CHAPTER IV

ARTIFICIAL LIGHTNING MADE AND HARNESSED TO MAN'S USE

OUR FRIENDS INVESTIGATE NIKOLA TESLA'S INVENTION FOR THE WIRELESS TRANSMISSION OF POWER, BY WHICH HE HOPES TO ENCIRCLE THE EARTH WITH LIMITLESS ELECTRICAL POWER, MAKE OCEAN AND AIR TRAVEL ABSOLUTELY SAFE, AND REVOLUTIONIZE LAND TRAFFIC.

"How would you like to send a signal clear through the earth with your wireless outfit and get it back again on your receiving instrument as clear and strong as at first, just about the same way you hear the echo of your voice when it rebounds from a mountainside or a big building?" asked the scientist one day while his young friend was telling him about his amateur wireless experiments.

"I don't see how I could," answered the boy.

"No, of course you don't," said the boy's friend, "for it took Nikola Tesla, 'the wizard of electricity' almost a lifetime to work out the invention by which he could do that, but if you like we will go and see Doctor Tesla and ask him to tell us about his wonderful experiments.

"You see this is a series of inventions by Tesla, and wireless telegraphy is only a small part of it. You remember the other day you told me of having read about aeroplanes equipped with wireless. Just think, Tesla's invention will make it possible for airships to be propelled and operated all by electricity sent without wires. The whole broad plan is called the wireless transmission of power, and that simply means that electricity can be transmitted without wires for all the uses we now have for it, as well as for a number of entirely new and hitherto unknown devices."

The boy was delighted with the prospect of seeing the great scientist Tesla, about whom he had read so much, and began to ask his older friend a thousand questions about the man, his work and life.

It was a good many days before the whole thing had been talked over, and the boy understood the series of inventions, but we will follow through a part of our scientist's explanation and the visit to Tesla's laboratory and plant.

Although Tesla's plan is one of the most astounding ever proposed by science, it has been proved possible by experiments of such hair-raising nature that the inventor has been called a "daredevil" a "demon in electricity" and a "dreamer of dynamic dreams." In his experiments he has produced electrical currents of a voltage higher even than the bolts of lightning we see cleaving the sky during the worst thunderstorms. These currents he has harnessed to his own use and made them tell him the inmost secrets of the earth--in fact of the palpitation at the very core of the globe--the heartbeats of our sphere. He has given exhibitions in which he has caused currents of inconceivably high power to play about his head as if they were gentle summer breezes, and while working in the mountains of Colorado, he has brought forth electrical discharges which caused disturbances in the wireless telegraph apparatus in all parts of the globe.

In short, Nikola Tesla plans to make artificial lightning, and so harness it to the use of man, that it can be sent anywhere on or above the earth, without wires.

To scientists and electrical engineers, Tesla's plan offers a field for limitless study and discussion, but to the boy who is interested in electricity it offers one of the most fascinating subjects for reading and thinking in all the realm of science. Just reflect that with the wireless transmission of power, and the development of an art that Tesla calls "telautomatics," the navigators of wireless power-driven airships and ocean liners will know their exact speed, position, altitude, direction, the time of night or day, and whether there is anything in their path, all through the wireless "telautomatic" devices for registering such impressions.

Tesla declares that the terrible _Titanic_ disaster never would have occurred had his system been in effect last April, for he declares that the _Titanic's_ captain would have known of the iceberg he was approaching long enough in advance to slacken speed and get out of its way. Moreover, he declares that with the wireless transmission of power, the wireless telegraph becomes a very simple matter, and that immediately after the accident, had the ship struck an obstacle in spite of warnings, the captain could have been in wireless telephone communication with his offices in London and New York, and with all the ships that were on the seas in the vicinity of the ill-fated liner.

But making air and sea navigation safe, sure, and speedy, are only the first steps Tesla intends to take in the wireless transmission of power. After that he hopes to light the earth--to carry a beautiful soft bright light to ranchmen far out on the deserts, to miners in their cabins or deep in the earth, to farmers, and to sailors, as well as to people in their homes in the cities all over the world--Australia as well as the United States.

Wireless electrical power, according to Tesla, will be one of the greatest agencies in war, if there is any, but it first will be an argument for universal peace. "Fights," says the inventor, "whether between individuals or between nations arise from misunderstandings, and with the complete dissemination of intelligence, constant communication, and familiarity with the ideals of other nations, that international combativeness so dangerous to world peace, will disappear."

