Chronometer no. 3157 by Abraham Louis Breguet & Fils

Catalogue description — Royal Museums Greenwich

Breguet et Fils, Paris, c.1822 No.3157 2 day marine chronometer in mahogany box For biographical details of the firm of Breguet of Paris, see pp.xxx Box/Mounting Two-tier, plain mahogany box measuring 175mm high, 222mm wide, and 190mm deep. The top of the box has an inset lid with side-pin hinges allowing it to open to about 120°. The lid is inlaid with a brass, diamond-shaped plaque, engraved: “3157”, and opens to a circular glazed panel retained with narrow brass bezel, screw-fixed from the underside. The front of the upper half has a push button brass catch for the lid with brass, circular escutcheon and brass spring inside the upper half to ‘jump’ the lid open when the button is pressed. In side the back of the upper half is inscribed in ink: “3157 / Novembre 1878” (?). The lock on the lower half is stamped on the upper edge: “328”, and has an oval, brass escutcheon on the front. The box has a full-width, ‘butt’-type, hinge and a brass strut on the right hand side, restraining the upper half to 90°opening. There is a raised step running around the inside of the junction on the lower half, mating with a rebate in the junction of the upper half and forming a dust seal when closed. The box fittings are similar to the standard French type, with brass drop handles on the sides and lacquered brass gimbals with a narrow, straight-sided bezel retained with two side screws and having a brass sight ring and beveled flat glass over the dial. The centre body of the movement-housing doubles as the brass edge of the movement and has a barleycorn knurled beading running round the outside. Both bezel and bowl are fixed to it with a pair of screws. The thick, oval gimbal ring has a concave inner edge to the upper surface, and two flat brass arms can be swung in from the rear left and front right corners of the box to engage with blocks on the bowl, securing the gimbals. When these arms are in place and the lid is closed, cast brass pegs fixed up inside the upper half of the box prevent them from swinging open. When these arms are not in use they are swung out and stowed on little brass pillars on the edge of the box. The heavy brass bowl has an upstanding beading on the base, within which are the two winding holes. No direction-of-winding arrows now present. There are two small plain holes drilled into the edge of the beading, with no apparent function. The Breguet-type ratchet key is stowed in a standard, Breguet-type boxwood socket in the rear right of the box, and has a brass retaining fork fixed up inside the upper half which secures the key in place when the box is closed. In the right and left sides of the lower half of the box there are vertical holes going through to the base, intended for wood screws to fix the box to a wooden surface when in use on board ship. The underside of the box is plain, without baize covering. Dial and hands The 98.6 mm Ø, engraved and wax-filled, French-silvered matt-finish dial is fitted snugly in a rebate in the front of the brass edge, fixed with one screw at the top of the seconds dial, into the train bridge beneath. To free the dial from the brass edge, a pin hole in the brass edge allows a pin to be inserted, which enters a small ramped groove at the 6 o’clock’ position on the back of the dial, forcing it up and releasing it. The movement is attached to the brass edge with three steel screws from the inside. The subsidiary hours and minutes dial has roman hour numerals and arabic ten-minute figures with a large seconds dial below having arabic ten second figures and with straight batons at five-second intervals. The dial is signed across the centre: “Breguet et fils Hgers de la Marine / Royale / No.3157 ”. Above the upper dial is engraved: “F” and “DÉPÔT DE LA MARINE”. On the left of the upper dial is a stop-start control lever marked: “BALANCIER / Fixe / Libre”. The back of the dial is scratched: “3157 / F”. Blued steel demi-lune hands with a fine, blued steel pointer seconds hand with a counter-poised tail. Movement Breguet Grande Horloge Marine format double-barrel calibre movement with the train mounted under a bridge on the front of a central brass plate with twin going barrels mounted on a large double-cock on the rear of the plate. The general level of finish of the movement is high with most movement parts flat-polished. The underside of the main plate is stamped: “3157” next to the foot of the fourth wheel blocking detent. and “13” near the barrel. The double going barrels have spring-clicks alongside the ratchet wheels on the cocks, and brass and steel Breguet-type stopwork mounted on the caps of both barrels. There is a four-wheel train with the two great wheels on the barrels, the greats both meshing with the second (‘centre’) wheel in a straight line, the second pinion being . The wheels are all brass with the fourth wheel run in a cock on its lower pivot. There is a meshing inspection hole by the 2nd/3rd pivot in the main plate and by the 3rd / 4th pivot in the bridge. Escapement, balance, spring and jewelling Breguet-type spring detent escapement with double-spring detent mounted, via a brass block with 2 screws, on a brass cock. The cock, which has been moved a couple of times (probably during manufacture. Plugged holes for screw and steadies), has “38” scratched on its foot, The escapement as a whole is mounted on the ‘Navette’-shaped escapement platform. The platform is scratched “R” and “L” by the two steel steady pins, on the underside (distance between pin centres: 51.0mm) and there are five unused holes in the navette baseplate adjacent to the escapewheel (possibly originally for escape-locking device, now superseded by fourth wheel detent lock). The detent has a screwed-on, gold passing spring running alongside the detent blade, and with a polished-steel locking ‘stone’. The impulse roller has a steeply raked, pale pink impulse jewel with cut out opposite for poising, and the discharge roller has a deep red stone inset. The balance staf