Portal de Periódicos da CAPES

TIME SIGNALS FOR MARINERS IN THE ATLANTIC ISLANDS AND WEST AFRICA

2021; National Astronomical Research Institute of Thailand; Volume: 24; Issue: 2 Linguagem: Inglês

10.3724/sp.j.1440-2807.2021.02.03

1440-2807

Roger Kinns,

Historical Geography and Cartography

The first time ball on an Atlantic island was established at Jamestown, St Helena in January 1834. It was one of the earliest operational time balls. New insights into preceding time ball trials at Portsmouth, England in 1829-1830 are presented. The primary time ball in St Helena was erected at the Ladder Hill Observatory, with a repeater time ball and a time gun. The Observatory was closed in 1836, but the time ball service continued with limited apparatus into the twentieth century. Notices about a time ball at Ascension were published in 1860 and 1865. A time ball at the Cape Coast Castle in Ghana was erected in July 1839 but may not have existed for long. A flag and time gun at Accra were listed by 1898. In 1932, there was a combined time ball and time gun service at Takoradi but no service at Accra. A time ball at St. Paul de Loanda in Angola was regulated by the observatory there from 1879. It was later replaced by time lights. There had also been a short-lived time ball at Tokonu in Nigeria, noted as being regulated from Loanda. Clocks were available for chronometer calibration in the Azores at Punta Delgada by 1904 and at Horta by 1908, regulated from Lisbon and Hamburg respectively. Telegraph office signals were available at Tenerife and Madeira by 1911. The most northerly time ball on the west coast of Africa at Dakar in Senegal was established in the early twentieth century but then withdrawn. It was re-established in 1911 and was still operating in 1920. New time signals were introduced on São Vicente Island in the nearby Cape Verde islands in February 1922, including a time ball. Telegraph signals had previously been available in the islands.