The word ship, from scip in Old English and Old Norse and schiffe in German, signifies any large waterborne vessel. In strict usage the word implies a vessel larger than a boat; custom among English-speaking people, however, has blurred the line dividing the two. Thus, fast mail and passenger steamers of considerable size are often referred to as packet boats (French, paquebots), and, indeed, people other than professional seamen often refer to any passenger liner as a boat. This article discusses the ship in various forms and during different periods. The earliest vessels (see also \Tboat and boating\t) are discussed briefly in the first section, which treats sailing ships and the history of their development. (Warships, mentioned here only briefly, are discussed in \Tnaval vessels\t.) Materials, shapes, and nomenclature for the sails themselves are also dealt with here, and the section concludes with the rigging of sailing ships. Engine-powered ships are then discussed--first steamships and then more modern forms of propulsion, such as turbines, diesels, and nuclear power. A section on specialized types of ships treats \Lair-cushion vehicle\ls, \Locean liner\ls, \Ltanker\ls, \Lhydrofoil\ls, and cargo carriers. Related articles include \Tnavy\t and \Tshipbuilding\t. Separate articles treat many individual types of merchant and military vessels. THE AGE OF SAIL The earliest sailing craft were no more than flat rafts with a short mast set into position so that a single square sail could be hoisted. The \TKon-Tiki\t is a balsa-wood replica of such an early craft on which the Norwegian explorer Thor \THeyerdahl\t and his companions crossed the Pacific in 1947; it is now preserved in the Kon-Tiki Museum in Oslo. The oldest ship of which there is definite knowledge was built for the funeral of the pharaoh Cheops (3960-3908 BC). Found near his tomb in a trench and covered with sand, this ship was an open-hulled vessel (that is, it had no deck) 40 m (133 ft) in length, with a maximum beam of 8 m (26 ft). It was constructed of about 600 separate pieces of wood, the largest being 23 m (75 ft) long. It was probably used only for Cheops's funeral and neither went to sea nor floated on the Nile. Much evidence exists, however, in contemporaneous rock carvings and paintings from which it can be deduced that the Egyptians employed similar ships for trading on the Mediterranean. Similar sources also indicate that, although such ships were normally propelled by oars manned by slaves (perhaps 15 to each side), the Egyptians also harnessed the natural power of the wind by hoisting a square (more accurately, rectangular) sail from a yard and hoisting it on a mast stepped (erected) amidships. Such a ship was steered by an extra-large oar slung over one quarter for which the word steerboard was coined--hence the term starboard for the right side of a ship. Phoenician, Greek, and Roman Ships The Phoenicians, who ruled many of the Mediterranean shores from about 1000 to 250 BC, improved on the Egyptian design. They built similar vessels (see \Tgalley\t) of approximately 30 m (100 ft) in length, with which to trade on the Mediterranean, and larger Tarshish ships with which they ventured out through the Straits of Gibraltar, up to the Scilly Isles, and--if Herodotus is to be believed--around the Cape of Good Hope into the Indian Ocean. The Greeks also built merchant ships, tubby craft that relied mainly on sail. By this date the basic principles for building the hull of the type of ship used in European waters had been developed. The frame comprised a longitudinal keel (backbone), with stemposts and sternposts, and athwartship ribs. This structure was transformed into a watertight vessel by covering it with a skin of wooden planks coated with pitch. These might overlap (clinker built) or be flush (carvel built), the latter becoming the more usual form. As soon as they became available, iron nails replaced the wooden pegs with which a ship's scantlings (thin strips of timber) were secured. Otherwise, except for the addition of stringers (longitudinal members) to give the frame greater strength, ships were built in this manner until metal replaced wood as a structural material. From wall paintings found in tombs near Rome, it appears that from about 450 BC a ship's carrying capacity was increased by building up its bulwarks (structures above the upper deck). The same source indicates that by this time some ships stepped two masts, with a sail hoisted on each. Because they were so broad-beamed, or wide, such trading vessels were known as "round ships." The Greeks increased their size. The Romans introduced the idea of partly decking their ships to provide passengers and crew with shelter from the elements. They also recognized that by adjusting the angle of a ship's sails relative to the fore-and-aft line, the ship could hold a course other than one with the wind blowing from behind. Chinese and Middle-Eastern Ships In the Far East the Chinese evolved a different design of vessel, the \Tjunk\t. They joined together two dugout \Lcanoe\ls, using planking, and then built up the sides, bow, and stern to form a flat-bottomed wooden box, that is, a hull without a keel. A wedge-shaped addition provided this box with a bow. Its stern was built up so that it would remain dry in a following sea. Inside, on the center line, a second, vertical, watertight box contained the steering oar. The Chinese junk was well suited to the waters it plied and the winds in which it sailed. The Chinese version of the fore-and-aft sail was in use about 250 BC, some 15 centuries before the Western world discovered it; their stern rudder was devised even earlier. Later junks were decked and, more important, were divided into separate compartments by means of transverse bulkheads, an improvement that was not introduced in the West for many centuries. Marco Polo described a junk with more than 50 private staterooms. The largest junks were easily as large as the Western square-rigged ships of the 18th and 19th centuries. Most innovative of the Chinese maritime innovations were their lug sails, stiffened with full-length battens and controlled ingeniously to shorten sail like a Venetian blind or to sail into the wind like a modern racing yacht. Naval architects have designed fully battened sails for greater efficiency on small racing yachts, but only the advent of electrically operated roller furling (inside the mast or around a stay) has brought the equivalent easy sail handling to modern sailboats. The Japanese, Javanese, and other Eastern civilizations built their own forms of the junk. With their many variations, these craft were superior to any Western vessels built before the 17th century. They were more seaworthy and able to sail closer to the wind. For this reason the basic junk design has endured to the present day, and junks still carry passengers and cargo off the Chinese coast and on the Yangtze and other Chinese rivers--as well as throughout the Orient. The small variation of the junk, the sampan, often is used today with an outboard motor as a power adjunct. The steady winds of the northeast monsoons created a special situation in the Indian Ocean, and the Arabs, Persians, and Indians devised a lateen-rigged type of vessel that was well suited to it. The triangular-sailed dhows that ply the Red Sea, the Persian Gulf, and the Indian Ocean today are thought to be little different from those of 2,000 years ago. The Egyptian felucca, used on the Nile River, is an adaptation of the dhow. Although sail handling is difficult with the special fore-and-aft sails of the lateen rig (the sail must be lowered and then raised again with each major change in direction), such handling is not often required, because on most dhow sailing routes the wind blows from one direction for days on end. Early European Ships The 7th century AD brought a new era in European ship design. From remains such as the Nydam boat found near Flensburg in Holland in 1863, and another vessel discovered more recently in a burial mound at Sutton Hoo in England, it is known that the vessels with which the Vikings carried out their overseas raids were long and narrow, and of shallow draft, so that they could be beached easily. Sometimes propelled by oars, they were more usually driven by a single, large, square sail. A century later these Viking longships, such as the one whose remains were found at Gokstad in Norway in 1880, were around 25 m (80 ft) in length, and double ended, with bow and stern rearing up in a graceful sweep, the former having a curved figurehead. Each gunwale was pierced with holes for 16 oars, and a single mast stepped amidships carried a large, square, painted sail. To judge from the \TBayeux Tapestry\t, the ships used by William the Conqueror to invade England in 1066 were of this design, except for being partially decked and having a corvus (small castle) at bow and stern, from which soldiers used their bows and arrows against the enemy before they came close enough to board. By this time, sail was replacing the oar as the prime means of ship propulsion. The invention, in the 12th century, of the rudder to replace the steerboard greatly facilitated steering, enabling seamen to learn that by bracing their ships' sails at a sharp angle to the fore-and-aft line, they could set a course close-hauled, that is, about 45 degrees off the direction of the wind. These developments were followed by an increase in the number of masts and sails (especially the latter) when it was discovered that several small sails could be more easily handled by a ship's crew than a single large one. In the 13th century the most common type of ship in northern European waters was the single-masted cog, with a broad beam and deep draft that gave it a considerable cargo-carrying capacity. The more advanced countries bordering on the calmer waters of the Mediterranean evolved the two-decked, finer-lined \Tcaravel\t. Initially lateen rigged on two masts, the caravel soon stepped three masts--foremast, mainmast, and mizzenmast--with square sails on the forward two and a lateen sail on the