Physicist (mathematical physics, atomic physics, theoretical physics, wave mechanics, quantum mechanics). On the mineralogy faculty at Georg-August Unviersitt̃ zu Gt̲tingen (1893-1897); on the mathematics faculty at Technische Unviersitt̃ Clausthal (1897-1900); on the mechanics faculty at the Technische Hochschule zu Aachen (1900-1906); and on the physics faculty at Universitt̃ M nchen from 1906.