# Marine Chronometer by Thomas Earnshaw > Thomas Earnshaw - c. 1800 (dated by the British Museum to the range 1795-1805) > Canonical HTML: https://iconotheca.com/artworks/thomas-earnshaw/earnshaw-chronometer-beagle-british-museum/ > Published by Servola Systems GmbH. Last verified: 2026-08-29 ## Tombstone - **Artist:** Thomas Earnshaw - **Date:** c. 1800 (dated by the British Museum to the range 1795-1805) - **Medium:** Brass movement (bowl, plates, pillars, wheels) and steel components (spring detent escapement, balance spring, hands) in a rectangular mahogany box lined with green baize, with an ivory disc set into the lid; silvered brass dial - **Dimensions:** 17.6 x 20.8 x 20.8 cm (box, as catalogued by the British Museum) - **Object type:** Clocks and instruments - **Period:** British, early nineteenth century - **Current location:** British Museum, London (Room 39, Clocks and Watches, Case 10, on display) - **Attribution:** accepted ## Summary A one-day marine chronometer, serial number 509, made in London by Thomas Earnshaw around 1800 and issued by the Royal Observatory, Greenwich to a succession of Royal Navy ships over four decades, including HMS Beagle's second survey voyage of 1831 to 1836, the voyage that carried Charles Darwin. Captain Robert FitzRoy sailed with twenty-two chronometers rather than the usual three, a deliberate scientific redundancy intended to let him cross-check longitude readings against one another across a circumnavigation lasting five years.Most of the twenty-two were sold, lost or scattered after the voyage, and tracing the survivors is itself active research rather than settled fact: how many are confirmed today depends on which published count is consulted. This instrument's own service record, by contrast, is unusually complete. The Greenwich ledger of chronometer issues tracks serial 509 by name through HMS Hecla, HMS Beagle, HMS Formidable and HMS Pembroke, then to shore duty at the Royal Society's Falmouth Observatory, and finally into the private collection of the engineer and horological collector Courtenay Adrian Ilbert, whose estate reached the British Museum in 1958.The one genuine gap in that chain is exactly where an object usually loses its history: the interval between being declared beyond economical repair by the Navy's own watchmaker in 1886 and turning up, at an unrecorded date, in Ilbert's collection. ## 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. - **c. 1795-1805** Thomas Earnshaw, chronometer maker, 119 High Holborn, London `[documented]` (manufacture) Made and signed by Earnshaw at his Holborn workshop and given serial number 509, the number stamped on both the movement and the dial and used by the Royal Observatory Greenwich to identify the instrument in its issue ledger for the rest of its service life. - **-1826-02-06** Board of Longitude / Royal Observatory, Greenwich (early Royal Navy service, ship or ships not confirmed for this serial number) `[unknown]` (gap, with unverified general context) The Wikipedia 'good article' on this object opens its service history with a general account of the Navy's early chronometer-issuing system: William Edward Parry's published narrative of his 1818-19 Arctic voyage mentions an Earnshaw chronometer being used near Baffin Bay, without naming the ship, and the same article separately notes that the Greenwich Observatory's first recorded issue under its formal system was in 1823, to HMS Larne. Neither anecdote is stated, by that article or by the British Museum, to be about serial 509 specifically, and this record does not assert that it is. The first entry the sources tie explicitly to this instrument is its return to Greenwich on 6 February 1826. - **1826-02-06-1828-03-04** Royal Observatory, Greenwich, in for servicing at the maker's `[documented]` (service) Returned to Greenwich 6 February 1826 and sent to Earnshaw's for servicing; it did not come back to Greenwich for nearly two years. - **1828-03-04-1830-07** Royal Navy, issued to HMS Hecla under Captain J. Bolder `[documented]` (naval service) Issued 4 March 1828 to Captain J. Bolder in command of HMS Hecla, then engaged in a survey of the West African coast. Hecla was a well-known ship, having carried Parry's second and third Arctic expeditions before this posting. Returned from Hecla and sent for cleaning to the watchmaker Robert Molyneux, London, in July 1830. - **1830-07-1831-12-06** Royal Observatory, Greenwich, via Robert Molyneux (service) and Devonport (delivery) `[documented]` (service and transfer) Serviced by Robert Molyneux, returned to Greenwich in November 1830 but not immediately reissued. Delivered to Devonport in March 1831, where its rate was checked and recorded. - **1831-12-06-1836-11-07** Royal Navy, HMS Beagle, second survey voyage `[documented]` (naval service) Issued 6 December 1831 to 'Captain Stokes' in command of HMS Beagle, per the Greenwich ledger as cited by the British Museum and by the Wikipedia article compiling the museum's own database; the ship sailed under Captain Robert FitzRoy on its famous circumnavigation with Charles Darwin aboard as naturalist, and was one of twenty-two chronometers carried. Returned to Greenwich 7 November 1836. - **1836-11-07-1842-01-13** Royal Observatory, Greenwich, via Arnold and Dent (service) and Devonport/Portsmouth (issue) `[documented]` (service and transfer) After cleaning by Arnold and Dent, transported by HMS Lightning to Devonport or Portsmouth for local issue. Returned to Greenwich 17 November 1841 and serviced again by Arnold and Dent before its next posting. - **1842-01-13-1845-11-20** Royal Navy, HMS Formidable `[documented]` (naval service) Issued to HMS Formidable 13 January 1842 and returned to Greenwich 20 November 1845. - **1845-11-20-1858-04-20** Royal Observatory, Greenwich, serviced repeatedly by Charles Frodsham and issued locally from Portsmouth `[documented]` (service and repeated transfer) Serviced by Charles Frodsham and sent for issue to ships at Portsmouth. Returned to Greenwich for further Frodsham servicing via HMS Rattlesnake (11 March 1850) and HMS Odin (27 December 1854), and finally back from Portsmouth 7 May 1857. - **1858-04-20-1867-02-01** Royal Navy, HMS Pembroke `[documented]` (naval service) The final ship to be issued the chronometer. Received it 20 April 1858; returned it to Greenwich 1 February 1867. - **1867-02-01-1886-11-03** Royal Society, Meteorological Committee, Falmouth Observatory `[documented]` (shore service) Stayed with Frodsham for servicing over six months, then issued by Greenwich to the Royal Society's Meteorological Committee 25 November 1867 for observations at Falmouth Observatory. Returned to Greenwich 3 November 1886. - **1886-11-22-1888-07-16** Royal Observatory, Greenwich, then E. Dent and Co. `[documented]` (condemnation and disposal) Sent to J. Poole for servicing 22 November 1886; Poole returned it 13 December 1886 declaring it beyond economic repair. Given to E. Dent and Co. on 16 July 1888 in part exchange for a different instrument, chronometer Dent 43107. - **1888-07-16-1956** Unknown, then Courtenay Adrian Ilbert (civil engineer and horological collector) `[unknown]` (gap, then private acquisition) No source consulted for this record states when or how the chronometer passed from E. Dent and Co. into the collection of Courtenay Adrian Ilbert, who assembled what is described as the most extensive private collection of watches, clocks, marine chronometers and sundials of its time at his home in Chelsea. This is the one real gap in an otherwise unusually well-documented service record, and it is exactly the kind of gap this record will not paper over with a guess. - **1956-1958** The Ilbert estate, prepared for auction `[documented]` (death and dispersal planned) Ilbert died in 1956. His collection, including this chronometer, was catalogued for public auction. - **1958-present** British Museum, London `[documented]` (acquisition) The planned auction was cancelled and the entire Ilbert Collection was purchased instead, following a private donation of funds by Gilbert Edgar that let the museum buy the collection intact rather than see it dispersed lot by lot. Accessioned as 1958,1006.1957 (registered 6 October 1958, per the accession-number convention), retaining the Ilbert Collection reference CAI.1957, L210. On display in Room 39. ## Open questions - How many of the Beagle's twenty-two second-voyage chronometers survive today? Sources disagree: the Wikipedia article specific to this object states two, both British Museum-owned; a separate Wikipedia survey of the ship's full chronometer complement states three; and this record's own research independently confirms at least two further survivors (pocket chronometer K, National Maritime Museum, and chronometer French 4214, Royal Museums Greenwich) plus a fifth in private hands (chronometer N, sold at Bonhams in 2014) that are not clearly folded into either published count. No single source consulted gives a total that accounts for all of these. - When and how did this chronometer pass from E. Dent and Co., which received it in part exchange in July 1888, into the collection of Courtenay Adrian Ilbert? No source fetched for this record documents the intervening years before Ilbert's death in 1956. - Was the Earnshaw chronometer mentioned in William Edward Parry's 1818-19 account of his search for the Northwest Passage this specific instrument, serial 509, or a different Earnshaw chronometer of the period? Parry's own account does not name the ship it was aboard, and no source consulted resolves the question either way. - Why was this chronometer issued to the Beagle's book under the name 'Captain Stokes' in December 1831, when the ship is otherwise universally associated with Captain Robert FitzRoy? The Greenwich ledger entry as reported does not explain the discrepancy, which may reflect ordinary Navy paperwork practice (recording an officer other than the eventual commanding captain at the moment of issue) or may indicate something the sources consulted do not capture. - What did the British Museum pay, if anything beyond Gilbert Edgar's donation, to complete the 1958 purchase of the Ilbert Collection, and what was the collection's total value at the cancelled auction? The sources consulted describe the mechanism of the purchase but not its financial terms. - Does the Board of Longitude award to Earnshaw in 1805 reflect a figure of 2,500 pounds, as one secondary source states, or 3,000 pounds matching John Arnold's award, as the Dictionary of National Biography states? This record follows the DNB figure as the more directly sourced of the two but