At the head of these new discoveries and insights comes the establishment of the facts that electricity is composed of discrete particles of equal size, or quanta, and that light is an electromagnetic wave motion.

Die elektrischen Quanten. Career
Stark worked in various positions at the Physics Institute of his alma mater until 1900 when he became an unsalaried lecturer at the University of Göttingen. (Sonderabdruck aus 'Annalen der Physik' 4.