Nikola Tesla's Lecture

Mr. Tesla's lecture on "Mechanical and Electrical Oscillators" was delivered in Assembly Hall at the southwest corner of the Agricultural Building at the World's Fair grounds on Friday evening as announced in the program. Every member of the congress with one or two exceptions was present and the greatest interest was manifested in the experiments that were shown.

It was twelve minutes after eight when Prof. Elisha Gray introduced Mr. Tesla to the audience in the following words: "I came down here tonight for the purpose of introducing to you a gentleman whose name needs no introduction as it is a household word with all electricians, but I wanted to do him the compliment of coming here as the official head of the World's International Congress of Electricians and to extend to him the compliment of an introduction for them as well as for myself. This compliment loses none of its force when I tell you that I have another official duty to perform tonight and it will be necessary for me to leave immediately, but if I should follow my inclinations I should stay, for no one wants to hear and see these experiments more than myself. I have the honor, ladies and gentlemen, of introducing to you Nikola Tesla. I wish to add one word, inasmuch as I have to leave; I am going to ask Dr. T. C. Mendenhall to do the honors for the rest of the evening."

Immediately the hearty applause subsided Mr. Tesla said: "Ladies and Gentlemen: We are told in a delightful anecdote how, many years ago, when science was still in its infancy, a man to whom the world is largely indebted for the discovery of a great truth was meditating in his garden when the idea came to him, and how on that occasion he was carried away by his enthusiasm. Be that an actual fact or not it is certain that the search for truth through the centuries that have elapsed has exercised an immense power on the imagination of man. It seems as though we are actual witnesses of the researches and experiments made by the discoverers and inventors of ages gone by, and that we are almost in a condition to know how they felt at the moment of sublime inspiration.

"I am sure in this audience there are many who have felt this most exquisite pleasure and whose presence here will forever fix the recollection of this evening upon my mind To feel this pleasure is accorded to but few; however, I can say myself that I have felt it and am still under the impression of the pleasure which the accomplishment of a few insignificant thoughts that have come to me and the speculation on the possibilities of their future development have caused. In these results I am, inventor like, quite taken up, and I hardly dare hope to be able to develop them as I wish, but I feel that I must explore them; and again I have doubted my ability to present them satisfactorily. Yet I am sure of the practicability of investigations in this manner from the few results I have so far obtained.

"I can best tell you what I have attempted if I comply with the scientific duty and tell you exactly the history of these inventions. It was at a time when I was strenuously endeavoring to solve a question or two which was considered insolvable, first, Was it possible to operate a motor without sliding contact, and second; was it possible to develop constant currents in a certain direction? I found the solution to the one problem and produced dynamos without commutators and that success emboldened me to go ahead and apply whatever of knowledge and experience I possessed to the solution of the other problem.

"On the occasion of my first visit to this country I stepped into the exposition at Philadelphia and I saw there a very thick copper washer provided with handles that visitors would move within a magnetic field. That day it occured to me that when the plate was moved slowly in the field there was experienced resistance, and that when the plate was suddenly pressed in there was a rebound as though it struck against something solid. After returning from the exposition the thought occurred to me that if I took a conductor and moved it into the field and then rapidly with. drew it, Icould in this way obtain whatever of electro-motive force there was. In the first place I was impressed with the analogy of this device to the induction coil, in which the same process takes place. When we impart current to the primary circuit we put lines of force slowly into the field and when we break the current we take the force swiftly away. I began to think of a mechanism which would be capable of fulfilling these conditions.

"During my work with induction coils and motors which succeeded I became familiar with currents of high frequency, and then I clearly realized the problem before me. I convinced myself that in alternating distributions we must induce currents of more thad one phase and that we must have a better organization and a perfected mechanism capable of rendering the current into steady oscillations before we could obtain the desired results. Here then I was confronted with this difficulty. I constructed small machines of the ordinary type which enabled me to investigate, but when I endeavored to construct machines with a greater number of alternations for higher frequency I found that I met insurmountable mechanical difficulties.

"And then the idea came up and I asked, how it would be if I took a very strong field and reciprocated very rapidly a conductor in that field, would I not have a similar machine and one which would not involve loss in the iron? And now I began to consider this matter very seriously and later I considered this question, knowing what has been done in the field of harmonic telegraphy and supposing that instead of the ordinary dynamo we take dynamos constructed like the pendulum of a clock and on a harmonic vibration principle, would we not then obtain alternating currents of a perfectly defined and absolutely constant period, which it is impossible to accomplish with an ordinary machine because it possesses so great inertia? And then again I thought like this, with such powerful machines there is a possibility of transmitting energy through the air and by means of this energy of transmitting messages. This, then, is one of the mainsprings which has driven me into this work."

Here by means of diagrams Mr. Tesla described the construction of the engine which he has invented for producing these absolutely constant oscillations and which is operated by compressed air under 100 pounds pressure and delivered at the rate of 40 cubic feet per minute. One of these engines having a diameter of about two inches and a half and of about that length operated a small motor and has a capacity of nearly one-half horse power. After this Mr. Tesla showed the operation of the larger engine having a piston and plunger weighing 20 pounds which was oscillated at the rate of 78 times a second, and stated that 5,000 or 10,000 oscillations per second could be as readily produced. The next experiment was made by attaching a horse shoe magnet having a wire about two feet in length inserted through it to show the vibration to the plunger of the engine. The engine was then set in motion, a current communicated to the magnet through wires attached to the nodes of the magnet wire. A copper disc revolving on an axis was then introduced by Mr. Tesla between the poles of the magnet while the same was being oscillated by the engine. The result of the experiment was that the copper disc began slowly to revolve, thus disproving the theory that there is no electro-magnetic force at work in the disc and that the force was simply one produced by induction as has been believed universally heretofore.

Mr. Tesla next attempted to show an experiment with what might be called a three coil generator, but the apparatus had been damaged in some way and refused to work. The next experiment was one with a large engine similar to that last described, having attached to the plunger of the oscillator a core of iron which played through four field magnets excited with a current at 5,000 volts from the Westinghouse plant. A current was generated by the apparatus, and was used to run a small registering motor, thus proving that generators can be constructed on the ideas evolved by Mr. Tesla in accordance with these more recent experiments, and having an absolutely constant current. It should be added that one of the claims made by Tesla for these oscillators is that the period will not be varied after the machine is started, whether the pressure be 10 pounds or 100 pounds, and that the electrical currents produced from small units will oscillate just as as the pendulum oscillates, and be unaffected by the circuit load or any imaginable condition. The oscillators are so constructed that they can be adjusted. so as to run with practically no noise, and with the entire absence of any pounding effect.