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Date: |
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Description: | John Hind, London c.1793
2 day marine chronometer in mahogany box
Hind?.
Box/Mounting
Box adapted from a small, three tier mahogany chronometer box of about 1830, the whole now measuring 121mm high, 164mm wide, and 157mm deep. The box retains its original lid with glazing beneath, but the upper half is now cut down to little more than the height of the lid. The lower half has also been reduce in height by cutting of about 2 cms from the bottom and adding a shallow base (green baize-covered underneath), similar to the lid, hinged at the back, to allow access to the movement from underneath. Both lid and base have push-button catches on the front of the box, and all three sets of hinges are of the butt-type. The junction of upper and lower half has a green baize lining on the top edge of the lower half, and the lower half retains drop handles at the sides, and the original gimbal pivots with mounts, now redundant. The two holes on the right hand side for the original gimbal locking are now neatly plugged. The lock on the front of the box has a round escutcheon, the escutcheon itself, probably originally brass, now missing. The inside of the box now has a nicely turned and moulded wooden platform, which drops into a rebate in the box and supports the brass edge of the movement.
Dial and hands
The 102.5 mm � white enamel dial attached to the movement with three pinned feet (one now \missing). Three countersunk screws fix the movement onto the turned wooden platform and the edge of the enamel dial is then covered with a further gilt brass ring, screwed into the brass edge. The dial has roman hour numerals with a large seconds dial at IV o?clock having Arabic quarter minute figures. The dial is signed across the upper centre: ?JOHN HIND / LONDON / 1793?. There do not appear to be any markings or alterations evident on the back of the dial, except remains of black paper tape which appears to have spanned across the centre hole at some stage. Blued steel spade hands both have a flat, pink jewel inset into the spade. The fine, blued steel pointer seconds hand has a counter-poised tail with a similar jewel inset.
Movement
Full-plate fusee movement with four pillars, each with moulded capitals and one fin in the middle, the potence plate fixed with four blued steel screws with turned brass washers under.. The pillar plate also forms the brass edge. The general level of finish of the movement is very high with all movement parts flat-polished and lightly curled. The inside of the great wheel is scratched neatly: ?Thos. Prest Finish Janry 1794 Prest?, ?W.Watson & F.H.Phillips 1893?, with an area heavily scratched out, followed by ?..Scapement &?. The rather coarse, powerful, unfinished and unblued steel mainspring has a fixed round hooking in the barrel and is unsigned. There is a four-wheel train and a great wheel, the wheels brass with the fourth and escape wheels run on a bar on the pillar plate.
Escapement, balance, spring and jewelling
Arnold-type spring detent escapement with polished steel escape wheel and polished steel foot detent screwed directly on the potence plate, the body of the detent suspended in a slot in the plate and with brass banking screw angled alongside in the plate. The detent has a riveted-on, gold passing spring running alongside the detent blade, and with a jewelled locking stone (now broken off). The impulse roller has a radially disposed, pink impulse jewel and the discharge roller has a similar stone inset.
The Arnold-type ?Y? balance has straight, bevelled steel arms. The three bimetal rim segments, which are screwed to the ends of the arms, are of blued steel and Arnold?s ?platina? metal on the outside, with mean-time screws`at the base of the segments and with ?bevelled cylinder? compensation weights screwed on the threaded ends of the segments. There are also threaded holes next to the ends of the segments where additional\ compensation weights could be attached. The blued steel helical balance spring has terminals on both ends, the upper terminal clamped under a polished steel piece attached to an adjustable frame, itself clamped under the table of the balance cock and encircling the balance staff. There is a bevel on one vertical edge of the balance cock foot, with a fine horizontal slot and a single threaded hole, level with the middle of the balance spring. The purpose of this feature is uncertain, but may have been associated with an amplitude limiting device, now missing.
The jewelling, which is all in clear stones and mounted in brass settings (upper balance facetted diamond endstone is in a polished steel setting), extends to the whole train except the fusee (all with endstones where possible) and the escapement parts as mentioned.
Alterations/condition
The wooden box, as it survives, is in sound and clean condition. The drop handles are tarnished but are generally sound. The, escutcheon on the front and the veneer covering the upper lid catch spring are missing, as is part of the support for the movement platform. The upper half hinges were loose and the screw holes have now been filled and re-threaded. The three screws attaching the brass edge to the wooden platform are missing, as is one of the screws fixing the gilt brass ring over the dial edge.
Box c.1830; originally would probably have been octagonal.
The barrel and set-up click position have been moved slightly (about 6mm) round the movement away from the fusee, (probably during manufacture) perhaps to provide slightly more clearance for the great wheel. Two other plugged holes in the potence plate suggest the fusee stop piece and the potence screw have both also been moved, probably also during manufacture.
The movement is in generally sound clean condition, but the escapement has been badly damaged by poor repairs. The detent spring has been broken and repaired with a collar lead-soldered around it, and it has been blackened and annealed with the heating required. The steady pin on the foot is missing and the locking stone has been broken off flush with the detent. The escape wheel has been roughly repaired in two places, using lead solder, blackening the wheel and ruining the finish. The head from one screw from the jewel settings on the lower centre wheel and from third wheel has broken off. The cross pin for the set-up ratchet and one of the pillar screws `and its washer, are missing. The mainspring is quite tired, only opening to about twice the diameter of the barrel. The balance cock has had burrs raised under its foot, suggesting the balance staff has been repivoted (or a new staff fitted) at some stage. The movement was quite dry and a little dusty, and has only been very lightly cleaned during inspection.
Commentary, Provenance, etc
Arnold made. Platina bimetal. Stud for adjustments jewelling
Potence Plate �: 101.2
Pillar Plate (brass edge) �: 117.2
Plate distance: 25.3
Inside barrel �: 44.5
Arbor �: 16.0 brass, snailed.
Thickness: 0.50- 0.66
Height: 19.9
TRAIN COUNT
Wheel / Pinion (+ext dia) Comment: Crossings? Marks?Jewelled?
Fusee/Great: 80 / 48.5 No.of Turns 6 � (Chain 84cms, 165 links)
Ratchet: 32 / 26.6 Brass, 1 steel clicks
Maintaining Power: 100 / 48.0 Brass
Centre/2nd: 80 / 43.2 + 10 / 6.5 4 curved crossings. V. highly polished pinion
Third: 75 / 38.6 + 10 / 6.0 ? ?
Fourth: 80 / 28.0 + 10 / 5.7 ? ?
Escape: 15/appr19.7 + 10/appr 3.9 ? ?
Balance Frequency: 14,400 vbs/ hr (half seconds)
Hour: 42 / 27.7
Minute Wheel: 48 / 29.8
Minute Pinion: 14 / 10.2 (Highly polished steel)
Cannon: 12 / 8.4 ?
Set up ratchet: 15 / 15 Blued steel.1 dot on underside for square orientation
Impulse pallet tip �: 4.9
Discharge pallet tip radius: 2.1
Detent length: 36
Balance �: 44.3 Balance Mass (incl. b/spring): 7.2g
Balance spring �: 21.0 Material: Blued steel
Turns incl. terminals: 11 (ac/w down)
AQN: Caird, James, Sir (owner).
caption: Marine Chronometer - Overall
caption: Marine Chronometer - Movement | Publisher: | "http://collections.rmg.co.uk/" | Rights holder: | "Royal Museums Greenwich" | Subjects: | Marine chronometer chronometers | Source: | Royal Museums Greenwich | Identifier: | http://collections.rmg.co.uk/collections... | Go to resource |
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