Visual Time Signals for Mariners Between Their Introduction and 1947

The worldwide evolution of visual time signals for mariners during the period up to 1947 is explored in this paper. The emphasis is on their external appearance and how they were regarded by mariners for rating chronometers. The first accurate signals were established by the 1830s and the number of different locations increased steadily throughout the nineteenth century. The signals included time balls and time guns as well as many other devices under control by an astronomical observatory. By 1880, signals were widely distributed, although some earlier signals had been either withdrawn or replaced. Lists of signals prepared by the British Admiralty from 1880 onwards provide a record of over 200 visual signals for mariners that is reviewed for the first time in this study. The lists did not include time signals that were inland and unavailable to mariners, nor did they include signals of unknown veracity at minor ports. The lists did indicate when signals might be unreliable. Some locations used more than one type of signal. Results are presented in a series of tables for different geographical areas, colour coded by signal type for selected years. These are complemented by maps showing locations listed between 1880 and 1947, indicating the type of signal that existed at the time of withdrawal or in 1947 if it was still extant. Although wireless time signals were widespread after 1920, visual signals continued to be provided at many locations worldwide and a significant number were still extant or re-established after the end of the Second World War. The total number of listed visual signals reached 220 in 1922 and declined to 64 in 1947. There were 53 listed time balls in 1880, 129 in 1919, 69 in 1939 and 26 in 1947. Electric time lights first appeared as principal signals in 1909 and replaced or complemented many time balls, giving a maximum of 41 light signals in 1934. The largest number of listed time guns was 49 in 1915

Astronomy · Cartography · Geography · Physics · Computer Science · History · History and Developments in Astronomy · Artificial Intelligence

• Italic>The World of Visual Time Signals for Mariners

  Open Access•Steven J Dick•Journal of Astronomical History…•2024

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