The north end of the compass needle is pulled down towards Earth when you hold it in the normal horizontal position in the northern hemisphere. So much so, in fact, that the south end needs to be slightly heavier to balance it. If you bring that same compass to Australia, the south end, already weighted, will be pulled down even further, perhap even dragging on the base of the compass. So you need to reverse the weights in any compass used in the southern hemisphere.
A chart of magnetic dip contour lines along which the dip measured at the Earth's surface is equal. These are called isoclinic lines.
Magnetic inclination, or dip angle, is the angle that the Earth's magnetic field makes with the horizontal. If you hold the compass vertically in the northern hemisphere, the North Pole end should be pulled downwards.
Image Source: How Magnets Work
A dip needle is just like a conventional compass, but instead of holding it horizontally, it is held vertically. It is a magnetic needle used for navigational purposes just like a compass, but is used predominantly when traveling around the north and south poles. Instead of measuring horizontal magnetic deflection, the dip needle measures vertical magnetic inclination. When over the equator, the magnetic field of Earth is parallel to the surface of the Earth. At the poles, or near them, a conventional compass is very unreliable.