DROGUE . A sea anchor or other parachute-shaped 

 device for use in water. Drogues suspended at 

 desired depths by buoys are used to determine the 

 SET and DRIFT of currents at those depths, by 

 following the motions that they give to the buoys 

 at the surface. (24) 



DROWNING . Asphyxial death due to submersion in 

 water. 



DRT . Dead Reckoning Tracer. 



DRV . Deep Research Vehicle. 



DRY-BULB THERMOMETER . A thermometer with an un- 

 covered bulb, used with a wet-bulb thermometer to 

 determine atmospheric humidity. The two thermo- 

 meters constitute the essential parts of a 

 PSYCHROMETER . (17) 



DRY DOCK . See DOCK. 



DRY SUIT . See RUBBER SUIT. 



DSL . Deep Scattering Layer. 



DSSP . Deep Submergence Systems Project. 



DSSRG . Deep Submergence Systems Review Group. 



DTMB . United States Navy David Taylor Model Basin. 



DTMS . Department of Mines and Technical Surveys . 



DUAL-FILTER HYDROPHOTOMETER . This instrument can 

 be used to obtain in situ readings of two wave 

 lengths within the visible part of the spectrum, 

 and measurements can be made at day or night. 



The underwater unit consists of a 6- to 8- 

 volt automobile-type sealed-beam spotlight mounted 

 15 cm from two GE-type PV-10 photocells. Blue, 

 BG-12 and RG-(red) filters are mounted over each 

 of the photocells. Daylight, which would inter- 

 fere with transparency measurements, is filtered 

 out by using a honeycomb of blackened drinking 

 straws, placed between the photocells and the fil- 

 ters. The amount of light striking each photocell 

 is measured on the deck of the ship and gives a 

 measure of the transparency of the water. (35) 



DUCTILITY . The extent to which a material, par- 

 ticularly a metal, can sustain plastic deformation 

 without rupture. Bendability, Crushability, Elon- 

 gation Reduction of Area and Wrapping Diameter, 

 results of Cup Draw, Flattening, Kink, Repeated 



Bend and Twisting Tests are considered some indica- 

 tion of Ductility. 



DUNC. 



Deep Underwater Nuclear Counting. 



DURATION . In wave forecasting, the length of time 

 the wind blows in essentially the same direction 

 over the FETCH (generating area) . (11) 



DURATION, MINIMUM . The time necessary for steady 

 state wave conditions to develop for a given wind 

 velocity over a given FETCH LENGTH. (11) 



DUTCHMAN'S LOG . A buoyant object thrown overboard 

 to determine the speed of a vessel. The time re- 

 quired for a knovim length of the vessel to pass the 

 object is measured. The time and distance being 

 known, the speed can be computed. (17) 



DVNIGMI . Far Eastern Scientific Hydrometeoro- 

 logical Institute. 



DYKE . See DIKE. 



DYNAMIC METER . A unit used to represent the work 

 performed by lifting a unit mass nearly 1 meter. 



DYNAMIC PRESSURE . 1. The pressure exerted by a 

 fluid, such as air, by virtue of its motion. 



2. The pressure exerted on a 

 body, by virtue of its motion through a fluid, 

 for example, the pressure exerted on a rocket 

 moving through the atmosphere. (31) 



DYSBARISM . A general term which includes a com- 

 plex group of a wide variety of symptoms within 

 the body caused by changes in ambient pressure, 

 exclusive of HYPOXIA. (31) 



DYSPNEA . Shortness of breath, difficult or labored 

 respiration. 



DYNAMIC MODULUS. EFFECTIVE . An indication of 

 vibration absorption characteristics of rubber. 

 A measure of dynamic stiffness of rubber deformed 

 beyond the straight-line portion of the Load- 

 Deflection Diagram in the Yerzley Mechanical Oscil- 

 lograph Test. It is calculated as follows: 



Kc = 210 If^ 

 Kg ■= 105 If"^ 

 where 



Kc = Effective Dynamic Modulus in compression, Dsi 

 Kg = Effective Dynamic Modulus in shear, psi 

 I = moment of inertia of beam and weights, slug ft 

 f = Frequency, cps 



E 



EAGER. See BORE. 



EARTH TIDE . Periodic movement of the earth's crust 

 caused by the tide -producing forces of the moon and 

 sun. (14) 



EAST AUSTRALIA CURRENT . A Pacific Ocean current 

 flowing southward along the east coast of Australia, 

 from the Coral Sea to a point northeast of Tasmania, 

 where it curves eastward and northeastward, being 

 influenced by water entering the Tasman Sea from 

 the southwest. The east Australia current is a 

 continuation of the southern branch of the SOUTH 

 EQUATORIAL CURRENT, and forms the western part of 

 the general counterclockwise oceanic circulation 

 of the South Pacific Ocean. (17) 



EAST AUSTRALIA CURRENT . The ocean current flowing 

 southward along the east coast of Australia. It is 

 formed by the division of part of the SOUTH EQUA- 

 TORIAL CURRENT as it approaches the coast of Austra- 

 lia. Part of the east Australia Current joins the 

 WEST WIND DRIFT flowing eastward toward South 

 America . 



In the summer (Southern Hemisphere) part of 

 this water flows westward along the south coast of 

 Australia into the Indian Ocean. (14) 



EAST GREENLAND CURRENT . An ocean current flowing 

 south along the east coast of Greenland, carrying 

 water of low salinity and low temperature. The 

 east Greenland current is joined by most of the 

 water of the IRMINGER CURRENT. The greater part 

 of the current continues through Denmark Strait 

 between Iceland and Greenland, but one branch 

 turns to the east and forms a portion of the coun- 

 terclockwise circulation in the southern part of 

 the Norwegian Sea. Some of the east Greenland 

 current curves to the right around the tip of 



37 



