The most recent example of long.distance electric transmission is that carried out in con nection with the Electrical Exhibition at Frankfort-on-the-Main, Germany, 1891. A water power of 300 horse-power, situated at Lauffen ou the Neckar, was carried over three wires to Frankfurt, a distance of 112 miles, at a potential of over 20,000 volts. The polyphase system of Nikola Testa, was employed, the transformers and dynamos being constructed by the Oerli kon Works, Switzerland, and the motors designed by Dolivo-Dobrowolski, of the Allgemeine Elektricitats Gesellschaft. Berlin, The report of the tests of this installation has not yet (January, 1892) been published.
[For more complete discussion and descriptions of electric-power transmissions, reference may be had to the following works, which have been freely quoted in the above: Electric Transmission Handbook, by F. B. Badt; Electric nansmission of Energy, by Gisbert Kapp, C.E. Kritische Vergleichung der Kraftuebertragung mit den Gebraenehlichsten Meehan ischen Uebertragungs Systemen, by A. Beringer: Dynamo Electric _Machinery, by Prof. S. P.
Thompson ; The Electric Motor and its Applications, by T. C. Martin and Joseph Wetzler; Electric _Motors, by F. J. Sprague (late Ensign U. S. NO, a paper read before U. S. Naval Institute, Annapolis, May 16, 1897; The Transmission of .Power by Electricity, by F. J. Sprague, a lecture delivered before the Franklin Institute, November 12, 1888; Some Appli cations of Electric Transmission, by F. J. Sprague, a lecture delivered before the students of Sibley College and published in the Scientific American. Supplement, July 20 and 27 and August 3, 1889 ; the papers of George W. Mansfield, Richard P. Rothwell, Francis A. Pocock, IL C. Spaulding. and ethers, read before the American Institute of Mining Engi neers; and the paper of H. Ward Leonard, read before the Association of Mining Engineers of the Province of Quebec, April 29, 1891; and an article by the same author in The Electrical Engineer, September 2, 1891. Also " Cantor Lectures on the Electric Transmission of Power," by G. Kapp, Journal Society of Arts, July 3, 10, and 17, 18911