Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 51

T 1 J T 1 J 1 1 T 1 J T induction coil passes through only a part of the attenuated gas in the form of a luminous thread or arc, a still further and considerable diminution of the pressure being required to render the entire mass of the gas, enclosed in a vessel, conducting. While this is true in every particular so long as electro-motive or current-impulses, such as are obtainable with ordinary forms of apparatus are employed, I have found that neither the general behavior of the gases, nor the known relations between electrical conductivity and. barometric pressure are in conformity with these. observations, when impulses are used such as are producible by methods and apparatus devised by me and which have peculiar, and hitherto unobserved properties, and are of effective electromotive forces measuring many hundred thousand or millions of volts. Through the continuous perfection of these methods and apparatus and the investigation of the actions of these currentimpulses I have been led to the discovery of certain highly important and useful facts which have hitherto been unknown. Among these and bearing directly upon the subject of my present application are the following: First, that atmospheric or other gases, even under normal pressure, when they are known to behave as perfect insulators, are in a large measure deprived of their dielectric properties by being subjected to the influence of electro-motive impulses of the character and magnitude I have referred to, and assume conducting and other qualities, which have been so far observed only in gases greatly attenuated or heated -2This page retyped from microfilm for better readability - Ed. 169