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Edmondson's Circular Calculating Machine

Edmondson's Circular Calculating Machine
This machine, which was designed and patented by Joseph Edmondson in 1883, is a modification in circular form of the straight arithmometer of the Thomas type. Eight number slides are placed radially on the outer fixed portion of the machine. The hinged slide of the straight type of machine is replaced by a circular plate, carrying 20 figure discs, each of which - depending on its position relative to the number slides and driving handle, respectively - can serve either for recording the result in multiplication or for setting the figures of the multiplier. "Stepping" is performed by lifting this plate, rotating it through one-twentieth of a revolution, and lowering it again. To multiply, the figures of the multiplier are set on the middle plate and those of the multiplicand on the slides. The handle is then turned and the plate "stepped" clockwise until all the digits of the multiplier have been brought to zero. The product then appears in the apertures on the middle plate.