KIRCHHOFF, GUSTAV ROBERT ( g g man physicist, was born at Konigsberg (Prussia) on March 12, 1824, and was educated at the university of his native town. Af ter acting as Privatdozent at Berlin for some time, he became extraordinary professor of physics at Breslau in 1850. Four years later he was appointed professor of physics at Heidelberg, and in 1875 he was transferred to Berlin, where he died on Oct. 17, 1887. Kirchhoff's contributions to experimental and mathe matical physics were numerous and important. In his work in electricity Kirchhoff was greatly influenced by Weber. He modi fied the resistance bridge as designed by Wheatstone, and devel oped a theorem which gives the distribution of currents in a net work. Kirchhoff extended Ohm's theory for a linear conductor to the case of conductors in three dimensions, and so generalised the equations dealing with the flow of electricity in conductors. He also tried to establish a connection between electrostatic and electrodynamic conceptions of electricity. Another important piece of work was the demonstration that an electric disturbance is propagated along a wire with the same velocity as light is propagated in free space. In other papers, various miscellaneous topics were treated—the thermal conductivity of iron, crystalline reflection and refraction, certain propositions in the thermo dynamics of solution, vaporization and chemical reaction. An im
portant part of his work was contained in his V orlesungen jibe?. mat/iematische Physik (1876), in which the principles of dy namics, as well as various special problems, were treated in a somewhat novel and original manner.
His name is best known for the researches, in conjunction with R. W. von Bunsen on the development of spectrum analysis. He can scarcely be called an inventor, for not only had many investi gators already used the prism as an instrument of chemical in quiry, but considerable progress had been made towards the explanation of the principles upon which spectrum analysis rests. But to him belongs the merit of having, most probably without knowing what had already been done, enunciated a complete account of its theory and established the method on a solid basis. Kirchhoff gave the explanation of the Fraunhofer lines and thus opened up to investigation a new field in spectrum anal ysis applied to the composition of celestial bodies.
Kirchhoff's work is collected in Gesammelte Abhandlungen (Leipzig, 1882). See W. Voigt, Zum Geddchtniss von G. Kirchhoff (Gottingen, 1888).