Magnetic Compass:

The existence of the Earth's magnetic field was observed in ancient times. Certain rocks, termed as lodestones, whenever hung by strings, always orient themselves in a commonly north-south direction. Long time ago this was properly attributed to the presence of a "force" in the air. It was a little time before the reasons for this phenomena were known, though the effect was put to use by seafarers and land explorers. Nowadays, a magnetic compass can still be a precious navigation aid, used by backpackers, mariners, and others who travel far from well-known landmarks. It can work whenever more sophisticated navigational devices fail.

The geomagnetic field and the magnetic field about a compass needle interact therefore a force is applied on the little magnet inside the compass. This force works not only in horizontal plane (parallel to the Earth's surface) though vertically, too, in most positions. The vertical component is zero at the geomagnetic equator, a line running roughly the globe equidistant from both geomagnetic poles. As the geomagnetic latitude rises toward either the north or the south geomagnetic pole, the magnetic force pulls up and downward on the compass needle more and more. The level of this vertical component at any specific position is known as the inclination of the geomagnetic field at that position. You have observed this whenever you hold a compass. One end of the needle looks to insist on touching the compass face, while the other end tilts up to the glass.