Voyage to Lisbon on HMS Centurion and HMS Orford
In 1736, John Harrison took his first timekeeper (H1  ) on a trial voyage to Lisbon and back. He was given outward passage on the HMS Centurion  , and returned in the HMS Orford  . Conducted under the authority of the Admiralty, this trial was crucial in establishing the unprecedented accuracy of Harrison's timekeeper at sea. He was able to correct the Orford's dead reckoning by a significant one and a half degrees on the return voyage.
In proving such potential for Harrison's timekeeper, the Lisbon Voyage was essentially responsible for bringing the Board of Longitude into being. The first recorded meeting [RGO 14/5:3] of the Commissioners took place the following year on 30th June 1737. In this, they considered Harrison's machine and ' were of Opinion that the same may tend very much to the Advantage of Navigation [RGO 14/5:4].' Harrison informed them that he wished to work on a second machine (H2  ) to make some changes he had observed as necessary on the voyage, but required more money to do so. The Commissioners therefore voted £500 to Harrison, half to be paid instantly, and half on production of a certificate proving that the new timekeeper had been tested on a trial to the West Indies. In doing so, the Commissioners implemented a pattern that would continue in meetings with Harrison, of increasing frequency, for the next thirty years.
Given the instigating role of the Lisbon voyage in the story of the Board of Longitude, it is never directly mentioned in the archives. Harrison himself is similarly under-represented. Where it does appear is in the logbooks of the Centurion and Orford [ADM/L/C/82] which transported Harrison and H1. These are now in the archives of the Royal Museums Greenwich  , and form the fundamental records of the voyage, kept by Captain George Proctor, and Lieutenants Montague Bertie, John Draper, and Rowland Cotton on the Centurion, and Captain Robert Man, and Lieutenants Thomson, Knowles, and Barnard on the Orford. They recorded daily at noon, the date, winds, course, distance, latitude, longitude, bearing and distance, as was expected of any ship of the line. But they also show the difficulty of recording such unusual events as taking Harrison and H1 on board for a trial, an exercise which did not fit within the standardised record keeping. Most interestingly, Lieutenant Knowles called Harrison a ‘projector,' a word which showed that, at this date, his timekeeper was still very much untried and therefore potentially unreliable.
The Centurion and Orford were both interestingly connected to the longer history of the longitude problem. The Orford had been part of the fleet commanded by Sir Cloudesley Shovell  in 1707, which ran aground on the Scilly Isles, leading to thousands of deaths, including Shovell's. This was not far from where H1 allowed Harrison to correct the dead reckoning of the same ship for a different crew thirty years later. In 1740-44, the Centurion would become the flagship of Commodore George Anson  in the voyage around the world, on which he famously 'lost' his longitude and therefore also many men due to scurvy. These two events have been used by historians, notably Dava Sobel [link] , as examples of why accurate longitude at sea was so desperately needed.
History and Philosophy of Science
University of Cambridge