Nikola Tesla U.S. Patent 511,916 - Electric Generator Patent Wrapper Page 21

28 8 in the coil. These currents, if the period of mechanical oscillation be constant will be of constant period, and may be utilized for any purpose desired. In the case under consideration it is assumed as a necessary condition that the inertia of the movable element of the generator and the electro-magnetic reaction which it exerts will not be of such character as to materially disturb the action of the engine. Fig. 2 is an example of a combination in which the engine is not of itself capable of determining entirely the period of oscillat ion, but in which the generator contributes to this end. In this figure the engine is the same as in Fig. 1. The exterior air spring is however omitted and the air spaces at the ends of the cylinder A relied on for accomplishing the same purpose. As the pressure in these spaces is. liable to variations from variations in the steam or gas used in impelling the piston they might affect the period of oscillation, and the condit ions are not as stable and certain as in the case of an engine constructed as in Fig. 1. But if the natural period of vibration of the elastic system be made to approximately accord with the average period of the engine such tendencies to variation are very largely overcane and the engine will preserve its period even though a considerable range of variations of pressure. The generator in this case is composed of a magnetic -12