third. Ships in the Age of Exploration The great discoveries of the 15th and 16th centuries, by such men as Bartolomeu \TDias\t, Ferdinand \TMagellan\t, and Christopher \TColumbus\t, were all made in caravels. Unhappily, none has been preserved for posterity, but full-sized replicas of Columbus's Santa Maria have been built in recent years. From these replicas a good idea of what such vessels were like can be obtained, and it is difficult to see how these early explorers managed to complete their voyages in such frail, small craft. With the opening of all-sea routes from Europe around the Cape of Good Hope to the Far East, and across the Atlantic to the New World in the west, came a great increase in seaborne trade. This additional volume of transported goods required larger merchant ships. Spain led the way by designing and building carracks of as much as 1,600 tonnage. These and the later \Lgalleon\ls (which had rigs similar to those of the three-masted carracks, with the addition of topmasts and with up to three decks) were the forerunners of the full-rigged ships that came to dominate naval architecture until the general introduction of steam propulsion in the mid-19th century. Ships of the 17th and 18th Centuries The caravel-built sailing ships of the 17th and 18th centuries--notably those of the British and Dutch \LEast India Compan\lies, which had been established to obtain and bring to Europe the valuable products of the East Indies--were the epitome of the shipbuilder's art until, in the 19th century, wooden hulls were superseded by iron (and, later, by steel). Known as East Indiamen, some of these ships were more than 60 m (200 ft) long, more than 15 m (50 ft) in breadth, and of greater than 2,000 tonnage, with up to five decks. All these ships were armed with broadsides of 24- and 32-pounder guns, after the manner of warships, for protection against privateers (warships of other nations) and pirates. Many were elaborately gilded and decorated with carvings, and most were ship-rigged with lower masts, topmasts, and topgallant masts. They were also the first sailing vessels to have luxuriously furnished cabins for passengers in addition to holds for cargo. None of these splendid ships has survived, but an idea of what they must have looked like can be gained not only from contemporaneous paintings, particularly those of the Dutch school, but also from the Swedish warship Vasa (completed in 1628), recently salvaged from the bottom of Stockholm Harbor and now preserved in Stockholm, and from Lord Horatio Nelson's flagship, H.M.S. Victory (completed in 1778), which is kept in dry dock at Portsmouth, England. Merchant ships similar to East Indiamen were used for bringing to Europe the products, notably sugar, of the West Indian islands colonized by Britain and France. Smaller vessels, however, were built for coastal and inshore trading, like bringing coal from Newcastle to London, and for inshore and deep-sea fishing. Pleasure yachts, devised by the Dutch and brought to England by Charles II, also appeared at this time. These retained either two masts or, more usually, only one. 19th-Century Ships In the 19th century the need for larger ships with greater cargo capacity--necessary both for the Chilean nitrate trade and for the Australia run, where emigrants were taken to Australia and wool brought back to Europe--produced larger vessels carrying from four to seven masts. Similarly, the demand for faster ships--in the United States for carrying prospectors from the east coast to the goldfields of California and Australia, in Britain for the China tea trade--led to the design of the slender, square-rigged craft known as the \Lclipper ship\ls, which carried both passengers and cargo. The best of the clippers reached speeds of 18-20 knots (32-37 km/h; 20-23 mph) and bore such appropriate names as Lightning and Flying Cloud. A day's run of 702 km (436 mi), set by the Lightning, was so good that many 20th-century steamers cannot match it. Dreadnought was one of the most consistently fast clippers, often beating Cunard steamers on the Atlantic. Her record run was 13 1/2 days, from New York to Liverpool. Donald \TMcKay\t's clipper, Great Republic, was (at 4,555 tons) the largest wooden ship ever built. She was 102 m (334 ft) long, and her four masts carried more than 0.6 hectares (1.5 acres) of canvas. Soon after her launching she caught fire and was rebuilt with a smaller rig. The great ships and their captains were the heroes of their day, and a Currier and Ives lithograph of a famous clipper ship was a popular item in the mid-19th century. Clipper ships and packet boats--speedy, slim-lined sailing ships that ran regular routes between Europe, the Americas, and China, carrying mail, official government cargoes, and such special passengers as ambassadors--were the fastest ships of their time, but their carrying capacity was necessarily restricted by their fine, sharp lines and their V-bottom hulls. Nevertheless, the British tea trade placed such a high premium on speed that the clipper-ship era