Feddersen, Berend Wilhelm

(b. Schleswig, Germany, 26 March 1832; d. Leipzig, Germany, 1 July 1918)

physics.

Not much is known of Feddersen’s early life or parentage, except that he was an only child. He studied in Göttingen, Berlin, Leipzig, and Kiel, where he received the doctorate in 1858 with a dissertation on the nature of electric-spark discharges, which he studied by improving a rotating-mirror technique of Wheatstone’s. In the same year he moved to Leipzig, where he spent the rest of his life.

By his early and subsequent investigations, Feddersen showed that the discharge of a Leiden flask produces a train of damped oscillations, which he contrived to record in a series of splendid photographs. The finding that a circuit made up of a capacitance, a resistance, and an inductance produces oscillations whose frequency and amplitude depend on these components also proved to be of considerable technological importance. Feddersen’s photographs served to confirm the 1853 theory of William Thomson (the future Lord Kelvin), who had been occupied—as had Faraday—with the analysis of long-distance signaling in connection with the first attempt to lay a transatlantic cable and had developed the formula for the frequency of a damped resonant circuit; Thomson’s public acknowledgment of his debt to Feddersen brought the latter worldwide renown. The beginnings of radiotelegraphy likewise depended on spark-discharge techniques, which dominated radio transmission well on into the twentieth century.

Feddersen is also remembered for his contributions to scientific bibliography, because of his personal participation in (and financial support of) Poggendorff’s Biographisch-literarisches Handwöreterbuch (now in its seventh edition). He undertook the editorship of the third volume after the death of the first editor, Johann Christian Poggendorff, in 1877; but its appearance was delayed because of a quarrel with the publisher, and the work was finally taken over by a third physicist, Arthur Joachim von Oettingen. (All three died octogenarians, a useful trait for bibliographers.) Feddersen supported the publication of volumes III and IV by donating the substantial sum of 30,000 marks and a few weeks before his death sought to assure the appearance of further volumes by setting up, jointly with his wife, a 100,000-mark endowment that was unfortunately wiped out by the runaway German inflation of 1919–1923.

In 1866 Feddersen married a distant cousin, Dora Feddersen, who was sickly and on whose account the practically withdraw from scientific activity. She died in 1889, and in 1890 he married Helga Kjär, who survived him until 1936. There were no children from either marriage.

BIBLIOGRAPHY

I. Original Works. A list of Feddersen’s publications appears in Poggendorff’s Biographisch-literarisches Handwörterbuch, vols. I–V. His diss., Beiträge zur Kenntniss des elektrischen Funkens, was published by the University of Kiel (a copy is in the British Museum). The article based on the diss, and his subsequent papers in Annalen der Physik, 2nd ser., 103, 108,112,113,115,116, form vol. CLXVI of Ostwald’s Klassiker der exakten Wissenschaften, T. Des Coudres, ed. (Leipzig, 1908), which also contains a portrait.

II. Secondary Literature. Obituaries are A. von Oettingen, in Berichte der Königlichen sächsischen Gesellschaft der Wissenschaften, 70 (1918), 353; T. Des Coudres, in Physikalische Zeitschrift, 19 (1918), 393; and G. von Eichhorn, in Jahrbuch der drahtlosen Telegraphie, 13 (1918/1919), 345. An appreciation on the centenary of his birth by W. Dudensing is in Hochfrequenztechnik und Elektroakustik, 39 (1932), 77. For the subsequent history of Poggendorff’s bibliography, see Isis, 57 (1966), 389.

Charles SÜsskind