Integrators and Integraphs

Instruments for measuring the area under a curve (integrators) and for drawing a curve representing that area (integraphs) date from the nineteenth century and were used well into the twentieth century. Vannevar Bush even designed an integraph that could plot the value of the integral of the product of two functions. Techniques used in planimeters and integraphs would be adopted in more complicated mechanical integrators such as differential analyzers.