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Ship is one of the oldest and most important means of transportation. Every day, thousands of ships cross the oceans, sail along seacoasts, and travel on inland waterways. Trade among countries depends heavily on ships. For example, ships carry wheat from Canada to Germany and machinery from Germany to Chile. They haul copper from Chile to Japan and Japanese automobiles to the United States. Ships transport American corn to Ethiopia, coffee from Ethiopia to France, and French plastics to Canada.

Many kinds of ships are used to carry the world's trade. Giant tankers haul petroleum, soybean oil, wines, and other liquids. Refrigerator ships carry fresh fruits, meats, and vegetables. Vessels called dry bulk carriers haul such cargoes as grain, ore, and sand. General cargo ships transport everything from airplane engines to zippers. Passenger liners carry travelers across the oceans and vacationers on cruises to the Mediterranean and Caribbean seas and other scenic areas.

For several thousand years, people have gone down to the sea in ships. They have been drawn by the mysteries of the sea and by its promise of adventure. More important, people have sailed the seas to explore, to settle, to trade, and to conquer. In 1492, Christopher Columbus braved the unknown waters of the Atlantic Ocean in three small sailing ships and reached the New World. During the 1500's, Spanish ships carried conquistadors (conquerors) to Latin America. The conquistadors soon won control of much of the region for Spain. An old trading ship called the Mayflower brought the first Pilgrim settlers to North America in 1620. From the 1600's to the 1800's, big sailing ships called East Indiamen carried silks, spices, and other riches from the Far East to Europe. During the mid-1800's, steam-powered ships began to replace sailing vessels. The world quickly became smaller as steamships crossed the seas in a fraction of the time that sailing ships needed. Thus, ships have brought countries and peoples closer and made them dependent economically on one another.

Throughout history, nations have become rich and powerful by controlling the seas in war and peace. When countries have lost that control, they have declined. Today, ships are as important as ever to a country's prosperity and strength. The United States, the world's leading trading nation, depends largely on ships for its imports and exports. The economies of Germany, Japan, the United Kingdom, and many other countries would soon be badly crippled if there were no ships to bring in food and raw materials and to carry out manufactured goods. All the great trading nations try to have a large merchant marine. A merchant marine consists of the commercial, or merchant, ships of a country.

The difference between a ship and a boat is chiefly a matter of size. Large oceangoing vessels are called ships. All other craft are called boats.

History

The first "ship" was probably a log that was used to cross a lake or river. People probably used their hands as paddles. Later, people learned to build rafts by lashing logs together. In time, they discovered how to make dugouts and bark canoes. In regions where wood was scarce, early people made boats of other materials. For example, they sewed animal skins into a bag, which they then inflated and used as a float. Several floats tied together could support a raft. In some areas, the people found that little clay pots tied together could hold up a raft. They also learned that a large pot made a boat for one person.

In ancient Egypt and certain other regions, the people made their first rafts of bundles of reeds. In time, the Egyptians learned to lash bundles of reeds together to make boats that had a spoonlike shape. By about 4000 B.C., they had learned to build long, narrow boats powered by a row of oarsmen. During the next 1,000 years, the Egyptians made two more great advances in the development of ships. By about 3000 B.C., they had discovered that sails could harness the power of the wind and propel their boats. In addition, the Egyptians had learned to build boats out of planks of wood. After people knew how to make plank boats, they could even build ships—vessels that are big enough to cross the oceans.

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The age of sailing ships

The basic pattern for ships became set with the invention of the sail and then of the vessel built of planks. For about the next 5,000 years, shipbuilders concentrated on designing bigger and bigger ships and on improving the rig—the sails with their masts and ropes. Shipbuilders of ancient times succeeded in building ever-larger ships, but they made little progress with the rig. Big improvements in the rig began during the 1400's and reached a high point with the development of the great sailing ships of the mid-1800's.

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Egyptian ships. The ancient Egyptians designed many kinds of vessels, including small, graceful canoes, beautiful yachts, and heavy freighters. Their most outstanding achievement was probably the huge barges that carried enormous stone pillars called obelisks from quarries up the Nile River. The biggest barges measured more than 200 feet (61 meters) long and carried 750 tons (680 metric tons) of cargo.

One sail and a line of oarsmen on each side propelled the yachts and other light Egyptian vessels. The heavier craft were driven by only a sail. The Egyptians used a rectangular sail, which is called a square sail. At first, they made the sail tall and narrow. But after 2000 B.C., they made it much wider than it was tall. The Egyptians steered their ships with large oars on each side near the stern.

The Egyptians built their vessels chiefly for use on the Nile. As a result, they made all their craft—even ships used on the sea—rather light. Today, boats of planks are built by first making a skeleton of keel (backbone) and ribs and then fastening the planks of the hull to the ribs. But the Egyptians built their river craft without a keel or ribs. They simply fitted the planks together by means of joints to form the hull. These vessels were sturdy enough to sail on the Nile, but they were too weak for the rougher Mediterranean Sea.

The Egyptian seagoing ships probably had some kind of keel and a few ribs. But the bow and stern of these ships tended to droop, especially in rough seas. So the Egyptians wound a heavy rope around the bow, stretched it tightly across the deck, and looped it around the stern. The rope strengthened the vessels and kept the bow and stern from sagging. The Egyptians sailed chiefly on the Red Sea and along the eastern shore of the Mediterranean.

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Minoan and Mycenaean ships. The Minoans, who lived on the island of Crete, became the first true seafaring people of the Mediterranean region. As early as 2500 B.C., their ships ranged the eastern Mediterranean and as far west as the island of Sicily. About 1450 B.C., the Mycenaeans, who lived on what is now the Greek mainland, won control of the sea. The Minoans and Mycenaeans both helped develop the seagoing sailing ship. However, historians know little about their ships. All they know for sure is that these peoples built cargo vessels that were sturdy and roomy and had one square sail. The Minoans and Mycenaeans also built strong war galleys—long, narrow ships that were propelled by a row of oarsmen on each side.

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Phoenician and Greek ships. Scholars know much more about the ships used on the Mediterranean Sea after about 1200 B.C. At that time, the leading seafaring peoples were the Phoenicians, who lived along the eastern shore of the Mediterranean, and the Greeks.

The Phoenicians and Greeks built broad, roomy cargo ships and greatly improved the ship rig. By about 500 B.C., they built vessels with two masts. The second mast sloped forward over the bow. It supported a small square sail that made steering easier. After 300 B.C., the Greeks set a triangular sail above the mainsail. On their biggest ships, they added another square sail near the stern. This simple four-sail rig was the most advanced rig ever developed by the peoples of ancient times. As a result, ancient ships were slow and could travel at an average speed of only about 5 knots with the wind. The standard Greek freighter measured about 100 feet (30 meters) long and could carry 100 to 200 tons (90 to 180 metric tons) of cargo.

The Phoenicians and Greeks used galleys for warships. Their galleys were driven by oars. After 1000 B.C., a large, sharp ram (point) was added to the prow at the water line for use in battle. By about 700 B.C., the Phoenicians built biremes, galleys with two banks (rows) of oarsmen on each side. The Greeks adopted these ships and made them lighter and faster. By about 500 B.C., the Greeks developed the trireme. It had three banks of rowers on each side.

The Greeks—and later the Romans—built the hull of their ships first, as the Egyptians had done. But they used more and tighter joints to fit the planks together. They also inserted a system of ribs to stiffen the hull. As a result, Greek and Roman ships had strong hulls.

