The previous two books contain works that had already been published and had thus been accessible to the public. The most significant of Tesla's works had been selected and published in their integrity in the first book (Nikola Tesla: Lectures, Patents, Articles, Beograd, 1956) while the most important reviews of Tesla's works and the appreciation of their significance for world science are contained in the second book (Tribute to Tesla, Beograd, 1961).
Tesla's manuscript (written in English), that has up to now remained unpublished and unknown to the public, is appearing in this book for the first time. Nikola Tesla did not write his diary for the public, but exclusively for his personal use.
Obviously, he was writing it to have an insight into the course of his research and due to the exceptional extent of the experiments of his research in the isolated laboratory he had erected in 1899 on the slopes of the mountain Pikes Peak, he was probably writing it with the wish to leave behind some evidence in case of fire or destruction of his laboratory.
Tesla evidently did not intend to publish this diary and left it among his other notes and writings. It was not until the whole legacy of Nikola Tesla had been systematically examined and put in order in the Nikola Tesla Museum that the manuscript of this diary was discovered. Like all testimonies of this kind, the diary of Nikola Tesla has the value and fascination of a most genuine testimony because it reveals Tesla's ideas in an important period of his research. It reveals the extraordinary enthusiasm and fervor of his inexhaustible and strikingly exploring imagination.
In fact, this diary brings to light all that made Tesla different from all other researchers: his creative spirit which often bewildered, amazed and infuriated many of his contemporaries and even some well-informed scientists, to whom it seemed that Tesla's ideas belonged to the sphere of illusion rather than to the acknowledged course of science. Tesla thus shared the fate of all exceptionally great and far-sighted explorers.
In fact, when one carefully studies the entire work of Tesla one can see that his principal aim was very clear: to search for the inexhaustible possibilities of dominating the forces of nature and subordinating them to human purposes thus increasing immensely the power of man and mankind in order to live more humanly. All that Tesla had done was subordinated to this principal aim. All his experiments in Colorado Springs, dealt with in this--diary, had also been dedicated to this basic aim.
the extraordinary dimensions of his experiments, which would be
unusual even for present-day experimental work in this field, this
diary is not only a valuable historical testimony but also an
inexhaustible inspiration for
further research even when some mistakes are spotted. Tesla was so
ingenious and devoted to his indefatigable search for new knowledge
that he could permit his little errors to feed all kinds of
small-minded people who learned how to calculate well but could
never learn to seek for new ways of knowledge because they didn't
have a creative gift.
He worked on the practical development of his first ideas of 1891—1893 at such a rate that by 1897 he had already patented a system for wireless transmission of power and an apparatus utilizing this system. Shortly before this, during the ceremonial opening of the hydroelectric power plant on Niagara, at a time when the world was only just coming around to Tesla's polyphase system which for the first time in history enabled the transfer of electrical power over distance, he said:
Always true to the principle that ideas must be experimentally verified, Tesla set about building powerful high-frequency generators and making experiments in wireless power transmission. The Nikola Tesla Museum in Belgrade possesses a Tesla's own slide which confirms that the experiment described in the patent "System of transmission of electrical energy" was in fact carried out before the Examiner-in-Chief of the U.S. Patent Office.
For experimental verification of his method of wireless power transmission "by conduction through the intervening natural medium", on the global scale Tesla needed still higher voltages and more room (in the Houston Street laboratory he generated voltages of 2 to 4 MV using a high-frequency transformer with a coil diameter of 244 cm), he finally decided on Colorado Springs, a plateau about 2000 m above sea level, where he erected a shed large enough to house a high-frequency transformer with a coil diameter of 15 meters!
Tesla's arrival in Colorado Springs was reported in the press. According to the Philadelphia "Engineering Mechanics" Tesla arrived on the 18th of May 1899 (according to 68 he left to New York on 11th May 1899), with the intention of carrying out intensive research in wireless telegraphy and properties of the upper atmosphere. In his article "The transmission of electric energy without wires" (1904 1)
Tesla writes that he came to Colorado Springs with the following goals:
Tesla had some ten years of experience with high frequency AC behind him by the time he moved to Colorado .Springs. In 1889, on his return from Pittsburg where he had been working as a consultant to Westinghouse on the development of his polyphase system, he began work on the construction of an alternator for generating currents at much higher frequencies than those used in ordinary power distribution. In 1890 he filed applications for two patents2 for alternators working at over 10 kHz.
