He wrote also on Armenian mythology.[1] He was the son of the Swiss historian Johann Heinrich Gelzer (1813–1889). He became Professor of classical philology and ancient history at the University of Jena, in 1878. He wrote a still-standard work on Sextus Julius Africanus.[2] He worked out the chronology of Gyges of Lydia, from cuneiform evidence, in an 1875 article.[3]