Marine chronometer by Breguet & Fils

Description — British Museum

Marine chronometer; spring-driven; thirty-hour movement; fusee with Harrison's maintaining-power; club-tooth lever escapement; balance with bimetallic rim for temperature compensation; independent seconds-train, recording minutes and seconds on right-hand dials; main dial for hours and minutes on left, seconds-dial above; lower 'up-and-down' dials indicate running time available for going-train and independent seconds-train; canister enclosing movement; suspended in gimbals within walnut box; complete with canister-securing key and winding key.

Curator's comments — British Museum

Text from 'Clocks', by David Thompson, London, 2004, p. 134. Breguet et Fils Marine chronometer Paris, 1813 Height 12.55 cm, width 17.4 cm, depth 17.4 cm Towards the end of the eighteenth century, improvements in the timekeepers used for finding longitude at sea were, to a large extent, achieved by English chronometer makers, particularly John Arnold and Thomas Earnshaw. Nevertheless, the great French clockmakers were also striving for the same goal and makers such as Ferdinand Berthoud, Pierre Leroy and Henri Motel all played their part. The most celebrated French watchmaker, Abraham Louis Breguet, was involved in the quest and made a number of marine chronometers. This example was never used at sea. When completed in 1813 Breguet used it himself as an experimental workshop piece until 1822. The chronometer has a lever escapement and also an independent timer for minutes and seconds. The silver dial shows the hours and minutes on the left and has a chapter ring with seconds in the top centre, but there are also dials on the right for independent minute- and seconds-timing and two sectors at the bottom which show the state of wind of the two mainsprings. The box is made from mahogany with gimbal mounts for the drum which holds the chronometer. Unusually, there are two spring-loaded wood screws attached to the box, which are provided to allow the chronometer to be fixed to a flat wooden surface. When not used they are retracted within the perimeter of the box and held there by springs. A key is provided which has two squares for releasing the gimbal lock and also for turning the wood screws. A second ratchet or 'tipsy' key is used to wind the chronometer. It runs for more than thirty-five hours but would have been wound every day. After being used as a test-bed to try the performance of different components it was finally presented to Breguet's friend Monseigneur Louis Belmas (1757-1841), Bishop of Cambrai, to whom it is inscribed, 'Premiere Piece ou la Comunication du Rouage au Régulateur S'Opère Sans Frotement. Exécutée en 1813 par Breguet Pour Mr Belmas ami de l'auteur N02741' ('The first piece in which the transmission from the train to the regulator occurs without friction. Made in 1813 by Breguet for Mr. Belmas friend of the author'). Emmanuel Breguet, in 'Breguet, Watch-makers Since 1775', paints a wonderful picture of Belmas as a collector who spent nearly 20,000 francs on Breguet watches between 1814 and 1822 and who described them in his letters to Breguet in the most affectionate terms. Breguet's aim in this piece was to incorporate an escapement in which there was no sliding friction produced at the point of impulse to the balance. This he achieved with limited success for, while it is true in one respect, he nevertheless introduced other frictions into the impulse geometry, which negated what he had accomplished. Ilbert Collection. View more about curator's comments Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript) Made by Breguet et Fils Paris, 1813 One-day marine chronometer with independent seconds indication and with an early lever escapement. Signature: At the bottom of the dial 'Breguet'. On the box cover 'No.2741 Breguet et Fils'. On the back plate 'Breguet et fils No 2741'. On the inner back cover 'Premiere Piece ou la Comunication du Rouage au Regulateur S'opère Sans Frotement Executée en 1813 par Breguet No 2741. Pour Mr Belmas ami de l'auteur'. This can be translated as: 'The first piece where the transmission from the train to the regulator occurs without friction. Made in 1813 by Breguet for his friend, Monseignor Belmas'(1). Box: The movement is contained in an open-ended brass drum with two narrow rings standing proud on the inside. The front plate rests on one and the movement is held by three dogs screws on the other. The dog screws are planted on the edge of the back plate. The inner back cover fits inside the back, it has two holes one for a winder and the other for a key, and two lugs fitting into slots in the drum. The drum is gilded on the outside. There is then a second cover fitting on the outside of the drum, again gilded on the outside. The dial is protected by a glazed cover fitting on the outside of the drum. The glass is flat, with a bevelled edge, and has a short blind hole to clear the cannon pinion. The cover is located by a peg in the drum fitting into a notch in the cover, and fixed by two screws going in from the side. The drum has a gilded band in the middle, on which are fixed a slide to operate the independent seconds train, and a squared arbor with female hole, held under a small plate, for setting the minute hand of the independent seconds train. There are engraved instructions for these. The drum containing the movement fits into a brass cradle heavily counterweighted with a hemispherical piece of brass, and lined with green silk. The cradle is gimballed in a well made and finely figured walnut box of the usual type. The gimbal assembly is locked by a threaded brass plug set in a brass plate in the centre of the bottom of the box. Using a male key this plug can be screwed in and out from underneath, the plug then locks in a hole in the centre of the hemispherical counterweight. The box can be screwed to a wooden surface by two spring loaded wood screws lodged in the side of the box. Each has a square head, and when the key is applied they can be forced down and turned to screw them into the chart room table, or a larger carrying box. They are normally held retracted by flat springs visible when the bottom of the box is removed. The box also has a lock with a shield shaped escutcheon plate, and a sliding cover in the lid over a round aperture, but no carrying handles. The cover is centred with a diamond shaped inset brass plate engraved 'No 2741 Breguet et Fils'. A large brass key is held under a brass clip inside the lid, it has a male square to operate the gimbal ring, and a femal.