If Tesla's plan were carried out in full it would completely revolutionize the industries of the world, for all the power of Niagara or any other waterfall in the world could be sent without wires to turn the wheels of the industries in China or Australia, while the power of the Zambesi Falls in Africa could be transmitted to run trains, subways, elevateds, and all other forms of industry in the United States. There is practically no limit to the possibilities of the scheme, because through Tesla's invention, distance means nothing, and the power instead of losing force with distance as is the case when power is transmitted through wires, retains practically the same voltage as at the outset.

We will visit Doctor Tesla at his office and laboratory in the Metropolitan Tower in New York with the scientist and his young friend to see what kind of a man it is who has invented machines for creating and handling such tremendous voltages.

Tesla sits at a wide flat-topped desk in the centre of his sunny office surrounded by books, a few models of inventions, and a few pictures of some of his most remarkable electrical experiments. He is very tall and slight, with a mass of black hair thrown back from his intellectual forehead. His piercing gray eyes sparkle as he smiles in greeting, and his thin pointed face lights up with an expression of pleasure and kindness that cannot help but make the great electrician's visitors feel that he is a good friend. Although he was naturalized more than twenty years ago, and has been an American citizen ever since, his English still shows some slight traces of his foreign birth. He looks no more than forty-odd and he is as interested in everything that is going on in the world as a young boy, but he has passed his fiftieth year.

"For all that I am something of a boy still myself," says the inventor. "You see I could work for the present generation to make money. Of course that's all right, but I don't care what the present generation thinks of me. It is the growing generation--the boys of to-day that I want to work for, because they will live in an age when the world has advanced far enough in science to understand some of the deeper mysteries of electricity. The boys of to-day are the great scientists of to-morrow, and it is to them that I dedicate my greatest efforts."

All his life Tesla has been working with an eye to the future as well as to the present, and some of his inventions probably will be far better appreciated in twenty years than they are now, although to Tesla we owe our thanks for some of the most important electrical machinery in use at the present time.

As an inventor Tesla is best known as a pioneer in high tension currents. It was he who introduced to the world the great principle of the alternating current, as up to the time he carried out his experiments only the direct current was used. Indeed, more than four million horsepower of waterfalls are harnessed by Tesla's alternating current system. That is the same as forty millions of untiring men working without pay, consuming no food, shelter or raiment while labouring to provide for our wants. In these days of conservation, it is interesting to note that this electrical energy derived from water power saves a hundred million tons of coal every year. Our trolley roads, our subways, many of our electrified railroads, the incandescent lamps in our homes and offices, all use a system of power transmission of this man's invention.

As said before Tesla is a naturalized American citizen. He was born in Smiljan, Lika, on the Austro-Hungarian border, in 1857. He came by his scientific and inventive turn of mind naturally, for his father was an intellectual Greek clergyman, and his mother, Georgia Mandic, was an inventor herself as was her father before her. The boy attended the public schools of Lika and Croatia, where he was a leader among his playmates in sports where imagination and mechanical skill were required. There are marvellous tales of the ingenuity of Tesla while a schoolboy, but with all his play he was a serious-minded student, and went through the Polytechnic in Gratz and the University of Prague in Bohemia with honours. While in the Polytechnic, Tesla saw the defects of some of the machinery that was used in the laboratory, and made suggestions for its improvement.

After finishing college Tesla began his practical career in Budapest as an electrical engineer in 1881. His first invention followed soon after in the form of a telephone repeater. He continued in electrical engineering in Paris until 1884, when he came to the United States. His first employment in America was with The Edison Company at Orange, N. J., but in 1887 he went into business for himself as an electrical engineer. From that time on he has been an important figure in the scientific world. He has made many addresses before various gatherings of experts and has written numerous papers on scientific subjects for the magazines. Of course the bulk of his time has been given to his inventions and the necessary research therefor.

[Illustration: LIKE A BOLT OF LIGHTNING

The electrical discharge of this Tesla oscillator created flames 70 feet across, under the pressure of 12,000,000 volts and a current alternating 130,000 times per second.]

[Illustration: DR. NIKOLA TESLA

Wizard of electricity, and inventor of the wireless transmission of power.]

[Illustration: DOCTOR TESLA'S FIRST POWER PLANT

From this oscillator Doctor Tesla sends out the electrical waves with which he hopes to revolutionize industry.]

Throughout his life Tesla has been more interested in the adventurous and scientific side of electricity than the commercial side, and all of his inventions smack of the marvellous. To name all his inventions would be almost like giving a list of the machines and devices that mark man's progress in the use of electricity. His invention for the alternating current dynamo, for instance, brought forth an entirely new principle, while his rotating magnetic field made possible the transmission of alternating currents from large power plants over great distances and is very extensively used to-day. High power dynamos, transformers, induction coils, oscillators, and various kinds of electric lamps all came in for his attention.

He became one of the foremost authorities on high tension currents and in 1889 invented a system of electrical conversion and distribution by oscillatory discharges which was a step toward his great goal, the wireless transmission of power. He was very near the prize when in 1893 he announced a system of wireless transmission of intelligence. His studies continued and finally, in 1897, he announced his famous high potential transmitter by which he claimed to be able to send power through the earth without wires. The art of telautomatics announced in 1899 was really a part of Tesla's invention for the wireless transmission of power, for the plan was to control such objects, for instance, as airships or boats, from a distance by electricity transmitted without wires.

Through that marvellous invention the boat or aeroplane dispatcher, sitting before a complex little wireless dispatching board could send his craft, at any speed, at any height, in perfect safety, and with exact precision to the place or port he desired it to go. It would not be necessary for the dispatcher ever to see the craft he was directing, for his instruments would show him everything in regard to its speed, direction, and location; nor yet would it be necessary for a craft to have a crew aboard, for all the operations in connection with sending it from one place to another would be controlled perfectly by telautomatics.

Such are the almost inconceivable inventions of Nikola Tesla. "Sometimes they call me a dreamer," says Tesla, "because I do not capitalize these inventions, start in manufacturing and make a big fortune. That is not what I care to do. I want to go further in this great mystery of wireless power, and if I am busy making money I cannot devote my best abilities to inventions that will be in use when the next generation is grown."

But let us try to fathom the mysteries of Tesla's scheme for the transmission of electric energy without wires. In the first place we must not try to think of it as being on the same basis as the radio, or Hertzian wireless telegraph, for, although the modern developments of the wireless telegraph take into consideration the central theory of Tesla's invention, they are not at all the same in their practical working.

Tesla's theory is based entirely on his discovery of what he calls stationary electrical earth waves which he sets in motion with his high potential magnifying transmitter, an electrical apparatus of tremendous power.

First, let us remember the three essential departments of Tesla's idea for world telegraphy, world telephony, and world transmission of power for commercial purposes.

Assuming that the power is created by Niagara or some other great waterfall--"white coal" as it is picturesquely called by many engineers--the first necessities are a transformer and a transmitter that will send the electrical energy, thus gathered, into the earth and air. The next necessity is a receiving instrument that will record the impulse, whether it be a voice, a telegraph click, or several million volts for driving factory wheels or lighting houses. Lastly, it is necessary to tune the currents so that millions of different impulses can be sent without causing confusion between them. In other words, there must be departments for sending, receiving and "individualizing."

To ask Doctor Tesla to tell us the whole story of this invention would be to ask him to tell us in detail the whole history of his life work--and that would take several volumes, for he is one of those men who have worked incessantly, day and night, sacrificing himself and overcoming his natural desire for leisure and amusement. It all started, Tesla explains, when he was a very small boy. He was troubled at that time with a strange habit. Whenever any one would mention a thing to him, a vision of the object immediately would come before his eyes. He declares that this was very troublesome, and that as he grew older he tried to overcome it, thinking it some strange malady. With an effort he learned how to banish the images by putting them from his mind. On inquiring into the cause of the visions, the young scientist's penetrating brain brought him to the conclusion that every time he saw a vision, some time previous he had seen something to remind him of the object. The tracing back of the cause of his vision so frequently caused it to become a mental habit, and he declares that for many years he has done it automatically, and that he has been able to trace the cause of nearly every impression, even including his dreams. Reflecting on these things, as a mature scientist, Tesla came to the conclusion that he was an automaton, responding automatically to impressions registered on his senses from the outside.

"Why couldn't I make a mechanical automaton that would represent me in every way, except thought?" he asked himself. The answer to the question which came only after years of study and experiment was the art of "telautomatics," which Tesla declares can be developed just as soon as the wireless transmission of power is an accomplished fact.

In the course of his research into the realm of high tension currents Tesla reached the stage where it was no longer safe nor convenient to experiment in the centres of population. Moreover, he desired to make a study of the action of lightning. Colorado, with its vast stretches of uninhabited plains and mountains, offered an ideal place for his laboratory, particularly because the high, dry climate of that state brings forth some of the worst electrical storms seen in the United States. Consequently, in the spring of 1899, Tesla built an experiment station on the plateau that extends from the front range of the Rocky Mountains to Colorado Springs, and began the experiments through which the secret with which he hopes to revolutionize the communication and transportation systems of the world, was revealed to him.

Besides his high power alternating current dynamo, Tesla set up an electrical oscillator with which he hoped to send out electrical waves, through the earth and air, that would prove to him the possibility of an extensive system of wireless communication, and telautomatic, or wireless control of airships, projectiles, steamships, etc. In his early experiments he used the oscillator at low tension, but as his success became more marked he increased the tension, until the oscillator was giving twelve million volts, and the current was alternating a hundred thousand times a second.

