Marine chronometer by John Poole, London

Dealer description — Howard Walwyn

A fine Victorian brass bound rosewood 8-day marine chronometer by John Poole, Maker to the Admiralty. The three-tier rosewood case is neatly bound in brass, with reinforced corners and a brass cartouche to the top lid. The front of the lid has a brass push-button within a twelve-point star escutcheon, the front of the base has a matching star-shaped keyhole escutcheon, and the sides are fitted with two substantial brass carrying handles. The interior is arranged to house the chronometer bowl within its gimbal ring, with the lid opening on brass hinges. The chronometer retains its brass winding key. The circular silvered dial is engraved with Roman numerals and an outer minute track, and is signed John Poole, / Maker to the Admiralty, / London , and numbered N° 1387 . There is a subsidiary power reserve dial at XII, marked WIND / UP , and a small seconds dial below the centre, numbered in tens. The dial is protected behind a glass set in the brass bowl. The chronometer retains its gilt hands. The high quality 8-day movement is housed in a brass bowl and carried in a gimbal ring within the box, arranged to maintain a level running position when in use on board ship. The brushed brass plates are joined by turned brass pillars and secured with blued steel screws, the top plate cut to reveal the train beneath. The movement is powered by a chain fusee with Harrison’s maintaining power, the grooved conical fusee with its finely cut great wheel standing beside the spring barrel. The balance is held on a lower tier beneath the balance cock, regulated by a spring detent escapement and a bimetallic compensation balance with a blued steel helical balance spring. Date: circa 1850 Height : 8 ⅜ in (21.2 cm) Width : 7 ½ in (19 cm) Depth : 7 ½ in (19 cm) *John Poole was the head of a London family firm that that was one of the leading makers of marine chronometers in the 19th century. John Poole senior (c.1791–1844) worked from Clerkenwell and, from the early 1830s, traded close to the river at Brunswick Terrace, Commercial Road. This was an advantageous position for supplying mariners and naval officers and he strengthened the firm’s standing through early submissions of their marine chronometers to the Greenwich trials. His sons entered the business: John Poole junior (1818–1867) emerged as the leading adjuster and is best known for inventing “ Poole’s auxiliary ”, a secondary compensation device applied to chronometer balances to reduce middle temperature error, James Poole (1816–1900) worked as a watch and chronometer maker (recorded in Clerkenwell/Pentonville) and remained an important part of the wider workshop output, with the Poole trade continuing in various forms into the later 19th century. HW6725