A typed postcard, signed H. Geiger, Tübingen, 24th December 1929.

1929. A personal postcard, typed address to recto with the inkstamps of the "Physikalisches Institut Universität Tübingen", Tübingen postal cancel, typed to verso and signed in a clear hand, writing in a clerical hand to the verso, in very good condition. Geiger is known for such technical achievements as the Geiger-Marsden experiment and the Geiger counter. In October, 1929, he accepted a position at the University of Tübingen, both as professor of physics and director of the physics research institute. While there, he considerably improved the counter that bears his name, developments that were to lead to the discovery of cosmic-ray showers. This postcard, sent by Geiger from Tübingen to the business firm K. Selmayr, orders "eine Grundserie von Kristall-Gitter-Modellen mit 30 mm Kugeln" (a basic series of crystal-lattice models with 30mm spheres").