- Museum number
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.
- Production date
Height: 12.55 centimetres
Width: 17.40 centimetres
Depth: 17.40 centimetres
- Curator's comments
Text from 'Clocks', by David Thompson, London, 2004, p. 134.
Breguet et Fils
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.
Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Breguet et Fils
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 female square to operate the spring loaded fixing screws. A brass tipsy key fits in a brass ring in the side of the box, with a small male square for hand setting and a female square for winding the going train fusee.
Dial & Hands: Solid silver engine turned dial, about 1.6 mm thick, held by a single screw at the centre in a recess in the drum containing the movement. The chapter rings for subsidiary seconds and independent recorded minutes are removable, being held by blued steel screws from the back. The central upper seconds dial and left hand central and lower sector dials are for the going train and the reserve of going (up-and-down) of the going mainspring respectively. The hands for these are of blued-steel. The large right hand central dial and small inset dial are for the independent seconds and minutes, these have gold hands as does the reserve of going sector below for showing the state of wind of the mainspring driving the independent train.
Ebauche Marks: the dial side of the front plate is punched 2741.
Frame: Full-plate construction with four turned pillars. There are potences screwed to the back plate for the lower escapement bearings. There is also a potence on the inside of the front plate for the upper bearings of two of the independent train arbors. A dust excluding collar is carried on the fusee arbor square inside a tube held with its foot on the arbor bearing. The brass parts are finished smooth with a mottle grain, the steel screws are grained.
Fusee, Barrel & Mainspring:
Fusee: 8-turn fusee with Harrison's maintaining power, the maintaining ratchet wheel of steel.
Barrel: flanged at the cover end, internal diameter 30.0 mm, height 12.0 mm. The set-up is mounted on the back plate.
Mainspring: tapered, height 11.7 mm, thickness 0.21 - 0.23 mm, a brace for the last turn, signed on the outside towards the outer end 'Vincent Juin 1813'.
Barrel arbor: diameter 10 mm, unsnailed.
Train: Apart from the offset planting of the second arbor, the train is of conventional construction and layout. The brass wheels are mottle grained, the steel pinions and arbors well finished and polished. The centre wheel has five crossings, the third and fourth wheels have four.
Jewelling: There is no jewelling in the front plate. The third and fourth rear pivots and those of the escapement are in pierced jewels, the latter with endstones set in straight grained steel plates. The back plate bearing has a cock for the independent train fly pivot which has a pierced jewel, otherwise this train has no jewels.
Escapement: A club tooth lever escapement with divided lift. The gold escape wheel, with four crossings, is recessed on both sides leaving only the ends of the teeth at the full width of the wheel. Every fifth tooth is drilled with a conical hole for oil retention, large at the back of the tooth and tapering to a small hole just below the locking corner. The exit pallet has a jewelled concave impulse plane, it is mounted on an arm which terminates with the notch. The entry pallet also has a jewelled concave impulse plane which is on a counterpoised arm pivoted on a centre line at about 45 degrees to that of the rest of the lever. A notch in the side of the pallet jewel engages with a gold pin on the main pallet frame where the entry pallet would normally be.
This system is to ensure that the impulse and locking friction are as near possible equal on each pallet. There is no draw. The fork and roller action is remarkable in that the normal impulse pin is replaced by a single long helical tooth formed on the edge of a gold roller. The fork is made to work with this, and has short horns and a gold dart, with a small steel roller to ensure safety action. The helix is so well made that there is no sign of rubbing, the transmission of impulse being by perfect rolling contact on the centre line. There is no sign of a compression contact on the helix, a most remarkable achievement for 1813. The fork is, however, very heavy and has a tail with a platinum counterpoise, the whole assembly having high inertia. Although the helical tooth on the impulse roller is wider at the tip than the root and curves around the roller the fork notch is apparently straight but inclined to the axis of the balance staff at about 15 degrees. In section it is of U shaped and polished along its length. Although the transmission of the impulse occurs virtually without sliding friction in this arrangement, a component of the impulse is directed parallel to the balance axis instead of at right angles to it, and so is lost. The helix must also be made long to reduce its inclination, thus adding to the problems of inertia.
Balance & Spring: A bimetallic two-arm balance of aerodynamic design so that all the compensation, poising and quarter screws are faired inside the rim to present the minimum air resistance. The non-ferrous component of the rim is a whitish grey metal considerably tarnished. The break in each rim section occurs midway between the arms, the screws are of red gold. The steel part of the rim has been blued. Diameter of rim 28.35 mm, thickness 2.78 mm.
A blued steel helical spring of just over 8 turns, with terminal curves at each end. The collet is brass with a slotted tail. The small steel stud is clamped by a plate with two screws on a steel platform and has three levelling screws. The platform is held by a central screw on a brass cock overhanging the balance.
Up-and-down indication for the going train: There is a reduced extension of the fusee arbor pivot in the front plate. This carries a two-armed steel piece held with a grub screw to index a brass sector carrying the indicating hand. The teeth of the sector are also acted on by a jumper spring.
