ANGLE OF REFRACTION 



(also called anaerohiont) . Organisms 



amplitude — 1. The magnitude of the displacement 

 of a wave from a mean value. For a simple 

 harmonic wave, it is the maximum displace- 

 ment from the mean. For more complex wave 

 motion, amplitude is usually taken as one-half 

 the mean distance (or dirt'erence) between maxi- 

 mums and minimums. 



An ocean surface wave has an amplitude equal 

 to the vertical distance from still water level to 

 wave crest, that is, one-half the wave height. 



(5) 



2. In eaigineering usag-e, loosely, the wave 



lieight from crest to trough. ( 61 ) 



3. The semirange of a constituent tide. (50) 

 anadromous — A form of life cycle among fishes 



in which maturity is attained in the ocean, and 

 the adults ascend streams and rivers to spawn 

 in fresh water. Salmon and shad are two ex- 

 amples. 



anaerobe 



for whose life processes a complete or (In some 

 forms) nearly complete absence of oxygen is es- 

 sential. Facultative anaerobes can utilize free 

 oxygen ; obligate anaerobes are poisoned by it. 



anaerobic — Conditions in which oxygen is ex- 

 cluded, and as a result noi'mal life that depends 

 on the presence of oxygen is not possible. Some 

 bacteria can, however, live in these conditions. 

 (32) 



anaerobic sediment — A highly organic sediment 

 ricli in H.,S formed in the absence of free oxygen. 

 Characteristic of some fiords and marine basins 

 where little or no circulation or mixing of the 

 bottom water occurs. 



anaerohiont — See anaerobe. 



anchorage — 1. An area where a ship anchors or 

 may anchor, either because of suitability or 

 designation. 



2. Explosives anchorage — an area set part for 

 anchored ships discharging or receiving explo- 

 sives. 



3. Exposed anchorage — an anchorage that is 

 unprotected from such danger's as weather, sea, 

 or ice. 



• 4. Proliibited anchorage — a section of a har- 

 bor kept free of anchored ships. 



5. Temporary anchorage — a place where ships 

 can anchor only mider favorable conditions and 

 where ships must have power ready to get under 

 way. 



anchorage stone — See anchor stone. 



anchor ice — (also called hottom ice, depth ice, 

 ground ice, Jappered ice, underwater ice). Ice 

 found attached or anchored to the bottom ir- 

 respective of its nature of formation. (74 ) 



anchor stone — (or anchorage stone). A pebble 

 or boulder to wliich marine plants have attached 

 themselves. (2) 



andesite line — The postulated geographic and 

 petrographic boundary between the andesite- 

 dacite-rhyolite rock association of the margin 

 of the Pacific Ocean and the olivine basalt- 



trachyte rock association of the Pacific Ocean 

 basin and its included islands. (2) 



anemometer — The general name for instruments 

 designed to ineasure the speed (or force) of the 

 wind. (5) 



anemone — See sea anemone. 



aneroid — 1. Literally, "not wet," containing no 

 liquid; applied to a kind of barometer which 

 contains no liquid, an aneroid barometer. 



2. See aneroid barometer. 

 (5) 



aneroid barometer — (rarely called holosteric 

 barometer) . An instrument for measuring at- 

 mospheric pressure. It is constructed on the 

 following principles: an aneroid capsule (a thin 

 corrugated hollow disk) is partially evacuated 

 of gas, and is restrained from collapsing by an 

 external or internal spring. The deflection of 

 the spring will be nearly pi'oportional to the 

 difference between the internal and external 

 pressures. Magnification of the spring deflec- 

 tion is obtained both by connecting capsules in 

 series and by mechanical linkages. 



The aneroid barometer is temperature com- 

 pensated at a given pressure level by adjust- 

 ment of the residual gas in the aneroid or by a 

 bimetallic link arrangement. The instrument is 

 subject to uncertainties due to variations in the 

 elastic properties of the spring and capsules, 

 and due to wear in the mechanical linkages. 

 (5) 



angel — A radar echo caused by a physical phe- 

 nomenon not discernible to the eye. 



Studies indicate that a fair portion of angels 

 are caused by strong temperature and/or mois- 

 ture gradients such as might be found near the 

 boundaries of bubbles of especially warm or 

 moist air. They frequently occur in shallow 

 layers at or near temperature inversions witliin 

 the lowest few thousand feet of the atmosphere. 

 (5) 



angle of bank — See angle of roll. 



angle of deviation — The angle through which a 

 ray is bent by refraction. ( 68 ) 



angle of incidence — The angle at which a ray of 

 energy, or an object, impinges upon a surface, 

 measured between the direction of propagation 

 of the energy (or object) and a perpendicular 

 to the surface at the point of impingement, or 

 incidence. See angle of reflection, angle of 

 refraction. (5) 



angle of reflection — The angle at which a re- 

 flected ray of energy leaves a reflecting surface, 

 measured between the direction of the outgoing 

 ray and a perpendicular to the surface at the 

 point of reflection. (5) 



angle of refraction — The angle at which a re- 

 fracted ray of energy leaves the interface at 

 which the refraction occurred, measured be- 

 tween tlie direction of the refracted ray and a 

 perpendicular to the interface at the point of 

 refraction. (5) 



