Ideas for Visual Time Signals

The first ideas for land-based visual time signals controlled by astronomical observations that could be used to rate marine chronometers have been credited to Robert Wauchope. Time guns had often been used previously but they were not then precision signals. The principal aim of this chapter is to demonstrate how the dropping time ball was introduced as the preferred time signal, following Wauchope’s first suggestion of a shutter signal in 1818. He later proposed the hauling down of a flag at noon. The Admiralty changed this signal to a dropping ball at 1 pm which was trialled at Portsmouth in 1829 and favoured by Wauchope thereafter. He continued to press the Admiralty and other authorities worldwide to introduce time balls, finally succeeding with the time ball at Greenwich. Preceding independent solutions included a shuttered oil lamp and a shuttered time ball or disc. The expansion of time balls and other signals for mariners is also discussed.