In regard to these high tension experiments in Colorado and elsewhere, Doctor Tesla said, "I have produced electrical oscillations which were of such intensity that when circulating through my arms and chest they have melted wires which have joined my hands, and still I have felt no inconvenience. I have energized, with such oscillations, a loop of heavy copper wire so powerfully that masses of metal placed within the loop were heated to a high temperature and melted, often with the violence of an explosion. And yet, into this space in which this terribly destructive turmoil was going on I have repeatedly thrust my head without feeling anything or experiencing injurious after effects."

Among the earlier experiments, which in themselves were wonderful enough, were the transmission of an electrical current through one wire without return, to light several incandescent lamps. Advancing further along the trail of wireless transmission of power, Tesla lighted the lamps without any wire connection between them and his transmitter.

The oscillator, though simple in its construction, is one of the most wonderful of all electrical devices. "You see," said Doctor Tesla, "all that is necessary is a high power alternating dynamo which generates a tremendous alternating current. For our oscillator proper, we make a few turns of a stout cable around a cylindrical or drum-shaped form, and connect its two ends with the source of electrical energy. Then, inside the big cable, or primary coil, we wind a lighter wire in spiral form. One end of the secondary coil is sunk into the ground and connected with a plate, and the other is erected in the air. When the current is turned on, our oscillator sends these electrical impulses into the earth and air--or, as the scientists say, into the natural media. These oscillations create electrical waves and affect any device that is tuned to them--but (and this is very important) no device that is not tuned to them."

Continuing the explanation of his high tension experiments, Tesla tells us that the awe-inspiring electrical display, of which there is a picture on page 136, was made by his oscillator which created an alternate movement of electricity from the earth into a hollow metal reservoir and back at a speed of 100,000 alternations a second. The reservoir is already filled to overflowing with electricity and as the current is sent back to it at each alternation the terrific force makes it burst forth with a deafening roar, as great as the heaviest lightning detonation. The electric flames shoot out in every direction searching for something on which they may alight, just as lightning sent from the clouds searches for a conductor upon which it may alight and escape into the earth. The induction coils in the picture are tuned to these tremendous electrical explosions, and the flames shoot direct to them, a distance of 22 feet.

The flames shooting from the coil of the oscillator pictured on page 164 were nearly 70 feet across, represented twelve million volts of electricity, and a current alternating 130,000 times a second. These hair-raising experiments created such electrical disturbances that it was possible to draw great sparks more than an inch long, from water plugs over 300 feet from the laboratory. One of the most marvellous things about these experiments is that any human being could remain in the vicinity. The absolute safety of these discharges when properly harnessed is well illustrated in the picture shown there as the man seen amidst the flames felt no ill effects from his experience, simply because this power was so thoroughly harnessed by the wizard Tesla, that it could go only to the device tuned to receive it. Every boy is familiar with stories of lightning striking one person, but yet leaving another person right next to him unharmed. Such is the action of Tesla's high tension currents, only he directs them by induction just as he wants them to go.

"But this is just like lightning!" exclaimed the boy.

"So it is," calmly answered Doctor Tesla with a smile. "I have often produced electrical oscillations even greater than the energy of lightning discharges."

These experiments were marvellous enough, but they were surpassed in a short time by his famous discovery of July 3, 1899, which showed him that he could send his wireless waves to the opposite side of the earth just as well as a hundred feet away.

This revelation, as the scientist calls it, came about through his study of lightning. The scientist had set up in his Colorado laboratory many delicate electrical instruments to register various different electrical effects. Tesla noticed, however, that strangely enough his instruments were just as violently affected by distant electrical storms as by nearby disturbances.

"One night when meditating over these facts," said Tesla, "I was suddenly staggered by a thought. The same thing had presented itself to me years ago; but I had then dismissed it as impossible. And that night when it recurred to me I banished it again. Nevertheless, my instinct was aroused, and somehow I felt that I was nearing a great revelation.

"As you know, it was on the third of July that I obtained the first definite evidence of a truth of overwhelming importance for the advancement of humanity. A dense mass of strongly charged clouds gathered in the west, and toward 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 at regular intervals of time. My observations were now greatly facilitated and rendered more accurate by the records already made. I was able to handle my instruments quickly, and 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. Sure enough, in a little while the indications again began, grew stronger, gradually decreased, and ceased once more. Many times, in regularly recurring intervals, the same actions were repeated, until the storm, as evident from simple computations, with nearly constant speed had retreated to a distance of about two hundred miles. Nor did these strange actions stop then, but continued to manifest themselves with undiminished force.

