Chronometers were formerly used for the accurate determination of longitude by ships at sea. By measuring the time of local solar noon compared to the time of noon at a reference point, the difference in longitude can be directly found. For this system to work, a timepiece showing the time at the reference point must be carried to the measuring point. A timepiece intended to remain accurate while subjected to the motions of a ship at sea and through extreme changes in environment, especially temperature, is called a chronometer. These were first built in the 18th century and were used extensively by mariners in the 19th century and into the 20th century, even after the widespread use of radio for time signals – the time signal was used to set the chronometer, but the instrument was still necessary to display the time.Gould, p. 211

HMS Beagle was an Admiralty survey ship sent on three major expeditions. The first (1826–1830) was to survey the coast of South America in company with HMS Adventure. The second expedition (1831–1836) was to build on the work of the first in South America and then to go onward to establish a chain of linked reference points encircling the globe. The third expedition (1837–1843) surveyed the coast of Australia.Fitz-Roy, p. 1King, p. 1Nicholas and Nicholas, pp. 3–4, 191–192

A chronometer was first carried on a survey ship by James Cook on his second voyage in 1772. This was Larcum Kendall's K1, a copy of John Harrison's H4, the first practical chronometer. From 1818 the Admiralty began issuing chronometers to naval ships. From 1825, this became standard and ships were issued a second chronometer if the captain personally provided a third. Three chronometers was the minimum necessary to be able to identify whether one had become unacceptably inaccurate. By the time of the Beagle voyages, the use of marine chronometers had become routine and the ship carried a large number – an unprecedented 22 on the second voyage. This had become possible because the price of chronometers had decreased steadily as manufacturing increased. H4 had cost over £20,000 (inflation adjusted £) to develop. Kendall's K1 cost £500 (now £) and his cheap model, K3, cost £100 (now £), but by the time the Beagle voyages were over the cost of a good chronometer had fallen to under £40 (now £).Fisher and Johnston, pp. 70–72Nicholas and Nicholas, pp. 4–6

Beagle required large numbers of chronometers because some would inevitably break down on long voyages and the chronometers were essential for the mission of the ship. Further, the rates of all chronometers vary with time. Although this can be allowed for by interpolating between the regular rate checks, there is no guarantee that the changes are linear, and often they are not. Averaging the readings from a large number of chronometers, especially if they are of a variety of types, will tend to cancel out such errors.Fitz-Roy and King, pp. 319–320Nicholas and Nicholas, pp. 4–6

To reach all points designated by the Admiralty for longitude measurements, it was sometimes necessary to take chronometers ashore, across inlets and up rivers too shallow for the ship. This put the chronometers at risk and the disturbance of moving them affected their accuracy. This was another reason for survey ships to carry a large number – most of them could be kept permanently in a safe, well-cushioned place on the main vessel.Haycox et al., p. 106

Chronometer makers Some details of the chronometer makers referred to in the lists below are given in this table. With few exceptions, they were London-based makers.

