Identify the magnetic north pole of earth's magnet

As we know that magnetic field lines always originated out from the north pole of magnet and then terminate at south pole of the magnet

So here in order to find out the magnetic north pole we can say that magnetic field lines will originated out from that pole

In order to find out that part of earth from which magnetic field lines originated out we have to suspend a bar magnet freely in the air.

Now the south pole of bar magnet is always attracted towards the North pole of Earth magnetic field

So when We freely suspend the bar magnet then its south pole always shows the position of North pole of Earth magnetic field.

So we can say that the Geographic south position of Earth is the magnetic North pole of Earth

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it