(1856 - 1943) American engineer and inventor who discovered the principle of a rotating magnetic field, invented the Tesla Coil and with Edison developed electric lighting. Fine content, scarce T.L.S. on his personal letterhead, 1p. 4to., New York, July 25, 1894, to the pioneering American engineer N. S. Amstutz, in part: "...I am receiving a great many communications such as yours...The identical experiment which you illustrate was performed by Messrs. Spottiswood [sic], Gordon and others a very long time ago, and the same observation was made in regard to the properties of the current when the breaking was rapid. I think that in your experiment the strength of the current was reduced and the E.M.F. increased when the wheel was more rapidly rotated. You have probably got in this case less energy through the body. It is difficult to say exactly what the result in your case was, because it depends entirely on the electrical constants of the circuits and on the rate of breaking...". Amstutz, as early as 1865, devised a way to transmit pictures electronically. The April 6, 1895 issue of Scientific American featured his invention called The Amstutz Electro-Artograph. In 1877, William Spottiswoode along with J. E. H. Gordon undertook a series of experiments using a large induction coil; Tesla elaborated upon these earlier attempts. Tesla mentioned the scientists in his 1892 lecture "Experiments with Alternate Currents of High Potential and High Frequency": "Usually in operating an induction coil we have set up a vibration of moderate frequency in the primary, either by means of an interrupter or break, or by the use of an alternator. Earlier English investigators, to mention only Spottiswoode and J. E. H. Gordon, have used a rapid break in connection with the coil. Our knowledge and experience of to-day enables us to see clearly why these coils under the conditions of the tests did not disclose any remarkable phenomena...In the experiments such as performed this evening, we operate the coil either from a specially constructed alternator capable of capable of giving many thousands of reversals of current per second, or, by disruptively discharging a condenser through the primary, we set up a vibration in the secondary circuit of a frequency of many hundred thousand or millions per second. Folds, very good condition.