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Sung

(Encyclopedia)Sung so͝ong [key], dynasty of China that ruled 960–1279. It was divided into two periods: Northern Sung (907–1126) with its capital at Kaifeng and Southern Sung (1127–1279) with its capital at ...

advertising

(Encyclopedia)advertising, in general, any openly sponsored offering of goods, services, or ideas through any medium of public communication. At its inception advertising was merely an announcement; for example, en...

Monitor and Merrimack

(Encyclopedia)Monitor and Merrimack, two American warships that fought the first engagement between ironclad ships. When, at the beginning of the Civil War, the Union forces abandoned the Norfolk Navy Yard at Ports...

Gran Chaco

(Encyclopedia)Gran Chaco grän chäˈkō [key] or Chaco, c.250,000 sq mi (647,500 sq km), extensive lowland plain, central South America. It is sparsely populated and is divided among Paraguay, Bolivia, and Argenti...

fugitive slave laws

(Encyclopedia)fugitive slave laws, in U.S. history, the federal acts of 1793 and 1850 providing for the return between states of escaped black slaves. Similar laws existing in both North and South in colonial days ...

communications satellite

(Encyclopedia)communications satellite artificial satellite that functions as part of a global radio-communications network. Echo 1, the first communications satellite, launched in 1960, was an instrumented inflat...

Saint Lawrence Seaway

(Encyclopedia)Saint Lawrence Seaway, international waterway, 2,342 mi (3,769 km) long, consisting of a system of canals, dams, and locks in the St. Lawrence River and connecting channels between the Great Lakes; op...

nuclear weapons

(Encyclopedia)nuclear weapons, weapons of mass destruction powered by atomic, rather than chemical, processes. Nuclear weapons produce large explosions and hazardous radioactive byproducts by means of either nuclea...

Wilkes, Charles

(Encyclopedia)Wilkes, Charles, 1798–1877, American naval officer and explorer, b. New York City, educated by his father. In 1815 he entered the merchant service and received (1818) an appointment as a midshipman....

bearing

(Encyclopedia)bearing, machine part designed to reduce friction between moving parts or to support moving loads. There are two main kinds of bearings: the antifriction type, such as the roller bearing and the ball ...