 In 1894 he returned to teaching at the Technical University of Berlin and the following year he obtained his "venia legendi" at the University of Halle where he taught as assistant professor till 1899.From 1899 to 1905 he was full professor at the university of Jena.In 1905 he returned to Halle University (succeeding Georg Cantor) where he remained till his death in 1924.