Charts, accurate timepieces, and instruments for calculating the noontime angle of the sun were needed to safely navigate the globe.
Swiss Pocket Chronometer, Around 1850
Developed in mid 18th-century England and France, chronometers were extremely accurate portable timepieces. They were carried aboard ships for timing star sightings, which permitted precise calculations of location. A pocket chronometer was carried on deck for the actual sighting; a larger boxed chronometer was kept protected below decks.
Gift of Dr. Thomas Featherstonhaugh
Before modern electronic navigation tools such as GPS, there were two types of navigation. The first was dead reckoning, in which a vessel’s position was estimated by observing local winds, currents, vessel speed, and direction. This worked best for coastal shipping, where sight of land could help determine location.
The more accurate celestial navigation used the positions of certain stars to calculate a ship’s precise position, using charts and an instrument to measure sun angles over the horizon. An accurate timepiece to determine exact noontime for sights also was needed, along with elaborate mathematical tables to calculate the precise position on the globe.
Norie Octant, 19th Century
John Norie sold navigating instruments in his shop. Inscribed “NORIE LONDON” and made of ebony, ivory and brass, this octant was used to take noontime sun sightings for determining a ship’s position. The instrument’s name derives from its arc enclosing one-eighth of a circle.
Gift of Edward Corcoran