggestive exposition of the human nerve mechanism. The
influence of this principle on the transmission of intelligence, and electrical energy in general, cannot as yet be estimated, for
the art is still in the embryonic stage; but many thousands of simultaneous telegraphic and telephonic messages, through one
single conducting channel, natural or artificial, and without serious mutual interference, are certainly practicable, while
millions are possible. On the other hand, any desired degree of individualization may be secured by the use of a great number
of co-operative elements and arbitrary variation of their distinctive features and order of succession. For obvious reasons, the
principle will also be valuable in the extension of the distance of transmission.
Progress though of necessity slow was steady and sure, for the objects aimed at were in a direction of my constant study and
exercise. It is, therefore, not astonishing that before the end of 1899 I completed the task undertaken and reached the results
which I have announced in my article in the Century Magazine of June, 1900, every word of which was carefully weighed.
Much has already been done towards making my system commercially available, in the transmission of energy in small
amounts for specific purposes, as well as on an industrial scale. The results attained by me have made my scheme of
intelligence transmission, for which the name of "World Telegraphy" has been suggested, easily realizable. It constitutes, I
believe, in its principle of operation, means employed and capacities of application, a radical and fruitful departure from what
has been done heretofore. I have no doubt that it will prove very efficient in enlightening the masses, particularly in still
uncivilized countries and less accessible regions, and that it will add materially to general safety, comfort and convenience, and
maintenance of peaceful relations. It involves the employment of a number of plants, all of which are capable of transmitting
individualized signals to the uttermost confines of the earth. Each of them will be preferably located near some important
center of civilization and the news it receives through any channel will be flashed to all points of the globe. A cheap and
simple device, which might be carried in one's pocket, may then be set up somewhere on sea or land, and it will record the
world's news or such special messages as may be intended for it. Thus the entire earth will be converted into a huge brain, as it
were, capable of response in every one of its parts. Since a single plant of but one hundred horse-power can operate hundreds
of millions of instruments, the system will have a virtually infinite working capacity, and it must needs immensely facilitate
and cheapen the transmission of intelligence.
The first of these central plants would have been already completed had it not been for unforeseen delays which, fortunately,
have nothing to do with its purely technical features. But this loss of time, while vexatious, may, after all, prove to be a
blessing in disguise. The best design of which I know has been adopted, and the transmitter will emit a wave complex of a total
maximum activity of ten million horse-power, one per cent, of which is amply sufficient to "girdle the globe." This enormous
rate of energy delivery, approximately twice that of the combined falls of Niagara, is obtainable only by the use of certain
artifices, which I shall make known in due course.
For a large part of the work which I have done so far I am indebted to the noble generosity of Mr. J. Pierpont Morgan, which
was all the more welcome and stimulating, as it was extended at a time when those, who have since promised most, were the
greatest of doubters. I have also to thank my friend, Stanford White, for much unselfish and valuable assistance. This work is
now far advanced, and though the results may be tardy, they are sure to come.
Meanwhile, the transmission of energy on an industrial scale is not being neglected. The Canathan Niagara Power Company
have offered me a splendid inducement, and next to achieving success for the sake of the art, it will give me the greatest
satisfaction to make their concession financially profitable to them. In this first power plant, which I have been designing for a
long time, I propose to distribute ten thousand horse-power under a tension of one hundred million volts, which I am now able
to produce and handle with safety.
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Tesla's perfected system of wireless transmission with four tuned circuits
was described in U.S. Patent numbers 645,576 (March 20, 1900) and 649621
(May 15, 1900). The applications were filed on Sept. 2, 1897
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The experimental station at Colorado Springs showing the structure used to determine the rate
of incremental capacity with reference to the earth.
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Diagramatic illustrations of the hermetically enclosed mercury
break that is described in U.S. Patent No. 609,245 of August 16, 1898.
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This energy will be collected all over the globe preferably in small amounts, ranging from a fraction of
one to a few horse-power. One of its chief uses will be the illumination of isolated homes. It takes very
little power to light a dwelling with vacuum tubes operated by high-frequency currents and in each
instance a terminal a little above the roof will be sufficient. Another valuable application will be the
driving of clocks and other such apparatus. These clocks will be exceedingly simple, will require
absolutely no attention and will indicate rigorously correct time. The idea of impressing upon the earth
American time is fascinating and very likely to become popular. There are innumerable devices of all
kinds which are either now employed or can be supplied, and by operating them in this manner I may be
able to offer a great convenience to the whole world with a plant of no more than ten thousand horse-
power. The introduction of this system will give opportunities for invention and manufacture such as have
never presented themselves before.
Knowing the far-reaching importance of this first attempt and its effect upon future development, I shall
proceed slowly and carefully. Experience has taught me not to assign a term to enterprises the
consummation of which is not wholly dependent on my own abilities and exertions. But I am hopeful that
these great realizations are not far off, and I know that when this first work is completed they will follow
with mathematical certitude.
When the great truth accidentally revealed and experimentally confirmed is fully recognized, that this
planet, with all its appalling immensity, is to electric currents virtually no more than a small metal ball
and that by this fact many possibilities, each baffling imagination and of incalculable consequence, are
rendered absolutely sure of accomplishment; when the first plant is inaugurated and it is shown that a
telegraphic message, almost as secret and non-interferable as a thought, can be transmitted to any
terrestrial distance, the sound of the human voice, with all its intonations and inflections, faithfully and
instantly reproduced at any other point of the globe, the energy of a waterfall made available for sup-
plying light, heat or motive power, anywhere--on sea, or land, or high in the air--humanity will be like
an ant heap stirred up with a stick: See the excitement coming!
The original 1904 caption to this photo read: Tesla Central Power Plant, Transmitting
Tower, and Laboratory for "World Telegraphy," Wardenclyffe, Long Island.
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In a 1929 article on "World-Wide Transmission of Electrical Signals, Tesla explained his theory to
the general public. The article used the following diagrams to show the "Theory, Analogy, and
Realization" of the transmission of Electrical Signals world-wide.
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Above: Tesla's drawing of the earth and its atmospheric envelope drawn to scale from the
February, 1919 issue of Electrical Experimenter, which discussed Tesla's "Ether Space Wave
Theory." Below: Another drawing from 1929 demonstrating Tesla's Ether theory and how he
theorized he would recover the energy from electromagnetic Hertz waves as oscillatory energy.
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Tesla's X-Ray tube, part of his method for utilizing "radiant energy," which
operated from the top of a Tesla coil, providing a means to charge the "elevated
insulated body of capacitance" C, with armatures T-T'. "Whenever the circuit is
closed owing to the rotation of the terminal t', the stored energy is discharged..."
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Interior views of Tesla's experimental Colorado Springs tower, showing the cage
generatoring voltage and the banks of batteries.
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