A very long time ago in ancient Greece there lived a shepherd called Magnes.
One day Magnes was grazing his sheep in the hills above his house when he realized that one of his sheep had gone missing. He looked everywhere for the missing sheep but couldn’t find it. He even looked among the rocks above the pastures in which his flock had been grazing.
While he was searching he was astonished to find that his hobnail boots, with iron nails in their soles, were sticking to the rocks as he walked!
Amazed by the properties of this ‘magical’ rock he took samples back with him to his village where he showed all his friends and neighbors.
Magnes had discovered ‘lodestone’ (also called ‘magnetite’) the most ‘magnetic’ of all rocks on earth!
The ancient Greeks did not understand the science behind magnetism. They came to believe that lodestone had magical powers, could cure the sick of many illnesses and drive away evil spirits.
If ancient ships sailed too close to islands containing large amounts of lodestone they were believed to fall apart and sink as mysterious magnetic forces ripped out iron nails from wooden hulls.
A compass is a tool that tells you geographical directions (north, south, east and west) using a magnetized needle as a pointer. Between 202BC and 220AD the Chinese made the first compasses. You can see an early Chinese compass working below:
When placed on a bronze base plate the handle turns to point south.
Early Chinese sailors used these compasses in their ships to help them navigate the oceans. Unfortunately rough seas and high winds made the compasses very unreliable and they often gave inaccurate directions.
The Chinese sailors also tried another type of compass at sea; they tied a piece of lodestone onto a stick floating in an bowl of water. However this type of compass was also unreliable at sea in stormy weather conditions.
Without reliable compasses the only ways in which sailors could tell where they were heading was by navigating using the sun, the stars or familiar landmarks on shore. In gale force weather conditions neither sun nor stars would appear for days on end and sailors would lose all knowledge of where they were heading. Being shipwrecked happened all too often!
What was needed was a different type of compass- one that was reliable in all weather conditions.
The example below is a 16th century Italian compass used at sea, a so called ‘maritime’ compass. This compass has a bar magnet inside it attached to a compass rose which rotates (turns) freely in a horizontal direction until it points north.
Most early compasses were placed in wooden boxes but this sixteenth century Italian compass is inside a box made of ivory, so its original owner must have been very wealthy.
‘North’ is indicated by the symbol of a lily flower or ‘fleur de lys’.The three petals of the ‘fleur de lys’ represent religious faith, wisdom and chivalry. Chivalry means honor, kindness and courage. ‘East’ is represented by the sign of the cross, symbolising the direction of christian holy lands.
The compass rose shown below is a replica of a design printed on the Portuguese ‘Cantino’ world map made in 1502. You should be able to spot north and east!
Some additional compass roses. Which amazing design do you prefer?