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Roman ships. The Romans became rulers of the Mediterranean region during the 100's B.C. They used chiefly the same kinds of ships the Greeks had used.

The Romans built up the largest merchant fleet of ancient times. Their biggest cargo ships carried grain from Alexandria, Egypt, to Rome. The largest ones measured up to 180 feet (55 meters) long and 45 feet (14 meters) wide. They could haul more than 1,000 tons (910 metric tons) of cargo and as many as 1,000 passengers.

Roman cargo ships, like all freighters of ancient times, carried travelers because no ships were designed only for passengers. Travelers simply reserved space on any freighter going their way. The ships had a few cabins for important people. The other passengers lived on the open deck. These people slept under little shelters that they set up each night.

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Viking ships were the best vessels built in northern Europe between the A.D. 700's and the late 1000's. The bold Vikings sailed their famous long ships across the North Atlantic Ocean to Greenland and even to North America. They raided, traded, and colonized. As pirates, they were the terror of the seas.

We know much about the superb Viking ships because many Viking lords arranged to be buried in their boats. Scientists have found several such tombs. A well-preserved example of a Viking warship was uncovered in 1880 near Gokstad, in southeastern Norway. The Vikings built the ship about A.D. 900. It measures 78 feet (24 meters) long and 16 feet 9 inches (5.1 meters) wide. Like all Viking ships, the hull is clinker-built—that is, the planks overlap like siding on a house. The ship carried 16 oarsmen on each side. It had a square sail mounted on a mast probably 40 feet (12 meters) high and a steering oar near the stern. The Gokstad ship was small. Most vessels had 20 oars on each side, and some had 30. See Vikings (Shipbuilding and navigation).

In 1893, a group of Norwegians built a full-scale replica of the Gokstad ship. They sailed it across the Atlantic Ocean from Bergen, Norway, to St. John's, Newfoundland, in only 28 days in spite of bad weather.

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The cog. The power of the Vikings gradually declined. By the late 1000's, they had lost control of the northern seas. Trade then began to increase among the countries of northern Europe. Merchants needed roomier vessels to carry larger shipments. By about 1200, shipbuilders in the north had developed a sturdy ship called the cog. It became the standard merchant vessel and warship of northern Europe for about 200 years.

Cogs could stand up against the rough seas and high winds of the North Atlantic Ocean. Their deep, wide clinker-built hulls held bulky cargoes. These ships had one large square sail. They also had a high structure called a castle at the prow and the stern. The forecastle, at the prow, served as a platform from which marines could fire arrows and stones at enemy ships. The sterncastle provided a shelter for important passengers. Cogs also had a new kind of steering apparatus. Instead of steering oars along the sides near the stern, cogs had a large rudder in the middle of the stern. This rudder, introduced by about 1200, was stronger than oars.

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Lateen-rigged ships. While northern shipbuilders were developing the cog, Mediterranean shipbuilders were also making important changes in ship construction and design. The Mediterranean shipbuilders began a new way of shipbuilding that became standard. They built a skeleton of keel and ribs first and then fastened the planks of the hull to the framework. They also greatly increased the use of triangular sails called lateens. Square sails worked well with winds blowing from behind. But unlike lateen sails, they did not work well when sailing into the wind.

Galleys had always been used in the Mediterranean region as cargo and passenger ships as well as warships. But about 1300, the use of cargo and merchant galleys increased greatly. These galleys generally used their oars only when there was no wind and when entering or leaving a harbor. The rest of the time the vessels were driven by lateen sails. Most galleys had two masts, with the forward mast carrying the large sail. Some had three masts. The merchant galleys were longer and wider than the warships. The standard galley could carry about 140 tons (127 metric tons).

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The full-rigged ship. About the mid-1400's, Mediterranean shipbuilders combined the best features of the sturdy cog with those of their own lighter lateen-rigged vessels. The result was a sailing ship that became standard throughout Europe for about 300 years. The Mediterranean shipbuilders continued to build the hull by fastening the planking to a skeleton of keel and ribs. But they replaced the steering oars with a rudder in the stern. They also adopted the forecastle and sterncastle of the cog. Most important, they changed the rig to gain more power and better maneuverability—and so developed the full-rigged ship.

The basic full-rigged ship, or square-rigger, had a mainmast in the middle of the ship, a foremast in the forward part, and a mizzenmast in the back part. The mainmast and foremast each carried a big square sail and, above it, smaller square sail. The mizzenmast held a lateen sail. A pole that stuck out from the bow carried a small square sail. During the late 1400's and 1500's, such great explorers as Christopher Columbus, Vasco da Gama, Sir Francis Drake, and Ferdinand Magellan used ships rigged in this way.

The new three-masted ships were relatively small and had few comforts. Only the captain, other high-ranking officers, and guests had cabins. The rest of the crew slept on the deck or in hammocks below deck. The hammock was an American Indian invention that Columbus brought back to Europe.

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The galleon. About the mid-1500's, a type of sailing ship called the galleon appeared on the seas. Galleons were big vessels with lower forecastles than other ships and a high sterncastle that housed elaborate living quarters. The foremast and mainmast each carried two or three sails, and the mizzenmast carried one or two. On the biggest galleons, a second mizzenmast was added near the stern.

Galleons served as both warships and cargo vessels. Guns had been used aboard ships since about the mid-1300's. But the galleons carried more and heavier guns. In 1588, the English and Spanish fleets fought one of the most famous sea battles in history. Both sides used galleons. But the English galleons were faster, more maneuverable, and better armed. They helped defeat the Spanish fleet. The Spaniards had called their fleet the Invincible Armada because they thought it could not be defeated (see Spanish Armada).

Spain, Portugal, and other countries also used galleons for trading. Spain used them to bring back gold and silver from its possessions in the New World. These treasure ships became a favorite target of pirates who roved the Caribbean Sea.

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East Indiamen. For centuries, ships had served as both cargo vessels and warships. But by about the 1600's, cannons had become so heavy that ships needed specially built hulls to carry the added weight. The design of warships and unarmed cargo vessels thus became, in time, greatly different.

In the 1600's, trading companies in several European countries began to build merchant ships especially for trade with India and the Far East. These ships brought ivory, silks, spices, and other products from India, China, and the East Indies. The Portuguese controlled the trade with the Far East until about 1600, when England and the Netherlands began to compete. Then Denmark and France also moved in. East India companies in each country built their own ships, called East Indiamen. Although the Indiamen were designed as cargo carriers, they carried guns for defense against attacks by pirates and fleets of enemy countries.

The size of the East Indiamen grew steadily larger. In 1700, for example, most English Indiamen carried 400 tons (360 metric tons) of cargo. By 1800, they carried 1,200 tons (1,090 metric tons).

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Packet ships. By the early 1800's, trade between the United States and European countries had increased tremendously. Also, a great demand had developed for better transatlantic passenger service. American shipowners met the demand by offering something new in service—ships that sailed on regular schedules. Such vessels are called packet ships. Before this time, ships sailed only if they had a full load of cargo and passengers. Also, the weather generally had to be favorable. Packet ships sailed at a scheduled time, fully loaded or not and regardless of the weather. The packets also became the first merchant vessels to stress the comfort of passengers. Packet service began in 1818, between New York City and Liverpool. The Black Ball Line started the service. It was so successful that other U.S. lines, such as Red Star and Swallowtail, quickly followed.

