Thomas’ arithmometer is a mechanical calculating machine designed to perform four basic arithmetical operations: addition, subtraction, multiplication and division. This machine was invented by the Frenchman Thomas de Colmar in 1820.
It was strong enough and reliable enough to be used daily in an office environment.
This is the first calculating machine that was commercialised and manufactured in large quantities. The arithmometer dominated sales of calculating machines during the second part of 19th century.
All his life Thomas de Colmar was improving the machine. When he died in 1870, his son Thomas de Bojano, and later engineer Louis Payen, continued improvements and the production. It was eventually cloned by numerous European manufacturers.
In 1915 Alphonse Darras attempted to continue production but the war and especially existence of much cheaper and better performing machines stopped his efforts.