So great was the interest and enthusiasm with which Mr. Tesla’s first lecture and experiments were received at the Royal Institution that he complied with the urgent request to repeat the same, and at the close of the second meeting Lord Rayleigh arose and spoke as follows: Sir Frederick Bramwell, ladles and gentlemen — Although it is not our custom here to follow the lecture with remarks from anyone else, I think you will agree with me that this is no ordinary occasion. At the request of the managers of the institution, and for the delectation of its members, Mr. Tesla consented to repeat the labors of last night, labors which, though small to him, would have completely exhausted anyone else.
I wish our great electrician, whose name appeared before us in letters of fire, in one of Mr. Tesla’s experiments, were here to propose this motion. There is only one respect in which I have any qualification to speak, and that is that I have made attempts myself to experiment with currents of a high degree of frequency. I was tolerably satisfied when I had a discharge rate of 2,000 per second, but we have had to-night ten or twenty thousand per second. My apparatus was on a very small scale indeed. Mr. Tesla has taken us into some of the dark — metaphorically dark — places in nature. These fields have been but little trodden. Mr. Crookes and Mr. Tesla alone have had the entree. In what has been put before us to-night, there has been matter which will afford food for intellectual contemplation for a long time to come. I think, at the same time, it will be obvious to you that Mr. Tesla has not worked blindly or at random, but has been guided by the proper use of a scientific imagination. Without the use of such a guide, we can scarcely hope to do anything of real service. I do not think there is anything I need add; it does not require any great capacity to see that Mr. Tesla has the genius of a discoverer, and we may look forward to a long career of discovery for him. His labors will be followed with admiration by all men of science of England, and especially by those in this institution to whom he has done the favor of lecturing to-night. I thank Mr. Tesla for his lecture.
Sir Frederick Bramwell: Ladies and gentlemen — I believe it is usual to second the vote of thanks. I, for one, should be very glad for Lord Rayleigh to put the motion to you. It is the duty of myself, however, to second this vote, which I do most heartily. Our treasurer is not here to-night; he foresees, as the result of the lecture, that the whole of our apparatus, in this line of study, is antiquated, and we shall have to begin afresh. This has evidently been too much for our treasurer, and he has consequently stayed away. In my own province of mechanical engineering, there was a time when we were content to have boilers which would be ridiculed now; and turning from mechanical engineering to electrical science, we have seen to-night the same development from the slow-going, old-fashioned style of phenomena, as that which I have referred to in the case of the steam boiler. I can only regret that Mr. Tesla has kept within the limits of time, and has had to refrain from giving us that which we so much liked. I wish he could give us another evening, and show us more of the experiments. I put the vote to the meeting.
Mr. Tesla: It would be difficult for me to find words to express the thoughts I feel; I have been so kindly received and generously treated. Whatever I have shown you here is not my own; it is the outcome of the work of English scientific men, whose names we delight to hear, and whom everyone loves and admires. To-night my aspirations are fulfilled in having my labors appreciated by some of the foremost men in the world, and I cannot tell you how highly I esteem your thanks, and how much it will encourage me to further work. There is one thing I desire to tell you — I am not a speaker, nor did I prepare to speak at all, and these two considerations should disqualify me at once — but this I want to say:
We have worked before with the problems that are at hand until they have been perfected. The water wheel, the gas engine, the steam engine, thanks to the great spirits which your country has produced, are brought to a high state of efficiency. In these departures we have come, so to speak, to the limit. We have now a possibility opened to us of accomplishing things we never dreamed of before, and in this lies the whole aspiration of scientific investigators. These contrivances are but in an imperfect state; they have consumed many years of my incessant thought; some other experimenter will start where I have stopped, and so the world goes on; but the same advantage which another will have from my work, l have already had myself from those who have gone before. The foremost scientific men of this country agree that there is a way of producing the electric light by fluorescence as the result of oscillations of a certain frequency. I will not dare to speak of what they have achieved in this direction, for if I do my discourse would be the praise of their work; it is, therefore, out of place. You will believe that these words are sincere, even if they are not put forth in the expressions of a good orator. We have a start. We can set up in a room the oscillations, and the only difficulty with which we are confronted is the perfecting of the apparatus. Thus we can have a light which will not need any leading wires, which will be a good luminant, and will never be destroyed — it will last for any length of time. This will be a great advancement over present methods. These difficulties are nothing compared to the problems English scientific men have opened up before. For instance, in the production of power. We are able to produce power at any point in the universe, and when this great work is finished, what an effect it will have upon the whole human race! I wish to say that the results I have shown you to-night are the outcome of the work of others, and I do not want to impress you as though I was displaying any discovery of my own. If anyone can reap the benefit of it, my desire is fulfilled. I am only paying a duty which any lover of science must pay to those who have been before in the field. Others have arrived at results. We are younger, and we go on from them, climbing the stairs; or, rather, we younger ones are taking the “lift” — we are using the “elevator.” The older ones were content with the stairs. I thank you most heartily, and express the hope that I may be able to bring before you some better work than I have shown you to-night.
