History of Computers and Computing, Mechanical calculators, 18th century, Jacob Auch

The Adding Device of Jacob Auch

The German Jacob Auch (1765-1842) was a very good mechanic and clock-maker (see biography of Jacob Auch), interesting for us with his remarkable calculating machine.

Auch was born in Echterdingen. In the same town, from 1781 till 1790 served Philipp Matthäus Hahn. The young Jacob was an apprentice of Hahn and used to work in his workshop in Echterdingen. From 1787 till 1798 Auch opened and worked in his own workshop in Vaihingen an der Enz and Karlsruhe, and from 1798 till 1842 he was hired as a ducal mechanic (Großherzoglichen Hofmechanicus) at the Weimar court.

In 1790, while in Vaihingen an der Enz, Jacob Auch made an adding machine of a very good workmanship. He was probably inspired by the machine of his mentor Hahn, but its construction is completely different.

Two machines survived to our time—one in Württembergisches Landesmuseum in Stuttgart (see the lower images), the other in Matematisch-Physikalischen Salon in Dresden.

The calculating machine of Jacob Auch (© Württembergisches Landesmuseum Stuttgart)

The dimensions of the machine of Auch in Stuttgart are: 22,8 x 6,1 x 1,9 cm. It is made of brass and was placed in a wooden case.

The machine of Auch has 8 digital wheels, 7 of them are decimal, and 1 (the second from the right) is divided to 12 parts. The graduation of the disks was made according to the monetary system adopted throughout the southern states of the Holy Roman Empire in 18th century (60 Kreuzer = 1 Gulden). The two rightmost wheels are used for calculations in Kreuzer (12 x 10), others (decimal) are used for Gulden. Entering of the numbers can be done by means of a stylus.

At the lower left corner of the box is inscribed an instruction for work in German: use black to add and red to subtract. This means, that the internal calculating mechanism is unidirectional, the wheels can be rotated only in clockwise direction, and subtraction can be done, using the method complements of 10. The machine has also tens carry mechanism.