Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 8

126 elevation to receive the current and to convey it to earth through suitable means for transforming and utilizing it. "The apparatus which I have invented, and by means 1 of which this method of transmission may be effected, is of represented in the accompanying drawing, which is a diagrammatic illustration of the system. A is a coil, generally of many turns and of very large diameter wound in spiral form either about a magnetic core or not, as may be desired. C is a second coil formed by a conductor of, much larger size and smaller length wound around in proximity to the coil A. "In the transmitting apparatus the coil A constitutes the high tension secondary, and the coil C the primary of much lower tension of a transformer. In the circuit of the primary C is included a suitable source of current G. "One terminal of the secondary A is at the center of the spiral coil, and from this terminal the current is led by a conductor B to a terminal D preferably of large 1 sur face formed of or maintained by such means as a balloon at an elevation suitable for the purposes of transmission as before described. The other terminal of the secondary A is connected to earth and, preferably, to the primary also, in order that the latter may be approx1 imately of the same potential as the adjacent portions of the secondary, thus insuring safety. 1 "At the receiving station a transformer of similar construction is employed, but in this case the long coil -4