What is a Lighthouse?
A lighthouse is s building that was made to guide ships. The most important part of a lighthouse is the light that it casts at night. Almost everything else at the lighthouse is designed to help keep the light as bright and visible as possible. Sometimes lighthouses guide ships to a port or harbor. Other times they guide ships away from a hazard. Sometimes they do both. At night, lighthouses guide ships with their light. Mariners can tell what light they are seeing by its characteristic. All ships have a book, called a Light List, that tells them the characteristics of lighthouses. When a mariner sees a light, he can look it up in the Light List to see what one it is. Off the South Shore of Long Island, if mariner saw a white light flashing every seven-and-one-half seconds, he could look it up and find out that it is the Fire Island Lighthouse. He could also see in the book what lighthouse he should expect to see next, depending on which way he is traveling. During the day, lighthouses
