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magnesium

(Encyclopedia)magnesium măgnēˈzēəm, –zhəm [key], metallic chemical element; symbol Mg; at. no. 12; at. wt. 24.3050; m.p. about 648.8℃; b.p. about 1,090℃; sp. gr. 1.738 at 20℃; valence +2. In 1808, Sir...

steamship

(Encyclopedia)steamship, watercraft propelled by a steam engine or a steam turbine. Despite such innovations as turbo-electric drive, which converts steam energy into rotational power for turning the propeller...

environmentalism

(Encyclopedia)environmentalism, movement to protect the quality and continuity of life through conservation of natural resources, prevention of pollution, and control of land use. The philosophical foundations for ...

9/11

(Encyclopedia)9/11, the terrorist attacks on Sept. 11, 2001, in the United States, and the associated events and impact of those attacks. The attacks, which were carried out by agents of Al Qaeda (a militant Islami...

Huang He

(Encyclopedia)Huang He, Hwang Ho both: hwängˈ ho͝oˈ [key], or Yellow River, great river of N China, c.3,000 mi (4,830 km) long, rising in the twin lakes Gyaring and Ngoring in the Kunlun Mts., NW Qinghai prov....

Nicholas II, czar of Russia

(Encyclopedia)Nicholas II, 1868–1918, last czar of Russia (1894–1917), son of Alexander III and Maria Feodorovna. Discontent at home grew, the army tired of war, the food situation deteriorated, the governme...

Volga

(Encyclopedia)Volga vŏlˈgə, Rus. vôlˈgə [key], river, c.2,300 mi (3,700 km) long, central and E European Russia. It is the longest river of Europe and the principal waterway of Russia, being navigable (with l...

Tolstoy, Leo, Count

(Encyclopedia)Tolstoy, Leo, Count, Rus. Lev Nikolayevich Tolstoi (lyĕf), 1828–1910, Russian novelist and philosopher, considered one of the world's greatest writers. About 1876 the doubts that had beset Tols...

seaweed

(Encyclopedia)seaweed, name commonly used for the multicellular marine algae. Simpler forms, consisting of one cell (e.g., the diatom) or of a few cells, are not generally called seaweeds; these tiny plants help to...

infrared astronomy

(Encyclopedia)infrared astronomy, study of celestial objects by means of the infrared radiation they emit, in the wavelength range from about 1 micrometer to about 1 millimeter. All objects, from trees and building...