A schematic diagram of the Phillips water computer, built in the 1940s to model the British economy, in Like Water for Money, a guest post by Steven Strogatz in the New York Times “The Wild Side” blog. It’s a good read, too. (via)
I’m always happy to see people come across this rather charming, if slightly impractical, analogue computer. I also hadn’t realised there was one in Cambridge (in working order, no less); I know of it from the (non-functional, sadly) example in the Science Museum’s computing gallery.