Concluding Remarks

Shore-based visual signals were the means used to check the accuracy of the time indicated by marine chronometers. The dropping time ball was the most popular visual signal for over a century, but there is still uncertainty about its original selection and key documents concerning its development have yet to be found. Admiralty lists of signals and postcard images show the recognised locations of signals for mariners, but there are errors of description and uncertainties about dates of introduction and withdrawal that need to be clarified. There also uncertainties about signal types, some arising from the use of “time-ball” as a generic term for time signals, while the specifications and suppliers of apparatus have yet to be identified in many cases. Archives in different countries may reward close investigation and there is much scope for international historical research. This book provides an initial framework, indicating the number and variety of visual time signals that had existed in the nineteenth and twentieth centuries.