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674
Edward Baker, London c.1810/1850 No.674
1 day marine chronometer in mahogany box
Baker….
Box/Mounting
Box adapted from the lower half of a three tier mahogany chronometer box without any lid, the whole now measuring 115mm high, 194mm wide, and 180mm deep. The box is lined with a solid, purple velvet-lined interior, designed to hold the chronometer bowl snugly in a padded socket, the dial with glazed bezel standing 2cms above the top edge of the box. There is a velvet covered corner socket in the back right of the box, to retain the simple brass ‘tear-drop’ winding key. The lock is still present on the lower half and has an ivory, ‘scalloped lozenge’ escutcheon, with an unsigned, circular ivory tablet, below. Seven filled holes on the front of the box suggest an earlier rectangular tablet was once present, and possibly even another, larger round one at some stage. The box still has its boxwood beading running along the centre of the top edge of the junction, originally designed to mate with a groove in the junction of the upper half which would have formed a dust seal when closed.
The box retains brass drop handles on the sides, but has all other fittings removed, only empty screw holes remaining. The hinges for the upper half have also been removed and their positions filled with slips of boxwood. On the back of the box, behind where the hinges had been, are two small brass bridge-like mounts, probably to locate the chronometer on a shelf of some kind. The underside of the box has a purple velvet covering.
The silver-plated brass bowl is of the early Earnshaw-type, with a heavy, deep weight attached to the base and with a convex glass in a nicely moulded, screwed bezel over the dial (2¼ turns).
Dial and hands
The 77.6 mm Ø, engraved and wax-filled, silver-plated dial is of the Earnshaw, one-piece type, forming the brass edge (but with the thin dial plate itself soldered to the brass edge, rather than being turned from one piece), seating directly into the bowl and attached to the movement with two screws at III and IX o’clock through the pillar plate. A single side-screw at II o’clock in the edge of the dial fixes the movement into the bowl through the threaded portion of the upper bowl. The dial has roman hour numerals with a large seconds dial at IV o’clock having Arabic ten-second figures with straight batons at alternate five-second intervals. The dial is signed across the upper centre: “Edward Baker / LONDON / No.674”. There do not appear to be any markings or alterations evident on the back of the dial. Blued steel spade and poker-hands with a fine, blued steel pointer seconds hand with a counter-poised tail.
Movement
Full-plate fusee movement with four pillars with flanges and fins at either end and one fin in the middle, the potence plate fixed with three pinned pillars and one (by the balance) with a blued steel screw. The general level of finish of the movement is reasonably high with all movement parts flat-polished. The underside of the pillar plate, of the potence plate, of the potence foot, of the balance cock foot and of the barrel bridge, are stamped with three dots, as are the great wheel, the m/p wheel and the centre, third and fourth wheels. The blued steel mainspring has a square hooking in the barrel and is unsigned. There is a four-wheel train and a great wheel, the wheels brass with the third, fourth and escape wheels run on a bar on the pillar plate. All train holes have been plugged and re-pitched from new, and viewing holes have been drilled (possibly later) at the lower 3rd/4th and 4th/esc pitchings.
Escapement, balance, spring and jewelling
Earnshaw-type spring detent escapement with grey-finished, foot detent screwed directly on the potence plate and with brass banking piece alongside. The detent has a screwed-on, steel passing spring running alongside the detent blade, and with a clear jewelled locking stone. The impulse roller has a raked, clear impulse jewel and the discharge roller has a similar stone inset.
The Earnshaw-type, two-arm bimetal balance has slightly tapered, steel arms. The rim segments, which are blued up to the junction with the arms, extend to just over 90° from the arms and have Earnshaw-type wedge weights at the ends. Steel meantime screws are attached at the end of the arms, each with thick brass washer under. The blued steel helical balance spring has terminals on both ends, the upper terminal with a fixed brass stud with two steadies, and without any side adjustment for fine isochronal adjustments. The jewelling, which is all light pink and mounted in brass settings (upper balance diamond endstone is in a blued steel setting), extends to the balance and escape wheel with endstones, and the escapement parts as mentioned.
Alterations/condition
The wooden box, as it survives, is in sound and clean condition. The beading on the top edge has `been deliberately removed for part of the back area, and a part of the front left corner has been broken off. The drop handles are tarnished but are generally sound. The silver-plating of the bowl is now rather tarnished and patchy.
The side screw in the edge of the dial has broken off flush with the edge of the dial.
