# John Harrison's Marine Timekeepers, H1 to H4 > John Harrison, with James Harrison on H1 and John Jefferys on the precursor watch to H4 - H1, 1730-1735. H2, 1737-1739. H3, begun 1740 and worked on for nineteen years, catalogued as 1759. H4, begun 1755 and catalogued as 1759. > Canonical HTML: https://iconotheca.com/artworks/john-harrison/harrison-marine-timekeepers-h1-h4/ > Published by Servola Systems GmbH. Last verified: 2026-08-17 ## Tombstone - **Artist:** John Harrison, with James Harrison on H1 and John Jefferys on the precursor watch to H4 - **Date:** H1, 1730-1735. H2, 1737-1739. H3, begun 1740 and worked on for nineteen years, catalogued as 1759. H4, begun 1755 and catalogued as 1759. - **Medium:** H1: brass, bronze, steel, oak, lignum vitae and mahogany. H2: brass, bronze, steel and lignum vitae. H3: brass, bronze, steel and glass. H4: brass, steel, silver, diamond, ruby, enamel, copper and glass. - **Dimensions:** H1: 620 mm high, 680 mm wide, 450 mm deep overall on display. H2: 686 mm overall, weight 40 kg. H3: 622 mm high overall on display. H4: dial diameter 102 mm; overall 165 x 124 x 28 mm; weight 1.45 kg. - **Object type:** Clocks and instruments - **Period:** English, 1730-1759 - **Current location:** National Maritime Museum, Greenwich, on display at the Royal Observatory Greenwich; object numbers ZAA0034 (H1), ZAA0035 (H2), ZAA0036 (H3), ZAA0037 (H4) - **Attribution:** accepted ## Summary Four objects made by one man over twenty-nine years to answer a question the Royal Navy could not answer: where, east or west, a ship actually is. H1 is a 620 by 680 millimetre machine of brass and lignum vitae that runs without oil. H4 is a watch 165 millimetres across that weighs 1.45 kilogrammes. Between them lies the whole argument of eighteenth-century precision engineering, and the bimetallic strip and the caged roller bearing, both invented for H3, are still in use.What makes this a provenance record rather than an engineering story is what the state did with them. The Longitude Act of 1714 offered up to 20,000 pounds; the body set up to administer it did not meet for twenty-three years; and when Harrison's watch met the Act's terms the Board rewrote the terms. Under the Act of 1765 he was required to dismantle H4 and explain it to nominated experts before he could be paid half the money, and to surrender all four timekeepers. The Astronomer Royal, Nevil Maskelyne, who was also the leading advocate of the rival lunar-distance method, took possession of them in 1766 and tested H4 himself for ten months.Harrison never received the prize as such. He received 23,065 pounds across forty years, the last 8,750 of it by a separate Act of Parliament in 1773, when he was eighty. The four objects have been public property ever since and have never been on the market. ## Provenance Every link carries a grade. `documented` means a cited source supports it, `disputed` means the identification is argued but not established, `unknown` means we have no owner for that span and have not bridged it. - **1730-1765** John Harrison, at Barrow upon Humber and then in London `[documented]` (manufacture and possession by the maker) H1 made 1730 to 1735 at Barrow upon Humber, probably with his brother James, and brought to London in 1735. H2 completed 1739 and never sent to sea. H3 begun 1740 and worked on for nineteen years. H4 begun 1755 after the Jefferys watch of about 1751 to 1753 showed the way. Harrison kept the machines at his own house throughout. - **1736** At sea, in the maker's care, aboard HMS Centurion and the Orford `[documented]` (sea trial of H1) Out to Lisbon aboard HMS Centurion in May 1736 and home aboard the Orford. On the return leg Harrison identified a landfall as the Lizard where the ship's officers reckoned the Start, and was right by about sixty miles. It is the only sea trial any of the three large machines received. The Commissioners of Longitude voted 500 pounds on 30 June 1737, with 250 paid up front. - **1761-1765** In the custody of William Harrison for trial, on the Board's authority `[documented]` (trials of H4) H4 to Jamaica in 1761 and 1762 in the care of Harrison's son William, and to Barbados in 1764, where Nevil Maskelyne conducted the competing astronomical observations. The Board accepted that the watch had met the terms of the 1714 Act and then declined to pay the prize. - **1765-1766** The Board of Longitude, by statute `[documented]` (compulsory surrender) Under the Act of 1765 Harrison was required to dismantle H4 and explain its principles to nominated experts to receive 10,000 pounds less prior payments, to wait for a second 10,000 pounds until other makers could produce comparable watches, and to surrender the timekeepers. The Royal Museums Greenwich catalogue entry for H2 records that Harrison kept it at his residence until 1766, when the Astronomer Royal claimed it under the conditions of the longitude prize. The disclosure was published by the Board in 1767 as The Principles of Mr Harrison's Time-Keeper. - **1766** The Royal