- Museum number
GOLD CASED VERGE STOP-WATCH WITH CENTRE-SECONDS, GRIDIRON COMPENSATION AND BOLT-AND-SHUTTER MAINTAINING POWER.
Full-plate; fusee; bolt and shutter maintaining power.
Verge escapement; gilded-brass 3-arm balance; gridiron temperature compensation.
White enamel dial; hours I-XII, minutes 5-60; winding hole at II.
Gold hour and minute hands; blued-steel centre-seconds hand.
Gold case with glazed front and back, rear glass missing.
- Production date
Diameter: 38.60 millimetres (back plate)
Diameter: 49 millimetres (case)
Diameter: 41.80 millimetres (front plate)
Height: 30.80 millimetres (case)
Thickness: 10 millimetres (movement)
- Curator's comments
- Comment from Richard Good, Catalogue of Watches in the British Museum. Vol. V (Unpublished manuscript)
Made by Ferdinand Berthoud, 1763
Signature: Around the edge of the dial plate 'Ferdinand Berthoud Inv et fecit 1763'. On the back plate 'Ferdinand Berthoud á Paris No 417'. The dial also signed.
Case: Gold consular style case with glazed back not opening, the glass missing, the glazed front bezel with book hinges of five knuckles, and a catch operated by a gold covered push-piece.
Stirrup pendant with chased ring. On the pendant is an indistinct assay mark. Diam. 49.0 mm, h. over glasses 30.8 mm.
Dial and hands: Curved enamel dial signed on the back 'CuJl' with one positioning foot passing into a hole in the front plate, and a retaining screw near the figure III. The dial pierced for winding and inscribed Ferdinand Berthoud.
Gold minute and hour hands, blued steel sweep centre seconds hand.
Front plate diam. 41.8 mm; back plate diam. 38.6 mm; frame th. 10.0 mm.
Frame: Full plate construction built up on a massive front plate, which also serves as the dial plate. Four turned pillars, the back plate retained by pins. The front plate recessed under the dial to provide space for the motion work, the case catch and spring, the setting-up-work, the bolt and shutter maintaining power and also the three cocks providing the lower bearings of the offset centre, and third and fourth arbors. The minute wheel and pinion arbor also pivoted under a cock. The movement hinge let into a slot in the edge of the front plate. The brass components nicely gilded.
Fusee: Keywind fusee pivoted between the front plate and a cock on the outside of the back plate. English type of stop-work, the setting-up-work under the dial on the front plate, the barrel arbor with an extended square on that end only. Bolt and shutter maintaining power acting on the teeth of the second wheel. A brass plate pivoting on a steel spring acting on the brass plate then provides the power to return it; this keeps the watch going during winding.
Going train: The centre wheel offset, the motion work driven by a pinion on the third arbor. The fourth wheel and pinion planted at the centre of the frame and carrying the seconds hand on an extended arbor. The fourth wheel meshing with a steel wheel on the arbor of the contrate wheel. The centre and fourth wheels and the steel wheel on the contrate arbor appear to be of the same fairly coarse pitch. The third wheel is of finer pitch. All the brass wheel teeth show signs of having been at least finished with a file, perhaps actually marked and filed out completely. The brass wheels are gilded, the general finish of the train of very ordinary quality.
Escapement: Typical continental verge escapement with adjustable slide for equalising the drops. The verge itself is a later replacement of poor quality and finish.
Balance: Plain gilded brass three-armed balance of large diameter, 27.3 mm, with a stop pin set in the outer edge of the rim. Two pins set in the top of the back plate in the path of the one on the rim of the balance limits the balance amplitude to a maximum of about 230°.
Balance spring: Steel open coiled spiral spring of about 2¼ turns, in poor condition, and seems likely to have been either a later replacement or the original spring much altered and deformed.
