Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 45

1113DDOJECT LI JEJU ter 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 also to the coil C' for the reasons above stated. The length of the fine wire 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 itself and the circuit with which it is designed to be used. To 11lustrate, if the rate at which a current traverses the circuit, including the coil, be 185,00 miles per second, thon 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 a secondary 50 miles in length. It will be observed that in coils of the character described, the potential gradu ally increases with the number of turns and the difference of potential between adjacent turns is comparatively small, and a very high potential, impracticable with ordinary coils, may be successfully obtained. As the main object of the invention is to produce a current of extremely high potential, this object will be facilitated by using a primary current of very cont siderable frequency, but the frequency of the current is, -4163