ARNOLD & DENT No. 896: A fine Royal Greenwich observatory two-day marine chronometer, the movement fitted with and the dial inscribed with Airy's supplementary Compensation Arm, signed on the silvered dial Arnold & Dent, 84 Strand, London No.896, Roman hour chapters, blued steel hands, subsidiary up-and-down and seconds dials, the latter with the Government Mark incised and repeated on the top-plate, Earnshaw escapement, dovetail detent with jewelled pallet to side of banking block, cut bi-metallic balance having peripheral compensation screws and fitted with Airy's Bar, oversprung with blued steel helical balance spring, in brass bowl fitted on the inside at the bottom with E.M.Johnson's Hermatic Case seal assembly to the winding hole alongside the punch-mark of a crown above the initials and number E.J.14, gimballed in plain three-tier mahogany box, circular ivory plaque to front of middle section, inscribed, Arnold & Dent, London No.896 two days and with the Government Mark, within the top lid the trade label of E.Dent & CO. 61 Strand, 4 Royal Exchange, London, and with external brass drop handlesDial; 88mm.diam.

The property of the Imperial College

ARNOLD & DENT No. 896: A fine Royal Greenwich observatory two-day marine chronometer, the movement fitted with and the dial inscribed with Airy's supplementary Compensation Arm, signed on the silvered dial Arnold & Dent, 84 Strand, London No.896, Roman hour chapters, blued steel hands, subsidiary up-and-down and seconds dials, the latter with the Government Mark incised and repeated on the top-plate, Earnshaw escapement, dovetail detent with jewelled pallet to side of banking block, cut bi-metallic balance having peripheral compensation screws and fitted with Airy's Bar, oversprung with blued steel helical balance spring, in brass bowl fitted on the inside at the bottom with E.M.Johnson's Hermatic Case seal assembly to the winding hole alongside the punch-mark of a crown above the initials and number E.J.14, gimballed in plain three-tier mahogany box, circular ivory plaque to front of middle section, inscribed, Arnold & Dent, London No.896 two days and with the Government Mark, within the top lid the trade label of E.Dent & CO. 61 Strand, 4 Royal Exchange, London, and with external brass drop handles Dial; 88mm.diam.

细节

ARNOLD & DENT No. 896: A fine Royal Greenwich observatory two-day marine chronometer, the movement fitted with and the dial inscribed with Airy's supplementary Compensation Arm, signed on the silvered dial Arnold & Dent, 84 Strand, London No.896, Roman hour chapters, blued steel hands, subsidiary up-and-down and seconds dials, the latter with the Government Mark incised and repeated on the top-plate, Earnshaw escapement, dovetail detent with jewelled pallet to side of banking block, cut bi-metallic balance having peripheral compensation screws and fitted with Airy's Bar, oversprung with blued steel helical balance spring, in brass bowl fitted on the inside at the bottom with E.M.Johnson's Hermatic Case seal assembly to the winding hole alongside the punch-mark of a crown above the initials and number E.J.14, gimballed in plain three-tier mahogany box, circular ivory plaque to front of middle section, inscribed, Arnold & Dent, London No.896 two days and with the Government Mark, within the top lid the trade label of E.Dent & CO. 61 Strand, 4 Royal Exchange, London, and with external brass drop handles
Dial; 88mm.diam.

拍品专文

This chronometer and No's. 909, 915, 924 & 994 are confirmed as being purchased in a letter, dated Jan. 6, 1837, addressed to G.B. Airy Esq, Astronomer Royal, from F. Beaufort, Hydrographer to the Navy, Copies of which are included with this lot. The letters also show that in November 1858 it was with Johnson to be fitted with his 'Hermetic Seal' and that in August to December 1877 it had a new balance with 'Airy's Comp' fitted and at the same time had a 'Stop/Start' assembly fitted. In a document with the address '84 Strand' dated Nov. 5 1840 it is recorded that No. 896 was one of 23 Admiralty chronometers which Mr Dent (who had charge of them) had left at 84 Strand 'on the dissolution of Arnold & Dents partnership', it's record of issue to H.M.Ships etc. is also included.
In 1870 The present chronometer was lent to Prof. Rucker of the Royal College of Science, now part of Imperial College.It was almost certainly one of the chronometers used by Professor Rucker in the Magnetic Survey of the British Isles for the Epoch January 1, 1886, which he carried out, together with Professor Thorpe, between 1884 and 1888. The chronometer would have been used to time the swings of a suspended magnet, one of two operations involved in using the classical Kew magnetometer for determining the horizontal componenet of the Earth's magnetic field.
No. 896 had at one time been fitted with a balance locking device operated by a separate key through the scallop plate in the bottom of the bowl. In the late 1860s Airy, the Astronomer Royal, commissioned for a system to locking the balance without the necessity of removing the movement from the bowl, the system devised by Loseby gained favour with Airy and his may have been the one fitted in No. 896.