lasted long after dependable, but slower, steamships were available. The famous race between the two British clippers, Thermopylae and Cutty Sark occurred as late as 1872. The race, however, was an anomaly in the progress of the British maritime industry, which had adopted iron-hulled steamships while U.S. shippers were still using wooden clippers. In the 20th century mechanical propulsion almost entirely replaced sail, except in the Far East where junks are still widely used. By 1934 only 40 square-rigged sailing ships remained afloat, 16 of these being used by various countries for training purposes. Most of the rest, owned by a Finnish company and used to bring bulk cargoes from Chile and Australia to Europe inexpensively, had a loaded displacement of as much as 5,000-7,000 tons. Today only about 20 large sailing ships remain in service worldwide. The Yacht The one notable exception to the demise of the sailing ship is the yacht, a sailing vessel used for both pleasure and racing purposes. Yachting proliferated worldwide, especially after World War II. Even so, yachts such as those that compete for the America's Cup are smaller than the famous "J" class of the 1920s and '30s. Neither in size nor in number of sails carried can these compare with such ships as East Indiamen, China tea clippers, or the great Australian wool barks of earlier times. Capt. Geoffrey Bennett Sails and Rigging In the 19th-century heyday of sailing ships, strict maritime usage limited the appellation ship to square-rigged vessels only--those with three or more masts, each with a topgallant mast, and each crossed by at least five yards, the spars that held the great square sails that gave the ship her power and her singular beauty. Supporting and controlling sails and masts, hundreds of separate lines, cables, ropes, spars, blocks, tackles, and lifts were organized into a system of enormous complexity, but one that any sailor knew as well as the palm of his hand. Along with the parts of the body of the ship itself, each mast, sail, cable, spar, and rope had its name, and thus nautical nomenclature is among the largest and richest of any technology. Limitations in the available materials, of course, influenced the design and size of almost every part of the ship. Trees that were large, straight, and strong enough to make a complete mast (some masts were more than 60 m/200 ft tall) were rare. Hence the mainmast ended in an iron and timber structure, the top, on which was mounted the topmast. The topmast in turn supported the topgallant mast, which could be lowered and replaced, if necessary, even at sea. The top-most mast--used only on the largest ships--was called the royal. The great square sails hung in ordered procession--as many as five or six each for foremast, main mast, and mizzenmast--across each mast. Each sail was suspended from its yard, and these were supported (in fact, raised and lowered when necessary) by a system of rope or chain braces, used to change the angle of the yards, and thus the sails, to take advantage of changes in wind direction. Each square sail had its name: mainsail, topsail, topgallant sail, royal, skysail, and moonsail--each smaller as one looked upward. The sails were further identified according to the mast on which they were set (mizzen royal, main royal). There were special names for a few: the crossjack, or "crojack," lower square sail on the mizzenmast, and the corresponding sail on the foremast was the foresail, or forecourse. The distinction between square sails and fore-and-aft sails is an important one. Early fore-and-aft sails, usually triangular in shape, were hung abaft the mast (that is, in the direction of the length of the ship; square sails hung athwart, or across the width of the ship) on gaffs that were suspended at an angle from the mast. Fore-and-aft ships generally carried only two sails per mast. Fore-and-aft schooners, and ships that used combinations of fore-and-aft and square sails--the brigantine, barquentine, and topsail schooner--did not require large crews to handle their relatively fewer sails. Although they were often slower than the square-riggers, they were easier to operate, and because they could sail closer to the wind, they were handier for coastal voyages. The square-riggers used the steadier trade winds and plotted their routes to make the most of them. Modern sailboats still use these fore-and-aft sails and have kept their names: staysail, jib, and spanker, among many others. Most ingenious of all the sails on a square-rigger were the studding sails (pronounced "stunsails"), which were small extensions hung at either side of a square sail in light air to add extra drive and speed. One is more likely to see ships under full sail, complete with studding sails, in bank calendar illustrations than in authentic old photographs, for these sails were difficult to handle and useful only in very special wind conditions. The "moonraker," set on a special pole above the topmast, was the most fancifully named sail of all, and the least often seen. Around the world