The adding machine by Charles Xavier Thomas de Colmar, whose patented model of the Arithmométre four-species calculating machine we presented here a few weeks ago, was patented in 1849. It differs from all previous adding machines due to the star-shaped engravings on the brass top plate. These engravings on the surface are not decorations, but serve as a guide for setting. The setting lever is used to enter a number, which is then displayed on parchment disks in the result unit.

The ten's carry is realized via a single tooth, which engages in the transfer gear of the next digit as soon as the 9 in the resulting gear turns to a 0. The different arrangement of the components in their respective layers prevents an unintended transfer of tens from being triggered.

Students Evelyn Lippmann and Tim Vellmer animated the addition machine described above as part of Professor Dr. Ina Prinz's “History of Mechanical Computing” lecture. This reveals details that would remain hidden to the visitor when viewed from the outside.
We hope you enjoy this new “Calculating Machine of the Week”.