"When I made this discovery I was utterly astounded. I could not believe what I had seen was really true. It was too great a revelation of Nature to accept immediately and unhesitatingly."

What Tesla had discovered, and soon announced to the scientific world, was the existence of stationary terrestrial waves of electricity, and its meaning was that an impulse sent into the earth was carried on these waves to the other side of the earth and rebounded without any loss of power. He had, in fact, discovered and turned to man's use the very heartbeats of our earth.

"Whatever electricity may be," he continued, "it is a fact that it acts like a fluid, and in this connection, we may consider the earth as a great hollow ball filled with electricity." He goes on to explain that when an impulse is sent into this ball of electricity it proceeds to the opposite wall of the earth in waves and, finding no outlet it returns to the place it started, but in a series of waves exactly the opposite of the outgoing ones, so that the two cross and diverge at regular intervals as indicated in the diagram.

[Illustration:

A--Oscillator

B--Opposite side of earth

C--Waves in nodal and ventral intervals.]

As Tesla put it, "The outgoing and returning currents clash and form nodes and loops similar to those observable on a vibrating cord." Tesla figured from these experiments that the waves varied from 25 to 70 kilometres from node to node, that they could be sent to any part of the globe, and that they could be sent in varying lengths up to the extreme diameter of the earth.

In order to prove his discovery Tesla sent an impulse into the earth, and received it back, on his delicate instrument, in a few seconds. "It is like an echo," he explained. "When you shout and in a few seconds hear your voice coming back, you do not think it is another voice but know immediately that it is simply your own vocal vibrations reflected by the house, mountainside, or what not. It is just the same with an electrical vibration. The stationary terrestrial wave goes through the earth, reaches the other side and, finding no outlet, is reflected without any loss of power. Indeed, in some cases it is returned with greater power than at first."

"Then in your system the wireless electrical current passes through the earth, and not through the air," interrupted the scientist.

"No," he answered, "it passes through both. It is difficult to understand the big things about electricity, but just think of the earth as a great ball filled with electricity, as I said before. Think of the tower of the oscillator as a tube, and of the great mushroom-shaped top of the plant as another ball. Now from our great alternating current dynamo we first fill the ball at the top of the oscillator with electricity, and then we make a motion that corresponds to squeezing it. What happens? Just what happens when you have two rubber balls connected with a tube. You squeeze one of them, and push the air, or water, into the other ball. In that way we push the electricity into the earth, but it comes back to us on the stationary waves, from the opposite side, and when it does we are ready to give it another mighty push with another tremendous squeeze from our dynamo. When this is going on the top of the oscillator is gathering electricity from the air all the time and sending it out to be used wherever there is a receiver properly tuned to receive these rates of vibration."

"But," again asked our friend, "isn't there a great deal of valuable electrical power wasted in that way?"

"No, there is very little waste," answered the electrician, "for this reason: If, for instance, our oscillator can generate a hundred thousand or a million, or any other number of volts, and we only wish to use it for some small purpose on the other side of the earth, the receiver at the antipodes takes as much power as is needed, and the rest remains unused and our oscillator can be run at reduced capacity."

Thus, according to Tesla's plan, the electrical energy will be sent into the earth and air by the high potential magnifying transmitter or oscillator, the stationary electrical waves carry it through the earth and the receiving instrument on the other side of the world collects the energy to put it to a thousand and one purposes of mankind. And do not forget that the oscillator and the receiving instrument are so tuned to each other that there is no danger, according to Tesla's scheme, of different oscillators and receivers getting mixed up.

Before Tesla had discovered the stationary electrical waves he had gone deep into the mystery of the "individualization" of electrical impulses, and as a result advanced plans for sending a number of messages over one wire without their interfering with each other. This study was continued with even greater energy, after he had taken the first steps toward the realization of his world telegraphy and world telephony without wires. In wireless telegraphy as we know its practice to-day, one of the serious drawbacks is the interference of other operators, both amateur and professional, with important messages. Tesla holds that the simple tuning of instruments to one another as is done nowadays would not be sufficient, when there were millions of currents passing through and around the earth. For instance, he says that an instrument tuned to a single rate of vibrations would be very apt to come into contact with another instrument sending at the same rate. Of course the confusion so familiar in modern radio-telegraphy would result. Moreover, it makes it difficult to send messages that cannot be intercepted and read by every wireless operator in hearing. "This can be avoided," continues the inventor, "by combining different tones or rates of vibration. In actual practice it is found that by combining only two tones, a degree of privacy sufficient for most purposes is attained. When three vibrations are combined it is extremely difficult even for a skilled expert to read or disturb signals not intended for him. It is vain to undertake to 'cut in on' a series of wireless impulses made up of four different rates of vibration. The probability of getting the secret of the combination is as slight as of your solving the number combination on the door of a safe. From experiments I have concluded that this individualization will allow the transmission of several million different messages. It is interesting when you think that one world telegraphy plant would have a greater capacity than all the ocean cables combined."

