Charlotte Rogers, age 14, of Miami, Fla., for her question:

HOW DOES A LIGHT BUOY WORK?

A buoy is a metal or wooden floating object usually anchored or moored on a dangerous rock or shoal at the entrance of a harbor, or at the edge of a channel as a guide to navigators. Mooring buoys are also used as anchorages to secure vessels in specific positions.

Especially useful is the light buoy, an important aid to navigation at night. It is battery operated and emits light signals of different colors and durations.

Another important buoy is the bell buoy, which is sounded by the action of the waves as a warning to sailors. The gong buoy, similarly operated, produces several distinctive, bell like tones. The whistle or horn buoy is fitted with a device by which air, compressed by the action of the waves, escapes through a whistle.

Each nation has a buoyage system of shapes, colors, numbers and markings to indicate dangers to navigation. In the U.S. buoyage system, red, even numbered buoys mark the starboard or right hand side of a channel when coming from seaward, and black odd numbered buoys indicate port (left hand) side. Buoys with red and black horizontal stripes mark channel junctions and isolated dangers.