Instruments · Marine chronometer
Marine Chronometer - No.1438, Molyneux & Sons, London, England, c. 1830s
- Maker / attribution
- Molyneux & Sons (Maker)
- Date
- c. 1830
- Historical period
- Precision & Scientific Horology (1750 – 1850)
- Country of origin
- England
- Place
- London, Middlesex, England, Great Britain
- Object type
- Marine chronometer
- Dimensions
- 18 cm (Length), 18 cm (Width), 20 cm (Height)
- Holding institution
- Museums Victoria, Melbourne
- Accession / object no.
- ST 42498
- Catalogue title (original)
- Marine Chronometer - No.1438, Molyneux & Sons, London, England, circa 1830s (English)
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Record summary
Held and catalogued by Museums Victoria, Melbourne (object number ST 42498), this is a marine chronometer by Molyneux & Sons, made in London, Middlesex, England, Great Britain, dated c. 1830. The Atlas places it in the Precision & Scientific Horology period (1750 – 1850) of its Instruments collection. Recorded dimensions: 18 cm (Length), 18 cm (Width), 20 cm (Height). The record is illustrated with 5 photographs.
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
Summary — Museums Victoria
Marine chronometer by Molyneux & Sons, London, no. 1438, circa 1830s. This is one of the first two chronometers used by Government Astronomer Robert Ellery at the Williamstown Observatory in the 1850s. This chronometer was also used in several astronomical expeditions undertaken by the Melbourne Observatory, including the total solar eclipse expedition to north Queensland in 1871 and the Transits of Venus in 1874 and 1882. In 1887 Ellery could report that the chronometer was still going at an excellent rate. See Robert Ellery to Editor of The Observatory, 19 Oct 1887 [Public Record Office of Victoria, series VPRS 866, Outward Letter Books - Foreign, Vol 1) In about 1860 Ellery had the chronometer adapted by a Williamstown watchmaker so that an electrical circuit was attached to the seconds arbor of the chronometer, producing an electrical signal every second that could be used to mark a chronograph. Thus adapted, the chronometer could be used in field observatories to enable chronographic registration of astronomical observations. Ellery used the chronometer for field observations during the Geodetic Survey in the 1860s. See Robert Ellery, 'On the Application of Galvanic Electricity to Practical Astronomy,' Transactions of the Royal Society of Victoria, v 5, 1860.
Physical description — Museums Victoria
Brass chronometer on brass gimbals in wooden case. Silvered dial with roman numerals and seconds dial at 6 o'clock and winding dial at 12 o'clock. Label inside case indicating chronometer used as a sidereal chronometer at Melbourne Observatory, and notes of repair dates from 1882 to 1892.
Inscriptions & marks
Dial marked "MOLYNEUX & SONS, 30 SOUTHAMPTON ROW, LONDON: 1438".
Provenance
Transfer from Office of Trade Measurement (formerly Weights & Measures Branch), Victoria: Local Government Department, 28 Sep 1994
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.
Read next:Spring detent (chronometer) escapementFuseeBalance spring (hairspring)Detent escapement
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