sails had been made from papyrus, palm leaves, straw matting stiffened with bamboo strips, animal skins, and canvas woven of flax. Flax sails were on all the great explorers' ships, as well as on those of Admiral Lord Nelson and Captain Cook. By the time the sailing ship reached its technological apex, however, most sails were made of cotton. American ships of the mid-19th century advertised Yankee cotton to all the world. For the finest yachts, however, sailmakers used Egyptian cotton, with its very long fiber. The rigging that held the masts and controlled the sails in the age of great sailing ships--and still does today on all sail-equipped vessels--was divided into two main types: standing rigging and running rigging. Generally speaking, standing rigging was more or less permanently in place, holding the masts and sometimes the bowsprit, the large spar projecting over the bow of a vessel. Rope shrouds supported the masts on each side (with cross ropes called ratlines, by which the crew could climb), and stays held the masts fore and aft. When standing rigging was made of rope it tended to stretch and shrink, depending on the strains put upon it, the wetness or dryness of the weather, and the materials from which it was made. To tighten the shrouds, sailors used wooden blocks called deadeyes. A pair of deadeyes, rigged with lanyards, could be hauled tight, or tighten the shrouds. Later, when iron and steel wire rigging was manufactured, turnbuckles or rigging screws proved to be an infinitely more efficient system. Running rigging controls the smaller spars and the sails. Halyards (" haul yards") were originally used to lift the yard. On today's sailboats they hoist the sails. Downhauls and lifts do what their names suggest. A buntline is a rope used to pull up the bottom of a topsail, thus spilling the wind the sail is holding. A furling, or gasket, line wraps around a furled sail, tying it to its mast or yard. Reefing halyards were used to rotate the yard, rolling the sail around it and reefing (shortening) it. A square sail--and modern conventional sails--use reef points, short ropes attached along the sail's width to tie it to the yard or boom when reefing it. ENGINE-POWERED SHIPS The attempt to use a \Tsteam engine\t to propel a ship had been made almost since James \Twatt\t, in 1774, began manufacturing his first engines. In 1776, for example, the Frenchman Claude Francois, marquis de Jouffroy d'Abbans, installed a Watt engine in a 13-m (42-ft) boat. It was, however, the invention (1802) by the Scottish engineer William Symington (1763-1831) of the crank and connecting rod--which converted the back-and-forth motion of the engine's piston rod into a rotary motion that could rotate a paddle wheel--that first made steam propulsion a practical means of powering waterborne craft. In 1807, Robert \TFulton\t installed a Boulton and Watt steam engine in his 45-m (150-ft) vessel, the \TClermont\t. On her first voyage the Clermont's 4.5-m (15-ft) paddle wheels took her from New York to Albany and back, a distance of 240 km (150 mi), in 62 hours. Fulton's was the first successful steamboat. The paddlewheeled ships that followed Fulton's prototype were capable of both speed and maneuverability and were well suited to river and bay transport. Paddle wheels, however, were a disadvantage in the rough waters of the oceans. The age of the steamship was slow in coming. Wary of fire and distrustful of the new mechanisms, shipbuilders continued to include a full complement of masts, spars, and sails. The U.S. ship \TSavannah\t, the first steamship to cross the Atlantic (1819), had a dozen sails and used them far more than she did her steam engine, which operated for only 80 hours in a voyage of 27 days. The British ship Sirius was the first to cross the Atlantic entirely under steam power (1838), although she ran short of fuel en route and was reduced to burning her spars and furniture. The maiden voyage of the Great Western was made the same year. A wooden ship of 72 m (236 ft) in length--considerably longer than most oceangoing ships of the time--with four boilers providing steam for her paddle wheels, she made the Bristol-New York run in 15 days, at an average speed of 8 knots (14.8 km/h; 9.2 mph). She became the first steamer in regular transatlantic service and inspired Sir Samuel \TCunard\t to inaugurate his shipping line, beginning, in 1840, with wooden paddle steamers that made the twice-monthly Liverpool-Boston voyage in an average of 15 days. Cunard's lead was soon followed by other shipping lines: the Royal Mail Steam Packet Company sailed from Great Britain to the West Indies; the Peninsular and Oriental Steam Navigation Company ran between Britain, India, and China. The Great Western had been the engineering creation of Isambard Kingdom Brunel (see \TBrunel\t family), the most important ship designer of his day. Brunel recognized the advantages of large ships on the rough waters of the Atlantic and the need for large coal bunkers to carry sufficient fuel to power them. His basic contributions