To meet the schedules and the competition, the packet ships had to sail as fast as possible. But the ships themselves were ordinary sailing vessels that had not been designed with especially sharp lines for speed. Their speed came from their captains, who drove the ships furiously night and day in all weather. The eastward crossing took from three to four weeks. The westward crossing took longer—from five to six weeks—because the ships had to sail against the westerly winds and took a longer, more southerly route.

The first packets measured about 100 feet (30 meters) long. By the 1840's, as passenger accommodations became larger and more comfortable, ships 160 feet (49 meters) long had come into use.

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Clipper ships, the most beautiful and romantic of all sailing ships, became the queens of the seas during the mid-1800's. The clippers, with their slender hulls and many sails, were designed for speed. Their name came from the way the ships "clipped off" the miles.

The United States built the first true clippers in the 1840's. They were designed to sail from the East Coast, around the tip of South America, to China and bring back tea. The discovery of gold in California in 1848 and in Australia in 1851 hastened the clipper's development as fortune seekers and supplies were rushed to the gold fields. The ship's success led the British to build a fleet to carry tea from China and wool from Australia.

Clippers had as many as six tiers (rows) of sails to a mast. Some ships had as many as 35 sails. Driven at top speed, clippers could cut through the water at 20 knots. Many could race from New York City, around South America, to San Francisco in less than 100 days.

Donald McKay, a Canadian, became the greatest designer of clipper ships. His shipyard in East Boston, Massachusetts, turned out a number of them. McKay's first clippers measured about 200 feet (60 meters) long and could carry 1,500 tons (1,360 metric tons). He steadily increased the size of his ships. In 1853, he launched the Great Republic, which was the largest sailing ship of its time. It was about 335 feet (102 meters) long, had four masts, and could carry more than 4,500 tons (4,080 metric tons).

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Sailing ships in the 1900's. Inventors began experimenting with steam-powered boats in the late 1700's. By the early 1900's, the steamship had nearly replaced the oceangoing sailing ship. But coal-burning steamships had to depend on coaling depots, and certain trade routes—such as those along the coasts of South America—had few coaling depots. On these routes, sailing ships still had use. For many years, for example, sailing ships carried nitrate, a fertilizer, from Chile, around the tip of South America, to Europe.

The sailing ships launched during the late 1800's and early 1900's were huge vessels built more for strength than speed. They had strong, straight-sided steel hulls and wire rigging. To operate cheaply, they used small crews and, therefore, carried a minimum amount of sail. The mightiest of these ships was the Preussen, a five-masted, full-rigged German vessel built in 1902. It was the largest sailing ship ever built, measuring 433 feet (132 meters) long and 54 feet (16 meters) wide. It could carry 8,000 tons (7,300 metric tons) of cargo.

Since the early 1900's, the number of seagoing sailing ships has declined steadily. Many have rotted or rusted away at their docks. Today, most of the few remaining square-riggers serve as training ships for cadets in the navies and merchant marines of various countries.

In many developing countries, people still use sailing vessels for coastal and inland shipping and for fishing. Many centuries ago, the Chinese developed the junk, a sturdy wooden vessel that carried its sails parallel to the length of the ship. The Chinese still use junks to carry goods and passengers along coasts and on rivers. For hundreds of years, the Arabs have sailed the Red Sea in long, slim, lateen-rigged vessels called dhows. Various Indian versions of the dhow are common in the harbors of Kolkata, Mumbai, and other port cities of India. The people of New Guinea have long used a sailing vessel called a lakatoi, which consists of several dugouts lashed together. Two-masted sailing ships called schooners carry cargo along the eastern and southern shores of the Mediterranean. Schooners and single-masted sloops sail between Panama and Ecuador and along South America's west coast.

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The age of engine-powered ships

The invention and development of the steam engine revolutionized water transportation. People no longer had to depend on the muscles of rowers or the uncertain wind to propel their ships. In 1769, James Watt, a Scottish engineer, patented a steam engine that could do many kinds of work. Inventors in Europe and the United States soon tried to use it to power boats.

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The first steamboats. In 1783, the Marquis Claude de Jouffroy d'Abbans, a French nobleman, built a steamboat that made a 15-minute trip on the Saone River near Lyon. But the marquis was never able to repeat his success. In 1787, John Fitch, an American inventor, demonstrated the first workable steamboat in the United States. Its engine powered a series of paddles on each side of the boat. Fitch later developed a vessel pushed by paddles at the stern. With this boat, he started the nation's first commercial passenger and freight service during the summer of 1790. He navigated the boat on schedule up and down the Delaware River between Philadelphia, Pennsylvania, and Trenton, New Jersey. But Fitch lacked enough money to keep operating. In 1802, William Symington, a British engineer, built a steam tug that had a paddle wheel at the stern. The tug worked perfectly, but Symington also ran out of money.

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The Clermont became the first commercially successful steamboat. Robert Fulton, an American, designed and built the vessel, which was officially called The North River Steamboat of Clermont. Fulton did not try to construct an engine himself, as earlier inventors had done. Instead, he ordered one from Watt and adapted it to his boat. In 1807, the Clermont steamed 150 miles (241 kilometers) up the Hudson River from New York City to Albany in about 30 hours, including an overnight stop. After extensive rebuilding, the boat sailed in regular passenger service on the Hudson. The Clermont was long and slender—originally 142 feet (43 meters) long and 14 feet (4.3 meters) wide. It had side paddle wheels 4 feet (1.2 meters) wide and 15 feet (4.6 meters) in diameter. After the rebuilding, the Clermont was 149 feet (45.4 meters) long and 18 feet (5.5 meters) wide.

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Oceangoing steamships. Fulton's boats puffed along only on bays and rivers. In 1809, the Phoenix became the first steamboat to make an ocean voyage. John Stevens, an American engineer, built it. The Phoenix traveled along the Atlantic Coast and up the Delaware River from New York City to Philadelphia. The trip took 13 days. Under perfect conditions, sailboats could do it in 2 days. In 1819, an American vessel, the Savannah, became the first steamship to cross the Atlantic Ocean. It was actually a full-rigged sailing ship equipped with steam-powered side paddle wheels. The ship took 29 days to travel from New York City to Liverpool. During the voyage, it ran its engine 105 hours, using up its entire fuel supply of 75 tons (68 metric tons) of coal and 25 cords (91 cubic meters) of wood. In 1838, the British side-wheeler Sirius became the first ship to offer regularly scheduled service across the Atlantic under steam power alone. The trip took 18 1/2 days.

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Ships of iron. During the late 1700's, British shipbuilders had begun to construct iron vessels, partly because good wood for ships was becoming scarce in the United Kingdom. But iron ships also had many advantages over wooden ones. They were stronger, safer, more economical, and easier to repair. In addition, iron ships were lighter than wooden ships of the same size, because wooden ships required huge, heavy timbers. As a result, iron ships could hold more cargo.

The United Kingdom led the world in the development of iron seagoing ships. In 1821, it launched the Aaron Manby, probably the first all-iron steamship. The United Kingdom's most gifted naval architect of the mid-1800's was Isambard Kingdom Brunel. In 1837, he launched the Great Western, the first steamship designed especially for regular Atlantic crossings. The Great Western measured 236 feet (72 meters) long and 35 feet (11 meters) wide. Its huge side wheels drove the vessel at 9 knots. Brunel designed ever-larger ships. In 1858, he completed the Great Eastern, the most spectacular ship built to that time. It was 692 feet (211 meters) long and about 85 feet (26 meters) wide and accommodated 4,000 passengers. But the ship failed economically. It did not attract enough customers to pay the huge operating costs. The Great Eastern was used in laying four successful transatlantic telegraph cables across the ocean floor. In 1888, the ship was sold for scrap.

