Buoy
2 of the 6 encyclopedias on this shelf carry an entry for Buoy. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
boi, in navigation, any float designed to indicate a rock, shallow, or channel. A row of buoys may be anchored along either side of a channel leading amid rocks or shallows to a harbor, in which case those of one series are painted usually of a color strongly contrasting with that of the other series. A pilot is assisted by knowing that he must steer, for instance, to the right of all red buoys and to the left of all black ones. When proceeding up stream or toward the head of a harbor or estuary, the pilot leaves flat-topped buoys on the port hand and conical-shaped buoys on the starboard hand. Spherical buoys indicate a shallow with a channel on each side. Bell buoys carry a bell rung by the heaving of the waves. Lamps and even electric lights, in a shore circuit, of course, are employed to render buoys visible at night. A life buoy is a life preserver , made usually of first crop cork covered with painted canvas. It is made in the form of a belt and is designed to surround the body below the armpits, and keep a person afloat till boats can reach him. Ships are required by law to carry life buoys accessible in case of disaster.
Collier's New Encyclopedia (1921)
any floating body employed to point out the particular situation of a ship's anchor, a shoal, the direction of a navigable channel, etc. They are made of wood, or, now, more commonly of metal. They are generally moored by chains to the bed of the channel, etc. They are of various shapes, and receive corresponding names; thus, there are the can buoy, the nun buoy, the bell buoy, the m mooring buoy, the whistling buoy, etc. The name is also given to a floating object intended to keep a person afloat till he can be taken from the water: more particularly called a life buoy.
What Has Changed in the Last Century
Aiton's 1910 rule — steer right of all red buoys, left of all black ones — has been half-superseded. Black lateral buoys were repainted green in American waters in the 1980s to match the IALA system agreed in 1980, which also divided the world into two regions: red to starboard when entering harbour in the Americas, Japan and Korea ("red right returning"), and red to port almost everywhere else, so the same buoy means opposite things depending on where you sail. The floats themselves have changed too: plastic and steel hulls with solar-powered LED lanterns and radar reflectors, moored oceanographic buoys that radio wind, wave and temperature data ashore, and "virtual" AIS marks that exist only as a radio signal on a chart plotter. Collier's life buoy of cork and painted canvas is now closed-cell foam, and under modern safety rules ships carry lifebuoys fitted with self-igniting lights and smoke floats.
Written for this edition, 2026.