Heidi Wills, age 13, of St. Catharines, Ontario, Canada, for her question:
WHO BUILT THE FIRST LIGHTHOUSE?
Many lighthouses today are equipped with beacons that send out radio signals that can be received by shipboard direction finders. Radio beacons are valuable for long distance navigation and in foggy weather. In addition, almost all lighthouses have fog signals. In addition to lighthouses, hundreds of automatic lights are used on the world's waterways.
For as long as man has traveled on the sea, he has built lighthouses to warn anxious sailors of land or rocks.
Ancient Libyans were the first to build towers on the northern coast of Egypt to guide the sailors on the Mediterranean. They filled metal baskets with burning coal or wood and hung them from poles on top of the towers.
In about 300 B.C. on the island of Pharos near Alexandria, the Egyptians built a lighthouse that is considered one of the seven wonders of the ancient world. It guided ships into the city's harbor for over 1,000 years before being toppled by an earthquake.
Romans also built lighthouses at many of their ports. After the Romans conquered Britain, they built lighthouses at Dover and Boulogne to guide ships on both sides of the English Channel.
Today there are many famous lighthouses in all parts of the world. The Charleston Lighthouse in Charleston, S.C., is the most powerful lighthouse in the Western Hemisphere. The light from this 163 foot structure can be seen 26 miles at sea.
The Eddystone Lighthouse stands on a dangerous group of rocks in the English Channel. Its lantern is 133 feet above the water, and the tower is built of interlocking stones. This famous structure has stood since the late 1600s.
Also famous are the series of iron skeleton towers on the Florida reefs.
When people talk about great lighthouses, often they'll mention the Cape Hatteras Lighthouse in North Carolina, or the Mt. Desert Rock Lighthouse in Maine, or the Southwest Pass Light Station in Louisiana, or Batiscan Range Front Lighthouse on the St. Lawrence River, or the Race Rock Lighthouse on Long Island Sound in Connecticut, or the New Cape Henry Lighthouse in Virginia.
Most important part of every lighthouse is its light. A complicated mechanism enables a beam of light to carry far out to sea.
The lens in a lighthouse light is often shaped somewhat like a barrel. It might be eight feet high and six feet in diameter. These large lights can send a flashing light that can be seen 30 miles away. Most send flashing lights which can be seen every few seconds.
The lighthouse light is made to flash by revolving the lens around the lamp. Part of the lens is blacked out by a screen so that the light is hidden for several seconds each time it revolves. The largest lamps can also have up to 200 prisms.