sentences:  He became a teaching authority as a senior primary school teacher (pro facultate docendi) on 26 February 1869 for his chosen courses.After a probationary year 1869/1870 at the high school of Bonn, he worked at the high school of Krefeld (at least to 1878) and then at the Realprogymnasium in Bonn.In the hope to be able to change to a high school career at the mathematical faculty at the University of Bonn he sent a habilitation document.