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Ruskin, John

(Encyclopedia)Ruskin, John, 1819–1900, English critic and social theorist. During the mid-19th cent. Ruskin was the virtual dictator of artistic opinion in England, but Ruskin's reputation declined after his deat...

soap

(Encyclopedia)soap, a cleansing agent. It cleanses by lowering the surface tension of water, by emulsifying grease, and by absorbing dirt into the foam. Ancient peoples are believed to have employed wood ashes and ...

Euclid, Greek mathematician

(Encyclopedia)Euclid yo͞oˈklĭd [key], fl. 300 b.c., Greek mathematician. Little is known of his life other than the fact that he taught at Alexandria, being associated with the school that grew up there in the l...

frontier

(Encyclopedia)frontier, in U.S. history, the border area of settlement of Europeans and their descendants; it was vital in the conquest of the land between the Atlantic and the Pacific. The importance of the westwa...

flame

(Encyclopedia)flame, phenomenon associated with the chemical reaction of a gas that has been heated above its kindling temperature with some other gas, usually atmospheric oxygen (see combustion). The heat and ligh...

blood clotting

(Encyclopedia)blood clotting, process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood ve...

Courbet, Gustave

(Encyclopedia)Courbet, Gustave güstävˈ ko͞orbāˈ [key], 1819–77, French painter, b. Ornans. He moved to Paris in 1839 and studied there, learning chiefly by copying masterpieces in the Louvre. An avowed real...

ozone

(Encyclopedia)ozone ōˈzōn [key], an allotropic form of the chemical element oxygen (see allotropy). Pure ozone is an unstable, faintly bluish gas with a characteristic fresh, penetrating odor. The gas has a dens...

snow

(Encyclopedia)CE5 Snow occurs in many different forms. Among the various recognized classes of forms are (A) needles; (B) columns and groups of columns; (C) plates; (D) branched, or dendritic, plates; (E) combin...

torpedo , in naval warfare

(Encyclopedia)torpedo, in naval warfare, a self-propelled submarine projectile loaded with explosives, used for the destruction of enemy ships. Although there were attempts at subsurface warfare in the 16th and 17t...