to ship design--such as the double bottom--were still in use more than a century after his death. Brunel's Great Britain (1843) was the world's first large iron ship and the first to use a screw propeller. Screw Propellers The principle of the Archimedes screw was common knowledge, but only in the 1830s were attempts first made to apply it to ship propulsion. The Frenchman Frederic Sauvage, the Swede John \TEricsson\t, and two Englishmen--Robert Wilson and Francis Pettit Smith--all contributed to its invention, although Smith was awarded the patent. Within a few years, improvements in propeller design were in use on steamships and naval vessels built throughout Europe and the United States. The first propellers consisted of two very thin blades, resembling those of an aircraft propeller; soon, however, three-bladed, four-bladed, and eventually multibladed propellers of increasingly sophisticated design were in use. The increasing horsepower of the engines added to the capabilities of the propellers; soon ships carried several engines, with each engine driving its own propeller, adding thrust, speed, and maneuverability. Brunel's third ship, the \TGreat Eastern\t, was launched in 1858; 211 m (692 ft) long, and displacing 27,400 tons, she carried a crew of 400 and 4,000 passengers, and remained the largest ship in the world until the end of the 19th century. The Great Eastern retained six masts and an elaborate suit of sails, but she also carried a set of paddle wheels run by one steam engine, a propeller run by another, and--another Brunel innovation--a separate engine to power her steering. During the next 20 years, as paddle wheels were superseded by screw propellers, marine engines also steadily improved. Engines became more powerful and sophisticated. Most were compound engines of various kinds, in which the steam was used first in a high-pressure cylinder and then in one or more low-pressure cylinders. The final form of the marine steam reciprocating engine, which was to be adopted in the latter half of the 19th century, was the triple- or quadruple-expansion engine with its cylinders placed vertically above the connecting rods and cranks. New \Tboiler\t designs were capable of generating steam at ever higher pressures. Turbines Just at the point where it seemed that no further improvements could be made in piston steam engines, the steam \Tturbine\t began to make significant inroads in ship propulsion. The work of the English engineer Sir Charles Algernon \TParsons\t was particularly important. After inventing (1884) a turbine-driven dynamo--some 200 of which were used to power ship lighting systems--he turned his attention to the powering of ship propulsion systems. His first turbine-propelled vessel, the Turbinia, made such an impression at the Royal Fleet Review in 1897 (it passed through the British fleet at 34 knots, or 63 km/h; 39 mph) that it was rapidly adopted for small warships, such as destroyers, and for increasingly larger ships until, with its installation (1905) in the \TDreadnought\t, a revolutionary new battleship, it became the form of propulsion for all warships. The first turbine-powered merchant ship (1901) was a small British packet boat, King Edward, which ran in the Firth of Clyde in Scotland and attained a speed of 20 knots (37 km/h; 23 mph). The Cunard Carmania was the first liner to install a steam turbine (1904). The famous Cunarders \TLusitania\t and Mauritania (the latter, for almost a quarter century, was the fastest ship on the Atlantic) were equipped with Parsons turbines, as were most transatlantic liners as the 20th century progressed. During the coal-fired era, the steam turbine was preeminent for driving a high-speed ship, but it was not as economical as the triple-expansion reciprocating engine. The advent of oil as a fuel eventually transformed this situation. Rudolf Diesel had patented his \Tdiesel engine\t in 1892. The small Dutch tanker Vulcanus was the first merchant ship to be fitted with a diesel, in 1910. Well into the opening years of the 20th century, the two eras of maritime history overlapped. The shoreline of any great port city still showed a mixture of tall masts and crossed yardarms with the smokestacks and funnels of steamships. Powered versions of almost every type of vessel were now in use. Some, such as the towboat and harbor tug, existed only in powered form. Curiously, the steam tugboat had helped the sailing ship survive into the 20th century, enabling her to move in and out of the slips, piers, and docks of modernized harbors without the necessity of maneuvering to take advantage of the wind or compensate for tidal currents. In addition, the skill of a seaman was still measured by his knowledge of sailing. For another 50 years the Cunard Line required captains to have served under sail. This was not simply a nostalgic gesture: the action of winds and waves on the hull of a great steamship could be just as difficult to handle as on a sailing vessel, and skills gained under sail were invaluable in directing large powered craft, especially