During the late 1800's, steel began to replace iron for ships. Steel ships were stronger and lighter than iron ones. In 1881, the Servia, a British vessel, became the first all-steel passenger liner to cross the Atlantic.

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Development of the ship propeller. In 1836, two inventors—Francis Pettit Smith of England and John Ericsson of Sweden—each patented a propeller that could drive steamboats more efficiently than paddle wheels could. The side paddles had worked well in calm waters. But in rough seas, as a ship rocked from side to side, one wheel and then the other might stick completely out of the water, wasting power. In addition, waves easily damaged the fragile wheels. A ship propeller, wholly under the water at the stern, used power more efficiently than the paddle wheels did. As the propeller bit into the water, it also pushed the ship forward much faster. In 1845, the Great Britain, designed by Brunel, became the first propeller-driven ship to travel across the Atlantic.

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Increasing power and speed. New types of engines and new sources of power were developed as ships changed from wood to steel and from paddle wheels to propellers. Until the middle to late 1800's, ships used a one-cylinder steam engine. The steam expanded in the cylinder, drove the piston a full stroke, and then passed to a condenser, where it was converted back to water. By the late 1800's, the compound steam engine, which had two cylinders, began to be used on ships. In the compound engine, steam pushed the piston in one cylinder and then passed on to a second, larger cylinder. The engine thus created much more power from the same amount of steam. The compound steam engine cut the use of coal on ships up to 50 per cent. Later, shipbuilders installed three-, four-, and five-cylinder steam engines on their ships.

In the 1890's, Charles A. Parsons, an English engineer, designed a marine steam turbine, a completely new type of marine engine. It was much more powerful and efficient than the steam engine. In 1897, Parsons installed three turbines in his vessel, the Turbinia. The turbines powered the vessel at an amazing 34¹/2 knots. Within a few years, fast luxury liners began crossing the Atlantic Ocean powered by steam turbines. One of the most famous of these liners was the British ship Mauretania, launched in 1907. It was 790 feet (241 meters) long and had a speed of 27 knots.

While Parsons was working on his steam turbine during the 1890's, Rudolf Diesel, a German mechanical engineer, was perfecting another new type of engine. It used heavy oil as fuel. His engine, now called the diesel engine, used less fuel than the turbine and required much less space on a ship. In 1910 and 1911, the first diesel-powered ships, which are called motorships, went into operation. Beginning about 1920, oil also began to replace coal as fuel for steam turbines. Today, most steamships use oil.

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Nuclear power and automation. In 1954, the United States launched the world's first nuclear-powered ship, the submarine Nautilus. It was retired in 1979. In 1959, the U.S. launched the Savannah, the first nuclear-powered merchant ship. It was retired in 1971. Germany, Japan, and the Soviet Union also built nuclear-powered merchant ships. But nuclear merchant vessels are still impractical for commercial use because of their high building and operating costs.

Ships today have become increasingly automated. On many modern vessels, for example, electronic equipment controls the flow of fuel oil and air to the furnace and of water to the boilers. Automatic navigation aids help keep ships on course. Ships have also become larger and larger, and entirely new types have been developed. The next section of this article discusses the kinds of ships used today and tells how they developed.

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Ships of today

Until the late 1940's, the queens of the sea were the great oceangoing passenger liners. France, Germany, and the United Kingdom built most of these magnificent floating hotels. The liners stressed luxury and service. In addition to the regular deck and engine room hands, an army of cabin and dining room stewards, cooks and bakers, and other service workers staffed the liners.

Beginning in the late 1940's, airplanes began to carry more and more people across the seas. Today, relatively few passenger liners sail the oceans, and the great cargo ships have become the queens of the sea. These ships emphasize efficiency and economy.

Cargo vessels have become bigger and bigger, chiefly for economic reasons. For example, shippers have found it far cheaper to transport 100,000 tons (91,000 metric tons) of oil in one huge tanker than in five smaller ones carrying 20,000 tons (18,000 metric tons) each. Also, for economic reasons, shipbuilders have designed vessels that can be loaded and unloaded in a minimum amount of time with minimum labor. In addition, more and more cargo ships are being automated so they can be run by smaller and smaller crews.

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Passenger vessels

The sailing packets that began to cross the Atlantic Ocean in the early 1800's were the first ships to stress passenger comfort. From then on, shipping companies provided better and better passenger services. As ships switched from sails to steam power during the 1800's, British companies offered the best accommodations, largely because of Brunel's excellently designed ships.

Two British firms—the Cunard Line and the White Star Line—dominated transatlantic service until about 1900. Then, Germany's North German Lloyd Line and Hamburg American Line began to offer serious competition. Later, French and Dutch lines entered the race for transatlantic passenger business. Much of this business came from transporting immigrants from the Old World to the New World. The United States took the lead in providing service across the Pacific Ocean with the founding of the Pacific Mail Steamship Company in 1848. As various shipping lines competed for passengers, ships became larger, faster, and more luxurious.

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Ocean liners. The great age of the ocean liner came in the early 1900's. It reached its height in the 1930's with the launching of three of the most luxurious ships ever built. They were the Normandie of France and the Queen Mary and Queen Elizabeth of the United Kingdom. These giants, each almost 1,000 feet (300 meters) long, crossed the Atlantic Ocean in just over four days. In 1942, a fire destroyed the Normandie as it lay in New York Harbor.

Beginning in the late 1940's, the airplane began to attract more and more transoceanic passengers. Today, jet planes fly daily between the world's great cities. They cross the sea in hours, not days, and at about half the cost of an ocean trip. Most ocean liners cannot compete with the airplane and have given up. During the 1960's, the United Kingdom sold the Queen Mary and Queen Elizabeth to American investors who planned to make tourist attractions of the ships. In 1972, fire destroyed the Queen Elizabeth as it lay at anchor in Victoria Harbour in Hong Kong. The Queen Mary became a hotel docked at Long Beach, California. In 1951, American shipbuilders launched the United States, the pride of the nation's passenger fleet. The United States had a cruising speed of 33 knots and was the fastest ocean liner afloat. But in 1969, the ship stopped operating because of a lack of passengers. Today, the United States has no major passenger liner service across the Atlantic.

The Queen Elizabeth 2, a luxury liner owned by Cunard, provided transatlantic service from 1969 to 2003. After 2003, the ship was used for world and Mediterranean cruises. The Queen Elizabeth 2 was sold in 2007. In 2008, it docked off the coast of the emirate of Dubai, where it will be transformed into a floating hotel that is expected to open in 2011. Today, the only luxury liner that provides regular transatlantic service is the Cunard ship the Queen Mary 2, which was launched in 2004. The Queen Mary 2 crosses the Atlantic during the spring, summer, and fall. In winter, the ship cruises the Mediterranean and the Caribbean.

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Other passenger vessels. Although the airplane has largely replaced the ocean liner for transoceanic travel, vessels for carrying passengers short distances over water have become increasingly important. Such short-distance vessels include car ferries, hydrofoils, and air cushion vehicles.

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Car ferries have carried automobiles, passengers, and even railroad passenger cars across harbors, lakes, rivers, and other small bodies of water for many years. Like cargo ships, ferries have become bigger and bigger. Today, the biggest ones cross such large bodies of water as the Adriatic and Baltic seas and the English Channel. The largest car ferries can hold up to 800 passengers and 360 cars. They have dining rooms, lounges, and bars. Some ferries make overnight runs and have cabins for most passengers.

