PU'PIN, MICHAEL IDVORSKY ( 1858— ). An American physicist and inventor, born at Idvor, 1 Southern Hungary, of Servian ancestry. He was educated at the village school of his native town and at a military school at Prague, and came to America in 1874. He entered Columbia College in 1879 and graduated in 1883. He then studied mathematics and physics at Cambridge Univer sity, England, and also at the University of Berlin. where in 1889 lie received the degree of doctor of philosophy, holding while abroad the John Tyndall Fellowship of Columbia. Upon his I return to America he was appointed instructor in mathematical physics at Columbia University, and in 1892 adjunct professor of mechanics. In 1901 he became professor of eleetro-meehanics. Professor Pupin's most important researches were in electrical resonance. electrical wave propagation, and theoretical and experimental I consideration of the magnetization of iron. He I became well known for his work on the propaga tion of electrical waves, as lie was able to apply his researches in this field to long-distance tele phony and multiplex telegraphy. By his use of '
non-uniform conductors in which wire coils pos sessing a certain amount of self-induction were placed at stated intervals along the conductor, he was able to prevent the attenuation of the elee trieal waves so that a far greater amount of the original current could be received at the terminal of the telephone conductor or eable. This inven tion greatly extended the limits of long-distance telephony and made possible the use of the tele phone with cables of considerable length. The rights were acquired by the Bell Telephone Com pany, in 1901, a year after the research had been described before the American Institute of Elec trical Engineers, and was also bought by German telephone interests and given an extensive and successful trial.