Observatory, Greenwich, under Nevil Maskelyne as Astronomer Royal `[documented]` (state custody and testing) Maskelyne received H4 on 5 May 1766 and tested it for ten months. It did not perform well and he published the result; Harrison disputed it. Maskelyne was the leading advocate of the lunar-distance method, the competing solution, which is the conflict of interest at the centre of the whole dispute. No source consulted resolves whether the poor result was the watch, the handling or the observer. - **1773-1828** The Crown, through the Board of Longitude and the Admiralty `[documented]` (public ownership) Harrison received 8,750 pounds by a separate Act of Parliament in 1773, at the age of eighty, bringing his total receipts to 23,065 pounds. He never received the 20,000 pound prize as such and never recovered the objects. The Board of Longitude was abolished in 1828 and replaced by a Resident Committee for Scientific Advice to the Admiralty whose members included Thomas Young, Michael Faraday and Edward Sabine. - **1920s-1930s** Restored by Rupert Gould while in official custody `[documented]` (conservation) Rupert Gould, a retired Royal Navy officer, restored all of the timekeepers after the First World War at his own cost and without payment, established the designations H1 to H5 that are now universal, and published The Marine Chronometer: Its History and Development in 1923. The names by which these four objects are known are his. - **-present** National Maritime Museum, Greenwich `[documented]` (museum) Object numbers ZAA0034 (H1), ZAA0035 (H2), ZAA0036 (H3) and ZAA0037 (H4). H2, H3 and H4 are displayed at the Royal Observatory Greenwich; H1 is undergoing conservation at the Prince Philip Maritime Collections Centre and a replica is shown in its place. The exact date and instrument of transfer from Admiralty custody to the National Maritime Museum is not established in the sources consulted for this record. ## Auction results Hammer and buyer's premium are stated separately. Where a source conflates them this record says so. - **** , - None of these four objects has ever been sold. They passed from their maker directly into state ownership by statute in 1765 and 1766 and have been public property continuously since. There is no hammer price, no premium, no estimate and no insurance or probate valuation in the public record for any of them, and any figure offered for what H4 would be worth is speculation about an object that cannot be sold. The sums below are payments made by the Crown for a method, not prices paid for objects. - **1737-06-30** Commissioners of Longitude, an award and not a sale, - Estimate: Not applicable - Hammer: Not applicable; no sale took place - With premium: GBP 500 voted, of which GBP 250 was paid up front - Voted after the Lisbon trial of H1, against Harrison's undertaking to build an improved machine within two years. It is the first award the Board of Longitude ever made on a submission. - **1765** Act of Parliament, a conditional award and not a sale, - Estimate: Not applicable - Hammer: Not applicable; no sale took place - With premium: GBP 10,000 less sums already paid, on disclosure of the principles of H4 - The Act also required Harrison to surrender the timekeepers, and made a further 10,000 pounds contingent on other makers producing watches of comparable performance, a condition he could not satisfy by his own effort. The disclosure was published by the Board in 1767. - **1773** Act of Parliament, a settlement and not a sale, - Estimate: Not applicable - Hammer: Not applicable; no sale took place - With premium: GBP 8,750 voted directly by Parliament - Harrison was eighty. His lifetime receipts totalled 23,065 pounds across roughly forty years. The 20,000 pound prize of the 1714 Act was never awarded to anybody in the form the Act described. Modern equivalents quoted for these figures depend entirely on the conversion method used and none of the sources consulted states which method it applied. ## Exhibitions - Ships, Clocks & Stars: The Quest for Longitude, National Maritime Museum, Greenwich, 2014-2015 - Time and Longitude, Royal Observatory Greenwich ## Literature - 1767, The Board of Longitude, The Principles of Mr Harrison's Time-Keeper, with Plates of the Same, London. The disclosure Harrison was compelled to make under the Act of 1765, published by the body that compelled it. A French edition, Principes de la montre de M. Harrison, appeared the same year. - 1923, Rupert T. Gould, The Marine Chronometer: Its History and Development, London. Written by the officer who restored all of these objects unpaid and who assigned them the designations H1 to H5. - 1802, Ferdinand Berthoud, Histoire de la mesure du temps par les horloges, vol. 2, Paris. Berthoud, Harrison's leading French rival, discusses Harrison at length and the volume carries engraved plates of watch movements. TERTIARY use only here; see notes_for_editor on a Wikimedia Commons file whose filename attributes its plate to the 1767 Principles while its own