The Doodson-Légé Tide Predicting Machine

I was watching the BBC show Coast last night, an episode all about the ebb and flow of tides, called Riddle of the Tides. It showcased a beautiful analog computer called the Doodson-Légé Tide Predicting Machine. Dr. Arthur Doodson, got his PhD for perfecting a method of making accurate tidal predictions, a task that is much harder than you may think, involving around 120 variables. His method was used to predict the tides for the Normandy landings on D Day in WWII. A machine was designed to mechanise the process in 1948/9, built by a Liverpool engineering firm, Légé. It remained in use until it was replaced by computers in 1962. The machine can be seen at the Bidston Observatory of the  National Oceanography Centre Liverpool.