Usher & Cole

Usher & Cole, Makers to the Admiralty, London, for M/Y Lady Patricia, circa 1880. Fine mahogany two-day marine chronometer with winding indicator with Poole’s auxiliary compensation. Three-body, with brass handles, the glazed upper section with hinged lid. Brass bowl and gimballed suspension. Silvered with Roman numerals, outer minute ring, subsidiary seconds and up-and-down scale. Blued steel “spade” hands. 87 mm, gilt brass full plate with baluster pillars secured by screws, 11 jewels, fusee with chain and maintaining power, spring detent escapement, two-arm bimetallic compensation balance with cylindrical weights and two mean time adjusting nuts, free sprung polished steel helical balance spring with terminal curves, diamond endstone.Signed on dial, M/Y Lady Patricia on plaque, bezel engraved “New York & Oriental Steamship Co. Ltd”Dim. Bowl 114 mm, box 19 x 18 x 18 cm. Notes The change in the rate of a timekeeper caused by the temperature acting on the bimetallic balance is approximately linear, and the same change due to the variation in the elasticity of the steel balance spring is approximately parabolic. Therefore, such combination can be compensated only in two points. In others, the difference can amount up to almost three seconds. To compensate for this, in around 1845, John Poole invented an auxiliary compensation. It works in cold temperatures and because of its simplicity became by far the most popular form of auxiliary compensation.