An anchor is a device attached to a boat or ship and cast overboard that keeps the vessel in a particular place by digging into the bottom. The word anchor comes from the Greek word meaning hook or crook. Prehistoric anchors held vessels in place simply by their great weight and bottom friction, and therefore consisted of a single, large stone or a basketful of stones. Sacks of sand also were sometimes used as were logs of wood loaded with lead. All of these primitive types are called deadweight anchors.
During ancient or Graeco-Roman times, anchors were made of iron and were given teeth or "flukes" to fasten themselves to the bottom. It is known that during Caesar's time a variety of anchor types and sizes were carried when extensive seafaring voyages were made. Each had its own particular use for certain conditions. During the Middle Ages, little or no improvements on anchors were made, and some knowledge was actually lost. Until the early 1700s, anchors were poorly made, mainly because of bad welding and poor quality iron that was brittle. By 1770, the entire anchor was made of iron, with the old wooden stock replaced by iron. The stock is the crossbar perpendicular to the anchor's shank or vertical bar.
In 1813, an Englishman named Pering introduced curved arms, and by 1852 the British Admiralty used what is recognized as the traditionally-shaped, curved anchors on all its ships. This became the classic stock anchor that we all know today and which sometimes serves as the symbol of hope. These hook-type anchors were used on all types of sea floors, but they were not very efficient since little of the anchor itself actually penetrated into the bottom soil. Also, as vessels, especially warships, became progressively larger and heavier, anchors grew proportionally, and they soon became difficult both to handle and to stow on board.
The Admiralty eventually switched from hemp to chain cable to attach its anchors and soon adopted the new stockless anchor called Trotman's or Rodger's anchor. This type had arms that could pivot and thus would dig very well into the bottom at the most effective angle when dragged. Stockless anchors eventually came to be used on most large ships, and they soon developed pivoting flukes (arrowhead-like projections on the ends of the curved arms). A great advantage of the stockless anchor was that it could be pulled up into a hole in the ship (the hawse pipe) until only its arms were protruding, and remain there always ready to be used. Other specialized anchor shapes that have become popular are the CQR or plow anchor with a single fluke; the grapnel anchor which resembles four or five fishhooks clustered together; and the mushroom anchor shaped like an upside-down mushroom. The effectiveness of an anchor depends mainly on the nature of the ocean bottom to which its attaches itself. For a mud bottom, a mushroom anchor is best; for a rocky bottom, a grapnel serves the purpose. Finally, the size of the vessel being held determines the size and type of anchor. A vessel the size of an aircraft carrier would need an anchor weighing more than 60,000 pounds (27,200 kilograms).
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