In addition to the task of pointing ships into the channel, the lighthouse also signaled ships about the state of the tide. During the day this was performed using two day signals installed on two corners of the structure, while during the night two 6th order dioptric lights showing different colors coded the state of the tide. The different colours were changed manually, by lowering glass cylinders over the lanterns, which could be done from inside the structure. Records of the tide were also kept automatically by floats in tubes which graphed the tide level. The graphs were replaced every month and were sent to Greenwich where they were kept.