THOMAS EARNSHAW, NO. 376, CIRCA 1800

Details

A GEORGE III MAHOGANY ONE-DAY MARINE CHRONOMETER
Thomas Earnshaw, No. 376, circa 1800
The silvered dial signed and numbered Thos. Earnshaw INVT ET FECIT No. 376, Roman hour numerals, blued steel tapered hour and minute hands, subsidiary seconds dial with gold hand (at VI), top-plate inscribed Thos. Earnshaw Invt et Fecit No. 376. London No. 2574, five pillar plate, one mounted within the train, three pinned, two with screws, Earnshaw's 15,600 count 'quick count' vernier escapement, viz thirteen tooth escape wheel, cut bimetallic balance with segmental heat compensation weights, blued steel helical balance spring, spring foot detent with jewelled locking stone, brass bowl with counter-weight skirt, square section gimbal, two sprung brass radial locking arms to underside of bowl, green baize-lined two tier box, the top with glazed viewing port and sliding cover thereto, external brass drop handles
73 mm. dial diam., 203 x 203 x 188 mm. box

Literature

Christopher Wood, The Function of the Quick Train Chronometer, Antiquarian Horology, No. III, Vol. IX, pp. 331-6.

Lot Essay

Earnshaw's 15,600 count 'quick train' means that instead of the seconds hand making a complete revolution of the seconds dial in 120 'half secon' steps, as is usual with a standard 14,400 count train, this chronometer takes 130 steps to complete one revolution. The purpose of this was to enable the sound of the faster beating chronometer escapement (130) to be used as a vernier to check a number of standard chronometers fitted with 'half second' beating (120) escapement.
For a full explanation of this principle see Christopher Wood F.R.A.S., op. cit.

More from Clocks

View All