in storm conditions. By the third decade of the 20th century, however, the sailing vessel had vanished from the fleets of western commercial ships (although they continue to be used--especially in conjunction with engines--throughout Asia and Africa). By the late 1960s almost 60 percent of all commercial ships were powered by diesel, steam turbines drove 30 percent, and only 11 percent still used the old steam reciprocating engines. The common fuel, however, was oil; few large ships continued to use coal. New Power Systems Whereas conventional steam turbine installations with oil-fired boilers--or, alternatively, multicylinder diesel engines--are the propulsion systems in universal use for merchant ships, two new power systems have been introduced for warships--nuclear power and the gas turbine. Nuclear-powered vessels use nuclear reactors to provide the heat to raise steam to drive turbines. The gas turbine is a self-contained unit driving the propeller shaft through reduction gearing; it requires little supervision, is small and light, and has a very short start-up time. Nuclear power has the advantage of providing power for long periods and for millions of kilometers of high-speed steaming without the need to replenish its fuel (the core of the reactor). It has been installed in a number of U.S. Navy aircraft carriers and guided-missile cruisers. Another advantage of nuclear power is that it does not require access to the atmosphere and is thus ideally suited to the \Tsubmarine\t. The navies of the United States and the \TUSSR\t each have large fleets of nuclear-powered submarines. The British and the French are also building nuclear-powered submarine forces. The high cost of nuclear-power systems and the reluctance of some nations to allow nuclear-powered ships in commercial docks have inhibited the application of nuclear power to cargo-carrying merchant ships. Only one has been built, the U.S. ship Savannah of about 14,000 tons. Put into experimental service in 1959, the Savannah did not prove to be commercially competitive and has since been laid up. The Soviets have the \Ticebreaker\t Lenin, of about 16,000 tons' standard displacement, which was the first nuclear-powered surface ship when it went into service in 1959. Gas turbines, too, are not economically suitable for merchant ships and are confined to small warships. Such ships may be equipped either with a system combining steam and gas turbines, the latter being used to boost the former for full speed and to provide instantly available power at all times, or with a large and powerful gas turbine for full power and smaller ones for economical cruising speeds. Although petroleum is still the main source of ship's fuel, its high cost has encouraged the tentative and experimental return of the sail on freighters and fishing boats, which use them as auxiliaries to their usual propulsion systems. SPECIALIZED TYPES OF SHIPS During the first half of the 20th century the great passenger liners dominated the ocean routes. Great Britain had long controlled most of the famous ocean runs, but in the second quarter of the century the French, Italian, and U.S. lines began competing with ever faster and more luxurious ships. The great expansion of air travel after World War II, however, dethroned the liners almost overnight--just as the time for transatlantic ship passage was cut (1952) to 3 days, 10 hr, 40 min by the S.S. United States. Within two decades, most of the liners were out of service; those which remained were used as cruise ships or were docked as floating museums (for example, the R.M.S. \TQueen Mary\t at Long Beach, Calif.). The last liner to be built, Cunard's \TQueen Elizabeth\t II (1968), was smaller and slower than many of her predecessors. She now serves primarily as a cruise ship. Cargo Ships A number of types of cargo carriers also plied the oceans, varying between the cargo liners of the more prestigious companies and the tramp steamers finding their cargoes wherever they were offered. For mixed cargoes the most usual type was the "three island," in which the "islands" were the raised poop, midships bridge superstructure, and forecastle. Homogeneous bulk cargo, such as grain, mineral ores, coal or oil, required other designs. The "turret" and "trunk" ships carried grain and ore. \Ltanker\ls for transporting crude oil made their first appearance in 1885. These cargo ships required special features such as the cofferdams separating the tanks from other spaces to prevent leakage from one to the other, expansion trunks, mechanical venting, and steam heating to reduce oil viscosity in cold weather. They could maintain fore-and-aft trim by filling empty tanks with water; therefore, the machinery could be situated aft and the propeller shafts could be shortened. As the problem of trim became resolved in other types of ships, they, too, introduced this feature. Even some passenger liners have the machinery aft, so today the silhouette of a general cargo ship may differ from that of a bulk cargo carrier only in the type and amount