The cylindrical calculating machines of the clergyman Philipp Matthäus Hahn (1739-1790) were the first fully functional four-species mechanical calculating machines. The construction principles of Hahn were continued by his apprentices Jakob Auch (1765-1842) and Johann Christoph Schuster (1759-1823), and by his old friend and schoolmate Gottfried Schaudt (1739-1809), who in turn passed on his knowledge to the brothers Sauter from Esslingen. Until recently it was not known whether the brothers Sauter built any calculating machines. Thus it came as a great surprise when an intact and nearly fully functional machine built by Johann Sauter (born 1770) was discovered in the City Museum of Göteborg, where it had lain unnoticed for nearly 150 years.

A visit to the museum and their permission to take the machine apart, measure it up and study its functioning, revealed many new insights into the mechanical representation of numbers in calculating machines and their constructional details. This lecture will present the results of these investigations. Technical details of the machine, which place it historically at the end of the 18. or the beginning of the 19. century, will be elucidated and illustrated by means of numerous pictures and videos which will make the lecture very interesting and fully accessible to a non-specialist audience.

Open Lecture on the "Dies Academicus" in the Gerhard Konow Lecture Hall in the Arithmeum