Dr. Harold Locke Hazen

Mechanical integrators for differential equations were designed by the Italian mathematician Ernesto Pascal, who called them "integrafi", and published details in 1914. However, the first widely practical version of such a machine was constructed by Harold Locke Hazen and Vannevar Bush at MIT, 1928?1931, comprising six mechanical integrators. In the same year, Bush described this machine in a journal article as a "continuous integraph". When he published a further article on the device in 1931, he called it a "differential analyzer". In this article, Bush stated that "[the] present device incorporates the same basic idea of interconnection of integrating units as did [Lord Kelvin's]. In detail, however, there is little resemblance to the earlier model." According to his 1970 autobiography, Bush was "unaware of Kelvin?s work until after the first differential analyzer was operational."