Chronometer

Do you have a chronometer?

In the 19th century a navigator wanting to know the ship's longitude needed to know the time, which was kept on board the ship by a chronometer.

A wristwatch costs $20; a chronometer costs $20,000.

The balances of all moveable time-keepers, the chronometer excepted, are prevented from vibrating beyond the proper arc by what is called bankings. The inferior escapements are very easily banked; a pin fixed in the balance, coming in contact with one or two studs, is sufficient for that purpose. […]

The stock-in-trade of this old gentleman comprised chronometers, barometers, telescopes, compasses, charts, maps, sextants, quadrants, and specimens of every kind of instrument used in the working of a ship's course, or the keeping of a ship's reckoning, or the prosecuting of a ship's discoveries.

The sailors sail by chronometers that do not lose two or three seconds in a year, ever since [Isaac] Newton explained to Parliament that the way to improve navigation was to get good watches, and to offer public premiums for a better time-keeper than any then in use.