The earliest basic magnetic compass, like many of humanity’s important technological breakthroughs, owes its development to the necessities brought on by warfare. Emperor Hoang-ti (2700 B.C.) used a magical stone hung on horse drawn wagons in pursuit of his enemies giving a tactical advantage.
Lodestone is the name given to this iron rich mineral magnetite which became magnetised by high voltage lightning strikes  orientated itself along the magnetic field lines. As a consequence of its seemingly magical property became highly prized and worth its equivalent weight in silver. The magnetic stone was either suspended by a thread or placed on a piece of floating wood (sometimes sculpted into the shape of a boat) on the surface of a bowl of water and by eliminating friction the stone naturally oriented itself along the North & South poles.
Later the Chinese found that they could magnetise an iron wire (or needle) by touching it to a lodestone. The needle would then become magnetised for a short time and could be stuck in a piece of straw or cork to float and likewise orientate North & South. To maintain the magnetism of this early compass it was necessary to frequently slide the stone along the needle, a process known as “feeding the needle.”
Sailors in Europe became aware of this crude compass via the Arabs around 1000 A.D. and began developing it for use in Maritime exploration.
However, floating a magnetized needle on a liquid surface was not easy, especially in a rolling sea, so a pivot pin was developed onto which the magnetised needle could be mounted to rotate freely. This technological innovation was followed by the introduction of a compass “card,” which later became the “compass rose” showing North, South, East & West, and subdivided into 32 points. North was traditionally indicated on the card by a fleur-de-lis, probably because of the early use of marine compasses by the seamen from the ancient Aquitaine region of France, (according to Norie & Wilson in 1889 ).
Over the ensuing 1000 years the compass as we know it today has changed very little but was used during that time to generate increasingly accurate maps that enabled a cumulative knowledge of the physical world.
The maps became a precious resource for explorers, merchants, politicians and their Navy’s. Maps represented a tool for power and expansion, without the compass may not have been possible. The compass was without doubt a key technology that shaped the world we live in today. For hundreds of years the compass and the exploration it honed has been a fascination for many artists, perhaps because of the horizon of possibilities it represents.
For Vermeer it was something of an obsession. Next I’ll look at more contemporary artists who have used the compass, maps or navigation as a means to produce artwork.
 Wasilewski, Peter; Günther Kletetschka (1999). “Lodestone: Nature’s only permanent magnet – What it is and how it gets charged”. Geophysical Research Letters. 26 (15): 2275–78. Bibcode:1999GeoRL..26.2275W. doi:10.1029/1999GL900496.