page_title: John Harrison
section_title: The first three marine timekeepers
hierarchical_section_title: John Harrison / The first three marine timekeepers
caption_attribution_description: English: John Harrison's H1 marine chronometer. It took Harrison about five years to develop this chronometer. Its sea trial was in 1735 on HMS Centurion to Lisbon and HMS Orford returning to England. It weighs 34 kilograms (75&#160;lb) and was originally housed in a glazed wooden case about 120 centimetres (3.9&#160;ft) in each dimension. Instead of a pendulum, it employs a pair of rocking bars with balls on the end and constrained with helical springs. The equal and opposite movement of these bars was less susceptible to being affected by a ships movement than a pendulum would be. Harrison's grasshopper escapement connects the bars with the rest of the mechanism. Some of the cog wheels are of wood which has self-lubricating properties. Gridirons provide temperature compensation by modifying the effective length of the helical springs. For this invention Harrison received £250 (compared with the £20,000 offered for a full solution) from the Board of Longitude. Harrison called it a "timekeeper". The bar-balances like elongated dumbells do not run in conventional bearings. Instead they roll on pairs of plates set at 45° to the vertical and at 90° to each other. These plates, which only move through very short distances are on the ends of long arms pivoted near the bottom of the instrument. The counterweights to these arms are the brass knobs looking like control knobs at the very bottom. This and other devices mean that the clock requires no lubrication. Harrison Jonathan Betts National Maritime Museum, Greenwich, 2007 Ref: The Illustrated Longitude, Dava Sobel and William J. H. Andrews, Fourth Estate, London, 1998. Better images: pixgood and my-time-machines. Shot without flash, 800 ASA setting.
context_page_description: John Harrison was a self-educated English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.
  Harrison's solution revolutionized navigation and greatly increased the safety of long-distance sea travel. The problem he solved was considered so important following the Scilly naval disaster of 1707 that the British Parliament offered financial rewards of up to £20,000 under the 1714 Longitude Act.
  In 1730, Harrison presented his first design, and worked over many years on improved designs, making several advances in time-keeping technology, finally turning to what were called sea watches. Harrison gained support from the Longitude Board in building and testing his designs. Toward the end of his life, he received recognition and a reward from Parliament. Harrison came 39th in the BBC's 2002 public poll of the 100 Greatest Britons.
context_section_description: In the 1720s, the English clockmaker Henry Sully invented a marine clock that was designed to determine longitude: this was in the form of a clock with a large balance wheel that was vertically mounted on friction rollers and impulsed by a frictional rest Debaufre type escapement. Very unconventionally, the balance oscillations were controlled by a weight at the end of a pivoted horizontal lever attached to the balance by a cord. This solution avoided temperature error due to thermal expansion, a problem which affects steel balance springs. Sully's clock only kept accurate time in calm weather, because the balance oscillations were affected by the pitching and rolling of the ship. However his clocks were amongst the first serious attempts to find longitude in this way. Harrison's machines, though much larger, are of similar layout: H3 has a vertically mounted balance wheel and is linked to another wheel of the same size, an arrangement that eliminates problems arising from the ship's motion.
  In 1716, Sully presented his first Montre de la Mer to the French Académie des Sciences and in 1726 he published Une Horloge inventée et executée par M. Sulli.
  
  In 1730, Harrison designed a marine clock to compete for the Longitude prize and travelled to London, seeking financial assistance. He presented his ideas to Edmond Halley, the Astronomer Royal, who in turn referred him to George Graham, the country's foremost clockmaker. Graham must have been impressed by Harrison's ideas, for he loaned him money to build a model of his "Sea clock". As the clock was an attempt to make a seagoing version of his wooden pendulum clocks, which performed exceptionally well, he used wooden wheels, roller pinions and a version of the 'grasshopper' escapement. Instead of a pendulum, he used two dumbbell balances, linked together.
  It took Harrison five years to build his first sea clock (or H1). He demonstrated it to members of the Royal Society who spoke on his behalf to the Board of Longitude.  The clock was the first proposal that the Board considered to be worthy of a sea trial.  In 1736, Harrison sailed to Lisbon on HMS Centurion under the command of Captain George Proctor and returned on HMS Orford after Proctor died at Lisbon on 4 October 1736.  The clock lost time on the outward voyage.  However, it performed well on the return trip: both the captain and the sailing master of the Orford praised the design. The master noted that his own calculations had placed the ship sixty miles east of its true landfall which had been correctly predicted by Harrison using H1.
  This was not the transatlantic voyage demanded by the Board of Longitude, but the Board was impressed enough to grant Harrison £500 for further development. Harrison had moved to London by 1737 and went on to develop H2,
  a more compact and rugged version. In 1741, after three years of building and two of on-land testing, H2 was ready, but by then Britain was at war with Spain in the War of Austrian Succession and the mechanism was deemed too important to risk falling into Spanish hands. In any event, Harrison suddenly abandoned all work on this second machine when he discovered a serious design flaw in the concept of the bar balances. He had not recognized that the period of oscillation of the bar balances could be affected by the yawing action of the ship (when the ship turned such as 'coming about' while tacking). It was this that led him to adopt circular balances in the Third Sea Clock (H3).
  The Board granted him another £500, and while waiting for the war to end, he proceeded to work on H3.
  Harrison spent seventeen years working on this third 'sea clock', but despite every effort it did not perform exactly as he would have wished. The problem was that, because Harrison did not fully understand the physics behind the springs used to control the balance wheels, the timing of the wheels was not isochronous, a characteristic that affected its accuracy. The engineering world was not to fully understand the properties of springs for such applications for another two centuries. Despite t
caption: Harrison's first sea clock (H1)
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot A470", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2011:02:24 18:36:50", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "174", "Thumbnail ImageWidth": "128", "Thumbnail ImageLength": "152", "Thumbnail BitsPerSample": "[8, 8, 8]", "Thumbnail Compression": "Uncompressed", "Thumbnail PhotometricInterpretation": "2", "Thumbnail StripOffsets": "3367", "Thumbnail SamplesPerPixel": "3", "Thumbnail RowsPerStrip": "152", "Thumbnail StripByteCounts": "58368", "Thumbnail XResolution": "180", "Thumbnail YResolution": "180", "Thumbnail PlanarConfiguration": "1", "Thumbnail ResolutionUnit": "Pixels/Inch", "EXIF ExposureTime": "1/10", "EXIF FNumber": "3", "EXIF ISOSpeedRatings": "800", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2011:02:24 13:46:57", "EXIF DateTimeDigitized": "2011:02:24 13:46:57", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "5", "EXIF ShutterSpeedValue": "53/16", "EXIF ApertureValue": "101/32", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "101/32", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "63/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "250", "EXIF ExifImageLength": "294", "Interoperability InteroperabilityIndex": "\u0001\u0001\u0001\u0002", "Interoperability InteroperabilityVersion": "[3, 0, 0, 0]", "Interoperability RelatedImageWidth": "3072", "Interoperability RelatedImageLength": "2304", "EXIF InteroperabilityOffset": "3124", "EXIF FocalPlaneXResolution": "96000/7", "EXIF FocalPlaneYResolution": "96000/7", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard"}