Instruments · Marine chronometer
Marine chronometer no. 1948 by Robert and Henry Molyneux
- Maker / attribution
- Robert and Henry Molyneux (maker)
- Date
- 1840
- Historical period
- Precision & Scientific Horology (1750 – 1850)
- Country of origin
- Unrecorded in source
- Object type
- Marine chronometer
- Materials / technique
- mahogany, steel, brass, silver
- Dimensions
- Overall: 225 x 205 x 205 mm
- Holding institution
- Royal Museums Greenwich
- Accession / object no.
- ZBA0671
- Credit line
- National Maritime Museum, Greenwich, London
- Catalogue title (original)
- 1948 (English)
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Record summary
Held and catalogued by Royal Museums Greenwich (object number ZBA0671), this is a marine chronometer by Robert and Henry Molyneux, dated 1840. The Atlas places it in the Precision & Scientific Horology period (1750 – 1850) of its Instruments collection. Materials and techniques recorded by the source: mahogany, steel, brass, silver. Recorded dimensions: Overall: 225 x 205 x 205 mm. The record is illustrated with 1 photograph.
Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.
Catalogue description
Catalogue description — Royal Museums Greenwich
This eight-day marine chronometer has a standard, double-frame reverse-fusee movement with an Earnshaw-type spring detent escapement and a standard compensation balance. The chronometer was purchased by the Admiralty in March 1857, when it was probably about twenty years old, and was sent immediately to William Cribb to be re-rated to solar time from sidereal, and to be “fitted with boxes”. It was then issued to the paddle wheel steamer HMS Cyclops for work taking soundings for laying first Atlantic telegraph cable, returning via HMS Racer in 1862. It was then sent to the fifth rate Flora in 1868, and in 1878 to HMS Terror, the base ship at Bermuda. In 1905 it was issued for service with the Labrador Boundary Commission, used during the Newfoundland Survey. In 1913 it went to the survey vessel HMS Mutine returning from Bermuda in 1915. In 1929 the chronometer was issued to the Royal Society’s Eclipse Expedition to Sumatra, after which it remained at the Royal Observatory for internal use. It was transferred to the NMM collections on the closure of the Royal Greenwich Observatory in 1998.
Historical context
Precision & Scientific Horology (1750 – 1850)
Harrison solves longitude; Mudge invents the lever; Breguet's Paris workshop defines the modern watch.
The longitude problem was solved by the marine chronometer and lunar distance methods; dividing engines made precision scales possible, and observatories set time by transit instruments.
Read the period in the timelineMore instruments from this periodEarlier: Early Modern Horology
Atlas type guide
Marine chronometers
A marine chronometer is a precision timekeeper carried at sea to find longitude: the navigator compares local noon, observed with a sextant, with the time at a reference meridian kept by the chronometer. Each hour of difference corresponds to fifteen degrees of longitude. John Harrison proved the method in the 1760s; Pierre Le Roy, Ferdinand Berthoud, John Arnold and Thomas Earnshaw then developed the detent escapement and the compensation balance that made chronometers practical to manufacture.
By the nineteenth century London, Liverpool, Le Locle and Glashütte supplied navies and merchant fleets. A typical box chronometer has a spring-detent escapement, a fusee to equalise mainspring torque, a bimetallic compensation balance with a helical balance spring, and is mounted in gimbals inside a wooden box so that it stays level.
What to look for
- Gimbals and a three-tier wooden box with a glazed inner lid.
- A power-reserve ('up and down') indicator on the dial, usually showing 56 hours on two-day instruments.
- Spring-detent escapement and a cylindrical (helical) balance spring visible through the movement.
- Admiralty or navy marks (broad arrow), and rating certificates from observatories.
- The maker's number on the dial and movement; many makers' registers survive, allowing dating.
Dating clues
- Earnshaw-type spring-detent chronometers became standard after about 1800.
- Auxiliary compensation devices on the balance appear from the mid-nineteenth century.
- Quartz and radio time signals ended routine use of mechanical chronometers in the 1970s and 1980s.
General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.
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