One of these patents was in conjunction
with a method for achieving quiet operation of arc lamps, but this
was in fact a first step towards a new application of alternating
currents, which soon became known as "Tesla currents". Tesla's
alternators were an important milestone in electrical engineering
and were the prototypes for alternators which were used some
quarter-century later for driving high-power radio transmitters, and
later on also for inductive heating.
This success was due in good measure to his convincing experiments too, which included a demonstration of rarefied gas luminescing in a tube not connected by wires to the source of power. This was the first experiment demonstrating wireless power transmission, and marked the birth of an idea to which Tesla was subsequently to devote a great part of his life. The necessary powerful electric field was created between the plates of a condenser connected across the secondary of a high-frequency transformer, whose was connected via a series condenser to a high-frequency alternator.
The system worked best when the primary
and secondary circuits were in resonance. Tesla also made use of the
resonant transformer with his spark oscillator, enabling easy and
efficient generation of high-frequency AC from a DC or low frequency
source. This oscillator was to play a key role in the development of HF engineering. Only a few years later it was to be found among the
apparatus of practically every physics laboratory, under the name of
the Tesla coil20.
Induction coil PS produces a high secondary voltage which charges condenser C until a spark occurs across air gap a. The discharge current flows through the air gap and the primary of the high-frequency induction coil P'. The discharge of the condenser in this case differs from the discharge through coil with ohmic resistance studied by Henry, already known by that time. In Tesla's oscillator the energy of the high-frequency oscillations in the primary circuit is gradually transferred circuit.
After energizing of the secondary circuit, the remaining
energy is returned to the primary, then back to the secondary, and
so on until losses reduce it sufficiently to interrupt spark across
a in the primary circuit. Then condenser C begins to recharge from
source G via induction coil (transformer) PS. Oberbeck published
a theoretical analysis of Tesla's oscillator in 1895.
Tesla also did a lot of work on improvements of the spark gap and
described several designs, some of which were subsequently
attributed to other authors(24). In describing the apparatus with
which he illustrated this lecture he explained several ways for
interrupting arcs with the aid of a powerful magnetic field; using
compressed air; multiple air gaps in series; single or multiple air
gaps with rotating surfaces.
According to Tesla's caption these diagrams are "Illustrating various ways of using high-frequency alternator in the first experiment at Grand Street Laboratory 1891—1892". It seems that Tesla made these to prove his priority in a patent suit. Only some of these diagrams have been published in, so that this is an important document throwing new light on an exceptionally fertile but relatively little known period of Tesla's work. It is, for example, clear from these diagrams that he introduced an HF transformer in the open antenna circuit.
Circuits like that in Fig. 3c—4 are to be found later in two patents
filed in 1897 on his apparatus and system for wireless
transmission of power (these patents refer to Tesla's disruptive
discharge oscillator as an alternative to the high-frequency
Tesla described here is often taken to be the foundation of radio
engineering, since it embodies principles ideas of fundamental
importance, viz.: the principle of adjusting for resonance to get
maximum sensitivity and selective reception, inductive link between
the driver and the tank circuit, an antenna circuit in which the
antenna appears as a capacitive load(71). He also correctly noted
the importance of the choice of the HF frequency and the advantages
of a continuous carrier for transmitting signals over great
While others principally developed
Hertz's apparatus with a spark-gap in the tank circuit (Lodge, Righi, Marconi, and others) and improved the receiver by
introducing a sensitive coherer (Branly, Lodge, Popov, Marconi, and
others), he set about
implementing his ideas of 1892—1893. How far he had got in verifying
his ideas for wireless
power transmission before coming to Colorado Springs may be seen
from patent No.
645576 and the diagram in Fig. 1c.
Figure 1c proves that Tesla did actually carry out an
of power transmission through rarefied gas before an official of the
Patent Office. From
the patent it may be seen that the pressure in the tube was between
120 and 150 mm Hg.
Since it was not intended for publication,
Tesla probably kept it as a way of recording his research results.
It could perhaps also have been a safety measure in case the
laboratory should get destroyed, an eventuality by no means unlikely
considering the dangerous experiments he was performing with
powerful discharges. Some days he made no entries, but usually
explained why at the beginning of the month.
