Christoffel was born on 10 November 1829 in Montjoie (now
Monschau) in
Prussia in a family of cloth merchants. He was initially educated at home in languages and mathematics, then attended the Jesuit Gymnasium and the Friedrich-Wilhelms
Gymnasium in
Cologne. In 1850 he went to the
University of Berlin, where he studied mathematics with
Gustav Dirichlet (which had a strong influence over him) among others, as well as attending courses in physics and chemistry. He received his doctorate in Berlin in 1856 for a thesis on the motion of
electricity in homogeneous bodies written under the supervision of
Martin Ohm,
Ernst Kummer and
Heinrich Gustav Magnus. After receiving his doctorate, Christoffel returned to Montjoie where he spent the following three years in isolation from the academic community. However, he continued to study mathematics (especially mathematical physics) from books by
Bernhard Riemann, Dirichlet and
Augustin-Louis Cauchy. He also continued his research, publishing two papers in
differential geometry. In 1859 Christoffel returned to Berlin, earning his
habilitation and becoming a
Privatdozent at the University of Berlin. In 1862 he was appointed to a chair at the
Polytechnic School in Zürich left vacant by
Richard Dedekind. He organised a new institute of mathematics at the young institution (it had been established only seven years earlier) that was highly appreciated. He also continued to publish research, and in 1868 he was elected a corresponding member of the
Prussian Academy of Sciences and of the
Istituto Lombardo in Milan. In 1869 Christoffel returned to Berlin as a professor at the Gewerbeakademie (now part of
Technische Universität Berlin), with
Hermann Schwarz succeeding him in Zürich. However, strong competition from the close proximity to the University of Berlin meant that the Gewerbeakademie could not attract enough students to sustain advanced mathematical courses and Christoffel left Berlin again after three years. In 1872 Christoffel became a professor at the
University of Strasbourg, a centuries-old institution that was being reorganized into a modern university after Prussia's annexation of
Alsace-Lorraine in the
Franco-Prussian War. Christoffel, together with his colleague
Theodor Reye, built a reputable mathematics department at Strasbourg. He continued to publish research and had several doctoral students including
Rikitaro Fujisawa,
Ludwig Maurer and
Paul Epstein. Christoffel retired from the University of Strasbourg in 1894, being succeeded by
Heinrich Weber. After retirement he continued to work and publish, with the last treatise finished just before his death and published posthumously. Christoffel died on 15 March 1900 in Strasbourg. He never married and left no family. ==Work==