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Compass Types
Good compasses have a fluid-filled housing; the fluid dampens the motion of the needle, so that you can use the compass without holding it perfectly still. Avoid inexpensive compasses that do not have fluid-filled housings. The compass needle is painted in two colors. Assuming that the compass is held flat, the red end points to north, and the white end to south. An interesting detail is that there are northern- and southern-hemisphere compasses. This has to do with the f act that the magnetic field lines, to which a compass needle aligns, point into the earth at the north and south magnetic poles. In the northern hemisphere the north end of the needle is pulled downwards, and the south end is counterweighted to balance t he needle. When you use a northern hemisphere compass in, say, Australia, the south end of the magnet is pulled downwards by the magnetic field, and is also heavier than the north end - resulting in a needle that catches and drags on the bottom of the compass housin g when the compass is held horizontal A good compass will last a long time. However, some things can go wrong with a compass: the plastic components can break, or the housing can develop a leak. Over time, the fluid within the housing may turn an opaque blue-green. And, very rarely, the magnetization of the compass needle may reverse, so that the south end now points to north. Baseplate or protractor compass |