Here is more on what he knew about the earth and the atmosphere. Pay attention to parallel lines around the planet. These are plasma double layers with different densities and subsequent voltage levels as you go towards the ground. As the plasma density lowers going to ground there is less voltage available going to ground level. With the ground being the zero point.
“It was evident to me that wireless transmission of energy, if it could ever be accomplished, is not an invention; it is an art. Bell’s telephone, Edison’s phonograph, or my induction motor were inventions, but the wireless transmission of energy is an art that requires a great many inventions in combination.
“We are living on a planet that is rushing through space; this planet is partly conducting and partly insulating. If it were all conducting, or if it were all insulating, we could not transmit energy without wire. It is only because it is partly conducting and partly insulating that a glorious future for man is reserved through the application of this art.”
–Nikola Tesla
(From a pre-hearing interview with Nikola Tesla and his legal counsel in 1916 to protect his radio patents from the Guglielmo Marconi and the Marconi Company.)
[Fig. 1]:
“We are living on a planet of well-nigh inconceivable dimensions, surrounded by a layer of insulating air above which is a rarefied and conducting atmosphere. This is providential, for if all the air were conducting the transmission of electrical energy thru the natural media would be impossible.” –NT
In every case you can insert Plasma field where the Natural Medium or Media is used.