Monday, April 19, 2010

Where are lighthouses built?

Lighthouses are built mostly on or near coastal reefs and peninsulas, and at harbors and ports. Some lighthouses warn sailors of danger. Others help to guide them to a safe anchorage.

Lighthouses have been used for centuries to guide and warn sailors. The most famous ancient lighthouse was the Pharos of Alexandria, built in Egypt about 300 B.C.

Early lighthouses were just wooden towers with metal baskets of burning wood or coal hung from poles on top. Many modern lighthouses are built of cast iron or reinforced concrete. Their lights are magnified by lenses so that they can be seen from great distances. The most powerful of all lights shines from the Creac'h d'Ouessant lighthouse. This warns of treacherous rocks off northwest France.

Most lighthouses have sirens that blare out coded fog-warnings. Some emit radio signals to guide ships with radio direction finders.

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