Marine chronometer by Bernard Callier

Description — British Museum

Marine chronometer; spring detent escapement, later Earnshaw type; movement in nickel brass bowl and mahogany box; flat engraved silvered brass dial, subsidiary seconds; blued steel hands; tipsy-key in box.

Curator's comments — British Museum

Compare with 1958,1006.1951 Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990) Made by Callier, c. 1880 Marine Chronometer Signature: On the dial 'Callier No. 763.(1) Box: The movement contained in a deep white metal (probably a nickel brass) bowl, with a heavy levelling weight screwed to the inside of the bottom. The winding hole is protected by a cover pivoted on a screw, which can be swung aside for winding. The heavy dial ring is turned to fit into the bowl with a wide flange resting on the top and screws at the side for fixing. The glazed bezel is missing. The gimbal ring, its lock and the box furniture are also made of the same white metal as the bowl. The mahogany box has a glazed panel in the top under a hinged lid with catch operated by a push-piece at the front, similar to English practice. The front is centred with a rectangular ivory plate engraved 'Callier 763'. There are the usual lock and carrying handles. A tipsy key similar to that of Auguste Berthoud.No. 293, registration no. 1958,1201.1951, fits in a hole in a corner gusset. There is also a slot in the right-hand side of the top of the box and lid, presumably for another type of key. Base 153 mm square, h. 153 mm. Dial and hands: Flat engraved silvered brass dial, the engraving filled with black wax, secured by a single screw in a recess in the dial ring. The subsidiary seconds dial is in the upper half, and a reserve of going sector in the lower half. Blued steel hands. Movement: Dial ring flange diam. 82.4 mm (reduced to 74.5 mm); dial ring thickness 12.4 mm; front plate diam. 62.9 mm; back plate diam. 62.9 mm; frame h. 16.7 mm. Frame: Very similar ébauche to that of Auguste Berthoud No. 293, 1958,1201.1951. The back plate secured by grained steel screws. The brass parts are considerably oxidised but were originally finished with a scratchy polish. Fusee: Similar to 1958,1201.1951, but with different stop work. The mainspring is missing. Going train: Similar to 1958,1201.1951, but the great wheel assembly held together by a flange and pin, with an integral index piece for the stop-work. Jewelling: The pivots of the fourth and escapement arbors in pierced jewels, those of the escapement with endstones. A diamond endstone in a blued steel ring in the balance cock. The jewel settings are of brass with flanges similar to English jewelling. Escapement: Similar to that of 1958,1201.1951. The brass escape wheel gilded, the teeth slightly cut by impact with the impulse jewel. Both the detent and the banking assembly are missing. Balance: A Frodsham/Hartnup bimetallic balance made up of a series of bimetallic strips screwed together at their ends and overlapping each other with a small clearance. Vertical threaded rods are fixed to the free ends of the final bimetallic strips for compensation weights, now missing. This type of balance is designed to cause the compensation weights to move towards the balance axis more rapidly in heat than they move away in cold, thus giving the possibility of eliminating the middle temperature error. There is an additional steel crossbar carrying brass timing and poising screws. The whole is fixed to a brass collet on the balance staff by a pair of steel screws. Diam. 34.5 mm; h. 12 mm (approx.). Balance spring: Helical spring made of a palladium alloy, with a very high finish. 11 turns with a short terminal curve to the collet, clamped concentrically at full turns to a stud with 3 levelling screws. Screwed to a brass arm fixed to the underside of the balance cock. Going-train counts: Great wheel (fusee) 84 teeth, 7½ turns of groove Centre pinion 12 leaves, wheel 80 teeth, 5 arms Third pinion 10 leaves, wheel 75 teeth, 5 arms Fourth pinion 10 leaves, wheel 80 teeth, 5 arms Escape pinion 10 leaves, wheel 15 teeth, 3 arms Beats per hour: 14,400 Motion work: Cannon pinion 14 leaves, minute pinion 18 leaves (brass) Hour wheel 54 teeth, minute wheel 56 teeth Provenance: Ilbert Collection. Presented by Mr Gilbert Edgar c.B.E. in 1958. There seems to be no reference to this chronometer in C.A. Ilbert's inventory notebooks. Note: (1) Tardy 1971, lists a Bernard Callier, Chronometers, in Paris 1848. Quai St. Michel, 1879. He quotes that he succeeded Winnerl in 1870, invented a new compensation balance for chronometers in 1879, received the cross of the Légion d'Honneur in 1893 and was succeeded by Emmanuel Boudeaud. Bibliography: Bertele 1981, p. 241.