Vannevar Bush's Differential Analyzer

The first (relatively) large scale analog computer was the 'differential analyzer' invented and constructed by Vannevar Bush (1980-1974) in the early 1930's. The machine was a completely mechanical assembly of gears and shafts driven by electric motors. The picture alongside shows Bush and his differential analyzer in a U.S. Army laboratory during World War II.

The Bush differential analyzer is pictured in the science fiction movie Earth vs. the Flying Saucers (Columbia Pictures 1956, now available on dvd in the Ray Harryhausen Signature Collection). It is a very short take, only a few seconds, and I doubt whether the machine was really capable of producing handwriting.... Click here to see and hear the Bush DA working.
An even better take (in colour) of the differential analyzer appears in When Worlds Collide (George Pal 1951), also available on dvd.

The pictures were reproduced from IEEE Spectrum, July 1995.