Book Review - Nikola Tesla: Lecture before the New York Academy of Sciences, April 6, 1897

Nikola Tesla: Lecture before the New York Academy of Sciences, April 6, 1897
Edited by Leland I. Anderson. Breckenridge, Colo: Twenty First Century Books, 123 pp, 1994. $12.95

"At the close of 1894...it occurred to me to investigate the actinic action of phosphorescent bodies." So begins the report by Nikola Tesla on the use of vacuum discharge tubes for the detection of wireless signals. Tesla's report on April 6, 1897, was in the form of a lecture before the New York Academy of Sciences. Tesla in his writings often referred to Lenard- and Roentgen-streams and tubes; he obviously considered Lenard and Roentgen to hold equal priority in the discovery of the X-ray tube.

Working in New York City, Tesla carried out many experiments with high-frequency alternators, Crookes tubes, single-electrode globes, and vacuum bulbs. He noted that the actinic power of the Crookes bulbs varied greatly and that many problems about their use still needed to be resolved. Together with a firm of artist's photographers in New York, Tesla started making photographs with the various tubes. The plates from their experiments were placed in a corner of Tesla's laboratory. He noticed that photographic impressions were obtained using the Crookes tubes, but because many of the plates were defective, resolved to review the process with the photographer. However, as Tesla states, "Just as my attention was arrested by [the obtaining of the photographic impressions], my laboratory with almost everything it contained was destroyed [by fire]...I had hardly finished the work of reconstruction and resumed the course of my ideas when the news of Roentgen's achievement reached me. Instantly the truth flashed upon my mind. I hurried to repeat his incompletely reported experiments, and there I beheld the wonder myself. Then - too late - I realized that my guiding spirit had again prompted me and that I had failed to comprehend his mysterious signs." The fire occurred on March 13, 1895, approximately 9 months before Roentgen's discovery.

Born in 1856 of Serbian parents in what is now Croatia, Tesla came to the United States in 1884, establishing a laboratory in 1887 and becoming a citizen in 1891. One of the main reasons he came to the United States was that he was unable to interest European engineers in a new alternating-current motor he had conceived. Tesla brought to the world great inventive gifts: wireless telegraphy embodying the "Tesla coil," telemechanics, and the Tesla turbine. In the preface of this book, he is also given credit for inventing the VTOL aircraft (vertical takeoff and landing airplane, the forerunner of the helicopter). His greatest achievement may be his discovery of the rotating magnetic field and the brilliant adaptation of it to his induction motor. The rotating magnetic field is of course central to the concept of the magnetic resonance imager. We all know Tesla for the unit of magnetic flux density named after him on the centennial of his birth. The only other American to share such recognition is Joseph Henry (the unit of inductive resistance is named the henry).

Many of the historical pearls detailed above appear in this little book, which essentially presents Tesla's lecture. As commented on by Kenneth and James Corum on the back cover, this lecture demands careful study and balanced evaluation. Tesla carried out many radiologic experiments after Roentgen's discovery, commenting on, among other factors, the dangers of X rays and methods to guard against them. The lecture sheds light on a fascinating part of our profession's history, detailing one of the greatest visionaries who ever lived. Tesla died in New York City on January 7, 1943.