Nikola Tesla U.S. Patent 645,576 - System of Transmission of Electrical Energy Patent Wrapper Page 17

acquire this necessary knowledge, but there is hope that we may, and that is by means of electrical resonance. If ever we can ascertain at what period the earth's charge, when disturbed, oscillates with respect to an oppositely electrified system or known circuit, we shall know a fact possibly of the greatest importance to the welfare of the human race. I propose to seek for the period by means of an electrical oscillator or a source of alternating electric currents. One of the terminals of the source would be connected to earth, as, for instance, to the city water, mains, the other to an insulated body of large surface. It is possible that the outer conducting air strats or free space contains an opposite charge, and that, together with the earth, they form a condenser of very large capacity. In such case the period of vibration may be very low, and an alternating dynamo machine night serve for the purpose of the experiment. I would then transform the current to a potential as high as it would be found possible, and connect the ends of the high tension secondary to the ground and to the insulated body. By varying the frequency of the currents, and carefully observing the potential of the insulated body, and watching for the disturbance of various neighboring points of the earth's surface, resonance might be detected. Should, as the majority of scientific men in all probability believe the period be extremely small, then a dynamo machine would not do, and a proper electrical oscillatcr would have to be produced, and perhaps it might not be possible to ob3 135