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A few pointers; Maritime Tales by Stephen Guy of Merseyside Maritime Museum.

Byline: Stephen Guy

THE origins of the compass are veiled in the mists of time and there is disagreement over the how this simple but essential device came into being. Early mariners relied on landmarks and the stars, which could be precarious and dangerous. Sea mists and fogs meant that ships had to stop or risk being wrecked - in some regions there was no winter sea travel between October and April.

As a result, seafarers usually hugged the coastline or at least kept within sight of land. There were numerous superstitions about the sea - for example, many feared that when ships reached the horizon they would plunge over the edge.

There were tales of sea monsters and strange lands where giants and unknown beasts waited for the unwary sailor and traveller.

The compass helped dispel some of these myths because it enabled ships to make safer journeys. Increasingly detailed charts were devised - invariably with BRASS: Sperry gyro-compass the magnetic north marked, as on the compass.

Many historians agree that the compass originated in China. They first used a lodestone or natural magnetised iron ore. People observed that a suspended lodestone, allowed to turn freely, would always point towards the magnetic poles.

Compasses were later made from iron needles which had been magnetised using a lodestone.

Lodestones and magnetism were first mentioned in China in about 350 BC but it was hundreds of years before there was reference to a lodestone attracting a needle (80 AD).

There is a specific mention of a magnetic direction finder - a compass - around 1040. About 1115 Zhu Yu wrote about a compass being used at sea.

Europeans were using compasses some time after this - for example there is a reference to a sea compass in 1269. In the same period the advent of compasses accompanied improved charts in the Mediterranean.

Modern compasses on display at Merseyside Maritime Museum include a brass Sperry gyro-compass and stand.

Patented in 1908, it enabled seafarers to establish more accurate direction. The master compass operates repeaters located in different parts of the ship.

The one on display was located on the bridge wing of a large Merchant Navy ship during the 1970s.

A gyro-compass works on similar principles as a gyroscope. The compass uses an electrical gyroscope and other forces to take advantage of physical laws and the Earth's rotation.

One of the main advantages of gyrocompasses over traditional magnetic compasses is that they locate the true north rather than the magnetic north - very important in navigation.

They are also unaffected by external magnetic fields such as the ship's hull, which can distort readings on a conventional compass.

. ? Buy the Maritime Tales book (pounds 3.99) at the Merseyside Maritime Museum open seven days a week, admission free, and at bookshops, newsagents and merseyshop.com.

MAPPED OUT: An early chart featuring magnetic north, depicting the coast of Africa

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MAPPED OUT: An early chart featuring magnetic north, depicting the coast of Africa
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Publication:Liverpool Echo (Liverpool, England)
Date:Apr 30, 2011
Words:493
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