frost or hoarfrost, ice formed by the condensation of atmospheric water vapor on a surface when the temperature of the surface is below 32°F; (0°C;). In the formation of frost, a gas (water vapor) is changed directly to a solid (see dew). Frost often appears as a light feathery deposit of ice, often of a curious and delicate pattern. The dates on which killing frosts (frost destructive to vegetation and staple agricultural products) occur vary considerably. Maps showing the growing season and the probable date of occurrence of frost may be obtained from the U.S. National Weather Service. The Weather Service stations issue warnings when frost is likely to occur; such warnings are broadcast by radio and are telegraphed or telephoned to farmers and fruitgrowers, who may protect their crops accordingly. Methods of protection vary: small flower beds and vegetable gardens are commonly protected by a screen or cloth that prevents excessive radiation from the earth and from the plants; in orchards, especially in California and Florida, simple oil-burning stoves or smudge pots placed at intervals throughout an orchard are used to heat and circulate the air sufficiently to prevent frost. Valleys are more subject to frosts than slopes, since cold air "slides" downhill and settles in depressions; orchards and citrus fruit groves are usually planted on slopes. Other factors in the occurrence of frost are altitude, latitude, proximity to large bodies of water, and other determinants of temperature. Frost, an element of climate, is an important agent of erosion. Frost heaving, an upthrust of ground caused by freezing, is a factor of consideration in engineering construction, especially in highway foundations. Frost is also a factor in the layer by layer mechanical weathering (exfoliation) of many types of rock masses. In England the word frost denotes freezing weather and degrees of frost means the number of degrees that the temperature falls below the freezing point.

Kennan, George Frost, 1904-2005, U.S. diplomat and historian, b. Milwaukee, Wis., grad. Princeton, 1925. Among the most influential Americans in the Foreign Service in the 20th cent., he served from 1927 in various diplomatic posts in Europe, including Geneva, Hamburg, Riga, Berlin, Prague, Lisbon, and Moscow. From the last he sent his "Long Telegram" (1946), which with his 1947 Foreign Policy article (published under the pseudonym X) was pivotal in the establishment of the cold war U.S. policy of Soviet "containment."

In 1947 he became chairman of the policy-planning staff of the Dept. of State, and contributed to the development of the Marshall Plan. He also was influential in the development of what became the Central Intelligence Agency's clandestine service. Later (1949-50) he was one of the chief advisers to Secretary of State Dean Acheson, but increasingly he disagreed with those in the government who emphasized the military aspects of containment. Kennan was appointed ambassador to the USSR in 1952, but was recalled at the demand of the Soviet government because of comments he made on the isolation of diplomats in Moscow and the campaign that Soviet propagandists were conducting against the United States.

Retiring from the diplomatic service in 1953, he joined the Institute for Advanced Study at Princeton, N.J., and from 1956 until 1974 was professor at its school of historical studies. In the late 1950s he became an advocate of withdrawal of U.S. forces from Western Europe and of Soviet forces from the satellite countries. From 1961 to 1963 he served as U.S. ambassador to Yugoslavia, and in the mid-1960s he opposed U.S. involvement in Vietnam, regarding the conflict there as peripheral to U.S. interests. His more than 20 noteworthy books include American Diplomacy, 1900-1950 (1951), Soviet-American Relations, 1917-1920 (2 vol., 1956-58; Vol. I, Pulitzer Prize), Russia and the West under Lenin and Stalin (1961), Nuclear Delusion (1982), and At a Century's Ending (1996).

Frost, Robert, 1874-1963, American poet, b. San Francisco. Perhaps the most popular and beloved of 20th-century American poets, Frost wrote of the character, people, and landscape of New England. He was taken to Lawrence, Mass., his family's home for generations, at the age of 10. After studying briefly at Dartmouth, he worked as a bobbin boy in a cotton mill, as a cobbler, a schoolteacher, and a journalist; he later entered Harvard but left after two years to try farming. In 1912 he went to England, where he received his first acclaim as a poet. After the publication of A Boy's Will (1913) and North of Boston (1914), he returned to the United States, settling on a farm near Franconia, N.H. Frost taught and lectured at several universities, including Amherst, Harvard, and the Univ. of Michigan. In later life he was accorded many honors; he made several goodwill trips for the U.S. State Dept., and in 1961 he recited his poem "The Gift Outright" at the inauguration of President John F. Kennedy.

Among Frost's volumes of poetry are New Hampshire (1923), West-running Brook (1928), Collected Poems (1930), A Further Range (1936), A Witness Tree (1942), Steeple Bush (1947), and In the Clearing (1962). A Masque of Reason (1945) and A Masque of Mercy (1947) were blank verse plays. Although his work is rooted in the New England landscape, Frost was no mere regional poet. The careful local observations and homely details of his poems often have deep symbolic, even metaphysical, significance. His poems are concerned with human tragedies and fears, his reaction to the complexities of life, and his ultimate acceptance of his burdens. Frost was awarded the Pulitzer Prize for poetry in 1924, 1931, 1937, and 1943. Frost's critical reputation has recently rebounded after a period when his poetry was often criticized for being old-fashioned.

