What Is A Barnacle

The barnacle is a small sea animal with a shell

. It attaches itself to ships' bottoms and to underwater timbers and rocks along sea shores. Whales and giant sea turtles sometimes have barnacles on parts of their bodies. There are two kinds of barnacles. One is called the acorn barnacle, the other the goose, or ship, barnacle. The acorn barnacle is two to three inches long and has a cone-shaped shell resembling an acorn. The goose barnacle is one to two inches long and has a strong leathery stalk by which it attaches itself to the bottom of a ship.

On one side of its shell it has six pairs of feathery legs, with which it pushes water carrying bits of food into its mouth. The stalk has such a powerful suction grip on whatever it attaches itself to that it can be loosened only by killing the barnacle. Barnacles are a very serious problem for the owners of ships. After a ship has been in sea water for three or four years, barnacles may become so thick on the bottom that they can slow the ship's speed by as much as four or five miles per hour. Instead of having a smooth bottom that will glide easily through the water, a ship with barnacles looks as if it had a rough coat on its underside made of thousands of small, sharp stones. Since the water cannot flow smoothly past this rough coat the ship's speed is slowed and more fuel must be used in the engines.

To get rid of the barnacles, a ship is taken into a drydock, which is a huge concrete basin filled with water. The water in the basin is pumped out and the ship settles down into a huge "cradle" with steel arms that hold it in place. Then the barnacles are hacked off with sharp steel tools. All this is very expensive. Certain kinds of paint that contain powdered copper are used on ships' bottoms. This paint is a poison to barnacles, and prevents them from attaching themselves to the ship's bottom.

by: David Bunch

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