## The mechanical calculator for all four arithmetic operations by Johann Jakob Sauter

This week we would like to introduce you to an especially impressive and aesthetically appealing mechanical calculator for all four arithmetic operations. It was built around 1796 by Johann Jakob Sauter from Esslingen, Germany. As the son of a watchmaker, he became - just like his siblings - a student of the scholar Philipp Gottfried Schaudt. Schaudt had earlier been working with Philipp Matthäus Hahn on his first mechanical calculator for all four arithmetic operations, the first calculator that was able to realize all tens carries with great precision and reliability in one single turn of a crank. The prototype used repeating components as features to store a number, a mechanism already used by watchmakers. With this component one could introduce a set number various times into the result mechanism. Said prototype got into the collection of a scholar named Beireis and was even presented to Goethe at some point. Due to the fact that the Bereis calculator got lost during WW2, for a long time it could not be explained how the repeating components worked in that calculator exactly. Only when the Sauter calculator was discovered at the City Museum of Gothenburg, Sweden, a detailed inspection of this unique mechanical construction was possible.

Sauter sold his mechanical calculator around 1804 to the Swedish royal house and took a post as royal mechanic and stayed in Sweden, too. At the Arithmeum we were given the opportunity to restore and inspect the original calculator in detail. We were able to build a functioning replica that can now be seen at the Arithmeum. Klaus Badur, Ingo Laubach and Ina Prinz built this replica as close to the original as possible. We would like to thank the City Museum of Gothenburg for their kind and loyal support! The restored and now functioning original of the calculator by Sauter is now part of the permanent exhibition there.

Since the fascinating functionality of the Sauter calculator can only be appreciated once we get to observe the working mechanism from the inside, Mario Wolfram created a 3D animation of the machine that provides these insights. Watching the following video you might be able to comprehend why this calculator is considered one of the most beautiful mechanical calculators of all times.