In this duty they are similar to the lighted buoys which, in recent years, have been put to so many uses, the lightships being, however, greatly more conspicuous and generally marking a spot well outside the entrance to the channel. Buoys are of many uses and of many shapes and sizes, marking danger spots, submarine cables, sunken wrecks, channels, as well as temporary obstructions. Some are used for mooring ships in harbours, some carry bells or whistles for sounding warnings, some carry lights. Attempts have been made to standardize the shapes and markings of buoys in all countries, but many lands still maintain their own designs, and the officers of a ship visiting strange waters must acquaint themselves with the particular designs there in use. [Illustration: FIRE ISLAND LIGHTSHIP _This lightship is anchored off Fire Island, near the southern coast of Long Island, U. S. A. Lightships sometimes mark shoals, and sometimes mark the entrances to harbours. They are always kept anchored in given spots and are merely floating lighthouses, although, of course, they are sometimes relieved by other lightships so that they may undergo repairs._ ] Buoys are of scores of different sizes and designs. They may be nothing more than tall painted poles of wood anchored to the bottom in shallow water and standing more or less vertically. These are called “spar” buoys, and are useful if ice is floating in the waters that they mark, for as the ice floats against them they give way, the ice passes over them and they serenely reappear, none the worse. On the other hand buoys may be huge structures of steel many tons in weight, forty feet from top to bottom, ten feet in diameter, and complex in their equipment of lights or whistles or bells. Or they may be great barrel-like steel floats, or conical ones, or great turnip-shaped floats. Some are spherical, some are of stranger shapes. They may be red or black or green. Some are striped, with weird decorations gracing their tops. Some support small triangles or spheres, some crosses, some paint-brush-like affairs. But each one has its particular uses, and one should hesitate to pass a buoy unless the thing it stands for is understood. In United States waters, for instance, one needs to know that in coming in from sea a ship should pass with the red buoys, which are conical in shape and are called “nun” buoys, on the starboard, or right side. These buoys are further distinguished by being numbered with even numbers. At the same time all “can” buoys, which are black and cylindrical, with odd numbers painted on them, should be kept to the port or left side. Sometimes “spar” buoys replace these, but the buoys to starboard will always be red, the buoys to port black, as the ship comes in from sea.