Instruments · Marine chronometer
Marine chronometer by Joseph French, Royal Exchange, London, c. 1840
- Maker / attribution
- Joseph French (maker)
- Date
- c. 1840
- Historical period
- Precision & Scientific Horology (1750 – 1850)
- Country of origin
- England
- Place
- Royal Exchange, London
- Object type
- Marine chronometer
- Materials / technique
- mahogany
- Dimensions
- Height 14 in (36 cm)
- Stock no.
- Product 44
- Credit line
- Dealer listing, P A Oxley (product 44)
- Catalogue title (original)
- Joseph French - Royal Exchange, London (English)
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Record summary
Catalogued by P A Oxley (dealer), Wiltshire (stock number Product 44), this is a marine chronometer by Joseph French, made in Royal Exchange, London, England, dated c. 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. Recorded dimensions: Height 14 in (36 cm). 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
Dealer description — P A Oxley
An excellent early 19th century antique Wall Clock by this prolific Clockmaking family. The 8 day duration single fusee movement has shaped plates, a well made anchor escapement and four plate pillars. The 12" diameter convex white dial has its original ground, Roman numerals, blued steel hands and signed by the maker Joseph French, Royal Exchange, London. The mahogany case has a flame veneered base which features a lockable access door for regulation and pendulum hanging. Also with an access door to the side. The cast brass and lockable bezel is fitted with a convex glass. Note: The French Clockmakers of The Royal Exchange, London were high quality Watch & Chronometer makers during the first half of the 19th century. They also made longcase clocks. Maker Joseph French of London
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) escapementBalance spring (hairspring)Detent escapement
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