Thomas Earnshaw Marine Chronometer No. 245
Record status
Individual type · partial
Period
1790-1800
This one-day marine chronometer by Thomas Earnshaw, dated by the British Museum to between 1790 and 1800 (and circa 1795 in catalogue comments), is built with an Earnshaw spring detent escapement.
The movement is cased in a brass canister with a solid gimbal ring, set within a later mahogany outer box edged with red velvet. Its silvered dial plate is directly engraved and filled with black wax, featuring Roman numerals, blued steel hands, and a subsidiary seconds dial. Research cited in the museum record identifies its use by Captain Henry Meriton aboard the HEICS Exeter during early 19th-century voyages to China.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Type
- One-day marine chronometer
- Escapement
- Earnshaw spring detent
- Dial Signature
- THOs EARNSHAW LONDON INVT et FECIT No 245
- Place recorded
- United Kingdom
- Maker / attribution
- Thomas Earnshaw
- Replacement Mainspring
- George Cotton and Sons Jan 1937
- Museum Registration Number
- 1958,1006.1960
Design
- Dial and Housing
- The dial lacks a separate plate; signature details, Roman numerals, and subsidiary seconds are engraved directly into the metal dial plate and filled with black wax. The hands are blued steel. The movement is contained within a brass canister and supported by a gimbal system. This canister is housed in a mahogany box, noted as a later replacement, which features a glazed top panel and internal red velvet dust seals.
- Visible features
- • Square mahogany case with an open hinged lid and inlaid brass keyhole escutcheon • Gimballed brass canister holding the marine chronometer movement • Brass side drop handle attached to the outer wooden box • Silvered dial with Roman hour numerals and subsidiary seconds track • Red velvet dust seal running along the upper rim of the lower box section
- Construction and Movement
- This one-day marine chronometer employs a full-plate movement construction typical of large watches, secured by five turned pillars. The brass elements are finished with a dull grain. The escapement is an Earnshaw spring detent type. It features a brass escape wheel with arms recessed below the level of the teeth and rims, a large diameter discharge roller, and a straight detent with a triangular locking stone.
- Historical Context and Provenance
- Log entries for the HEICS Exeter demonstrate that Captain Henry Meriton used this chronometer, identified as No. 245, for longitude observations during voyages between 1800 and 1808. The chronometer was formerly part of the Ilbert Collection and was acquired by the British Museum in 1958 via a donation from Mr. Gilbert Edgar. A mainspring replacement recorded to George Cotton and Sons occurred in January 1937.
Identification
- Serial number
- No 245
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: Museum curators note the mahogany box is a later replacement
- Research required: Mainspring is not original, signed by George Cotton and Sons and dated January 1937