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Hydrofoils provide high-speed transportation over relatively short distances. These vessels are mounted on foils (wings that skim near the surface of the water). The hull remains completely out of the water, greatly reducing the drag caused by water resistance. Hydrofoils can reach speeds greater than 80 knots. These vessels have carried passengers across New York Harbor, on the Nile River of Egypt, across the Strait of Messina in Italy, and over other bodies of water in many parts of the world.

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Air cushion vehicles also provide fast trips for short distances. Such vehicles are also called hovercraft or ground effect machines. Air cushion vehicles have a powerful horizontal fan that produces a strong, continuous thrust of air between the vehicle and the water or ground beneath it. The craft, which is driven by airplane-style propellers, rides on this cushion of air and can do almost 70 knots. Air cushion vehicles are especially popular in the United Kingdom, where they have carried passengers on the River Thames, along the coasts, and across the English Channel to France.

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Classification of cargo ships

Cargo ships, or freighters, can be divided into four groups, according to the kind of cargo they carry. These groups are (1) general cargo ships, (2) tankers, (3) dry bulk carriers, and (4) multipurpose ships. General cargo ships carry what are called "packaged" items—goods that are put in packages or that form a package in themselves. Packaged items include such products as chemicals, foods, furniture, machinery, motor vehicles, shoes, steel, textiles, and whiskey. Tankers carry petroleum or other liquid cargo. Dry bulk carriers haul coal, grain, iron ore, and similar products that can be loaded in bulk (loose) on the vessels. Multipurpose ships carry different classes of cargo—for example, liquid and general cargo—at the same time.

Cargo ships can also be divided into two types according to the service they offer shippers—liner service or tramp service. Cargo liners run on fixed schedules along certain trade routes and charge published rates. They usually transport only general cargo. Some cargo liners also carry passengers. Those that carry more than 12 passengers are called combination or passenger-cargo ships. These vessels must meet safety standards set up for passenger ships. Large shipping companies operate cargo liners. Tramp ships do not sail on regular trade routes or have regular schedules. They wander the sea lanes like taxicabs and can be hired to haul almost anything, anywhere, anytime. Small shipping companies and private individuals operate these ships.

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General cargo ships

During the early 1900's, the standard general cargo ship was a three-island ship. Its name came from three structures that stood out above the main deck like separate islands. The forecastle, which held the crew's quarters, formed one island at the bow. The bridge, from which the ship was navigated, formed the second island in the middle of the ship. The engine room was below the bridge. The poop, which held cabins for the officers and passengers, formed the third island at the stern. Hatches between the islands led to the holds beneath the deck where the cargo was stored. Each hold was a separate area with a hatch cover over it. The derricks (lifting devices) that loaded and unloaded each hold rose alongside the hatches.

In time, the three-island ships gave way to freighters with one island, either in the middle of the ship or toward the stern. The island included the bridge and living quarters, with the engine room below. The one-island ship provided room for more and bigger hatches and so made it easier to load and unload cargo. During World War II (1939-1945), shipyards in the United States built more than 3,000 one-island ships—the famous Liberty and Victory ships. Both types of ships were about the same size, but the Victory ships, powered by steam turbines, were faster. The Liberty ships had reciprocating steam engines (see Steam engine [Reciprocating steam engines]). Both ships were built according to standard plans so they could be mass-produced. They carried millions of troops and millions of tons of supplies to battlefields in every part of the world.

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Traditional cargo ships. Since World War II, the traditional general cargo ship has steadily become more advanced. Today, it has powerful, electrically driven cranes and derricks. It can be loaded at the side and stern as well as at the hatches. It has automatic engine room controls and automatic navigation equipment. Yet the traditional general cargo ship has steadily been declining in use, chiefly because of high operating costs. A typical ship may carry automobiles, sacks of flour, cases of whiskey, television sets, airplane engines, crates of chinaware, and a variety of other items. Loading and unloading such a mixture of items of varying shapes and sizes requires much time and labor and is, therefore, expensive. As a result, the number of ships designed to carry only one type of cargo—tankers and dry bulk carriers, for example—has increased. Revolutionary versions of the general cargo freighter have also been developed. They include container ships, roll-on/roll-off ships, and LASH ships.

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Container ships eliminate the individual hatches, holds, and derricks of the traditional general cargo vessel. The hull of a container ship is simply an enormous warehouse divided into cells by vertical guide rails. The cells are designed to hold cargo in prepackaged units called containers. Most containers consist of a standard-sized aluminum box that measures either 20 feet (6 meters) by 8 feet (2.4 meters) by 8 feet or 40 feet (12 meters) by 8 feet by 8 feet. A 40-foot container is about the size of a railroad car.

Manufacturers load their finished goods—anything from perfume to electronic products—into the containers, which are provided by the shipping company. They then have the containers delivered to the dock for loading onto the container ship. The ship does not need a large gang of workers spending hours to fit various items into different holds. Giant cranes pick up the containers, swing them over the ship, and then lower them one upon the other into the cells. After the hold has been loaded, additional containers are stacked on the deck.

Containerization saves shippers much money. A container ship can be loaded and unloaded in a small fraction of the time it takes for a conventional cargo vessel. Thus, labor costs are cut sharply. There is also less breakage and less danger of cargo shifting during a voyage. In addition, there is far less theft of valuable merchandise because the containers are sealed.

The largest container ships measure about 700 feet (210 meters) long. They can carry more than a thousand 20-foot (6-meter) containers that hold a total of about 12,000 tons (10,900 metric tons) of cargo. These ships can make a round trip between Europe and the United States in 21 days. Because of this fast time, each of these ships equals the cargo-carrying capacity of 17 standard World War II freighters.

Many shipping companies believe that containerization is the greatest advancement in shipping since the invention of the steamship. Containerization of cargo began about the mid-1950's. Today, major shipping companies throughout the world operate or are building fleets of container ships.

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Roll-on/roll-off ships, also known as ro-ro ships, take containers mounted on a framework of wheels like a truck trailer. These ships have a stern opening and side openings. Dockworkers drive the containers up ramps onto the ships and then, by way of inboard ramps or elevators, take them to their assigned places. Ro-ro ships also haul cars, buses, house trailers, trucks, and any other cargo that can be rolled aboard. An international partnership, the Atlantic Container Line, put the world's largest ro-ro ships into operation in 1987. The five ships are each 958 feet (292 meters) long and can do 18 knots. Each one can carry about 1,100 40-foot (12-meter) containers and about 1,000 cars and trucks.

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LASH ships are huge freighters that carry preloaded seagoing lighters (barges) stacked one upon the other. The term LASH stands for Lighter Aboard SHip. The lighters are loaded at upriver ports with any kind of cargo and then towed by tugs to the seaport. There, cranes on the carrier ship lift the barges on board. The freighter then carries the barges to a seaport across the ocean. There, the barges are lowered into the harbor and then towed upstream to their final ports.

LASH ships measure up to 875 feet (267 meters) long and 107 feet (33 meters) wide and can travel at 20 knots. They can hold from 70 to 90 barges, each of which can carry 370 tons (336 metric tons) of cargo. The first LASH ship, the Acadia Forest, began operation in 1969 between New Orleans, Louisiana, and Rotterdam, the Netherlands.

