Lighthouses Gallery

Longstone Lighthouse 34013_048

Longstone Lighthouse and Keeper's Cottage. Farne Islands, Northumberland, 2018. Famous for its association with Grace Darling, daughter of the keeper who with her father rescued five people from the wreck of the Forarshire in 1838. NU2438

© Historic England Archive

Aerial, Lighthouse

Tidal Observatory, Newlyn Harbour, Cornwall DP221138

Tidal Observatory, Newlyn Harbour, Newlyn, Cornwall. General view of tidal observatory lighthouse, shot at dawn, view from north west. Photographed by James O. Davies for Listing Review 2019. The fishing industry in Newlyn on the south coast of Cornwall expanded in the 1880s, resulting in the construction of a new harbour and two piers. In the early 20th century, the south pier was extended to give better protection to the harbour and a tidal observatory was built at its north end. The observatory was one of three constructed at the request of Ordnance Survey to establish Mean Sea Level. With the observatory being completed in 1914, hourly measurements were taken of the height of the tide between 1915 and 1921, determining that Newlyn was the most stable and therefore the principal place to establish Mean Sea Level for the entire country. Over the next 100 years, the observatory contributed key tidal data to studies in oceanography, geology and climate change. Today, all heights on Ordnance Survey maps are referenced to a brass bolt within the observatory, 4.75m above Mean Sea Level - also known as Ordnance Datum Newlyn. The Ordnance Survey gave up responsibility for the tidal observatory in 1983, but it continues to be used for scientific tidal measurements, particularly for guiding climate change and coastal management studies