Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 57

1. ( ) ) 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 surface, formed 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, if desired also to the primary, in order that the latter may be at substantially the same potential as the adjacer portions of the secondary, thus insuring safety. At the receiving station a transformer of similar construction is employed, but in this case the coil C', of thick wire or cable, the secondary of the transformer. In the circuit of the latter are included lamps L, motors M, or other devices for utilizing the current. The elevated terminal D' is connected. with the centre of the coil A', and the other terminal of said coil is connected to earth and, preferably, also to the coil c', for the reasons above stated. It will be observed that in coils of the character described the potential gradually increases with the number of turns towards the center and, the difference of potential between the adjacent turns being comparatively small, a very high potential, impracticable with ordinary coils, may be successfully obtained. It will be furthermore noted that, no matter to what an extent the coils may be modified in design and construction, owing to their general arrangement and manner of connection, as illustrated, those portions of the wire or apparatus which are highly charged will be out of reach, while those parts of the -8This page retyped from microfilm for better readability - Ed.] 175