Arithmometer - Variants

Variants

In 1885, Joseph Edmondson of Halifax, UK, patented his 'Circular Calculator' - essentially a 20-digit arithmometer with a circular carriage (the slides being arranged radially around it) instead of the straight sliding carriage. One benefit of this was that the carriage always remained within the footprint (to use a modern term) of the machine instead of overhanging the case at one side when the higher decimal places were in use. Another was that one could make a calculation of up to ten places, using half the circumference of the carriage, and then turn the carriage through 180°; the result of the calculation was locked in place by means of brass prongs mounted on the framework, and one could leave it there while making an entirely new calculation using the fresh set of display windows now brought into alignment with the sliders. Thus the machine could be said to have a rudimentary memory. See the Rechenmaschinen-Illustrated website (External Links below) for pictures and a description.