Vannevar Bush, an engineer who did much of his work in the mid-twentieth century, is especially well known for his proposal of the memex, a machine that in many ways predicted the world wide web, and for his series of differential analyzers, which were analog computers that saw a great deal of military and scientific use through the 1950s.
The development of the Vannevar Bush series of differential analyzers took place in the 1930s, in order to satisfy that era's increased demand for scientific calculation. The machines were very similar to a theoretical analog machine designed by Lord Kelvin in the late 1800s, though Bush denied knowledge of Kelvin's work prior to completing his design. In any event, although Thomson first put forth the design that would later be realized in the Bush Differential Analyzer (that of chaining n first-order differential analyzers to solve a differential equation of nth degree), he cannot be fully credited for the invention, since he was unable to build a working model. Therefore, Vannevar Bush and his assistant Harold Hazen (who colloborated with Bush to develop the servomotor that allowed the machines to be linked) share credit for developing the first differential analyzers capable of solving differential equations of second degree or greater.
Though Bush's differential analyzers were useful tools for calculation, they were in many ways limited by their technology. Difficulties due to the machine's mechanical nature, as well as the problem of configuring the machines for different problems, eventually led to their being replaced by newer, cheaper, and more readily adaptable computing technologies. Despite this, Bush's Differential Analyzers mark an important milestone in computing history. They were powerful general-purpose analog computers, and the interest they generated in general purpose computing was one of the factors that drove the computer industry onto the path that led to modern day computing.
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