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I read that Tesla in his NYC workshop was experimenting with an oscillator attached to the building's steel framework to test resonance or something similar, and these oscillations were felt several blocks away.  Do you have any information on this?

On the occasion of his annual birthday celebration interview by the press on July 10, 1935 in his suite at the Hotel New Yorker, Tesla spoke about a method of transmitting mechanical energy with minimal loss over any terrestrial distance.  It could be used for the unerring location of underground mineral deposits using the principle of mechanical resonance.  At that time he recalled the minor earth trembler in lower Manhattan, that brought police and ambulances rushing to the scene of his Houston Street laboratory while an experiment was under way with his reciprocating electro-mechanical oscillator.  The device, that has come to be known as "the earthquake machine," was clamped to one of the building's structural I-beams.  Through precise adjustment of the oscillator's frequency, it had been brought in tune with the building's natural resonant frequency and that of the ground upon which it stood.

New York World-Telegram
July 11, 1935


Could Destroy Empire State Building with Five Pounds of Air Pressure, He Says

By Earl Sparling

. . . Tells of —Quake—

. . . he revealed that an earthquake which drew police and ambulances to the region of his laboratory at 48 E. Houston St. in 1887 or 1888 was the result of a little machine he was experimenting with at that time which —you could put in your overcoat pocket.—

The bewildered newspapermen pounced upon this as at least one thing they could understand and —the father of modern electricity— told what had happened as follows:

—I was experimenting with vibrations. I had one of my machines going and I wanted to see if I could get it in tune with the vibration of the building. I put it up notch after notch. There was a peculiar cracking sound.

—I asked my assistants where did the sound come from. They did not know. I put the machine up a few more notches. There was a louder cracking sound. I knew I was approaching the vibration of the steel building. I pushed the machine a little higher.

—Suddenly all the heavy machinery in the place was flying around. I grabbed a hammer and broke the machine. The building would have been down about our ears in another few minutes. Outside in the street there was pandemonium. The police and ambulances arrived. I told my assistants to say nothing. We told the police it must have been an earthquake. That's all they ever knew about it.—

Watch Out, Mr. Smith

Some shrewd reporter asked Dr. Tesla at this point what he would need to destroy the Empire State Building and the doctor replied:——Five pounds of air pressure. If I attached the proper oscillating machine on a girder that is all the force I would need, five pounds. Vibration will do anything. It would only be necessary to step up the vibrations of the machine to fit the natural vibration of the building and the building would come crashing down. That's why soldiers always break step crossing a bridge.—

His early experiments in vibration, he explained, led to his invention of his —Earth vibrating machine. Tall and thin and ascetic face, his eyes sunken but . . . . humorous under protruding brows, he was cagey about describing what his new machine is, although he believes it will be —the chief thing of my many inventions posterity will thank me for.—

The earthquake story, with some apparent literary embellishments, also appears in John O'Neill's biography of Tesla, Prodigal Genius. 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The idea made a strong appeal to Tesla; and in his discussion, after telling me of the experience here related, he further declared that he had so far developed his study of vibrations that he could establish a new science of —telegeodynamics— which would deal not only with the transmission of powerful impulses through the earth to distant points to produce effects of large magnitude—in addition, he could use the same principles to detect distant objects. . . .

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

—So powerful are the effects of the telegeodynamic oscillator,— said Tesla in reviewing the subject in the thirties, —that I could now go over to the Empire State Building and reduce it to a tangled mass of wreckage in a very short time. I could accomplish this result with utmost certainty and without any difficulty whatever. I would use a small mechanical vibrating device, an engine so small you could slip it in your pocket. I could attach it to any part of the building, start it in operation, allow it twelve to thirteen minutes to come to full resonance. The building would first respond with gentle tremors, and the vibrations would then become so powerful that the whole structure would go into resonant oscillations of such great amplitude and power that rivets in the steel beams would be loosened and sheared. The outer stone coating would be thrown off and then the skeleton steel structure would collapse in all its parts. It would take about 2.5 horsepower to drive the oscillator to produce this effect—

In the article Nikola Tesla, Dreamer (Allan L. Benson, World Today, Feb. 1912), an artist's illustration appears showing the entire earth cracking in half with the caption, Tesla claims that in a few weeks he could set the earth's crust into such a state of vibration that it would rise and fall hundreds of feet and practically destroy civilization. A continuation of this process would, he says, eventually split the earth in two.

Underground Seismic Exploration Using Telegeodynamics

Tesla's mechanical power transmission system was based upon his Reciprocating Engine invention, U.S. Patent No. 514,169, February 6, 1894.  He claimed that when fully developed the system would give prospectors a means for locating underground mineral deposits.  He called this discovery telegeodynamics whereby powerful acoustic impulses were transmitted through the earth to be picked up and amplified at distant locations.

It has been found that an acoustic impulse which is coupled into the ground will interact with the various types of underground structures which the propagating signal encounters. Furthermore, knowledge about the shape and to some degree the composition of these concealed structures can be developed using data from nearby instruments set in place to detect, amplify and record the reflected seismic waves after their passage through the intervening subsurface medium. The information obtained with such transmitting and receiving instruments, the signal experiencing reflection, refraction and diffraction as it passes between them, can be used to deduce the possible location of underground petroleum reserves and mineral deposits.

The two types of acoustic energy used to artificially produce seismic waves are impulsive and oscillating. The impulsive energy source, first used in 1919, is a large dynamite charge on the order of 50 pounds. The detonation of a specially prepared explosive charge creates a compression wave which travels outward in the shape of an expanding sphere. 

The frequency-stable Tesla telegeodynamic transmitter is an oscillating acoustic energy source.  According to his mechanical earth resonance hypothesis, when continuously operated, some of the energy contained within each transmitted pulse is reflected back to its point of origin.  Each successive pulse is carefully timed to precisely reinforce the action of those preceding it.  In this fashion, over an extended period of time a tremendous amount of acoustic energy, exceeding that which is available from a single dynamite charge, is impressed upon the earth. 

Seismic waves propagate by elastic deformation, which takes place through a series of alternating compressions and rarefactions of the transmitting medium.  But how elastic is the earth's crust wherein continuous acoustic waves are to be propagated?  And, is it sufficiently elastic to allow sustained oscillations to take place?  In a letter to Tesla dated April 19, 1918, George Scherff refers to a newspaper article mentioning effects produced on seismographs in this country by the German supergun and recalls remarks that seemed to bear out what Tesla said some time before about the transmission of mechanical energy.  It is also noted that ongoing sustained natural global oscillations on the order of one cycle per 110 minutes exist in the earth medium.  Furthermore, acoustic waves associated with some earthquakes are known to propagate throughout the entire planet.

Tesla's telegeodynamics receiver was of the same basic configuration as the transmitter, only much smaller in size.  He made statements regarding the location of underground ore deposits, saying that telegeodynamics could be used as a certain divining rod for locating ore deposits of any type under the surface of the earth.  Recent activities in geophysics bear upon these claims regarding direct detection.  While many ore-bearing structures can be imaged using acoustic means alone, the identification of specific ores or their associated minerals will almost certainly depend upon techniques that also detect non-acoustic responses to an acoustic wave, using instruments that measure various electrical and magnetic parameters.  Such responses would at least take the form of induced magnetic fields, telluric currents, and localized changes in earth conductivity.

Revised: 05/15/2008

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