Originally used to warn and guide ships, lighthouses are found on sandy shoals on land, entrances to bays and harbors and rocky ocean cliffs. Today, NOAA Nautical Charts, the Global Positioning System and other lighted navigational aids have mostly replaced them. But, they still serve a very important purpose, especially in remote areas where the water can be dangerously choppy.
The first lighthouses were simple wooden structures with a fire burning on the top to create a bright light. Later, whale oil and kerosene were used to light the lamp, and then electricity and carbide (acetylene gas) became popular at the turn of the 20th century. Many lighthouses used a Fresnel lens, which allowed the beam to be focused more precisely.
Modern lights use unique reflectors or Racon transponders to give them a specific light characteristic that distinguishes them from other lights in the area. Some have sectors of a particular color formed by colored panes in the lantern to identify safe water areas.
If you are passing near a lighthouse, it is important to know what information is most important and to pay attention to your surroundings. Be sure to stay alert for any rocks or other hazards in the area. Avoid distractions and be careful of the wind and current. Also, make sure to scan your charts and read the tide tables, depths and currents for that area before entering or exiting a channel. And, of course, keep an eye out for that famous light!