+ Chronometer makersMakerDetailsArnoldJohn Arnold (1736–1799) was the leading chronometer maker of his time. He opened his business in The Strand in 1763, and later went into partnership with his son, John Roger Arnold (1769–1843), forming the company Arnold & Son."John Arnold", British Museum Collection Database, retrieved and archived 14 January 2012.Arnold & DentThis was the successor company to Arnold & Son and was formed by a partnership between John Roger Arnold and Edward John Dent. The partnership lasted from 1830 to 1840. Dent then continued in business in his own right. Arnold & Son was acquired by Charles Frodsham after Arnold's death in 1843."John Roger Arnold", British Museum Collection Database, retrieved and archived 14 January 2012."Arnold & Dent", British Museum Collection Database, retrieved and archived 14 January 2012.DentEdward John Dent (1790–1853). After the end of the partnership with Arnold, Dent formed a business which was continued by his stepsons. This business ultimately became E. Dent & Co. and continued trading until 1976. Dent is perhaps best known as the designer of the Big Ben clock, which was finished by one of his stepsons."Edward John Dent", British Museum Collection Database, retrieved and archived 14 January 2012.EarnshawThomas Earnshaw (1749–1829). An important figure in the history of chronometers, Earnshaw invented the spring detent escapement which later became the standard arrangement for all chronometers. He also made improvements to the temperature compensation of balance wheels."Thomas Earnshaw", British Museum Collection Database, retrieved and archived 14 January 2012.EiffeJohn Sweetman Eiffe (d.1880). Until his death, Eiffe held a grudge against the Admiralty for their failure to give him a reward for his invention of an auxiliary temperature compensation, which was independently discovered and patented by Molyneux while the Admiralty was still examining Eiffe's version.Gould, pp. 181–182FrenchSantiago James Moore French, or sometimes just James Moore French, was active from 1808 to 1842. He was a London chronometer maker operating at the Royal Exchange, later at Cornhill."Santiago James Moore French", British Museum Collection Database, retrieved and archived 13 January 2012. French won a minor prize from the Board of Longitude for his chronometers and his no. 720 was the standard (that is, considered the best to which the others are compared) for 16 chronometers used to determine the accurate longitude of Madeira in 1822."Geography, astronomy &c: chronometers", The Annual Register for 1825, p. 259, London: various publishers, 1826 .FrodshamCharles Frodsham (1810–1871) was a clockmaker and chronometer maker with premises initially in Finsbury Pavement and then New Bond Street. He purchased the business of John Roger Arnold on Arnold's death in 1843 and was then based at the premises of Arnold's business in The Strand under the name of Arnold & Frodsham. He was granted a Royal Warrant in 1854 and reverted the name to Charles Frodsham & Co. in 1858. Charles Frodsham & Co. Ltd. is still in existence, but has moved from The Strand to another London address."Charles Frodsham", British Museum Collection Database, retrieved and archived 14 January 2012.GardnerRobert Gardner (d. 1875) was a Glasgow supplier who founded the business of Gardner and McGregor in 1834. He may not be the manufacturer of the chronometers he sold. His son of the same name (b. 1851) was a noted horological collector.Chamberlain, p. 456McCabeMcCabe was a London clock and watchmaker active from 1780 to 1811. He was born in Ireland but moved to London in 1775. The business he founded continued to trade until 1883."McCabe", British Museum Collection Database, retrieved and archived 14 January 2012.MolyneuxRobert Molyneux (d.1876) was a clock and watchmaker with premises in Southampton Row. The partnership R. & H. Molyneux was formed between Robert and his son Henry in 1835. The business was succeeded by Birchall & Appleton in 1842, who in turn were succeeded by William E. Cribb.Britten pp. 634, 646, 670, 744"R & H Molyneux", British Museum Collection Database, retrieved and archived 16 January 2012."Chronometer watch by Cribb", British Museum Collection Database, retrieved and 16 January 2012.MorriceD. & W. Morrice, chronometer, clock and watchmakers, 80 Cornhill, London.Robson, p. 724MurrayJames Murray (1780–1847) was a Scottish clock, watch and chronometer maker with a business at the Royal Exchange from 1815 to 1847. His chronometer won the top prize in the Greenwich trials for 1823 and later accompanied William Parry on his final attempt to find the Northwest Passage. His chronometers also accompanied James Weddell to the Antarctic Ocean, reaching, in 1823, the most southerly point achieved by any ship or chronometer up to that time. His son, James, continued the business and set up subsidiaries in Melbourne and Calcutta.Britten, p. 747Leahy, p. 41Rubin, p. 32"James Murray", British Museum Collection Database, retrieved and archived 18 January 2012."Multi-time watch / centre-seconds watch", British Museum Collection Database, retrieved and 18 January 2012."The best chronometer", Glasgow Mechanic's Magazine, vol. 2, no. 57, p. 445, 29 January 1825, Glasgow: W. R. McPhun, 1825.Parkinson & FrodshamWilliam Parkinson and William James Frodsham (1778–1850) formed a London business in 1801. Frodsham came from a long line of watchmakers. He was the grandson of William Frodsham, who was taught by Earnshaw, and his mother was the granddaughter of the famous John Harrison, the inventor of the first marine chronometer. He was also the father of Charles Frodsham. The company continued to trade until 1947.Britten, pp. 691, 753"Parkinson & Frodsham", British Museum Collection Database, retrieved and archived 18 January 2012.PenningtonRobert Pennington (1780–1844) was a chronometer maker from Camberwell. Robert Pennington & Son was a partnership between Pennington and his son John that existed between 1832 and 1842. Pennington Sr. invented an improved sector.Britten, p. 755"Robert Pennington", British Museum Collection Database, retrieved and archived 18 January 2012.

Nomenclature In the following lists, the designation letter ("Des." column) is a reference assigned to the chronometer while it was on board ship and was used to identify the instrument in logged tables of chronometer readings during the voyage. It was a temporary designation with no relevance once the ship's mission was over. The number ("No." column) was a number permanently marked on it by the maker and together with the maker's name uniquely identified the instrument. When referring to chronometers, the maker's name is frequently abbreviated; for instance, Earnshaw's chronometer no. 509 is known simply as E509. The "type" of all chronometers listed here is either box or pocket. A boxed chronometer is mounted on gimbals attached to its box. A pocket chronometer is in the style of a pocketwatch. "Winding" refers to the number of days that a chronometer kept going before needing rewinding. However, they were all wound at precisely the same time every day, except for the eight-day chronometers which were wound weekly.Fitz-Roy and King, p. 427

First voyage On its first voyage (1826–1830), the Beagle accompanied the Adventure, which led the expedition under the command of Phillip Parker King. The Beagle was initially commanded by Pringle Stokes, but Stokes became depressed and shot himself on 1 August 1828 while the expedition was at Port Famine. He died 12 days later. After a brief temporary command by Lieutenant Skyring, Robert Fitz-Roy, future first head of the Met Office, was appointed the new commander of Beagle.Anderson, p. 44King, pp. xiii–xiv, 152–153

Beagle carried only three chronometers on this expedition; the majority of the expedition's chronometers were on board Adventure (see next section).Fitz-Roy and King, pp. 318–319

+ Chronometers on first voyage (Beagle)Des.MakerNo.OwnerTypeWindingCommentsRef. – Parkinson & Frodsham228 GovernmentKing, p. xvi box – Assessed by King as "excellent", These two chronometers had previously been used on polar voyages before being assigned to Beagle. Fitz-Roy and King, p. 319 – Parkinson & Frodsham254 Government box – – McCabe228 Government box – Assessed by King as "excellent"

Adventure's chronometers