# 1911 Encyclopædia Britannica/Kirchhoff, Gustav Robert

**KIRCHHOFF, GUSTAV ROBERT** (1824-1887), German
physicist, was born at Königsberg (Prussia) on the 12th of
March 1824, and was educated at the university of his native
town, where he graduated Ph.D. in 1847. After acting as
*privat-docent* 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 the 17th of October
1887. Kirchhoff's contributions to mathematical physics were
numerous and important, his strength lying in his powers of
stating a new physical problem in terms of mathematics, not
merely in working out the solution after it had been so formulated.
A number of his papers were concerned with electrical
questions. One of the earliest was devoted to electrical
conduction in a thin plate, and especially in a circular one, and it
also contained a theorem which enables the distribution of
currents in a network of conductors to be ascertained. Another
discussed conduction in curved sheets; a third the distribution
of electricity in two influencing spheres; a fourth the
determination of the constant on which depends the intensity of
induced currents; while others were devoted to Ohm's law,
the motion of electricity in submarine cables, induced
magnetism, &c. In other papers, again, various miscellaneous
topics were treated — the thermal conductivity of iron, crystalline
reflection and refraction, certain propositions in the
thermodynamics of solution and vaporization, &c. An important
part of his work was contained in his *Vorlesungen über*
*mathematische Physik* (1876), in which the principles of dynamics,
as well as various special problems, were treated in a somewhat
novel and original manner. But his name is best known for
the researches, experimental and mathematical, in radiation
which led him, in company with R. W. von Bunsen, to the
development of spectrum analysis as a complete system in
1859-1860. He can scarcely be called its inventor, for not only
had many investigators already used the prism as an instrument
of chemical inquiry, 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 of thus having firmly
established it as a means by which the chemical constituents
of celestial bodies can be discovered through the comparison
of their spectra with those of the various elements that exist
on this earth.