Captain Inglis and his Tide Machines: The dodging tides of Port Adelaide, from South Australia to the Pacific War at Tarawa

The confusing tides of Port Adelaide in South Australia periodically appeared to barely move, earning them the local name ‘dodging tides’ and restricting maritime traffic to high water. The harbour master from 1881, Captain Inglis, and a mathematician, Professor Chapman, combined to observe and analyse the tides, rendering them predictable by harmonic analysis. By the turn of the century Inglis had invented a machine that enabled more efficient prediction of Port Adelaide’s tide and was far cheaper than the complex analogue computers used in Europe. At a time when there were globally only ten functioning tide prediction machines (TPMs), Inglis’s machine provided a relatively simple bespoke solution for a colonial port. As this machine could predict tides at only one port, and only Inglis knew how to use it, and tide tables were becoming readily available from other sources, the Inglis TPM fell into disuse on his death in 1921. Nevertheless, local lore of the dodging tide left a legacy at Tarawa in 1943 during the Pacific War when mariners asked to predict the tide based on memory recalled familiarities with the phenomenon at Port Adelaide. The unique Inglis TPM, donated to a museum in 1922, is now missing.