Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 9

A constitutes the primary and the short coil c' the secondary of the transformer. In the circuit of the latter are arranged lamps L, motors M, or other devices for utilizing the current. The elevated terminal D' connects with the center of the coil A', and the other terminal of said coil is connected to earth and preferably al so to the coil c' for the reasons above stated. i The length of the high tension coil of each apparatus should be approximately one quarter of the wave length of the electrical disturbance in the circuit, this estimate being based on the velocity of propagation of the electrical disturbance through the coil itsalf and the circuit with which it is designed to be used. To illustrate, in accordance with accepted views, if the rate at which a current traverses the circuit, including the two high tension. coils, be 185,000 miles per second, then a frequency of 925 per second would maintain 925 stationary waves in a circuit 185,000 miles long, and each wave would be 200 miles in length. For such a frequency I should use in each high tension coil a conduc1 tor 50 miles in length, or in ge reral, with due allowance for the capacity of the leading wires and terminals, such length of conductor would would secure the highest electrical pressures at the terminals under the working conditions. It 111 be observed that in coils of the character described, the potential gradually increases with the number of turns and the difference of potential between adjacent turns is comparatively small, and a very high -5127