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This machine, while an improvement of the Arithmometer made in 1820 by Thomas de Colmar (1785-1870), is essentially of the same type. Beginning in 1883, Tate modified the Thomas calculator, eventually selling his patents to the Layton Brothers. That firm brought out a commercial model in 1910 named the "Improved Arithmometer." As in the Thomas machine, the Layton incorporates the Leibniz stepped gear principle - multiplying by repeated addition and dividing by repeated subtraction. |
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