English Marine chronometer with power reserve Circa 1870

Brass chronometer in a mahogany box by Litherland Davies Co
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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, three part, cardanic suspension and 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, extremely rare, full plate chronometer 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, cylindrical hairspring, 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.
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John Hartnup (member of the Royal Astronomical Society) was the first director of the observatory in Liverpool (from 1844 to 1885) and developed his compensation balance with a multilayered rim. He worked with the Liverpool chronometer maker William Shepherd, who made the first copy of it. Instead of a single crossbar, as in Earnshaw’s balance wheel, three multi layer bars shaped like a “Z” are connected. The brass layer was on the top of the central rod and on the bottom of the other two rods connected by screws. The two outer bars each had a pair of multi layered edges, with brass forming the outer layer and steel forming the inner layer – like a conventional balance wheel. However, they were not arranged vertically but rather bevelled so that they were inclined at an angle of 45 degrees at an average temperature. These edges carried the balance weights and the adjusting screws. Chronometers with this balance are extremely rare. Dr Crott auctioned a Mercer chronometer with a Hartnup balance. If they even appear at auctions, these chronometers fetch enthusiast prices. The chronometer presented here was auctioned for the first time in 1995.