Train Counts and Beat Rate:
Great wheel 65 (fusee)
Centre wheel 80 pinion 15
Third wheel 75 pinion 10
Fourth wheel 75 pinion 10
Escape wheel 16 pinion 10
Beat per hour: 14,400
Motion work: cannon pinion 12
minute pinion 10 minute wheel 36
hour wheel 40
Independent seconds mechanism:
Driven by a small going barrel and consisting of four wheels and five pinions, planted on the edge of the frame partly between the plates and partly in a potence screwed to the front plate. The last pinion carries a steel two armed flirt on the outside of the back plate. This can be held up by a pivoted arm with a two position jumper, operated by the slide on the edge of the movement drum. When freed it turns until it meets a brass slotted turret carried on the escape wheel arbor. This releases the flirt once per second, or at every fourth swing of the balance, and allows the independent train to advance. There is no means of returning the independent seconds hand to zero except by stopping it there, but the recorded minutes can be reset. A steel shaft carried on a bracket on the pillar carries a squared tube for the resetting male key. Motion is transmitted in a clockwise direction via a steel contrate wheel to a pinion on the end of an arbor passing through a hollow pinion. The latter pinion turns once in thirty minutes when the independent train is running, the recording hand being carried on the end of its central arbor. There is a tiny ratchet and click system on the resetting arbor, before the contrate wheel, so that resetting can occur only forwards. This is to prevent the flirt being turned backwards and possibly jamming in the turret if the friction in the hand setting mechanism should be greater than the driving torque. It also prevents the resetting arbor from rotating with the independent train while the latter is running.(2)
Barrel and Mainspring:
Barrel: a going barrel, diameter 13.3 mm.
Mainspring: Two mainsprings, both with height 3.65 mm and thickness 0.12 mm. The springs are separated by a central brass section in the middle of the barrel. Each spring is numbered and signed "penpin mai 1812" and there are dots inside the barrel to indicate which side each spring should be fitted.
Barrel arbor: diameter 4.0mm, solid and unsnailed. The end of the barrel arbor towards the front plate has an extended square, and then a pivot running in a cock on the front plate. A steel arbor fits on the square, threaded on its outside and with a steel nut running on the thread, edged with brass. A steel piece standing on the barrel cover fits in a slot in the steel nut. This arrangement operates as both up-and-down indicator and stop-work. When the arbor turns during winding the nut is carried towards the barrel until a projection on the threaded arabor encounters a projection on the underside of the steel nut. When the barrel turns during running the nut moves away from the barrel. A lever with an inclined plane in the path of the nut operates the indicator hand through another lever and pivoted arbor. The first lever is carried on an arbor pivoted in the frame with a brass piece squared to the end projecting through the back plate. This is moved into the path of the independent seconds flirt to hold up the train before the mainspring is completely run down.
Independent seconds train:
Great wheel 72 teeth (barrel)
Second wheel 60 pinion 12
Third wheel 50 pinion 10
Fourth wheel 60 pinion 10
Fifth wheel 50 pinion 10
Sixth pinion 10 leaves with a two-arm flirt engaging with a turret of 8 slots on the escape arbor. This train can be stopped or started at will, without affecting the going train, by a push-piece in the side of the drum.
Winding Mechanism: The going train fusee is key wound in the normal way but the independent seconds train is wound by a folding key mounted on the squared barrel arbor.
Box: base 174.0 mm square, overall height 125.5 mm.
Drum: diameter 87.4 mm, overall height 39.9 mm.
Movement: front plate diameter 83.1 mm.
back plate diameter 80.2.
frame height 18.5 mm.
Provenance: Formerly in the Ilbert Collection. Purchased by Ilbert from Contarde in 1934. Presented by Gilbert Edgar CBE in 1958.
(1) Monseigneur Louis Belmas, Bishop of Cambrai. Although completed and inscribed with the date 1813, it appears that Breguet initially used this chronometer as an experimental piece and did not supply it to Monseigneur Belmas until 1822, see Emmanuel Breguet, Breguet, Watchmakers since 1775, The Life and Legacy of Abraham- Louis Breguet (1747-1823), Paris 1997, pp275-276.
(2) The independent seconds mechanism was invented by Moyse Pouzait in 1777.
Exhibited: "Pendulum to Atom" under the auspices of The Worshipful Company of Clockmaker's at Goldsmiths' Hall, London, October 1958.
L. J. Gay Lussac and Arago, 'Chronometres de Breguet', 1819.
Daniels, 1975, pp.85-86.
Bertele 1981, p.202;
E. Jacquet, 'Le Musee D'Horologerie de Geneve, Catalogue', Geneva, 1952, pp.181, 182, fig.104.
Emmanuel Breguet, Breguet, 'Watchmakers since 1775, The Life and Legacy of Abraham- Louis Breguet (1747-1823)', Paris 1997, p.276.
- On display (G39/dc10)
- Acquisition date
- Acquisition notes
- The Ilbert Collection of clocks, prints and other related material was destined to be sold at Christie's auction house on 6th-7th November 1958. As a result of the generous donation of funds by Gilbert Edgar CBE the sale was cancelled and the material purchased privately from the beneficiaries of the Ilbert Estate.NL1Ilbert's watches were then acquired with further funds from Gilbert Edgar CBE, public donations and government funds. These were then registered in the series 1958,1201.
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.2066 (Ilbert Collection)
Previous owner/ex-collection number: N331/2 (Ilbert Ledger)