Thomas Arithmometer

This manual, non-printing stepped drum calculating machine has a brass mechanism that fits snugly in a wooden case. Eight levers moved 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 number 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 glass-covered compartment. Right of the digit levers is an operating crank with an ivory handle that bends down so that the lid closes.
Behind the levers is a movable carriage with 9 windows for the revolution register and 16 windows for the result register. A crank for zeroing the revolution register is on the right of the carriage. A lifting knob and a crank for zeroing the result register are on the left. Rotating the thumbscrews enters numbers in both the revolution and the result registers. Holes for decimal markers are between the windows of the registers. There is one brass decimal marker. The bottom of the case is covered with green felt. Holes in the sides of the case allow the carriage to move.
A mark at the center reads: THOMAS de Colmar, INVENTEUR (/) S’adresser (/) 44, RUE DE CHATEAUDUN, 44 (/) PARIS (/) No 1372 (/) EXPOSITION, 16. RUE DE LA TOUR DES DAMES. A mark on the carriage reads: PRUDENTIAL (/) ASSURANCE COMPANY, LTD. A mark inside the lid: TIM & UNITAS (/) CALCULATING MACHINES (/) GEORGE SPICER (/) Market Place, Brentford. (/) PHONE EALING 2020. It is marked on top of the lid: Arithmomètre.
The Frenchman Charles Xavier Thomas of Colmar (1785-1870) patented his first calculating machine in 1820. He made major changes to the mechanism at mid-century, and the Thomas arithmometer became the first commercially successful calculating machine. After Thomas died, his firm was taken over by his longtime associate Payen, who made some modifications. Payen began selling arithmometers under his own name and, in 1908, following his own design. This machine is one made after Thomas’s death in his style. The Prudential Assurance Company was an important early British user of arithmometers. This machine passed from the Prudential into the collections of Felt & Tarrant Manufacturing Company of Chicago and from there to the successor firm of Victor Comptometer Corporation.
Compare MA*327900.
Stephen Johnston, “Making the Arithmometer Count,” Bulletin of the Scientific Instrument Society, #52 (1997) refers to several arithmometers that were in use at the Prudential by 1872.
Stephen Johnston, Personal Communication, indicates that this machine was acquired by the Prudential in 1876.
Currently not on view
Object Name
calculating machine
date made
Thomas, Charles Xavier
Physical Description
brass (overall material)
wood (overall material)
steel (overall material)
ivory (overall material)
felt (overall material)
overall: 10 cm x 59 cm x 18 cm; 3 15/16 in x 23 7/32 in x 7 3/32 in
place made
France: Île-de-France, Paris
ID Number
catalog number
accession number
maker number
Science & Mathematics
Calculating Machines
See more items in
Medicine and Science: Mathematics
Calculating Machines
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Victor Comptometer Corporation
Additional Media

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