Who has first used the properties of showing the direction of the magnet and why ?

Explanation

A thin long piece of a magnet when suspended freely, pointed in the north-south direction.
When it was placed on a piece of cork which was then allowed to float in still water. It is shows also north-south direction.
The name lodestone (or loadstone) given to a naturally occurring ore of iron magnetite means leading stone.
The first use of magnet was made by the Chinese people to determine the direction while traveling in the sea.
Caravans crossing the Gobi desert also employed magnetic needles.
A Chinese legend narrates the tale of the victory of the emperor Huang-ti about four thousand years ago, which he owed to his craftsmen (engineers).

These engineers built a chariot on which they placed a magnetic figure with arms outstretched.
The figure swiveled around so that the finger of the statuette on it always pointed south.
With this chariot, Huang-ti.s troops were able to attack the enemy from the rear in thick fog and to defeat them.