diathermy Vdl-o-.thsr-meX Use of high-frequency electric current for deep heating of tissues in physical therapy. Shortwave, ultrasound, and microwave diathermy heat tissues at different depths for different purposes. Low heat warms tissue to ease muscle pain. Higher degrees of diathermy destroy tissue; this is useful in surgery, particularly on the eye or nerves, to coagulate, limit bleeding, and seal off traumatized tissues.
diatom Vdl-o-.tamV Any member of the algal division or phylum Bacil- lariophyta (about 16,000 species), tiny planktonic (see plankton), uni¬ cellular or colonial algae found float¬ ing in all the waters of the earth. The intricate and delicate markings of the silicified cell wall are useful in test¬ ing the resolving power of micro¬ scope lenses. The beautiful
symmetry and design of diatoms jus¬ tify their title “jewels of the sea.”
Among the most important and pro¬ lific sea organisms, diatoms serve directly or indirectly as food for many animals. Diatomaceous earth, composed of fossil diatoms, is used in filters, insulation, abrasives, paints, and varnishes, and as an insecticide.
diatomaceous V.dl-o-to-'ma-shosV earth or kieselguhr Vke-zol- ,gur\ Light-coloured, porous, and friable sedimentary rock composed of the frustrules (silicate cell walls) of diatoms. It is used in industrial filtra¬ tion applications; as a filler or extender in paper, paint, brick, tile, ceram¬ ics, linoleum, plastic, soap, detergent, and other products; in insulation for boilers, blast furnaces, and other high-temperature devices; as a sound insulator; and as a carrier for herbicides and fungicides. The oldest and best-known commercial use is as a very mild abrasive in metal polishes
ERIC GRAVE-PHOTO RESEARCHERS
and toothpaste. Large deposits occur in California, Nevada, Washington, and Oregon; other sources are Denmark, France, Russia, and Algeria.
Diaz Vde-.asV Porfirio (b. Sept. 15, 1830, Oaxaca, Mex.—d. July 2,
1915, Paris, Fr.) Soldier and presi¬ dent of Mexico (1877-80, 1884— 1911). After training for the priesthood, he pursued a military career instead. When peace was restored to Mexico under Benito JuArez, Diaz resigned his command, but he soon became dissatisfied with the government. After leading two revolts, he was elected president in 1877. He succeeded in bolstering the export economy through foreign investment, while leading in the spirit of a caudillo, suppressing oppo¬ sition, rigging elections, and using patronage to win the cooperation of various groups. The Mexican Revolu¬ tion was launched in 1910 to end his dictatorship and reverse his policies. See also Francisco Madero, La Reforma.
Porfirio Diaz.
LIBRARY OF CONGRESS, WASHINGTON, D.C.
Dibdin, Charles (baptized March 4, 1745, Southampton, Hampshire, Eng.—d. July 25, 1814, London) British composer, novelist, and actor. A cathedral chorister, Dibdin began working for a music publisher at age 15 and began his stage career in 1762. His first operetta was The Shepherd’s Artifice (1764). By 1778, when he became exclusive composer for Cov¬ ent Garden, he had produced eight operas, including The Padlock (1768), The Waterman (1774), and The Quaker (1775). He later produced his bal¬ lad opera Liberty Hall. He was author, singer, and accompanist for his celebrated one-man “table entertainments”; most of his popular sea songs were written for these. In all, he wrote about 100 stage works and 1,400 songs. He was one of the most popular British composers of the 18th cen¬ tury.
Dibon \'dl-,ban\ modern DhTban \the-'ban\ Ancient city of Palestine. The capital of Moab, it was located north of the Arnon River in what is now west-central Jordan. Excavations have uncovered the remains of city walls and numerous buildings; pottery found at the site dates from c. 3200 bc to the 7th century ad. One of the most important finds was the Moabite Stone, written in the Moabite alphabet, an important representation of the Phoenician script. Dating from the 9th century bc, it commemorates a victory over the Israelites. See also Moabites.
dice Set of small cubes (each called a die) marked on each face with from one to six spots and used in gambling and in various social games by being shaken and thrown down to come to rest at random on a flat surface. The combined number of the spots on the topmost surface of the tossed dice decides, according to the rules of the game being played, whether the thrower (or “shooter”) wins, loses, or continues to throw. In numerous board games the thrown dice determine the player’s moves. Dice, which may be traced back to prehistory, were in many cultures magical devices used for the casting of lots to divine the future. In the modern era they became associated with the playing of games of chance, including craps.
dickcissel \dik-'si-sol, 'dik-.si-soL American passerine ( Spiza americana, family Fringillidae) bird that eats seeds and breeds in weedy fields of the central U.S. Most dickcissels winter in northern South America, but some stray to the Atlantic coast.