of cargo-handling equipment. Even this distinction is disappearing today because of the development of two new types of general cargo carriers: the "roll-on, roll-off" (Ro-Ro) ships, in which cargoes in special containers are passed over ramps through doors in the ships' sides; and container ships, in which standard containers, often filled at factories far from the loading port, are hoisted on board by special loading systems and stacked in cellular holds and on deck (see \Tcontainerization\t). Tankers have meanwhile grown out of all recognition from the 12,000-ton, 15-knot ships built by the British to replace the great number lost during World War II, or the 16,800-ton, 16-knot standard U.S. tankers built at the same time. Ships of 24,900 tons deadweight, called supertankers, were first built in 1949. When the Suez Canal was closed in 1956 and again in 1967, the shortest route for Middle Eastern oil to Europe was blocked, and it became necessary to sail around the Cape of Good Hope. To make this economical, even larger tankers were required. The first to take advantage of the need for these larger tankers were the Japanese shipyards, which were redesigned to build supertankers of 100,000 tons, and then even larger ships of 250,000 to 275,000 tons, known as very large crude carriers (VLCC). The economic success and reasonably safe operation of these enormous ships led to even larger vessels, the ultralarge crude carriers (ULCC) of tonnages up to 400,000, while others up to double that size are in the planning stage. Although economic considerations suggest such huge ships, the safety factor causes concern among many in the shipping world. The supertankers require many kilometers to stop and are not very maneuverable. When routed through narrow and perhaps foggy seaways like the English Channel, they pose a high risk to other shipping, and damage from grounding or collision can result in \Loil spill\ls of enormous proportions. They also share with all tankers, but on a greater scale, the risk of gas explosion in emptied tanks. Among the smaller commercial craft of special design are the tugboats, also called towboats. In relation to their size, these craft use powerful engines, but their very large, slowly rotating propellers are the secret of tugboat thrust. Their seagoing ability varies. Those used for long-distance ocean tows are quite different from the tugs seen pulling barges or maneuvering ships into docks in a port. Fishing boats have evolved into a number of different types according to the kind of sea, type of catch, and necessary length of the voyage (see \Tfishing industry\t). The largest are refrigerated factory ships, which process as well as catch fish. Some Russian whaling ships combine the storage facilities of a large tanker with the capacity to act as a depot ship for a fleet of smaller whale-catchers, and they may even house an amphibious airplane used for whale spotting. New Types of Water Craft Two types of craft that can be said to have now advanced from the status of "boat" to that of "ship" are the hovercraft and the hydrofoil. Examples of each type of about 230 tons are in service. A hovercraft rides above the surface of the water (or land, for that matter) on a cushion of air provided by fans and is propelled by air screws (propellers). The first practical design was made by the British engineer Sir Christopher Cockrell. Under British government sponsorship, the first commercial hovercraft, the 165-ton SRN-4, went into service as a cross-Channel ferry. It has a cruising speed of 55 knots and a maximum speed of 65. It can also run up on a beach and travel over flat or marshy terrain. The hydrofoil has been under development since the early 20th century, but it was not until 1956 that the first hydrofoil went into operation between Sicily and Italy. Two basic types have been developed. In one of these, when a certain forward speed is attained, the boat is lifted clear of the water by hydrofoils that remain submerged. In the other the foils break through the surface. The former is the more stable type; the latter, however, can be faster. Hydrofoils may be driven by a water propeller on a shaft that is sloped downward to the rear or by a water jet ejected astern. Speeds of about 50 knots are usual. John R. Whiting Bibliography: Bathe, Basil W., Seven Centuries of Sea Travel (1972); Blackburn, Graham, The Illustrated Encyclopedia of Ships, Boats, and Vessels (1978); Casson, Lionel, Ships and Seamanship in the Ancient World (1971); Chatterton, E. K., Sailing Ships (1977); Kemp, Peter, The History of Ships (1978) and The Oxford Companion to Ships and the Sea (1976); Phillips-Birt, Douglas, A History of Seamanship (1971); Spratt, H. Philip, Transatlantic Paddle Steamers (1981); United States Coast Guard, Eagle Seamanship: Square Rigger Sailing (1979); Villiers, Alan, Men, Ships, and the Sea (1962; rev. ed., 1973) and The Way of a Ship (1954; repr. 1975); Worcester, G. R., Junks and Sampans of the Yangtze (1971); Tyler, David B., Steam Conquers the Atlantic, (1939; repr. 1972).