The movement is in generally sound clean condition. The detent foot has lost its steady pin. The balance spring may be a later replacement. The mainspring is badly distorted, having been pulled out of the barrel in the past, and is evidently a later replacement, having been roughly ground down one edge to the correct height. Both the train bar and the balance cock have had burrs raised under their feet, suggesting the escape wheel and the balance have both been repivoted or had a new staff at some stage.
20 teeth on set up, as found (16 as left). The movement was quite dry and a little dusty.The lower fourth pivot hole has been punched round to reduce the wear, but is still quite worn. The movement has only been very lightly cleaned, and has been re-oiled, during inspection.
Commentary, Provenance, etc
Poss earnshaw renamed? Hunting on great/centre
Potence Plate Ø: 61.7
Pillar Plate Ø: 62.7
Plate distance: 12.0
Inside barrel Ø: 26.6
Arbor Ø: 8.7 steel, snailed.
Thickness: 0.26 (untapered)
Height: 10.7
TRAIN COUNT
Wheel / Pinion (+ext dia) Comment: Crossings? Marks?Jewelled?
Fusee/Great: 63 / 32.0 No.of Turns:7 (Chain 51cms, 150 links)
Ratchet: 37 / 15.6 Brass, 2 steel clicks
Maintaining Power: 120 / 30 Brass
Centre/2nd: 75 / 26.3 + 14 / 7.4 Wheel solid
Third: 64 / 20.7 + 10 / 3.7 4 curved crossings
Fourth: 70 / 18.0 + 9 / 2.9 “
Escape: 13 / appr.11.5 + 7 / appr.2 3 curved crossings
Balance Frequency: 15,600 vbs/hr (13 beats in 6 secs)
Hour: 60 / 16.0
Minute Wheel: 64 / 16.85
Minute Pinion: 20 / 5.55 (Highly polished steel)
Cannon: 16 / 4.5 (Steel)
Set up ratchet: 20 / 12.2 Blued steel.1 dot on underside for square orientation
Impulse pallet tip Ø: 5.4
Discharge pallet tip radius: 1.25
Detent length: 21
Balance Ø: 26.8 Balance Mass (incl. b/spring & stud): 6.5g
Balance spring Ø: 12.6 Material: Blued steel
Turns incl. terminals: 8 ½ (c/w down)
1 day marine chronometer in mahogany box
Baker….
Box/Mounting
Box adapted from the lower half of a three tier mahogany chronometer box without any lid, the whole now measuring 115mm high, 194mm wide, and 180mm deep. The box is lined with a solid, purple velvet-lined interior, designed to hold the chronometer bowl snugly in a padded socket, the dial with glazed bezel standing 2cms above the top edge of the box. There is a velvet covered corner socket in the back right of the box, to retain the simple brass ‘tear-drop’ winding key. The lock is still present on the lower half and has an ivory, ‘scalloped lozenge’ escutcheon, with an unsigned, circular ivory tablet, below. Seven filled holes on the front of the box suggest an earlier rectangular tablet was once present, and possibly even another, larger round one at some stage. The box still has its boxwood beading running along the centre of the top edge of the junction, originally designed to mate with a groove in the junction of the upper half which would have formed a dust seal when closed.
The box retains brass drop handles on the sides, but has all other fittings removed, only empty screw holes remaining. The hinges for the upper half have also been removed and their positions filled with slips of boxwood. On the back of the box, behind where the hinges had been, are two small brass bridge-like mounts, probably to locate the chronometer on a shelf of some kind. The underside of the box has a purple velvet covering.
The silver-plated brass bowl is of the early Earnshaw-type, with a heavy, deep weight attached to the base and with a convex glass in a nicely moulded, screwed bezel over the dial (2¼ turns).
Dial and hands
The 77.6 mm Ø, engraved and wax-filled, silver-plated dial is of the Earnshaw, one-piece type, forming the brass edge (but with the thin dial plate itself soldered to the brass edge, rather than being turned from one piece), seating directly into the bowl and attached to the movement with two screws at III and IX o’clock through the pillar plate. A single side-screw at II o’clock in the edge of the dial fixes the movement into the bowl through the threaded portion of the upper bowl. The dial has roman hour numerals with a large seconds dial at IV o’clock having Arabic ten-second figures with straight batons at alternate five-second intervals. The dial is signed across the upper centre: “Edward Baker / LONDON / No.674”. There do not appear to be any markings or alterations evident on the back of the dial. Blued steel spade and poker-hands with a fine, blued steel pointer seconds hand with a counter-poised tail.
