BOA-MILS . Broad Ocean Area-Missile Impact Locating 

 System. 



BOD . Biological Oxygen Demand. 



BOLD COAST . A prominent land mass that rises steep- 

 ly from the sea. (11) 



BOOMERANG SEDIMEOT' CORER . This (FREE INSTRUMENT 

 type) device can be dropped over the side of a 

 moving ship where it vd.ll sink rapidly to the ocean 

 floor, take a core of sediment, -release ballast and 

 automatically return to the surface for retrieval. 

 It is designed for nighttime recovery. (35) 



BORA . A cold, northerly wind blowing from the 

 Hungarian basin into the Adriatic Sea. (17) 



BORAS CO . A thunderstorm or violent squall, es- 

 pecially in the Mediterranean. (17) 



BORE . A very rapid rise of the tide in which the 

 advancing water presents an abrupt front of con- 

 siderable height. In shallow estuaries where the 

 range of tide is large, the high water is propa- 

 gated inward faster than the low water because of 

 the greater depth at high water. If the high water 

 overtakes the low water, an abrupt front is pre- 

 sented with the high-water crest finally falling 

 forward as the tide continues to advance. Also 

 called eager, mascaret, and pororoca. (14) 



BORING . Forcing a vessel under power through ice, 

 by breaking a lead. (17) 



BOTTOM . The ground under a body of water. The 

 terms bed, floor, and bottom have nearly the same 

 meaning, but bed refers more specifically to the 

 whole hollowed area supporting a body of water, 

 floor refers to the essentially horizontal surface 

 constituting the principal level of the ground 

 under a body of water, and bottom refers to any 

 ground covered with water. (17) 



BOTTOM ICE . Ice formed on the bed of a river, lake, 

 or very shallow sea irrespective of its nature of 

 formation. (25) 



BOTTOM ICE (ANCHOR ICE) ■ In shoal water and 

 streams particularly where motion is sufficient 

 to cause thorough mixing, freezing temperatures 

 may extend from the surface to the bottom. When 

 this occurs, ice crystals may form at any depth. 

 Because of their decreased density, they tend to 

 rise to the surface, unless they form at the bottom 

 and attach themselves there. This is called bottom 

 ice or anchor ice and continues to grow as addi- 

 tional ice freezes to that already formed. (12) 



BOTTOM REVERBERATION. See REVERATION 



BOTTOM WATER . The water mass at the deepest part 

 of the water column. It is the densest water that 

 is permitted to occupy that position by the region- 

 al topography. In the case of a BASIN, bottom water 

 may be formed locally, or It may represent the den- 

 sest water that has existed at SILL DEPTH in the 

 recent past. (24) 



BOUGUER ANOMALY . A method of stating the Isostatic 

 anomaly, derived from gravity observations. It al- 

 lows for height above sea-level and the visible ex- 

 cess or deficit of mass. It is called after Bouguer, 

 who first noticed that the Andes did not disturb 

 gravity as much as their mass would suggest. (27) 



change causes an increase in the radius of curva- 

 ture of the tube. The curvature may then be mea- 

 sured by the travel of the tip of the tube. The 

 Bourdon-tube barometer consists of an evacuated 

 Bourdon tube and operates In a similar manner. In 

 both cases the curvature is a measure of the differ- 

 ence between the pressure inside the tube and that 

 outside. (24) 



BOW AND BEAM BEARINGS . Successive relative bear- 

 ings (right or left) of 45° and 90° taken on a 

 fixed object to obtain a running fix. The length 

 of the run between such bearings is equal to the 

 distance of the craft from the object at the time 

 the object is broad on the beam, neglecting current. 

 The 45° bearing is also called a fourpolnt bearing. 

 (17) V 



BOWEN RATIO . At a water surface, the ratio of the 

 energy flux upward as sensible heat to the energy 

 flux used In evaporation. The Bowen ratio is high- 

 ly variable and is sometimes negative. It has been 

 estimated that an average value for the ocean sur- 

 face is about 40.1. (24) 



BOX GAGE . A tide gage that is operated by a float 

 in a long vertical box to which the tide is admit- 

 ted through an opening in the bottom. In the orig- 

 inal type of box gage the float supported a gradu- 

 ated rod which rose and fell with the tide, the 

 height of the tide being read on the rod at a point 

 corresponding to a fixed reading mark. When the 

 rod was graduated with numbers Increasing toward 

 the float the gage readings Increased with the ris- 

 ing tide, but when the rod was graduated from zero 

 upward the gage readings Increased with the falling 

 tide. (14) 



BOXING THE COMPASS . Naming the points and quarter 

 points of the compass in order clockwise around the 

 circle, beginning with north. (24) 



BOYLE'S LAW . States that at a constant temperature 

 the volume of a gas varies Inversely as the abso- 

 lute pressure while the density varies directly as 

 the pressure. (That is, if the pressure on a gas is 

 doubled the density is also doubled, but the volume 

 is decreased to 1/2 of the original volume.) (37) 



BRACKISH WATER . Water in which salinity values 

 range from approximately 0.50 to 17.00 parts per 

 thousand. (15) 



BRADYCARDIA . A slowing of the heart rate that 

 takes place in all diving mammals including man. 



BRANCHIAL . Referring to gills. (19) 



BRASH . See BRASH ICE. 



BRASH ICE . Small fragments of sea or river ice 

 less than 6 feet in diameter. (15) 



BRAVE WEST WINDS . A nautical term for the strong 

 and rather persistent westerly winds over the 

 oceans in temperate latitudes. 



They occur between latitudes 40° and 65 in 

 the northern hemisphere and 35° to 65° in the 

 southern hemisphere, where they are more regular 

 and are strongest between 40 and 50 S (roaring 

 forties). They are associated with the strong pres- 

 sure gradient on the equatorial side of the fre- 

 quent depressions passing eastward in sub-polar tem- 

 perate latitudes; hence they fluctuate mainly be- 

 tween southwest and northwest. (24) 



BOUNDARY WAVES . See INTERNAL WAVES. 



BOURDON TUBE . A closed curved tube of elliptical 

 cross-section used in some thermometers and barom- 

 eters. The Bourdon-tube thermometer consists of a 

 Bourdon tube which is completely filled with liquid. 

 The expansion of the liquid due to a temperature 



BRAZIL CURRENT . A South Atlantic Ocean current 

 flowing southward and southwestward along the south- 



BREAK-DOWN VOLTAGE . The voltage at which an insu- 

 lator or dielectric ruptures; or the voltage at 

 which ionization and conduction begin in a gas or 

 vapor. (36) 



16 



