1887 in the journal Neues Jahrb. Mineral Geol. Paleontol. (Vol. 5, p. 145). Later, Neumann attacked the problem of giving mathematical expression to the conditions holding for a surface separating two crystalline media, and worked out from theory the laws of double refraction in strained crystalline bodies. He also made important contributions to the mathematical theory of electrodynamics, and in papers published in 1845 and 1847 established mathematically the laws of the induction of electric currents. His last publication, which appeared in 1878, was on spherical harmonics (Beiträge zur Theorie der Kugelfunctionen). With the mathematician Carl Gustav Jacobi, he founded in 1834 the mathematisch-physikalisches Seminar which operated in two sections, one for mathematics and one for mathematical physics. Not every student took both sections. In his section on mathematical physics Neumann taught mathematical methods as well as the techniques of an exact experimental physics grounded in the type of precision measurement perfected by his astronomer colleague Friedrich Wilhelm Bessel. The objective of his seminar exercises was to perfect one's ability to practice an exact experimental physics through the control of both constant and random experimental errors. Only a few students actually produced original research in the seminar; a notable exception was Gustav Robert Kirchhoff who formulated Kirchhoff's Laws on the basis of his seminar research. This seminar was the model for many others of the same type established after 1834, including Kirchhoff's own at Heidelberg University. Neumann retired from his professorship in 1876, and died at Königsberg (now Kaliningrad, Russia) in 1895 at the age of 96. His children were talented. His son, Carl Gottfried Neumann (1832–1925), became in 1858 Privatdozent, and in 1863 extraordinary professor of mathematics at Halle. He was then appointed to the ordinary chair of mathematics successively at Basel (1863), Tübingen (1865) and Leipzig (1868). Works Beiträge zur Krystallonomie (Mittler, Berlin, 1823) Beiträge zur Theorie der Kugelfunctionen (B. G. Teubner, Leipzig, 1878) Franz Neumanns Gesammelte werke (2 vols.) (B. C. Teubner, Leipzig, 1906–1928) See also Faraday's law of induction Plane of vibration International System of Electrical and Magnetic Units Notes References Olesko, Kathryn M. Physics as a Calling: Discipline and Practice in the Koenigsberg Seminar for Physics. Ithaca, NY & London: Cornell University Press, 1991. External links Primary sources on Neumann 1798 births 1895 deaths People from Barnim People from the Margraviate of Brandenburg 19th-century German mathematicians 19th-century German physicists German mineralogists Humboldt University of Berlin