Kelvin's second tide predictor, 1873.
© Science Museum / Science & Society Picture Library
Designed by Lord Kelvin (1824-1907) to predict the tide pattern in harbours, this is a smaller version of his 1872 model. The two dials seen on the machine are set with the oceanographic and astronomical data of the harbour. On cranking the handle, the machine calculates the harbour's tide patterns for up to a year in only four hours.