- Museum number
GOLD CASED CYLINDER WATCH WITH DUMB HALF-QUARTER REPEAT.
Ruby cylinder escapement; compensation curb; originally had regulator on cap.
Enamel dial with subsidiary seconds.
Gold heart-shaped hour and minute hands; blued-steel seconds hand.
- Production date
- 1787 (case)
Circumference: 41.20 millimetres (dial)
Diameter: 37.90 millimetres (back plate)
Diameter: 51.90 millimetres (case)
Diameter: 44.50 millimetres (dial plate)
Diameter: 40.20 millimetres (front plate)
Thickness: 24.20 millimetres (case)
Thickness: 7.50 millimetres (movement)
Thickness: 24.50 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Josiah Emery, 1787
Signature: On the back plate and on the dust cover 'Josiah Emery Charing Cross London 1110'.
Case: Gold open face consular case with seven-knuckle hinge and screwed-on stirrup pendant. The maker's mark VW (see note 1, registration no. 1958,1201.806) and with the London hallmark for 1787. The dust cover has to be removed before the movement can be swung out of its case. Diam. 51.9 mm, overall h. 24.2 mm.
Dial and hands: Flat enamel dial slightly curved at the edge, with subsidiary seconds, having two short rectangular feet passing into slots in the dial plate and held by screws set in the edge of the dial plate. The edge of the dial plate engine-turned. Gold minute and hour hands, blued steel seconds hand.
Dial plate diam. 44.5 mm; front plate diam. 40.2 mm; back plate diam. 37.9 mm; frame h. 7.5 mm.
Frame: Full plate construction with five turned pillars, the back plate retained by pins. The front plate secured by three screws to the dial plate, the screws passing through the edge of the latter and into blocks standing on the front plate. The movement hinge is integral with the dial plate and the elaborate blued steel case catch and return spring are secured to it. A balance stop operating lever and spring are also fitted under the dial plate with a push-piece projecting through the edge just after the III o'clock position. The balance stop connects with a yoke-crank on the end of an arbor pivoted in the frame, and carrying the stop piece squared and pinned to its other end. The elaborate turned dust cover, probably made from a number of pieces soldered together, is fixed to the back plate by a semicircular polished steel clip engaging two pillars standing on the back plate. In addition to the signature there is an engraved regulation scale with 'Fast' and 'Slow'. All the brass parts are gilded, including the dust cover and the edge of the dial plate. The balance cock engraved and with a segmented cut-out in its foot to clear the limiting stop of the dust cover catch. This stop no longer protrudes so that the cut-out is not required.
Fusee: Key wind fusee, with winding square surrounded by a dust-excluding tube, the foot of which obscures part of the engraving on the back plate. The usual stop-work and maintaining power are fitted; the block for the stop-piece is elaborately worked. The maintaining ratchet wheel is of brass and the polished steel maintaining detent is pivoted under the great wheel, the ratchet with integral spring. The setting-up-work is fitted on the front plate under the barrel which has a narrow flange. The barrel arbor is provided with a square hole on the dial side for setting up with a male key.
Going train: Compressed into the somewhat restricted space shared with the repeating train and hammers, it was not possible, apparently, to lodge the fourth wheel in the correct place for the seconds hand. A separate pinion is driven by a third wheel, carrying the seconds hand on an extended pivot and planted between cocks on either side of the front plate. A light spring bears on the arbor of this pinion to take up the backlash in the gearing. The train count itself is chosen to give the very unusual number of beats per hour of 17,966 ⅔ of the balance and spring. The finish of the polished steel pinions and arbors is of a very high quality. The brass wheels are gilded.
Jewelling: The pivots of the escape pinion arbor and balance staff run in pierced jewels with endstones. A diamond endstone set in a polished steel ring is secured by two screws in a sink on the balance cock.
Escapement: A cylinder escapement in which the part of the cylinder acting with the escape wheel teeth is made from a semicircular piece of ruby set in a delicate steel frame carrying the lower pivot. The escape wheel is made of steel. Banking for the balance, to restrict its movement to somewhat less than a turn in either direction, is provided by a brass pin set in the top of the balance rim and two gold pegs set in the underside of the balance cock table, in the path of the pin.
Balance: Gilded brass four-armed wheel, the arms sunk below the level of the rim, and a large central boss sunk out below the level of the arms. Four gold timing screws are set in slotted holes in the rim, and two threaded gold pegs in plain tapped holes at the ends of one of the arms.
Balance spring: Blued steel helical spring of 4½ turns without terminal curves attached at its lower end to a brass collet similar to that of Emery, registration no. 1969,0303.1. The brass stud overhanging the balance also similar to that of Emery, registration no. 1958,1201.806. Both collet and stud clamp the ends of the spring without distorting it from the original radius.
Thermal compensation: A segment-shaped piece of gilded brass is screwed to the back plate next to the balance cock. It carried a movable piece with rack teeth concentric with the balance centre engaged by a pinion with a squared arbor for mean time adjustment; this once had an index mounted on it which registered against the scale on the dust cover. Carried on the rack is a brass arm, and beside it a single straight bimetallic strip which has been repaired and may not be original. The brass arm is divided in two, with a thick portion carrying a screw to move the free end of the thinner portion towards or away from the free end of the bimetallic strip. The bimetallic strip is made up of steel and brass soldered together and appears to have been difficult to make. The flux has corroded along the edge and there is a good deal of distortion. The free ends of both the bimetallic strip and the thin brass piece next to it are formed with a part pointing down to embrace the last coil of the balance spring. The whole system is a developed version of that fitted to Emery, registration no. 1958,1201.806.
Repeating work: Half/quarter dumb repeating of Stogden type, operated by pumping the pendant. This action causes a toothed rack to turn a pinion on the barrel arbor of the repeating mainspring, lodged in a barrel within the frame. All the steel parts of the repeating work are highly polished on their upper surfaces, and several on their lower surfaces as well. The edges are finely grained.
Great wheel (fusee) 60 teeth
Centre pinion 12 leaves, wheel 60 teeth, no crossings
Third pinion 8 leaves, wheel 56 teeth, 4 arms
Fourth pinion 6 leaves, wheel 55 teeth, 4 arms
Escape pinion 6 leaves, wheel 14 teeth, 4 arms
17,966 ⅔: Beats per hour
There is an additional pinion of 7 leaves driven by the third wheel and carrying the seconds hand on an extended pivot. Since the gear ratio between this pinion and the centre wheel is 60:1 it will rotate once per minute.
Great wheel 42 teeth
Second wheel 34 teeth, pinion 6 leaves
Third wheel 34 teeth, pinion 6 leaves
Fourth wheel 30 teeth, pinion 6 leaves
Fifth wheel 25 teeth, pinion 6 leaves
Fifth pinion 6 leaves
Cannon pinion 4 leaves, minute 'pinion' (a brass wheel)
32 teeth Hour wheel 32 teeth, minute wheel 48 teeth
Provenance: Ilbert Collection; purchased by Ilbert from Jauncey in 1938.
- Not on display
- Exhibition history
1992-1993 2 Oct-28 Mar, London, BM, Britain's First View of China
- Latest: 3 (2017)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.1882 (Ilbert Collection)
Previous owner/ex-collection number: P264 (Ilbert Ledger)