THE MAGNETIC COMPASS
The magnetic compass is one of the oldest of the navigator's instruments. Initially, a compass was used only to indicate north, but soon the concept of marking other directions around the rim of the bowl was thought of. The directions were given the names of the various winds, now known as North, East, South, and West; these are the cardinal directions. Next are the intercardinal directions: NE, SE, SW, and NW. Still finer subdivisions are the combination directions: NNE, ENE, ESE, etc.; and the by-points: NxE, NNExN, NNExE, etc. This system results in a complete circle divided into 32 points and there are half-points and quarter points. The point system was widely used until relatively modern times, but is now obsolete except for some minor use on sailing craft.
Because of the difficulty at sea in using a needle floating freely in an open bowl of water, the next development was that of using a pivot at the center of a dry bowl. Not for some centuries was the liquid put back in, this time in an enclosed chamber, as now is the case in modern magnetic compasses.
The magnetic compass still retains its importance, despite the invention of the gyrocompass. While the gyro is an extremely accurate instrument, it is highly complex, dependent on an electrical power supply, and subject to mechanical damage. The magnetic compass, on the other hand, is entirely self-contained, simple, comparatively rugged, and not easily damaged.
