Molyneux, London c.1828 No.987

2 day sidereal chronometer in brass bound mahogany box

Molyneux……………

Box/Mounting

Three-tier brass-bound mahogany box measuring 172mm high, 177mm wide, and 172mm deep.

The lid has a ‘hollow-sided’ lozenge brass plate inlaid in the top, with brass butt- hinges, opening to 90° to reveal a glazed panel retained with narrow wooden beading. Inside the lid is pasted a small paper label inscribed in ink: Loses 3s / on sid.time / Gains 233s / on mean t. / per diem / about”. In the lower part of the lid is loosely screwed a long slip of card, cut from the back of a book cover, possibly intended as a means of retaining a card for recording purposes. The front of the upper half has a brass push-button lid catch with inlaid brass ‘hollow pointed star’ escutcheon, and a small rectangular, blank ivory tablet, below. The lock on the lower half has an inlaid, pointed escutcheon (now missing). The box is of fine, concealed dovetailed construction at all four corners, and the upper half has plain hinges, opening right over. The inside of the upper and lower halves of the box are lined with dark red leather, and the back of the upper half has pasted inside a paper label inscribed in ink: “Gain or Loss of 4m.+- 2ns per diem / = do [gain or loss] of 1s in (6m +- 3ns) / Ex.S.Chronr gains 236s on / M.T.Clock in 24 hours: / equivalent to 1sm 6m 6s”

The box fittings are of the standard layout. There are brass drop handles on the sides, the gimbal screws threaded into bevelled brass blocks on the outsides of the box. The narrow, quite close-fitting lacquered brass gimbal ring and bowl have the standard adjustable curved plates for adjustment. The cast brass bowl has a slightly off-centre swiveling shutter on the base, the inside of the bowl scratched: “913”. The brass gate on the bowl, for the receiving the tongue of the gimbal lock, has been moved round on the bowl, the earlier screw and steady pin holes now plugged. The tongue of the gimbal lock has been crudely filed up and has had its vertical pin-handle position moved and the pin replaced with a larger one, crudely threaded in the tongue. The upper part of the bowl sweeps out to a slightly larger diameter, threaded for the bezel. Narrow brass screwed bezel (2 turns) with a short, flat side and narrow mouldings, with thin convex glass over the dial. The winding key is a later composite key with a brass tear-drop handle, crudely lead-soldered to the shank,. The underside of the box has a green baize covering.

Dial and hands

The 95.3 mm Ø, engraved and wax-filled, silvered-brass dial with three short dial feet riveted to the plate and fixing to the pillar plate with screws. The edge of the dial then the recess in the bowl, a pin at XII and a notch in the bowl orientating it correctly. The dial has 24 arabic hour numerals and Arabic five minute figures, the seconds dial, below the centre, has arabic five-second figures with straight batons through each. The main dial is signed above the centre: “Robt. Molyneux / 44 Devonshire Street, / Queen’ Square / 987”. Blued steel spade and poker-hands with a fine, blued steel pointer seconds hand with a counter-poised tail. The back of the dial is finely curled and lacquered and, by the centre, is drilled with one round dot mark. Four small plugged holes round the periphery of the seconds dial suggest that at some earlier stage the dial had a removable seconds dial with 130 markings, to match the frequency of the seconds hand advances

Movement

Full-plate fusee movement with four pillars with flanges and fins at either end and one fin in the lower middle, screwed to the potence plate with blued steel screws. The brasswork has a fine curled damascened finish, probably dating from the 1860s.The underside of the blued steel set up ratchet wheel has one dot (a polishing points?) and there is a nick in the barrel arbor square for orientating the wheel correctly. There is a polishing point on the underside of the maintaining power detent spring and the set-up ratchet spring. The maintaining power detent has signs of having been altered somewhat in the past, the click itself appearing to have been added to the arbor at some stage. The inside of the potence plate, the train bar, and the undersides of the pillar plate, the barrel bar, the balance cock foot, the potence, the centre wheel and the great wheel, are marked with three dots. The third and fourth wheels have two dots on the turned rivet (originally three?) and the fusee bar also has two dots. The fusee cap is dot marked for the pin entry hole. The later, signed blued steel mainspring has a steel square hooking in the barrel. There is a five-wheel train including great wheel, the fusee with Harrison’s maintaining power and with a straight sided fusee pipe, fixed with a radial screw into a dimple in the arbor. The train wheels are brass with the third, fourth and escape wheels run on a bar on the pillar plate with the lower fusee pivot run on a separate bar. All train holes have been plugged and re-pitched from new, including the maintaining power detent. There is a small hole in the pillar plate directly opposite the balance centre. There is an unused dial foot hole by the fourth wheel, presumably the result of an alteration during manufacture. The arrangement of the dial fixing is odd and inconvenient, as it is impossible to get a screwdriver blade correctly over the dial foot screws to tighten them safely, the blade has to be used at a considerable angle.