Frost, Arthur Burdett, 1851-1928, American illustrator and cartoonist, b. Philadelphia; pupil of Thomas Eakins at the Pennsylvania Academy of the Fine Arts. He worked chiefly in New York City and became one of the most popular illustrators of his time. His most characteristic drawings portrayed various aspects of American rural life, but he is best known for his illustrations of Joel Chandler Harris's "Uncle Remus" stories.

Atmospheric moisture that crystallizes directly on the ground and on exposed objects. The term also refers to the occurrence of subfreezing temperatures that affect plants and crops. Frost crystals, sometimes called hoarfrost in the aggregate, form when water vapour in the atmosphere passes into the ice-crystal phase without going through the intermediate liquid phase. Frost forms under conditions that would form dew if the temperature were above freezing. In agriculture, frost refers to the freezing of the water in plant cells, which causes the cells to burst and thereby destroys the plant.

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(born March 26, 1874, San Francisco, Calif., U.S.—died Jan. 29, 1963, Boston, Mass.) U.S. poet. Frost's family moved to New England early in his life. After stints at Dartmouth College and Harvard University and a difficult period as a teacher and farmer, he moved to England and published his first collections, A Boy's Will (1913) and North of Boston (1914). At the outbreak of war he returned to New England. He closely observed rural life and in his poetry endowed it with universal, even metaphysical, meaning, using colloquial language, familiar rhythms, and common symbols to express both its pastoral ideals and its dark complexities. His collections include New Hampshire (1923, Pulitzer Prize), Collected Poems (1930, Pulitzer Prize), A Further Range (1936, Pulitzer Prize), and A Witness Tree (1942, Pulitzer Prize). He was unique among American poets of the 20th century in simultaneously achieving wide popularity and deep critical admiration. Many of his poems, including “Stopping by Woods on a Snowy Evening,” “Birches,” “The Death of the Hired Man,” “Dust of Snow,” “Fire and Ice,” and “Home Burial,” are widely anthologized.

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(born March 26, 1874, San Francisco, Calif., U.S.—died Jan. 29, 1963, Boston, Mass.) U.S. poet. Frost's family moved to New England early in his life. After stints at Dartmouth College and Harvard University and a difficult period as a teacher and farmer, he moved to England and published his first collections, A Boy's Will (1913) and North of Boston (1914). At the outbreak of war he returned to New England. He closely observed rural life and in his poetry endowed it with universal, even metaphysical, meaning, using colloquial language, familiar rhythms, and common symbols to express both its pastoral ideals and its dark complexities. His collections include New Hampshire (1923, Pulitzer Prize), Collected Poems (1930, Pulitzer Prize), A Further Range (1936, Pulitzer Prize), and A Witness Tree (1942, Pulitzer Prize). He was unique among American poets of the 20th century in simultaneously achieving wide popularity and deep critical admiration. Many of his poems, including “Stopping by Woods on a Snowy Evening,” “Birches,” “The Death of the Hired Man,” “Dust of Snow,” “Fire and Ice,” and “Home Burial,” are widely anthologized.

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(born Feb. 16, 1904, Milwaukee, Wis., U.S.—died March 17, 2005, Princeton, N.J.) U.S. diplomat and historian. After graduating from Princeton University in 1925, he entered the U.S. foreign service, studied Russian language and culture at the University of Berlin (1929–31), and was assigned to the U.S. embassy in Moscow (1933–35). He served in Vienna, Prague, Berlin, and Lisbon, returning to Moscow during and after World War II. His concept of containment was presented in a highly influential article, signed “X,” that appeared in Foreign Affairs magazine in July 1947. Kennan questioned the wisdom of conciliatory U.S. policy toward the Soviet Union, which he considered appeasement, and advocated instead U.S. counterpressure wherever the Soviets threatened to expand; this approach became the basis of U.S. policy toward the Soviet Union during the first decades of the Cold War. After brief service as an adviser to the State Department, he joined the Institute for Advanced Study at Princeton as professor of historical studies (1956–74); his tenure there was interrupted by a stint as U.S. ambassador to Yugoslavia (1961–63). He won simultaneous Pulitzer Prizes and National Book Awards for Russia Leaves the War (1956) and Memoirs, 1925–50 (1967).

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(born Feb. 16, 1904, Milwaukee, Wis., U.S.—died March 17, 2005, Princeton, N.J.) U.S. diplomat and historian. After graduating from Princeton University in 1925, he entered the U.S. foreign service, studied Russian language and culture at the University of Berlin (1929–31), and was assigned to the U.S. embassy in Moscow (1933–35). He served in Vienna, Prague, Berlin, and Lisbon, returning to Moscow during and after World War II. His concept of containment was presented in a highly influential article, signed “X,” that appeared in Foreign Affairs magazine in July 1947. Kennan questioned the wisdom of conciliatory U.S. policy toward the Soviet Union, which he considered appeasement, and advocated instead U.S. counterpressure wherever the Soviets threatened to expand; this approach became the basis of U.S. policy toward the Soviet Union during the first decades of the Cold War. After brief service as an adviser to the State Department, he joined the Institute for Advanced Study at Princeton as professor of historical studies (1956–74); his tenure there was interrupted by a stint as U.S. ambassador to Yugoslavia (1961–63). He won simultaneous Pulitzer Prizes and National Book Awards for Russia Leaves the War (1956) and Memoirs, 1925–50 (1967).

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