A chronometer is an extremely accurate clock, especially one used in connection with celestial
navigation at sea (see also celestial sphere).
It differs from an ordinary clock in that it has a fusee, by means of which
the power transmission of the mainspring is regulated such that it remains
approximately uniform at all times; and a balance made of metals of different
coefficients of expansion to minimize the effects of temperature changes.
The device is maintained in gimbals to reduce
the effects of rolling and pitching. A chronometer's accuracy is checked
daily and its error noted; the daily change in error is termed the daily
|Harrison's No.4 chronometer
Chronometers are always set to Universal Time (Greenwich Mean Time). The first chronometer was invented by John Harrison (1735).
MEASUREMENT AND PUZZLES