Subsequently, he spent three years at different universities in Germany, at first in Munich, then Jena, Berlin, and finally Göttingen, where he attended the lectures of German historian Georg Waitz and where he finished his PhD thesis on Count Ernst von Mansfeld in Bohemia in October 1864.

[3] He earned a Dr.Phil "summa cum laude" in December 1864, and subsequently returned to Strasbourg, where he became a teacher at the Jean Sturm Gymnasium in 1865.

After the Franco-Prussian War he resumed his position as teacher, retired however from the Protestant seminary when the Kaiser-Wilhelms-Universität was founded in 1872 and became librarian at the Strasbourg library.

[4] He then moved to Versailles, close to Paris, where he was appointed professor at the École des hautes études in June 1896.

He gave lectures there two times a week for 26 years, while living with his family in Versailles.