Jacobi, Moritz Hermann von

(b. Potsdam, Germany, 21 September 1801; d. St. Peterburg, Russia, 27 February 1874)

physics.

At the urging of his parents Jacobi studied architecture at Göttingen and in 1833 set up practice in Königsberg, where his younger brother Carl was a professor of mathematics. He also began to turn his attention to physics and chemistry. In 1835 he went to the University of Dorpat as a professor of civil engineering, and in 1837 he moved to St. Petersburg. There he became a member of the Imperial Academy of sciences (adjunct in 1839, extraordinary in 1842, and ordinary in 1847) and devoted his energies to research on electricity and its various practical applications, his interest in this subject having developed since his days in Göttingen.

Jacobi engaged in a number of studies of great interest in the fast-developing subject of electricity, dealing especially with its possible technical applications. Although most of the results of his work were published and were generally available, their impact was minimal. One reason for this certainly lies in his physical isolation from the centers of development in electricity in France and England. Another can probably be found in that most of his practical applications proved to be premature; that is, the technology had not developed enough to sustain them.

Jacobi’s most interesting work, reported to the St. Petersburg Academy in 1838 and to the British Association two years later, was his investigation of the power of an electromagnet as a function of various parameters; electric current, thickness of wire, number of turns on the helix, diameter of the helix, and thickness of the iron core. Of great practical value in the design of motors and generators, this work was pursued in greater detail by Henry Rowland and John Hopkinson almost half a century later.

In May 1834 Jacobi built one of the first practical electric motors. He performed a variety of tests on it, for instance measuring its output by determining the amount of zinc consumed by the battery. In 1838 his motor drove a twenty-eight-foot boat carrying a dozen Russian officials on the Neva River at a speed of one and one-half miles per hour. His hopes of covering the Neva with a fleet of magnetic boats were doomed from the beginning, however, by the cost of battery-powered operation and by the fumes that such batteries emitted.

In a separate enterprise Jacobi was asked to continue the work of Baron Pavel Schilling, who had demonstrated the needle (electromagnetic) telegraph to the Russian government in 1837 but who had died that year before an experimental line could be set up. Jacobi improved on Schilling’s design and by 1839 had constructed an instrument quite similar to Morse’s first, and earlier, receiver. Various experimental lines were run in succeeding years, but practical telegraphy did not come to Russia until the 1850’s, with the introduction of the Siemens and Halske system.

In 1838 Jacobi announced his discovery of the process he called“galvanoplasty” (now called electrotyping), the reproduction of forms by electrodeposition. In subsequent publications he described his techniques in great detail.

BIBLIOGRAPHY

I. Original Works. Jacobi’s articles are listed in the Royal Society’s Catalogue of scientific Papers, III, 517-518; VIII, 8. Among the more important are “Expéeriences électromagnétiques,” in Bulletin de l’Académie impériale des sciences de St. Pétersbourg, 2 (1837), 17-31, 37-44, trans. in R. Taylor et al., eds., Scientific Memoirs, 2 (1841), 1-19; and “Galvanische und electromagnetische Versuche. Ueber electro-telegraphische Leitungen,” in Bulletin de l’Académie impériale des sciences de St. Pétersbourg, 4 (1845), 113-135, 5 (1847), 86-91, 97-113, 209-224, 6 (1848), 17-44, 7 (1849), 1-21, 161-170, and 8 (1850), 1-17.

Published separately as pamphlets were Mémoire sur l’application de l’électro-magetisme au mouvement des machines (Potsdam, 1835), trans. in Scientific Memoirs, 1 (1837), 503-531;and Die Galvanoplastik (St. Petersbourg, 1840), trans. in Annals of Electricity, Magnetism and Chemistry, 7 (1841), 323-328, 337-344, 401-448.; and 8 (1842), 66-74, 168-173.

Jacobi’s papers are preserved in the archives of the Soviet Academy of Sciences in Leningrad. His correspondence with his brother was published by Wilhelm Ahrens as Briefwechsel zwischen C. G. J. Jacobi und M. H. Jacobi (Leipzig, 1907).

II. Secondary Literature. A biographical account, with portrait, appears in German in the Bulletin de l’Académie impériale des sciences de St. Pétersbourg, 21 (1876), 262-279. A much shorter sketch is Ernest H. Huntress, in Proceedings of the American Academy of Arts and Sciences, 79 (1951), 22-23.

Bernard S. Finn