Time Signals for Mariners in SE Asia: Time Balls, Discs, Bells, Guns and Lights

Abstract

AbstractLand-based visual time signals for marine chronometer calibration were essential for navigation in the nineteenth and twentieth centuries, before the widespread introduction of radio time signals in the 1930s. The determination of longitude at sea required exact knowledge of the mean time at Greenwich, England, which is located on the internationally agreed prime meridian, as well as the local mean time. Visual signals that allowed checks on chronometer readings were located at principal ports worldwide. The most common signal was a time ball, dropped at a designated time each day. Observatories and signal stations in different countries were often interconnected by undersea telegraphs in the late nineteenth century. The exact locations and details of time signals were included in nautical almanacs and sailing instructions issued by various authorities. The aim of this chapter is to establish the locations and types of time signals for mariners that existed in SE Asia.The first time ball in SE Asia was established in Batavia in 1839 and there was later another in Surabaya. By 1880, these had been superseded by signals using one or more time discs. The largest assembly of time signals was in Singapore, which in 1932 had two time balls, a collapsible arm signal, a time gun, bells in harbour offices and time lights, all regulated using Singapore Observatory. There were time balls at Makassar (present-day Indonesia), Rangoon (present-day Myanmar, formerly Burma), Haiphong and Saigon (present-day Vietnam, formerly Indo-China) and Manila (Philippines), but not all existed at the same time and some had short lives. There were also time guns at Rangoon, Moulmein and Manila, and a time light at Rangoon. Many visual signals were discontinued when radio stations were established. Evidence of visual signals for chronometer calibration in Thailand, Malaysia and large parts of Indonesia has yet to be found.