Kelvin's second tide predictor, 1873.

Kelvin's second model for a tide-predicting machine, 1873

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 for the harbour. On cranking the handle, the machine calculates the harbour's tidal patterns for up to a year, in only four hours.