In many places, where ordinary buoys cannot be used, a large sphere is set up on the end of a pole and painted red or black, according to the side on which it should be passed. This is known to seamen as a perch and ball. Often a square, boxlike affair or a cone made of iron or wooden slats is used in the same manner.
In still other localities the government does not think it worth while to establish regular buoys and local fishermen or others use channel marks in the form of kegs set on posts or rods in place of danger buoys and cedar trees fastened on tall posts to indicate the channels.
In many parts of the country beacons are used which are tripods or platforms of wood or iron on which lanterns are suspended. Sometimes the beacons are built of stone or concrete.
On navigable rivers and inland waters and in some places on the coasts range marks are used. These are square or diamond-shaped frames of boards painted white with a square or circle of black in the center and set on posts. They are placed so that when two come directly in line the boatman knows he is in the center of the channel. At night lanterns are often hung upon them.
Sometimes one sees a large spar buoy painted white and with a little black anchor painted upon it. This shows the anchorage for large vessels and indicates that vessels cannot anchor further than the buoy without obstructing a channel or endangering cables, submarine works or other things.
Just as buoys tell the sailor which way to steer in harbors or when close to shore so lightships and lighthouses show mariners how to sail along the coasts. Lightships are vessels carrying lights at their mastheads and are anchored out at sea on shoals or off harbors to show where the channels begin.
Lighthouses are usually built on shore close to the sea, but they are often built on stone, masonry or slender steel supports quite a distance from the land. Each lighthouse has a different light, many are painted in stripes or other distinctive patterns and lightships are numbered and named to enable sailors to identify them easily.
Harbor Chart Showing Lights, Buoys, Channels, Soundings, Bearings, Bottom, Etc.
Some lighthouses throw a steady red light, others a steady white light, others flashes of white, others flashes of red, others alternate flashes of red and white, and in many places they are arranged so that a white light is visible from vessels in the channels or in safe waters, while a red sector causes a red light to be thrown over the shallow or dangerous waters. Moreover, the flashing lights have various intervals between flashes and thus, by knowing the colors of the various lights and the duration of their flashes, a sailor can determine just where he is by the lighthouses he sights.