- Museum number
- 1958,1006.2121
- Description
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Marine chronometer; constant force escapement with three detents; movement in brass canister gimballed in oak box; tipsy key in corner; heavy brass engraved and silvered dial; blued steel hands.
- Production date
- 1795-1805
- $Inscriptions
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- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Breguet, c. 1800
Marine Chronometer
Signature: On the dial 'Breguet No 428'.
Box: The movement contained in a brass canister, the top half sliding into the bottom, and with a bayonet fixing and a single locking screw. Both ends of the canister are glazed, and there is a small brass levelling weight screwed to the edge of the bottom. The bottom half of the canister is gimballed in an oak box. The gimbal ring is square, with rounded corners, and there is no lock, it is pivoted on brass screws set in the wood of the side of the box, with their ends formed into pivots. There is a-tipsy key numbered 4847, fitted in a corner. The sides of the box are fitted together with dovetail joints, and there is a sliding panel over a circular aperture in the top with an inset diamond-shaped brass plate numbered 426. The box has the usual lock and carrying handles, and there is a brass limit stop for the top, fitted on the outside. Base 208 mm square, sides 204 mm square, h. 187 mm.
Dial and hands: The dial a heavy brass plate, engraved and silvered on a granular surface, the engraving filled with black wax. The dial is attached directly to the front plate by four turned pillars and pins, leaving room for the under dial work, at the back it is engraved or punched 428. The indications are as follows: the three large central dials, starting at the top and going round clockwise, are for seconds, minutes and hours. The sector at the bottom is for reserve of going and the small dial below this records each time the machine is wound. The sector on the upper left-hand side indicates temperature, and the small dial beneath the hand indicates each time the temperature rises above a certain value. The right-hand small dial hand advances one division each time the machine is twisted as in starting. Winding and hand setting are controlled by two squared arbors of different sizes, through the dial and holes in the glass; these holes are normally covered by brass caps. Hands are of blued steel.
Movement:
Front plate diam. 100.3 mm; middle plate diam. 100.3 mm; back plate diam. 100.3 mm; frame h. over the front and middle plates 37.3 mm; frame h. over the middle and back plates 19.1 mm; frame h. over the front and back plates 53.5 mm.
Frame: Built up in two layers. The front and middle plates are separated by four cylindrical pillars riveted to the middle plate and with the front plate held by pins. Between these plates are planted the two barrels, the winding work and the going train, as far as and including the fourth arbor. All the escapement and balance components are planted on the back plate between a series of cocks and potances and the plate. The back plate has four cylindrical pillars which pass into holes in the middle plate, which is retained by taper pins. Each plate is numbered 428.
Going barrels: Each drives the centre arbor. Each barrel arbor carries a large brass winding wheel which meshes with a common steel wheel on the winding arbor having a steel click pivoted in the frame. Breguet's stop-work is fitted on one barrel cover, the reserve of going indicator operating mechanism on the other. The latter mechanism is similar to that described for Breguet et fils No. 2741, registration no. 1958,1201.2066, except that the nut moving up and down on the threaded piece on the barrel arbor is cone-shaped and brass. The arm, spring loaded against the side of the cone, moves towards or away from the arbor as the cone moves up and down. This motion is transferred to a toothed sector engaging with another on which the indicating hand is carried. Stop-work is also incorporated in the reserve of going operation mechanism, so that each mainspring can be set up a pre-determined amount. The mainspring in the barrel with reserve of going is marked 'D Juin '67'. It is hooked with an eye to a steel hook piece held by a screw to the barrel wall partly in a rectangular slot as for solid hooking. The arbor has a brass unsnailed boss and steel hook. The other barrel is allowed four turns of going by its stop-work and is set up 4½ turns. Its spring is also signed 'D Juin '67', otherwise it resembles the other in every detail. Each spring has a bride. The barrel with reserve of going indication has had two teeth carefully replaced.
Going train: The centre arbor is planted at the centre but does not drive the motion work or any of the hands. These are driven by a pinion on the third arbor meshing with the wheel turning once per hour and carrying the minute hand. The centre and fourth wheels are riveted to their pinions, the third to a collet on its arbor. The general quality of the finish is good without being remarkable.
Jewelling: Only the pivots of the escapement run in jewelled bearings. The balance staff has conical pivots running in the usual jewelled holes with endstones. The remontoire wheel and fly arbor pivots run in pierced jewels, but the pivoted remontoire detent has tapered pivots with flattened ends running in blind holes in pieces of ruby. The pieces of ruby are set in detachable brass strips, the one on the inside of the frame with an endshake adjusting screw.
Escapement: An example of Breguet's constant force escapement employing three detents. A pivoted counter-poised detent has a gold helical spring with terminal curves colleted to its arbor, and is held locked on the locking stone of a conventional spring detent having banking and a passing spring. The latter detent is released by a roller on the balance staff at the correct moment for the pivoted detent to be released in its turn, to transmit impulse to the balance. The free acting end of the pivoted detent is formed into a crescent, at the far end of which is set a piece of ruby. This piece of ruby contacts a gold block set on an arm attached to and curving round the balance staff. At the end of impulse the end of the pivoted detent encounters the end of a third detent on which is locked a fly. The fly is the last pinion of the going train, and is driven by a wheel on whose arbor is carried the rewinding wheel which has a series of teeth with cycloidal acting surfaces to rewind the pivoted detent. They act on a piece of ruby set in a short piece standing off the crescent of the pivoted detent.
