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Clark, George Rogers

(Encyclopedia)Clark, George Rogers, 1752–1818, American Revolutionary general, conqueror of the Old Northwest, b. near Charlottesville, Va.; brother of William Clark. A surveyor, he was interested in Western land...

thermodynamics

(Encyclopedia)thermodynamics, branch of science concerned with the nature of heat and its conversion to mechanical, electric, and chemical energy. Historically, it grew out of efforts to construct more efficient he...

guerrilla warfare

(Encyclopedia)guerrilla warfare gərĭlˈə [key] [Span.,=little war], fighting by groups of irregular troops (guerrillas) within areas occupied by the enemy. When guerrillas obey the laws of conventional warfare t...

South, the

(Encyclopedia)South, the, region of the United States embracing the southeastern and south-central parts of the country. Traditionally, all states S of the Mason-Dixon Line and the Ohio River (except West Virginia)...

hagfish

(Encyclopedia)hagfish, primitive, jawless marine fish of the family Myxinidae, of worldwide distribution in cold and temperate waters. Its rudimentary skeleton, of cartilage rather than bone, has a braincase, but n...

Sedna

(Encyclopedia)Sedna, in astronomy, the most distant known large object in the solar system. With a highly eccentric elliptical orbit that ranges from an estimated 76 AU to 937 AU, Sedna also has an extremely long o...

Old Person, Earl

(Encyclopedia) Old Person, Earl,1929-2021, leader of the Blackfeet Nation, b. outside Browning, Mt., Blackfeet names Stu Sapoo ("Cold Wind") and ...

Stirling engine

(Encyclopedia)Stirling engine, an external combustion reciprocating engine having an enclosed working fluid that is alternately compressed and expanded to operate a piston, thus converting heat from a variety of so...

foreign aid

(Encyclopedia)foreign aid, economic, military, technical, and financial assistance given on an international, and usually intergovernmental level. U.S. foreign aid programs have included at least three different ob...

plastic

(Encyclopedia)plastic, any organic material with the ability to flow into a desired shape when heat and pressure are applied to it and to retain the shape when they are withdrawn. The first important plastic, cel...