buoyant apparatus
51Mercury (element) — gold ← mercury → thallium Cd ↑ Hg ↓ Cn …
52Poland — /poh leuhnd/, n. a republic in E central Europe, on the Baltic Sea. 38,700,291; ab. 121,000 sq. mi. (313,400 sq. km). Cap.: Warsaw. Polish, Polska. * * * Poland Introduction Poland Background: Poland is an ancient nation that was conceived around …
53pump — pump1 pumpable, adj. pumpless, adj. pumplike, adj. /pump/, n. 1. an apparatus or machine for raising, driving, exhausting, or compressing fluids or gases by means of a piston, plunger, or set of rotating vanes. 2. Engin., Building Trades. a shore …
54rock — rock1 rockless, adj. rocklike, adj. /rok/, n. 1. a large mass of stone forming a hill, cliff, promontory, or the like. 2. Geol. a. mineral matter of variable composition, consolidated or unconsolidated, assembled in masses or considerable… …
55Rock — /rok/, n. a male given name. * * * I In geology, a naturally occurring and coherent aggregate of minerals. The three major classes of rock igneous, sedimentary, and metamorphic are based on the processes that formed them. These three classes are… …
56social security — 1. (usually caps.) a program of old age, unemployment, health, disability, and survivors insurance maintained by the U.S. federal government through compulsory payments by specific employer and employee groups. 2. the theory or practice of… …
57United States — a republic in the N Western Hemisphere comprising 48 conterminous states, the District of Columbia, and Alaska in North America, and Hawaii in the N Pacific. 267,954,767; conterminous United States, 3,022,387 sq. mi. (7,827,982 sq. km); with… …
58arts, East Asian — Introduction music and visual and performing arts of China, Korea, and Japan. The literatures of these countries are covered in the articles Chinese literature, Korean literature, and Japanese literature. Some studies of East Asia… …
59paracanthopterygian — ▪ fish Introduction any member of the superorder Paracanthopterygii, a predatory, primarily marine group that forms one of about six major branches of the Teleostei (teleost), or bony fishes, the dominant modern aquatic vertebrates.… …
60western Africa, history of — Introduction history of the region from the 11th century to the present. A reasonable body of sources for the writing of western African history begins to be available about AD 1000. Three centuries earlier, the Arabs (Arab) had… …
