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de Prony Produces Mathematical Tables Calculated by Hairdressers Unemployed after the French Revolution

1793 to 1801

French mathematician and engineer Gaspard Clair François Marie Riche de Prony, Engineer-in-Chief of the École Nationale des Ponts et Chaussées, undertook, beginning in 1793, the production of logarithmic and trigonometric tables for the French Cadastre. He was asked to produce the tables by the French National Assembly, which, after the French Revolution, wanted to bring uniformity to the multiple measurements and standards used throughout the nation. The tables and their production were vast, with values calculated to between fourteen and twenty-nine decimal places.

Inspired by Adam Smith's Wealth of Nations, de Prony produced the tables through the systematic division of labor, bragging that he could manufacture logarithms as easily as one could manufacture pins. At the top of the organizational hierarchy were scientists and mathematicians who devised the formulas. Next were workers who created the instructions for doing the calculations. At the bottom were about ninety human computers who were not trained in mathematics, but who followed instructions very carefully. De Prony found that hairdressers unemployed after the French Revolution, who were meticulous by nature, made excellent human computers. In spite of the division of labor it took eight years for the tables to be completed, and because of the inflation during the French Revolution the tables were never published in full. Portions were published for the first time in 1891.    

Though the tables remained unpublished the manuscripts could be examined and consulted. De Prony's method of production of the tables inspired Charles Babbage in the design of his Difference Engine No. 1 in 1822.

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