Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 46

164 in large measure, arbitrary, for if the potential be sufficiently high and the terminals of the coils be maintained at a proper elevation where the atmosphere is comparatively rarefied, the stratum of air will serve as ice conducting medium for the current produced, and the latter will be transmitted through the air with, it may be, even less resistance than through an ordinary conductor. It will be understood that the receiving coil, transformer or other apparatus may be movable, as for instance when it is carried by a vessel floating in the air or by a ship at sea. In the former case the connection of one terminal of the receiving apparatus to the ground might not be permanent, but might be intermittently or inductively established without departing from the spirit of my invention. As to the elevation of the terminals D, D', it is obvious that this is a matter which will be determined not only by the condition of the atmosphere, but also by the character of the surrounding country. Thus, if there be high mountains in the vicinity the terminals should be at a greater height and, generally, they should always be at an altitude much greater than that of the highest objects near them in order to avoid loss by leakage. Since by the means described practically any potential that is desired may be produced, the currents through the air strata may be very small, thus reducing the loss in the air. It will be observed that the phenomenon here involv-5