Harrison manufactures and trials H1 John Harrison formulated the plan for his first marine timekeeper in 1730 and sought the support of Astronomer Royal Edmond Halley, who instructed Harrison to seek out George Graham. Graham then offered Harrison a loan to develop H1. Construction took five years. In 1737, H1 was trialled aboard the ships Centurion and Orford on their return voyage to Lisbon. The timekeeper was used to correctly identify the ship’s position as 60 miles southwest of where the sailors originally thought they were, suggesting that a marine timekeeper could be the answer to the the problem of determining longitude at sea. In her book, Longitude, science writer Dava Sobel provides a full history of Harrison's dramatic quest to solve the problem of determining longitude at sea. You can also read an account Harrison’s trials and tribulations on Clocktime. Reference Sobel, D. 2011. Longitude: The true story of a lone genius who solved the greatest scientific problem of his time. London: Harper Perennial. Image Credit Front view of John Harrison's marine timekeeper H1. Object: ZAA0034. © National Maritime Museum, Greenwich, UK, Ministry of Defence Art Collection, CC BY-NC-ND 3.0, https://www.rmg.co.uk/collections/objects/rmgc-object-79139
