Scheepschronometer

MARINE CHRONOMETER IN CANISTER.

The director of the Leiden Observatory, Cornelis Ekama bought this chronometer in 1817 together with a regulator. The chronometer is probably of English origin.

One of the successors of Ekama, Frederik Kaiser, ordered Hohwü sr. to make this chronometer into a 130-beater in 1850. Hohwü replaced the escape wheel so that the movement from that point beat 130 times per minute. Kaiser then used this chronometer with the seconds beater to make a 'time vernier'. Kaiser developed a method, by which the use of both timepieces could make measurements accurate to a fraction of a second. Both were started at the exact instant of an event (the device with which Kaiser accomplished this is now lost) and the number of beats after which both clocks were heard to be in step was noted (this happens every six seconds). In this way the original time could be fixed within parts of a second.

The dial has a central hour hand (I-XII) and minute hand (divided in 60 parts). The subsidiary second dial (0-120, divided in 65 parts) is below the centre and the usual up-and-down indicator is missing. The chronometer has a duration of one day.

1816
Chronometer h 5.5, ø 9
Canister h 8, w 11, d 11
Signed on dial 'Knebel, Fecit, Amsterdam. N°. 46.'
By Herman Friedrich Knebel, Amsterdam