This led to pessimistic conclusions about the possible range of radio stations, which were soon refuted by experiments using the aerial-earth system designed by Tesla in 1893. Tesla did not go along with the general opinion that without wires "electrical vibrations" could only propagate in straight lines, being convinced that the globe was a good conductor through which electric power could be transmitted. He also suggested that the "upper strata of the air are conducting" (1893), and "that air strata at very moderate altitudes, which are easily accessible, offer, to all experimental evidence, a perfect conducting path" (1900).
It is interesting to note that this mode of propagation
of radio waves was initially considered as something different from
other modes then to be forgotten until recent years. In the I950's
Schumann, Bremmer, Budden, Wait, Galejs and other authors, working
on the propagation of very low (3 to 30 kHz) and extremely low (1 to
3000 Hz) electromagnetic waves, founded their treatment on
essentially the same principles as Tesla.
He tried out various
modifications of the receiver with one or two coherers and special
pre-excitation circuits. He made measurements of the electromagnetic
radiations generated by natural electrical discharges, developed
radio measurement methods, and worked on the design of modulators,
shunt-fed antennas, etc.
By then many leading
scientists had been experimenting with "Tesla" currents but Tesla
himself was still in the vanguard with new and unexpected results.
When he finally finished his work in Colorado Springs he published
some photographs of the oscillator in a blaze of streamers causing
as much astonishment as had those from his famous lectures in the
USA, England and France in 1891—1893. The famous German scientist Slaby wrote that the apparatuses of other radio experimenters were
mere toys in comparison with Tesla's in Colorado Springs.
fireballs was not envisaged in his Colorado Springs work plan, but
belonged to the special experiments which, in his own words, "were
of an interest, purely scientific, at that time"*68*, which he
carried out when he could spare the time.
The article really did create a sensation, and was reprinted and cited many times. The style he uses in describing Colorado Springs research differs greatly from that of the diary.
Tesla wrote about his Colorado Springs work again in 1904. Some
interesting data is to be found in his replies before the United
States Patent Office in 1902, in connection with a patent rights
dispute between Tesla and Fessenden. This document includes
statements by Tesla's assistant Fritz Lowenstein and secretary
George Scherff. Tesla took Lowenstein on in New York in April 1899.
At the end of May that year he summoned him to Colorado Springs,
where Lowenstein remained until the end of September, when family
matters obliged him to return to Germany. Tesla was satisfied with
him as an assistant and asked him to return later, which he did,
again becoming Tesla's assistant in February 1902.
The experiments he wanted to perform Were not in fact carried out until the sixties of this century, when it was found that the Earth resonates at 8, 14 and 20 Hz. Tesla predicted that the resonances would be at 6, 18 and 30 Hz. His preoccupation with this great idea slowed down the construction of his overseas radio station, and when radio transmission across the Atlantic was finally achieved with a simpler apparatus, he had to admit that his plans included not only the transmission of signals over large distances but also an attempt to transmit power without wires.
Commenting on Tesla's undertaking, one of the world's leading experts in this field, Wait, has written:
In a letter to Morgan early in 1902 Tesla explained his research, in which he envisaged three "distinct steps to be made:
With the completion of my present
undertaking the first step will be made". For the experiments with
transmission of large power he envisaged the construction of a plant
at Niagara to generate about 100 million volts.
Today, when we have proof of the Earth's resonant modes (Schumann's resonances), and it is known that certain waves can propagate with very little attenuation, so little that standing waves can be set up in the Earth-ionosphere system, we can judge how right Tesla was when he said that the mechanism of electromagnetic wave propagation in "his system" was not the same as in Hertz's system with collimated radiation. Naturally, Tesla could not have known that the phenomena he was talking about would only become pronounced at very low frequencies, because it seems he was never able to carry out the experiments which he had so brilliantly planned, as early as 1893.
It is gratifying that after so many years Tesla's name is rightfully reappearing in papers dealing with the propagation of radio waves and the resonance of the Earth. In a recent book of a well known scientist (Jackson) it is stated that,
We believe that further studies of Tesla's writings will
reveal some interesting details of his ideas in this field.
section at the end of the book contains commentaries on the Diary
with explanatory notes, and a survey of his earlier work and that of
other researchers. For these commentaries reference was made to the
large body of literature and documents in the archives of the Nikola
Tesla Museum in Belgrade.