Thermal compensation: A gridiron system, made up of six steel rods and six brass rods built into a framework, moves a brass block set on the free ends of the two middle brass rods relative to the frame. This frame is screwed to the back plate by two plain steel screws at one end and a shoulder screw at the other. The effective length of steel relative to brass is 88.6 mm of steel to 89.5 mm of brass; this is duplicated on either side of the centre line. The movement of the brass block is further magnified by a pivoted lever on a stud on the edge of the back plate, in the ratio of about 7:1. This can be varied by moving a brass block fitted onto the longer arm of the lever.
Above the balance staff upper bearings an index system is pivoted between two superimposed cocks screwed and steady pinned to the balance bridge. This is moved by the brass block mentioned above, against a light return spring. The index pins embrace the last turn of the balance spring and are formed on the end of a piece of brass pointing down from a polished steel plate. This plate can be moved in relation to the compensation system for mean time adjustment.
Balance stop: A polished steel arbor is pivoted near the edge of the frame at the 5 o'clock position on the dial. A short steel lever mounted on the squared end under the dial projects through the edge of the movement. On the other end projecting through the back plate is squared a thin brass lever to stop or release the balance at will, by acting on the outer edge of the balance rim.
Great wheel (fusee) 54 teeth
Centre pinion 12 leaves, wheel 64 teeth, 4 arms
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 48 teeth, 4 arms
Contrate pinion 24 leaves, wheel 32 teeth, 4 arms
Escape pinion 8 leaves, wheel 15 teeth, 3 arms
Beats per hour: 14,400
Motion work: Driven by a pinion of 8 leaves on the third arbor of the going train meshing with a brass cannon wheel of 64 teeth turning once per hour and mounted with a friction device below a steel wheel integral with the cannon pipe.
The wheel on the cannon pipe 30 teeth Minute wheel 30 teeth, minute pinion 6 leaves Hour wheel 72 teeth
The only provision for setting the hands to time is either by stopping the watch with the balance stop and restarting it again at the correct moment as indicated by the hands, or else by attempting to push the minute hand round with the risk of breaking it or damaging the other two hands.
The minute hand is provided with a pin set in the hole of the boss passing into a slot in the steel cannon pipe. On pushing the minute hand the cannon pipe and steel wheel turn against the friction spring, under the brass cannon wheel, and the remaining motion work and hour hand turn as well. The friction device is so strong in action that any attempt to alter the hands by this method would have a disastrous effect on the rate of the watch.
Provenance: Ilbert Collection.
Note: Whilst it appears that this watch was intended by its maker to keep a close rate, there seems little doubt that it would have kept only marginally better time than a common verge watch of the period if this was well executed. The compensation would have suffered from stick-slip friction, and the balance and spring would have suffered from a distinct lack of isochronism.
This watch is, however, extremely interesting as being almost certainly the first Continental watch to be fitted with temperature compensation ; also it is one of only two watches known with bolt and shutter maintaining power.
Harrison's maintaining power predates this watch and was fitted to the 'Jefferies' watch made under John Harrison's control in 1752. However, the first watch whose details were made public that contained Harrison's maintaining power was Harrison's watch known as H4, and the mechanism of this watch was not made public until after the manufacture of Berthoud's watch.
The case has been modified from a more conventional case which has been deepened to provide room for the temperature compensation device. Gould in 'The Marine Chronometer' (p. 170), refers to the first pocket watch with a compensation curb as generally stated to have been sold by Berthoud to George III in 1763.
Bibliography: A. Randall, ' Ferdinand Berthoud ', AH, June 1986; A. Randall, 'Analyse du Traité des Horloges Marines et du Supplément au Traité des Horloges Marines', ANCAHA, no. 30, Printemps 1981 ; A. Randall, 'Berthoud et l'influence de ces contemporains', Chronométrophilia, no. 17, Winter 1984; Ferdinand Berthoud 1727-1807, Horloger Mécanicien du Roi et de la Marine, exh. cat., Musée international d'horlogerie, La Chaux-de-fonds.
- Not on display
- Latest: 3 (2017)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.0276 (Ilbert Collection)
Previous owner/ex-collection number: Q196 (Ilbert Ledger)