Nikola Tesla U.S. Patent 511,916 - Electric Generator Patent Wrapper Page 13

20 3 any special advantage. Such an engine as I have described affords a means of accomplishing a result heret ofore unat ta ined, the tinued production of electric currents of constant period, by impart ing the moverents of the piston to a core or coil in a magnetic field. conIt should be stated, however, that in applying the engine for this purpose certain conditions are encountered which should be taken into consideration in order to satisfactorily secure the desired result. When a conductor is moved in a magnetic field and a current caused to circulate therein, the electro-magnetic reaction between it and the field, might disturb the mechanical oscill at ion to such an extent as to throw it out of isochronism. This, for instance, might occur when the electro-magnet ic reaction is very great in comparison to the power of the engine, and there is a retardation of the current so that the electro-magnetic reaction might have an effect similar to that which would result from a variation of the tension of the spring but, if the circuit of the generator be so adjusted that the phases of the electrano tive force and current coincide in time, that is to say, when the current is not retarded, then the generat or driven by the engine acts merely as a frictional resistance and will not, as a rule, alter the period of the mechanical vibration, although it may vary its amplitude. diti on may be readily secured by properly proportioning -4This con