## Adding machine by Philipp Matthäus Hahn

Besides his main profession as a clergyman, Philipp Matthäus Hahn (1739-1790) also ran a workshop where he designed watches and astronomical clocks, the construction of which needed time-consuming mathematical operations to be solved without mistakes. One day, he wrote: “Today, 10 pm, I miscalculated again: I will now build a calculating machine!” And so he invented a calculating machine that worked perfectly at every digit’s position with just a single turn of the crank.

He also built simpler adding machines. His workshop books prove that he manufactured three adding machines. They were regarded missing for a long time, until one machine showed up in an auction in England in 1998. This piece is now part of the Arithmeum collection. Stefanie Juchmes, student of Computer Science, made a wonderful 3D animation of this adding machine as a work project. The mechanism of this small, but lovely machine can be understood quite well from this video. Enjoy your discovery of this unique gem.