The gold helical remontoire spring has a certain set up that can by varied by moving a pointer to which it is fixed over a scale. There are also several screws for adjusting the different functions (see also Gould 1923, p. 142).
The whole escapement and balance assembly is mounted on a separate plate and can be removed as a unit. A screw is provided that operates a fourth wheel lock that should be engaged before this plate is removed.
Balance: Bimetallic two-armed balance of Arnold 'z' type. The bimetallic rim sections each secured by two steel screws to an upstanding integral brass block on the end of the brass crossbar. Brass quarter nuts are fitted on studs, and brass double slotted screws on top at the ends of the arms. At the free end of each rim section is fixed a short steel piece with three tapped holes for a small brass screw to adjust the compensation. The balance is secured by two screws to a brass collet on the staff. Diam. of rim 35.1 mm, h. 3.5 mm.
Balance spring: Blued steel helical spring of 8 turns, with terminal curves. The brass collet has a slotted counterpoising tail, and a clamping screw for the collet on the staff. The stud is clamped under a steel strip on a brass stand having three levelling screws and a central clamping screw.
Going-train counts:
Great wheels, each 120 teeth, one turn in 10½ hours, the stop-work allowing four turns of going
Centre pinion 8 leaves, wheel 84 teeth, 4 arms, 1 turn per 42 minutes
Third pinion 12 leaves, wheel 72 teeth, 4 arms, 1 turn per 6 minutes
Fourth pinion 12 leaves, wheel 75 teeth, 4 arms, 1 turn per minute
Escape pinion 10 leaves, wheel 16 teeth, 4 arms
On the arbor of the escape wheel and pinion a wheel of 96 teeth, 4 arms, meshes with the fly pinion of 6 leaves. Beats per hour: 14,400
Stop work:
A brass pinion of 6 leaves on the arbor driving another of 8 leaves.
Winding work :
A steel winding wheel of 25 teeth meshes with two brass wheels, one on each barrel arbor, of 50 teeth each.
Motion work: Driven by a pinion of 12 leaves on the third arbor, making one turn in 6 minutes. This drives a wheel of 120 teeth on the right-hand side of the dial. This wheel has a coarse pitch wheel of 33 teeth mounted friction tight on its arbor, and carrying the minute hand. The wheel of 33 meshes with another similar on the squared hand-arbor. The hand-set arbor is integral with a pinion of 10 leaves meshing with another wheel of 120 teeth carrying the hour hand.
During normal running all these wheels turn together, for hand setting they all turn except the wheel of 120 meshing with the driving pinion of 12 leaves on me third going train arbor.
Thermometer: The sensitive element is a semicircular bimetallic strip made of steel and a whitish grey metal. The free end of the bimetallic strip carries a light pawl to index a wheel of 40 teeth each time the temperature cycle goes above a certain predetermined value.
Twist indicator: A privoted crossbar at the top has two weights, one at each end, and a spiral return spring. It carries a broken piece and a wire replacement to index a wheel of 40 teeth if the machine is given a twist as in starting.
Provenance: Ilbert Collection; in his inventory notebook Ilbert records the acquisition of this chronometer from Bennett in 1953. He mentions a letter from the firm of Breguet in 1953 giving the date of manufacture as 1821. In this letter M. G. Brown states that the record of sale of the chronometer was not entered in their old sales book and that as a result a Certificate of Origin could not be issued. [The British Museum has this letter.] Presented by Mr Gilbert Edgar C.B.E. in 1958.
Exhibited: 'Pendulum to Atom', under the auspices of The Worshipful Company of Clockmakers at Goldsmiths' Hall, London, October, 1958; Musée International d'Horlogerie, La Chaux-de-Fonds, Switzerland May-September 1976, see exhibition catalogue, pp. 42, 53.
Bibliography: Daniels, 1975, pp. 87, 171; Bertele 1981, pp. 158, 159, 160; Gay Lussac and L. J. Arago, 'Chronometres de Breguet', 1819.
- Location
- Not on display
- Exhibition history
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Exhibited:
2008 1 Feb-16 Apr, Liverpool, Prescott Museum, Lost Time
1976 15 May-20 Sep, Switzerland, La-Chaux-de-Fonds, Musee Internationale d'Horologie, Abraham-Louis Breguet
- Condition
- Latest: 2 (Oct 2015)
- Acquisition date
- 1958
- 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.NL1Purchased by Ilbert in 1953.
- Department
- Britain, Europe and Prehistory
- Registration number
- 1958,1006.2121
- Additional IDs
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Previous owner/ex-collection number: CAI.2121 (Ilbert Collection)
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Previous owner/ex-collection number: Q283 (Ilbert Ledger)
