Inventor of the modern slide rule, Mannheim standardized the design that remained in common use until pocket calculators took over.
After graduating from the École d'Application in Metz, Mannheim became an officer of the French artillery. It was while he was a student at the École d'Application that the ideas for the slide rule came to him. He invented what may be considered the first of the modern slide rules around 1850. This was a new scale system that used a runner to perform calculations.
The Mannheim rule, which also brought into general use a cursor, or indicator, was much used in France, and after about 1880 it was imported in large numbers into other countries. Although slide rules existed before his time, invented by Oughtred and Gunter and others, it was Mannheim who standardized the modern version of the slide rule, which remained in common use until pocket calculators took over.
After several years in the military, he was appointed to the École Polytechnique in Paris, while continuing his army career. In 1864 he was appointed as Professor of Descriptive Geometry at the École Polytechnique. Mannheim retired from his army post in 1890, having attained the rank of colonel in the engineering corps. He continued teaching at the École Polytechnique until he retired in 1901 at the age of 70.
He made numerous contributions to geometry, and for his outstanding contributions to the subject he was awarded the Poncelet Prize of the Académie des Sciences in 1872. Mannheim studied the polar reciprocal transformation introduced by Chasles and applied his results to kinetic geometry. His own definition of kinetic geometry considered it to be the study of motion of a figure without reference to any forces, time, or other properties external to the figure. He also studied surfaces, in particular Fresnel's wave surfaces.