For the purpose of the experiments, says the Practical Engineer, Mr. Tesla employed an alternating current dynamo of special construction, and capable of producing alternations amounting, it was said, to as many as 20,000 in a single second.
The current was controlled by a switch on the lecture table, and the first experiment consisted in holding an exhausted glass tube, 3 feet long, in one hand, while the other was placed upon the terminal of the transformer; the tube then appeared lighted throughout its length with a brilliant blue light. The lecturer then showed a glass bulb lighted in a similar way when attached to one wire only, and also showed the phenomenon of a Crookes’ shadow. On attaching a copper plate to each terminal of the transformer, an arc being formed between them, and upon the insertion of a plate of ebonite, the arc gave place to a blue light over the faces of the opposing plate.
When suitable terminals were attached to the transformer, lines of light 7 inches long were readily obtained through air, and when balls of brass 4 inches in diameter were attached, sparks were obtained over a distance of 1¼ inches. Under favorable conditions, Mr.
Tesla said, this discharge appeared exactly similar to that of the Wimshurst influence machine. Another beautiful experiment was made with two thin wires about 10 feet long stretched from the lecture table to the gallery, at a distance of about 9 inches apart. These, on the extinction of the gas, were seen to glow with a blue phosphorescent light.
Some Geissler tubes, provided by Professor Crookes, were then exhibited; one of these contained yttria and another sulphate of calcium. Attaching a wire to one of these, Mr. Tesla held it in his hand, while touching the terminal of the transformer with the other. The glass vessel was then seen to be filled with the characteristic colored phosphorescence, and the material continued to phosphorescence after the current had ceased to flow.
Referring to the difficulties found in obtaining good insulating media, Mr. Tesla said the transformer used by him was provided with oil insulation, the exterior of the primary coil being about one-quarter inch less in diameter than that of the internal diameter of the tube upon which the secondary was wound, and the annular space filled with oil. With currents of such high tension and frequency, solid insulation, according to Mr. Tesla, is quite useless, and is absolutely certain to break down after working for a short time, a fact he adduced as the reason why the costly induction coils now made often become useless after a short period. His transformer had, he said, sometimes broken down twelve times a day, yet, owing to the fluid insulation, it was never permanently injured. For the production of the effects shown with yttria and sulphate of calcium tubes, alternations amounting to the almost inconceivable number of 100,000 per second are, according to Mr. Tesla, essential. One of the most remarkable effects observed in connection with these currents of high frequency is, that no matter how great their intensity, they have no effect on the animal system, and thus appear to be perfectly safe. As an illustration of this, he took an iron bar in one hand and a vacuum tube in the other. On making his body a portion of the circuit by placing the point of the bar upon a terminal, emitting sparks several inches long, the vacuum tube glowed brilliantly, while the lecturer remained wholly unaffected.
The most striking experiment, however, was one designed to show the possibility of illuminating a room by making the space itself electric. Above the head of the lecturer was hung a plate of zinc about 8 feet long by 1 foot wide, a similar plate being hung upon the wall at a distance of about 10 feet, and parallel to the first. Between these two plates an intense electrical field was then produced, and exhausted glass tubes placed anywhere in the field at once glowed with phosphorescent light. The lecturer took in his hand a glass wand, 3 feet long, and, with no special connection of any sort to his body or to the glass, when waved in the magnet field it shone like a flaming sword. If such an electric field were produced in a room, it is manifest that it could be illuminated by merely hanging suitable glass globes without connection of any kind.
We have not been able to more than faintly describe a portion of Mr. Tesla’s experiments, but it will be evident that the phenomena disclosed were of no ordinary kind. On the possibilities of their immediate application it would be almost rash to speculate, and we shall look forward with excited curiosity to the further experiments and lectures which we understand Mr. Tesla has promised to give on the subject.