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Humboldt, Alexander, Freiherr von

(Encyclopedia)Humboldt, Alexander, Freiherr von hŭmˈbōlt, Ger. älĕksänˈdər frīˈhĕr fən ho͝omˈbôlt [key], 1769–1859, German naturalist, inventor, explorer, and author, the most eminent scientist of ...

ignition

(Encyclopedia)CE5 Ignition system ignition, apparatus for igniting a combustible mixture. The German engineer Nikolaus A. Otto, in his first gas engine, used flame ignition; another method was heating a metal t...

occupational disease

(Encyclopedia)occupational disease, illness incurred because of the conditions or environment of employment. Unlike with accidents, some time usually elapses between exposure to the cause and development of symptom...

oceanography

(Encyclopedia)oceanography, study of the seas and oceans. The major divisions of oceanography include the geological study of the ocean floor (see plate tectonics) and features; physical oceanography, which is conc...

skin

(Encyclopedia)CE5 Cross section of skin skin, the flexible tissue (integument) enclosing the body of vertebrate animals. In humans and other mammals, the skin operates a complex organ of numerous structures (so...

Great Plains

(Encyclopedia)Great Plains, extensive grassland region on the continental slope of central North America. They extend from the Canadian provinces of Alberta, Saskatchewan, and Manitoba south through W central Unite...

metamorphism

(Encyclopedia)metamorphism, in geology, process of change in the structure, texture, or composition of rocks caused by agents of heat, deforming pressure, shearing stress, hot, chemically active fluids, or a combin...

nickel

(Encyclopedia)nickel, metallic chemical element; symbol Ni; at. no. 28; at. wt. 58.6934; m.p. about 1,453℃; b.p. about 2,732℃; sp. gr. 8.902 at 25℃; valence 0, +1, +2, +3, or +4. Nickel is a hard, malleable, ...

liquid

(Encyclopedia)liquid, one of the three commonly recognized states in which matter occurs, i.e., that state, as distinguished from solid and gas, in which a substance has a definite volume but no definite shape. T...

cactus

(Encyclopedia)cactus, any plant of the family Cactaceae, a large group of succulents found almost entirely in the New World. A cactus plant is conspicuous for its fleshy green stem, which performs the functions of ...