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Modernization of ports. Container ships need special port facilities. Throughout the world, ports are being built or modernized to handle these vessels. The new facilities have giant cranes and other lifting equipment because container ships have few or no derricks. In port, the ships chiefly need large open areas where their thousands of containers can be left while awaiting loading or pickup. The most advanced ports use computers to assign the loading and pickup areas.

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Tankers

Tankers were among the first ships designed to carry only one kind of cargo—petroleum. Earlier ships carried oil in barrels and then in large tanks. In 1878, Ludwig Nobel of Sweden launched a ship that was simply one great tank itself. Nobel was the brother of Alfred Nobel, founder of the famous Nobel Prizes. His tanker hauled oil from the Baku fields in southeastern Russia (now part of Azerbaijan) across the Caspian Sea.

In 1885, the first oceangoing tanker, the Gluckauf, was launched. This ship, built in the United Kingdom for a German oil company, carried petroleum from the United States to Europe. It became the model for all later tankers. Its hold space had eight big tanks, and its engine room was set in the stern to reduce the danger of fire. The vessel was 300 feet (90 meters) long and 37 feet (11 meters) wide. It carried 2,300 tons (2,090 metric tons) of oil and could travel 9 knots.

Today, large tankers, often called supertankers, can measure more than 1,500 feet (460 meters) long and 200 feet (60 meters) wide. They carry about 1.1 billion pounds (505 million kilograms) of oil and can do about 15 knots. Even larger supertankers are being planned and built. Most supertankers are used to transport oil from the Middle East to Europe and Japan.

Supertankers have various economic advantages over smaller tankers. For example, it costs much less to ship a large amount of oil in one supertanker than in many small tankers. But supertankers also have major disadvantages. Their huge size makes them difficult to navigate and increases the risk of accidents. Because of their size, supertankers require ports as deep as 100 feet (30 meters) in order to unload. If a supertanker suffers an oil spill, the pollution that results could be disastrous because of the ship's huge capacity.

Most tankers carry petroleum. But some tankers are designed to haul other kinds of liquid cargo, such as liquid natural gas (see Tanker [Liquefied natural gas carriers]). Ships called ore/bulk/oil carriers (OBO's) can serve as either tankers or dry bulk carriers. These ships are discussed in the following section of this article.

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Dry bulk carriers

Dry bulk carriers transport fertilizer, grain, ore, powdered detergents, salt, sugar, wood chips, or any other cargo that can be piled loose into a hold. The first modern bulk carriers included the specially designed boats that began hauling iron ore on the Great Lakes during the late 1800's. Like tankers, these vessels were designed to carry only one kind of cargo. But unlike tankers, the ore carriers hauled solid cargo. As a result, they required more complicated loading and unloading arrangements than tankers, which needed little more than hose connections and pumps.

The Great Lakes ore carrier resembled a long steel box. It had a forecastle to accommodate the crew and bridge at the bow, and a poop to house the engines at the stern. Between the forecastle and the poop, there was a long bin to hold iron ore. Modern Great Lakes freighters have the same basic design, but they are larger than the earlier carriers. The largest vessels today are more than 700 feet (210 meters) long and carry up to 25,000 tons (22,700 metric tons).

Oceangoing bulk carriers have also grown larger and larger. The biggest ones can carry more than 100,000 tons (91,000 metric tons) of cargo. A modern seagoing bulk carrier has the bridge and engine room near the stern. The rest of the ship is a level area of deck with a line of hatches. Motor-driven equipment on board quickly removes the enormous hatch covers.

During the late 1950's, shipbuilders began to design vessels that could haul either ore or oil. These ships are called ore/oil carriers. During the 1960's, OBO carriers appeared. An OBO ship can haul ore; bulk cargo, such as grain or fertilizer; or oil. Some OBO's do not carry ore. The largest ore/oil ship can haul about 250,000 tons (225 metric tons) of cargo. The largest OBO vessels can carry about 150,000 tons (135,000 metric tons).

Barges are somewhat like small bulk carriers. These boxlike vessels haul such cargoes as cement, coal, grain, gravel, and sand across harbors, on canals and rivers, and along coasts. Before the invention of power-driven machinery, sails propelled most canal and river barges. In areas where the wind was unreliable, people or animals trudged along the bank of a canal or river and pulled the barges. In Egypt, India, and some other countries, barges are still towed in this way. Modern barges have diesel motors or are pushed or towed by tugs. The size of a canal or river barge is limited by the waterway on which it operates. The barge must be short enough to make the curves in the waterway and narrow enough to pass through canals. Barges that operate in coastal waters can be practically any size.

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Multipurpose ships

Multipurpose ships are designed to haul several kinds of cargo at the same time. An example is the British ship Strathardle, launched in 1967. It has refrigerated space for foods that spoil easily, tank space for liquid cargo, and a deck for automobiles. The vessel is 563 feet (172 meters) long and 80 feet (24 meters) wide. Another multipurpose ship is the Bore VI, a small Finnish freighter also built in 1967. It hauls roll-on/roll-off vehicles, large rolls of paper, packaged lumber, and general cargo. This ship is 290 feet (88 meters) long and 49 feet (15 meters) wide. In 1968, the Mormacsea, the first American-built multipurpose vessel, was launched. It can carry containers, roll-on/roll-off cargo, and general cargo. It also has refrigerated space. The Mormacsea measures 602 feet (183 meters) long and 90 feet (27 meters) wide.

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Specialized types of vessels

Many ships and boats have been designed to do particular jobs. Refrigerator ships, traveling 22 knots or faster, speed fresh fruits, meats, and vegetables across the ocean. Tugboats tow barges along canals and rivers and guide huge passenger liners and freighters in and out of harbors. Oceangoing tugs take part in rescue and salvage work. Besides ferries that transport automobiles and passengers, there are train ferries that carry railroad cars across small bodies of water. Powerful icebreakers use their sturdy bows to ram through frozen waters and open a path for other ships and boats. Oceanographic ships carry instruments to study currents, tides, waves, and the animals and plants of the sea. Some modern fishing vessels are used not only to catch fish, but also to process them. These ships have equipment to behead, clean, and refrigerate the fish.

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Ships of the future

Future ships will be even more efficient than those of today and so will cost less to operate. More and more ships will carry containerized cargo, and all ships will be larger. Ships will become increasingly automated. A staff of engineers will no longer need to stand watch in the engine room. Instead, ship engines will be operated from the bridge, just as plane engines are run from the pilot's cabin. Electronic equipment will navigate tomorrow's ships automatically. A computer will determine a ship's course and, by sending the information to machinery that regulates the rudder, steer the vessel. As a result of these developments, ship officers will receive increased technical training. Crews will become smaller. Ship maintenance will no longer be done at sea by the crew, but in port by specialized workers. To avoid such maintenance work as painting, the bridge, cabins, and other structures on the main deck will be built of aluminum and other materials that do not rust and that resist wear from the chemicals in seawater.

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A ship at sea

The officers and crew of a ship work as a team to see that the passengers, the cargo, and the ship itself arrive at their destination safely and on time. To sail a ship long distances across open water requires great skill and experience. A change in the wind's strength or direction, or the force of the waves and currents, can put a ship off course. A ship's officers use equipment and methods developed hundreds of years ago—as well as modern devices—to tell where their ship is at all times.

