compass

As early as 2500 BC, the Chinese were using pieces of magnetic rock, magnetite, as simple compasses. By the 12th century, European navigators were using compasses consisting of a needle-shaped magnet floating in a bowl of water.

Any instrument for finding direction. The most commonly used is a magnetic compass, consisting of a thin piece of magnetic material with the north-seeking pole indicated, free to rotate on a pivot and mounted on a compass card on which the points of the compass are marked. When the compass is properly adjusted and used, the north-seeking pole will point to the magnetic north, from which true north can be found from tables of magnetic corrections.

Compasses not dependent on the magnet are gyrocompasses, dependent on the gyroscope, and radiocompasses, dependent on the use of radio. These are unaffected by the presence of iron and by magnetic anomalies of the Earth's magnetic field, and are widely used in ships and aircraft. See navigation.

A compass (or pair of compasses) is also an instrument used for drawing circles or taking measurements, consisting of a pair of pointed legs connected by a central pivot.

compass

In music, the range of notes covered by a voice or instrument.