Nikola Tesla Books
[Sec. 3.a., cont.] nevertheless, when the storm was still at a distance of about 80-100 miles, that is judging the distance from the velocity of sound. As the storm got nearer the adjustment had to be rendered less and less sensitive... A small spark gap was bridged by a bright spark when the lightning occurred in the neighborhood... As the storm receded the most interesting and valuable observation was made. The instrument was again adjusted so as to be more sensitive... It did so for a while, when it stopped. It was thought that the lightning was now too far and it may have been about 50 miles away. All of a sudden the instrument began again to play, continuously increasing in strength, although the storm was moving away rapidly. After some time, the indications again ceased but half an hour later the instrument began to record again. When it once more ceased the adjustment was rendered more delicate, in fact very considerably so, still the instrument failed to respond, but half an hour or so it again began to play... By this time the storm had moved away far out of sight. By readjusting the instrument and setting it again so as to be very sensitive, after some time it again to play periodically. The storm was now at a distance greater than 200 miles at least. "[This experience] showed clearly the existence of stationary waves, for how could the observations be otherwise explained? How can these waves be stationary unless reflected and where can they be reflected from unless from the point where they started? It would be difficult to believe that they were reflected from the opposite point of the Earth's surface, though it may be possible. But I rather think they are reflected from the point of the cloud where the conducting path began; in this case the point where the lightning struck the ground would be a nodal point. It is now certain they they can be produced with an oscillator." A narrative article by Tesla entitled "The Transmission of Electric Energy Without Wires," appearing in the March 5, 1904, issue of the Electrical World and Engineer, pp. 429-431, also describes the detection of what he interpreted to be standing waves in the earth, induced by lightning strokes. From this observation, an entirely different approach to wireless power transmission suggested itself to Tesla--earth conduction, by means of establishing standing waves in the earth's static charge over its entire surface (his description). b. Patent No. 787,412 remarks on lightning storms In a subsequent patent application for wireless power transmission filed on May 16, 1900, after Tesla's return to New York (granted as No. 787,412, April 18, 1905, under the title "Art of Transmitting Electrical Energy Through the Natural Mediums") and based on the standing wave observations, Tesla provides a few more observations of lightning storms: 5
