The MONIAC or Phillips machine is a hydromechanical analog computer built to teach basic economical principles using colored water flowing in transparent pipes. The machine was built in 1951 after electrical-engineer-turned-economist William Phillips and his economist colleague Walter Newlyn realized that flows were used as a metaphor to teach economics, but have never been made physical. Phillips is also known for his eponymous curves. Several MONIACs were built, and a working one is permanently displayed at the Economics Department of Cambridge University. Sources: Bissell (2007) The Moniac: A Hydromechanical Analog Computer of the 1950s. The museum of the Reserve Bank of New Zealand also has a working MONIAC and a Youtube video explaining it. Image from fulltable.com. Morgan & Boumans (1998) The Secrets Hidden by Two-Dimensionality: Modelling the Economy as a Hydraulic System. The original article by the creator of the machine: Philips (1950) Mechanical Models in Economic Dynamics.