Movement
Full-plate fusee movement with four pillars with flanges and fins at either end and one fin in the middle, the potence plate fixed with three pinned pillars and one (by the balance) with a blued steel screw. The general level of finish of the movement is reasonably high with all movement parts flat-polished. The underside of the pillar plate, of the potence plate, of the potence foot, of the balance cock foot and of the barrel bridge, are stamped with three dots, as are the great wheel, the m/p wheel and the centre, third and fourth wheels. The blued steel mainspring has a square hooking in the barrel and is unsigned. There is a four-wheel train and a great wheel, the wheels brass with the third, fourth and escape wheels run on a bar on the pillar plate. All train holes have been plugged and re-pitched from new, and viewing holes have been drilled (possibly later) at the lower 3rd/4th and 4th/esc pitchings.
Escapement, balance, spring and jewelling
Earnshaw-type spring detent escapement with grey-finished, foot detent screwed directly on the potence plate and with brass banking piece alongside. The detent has a screwed-on, steel passing spring running alongside the detent blade, and with a clear jewelled locking stone. The impulse roller has a raked, clear impulse jewel and the discharge roller has a similar stone inset.
The Earnshaw-type, two-arm bimetal balance has slightly tapered, steel arms. The rim segments, which are blued up to the junction with the arms, extend to just over 90° from the arms and have Earnshaw-type wedge weights at the ends. Steel meantime screws are attached at the end of the arms, each with thick brass washer under. The blued steel helical balance spring has terminals on both ends, the upper terminal with a fixed brass stud with two steadies, and without any side adjustment for fine isochronal adjustments. The jewelling, which is all light pink and mounted in brass settings (upper balance diamond endstone is in a blued steel setting), extends to the balance and escape wheel with endstones, and the escapement parts as mentioned.
Alterations/condition
The wooden box, as it survives, is in sound and clean condition. The beading on the top edge has `been deliberately removed for part of the back area, and a part of the front left corner has been broken off. The drop handles are tarnished but are generally sound. The silver-plating of the bowl is now rather tarnished and patchy.
The side screw in the edge of the dial has broken off flush with the edge of the dial.
The movement is in generally sound clean condition. The detent foot has lost its steady pin. The balance spring may be a later replacement. The mainspring is badly distorted, having been pulled out of the barrel in the past, and is evidently a later replacement, having been roughly ground down one edge to the correct height. Both the train bar and the balance cock have had burrs raised under their feet, suggesting the escape wheel and the balance have both been repivoted or had a new staff at some stage.
20 teeth on set up, as found (16 as left). The movement was quite dry and a little dusty.The lower fourth pivot hole has been punched round to reduce the wear, but is still quite worn. The movement has only been very lightly cleaned, and has been re-oiled, during inspection.
Commentary, Provenance, etc
Poss earnshaw renamed? Hunting on great/centre
Potence Plate Ø: 61.7
Pillar Plate Ø: 62.7
Plate distance: 12.0
Inside barrel Ø: 26.6
Arbor Ø: 8.7 steel, snailed.
Thickness: 0.26 (untapered)
Height: 10.7
TRAIN COUNT
Wheel / Pinion (+ext dia) Comment: Crossings? Marks?Jewelled?
Fusee/Great: 63 / 32.0 No.of Turns:7 (Chain 51cms, 150 links)
Ratchet: 37 / 15.6 Brass, 2 steel clicks
Maintaining Power: 120 / 30 Brass
Centre/2nd: 75 / 26.3 + 14 / 7.4 Wheel solid
Third: 64 / 20.7 + 10 / 3.7 4 curved crossings
Fourth: 70 / 18.0 + 9 / 2.9 “
Escape: 13 / appr.11.5 + 7 / appr.2 3 curved crossings
Balance Frequency: 15,600 vbs/hr (13 beats in 6 secs)
Hour: 60 / 16.0
Minute Wheel: 64 / 16.85
Minute Pinion: 20 / 5.55 (Highly polished steel)
Cannon: 16 / 4.5 (Steel)
Set up ratchet: 20 / 12.2 Blued steel.1 dot on underside for square orientation
Impulse pallet tip Ø: 5.4
Discharge pallet tip radius: 1.25
Detent length: 21
Balance Ø: 26.8 Balance Mass (incl. b/spring & stud): 6.5g
Balance spring Ø: 12.6 Material: Blued steel
Turns incl. terminals: 8 ½ (c/w down)
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Object Details
| ID: | ZAA0060 |
|---|---|
| Collection: | Timekeeping |
| Type: | Marine chronometer |
| Display location: | Not on display |
| Creator: | Baker, Edward |
| Date made: | ca.1820 |
| Credit: | National Maritime Museum, Greenwich, London |
| Measurements: | Overall: 115 x 190 x 185 mm |
| Parts: | 674 |