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Officers and crew. A highly organized team of officers commands a ship. The top officer, called the captain or master, has final authority over and final responsibility for the passengers, crew, cargo, and ship. The captain has a number of deck officers, called mates, as assistants. The captain has at least a chief, or first, mate; a second mate; and a third mate. On large passenger ships, the captain may have one or two additional mates. All these officers must have a license, which they receive after passing a test given by a nation's government or some other authority. The U.S. Coast Guard issues licenses to officers on American merchant ships. The officers navigate the ship and command the deck crew.

The deck crew consists of able-bodied seamen (A.B.'s) and ordinary seamen. On American ships, both groups of seamen must hold certificates issued by the Coast Guard. Able-bodied seamen have more experience than ordinary seamen and have the more responsible tasks, such as standing lookout, helping steer, and making difficult repairs. Ordinary seamen do maintenance work.

The engine room has a separate organization. It is headed by a chief engineer, who is aided by first, second, and third assistant engineers. Like the captain and deck officers, all the engineers must have a license. The crew members in the engine room of a ship driven by steam turbines include oilers, who help tend the engines, and firemen, who fire the boilers.

A ship also has a number of other crew members. They include a chief radio operator; a chief steward, who is in charge of obtaining, preparing, and serving food; one or two cooks; and a mess staff, who serve the meals and assist the cooks.

Cargo and passenger ships carry the same basic groups of crew members. But large passenger liners and cruise ships have much larger crews to make a voyage as pleasant as possible for the passengers. The extra crew members include bakers, barbers and beauticians, bartenders, butchers, doctors and nurses, entertainers, launderers, printers, pursers (accountants), recreation directors, and a large staff of stewards and stewardesses. A big passenger or cruise ship may carry as many as one crew member for every two passengers.

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Navigating a ship. When a large ship leaves port, three or four small tugboats pull it from the pier into the harbor. A docking pilot directs the tugs and the ship until the vessel clears the pier and is underway in the harbor. The tugs then leave the ship and the docking pilot turns the vessel over to a harbor pilot. Every merchant ship enters and leaves port with a local harbor pilot aboard.

The harbor pilot guides the ship into the harbor or out into open water. The harbor pilot must know every channel, turn, sand bar, or other obstacle that could endanger the vessel. After a ship reaches open sea, a small boat comes out and carries the pilot back to port. The ship officers then navigate the vessel to its destination.

On the bridge, the navigator, usually the second mate, uses various equipment to locate the ship's position. As sailors have done for thousands of years, the navigator checks the position by observing the sun, moon, planets, and stars. For hundreds of years, the most important navigation devices have included a compass to tell direction, a chronometer to tell the exact time and help determine a ship's longitude, and a sextant to calculate a ship's latitude by measuring the angle of the sun or of a star above the horizon. See Compass; Chronometer; Sextant.

Modern ships also have highly accurate electronic navigation equipment. Many ships have devices for determining their position through radio signals. These signals are sent out continuously by special transmitting stations along the coasts of busy trade routes. One such system is called loran, for long range navigation. With loran, an accurate position can be obtained in bad weather and poor visibility without a compass, chronometer, or sextant (see Loran). Many ships also can determine their position by signals that are transmitted from orbiting satellites.

Modern ships also carry radar. At night and in bad weather, a ship's radar can spot icebergs, rocks, and other vessels in time to prevent a collision (see Radar). Some modern ships also have an automatic pilot, which, after a ship has been set on course, holds it there. This device is linked to a gyrocompass, which determines direction, and it operates the rudder automatically (see Gyrocompass). In spite of all these remarkable devices, navigators still also use the tried-and-true compass, chronometer, and sextant. For more information on how ships are navigated, see Navigation.

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Automation aboard ships is increasing, but no ship is as yet completely automated. Most automation has been in the engine room. When the officer on the bridge signals the engines to go ahead or backward or to change speed, the engineer no longer has to make adjustments by hand. Instead, the engines respond immediately. The operation of the valves and the necessary change in temperature or pressure are taken care of automatically. Many ships have automatic navigation aids and automatic devices to speed up the loading and unloading of cargo. Automation may one day make it possible for cargo ships to have only 9 or 10 crew members.

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Safety at sea. Safety standards for ships have been set up by International Safety of Life at Sea conventions, which were held in 1914, 1929, 1948, 1960, and 1972. All the major maritime nations have agreed to these standards. The standards require that ships have watertight bulkheads (compartment walls); fire-fighting equipment; and enough lifeboats, life jackets, and other lifesaving equipment. Other rules provide that lifesaving and fire drills be carried out at regular intervals. In addition, ships must follow the International Rules of the Road. These rules deal with such points as the rights of way of ships on the high seas, the lights ships must show, and the signals that ships must give in fog and during times of distress.

In 1930, all the leading seafaring countries accepted rules set up by the International Load Convention to keep ships from being overloaded. These rules require that cargo ships have a series of short lines painted on their side to show the depth to which the vessels may be safely loaded at various times of the year and in various waters. When a ship, being loaded with cargo, sinks in the water to a certain line, it has reached the maximum load. The lines are called Plimsoll marks. They are named after Samuel Plimsoll, a member of the British Parliament who brought about their adoption in the United Kingdom's Merchant Shipping Act of 1876. In 1966, the world's maritime nations agreed to new rules that raised the limits to which ships may be safely loaded. The new rules reflected improvements in ship design and construction since 1930. See Plimsoll mark.

In addition to international maritime laws, individual countries have regulations governing the construction and operation of their own ships. The United States has especially high safety requirements. In many cases, its standards are far higher than international rules require. These strict standards have made American ships exceptionally safe. They have also made U.S. ships much more costly to build and operate than foreign ships.

The U.S. Coast Guard sees that American vessels meet the standards set up by the federal government. The Coast Guard must approve the construction plans for each new ship. It inspects the ships during their construction to make sure that they are being built according to the plans. At regular periods, the Coast Guard also checks all merchant ships in active service to make sure that they meet all safety regulations.

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The art of shipbuilding

A ship is one of the most complicated objects ever made. It is actually a floating city that generates its own power, heat, and electricity. A ship carries its own fuel and provisions. It can make its own fresh water from the sea, and it disposes of its own garbage.

All ships have four main parts. In designing a ship, naval architects plan these and other parts of the vessel so that it meets a shipping company's special needs as well as government safety regulations. A shipyard then builds the ship according to the architect's plans.

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The chief parts of a ship are (1) the hull, (2) the engines, (3) the propellers, and (4) the rudder.

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The hull is the watertight shell of a ship. It is divided into a number of horizontal surfaces called decks. Bulkheads are walls built between the decks, forming compartments. Each compartment has special doors that, when closed, make it watertight. If water floods one compartment because of an accident, closing the doors will trap the water there and prevent it from flooding other compartments. Watertight compartments enable a ship to float even with a hole in its hull.

The deck at the top of the hull is called the main deck. Several more decks may be above it. All the structures above the main deck make up the superstructure.

Hulls have a pointed bow so they can knife swiftly through the water. Most hulls also have a rounded stern, which helps the water close smoothly behind as the ship cuts through the water. The overall shape of a hull is designed to make the ship as stable (steady) as possible. A ship must not roll (rock from side to side) or pitch (rock from front to back) too much. Most modern ships also use stabilizing systems to reduce rolling. One such system has a horizontal underwater fin on each side of the hull. The fin moves upward on the descending side of the ship and downward on the ascending side and so reduces the roll.

To increase stability further, ships carry extra weight called ballast. Without ballast, an empty cargo ship would bobble about in the ocean like a cork. Most ships use seawater as ballast. As a ship takes on cargo, the ballast water is pumped out.