In regard to the amount of power to be transmitted, Tesla points out that an impulse of low voltage, or low horsepower, will carry to the other side of the earth without any loss of power, just as easily as a high voltage current. "A wire," says Tesla, "offers certain resistance to an electrical current causing some loss, but not so when it is sent through the natural media. The earth is a conducting body of such enormous dimensions that there is virtually no loss, so that distance means nothing. To the average intelligence this will appear incomprehensible. We are continuously confronted with limitations, and those truths which are contradicted by our senses are the hardest to grasp. For example, one of the most difficult tasks was to satisfy the human mind that the earth rotated round the sun; for to the eye it seemed just the opposite."

Tesla further pointed out that five-hundred miles is about the farthest that high power can be transmitted by wires with complete success, but that without wires, by his system, power can be transmitted, as we have seen, to any part of the globe or the atmosphere about it.

The plan for a world-wide system of wireless telegraphs and telephones differs considerably from the original idea laid down by scientists for radio or Hertzian wireless telegraphy. Originally Guglielmo Marconi, who first successfully telegraphed without wires, and whose system is well known all over the world, planned to send his electrical impulses through the ether, in the form of Hertzian rays, but later the method was amended. The theory advanced was that since everything is afloat in the colourless, intangible something called ether (not the drug used as an anæsthetic), and that since waves of light, heat, and electricity travel through ether, it would be possible to send electrical impulses through the ether in the earth and air, just as well as through the ether in a copper wire. In his early experiments Marconi used the light rays or waves named after their discoverer, Hertz, but these were found to be very limited, so electrical vibrations of a higher intensity were substituted, as we shall see in a later chapter.

"From the very first," declared Tesla, "my system has been based on a different principle, as you can see from what I have told you. For instance, my invention takes no consideration of light rays in any visible or invisible form (and Hertzian rays are invisible light), which can only travel in a straight line. Hence, you can see that they could not be used except as far as could be seen. In other words, they only could be used as far as the horizon, for just as soon as the curve of the earth's surface took the receiving instrument below the level of the Hertzian waves they became ineffective. You see the difference is that my system is based on the stationary earth waves, along which the electrical currents can pass to any distance irrespective of horizon, or matter."

A simple explanation will serve to show the principle of Tesla's theory of wireless telegraphy and telephony. We can easily think of a reservoir with two openings in the cover filled with some fluid. In each of these openings is a piston and above each piston is a tuning fork. The two tuning forks must be of exactly the same tone or the experiment will not work. We strike one of the pistons with the tuning fork, and continue to strike it until the fork sets up vibrations. The vibrations pass through the air, and also communicate vibrations to the piston, which in turn passes the vibrations on to the fluid in the reservoir. These vibrations naturally continue through the reservoir, as waves, just the same as when we throw a pebble into a calm pond and watch the waves radiate out in every direction. The water does not advance, but merely moves up and down. The waves, however, advance. So with the waves set up by the tuning fork, and they set up an oscillation of the piston at the other side, agitating the tuning fork in unison with the sound vibrations coming through the air.

It is just the same, declares Tesla, with two of his oscillators set up on the earth's surface and tapping the great sea of electricity, which he says is in the earth. The oscillators correspond to the tuning forks, the reservoir to the earth, and the fluid in the reservoir to the electrical currents with which he says the interior of the earth is alive. Exactly attuned, Tesla says, the vibrations set up by the sender will be communicated to the receiver through the earth and through the air.

"Now, with the development of the world system," continued Tesla, "we shall be able to telephone without wires just as well as telegraph, and to any part of the world just as easily as we now talk to a friend in an adjoining house over the modern wire circuits."

Before going with Doctor Tesla to his great plant out on Long Island to see how he is carrying on these tremendous theories of his, the boy asked him a few more questions about them, for it is a big and intricate question.

"What application will you first make of the wireless transmission of power?"

"My first concern," replied the magician of electricity, "will be to make air and water navigation safe. We have plenty of demonstrations of the value of the wireless telegraph in saving human lives when ships are in danger, in the _Republic_ and _Titanic_ disasters. But also we know that the wireless can be greatly improved upon. With a perfect system of communication, both by wireless telegraph and telephone, consider what it would mean to the navigators of air and ocean craft.

