Polar planimeter in case, 1894

Planimeter in case by G. Coradi, Zurich. 1894

A planimeter made by G Coradi, Zurich, Switzerland, 1894. A planimeter measures the area bound by a closed curve. Scientists and engineers used them to perform integration and they are used to measure maps, plans and the area or volume of engineering components. In the instance of an area on a map the anchor end of two hinged rods is fixed whilst the end of the other rod traces the boundary line of the area to be measured. Planimeters were one of several devices for carrying out mathematical operations that sold widely in the late 19th century and used up to the first half of the 20th century.