the discrepancy is not resolved. ## Sources - [1] British Museum, Collection Online, 'marine chronometer', museum number 1958,1006.1957 (object description, dimensions, inscriptions, materials, maker, acquisition note, exhibition history, current display location). - [2] British Museum, Collection Online, 'chronometer watch; repeating watch' by Robert Pennington, museum number 1958,1201.1743 (the second Beagle-associated instrument in the British Museum's own collection, fetched to confirm its registration number and maker independently rather than assume it from secondary sources). - [3] Wikipedia, 'Ship's chronometer from HMS Beagle', a Good Article compiling the British Museum's object database, the Royal Observatory Greenwich's ledger of chronometer issues, and published sources including James Taylor's 'The Voyage of the Beagle' (2008), F.W. and J.M. Nicholas's 'Charles Darwin in Australia' (2002), Philip Parker King, Charles Darwin and Robert FitzRoy's 'Narrative of the Surveying Voyages of His Majesty's Ships Adventure and Beagle' (1839), Rupert Gould's 'The Marine Chronometer' (1960), Dava Sobel and William Andrewes's 'The Illustrated Longitude' (1998), and Fiona Macdonald's 'Inside the Beagle with Charles Darwin' (2005). Tertiary; flagged for replacement with the British Museum's own curatorial file and the Greenwich ledger pages themselves where a researcher needs primary confirmation of an individual date. - [4] Wikipedia, 'Ship's chronometer from HMS Beagle', full wikitext with inline citations, fetched separately to confirm the reference list and the exact wording of the disputed points (the Parry/Larne anecdotes, the FitzRoy 33-second closure error, the Darwin GBP 500 keep payment, and the bibliography). - [5] Wikipedia, 'List of chronometers on HMS Beagle', a survey of the ship's chronometer complement across all three of its voyages, including a differing survivor count from the object-specific article. Tertiary; the discrepancy between this page and source 3 is recorded in this record's open questions rather than silently resolved. - [6] Wikipedia, 'Thomas Earnshaw', for the maker's biography, his invention of the spring detent escapement and bimetallic compensation balance, and the 1805 Board of Longitude award. Cross-checked against the Dictionary of National Biography entry (source 9) for the award figure, where the two disagree. - [7] Wikipedia, 'Courtenay Adrian Ilbert', for the collector's career, the scale of his horological collection, his death in 1956, and the cancelled 1958 auction and museum purchase. - [8] Wikimedia Commons, file description and extmetadata for 'File:British Museum Marine Chronometer.jpg' (license CC0, photographer BabelStone, description confirming the object as the Earnshaw Beagle chronometer) and for 'File:EARNSHAW 509 165.jpg' and 'File:FalmouthObservatory2.jpg' (both public domain), fetched via the Commons API to verify licensing and description before use. - [9] Dictionary of National Biography, 1885-1900, 'Earnshaw, Thomas', via Wikisource: birth at Ashton-under-Lyne 4 February 1749, apprenticeship, the 119 High Holborn workshop, the 1793 Board of Longitude submission backed by Nevil Maskelyne, the 1805 award of GBP 3,000 to both Earnshaw and John Arnold, the 1808 pamphlet 'Longitude: an Appeal to the Public', and death 1 March 1829 at Chenies Street, Bedford Square. - [10] All At Sea, 'Pocket Chronometer Used On Charles Darwin's Beagle Voyage Acquired By The National Maritime Museum, Greenwich' (2025-2026), on Beagle pocket chronometer 'K', saved from export in 2025 and acquired by the National Maritime Museum, Greenwich, for display from October 2026. Cited only as context for a different object at a different institution; no image or fact from this object is used for the present record. - [11] ianvisits, 'Darwin's HMS Beagle chronometer blocked from export to keep it in the UK' and 'One of HMS Beagle's last surviving chronometers is coming to Greenwich', on the 2025 export bar and 2026 display of chronometer K at the National Maritime Museum, Greenwich. Context only, different object and institution. - [12] Royal Museums Greenwich, 'The lost chronometer: the timepiece that sailed with Charles Darwin and Sir John Franklin', on chronometer 'French 4214', issued to the Beagle's second voyage in 1831 and later to HMS Erebus for the 1845 Franklin expedition, recovered in fragments by the Charles Francis Hall search expedition of 1869 and now in the Royal Museums Greenwich collection. A different, distinct instrument, cited only for the survivor count discussed in this record's open questions. - [13] Bonhams, sale 21931, lot 26, 'The property of Captain Robert FitzRoy, an historically important... two day marine chronometer present on the second and third voyages of HMS Beagle', by Robert Molyneux, London, no. 1175 (Beagle designation 'N'). FitzRoy's personal property, purchased by the British Government in 1837, later lost with HMS Irresistible in the 1916 Dardanelles campaign, recovered and resurfaced aboard a Soviet Liberty ship in the Second World War, sold at Bonhams London 10 December 2014 for GBP 100,900 including premium. A different, distinct instrument, in private hands, cited only for the survivor count and as a market comparandum. --- 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.