Marine watch

Historical significance

• Described in detail in Louis Berthoud's four workshop journals, now in the archives of the Museum of Industrial Arts and Crafts in Paris, this chronometer originally had a gold or silver case, which has since disappeared (Boëte de Joly no 644, op. cit.).
• The white enamel dial has a clover-shaped aperture over the balance's lower pivot point, a large central minute hand, and two small offset chapter rings - for the hours at the top and the seconds at the bottom.
• The pillar movement has a fusee and chain fitted with maintaining power, a pivoted detent escapement, a two-arm compensation balance bearing two trapezoidal weights, and a cylindrical balance spring. The upper plate, heavily pierced unlike other Louis Berthoud chronometers, supports the three anti-friction rollers, which are also used at the lower pivot point of the balance staff.
• After Louis Berthoud regulated this marine watch between the 7 May and 28 August 1791, it was taken on board Rear Admiral d'Entrecasteau's ship, La Pérouse, for a voyage of research. The performance of this watch during this expedition was the subject of the first appendix of Louis Berthoud's Entretien sur l’horlogerie à l’usage de la Marine (Discussion on Clocks and Watches for Use by the Navy), published in Paris in 1812.

Sources & references

1. Musée international d'horlogerie, online collection record, inv. I-109: https://collection.mih.ch/fr/collection/item/32081/

Where sources disagree, the disagreement is stated rather than resolved silently.