It was during the Explorer’s Age that cartographers began using a compass rose to display orientation with regards to the map on which it was placed:
A compass rose displays the cardinal directions of North, South, East and West on a map or nautical chart. We had already come across the compass rose when we built our own map of the world:
A6 had stuck it into the corner of our map. This compass rose made it clear that, for example the Antarctic was down south, as was Australia; whilst the Arctic circle was up north, alongside Iceland and Norway.
Compass rose is also the term used to describe the graduated markings found on a traditional magnetic compass:
We would be using a compass rose for our home-made compass.
The Mariner’s Magnetic Compass
The magnetic compass was probably the most important navigational instrument the sailors had at their disposal. It is an incredibly simple tool, consisting of a magnetised needle which points to the north. Once the sailors knew where north was they were able to find other directions. The introduction of the compass rose to the design of the compass made this even easier.
The Pole star or North star, known as Polaris, had been known as the sea man’s lodestar, as it guided them through waters when they had no other equipment. It is therefore no surprise that the stone containing magnetic properties (it attracted iron), first mentioned by 6th century BC Greek philosopher Thales of Miletus, was known as Lodestone:
Lodestone is a magnetic, north finding rock capable of magnetising a compass needle. On a long exploration the sea-captain would always keep a lodestone to remagnetise their compass, which would lose its strength over time.
Making our own Compass
- L12 magnetised our needle by stroking its tip from one end of a magnet to the other 70 or so times:
- The needle was then placed next to a magnet to see if had successfully been magnetised. It had:
- The needle was taped onto a polystyrene disk:
- I photocopied a compass rose. The compass was placed on top of it and the compass rose paper was moved until its north lined up with the north on the compass:
- The polystyrene disc with the magnetised needle attached was floated on a petri dish of water and observed. The top of the needle slowly moved around until it was pointing North. We had made a compass:
In addition to a compass we also made a quadrant. But you will have to wait until tomorrow for that post. Yes, I know, you just can’t wait…..