The male, for whose song the species is named, is a streaky brown bird 6.5 in. (16 cm) long, with a black bib on its yellow breast, resembling a min¬ iature MEADOWLARK.
Dickens, Charles (John Huf- fam) (b. Feb. 7, 1812, Portsmouth,
Hampshire, Eng.—d. June 9, 1870,
Gad’s Hill, near Chatham, Kent)
British novelist, generally considered the greatest of the Victorian period.
Dickcissel [Spiza americana)
THASE DANIEL
© 2006 Encyclopaedia Britannica, Inc.
Dickey ► Didot family I 543
The defining moment of Dickens’s life occurred when he was 12 years old. With his father in debtors’ prison, he was withdrawn from school and forced to work in a factory. This deeply affected the sensitive boy. Though he returned to school at 13, his formal education ended at 15. As a young man, he worked as a reporter. His fiction career began with short pieces reprinted as Sketches by “Boz” (1836). He exhibited a great ability to spin a story in an entertaining manner and this quality, combined with the seri¬ alization of his comic novel The Pickwick Papers (1837), made him the most popular English author of his time. The serialization of such works as Oliver Twist (1838) and The Old Curiosity Shop (1841) followed. After a trip to America, he wrote A Christmas Carol (1843) in a few weeks. With Dombey and Son (1848), his novels began to express a heightened uneasiness about the evils of Victorian industrial society, which intensi¬ fied in the semiautobiographical David Copperfield (1850), as well as in Bleak House (1853), Little Dorrit (1857), Great Expectations (1861), and others. A Tale of Two Cities (1859) appeared in the period when he achieved great popularity for his public readings. Dickens’s works are characterized by an encyclopaedic knowledge of London, pathos, a vein of the macabre, a pervasive spirit of benevolence and geniality, inex¬ haustible powers of character creation, an acute ear for characteristic speech, and a highly individual and inventive prose style.
Dickey, James (Lafayette) (b. Feb. 2, 1923, Atlanta, Ga., U.S.—d. Jan. 19, 1997, Columbia, S.C.) U.S. poet, novelist, and critic. Dickey served as a pilot in World War II. His poetry—published in such volumes as Into the Stone (1960), Drowning with Others (1962), Helmets (1964), Buckdancer’s Choice (1965), and The Zodiac (1976)—combines themes of nature mysticism, religion, and history. He became widely known with his powerful novel Deliverance (1970; film, 1972).
Dickinson, Emily (Elizabeth) (b. Dec. 10, 1830, Amherst, Mass., U.S.—d. May 15, 1886, Amherst) U.S. poet. Granddaughter of the cofounder of Amherst College and daughter of a respected lawyer and one-term congressman, Dickinson was educated at Amherst (Mass.) Acad¬ emy and Mount Holyoke Female Seminary. She subsequently spent vir¬ tually all her life, increasingly reclusive, in her family home in Amherst. She began writing in the 1850s; by 1860 she was boldly experimenting with language and prosody, striving for vivid, exact words and epigram¬ matic concision while adhering to the basic quatrains and metres of the Protestant hymn. The subjects of her deceptively simple lyrics, whose depth and intensity contrast with the apparent quiet of her life, include love, death, and nature. Her numerous letters are sometimes equal in art¬ istry to her poems. By 1870 she was dressing only in white and declin¬ ing to see most visitors. Of her 1,775 poems, only seven were published during her lifetime. After posthumous publications (some rather inaccu¬ rate), her reputation and readership grew. Her complete works were pub¬ lished in 1955, and she has since become universally regarded as one of the greatest American poets.