Nikola Tesla U.S. Patent 511,916 - Electric Generator Patent Wrapper Page 10

T T 1 Nov. 4-93 TO ALL WIDOM IT MAY CONCERN: BE IT KNOWN, That I, NIKOLA TESLA, a citizen of the United States, residing at New York, in the County and State of New York, have invented certain new and useful improvements in ELECTRIC GENERATORS of which the following is a specification, reference being had to the drawings accompanying and forming a part of the same. serial number 483563 In an application of even date herewith I I have shown and described a form of engine invented by me, which, under the influence of an applied force such as the elastic tension of steam or a gas under pressure, yields an oscillat ion of constant period. En In order that my present invention may be more readily understood I will explain the conditions which are to be observed in order to secure this result. I It is a well known mechanical principle that if a spring possessing a sensible inertia be brought under tension, as by being stretched, and then freed, it will perform vibrations which are isochronous, and as to period, in the main, dependent upon the rigidity of the spring, and its own inertia or that of the system of which it may form an immediate part. This is known to be true in all cases where the force which tends to bring the spring or movable system into a given position is proportionate to the displacement. 17