**Julius Weingarten** was a German mathematician best known for the Weingarten equations in the differential geometry of surfaces.

- Weingarten attended the Municipal Trade School in Berlin.
- At the University of Berlin Weingarten attended lectures on potential theory given by Dirichlet.
- These lectures were particularly inspiring and, although this would not be Weingarten's main area of research, he continued to work, from time to time, on problems related to this topic throughout his career.
- The work was of such quality that Weingarten received a prize for work on the lines of curvature of a surface in 1857.
- The only class of such surfaces known before Weingarten consisted of the developable surfaces isometric to the plane.
- In 1863 Weingarten was able to make a major step forward in the topic when he gave a class of surfaces isometric to a given surface of revolution.
- Surfaces of constant mean curvature or constant Gaussian curvature are now called the Weingarten surfaces.
- Having produced work of outstanding quality, while one must remember he was teaching in schools, it would be reasonable to expect that Weingarten would find a good academic post.
- Weingarten had to take the option which would provide him with an income so he accepted a rather unsatisfactory position at the Bauakademie in Berlin.
- Weingarten was promoted to professor at the Bauakademie in 1871 but left the rather unsatisfactory post to take on what was another rather unsatisfactory position at the Technische Hochschule in Berlin.
- Weingarten's work on the infinitesimal deformation of surfaces, undertaken around 1886, was praised by Darboux who included it in his four volume treatise on the theory of surfaces.
- Darboux said that Weingarten's work was worthy of Gauss, a compliment indeed.
- The interest which Darboux showed in his work, encouraged Weingarten to push his results further and he wrote a long paper which won the Grand Prix of the Académie des Sciences in Paris in 1894.
- The work was published in Acta mathematica in 1897 and was another major step forward in solving the problems on which Weingarten had worked all his life.
- Darboux was not the only leading mathematician in Weingarten's time who was also interested in the theory of surfaces.
- Another was Bianchi and a major correspondence grew up between Weingarten and Bianchi.

Born 2 March 1836, Berlin, Germany. Died 16 June 1910, Freiburg im Breisgau, Germany.

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Origin Germany

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive