Display 9: Compass
The magnetic compass marked a fundamental change in maritime navigation. Unlike astronomical instruments, the compass was independent of clear weather, visibility of the horizon, or the position of celestial bodies. It enabled continuous coursekeeping, even in cloudy conditions, fog, or at night.
The compass operates on magnetism. A magnetized needle or map points to the Earth's magnetic north, which can differ from true north. The first applications of the compass originated in China, probably as early as the 11th century. Via the Arab world, the instrument found its way to Europe, where it was increasingly used in navigation from the 12th and 13th centuries onward.
Initially, the compass consisted of a needle floating on water, magnetized by the leadstone. Later, the compass rose was developed, mounted on a pivot and housed in a compass box. To minimize the effects of the ship's pitch and roll, the compass was placed in a gimbal.
The compass indicated direction, but not exact position. Therefore, it was always used in conjunction with other navigation methods, such as the log for speed measurement, the lead for depth determination, and astronomical observations for determining latitude and longitude.
Despite its limitations, the compass remained an indispensable tool for sailors for centuries. Even today, alongside modern electronic systems, it remains an essential and reliable tool for maritime navigation.
9.7
Dip Needle or Dipping Needle, 1905
Maker:
Britse Admiraliteit, London
Collection:
NavigArte
A dip needle resembles a conventional compass, but instead of being held horizontally, the needle is mounted vertically. It is a magnetic instrument used primarily for scientific and polar navigation near the North and South Poles.
9.10
Magnetic Atlas, 1800
Maker:
John Churchmann, New York
Collection:
NavigArte
Compass deviation, particularly magnetic variation, differs across the globe. It was hoped that accurate maps with isogonic lines—zones of equal variation—would assist in determining longitude.
Unfortunately, magnetic variation also changes over time.
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