Escapement, balance, spring and jewelling

Earnshaw-type spring detent escapement, the fine grey-finished foot detent with gold passing spring screwed to the side, and pink locking stone in a pipe. The detent banks against a gilt-brass banking piece, fixed alongside the detent and there is a small viewing hole directly above, for viewing the depth of engagement of the locking stone. Bright, grey-finished impulse roller with polished edge and raked, light pink impulse stone inset, and discharge roller with a light pink stone inset.

The standard, Earnshaw-type, oversprung bimetal balance, has segmental brass compensation weights mounted on the rim segments at 85° to the arms, the rim segments extending to about 100° from the arms. Brass mean time screws are fitted to the rim at the ends of the arms. The blued steel helical balance spring has terminals on both ends, the upper terminal pinned to a brass pointer stud on the balance cock. The jewelling, is all in pink stones, except for a facetted diamond in a blued steel setting in the balance cock, all otherwise mounted in brass settings. It extends to the lower pivot of the fourth wheel, and the escapement parts as mentioned.

Alterations/condition

The box is in sound and clean condition but with a number of slight knocks. The glass beneath the lid, and all its retaining beading, is now missing. The left hand hinge has its left screw-hole broken across. The leather lining inside the box is scratched and torn in one or two places, and is mostly cut away in the area of the box lock. The brass furniture in general is well patinated, with a certain amount of old (probably not original) lacquer surviving.

The dial silvering is sound and clean. It was probably re-silvered when the additional seconds circle was removed.

The movement is in generally sound clean condition, though it was found to be thick with old, solidified oil. The gilt brass escape wheel is a later replacement and the upper pivot has been somewhat crudely re-pivoted, blueing the middle part of the pinion. The position of the minute wheel has been moved out by about 2mm, presumably an original change to accommodate the 24 hour motion work. The earlier wheel probably had 13 teeth and the balance would probably have had a 130 beats/ minute frequency, necessitating a replacement balance spring. The brass movement is in fine, well preserved condition, but may have been rebuilt and refinished, along with the above alterations, in the 1860s. The movement has only been very lightly cleaned, and has been re-oiled, during inspection.


Commentary, Provenance, etc


Potence Plate Ø: 77.2

Pillar Plate Ø: 76.9

Plate distance: 15.7

Inside barrel Ø: 32.0

Arbor Ø: 10.8 steel, unsnailed.

Thickness: 0.33 - 0.26

Height: 13.4

(6 full turns output from barrel)

Set up: 14 teeth (19 teeth as found).

Signature: (?) “Novr 1861 J Brooks” (on outside of spring, 18cms from outer end)

TRAIN COUNT


Wheel / Pinion (+ext dia) Comment:

Fusee/Great: 90 / 36.0 No.of Turns: 8 ¼ (Chain 65.4cms, 195 links)

Ratchet: 30 / 16.4 Brass, 2 steel clicks

Maintaining Power: 100 / 34.2 Brass

Centre/2nd: 90/ 29.7 + 14 / 5.8 Solid wheel. Very finely finished pinion

Third: 80 / 21.6 + 12 / 4.2 5 tapered crossings “

Fourth: 80 / 19.4 + 10 / 2.9 “ “

Escape: 12 / 12.7 + 8 / 2.2 3 curved crossings. Gilt wheel. “

Balance Frequency: 14,400 vbs/ hr (120 beats per minute)

Hour: 72 / 25.0 Brass

Minute Wheel: 72 / 23.4 “

Minute Pinion: 12 / 4.6 Highly polished steel

Cannon: 18 / 6.3 “

Set up ratchet: 13 / 20 Blued steel

Impulse pallet tip Ø: 6.8

Discharge pallet tip radius: 1.1

Detent length: 26.0

Balance Ø (length of arm): 28.4 Balance Mass (incl. b/spring & stud): 7.4g

Balance spring Ø: 11.5 Material: blued steel

Turns incl. terminals: 10 (c/w down)