The ancestors of the pocket calculator

The HNF is showcasing two very rare computing devices from the 17th and 18th centuries.

Machine arithmétique de Grillet

The “Machine arithmétique de Grillet”, made in 1678, is in particularly good condition. Only one other example is known to exist, and it is on display at the arts et métiers in Paris.

The device was made by René Grillet, the royal watchmaker of Ludwig XIV. It is an outstanding example of the beginnings of mechanical calculation. Grillet published a brief description with a copper engraving that appeared in the first European scientific magazine “Le Journal des Scavants” in 1678. His invention was based on a calculation process involving Napier’s rods, which had been in use since 1617.

The wooden box contains five cylinders designed according to the principle of Napier’s rods and used for multiplication and division, plus two more cylinders for squaring and calculating cubic numbers. In the lid of the box, Grillet installed 24 small paper discs that display numbers. They are used to add the partial result produced by Napier’s rods. The very meticulous number discs appear to have been rarely used during the past 335 years: they are in exceptionally good condition.

Unlike the Pascaline, one of the calculating machines built in 1642, Grillet’s device has no decimal carry or mechanical wheelwork. With a format of 14.5 x 32.5 x 5 cm and a weight of 990 grams, it is particularly compact. As a result, this portable device can be regarded as the forefather of pocket calculators.

Schott computing box

In 1668, the mathematician and Jesuit Caspar Schott published a design for a calculating device that was likewise based on Napier’s rods. The device displayed at the HNF is based on Schott’s description and was made around 1780. The name of the manufacturer is unknown. It helps multiply and divide eight-digit figures. The box is made of walnut and oak. The dials are made of ivory. Brass trim serves as decoration.