Synthesized answer
The central thesis of this text, as presented by Nikola Tesla, concerns experiments with alternating currents, specifically those of high potential and high frequency [1]. Tesla states that the investigation "deals with alternating currents, and, to be more precise, with alternating currents of high potential and high frequency" [1].
While the text emphasizes the importance of very high frequencies for many of the presented results, and notes that they are desirable for securing numerous effects and for conveniently obtaining the necessary high potentials, it does not explicitly state a singular, overarching central thesis beyond the focus on these specific types of currents and their experimental applications [1, 2]. The passages describe the *subject* of the investigation, but not a definitive, concise statement of its core argument or conclusion.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Experiments with alternate currents of high potential and high frequency by Nikola Tesla Description: A lecture delivered before the Institution of Electrical Engineers, London, February 1892. Complete with illustrations.A short time ago I had the honor to bring before our American Institute of Electrical Engineers some results then arrived at by me in a novel line of work. I need not assure you that the many evidences which I have received that English scientific men and engineers were interested in this work have been for me a great reward and encouragement. I will not dwell upon…
frequency is essential for the production of the results presented is a question which, even with my present experience, would embarrass me to answer. Some of the experiments may be performed with low frequencies; but very high frequencies are desirable, not only on account of the many effects secured by their use, but also as a convenient means of obtaining, in the induction apparatus employed, the high potentials, which in their turn are necessary to the demonstration of most of the experiments here contemplated.