More than three centuries ago, the Parisian physician and polymath Claude Perrault devised a fascinating small mechanic calculator, Abaque Rhabdologique. In the 1699 issue of the journal Le Journal des sçavants, Perrault explained that the name of his machine was derived from the mathematical practice of the ancients, who had used tablets (abacuses) to write numbers, and who had the capacity to perform many arithmetic operations by employing small rods marked with digits (rhabdology).
Subsequently, many mathematicians and inventors have improved, and re-shaped, Perrault’s ingenius machine. As an heir of this tradition, Troncet created what he called the Arithmographe. Essentially, it is a small stylus-driven metal calculator consisting of flat metal bands with notched edges pointing at numbers from one to nine. To be precise, these metal bands are hidden behind seven cane-shaped columns. The user needs to move these bands with the stylus to enter numbers. As seen in the image above, the device also included a small pamphlet with instructions and mathematical tables.
For instance, imagine that you want to do a simple addition: 24 plus 57. This is the way you do it by using our Arithmographe Troncet. Insert the stylus in the hole on the right side of each digit to be added, starting always in the right column to insert the units of each number. Next, slide the stylus all the way up or down depending on whether the number to be added is opposite to a white or red column respectively.
And here you have the result!
Troncet’s invention became enormously popular: the calculator was in production for more than 30 years!