"By the art of telautomatics, which is a part of the broad scheme for the wireless transmission of power, many of the worst dangers of air and water navigation will be avoided, which is right in line with the modern tendency of preventing trouble rather than waiting for it to happen before remedying it." He then went on to enumerate the various telautomatic devices that will be carried by ocean liners and airships of the future, as mentioned in the early part of this chapter.

"Just for instance, how could telautomatics have saved the _Titanic_?" the inventor was asked.

"You understand, of course," answered Tesla, "that the devices I propose would be of almost inconceivable sensitiveness. They would be the centre of electrical waves, and, as soon as the iceberg got into the path of these waves from the wireless transmission plant to the ship, it would cause the electricity to register an impression of danger ahead. Of course mariners would become so expert in the reading of these danger signals that they could tell the meaning of each one, and alter their course or reverse their engines according to the needs of the case."

"How much have you accomplished in telautomatics at this time?"

"I have made a little submarine boat that will answer to every necessary impulse. The boat contained its own motive power in a storage battery and gear for propulsion, steering sidewise, or upward or downward, and all other accessories necessary for its operation. All of these were worked from a distance by wireless impulses, sent by an oscillator to the circuit in the boat through which magnets and other devices operated the interior mechanism.

"This proved to me the possibility of a high development of telautomatics. When my system is complete, a crewless ship may be sent from any port in the world to any other port propelled by wireless energy from a power plant anywhere on the face of the earth, and controlled absolutely by telautomatics."

Tesla's plan for aerial navigation is even more startling than that for crewless ocean liners. He thinks that the airships of the future will be propelled by wireless power and that they will have, neither planes nor other supporting surfaces, such as we are so familiar with nowadays. Neither will they be supported by gas bags like balloons and dirigibles. The inventor thinks they will be compact and just as airworthy as ocean liners are seaworthy. They will be tightly enclosed, so that the terrific rush of air through the high altitudes will not strangle the passengers and crew. He sees no reason why the airships of the future should not travel at a rate of several hundred miles an hour, so that you could leave San Francisco in the morning and be in New York in time for a six o'clock dinner, and the theatre, or cross the Atlantic in a night.

"How will these airships be propelled?" the boy asked.

"By engines driven with power supplied by our great oscillator wherever we care to erect it. These engines will work with such incredible force that they will make of the air above them a veritable rope to sustain them at any desired altitude, while they will make of the air in front of them a rope to pull them forward at a high rate of speed." Tesla continues to say that these ships can be made just as large as it is practicable to make their landing stages, or small enough for one or two passengers.

In the waterfalls of the United States alone, he pointed out, there are twenty-five hundred million horsepower of electrical energy. Niagara Falls could supply more than one fifth of all the power now used in this country, he says. Moreover, none of the great sites, such as those in the far Northwest, are developed to their highest state, because of the difficulty in transmitting the power over long distances to where it is used.

"It must be borne in mind," said Tesla, "that electrical energy obtained by harnessing a waterfall is probably fifty times more effective than fuel energy. Since this is the most perfect way of rendering the sun's energy available the direction of the future material development of man is clearly indicated. He will live on 'white coal.'"

"Doctor Tesla, can you tell us, please, just how far you have developed this invention for the wireless transmission of power?"

"Well," answered the electrical inventor, "the best way to tell you is to show you what has been done so far." In order to see Tesla's great plant we must follow the scientist and his boy friend out to Bay Shore, L. I., where, overlooking Long Island Sound, we see a great mushroom-shaped steel network tower surmounting a low building--the first of Tesla's many proposed high potential magnifying transmitters.

"So far," said Tesla of his power plant where the first attempts at wireless transmission are being made, "only about three million horsepower has been harnessed by my system of alternating current transmission. This is little, but it corresponds nevertheless to adding to the world's population sixty million indefatigable laborers, working virtually without food or pay."

As the boy approached the power plant he was impressed by the great size of the tower and its circular top, as shown in the photograph. It is this circular top, with its conductive apparatus, that gathers the electricity from the air and from the dynamo, and sends it forth in great waves both through the air and through the earth. The tower is 185 feet high, from the ground to the top, and from the ground to the edge of the cupola it is 153 feet. The diameter of the cupola floor is 65 feet. The cupola can be reached by both a staircase and an elevator, but it would hardly be healthy for any one to be within the network of electrical conductors when the plant was working. Inside the building are the high power alternating dynamos and underneath it extends the ground wire from the cupola, through which the electricity is pumped into the ground in great spurts at the rate of more than a hundred thousand spurts a second. At this plant Tesla plans to gather and concentrate millions of horsepower of electrical energy and then, in the ways we have seen, send it out to be used in a thousand different ways.