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The engines of most ships are steam turbines, gas turbines, or diesel engines. The largest and fastest ships have steam turbines. Steam produced in the boilers spins the bladed wheels of the turbine. The turbine, through a series of gears (toothed wheels), drives the propeller shaft and makes the propeller revolve. On turboelectric ships, the turbine turns a generator that produces electricity for a motor. The motor, in turn, drives the propeller. Almost all merchant ships use oil as the fuel to heat the boilers that create the steam. On nuclear-powered ships, a nuclear reactor creates the steam. Many of the most advanced ships have gas turbines. Gas turbines work much like steam turbines but use hot gases instead of steam. See Turbine.

Vessels propelled by diesel engines are called motorships. They have either geared-drive or diesel-electric machinery. On a geared-drive ship, the engine works through gears to turn the propeller. On a diesel-electric ship, the engine turns a generator that supplies current to an electric motor connected to the propeller shaft. See Diesel engine.

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The propellers, also called screws, move a ship through the water. The engine turns a shaft that juts out underwater from the stern. The propeller is bolted to the end of the shaft. Most propellers have four blades. As a propeller turns, it screws itself through the water and so pushes the ship forward. Most small ships have one propeller. Many larger vessels have two propellers, and very big ships have four. Additional screws increase a ship's power and make the vessel easier to maneuver. For example, a twin-screw ship can be swung around quickly by going forward on one propeller and backward on the other. Some ships have an extra propeller called a bow thruster. This propeller, which is located in the bow, turns the ship more rapidly than stern propellers alone. See Propeller (Ship propellers).

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The rudder is a large flat piece of metal that steers a ship. It is hinged to the stern and so can be swung like a door. The rudder is connected to the helm (steering wheel) on the ship's bridge. When the sailor at the helm turns the wheel to the right, the rudder moves to the right, causing the stern to swing left and the bow to swing right. When the helm is turned to the left, the rudder and bow swing to the left.

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Other parts and equipment of a ship include funnels (smokestacks) to discharge smoke and exhaust fumes, an anchor on the left and right sides of the bow, and enough lifeboats to hold all persons on board. Modern ships have power-driven winches to raise or lower the anchors and to bring in or let out the mooring lines used to tie vessels at a pier. Power-driven winches also operate the cranes for loading and unloading cargo. Modern ships also have high-speed pumps to pump out ballast water or to pump up seawater in case of fire. Radio-telegraph equipment keeps ships in constant touch with the rest of the world.

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Designing and constructing a ship. Before naval architects begin to design a ship for a shipping company, they must know how the firm plans to use the vessel. They must know where the ship will sail, what kind of cargo it will carry, and how fast it will have to travel. Architects also must be aware of government safety regulations. In addition, they must adjust their designs to allow for the ever-increasing use of automation on ships.

The shipyard carefully follows the architect's designs in building a ship. Traditionally, construction begins with the laying of the keel. Workers then build the ribs that support the hull and give it shape. Next, they weld the metal plates that form the middle section of the hull. As the middle section is built, the various compartments, the boilers, and the necessary machinery are added. Finally, the bow and stern are built, completing the hull.

Modern shipyards no longer construct ships in this piece-by-piece manner. Instead, they first build enormous prefabricated sections of the ship in subassembly shops. Many of these sections have some wiring and piping built into them. Giant cranes then carry these huge sections to a framework called a shipway, where they are welded together. There is no laying of the keel. As the double-bottom sections of the hull are welded together, the keel is laid automatically. The entire hull may consist of as few as 20 prefabricated units. After the hull is completed, parts of the superstructure are added. The ship is then ready to be launched.

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Launching and outfitting a ship. Shipbuilders launch a ship after it is about 70 to 90 percent completed. The ship is slid down a runway of heavily greased timbers into the water. Most ships are launched stern first. A ship launched bow first would plow down into the mud. Ships built along rivers too narrow for stern launching are launched sideways. Some yards build their ships in dry docks below the water level. After the hull and superstructure have been completed, workers open the valves and flood the dock. The ship then gently floats off the blocks that support the bottom of the hull. After the water inside the dock reaches the level of the water outside it, the dock gate is opened and the ship is launched.

Just before a ship is launched, it is christened. The shipping company selects a person, usually a woman, as the ship's sponsor. This person names the vessel and breaks a bottle of champagne across its bow. At that instant, the ship begins to slide into the water.

After a ship has been launched, a tug pulls it to an outfitting pier. There, workers complete the superstructure and add the interior furnishings. The ship then makes its builder's trials with observers aboard from the company that ordered the ship. They make sure that all the equipment is in good working order and that the ship performs maneuvering, speed, and other tests according to the specifications. If the ship returns from the trials with a broom tied to the mainmast, it has made a "clean sweep" of its tests and the shipping company has accepted delivery of the vessel.

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Merchant fleets of the world

Altogether, the countries of the world have about 100,000 merchant ships of at least 100 gross tons. About 33,000 of these ships are of 1,000 gross tons or more. The world's merchant vessels total more than 600 million gross tons. Each year, millions of gross tons of new shipping are built. China, Japan, and South Korea produce most of the total gross tonnage of ships launched annually.

In the United States and a number of other countries, many companies register their ships under the flag of another nation. They do this in order to operate their vessels with lower-paid crews, avoid strict safety regulations, and pay lower taxes than they would by registering in their own countries. A number of nations allow their flag to be used in this way as a flag of convenience for a registration fee. Countries that have a flag of convenience include Antigua and Barbuda, the Bahamas, Cyprus, Honduras, Liberia, the Marshall Islands, and Panama.

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The United States merchant marine consists of thousands of vessels, including those that sail the Great Lakes and other inland waterways. All of these vessels are registered in the United States and fly the American flag. The size of the United States merchant fleet and the fleets of other maritime nations varies according to the level of world trade. In addition, many United States merchant ships are inactive or past the age of active use. The United States is the chief trading country in the world. Yet American-flag ships carry only about 4 percent of the country's foreign trade.

The federal government requires that all merchant ships registered under the United States flag must be American-built and operated by American crews. But building and operating ships costs about 50 percent more in the United States than in the lowest-cost shipyards, which are located mainly in Asia. American-flag ships can compete against foreign vessels only with the help of subsidies (grants of money) from the government. The government grants subsidies because it believes that a merchant fleet is vital to the country's foreign trade and national defense. For example, without a merchant marine, the nation would be completely dependent on foreign shipping lines—which owe no allegiance to the United States—to carry American trade. During wartime, U.S. cargo ships are needed to carry supplies, and shipyards in the United States must be in operation to build warships.

Under the Merchant Marine Act of 1936, the Maritime Administration has control over subsidized shipping lines. The act requires that such lines provide regular service on trade routes that the administration selects as essential to United States foreign trade and defense. Subsidized operators must also replace ships that the administration considers too old and inefficient for service.

Many American ship operators prefer not to accept government subsidies. Instead, they buy their ships from foreign shipyards at about 50 percent less than American-built vessels and register them in a country that has a flag of convenience.

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Merchant fleets of other countries. Many countries have a long tradition as seafaring nations. They include Denmark, France, Italy, the Netherlands, Norway, Sweden, and the United Kingdom. In addition, Japan and a number of other nations have developed large fleets of ships.

Panama and Liberia have the largest merchant fleets in the world. Each country allows its flag to be used as a flag of convenience. Companies of other countries own almost all the ships of the Panamanian and Liberian fleets.

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