. Annual report of the Board of Regents of the Smithsonian Institution . y alter-nator.—The first highfrequency alternatorwas built by Prof. EliliuThomson in 1889. Andit^ was while experi-menting with it in 1900 that Doctor Tatum made his very in-teresting discovery that high frequency currents of large amperagecould be passed through the body without injury.^ « United States patents Nos. 706742, July 6, 1902; 706747, September 28, 1901;727330, March 21, 1903; 730753, April 9, 1903. 6 Ibid and United States patent No. 706741. Austin, Bulletin of the Bureau of Standards, vol. 3, No. 2. ^Austin
. Annual report of the Board of Regents of the Smithsonian Institution . y alter-nator.—The first highfrequency alternatorwas built by Prof. EliliuThomson in 1889. Andit^ was while experi-menting with it in 1900 that Doctor Tatum made his very in-teresting discovery that high frequency currents of large amperagecould be passed through the body without injury.^ « United States patents Nos. 706742, July 6, 1902; 706747, September 28, 1901;727330, March 21, 1903; 730753, April 9, 1903. 6 Ibid and United States patent No. 706741. Austin, Bulletin of the Bureau of Standards, vol. 3, No. 2. ^Austin assumed from the figure he obtained for the* dampening, that theoscillations were not contiiuious; but the method used for determining thedampening is not applicable to this case, and a comparison of the currentsand voltages with the frequencies given in Austins experiments, shows thatthese oscillations must have been continuous. Thomson, Electrical Engineer, July 30, 1890, and London Electrician, Sep-tember 12, 1890. f Thomson, Electrical Engineer, March 11, Fig. 1.—Eliliu Thomsons method of producinjihigh frequency oscillations. WIRELESS TELEPHONY—PESSENDEN. 173 From 1898 to 1900 numerous experiments were made on antennaeof large capacity, and it was found that instead of using sheets ofsolid metal or wire netting, single wires could be placed at a con-siderable fraction of the wave-length apart and yet give practicallythe same capacity effect as if the space between them were filled withsolid conductors. From other investigations on the variation of radiation with fre-quency the result was arrived at that it should be possible to con-struct an alternating-current dynamo of sufficiently high frequencyand output to give ample radiation for wireless telegraphic purposes. In 1900 a large American electrical manufacturing company kindlyconsented to take up the construction of such a dynamo. As a pre-liminary, a dynamo of 1 kilowatt output and 10,000 cycles (shown in
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