Amsler-Laffon, Jakob (1823–1912)

Swiss mathematical physicist who designed and manufactured precision instruments for use in engineering, including an improved tool to measure areas inside curves – the polar planimeter.

Amsler was born in Stalden bei Brugg, Valais, and studied mathematics and physics at Königsberg, Germany. He took up the design and manufacture of scientific instruments in Schaffhausen in 1854.

Earlier models of tools to measure the surface of spheres had been based on Cartesian coordinates, but they were bulky and expensive. Amsler-Laffon's design, based on a polar coordinate system, was not only more delicate and flexible than its predecessors, but was also much cheaper to manufacture. It was particularly valuable to shipbuilders and railway engineers. By the time he died, his factory had produced more than 50,000 polar planimeters.