ship of the line, large, square-rigged warship, carrying from 70 to 140 guns on two or more completely armed gun decks. In the great naval wars of the 17th, 18th, and early 19th cent., ships of the line were the largest naval units employed. They passed from use with the advent of the ironclad and the battleship. One of the few remaining examples of a ship of the line is Lord Nelson's flagship, the H.M.S. Victory, which has been preserved at Portsmouth, England.

ship, large craft in which persons and goods may be conveyed on water. In the U.S. Navy the term boat refers to any vessel that is small enough to be hoisted aboard a ship, and ship is used for any larger vessel; all submarines, no matter what size, are designated as boats, and ship-sized vessels are often referred to colloquially as boats (e.g. steamboats).

Seagoing vessels large enough to be called ships were used in ancient times by the Egyptians, Cretans, Greeks, Phoenicians, Romans, and Chinese. Ancient ships were propelled by oars or by sails or by both. They were of different types for different functions. Heavy, slow ships with round bottoms were used to transport grain, while slim-keeled ships such as the trireme were used for warfare (see galley). In the Middle Ages Viking ships, propelled by both oars and sails, carried Leif Eriksson to America; their structure is well known from such evidences as the Gokstad ship (unearthed in 1880), which is 80 ft (24.4 m) long, 16 ft 6 in. (5 m) wide, and 6 ft 10 in. (2.1 m) deep.

The introduction of the mariner's compass, the sternpost rudder, and the lateen sail made possible the transoceanic voyages of the Portuguese who rounded Africa and of Columbus and other explorers of the New World, giving new impetus to the building and navigation of ships. Many sturdy and refined types of wooden sailing vessels up to three hundred feet in length were developed. Men-of-war included the ship of the line, the frigate, and the corvette. Differing especially in such details as number and position of masts, with sails either square-rigged or fore-and-aft, ships were differentiated into such types as brig, clipper, and schooner. Building wooden ships became an important industry, especially in Britain and the United States.

The success of Fulton's Clermont on the Hudson River (1807) prepared the way for the superseding of sailing ships by steamships (see steamship), and later in the 19th cent. steel began to replace wood as material for shipbuilding. Steel ships can be made much larger than wooden ships. The steam engine was followed by the steam turbine, which actuated the propeller directly or through gear mechanisms. Both methods of power production underwent many improvements through the years before the diesel engine came (1902-3) into maritime use. In some ships, diesel engines are now used to generate electricity, which is used to power propeller motors. In the 1950s nuclear power was introduced in military vessels and icebreakers; modern nuclear submarines can travel submerged for months at a time (see nuclear energy).

Modern freight ships are equipped with powerful machines for handling cargo; and, although jet transportation led to the demise of the great ocean liners, cruise ships continue to be built, providing the luxuries of the finest hotels. The pivotal vessels of modern warfare are the aircraft carrier and the submarine; other warships important in recent times include the battleship, cruiser, and destroyer.

Welland Ship Canal, 27.6 mi (44.4 km) long, SE Ont., Canada, connecting Lake Ontario with Lake Erie and bypassing Niagara Falls. Built between 1914 and 1932 by Canada to replace a canal opened in 1829, it can accommodate (minimum depth 27 ft/8 m) the largest lake ships. Its eight locks overcome a 326-ft (99-m) difference in level between the lakes. The Lake Ontario entrance is near Port Dalhousie; the Lake Erie entrance is at Port Colborne. It is part of the St. Lawrence Seaway system.

Manchester Ship Canal, 35.5 mi (57 km) long with a minimum depth of 28 ft (8.5 m), connecting Manchester, W England, with the Mersey estuary at Eastham, above Birkenhead. Begun in 1887, it was opened in 1894 and changed Manchester from a river port to a seaport.

Chicago Sanitary and Ship Canal: see Chicago, river.

Fast naval vessel smaller than a frigate. In the 18th–19th century corvettes were three-masted ships with square rigging and carried about 20 guns on the top deck. Often used to send dispatches within a battle fleet, they also escorted merchant ships. Early U.S. corvettes won distinction in the War of 1812. They disappeared as a class after the shift to steam power in the mid-19th century, but in World War II the term was applied to small armed vessels that served as escorts for convoys. Modern corvettes, usually displacing 500–1,000 tons (454–900 metric tons) and armed with missiles, torpedoes, and machine guns, perform antisubmarine, antiaircraft, and coastal-patrol duties in small navies.

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Type of sailing warship, the principal vessel of the West's great navies from the mid-17th to the mid-19th century. It evolved from a tactic in naval warfare known as the line of battle, in which two opposing columns of ships maneuvered to fire their guns broadside against each other. Since the largest ships carrying the biggest guns usually won these battles, this led to the construction of more big line-of-battle ships, or ships of the line. These three-masted ships were often 200 ft (60 m) long, displaced 1,200–2,000 tons (1,100–1,800 metric tons), and had crews of 600–800 men; they usually had 60–110 cannons and other guns arranged along three decks. They eventually gave way to the steam-powered battleship.

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English tax levied by the crown on coastal cities for naval defense in time of war. First levied in medieval times, the tax required payment in the form of a number of warships or their equivalent in money. It was revived in 1634 by Charles I to raise extra revenue. He issued six annual writs (1634–39) that extended the imposition to inland towns and sought to establish it as a permanent tax. Its enforcement aroused widespread opposition and added to the discontent leading to the English Civil Wars. In 1641 the tax was declared illegal by Parliament.

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Large floating vessel capable of crossing open waters. The term formerly was applied to sailing vessels with three or more masts; today it usually denotes a vessel of more than 500 tons' (450 metric tons') displacement. The largest ships today are enormous oil tankers, some of which are 500,000 tons (450,000 metric tons) deadweight. Other specialized ships (containerships) carry general freight in standardized containers that can be easily loaded, unloaded, and transferred. Seealso battleship, brig, clipper ship, corvette, dhow, frigate, junk, longship, ocean liner, schooner, yacht.

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Classic sailing ship of the 19th century, renowned for its beauty, grace, and speed. Apparently originating with the small, swift coastal packet known as the Baltimore clipper, the true clipper evolved first in the U.S. (circa 1833) and later in Britain. It was a long, slim, graceful vessel with a projecting bow, a streamlined hull, and an exceptionally large spread of sail on three tall masts. Clippers carried tea from China and goldminers to California. Famous clippers included the American Flying Cloud and the British Cutty Sark. Though much faster than the early steamships (already in use when the clipper appeared), they were eventually outrun by improved steamship models and largely disappeared from commercial use in the 1870s.

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