>>9508661all this is also related to Paschen's law:
>equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap lengthhttps://en.wikipedia.org/wiki/Paschen%27s_lawsee the video and schematics, I tried to make the schematic as clear as possible using the same schema from tesla's patent, short video (with sound) showing the basic principle behind this
https://imgur.com/a/lTUgua6continuing
https://patentimages.storage.googleapis.com/62/90/92/45a5932052a940/US645576.pdf>page4, parag135 "with terminals not more than thirty to thirty-five thousand feet (10 km) above the level of the sea, and even this comparatively-small elevation will be required chiefly for reasons of economy, and, if desired, it may be considerably reduced, since by such means as have been described practically any VOLTAGE that is desired may be obtained, the currents through the air strata may be rendered very small, whereby the loss in the transmission may be reduced."terminals at 30000 feet high? why? this is because at high altitutes the gases of the atmosphere are rarefied and this lowers the "breakdown voltage" so conduction can be achived at lower voltages this gives longer discharge distances with the same voltage thats why the proposal to use this scheme of putting the terminals at high altitue (he sugest using ballons)
>page3, parag.95 "for if the potential (VOLTAGE) be sufficiently high and if the terminals of the (transformer) coils be maintained at the proper altitudes the action described will take place, and a current will be transmitted through the elevated air strata (rarefied atmosphere), which will encounter little and possibly even less resistance than if conveyed through a copper wire of a practicable size. " 