Turn the compass around its vertical axis. Note that the pointer (the magnetic needle) keeps indicating the same direction.
How it works
The metal compass needle always points in the same direction because of the earth’s magnetic field. As opposed to a regular compass, this one is additionally equipped with a viewer.
The earth’s magnetic poles and its geographical poles do not overlap. Moreover, the magnetic poles also change their position over time. Therefore, the direction indicated by a magnetic needle may be at an angle to the geographical meridian.