metadata attributes it to this volume. ## Open questions - The exact date and legal instrument by which the four timekeepers passed from Admiralty custody to the National Maritime Museum. The Royal Museums Greenwich catalogue entries give the credit line but no acquisition date, and none of the sources consulted here supplies one. - Whether H4's poor showing under Maskelyne's ten-month test from 5 May 1766 was caused by the watch, by its dismantling and reassembly, by the handling, or by the observer. Harrison disputed the result and no source consulted resolves it. - What the inscriptions and signatures on H1 to H4 actually read. The catalogue entries consulted do not print them. - The identity and terms of Harrison's suppliers and workmen. H1 was probably made with his brother James, and the Jefferys watch was bought in, but no workshop account for any of the four appears in the sources consulted. - How long H1 will remain out of the gallery at the Prince Philip Maritime Collections Centre, and what the conservation programme involves. The museum states the fact of the conservation but not its scope or its end date. - Whether any of H1 to H4 is currently kept running, and on what regime. The Royal Museums Greenwich pages consulted do not state it, and popular accounts that describe them ticking may be describing a past display. - The precise itemisation of the 23,065 pounds Harrison received. The 1737, 1741, 1765 and 1773 payments are documented; the intervening sums are aggregated in the sources consulted rather than listed. ## Sources - [1] Royal Museums Greenwich, collections catalogue, Marine timekeeper H1, object number ZAA0034. Source for the maker, the date range 1730 to 1735, the materials, the display dimensions of 620 by 680 by 450 mm, the description of it as the first relatively successful marine timekeeper of any kind, the two interconnected swinging balances, the temperature compensation, the absence of lubrication, the credit line and the exhibition history. - [2] Royal Museums Greenwich, collections catalogue, Marine timekeeper H2, object number ZAA0035. Source for the dates 1737 to 1739, the materials, the 686 mm overall size and 40 kg weight, the remontoire, the fact that it never went to sea, and the statement that Harrison kept it at his residence until 1766 when the Astronomer Royal claimed it under the conditions of the longitude prize. - [3] Royal Museums Greenwich, collections catalogue, Marine timekeeper H3, object number ZAA0036. Source for the date of 1759, the materials, the 622 mm display height, the nineteen years of work from 1740, and the bimetallic strip and caged roller bearing. - [4] Royal Museums Greenwich, collections catalogue, Marine timekeeper H4, object number ZAA0037. Source for the date of 1759, the materials including diamond and ruby, the 102 mm dial and 165 by 124 by 28 mm overall dimensions, the 1.45 kg weight, the John Jefferys watch of 1753 and the start of work in 1755. - [5] Wikipedia, 'John Harrison'. TERTIARY, flagged for replacement with the Board of Longitude papers. Source for the three prize tiers, the construction dates, the Lisbon trial, the Jamaica and Barbados trial figures, the 1765 and 1773 payments, the total of 23,065 pounds, Larcum Kendall's K1 and K2, H5 and the George III test, and Rupert Gould's unpaid restoration and the H1 to H5 designations. - [6] Royal Museums Greenwich, 'Harrison's clocks and the longitude problem'. Source for the May 1736 Lisbon trial aboard HMS Centurion and the Orford, the Lizard and Start landfall and the sixty miles, the payment of 500 pounds approved on 30 June 1737 with 250 up front, the nineteen years on H3 from 1740, the Jefferys watch of about 1751 to 1752, the five beats a second of H4, Maskelyne's appointment to the Barbados trial, the receipt of H4 by Maskelyne on 5 May 1766 and the ten-month test, and the current display state including H1's conservation at the Prince Philip Maritime Collections Centre. - [7] Wikipedia, 'Board of Longitude'. TERTIARY, flagged for replacement with the Board's own minutes in the Cambridge Digital Library. Source for the 1714 Act, the three prize tiers of 10,000, 15,000 and 20,000 pounds, the twenty-four commissioners, the Board's failure to convene until about 1737, the conditions imposed on Harrison including the dismantling and explanation of H4, and the abolition of the Board in 1828 and its replacement by the Resident Committee for Scientific Advice to the Admiralty with Thomas Young, Michael Faraday and Edward Sabine. - [8] Wikimedia Commons API and file description pages, used to verify extmetadata.LicenseShortName per file for every plate proposed in this record, and to read the full wikitext rather than the API summary. The K1 photograph is released under PD-UKGov as a National Maritime Museum staff photograph of about 1969 published in 1970. --- Images on this record are public domain or CC0 and are hosted by us. No image on this site is generated or simulated. If you quote this record, quote the provenance grades with it.