- Museum number
SILVER PAIR-CASED SUBSIDIARY SECONDS POCKET-CHRONOMETER WITH SPRING DETENT ESCAPEMENT AND SUGAR-TONGS TEMPERATURE COMPENSATION.
Spring detent escapement; sugar-tong compensation curb.
Green watchpaper with printed inscription on obverse and manuscript on white reverse.
- Production date
- 1800 (case)
Diameter: 48.90 millimetres (dial)
Diameter: 51.90 millimetres (inner case)
Diameter: 60.20 millimetres (outer case)
Diameter: 52.45 millimetres (watch-paper)
Thickness: 25.60 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Thomas Earnshaw, 1800
Signature: On the back plate 'T. Earnshaw Inv' et Fecit No. 504', on the barrel bridge 'LONDON 3163'.
On the dial below the figure XII 'THOMAS EARNSHAW INVT ET FECIT N° 504'.
Case: Silver pair cases with the London hallmark for 1800 and the maker's mark T.C. surmounted by an axe, the mark of Thomas Carpenter. Outer case diam. 602 mm, h. 196 mm, with five-knuckle hinge; inner case diam. 520 mm, h. 250 mm, over glass. Watch paper in case back.
Dial and hands: Flat enamel dial, similar in appearance to that of registration nos 1958,1201.1592 and 1593.
Gold hands also similar in appearance to those of 1958,1201.1593.
Dial plate diam. 47.4 mm; front plate diam. 42.9 mm; back plate diam. 42.4 mm; frame h. 7.5 mm.
Frame: Similar full plate construction to most other watches by Earnshaw. The brass parts gilded, the steel parts well finished and blued. The movement retained in its case by a single positioning peg in the dial plate, and two screws going through the inner case and into the dial plate. One frame pillar shortened flush with the back plate and with a screw to retain the back plate, to allow free movement of the sugar tongs assembly for mean time regulation. Cock engraved with scrolling foliage and a flower. Scratched on the dial plate 'John Hill Taunton 1852 FHV Taunton Feby 8 1839'.
Fusee: Similar to 1958,1201.1592 except that the steel parts are prepared and finished to a high standard. The barrel arbor with an extended square at both ends, the barrel itself without a flange but waisted at the lower end to miss the teeth of the great wheel; this done after gilding. Blued steel maintaining detent returned by a piece of brass wire pointing downwards from a hole in the back plate.
Going train: The third and fourth wheels gilded, the ends of the pinions and the arbors finished and polished as well as the pivots and acting parts of the pinions.
Jewelling: The pivots of the escape pinion arbor and balance staff only in pieced jewels with endstones. The endstone in the balance cock a piece of ruby set in a blued steel disc.
Escapement: Apparently as originally fitted in every detail and similar to 1958,1201.1592. On the impulse roller only the impulse face polished.
Balance: Steel three-armed balance, polished on both sides, triangular section arms. Diam. 25.0 mm, h. 0.55 mm.
Balance spring: Dull, blued steel, flat, open coiled spiral spring of 7⅓ turns, without overcoil or terminal curve and pinned to a brass stud on the back plate.
Thermal compensation: Sugar tongs bimetallic strips mounted on a brass plate with central open boss held with two blued steel screws in the hole in the back plate concentric with the balance axis. The edge of the brass plate having a pointer moving over an engraved sector on the edge of the back plate for mean time regulation. Each bimetallic strip carries an index pin at its extremity embracing the last turn of the balance spring. The two index pins move towards each other in heat and apart in cold.
Great wheel (fusee) 62 teeth, worn and leaning backwards
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 70 teeth, 4 arms
Escape pinion 7 leaves, wheel 15 teeth, 3 arms
Beats per hour: 18,000
Cannon pinion 12 leaves, minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Webster in 1930.
The watch paper is of J. Greenhatch, Manchester, and written on the reverse 1496 over March 45 and a dollar sign with an extra vertical stroke.
- Not on display
- Exhibition history
1998-1999 04 Dec-18 Apr, London, National Maritime Museum, Arnold & Earnshaw, Pioneers of the Chronometer
Latest: 2 (2017) Two screws for securing movement in case missing.
2 (Oct 1995)
- Acquisition date
- Acquisition notes
- Following the successful acquisition of the celebrated Ilbert collection of clocks (1958,1006 collection), prints and other related materials made possible by the generous donation of funds by Gilbert Edgar CBE Ilbert's watches were then acquired using funds provided by Gilbert Edgar, public donations and government funds.
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.1733 (Ilbert Collection)
Previous owner/ex-collection number: K46 (Ilbert Ledger)