English Marine chronometer with power reserve Circa 1870

Brass chronometer in a mahogany box
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A Fine English, two day marine chronometer with power reserve indication, Hartnup’s continuous auxiliary compensation balance and ratchet key, circa 1870. Three tier mahogany box with external brass handles, the glazed upper section with hinged lid (heavily restored). Brass bowl and gimballed suspension. Silvered dial with Roman numerals, outer minute track and Arabic five minute numerals, subsidiary seconds and Up and Down scale. It has blued steel pear hands.

Brass full plate movement, spotted decoration, relieved for the barrel, ring turned cylindrical pillars, fusee with chain and Harrison’s maintaining power, Earnshaw type spring detent escapement, jewelled locking stone, Hartnup’s auxiliary compensation balance, free sprung blued steel helical balance spring with terminal curves, diamond end stone. Dial signed.
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Diameter: 102 mm
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Dimensions box: 190 x 190 x 190 mm
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Signed: Litherland Davies Co. Liverpool
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The dial side of the pillar plate is stamped T & JH, who were the movement suppliers. The layout and design of the movement with the foot of the balance not inset from the edge of the plate is a typical feature of a movement made in Prescot or Lancashire. The Hartnup Balance John Hartnup, the inventor of the continuous Auxilliary compensation balance, was superintendent of the Liverpool Observatory and, during his work, would have tested many chronometers. This made him acutely aware of the middle temperature error. To solve the problem, he designed his balance in about 1847, assisted by William Shepherd, a Liverpool chronometer maker. Hartnup did not patent his balance and widely publicised it in 1849 in the June issue of Monthly Notices of the Royal Astronomical Society. Whilst the Hartnup balance works well; it was a difficult and expensive balance to produce and suffered from instability due to the parts being held together by screws.