## Pole Star

The very first sailors steered by the stars in the sky.

In the northern sky, the most useful star is the Pole Star, because it shows where North lies. First, look for the group of stars known as the Plough. The two stars that form the outer edge of the Plough point straight towards the Pole Star. The Pole Star hangs over the North Pole.

## Southern Cross

The southern sky does not have any one star that is bright enough to be easily spotted. Instead, find the Southern Cross. Imagine a line down the cross, add four and half times its length, and you’ll be looking directly over the South Pole.

## COMPASS

The invention of the compass helped explorers to fid their way much more accurately. A compass needle is pulled by the magnetic attraction of the North and South poles so that  it always settles to point in a North-South direction. Using a compass, explorers could now steel a direct path from one part of the world to another.

The Chinese discovered the magnetic compass as early as 200 B.C. At first, only fortune tellers used it. Later, people realized it was also a good way to find the direction of North and South. The needle of an Ancient Chinese compass would be magnetized, or made to point North, by being stroked against a lump of iron rock, called a lodestone.

In the 1300s, the Italians invented the compass card. It had 32 points of direction marked on it, which made it much easier for an explorer to work out his exact direction.

The compass card was balanced on the point of a needle. Magnets were attached underneath the card. These magnets caused the whole card to suing on the needle to always point North.

## HOW DID EXPLORERS STEER BY THE STARS

Explorers could tell where they were heading by studying the position of the Sun or stars. The trick was to measure how high the Sun or stars were above the horizon. One instrument for doing this was the quadrant. It was first used in Europe around the early 1200s.

A quadrant was a quarter circle made out of metal. Degrees were marked along the rounded edge. A small weight called a plumb hung straight down from the squared-off corner.

The navigator would aim the quadrant at a well-known star. He would read off the degrees where the plumb was hanging. He then worked out his latitudes.

## HOW DID SAILORS MEASURE THEIR SPEED

Sailors used a log to measure how fast their ship was going. This was a block of wood that was thrown into the water behind the ship. A line of rope attached to the log unreel as the ship moved.