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Olympiad

(Encyclopedia)Olympiad, unit of a chronological era of ancient Greece, a four-year period, each one beginning with the Olympic games. Timaeus (c.356–c.260 b.c.) of Sicily was the first to use, as a check on chron...

Oroville Dam

(Encyclopedia)Oroville Dam, 770 ft (235 m) high and 7,600 ft (2,317 m) long, on the Feather River, N Calif., near the city of Oroville. The highest dam in the United States and the largest unit of the Feather River...

Yakima, river, United States

(Encyclopedia)Yakima yăkˈəmô, –mə [key], river, 203 mi (327 km) long, rising in the Cascade Range, central Wash., and flowing SE past Yakima to the Columbia River near Kennewick. The U.S. Bureau of Reclamati...

vernier

(Encyclopedia)vernier vûrˈnēr [key], auxiliary scale, either straight or an arc of a circle, designed to slide along a fixed scale. Its unit divisions, usually smaller than those on the fixed scale, permit a far...

turbine

(Encyclopedia)CE5 Types of turbines turbine, rotary engine that uses a continuous stream of fluid (gas or liquid) to turn a shaft that can drive machinery. A water, or hydraulic, turbine is used to drive electr...

dissociation

(Encyclopedia)dissociation, in chemistry, separation of a substance into atoms or ions. Thermal dissociation occurs at high temperatures. For example, hydrogen molecules (H2) dissociate into atoms (H) at very high ...

South Pass

(Encyclopedia)South Pass, broad, level valley (alt. c.7,550 ft/2,301 m), SW Wyo., cutting across the Rocky Mts. It was used by trappers and explorers before Jedediah Smith inaugurated its use as a route for settler...

barn

(Encyclopedia)barn, abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleus for collisions leading to nuclear reactions; it is equal to 10−24 square centimeters. The ...

charter

(Encyclopedia)charter, document granting certain rights, powers, or functions. It may be issued by the sovereign body of a state to a local governing body, university, or other corporation or by the constituted aut...

Ohm, Georg Simon

(Encyclopedia)Ohm, Georg Simon gāˈôrkh zēˈmôn ōm [key], 1787–1854, German physicist. He was professor at Munich from 1852. His study of electric current led to his formulation of the law now known as Ohm's...