Amos ' n ' Andy See Freeman and Charles Correll Gosden
a mo site Va-ms-.sfiA Variety of the silicate mineral cummingtonite, which is a source of asbestos. Cummingtonite is an amphibole mineral, an iron and magnesium silicate that occurs in metamorphic rocks in the form of long needlelike, fibrous crystals.
Ampere \a n -'per\, Andre Marie (b. Jan. 22, 1775, Lyon, France—d. June 10, 1836, Marseille) French physicist, founder of the science of electromagnetism. A prodigy who mastered the entire known field of mathematics by age 12, he became a professor of physics, chemistry, and mathematics. He formulated a law of electromagnetism, called Ampere's law, that describes the magnetic force between two electric currents. An instrument he devised to measure the flow of electricity was later refined as the galvanometer. His chief published work was Memoir on the Math¬ ematical Theory of Electrodynamic Phenomena (1827). The ampere (A) unit of electric current was named for him.
Ampere's law Law of electromagnetism that describes mathematically the magnetic force between two electric currents. It was named after A.-M. Ampere, who discovered that such forces exist. If two currents flow in the same direction, the force between the two wires is attractive; if they flow
in opposite directions, the force is repulsive. In each case, the force is directly proportional to the currents.
amphetamine Vam-'fe-to-.menX Organic compound, prototype of a class of synthetic amphetamine drugs (e.g., Benzedrine, Dexedrine, meth- amphetamine), that stimulates the central nervous system. It was first syn¬ thesized in 1887. Amphetamines cause wakefulness, euphoria, decreased fatigue, and increased ability to concentrate. Since they dull the appetite, they have been used for weight reduction. Often called “speed,” they are used (often illicitly) to stay awake. In children with attention deficit (hyperactivity) disorder, they have a calming effect, helping them con¬ centrate. Undesirable effects include overstimulation, with paranoia, rest¬ lessness, insomnia, tremor, and irritability, and a deep depression when the drug wears off. This, along with rapid development of tolerance requir¬ ing increased doses, can lead to drug addiction.
amphibian Any member of a class (Amphibia) of cold-blooded verte¬ brate animals that includes more than 4,400 species in three groups: frogs and toads (order Anura), salamanders (order Caudata), and caecilians (order Apoda). Probably evolved from certain fish species of the Early Devonian period (417-391 million years ago), amphibians were the first vertebrates to move from an aquatic environment to land. Most species have an aquatic larval, or tadpole, stage that metamorphoses into a terrestrial adult, but a few species spend their entire life in water. Amphibians are found worldwide, the majority in the tropics.
amphibious warfare Military operations directed against hostile shores and characterized by attacks launched from the sea by naval and landing forces. It has been conducted since ancient times. The Greeks attacking Troy (1200 bc) had to make a shore landing, as did the Persian invaders of Greece prior to the Battle of Marathon (490 bc). The British- led landings at Gallipoli (1915) were the main amphibious assault in World War I. The Allies of World War II found amphibious tactics essential in the island-hopping Pacific campaign and in the famous D-Day of the Normandy campaign, which still ranks as the greatest amphibious assault in history. Amphibious warfare’s greatest advantage is its mobility and flexibility; its greatest limitation is that the attacker must start from noth¬ ing to build up strength ashore. Modern amphibious forces attempt to overcome this by fielding larger and more efficient landing vessels and also by using helicopters and short-takeoff and -landing airplanes to deploy troops beyond the hostile shore.
amphibole Vam-fs-.boL Any of a group of common rock-forming hydrous silicate minerals. Amphiboles occur in many igneous rocks as minor and major constituents and form the major component in many gneisses and schists. Some highly fibrous forms are collectively called ASBESTOS.
amphibole asbestos Collective term for three highly fibrous (asbestiform) varieties of amphibole: crocidolite, amosite, and actinolite. All have long, silky to splintery fibres with appreciable tensile strength and are of economic importance as asbestos.
amphibolite Vam-'fi-bo-.llA Igneous or metamorphic rock composed largely or dominantly of amphibole minerals. For igneous rocks, the term homblendite is usually used and is more restrictive; hornblende is the most common amphibole. Metamorphic amphibolites are more widespread and variable than igneous ones. Typically, they are medium- to coarse-grained and are composed of hornblende and plagioclase. Basic igneous rocks such as basalts and gabbros (see acid and basic rocks) can be the parent rocks of amphibolite.
amphibolite facies \'fa-shez\ One of the major divisions of the min¬ eral facies classification of metamorphic rocks, encompassing rocks that formed under conditions of moderate to high temperatures (950°F, or 500°C, maximum) and pressures. Less-intense temperatures and pressures form rocks of the epidote-amphiboute facies, and more-intense temperatures and pressures form rocks of the granulite facies. Amphibole, diopside, epi- dote, plagioclase, certain types of garnet, and wollastonite are minerals typically found in amphibolite facies rocks. They are widely distributed in Precambrian gneisses and probably formed in the deeper parts of folded mountain belts.
Amphion and Zethus \'am-fe-9n... , ze-th3s\ In Greek mythology, twin sons of Zeus by the mortal Antiope. As infants the two were left to die on Mount Cithaeron, but were found and raised by a shepherd. Amphion grew up to become a great musician and singer, while Zethus became a hunter and herdsman. According to legend, they built the city of Thebes
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64 I amphioxus ► amygdule
after the stone blocks arranged themselves into walls at the sound of Amphion’s lyre. Amphion became king of Thebes, and he married Niobe, with whom he had six sons and six daughters. When their children were killed by the gods, he committed suicide.
amphioxus \,am-fe-'ak-s3s\ or lancelet Vlan-sldtX Any of certain small marine chordates (invertebrate subphylum Cephalochordata) found widely on tropical and subtropical coasts and less commonly in temper¬ ate waters. Seldom more than 3 in. (8 cm) long, they resemble small, slender fishes without eyes or a definite head. They are grouped in sev¬ eral species in two genera (Branchiostoma or Amphioxus, and Epigon- ichthyes or Asymmetron). They spend much of their time buried in gravel or mud on the ocean bottom, though they are able to swim, and feed by filtering food particles from water passing through their gill slits. They have no brain or distinct heart.
Amphipolis \am-'fi-p3-l3s\ Ancient city, eastern Macedonia, near the mouth of the Struma River. Amphipolis was a strategic transportation cen¬ tre, controlling the bridge over the river and the route from northern Greece to the Dardanelles. Colonized by Athens in 437 bc, it was taken by Sparta in 424 bc. It soon received its independence, only to be taken by Philip II of Macedon in 358 bc. Later, under Roman rule, it was the headquarters of the Roman governor of Macedonia.
amphitheater Freestanding, open-air round or oval structure with a central arena and tiers of concentric seats. The amphitheater originated in ancient Italy (Etruria and Campania) and reflects the entertainment forms popular there, including gladiatorial games and contests of animals with one another or of men with animals. The earliest extant amphitheater is one built at Pompeii (c. 80 bc). Examples survive throughout the former prov¬ inces of the Roman empire, the most famous being Rome’s Colosseum.