Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 50

168 Lub. جسد TO ALL TO WHOM IT MAY CONCERN: BE IT KNOWN that I, NIKOLA TESLA, a citizen of the United States, residing at New York, in the County and State of New York, have invented certain new and useful improvements in systems of transmission of electrical energy of which the following is a specification, reference being had to the drawing accompanying and forming a part of the same. It has been well known heretofore that by rarefying. the air enclosed in a vessel its insulating properties are impaired to such an extent that it becomes what may be considered as a true conductor, although one of admittedly very high resistance. The practical information in this regard has been derived from observations necessarily limited in their scope by the character of the apparatus, or means heretofore known, and the quality of the electrical effects producible thereby. Thus it has been shown by WILLIAM CROOKES in his classical researches, which have so far served as the chief source of knowledge of this subject, that all gases behave as excellent insulators until rarefied to a point corresponding to a barometric pressure of about seventy-five millimeters and, even at this very low pressure, the discharge of a high tension Speer uns This page retyped from microfilm for better readability - Ed.]