How Tesla Conceived the Rotary Magnetic Field Part Il By Nikola Tesla Editor’s Note: The popular movie “The Prestige” brought mythic figure Nikola Tesla to the forefront of pop culture last year. This “unsung prophet of the electric age” is without a doubt the granddaddy of our industry and many others. Tesla’s autobiography, originally written for the Electrical Experimenter magazine in 1919, has in recent years been reproduced on the Web and by various publishers, and gives tremendous insight into the workings of his brilliant mind. Following is an excerpt from the third chapter of “My Inventions,” which chronicles Tesla’s “discovery of the rotating magnetic field.” In one of the sinking spells which was thought to be the last, my father rushed into the room. I still see his pallid face as he tried to cheer me in tones belying his assurance. “Perhaps,” I said, “I may get well if you will let me study engineer- ing.” “You will go to the best technical institution in the world,’ he solemnly replied, and I knew that he meant it. A heavy weight was lifted from my mind but the relief would have come too late had it not been for a marvelous cure brought through a bitter decoction of a peculiar bean. I came to life like Lazarus to the utter amazement of everybody. My father insisted that I spend a year in healthful physical outdoor exercise to which I reluctantly consented. For most of this term I roamed in the mountains, loaded with a hunter’s outfit and a bun- dle of books, and this contact with nature made me stronger in body as well as in mind. I thought and planned, and con- ceived many ideas almost as a rule delu- sive. The vision was clear enough but the knowledge of principles was very limited. In one of my inventions, I proposed to convey letters and packages across the seas, through a submarine tube, in spher- ical containers of sufficient strength to resist the hydraulic pressure. The pump- ing plant, intended to force the water through the tube, was accurately figured and designed and all other particulars carefully worked out. Only one trifling detail, of no consequence, was lightly dismissed. I assumed an arbitrary veloc- ity of the water and, what is more, took pleasure in making it high, thus arriving at a stupendous performance supported by faultless calculations. Subsequent reflections, however, on the resistance of pipes to fluid flow induced me to make this invention public property. Another one of my projects was to construct a ring around the equator which would, of course, float freely and could be arrested in its spinning motion by reactionary forces, thus enabling trav- el at a rate of about one thousand miles an hour, impracticable by rail. The read- er will smile. The plan was difficult of execution, I will admit, but not nearly so bad as that of a well known New York professor, who wanted to pump the air from the torrid to temperate zones, entirely forgetful of the fact that the Lord had provided a gigantic machine for this purpose. Still another scheme, far more impor- tant and attractive, was to derive power from the rotational energy of terrestrial bodies. I had discovered that objects on the earth’s surface owing to the diurnal rotation of the globe, are carried by the same alternately in and against the direc- tion of translatory movement. From this results a great change in momentum which could be utilized in the simplest imaginable manner to furnish motive effort in any habitable region of the world. I cannot find words to describe my disappointment when later I real- ized that I was in the predicament of Archimedes, who vainly sought for a fixed point in the universe. At the termination of my vacation I was sent to the polytechnic school in Gratz, Styria (Austria), which my father had chosen as one of the oldest and best reputed institutions. That was the moment I had eagerly awaited and I began my studies under good auspices and firmly resolved to succeed. My pre- vious training was above average, due to my father’s teaching and opportunities afforded. I had acquired the knowledge of a number of languages and waded through the books of several libraries, picking up information more or less use- ful. Then again, for the first time, I could choose my subjects as I liked, and free- hand drawing was to bother me no more. I had made up my mind to give my parents a surprise, and during the whole first year I regularly started my work at three o’clock in the morning and contin- ued until eleven at night, no Sundays or holidays excepted. As most of my fellow- students took things easily, naturally I eclipsed all records. In the course of the year I passed through nine exams and the professors thought I deserved more than the highest qualifications. Armed with their flattering certificates, I went home for a short rest, expecting triumph, and was mortified when my father made light of these hard-won honors. That almost killed my ambition; but later, after he had died, I was pained to