Thomas Arithmometer

This stepped drum, manual non-printing calculating machine has a brass mechanism that fits well in a wooden case. Eight levers slide up to enter digits. A stepped drum is below each lever. The brass plate that covers the drums and top of the machine has slits in it to allow these and other parts to move. The edges of the slits next to digit levers are numbered from 0 to 9 to indicate the digit entered. A lever to the left of these is either pushed up for addition and multiplication or down for subtraction and division. Further to the left is a slate-covered compartment. An operating crank is right of the digit levers. It has an ivory handle, which bends down so that the lid closes.

Behind the levers is a movable carriage that can be set in seven different positions. It has nine windows for the revolution register and 16 windows for the result register. The revolution register turns clockwise for subtraction and division, and counterclockwise for addition and multiplication. A knob for zeroing the revolution register is on the right of the carriage, and a lifting knob on the left. Rotating thumbscrews allow one to enter numbers in both the revolution and the result registers. Holes for decimal markers are between the windows of the register, but no decimal markers survive.

A mark to the left of the levers reads: THOMAS de Colmar (/) A PARIS (/) INVENTEUR (/) No. 787. A nearby mark reads: ADDON ET MULTON (/) SOUSTON ET DIVISON. The frame of the slate is stamped on the bottom: ASTRONOMICAL OBSERVATORY (/) COLUMBIA (/) UNIVERSITY (/) NEW YORK.

Frederick A. P. Barnard, the president of Columbia University, purchased this machine at the Paris Exposition of 1867. He used it in preparing a report on the exposition and later transferred it to the Astronomical Observatory at Columbia.

Compare MA.323658.

Reference:

P. A. Kidwell, “Scientists and Calculating Machines,” Annals of the History of Computing, 12, 1990, pp. 31–40.

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