Amedee Mannheim, French mathematician, c 1901.

Amedee Mannheim (1831-1906) developed the standardised modern version of the slide rule that was used up until the invention of calculators. Mannheim simultaneously had an army career whilst teaching mathematics and chemistry at the Ecole Polytechnique. Mannheim retired from his post at the Ecole Polytechnique in 1901, this photograph commemorates his time there.