The ship's binnacle houses the compass. It is made of non-magnetic copper. Cast iron balls mounted on each side are adjusted to counteract the ship's magnetic field. The compass does not point to true north but to the North Magnetic Pole. It must be corrected for "deviation" resulting from the ship's magnetism and "variation" because the North Pole and the North Magnetic Pole do not coincide. The compass is mounted on a "gimbal" to keep it level as the ship rolls.

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