"This is merely an experiment," declared Tesla. "We can telegraph and carry on other such operations as require only a small amount of power from here, but it is nothing compared to the great power plants we will erect in the future."

"Is it necessary," asked the boy, "to have your power plant erected near the waterfall, or other means of producing the electricity?"

"No, it is not. This plant, for instance, can be made a great receiving station for electric power from all the great hydro-electric sites, and from it we hope to be able to send out electrical waves that will run our ships, airships, trains and street cars, carry our voices, light our houses, and turn the wheels of our factories. It is better, however, to have the plants located close to the seats of power, and to have a greater number of plants."

"How much horsepower did you say this plant would send out?"

"Only a mere trifle of three million horsepower, but of course this is only an experiment. To be done properly the thing must be done on a large scale, and the time will come--not necessarily remote--when we will be carrying on the whole programe embraced by the wireless transmission of power. The cost of wireless power I estimate would be about one sixteenth of that of the present system."

"When you are sending such tremendous voltages won't it be very dangerous to be anywhere in the vicinity of a plant, much less anywhere that the electricity might be brought from the earth?"

"No, for the power is so well harnessed that we can send it just where we want it and nowhere else. Of course, on the other hand, if we wanted to make trouble with this well-harnessed lightning we could make a terrible disturbance in the earth and on the surface of the earth."

"What about lightning?"

"That is one of the things we had to guard against right from the very first, and I can tell you that lightning will not bother us a bit, although I cannot give you the details of our method of avoiding it.

"When we are using the plant at night, however, there will be a display far more beautiful than lightning, all about the cupola in the form of a great halo of electric light visible for miles around."

Before we leave this fascinating subject of the wireless transmission of power let us ask Doctor Tesla about the effect of his invention on war.

"The wireless transmission of power will first be a big factor in promoting world peace, as I said before, because through the great improvement in communication it will lead to a better understanding between nations and break down many of the old prejudices that have lived for so many thousands of years. It will facilitate travel and commerce so that a citizen of the United States will find it as simple and cheap to travel abroad as he now finds it to travel in the neighbouring state. His commercial interests also will spread to foreign countries, and the nations will be so linked with one another socially and commercially that war will be out of the question.

"However, in case war should break out between the nations it will be a conflict of such gigantic proportions, and carried on with such tremendous death-dealing machines, that it will surpass our wildest dreams.

"For one thing, the new art of controlling electrically the movements and operations of individualized automata at a distance without wires will soon enable any country to render its coast impregnable against all naval attacks.

"I have invented a number of improvements of this plan, making it possible to direct a telautomaton torpedo, submersible at will, from a distance much greater than the range of the largest gun, with unerring precision, upon the object to be destroyed. What is still more surprising, the operator will not need to see the infernal engine or even know its location, and the enemy will be unable to interfere, in the slightest, with its movements by any electrical means. One of these devil-telautomata will soon be constructed, and I shall bring it to the attention of governments. The development of this art must unavoidably arrest the construction of expensive battleships as well as land fortifications, and revolutionize the means and methods of warfare. The distance at which it can strike, and the destructive power of such a quasi-intelligent machine being for all practical purposes unlimited, the gun, the armour of the battleship, and the wall of the fortress, lose their import and significance. One can prophesy with a Daniel's confidence that skilled electricians will settle the battles of the near future, if battles we must have.

"The future of wireless power development," explained the inventor, "may render it folly for any nation to have afloat a vessel of war. The secret of another nation's scheme of selectivity or combination of vibrations might be disclosed to the enemy, when the guns of their own vessels might be turned against sister ships and a whole fleet destroyed by shells from their own guns, or their magazines might be exploded by the enemy at will. However, should there be battleships in the wireless future, they will be crewless. They will be manoeuvred, their guns will be loaded, aimed, and fired, and their torpedoes discharged with unerring accuracy, by the director of naval warfare seated before a telautomatic switch-board on land.

"The time will come, as a result of my discovery," says Tesla, "when one nation may destroy another in time of war through this wireless force: great tongues of electric flame made to burst from the earth of the enemy's country might destroy not only the people and the cities, but the land itself. I realize that this is indeed a dangerous thing to advocate. At first thought it might mean the annihilation of the nations of the world by evilly disposed individuals. The public might at first look upon the perfection of such an invention as a calamity. We say that all inventions assist the criminal in his work. To-day the safe burglar despises the use of dynamite, turning to electrical contrivances to cut the lock from a safe. It is fortunate for the world, therefore, that 90 per cent. of its people are good, and that only 10 per cent. are evilly disposed: otherwise all invention might be turned more greatly to evil than to good."