If the barometer is located at 45° latitude at 

 sea level and its temperature is C, a length in- 

 crement of one baromil will correspond to a pres- 

 sure increment of one millibar. Corrections must 

 be applied at other locations. (24) 



BAROTRAUMA. . A generic term for injury caused by 

 pressure. Although "SQUEEZE" is a colloquialism, 

 it is an excellent descriptive term for all of the 

 phenomena which occur when a rigid closed space 

 within the body or on its surface fails to equalize 

 with external pressure during descent, or is for 

 some reason vented to lower pressure than that act- 

 ing at the depth. (37) 



BAROTROPY . The state of a fluid in which surfaces 

 of constant density (or temperature) are coincident 

 with surfaces of constant pressure; it is the state 

 of zero BAROCLINITY. Mathematically, the equation 

 of barotropy states that the gradients of the den- 

 sity and pressure fields are proportional: 



Vp= gVp 



where P is the density, P the pressure, and yS a 

 function of thermodynamic variables, called the 

 coefficient of barotropy. With the equation of 

 state, this relation determines the spatial dis- 

 tribution of all state parameters once these are 

 specified on any- surface. For a homogeneous at- 

 mosphere, P = 0; for an adiabatic atmosphere, 

 fi - CvJCp Ri: where Cv and Cp are the specific 

 heats at constant volume and pressure, respectively, 

 R the gas constant, and T the Kelvin temperature; 

 for an isothermal atmosphere, = 1/RT. 



It is not necessary that a flAid which is 

 barotropic at the moment will remain so; but the 

 implication that it does often accompanies the 

 assumption of barotropy. In this sense the assump- 

 tion, or a modification thereof, is widely applied 

 in dynamic meteorology. The important consequences 

 are that absolute vorticity is conserved (to the 

 extent that the motion is two dimensional), and 

 that the geos trophic wind has no shear with height. 

 (24) 



BARRANCA. A large rift In piedmont ice or shelf 

 ice. A smaller rift with steep sides is called a 

 donga. (17) 



BARRIER BEACH (OFFSHORE BARRIER) . A bar essential- 

 ly parallel to the shore, the crest of which is 

 above high water. (10) 



BARRIER ICEBERG . See TABULAR ICEBERG. 



BARRIER ISLAND . A wave-built deposit of sand main- 

 ly, raised above sea-level by constructive wave 

 action and separated from the shore by a lagoon. 

 Its height may be increased by dune formation. (27) 



BARRIER LAYER CELL . For ambient light measurements 

 in the upper 50-100 meters a barrier-layer-type 

 cell generally is used. For example, the Weston 

 photronic cell, responds to light wave lengths 

 between 3,000^and 7,500 A with a maximum response 

 around 5,500 A. With the proper detection device 

 this cell has sufficient sensitivity to measure 

 radiation of as little as 10'^ gm cal/cm^/min. (35) 



BARRIER REEF . A reef which roughly parallels land 

 but is some distance offshore, with deeper water 

 adjacent to the land, as contrasted with a FRINGING 

 REEF closely attached to the shore. (17) 



BARYE . The term "barye" is used in some European 

 countries to mean one dyne per square centimeter, 

 or one microbar as defined in American Standard 

 Acoustical Terminology, SI. 1-1960. See MICRO- 

 BAR, (1) 



BASIC FREQUENCY . Any given oscillation can always 

 be considered to be made up of a number of 

 sinusoidal components each having a different 



frequency. In any given instance, that frequency 

 which is considered to be the most important is 

 called the basic frequency of the oscillation. (9) 



BASIN . 1. A depression of the sea floor more or 

 less equidimensional in form. When the length Is 

 much greater than the width, the feature is a 

 TROUGH. (26) 



2. An area in a tidal region in which 

 water can be kept at a desired level by means of 

 a gate. Also called tidal basin. 



3. A relatively small cavity in the bottom- 

 or shore, usually created or enlarged by excavation, 

 large enough to receive one or more vessels for a 

 specific purpose. (27) 



BATHOLITH . A large igneous intrusive mass, having 

 an exposed area greater than 40 square miles and no 

 visible or clearly inferable floor. (27) 



"BATH SPONGE". See SPONGIN. 



BATHYCONDUCTOGRAPH (BC) . 1. A device used to 

 measure the electrical conductivity of sea water 

 at various depths . 



2. The letters, "BC", 

 are also used as an abbreviation in oceanographic 

 work for Bottom Contour. (35) 



BATHYMETER . The Naval Ordnance Test Station 

 developed a device which they call the "bathymeter." 

 This instrument measures temperature, pressure, and 

 sound velocity to depths up to 7 miles. The device 

 is completely transistorized and uses frequency 

 modulation for telemetering. (35) 



BATHYMETRIC . Pertaining to depth measurement. 



BATHYMETRIC CHART . A topographic chart of the bed 

 of a body of water, or a part of it. Generally, 

 bathymetric charts show depths by contour lines 

 and gradient tints. (17) 



BATHYMETRY . The art or science of determining 

 depths of water. (17) 



BATHYSCAPH . Literally means "deep-boat". Refers 

 usually to those small submersibles which are de- 

 signed much more for going to a great depth than 

 for horizontal mobility. 



BATHYSYSTEM . A coined word for a permanent sea 

 floor installation. 



BATHYTHERMOGRAM . The record obtained by a single 

 immersion of a BATHYTHERMOGRAPH. (4) 



BATHYTHERMOGRAPH (BT) . The Bathythermograph is an 

 instrument that determines water temperature as a 

 function of depth. When the BT is lowered into the 

 sea a plot of temperature vs . depth is automatical- 

 ly recorded either on smoked glass by a stylus, or 

 with pen and ink on paper. Mechanical as well as 

 electronic Bathjrthermographs are available. In the 

 mechanical BT the temperature sensing device is a 

 Bourdon tube and the depth finder is a bellows 

 system. In the electronic BT the temperature sens- 

 ing unit is a thermistor while the depth finder is 

 a Bourdon tube activated potentiometer. (30) 



BAY . (1) A recess in the shore or an inlet of a 

 sea or lake between two CAPES or HEADLANDS, not as 

 large as a GULF, but larger than a COVE. (1) 



(2) A portion of the sea which penetrates into 

 the interior of the land . It is usually wider in 

 the middle than at the entrance. It may be similar 

 to a gulf, but smaller. 



(3) A portion of the sea partly surrounded 

 by ice. See BIGHT. (17) 



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