Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 54

172 As to the influence of rarefaction upon the electric conductivity imparted to the gases it is noteworthy that, whereas the atmospheric or other gases begin, ordinarily, to manifest this quality at something like seventy-five millimeters barometric pressure, with the impulses of excessive electro-motive force to which I have referred, the conductivity, as already pointed out, begins even at normal pressure and continuously increases with the degree of tenuity of the gas so that at, say, one hundred and thirty millimeters pressure, when the gases are known to be still nearly perfect insulators for ordinary electro-motive forces they behave towards electro-motive impulses of several millions of volts like excellent conductors as though they were rarefied to a much higher degree. By the discovery of these facts, and the perfection of means for producing in a safe, economical, and thoroughly practicable manner, current-impulses of the character described, it becomes possible to transmit, through easily accessible and only. moderately rarefied strata of the atmosphere, electrical energy not merely in insignificant quantities such as are suitable for the operation of delicate instruments and like purposes, but also in quantities suitable for industrial uses on a large scale up to practically any amount and, according to all the experimental evidence I have obtained, to any terrestrial distance. To conduce to a better understanding of this method of transmission of energy and to distinguish it clearly, both in its theoretical aspect and in its practical bearing, from other known -5This page retyped from microfilm for better readability - Ed.]