Skip navigation

<
  • Joseph Manton
  • Joseph Manton 2
  • Joseph Manton 3
  • Joseph Manton 4
  • Joseph Manton 5
  • Joseph Manton 6
  • Joseph Manton 7
>

Joseph Manton (unsigned), London

Exceptional, rare 8-day vacuum chronometer, one of two known to have survived. Circa 1808

Case

Large 2-piece mahogany box with front opening door that allows release of the upper section and also access to what will have been tubes connecting the bottom valve of the gimballed assembly to an air pump (not present) used to create a (partial) vacuum.

Dial

Original silvered dial with up/down at 12, probably having originally had an identification letter, the rear scratched JM. Blued-steel hands.

Movement

Double-frame fusee movement, the main frame with 3 pillars supporting a pinned-on top plate, with Earnshaw-type spring-detent escapement having Pennington's dovetail detent assembly on a separate sub-frame. 6-turn blued-steel helical balance-spring, 2-arm compensation balance having Earnshaw-type wedge-shaped weights, with the addition of timing screws at the end of the arms and extra screws on the balance arms. The valve on the underside of the platform on top of which is a polished steel plate having six beautifully turned brass pillars supporting the stand for the movement and also holding thermometer and pressure gauges with ivory scales. The platform also supports a heavy gauge glass dome. This will have been sealed to the steel plate with mastic originally, now loose for easy access.

Box approximately 10 inches cubed (25 cm).

Joseph Manton, the famous London gunsmith took out Patent No 3085 in December 1807 for a "machine for timekeepers to act in a vacuum, so constructed that they may be wound up in vacuum when required without admitting the external air." By prior agreement with the Board of Longitude Manton was permitted to deposit one of his 'in vacuo' chronometers (most likely this machine) with the Astronomer Royal at Greenwich Observatory. In a subsequent meeting with the Board Manton, after being questioned, revealed that the maker of his chronometer was "Mr Pennington"

Manton is known to have made at least two 'in vacuo' box chronometers, the other surviving example now in the collections held at Museums Victoria in the city of Melbourne, Australia. The mechanism is the same but now has an inlaid octagonal wooden base with no provision for carrying or protecting the dome. Its dial is signed for Manton and retains its identification letter M within the seconds indication. See also the books by Gould The Marine Chronometer, 1923, and Neal & Black The Mantons, Gunmakers, 1967.

£35,000