DRIFT BOTTLE 



dome-shaped iceberg — See ice island iceberg. 



Doodson-Lege — A tide-prediction machine, used 

 at Liverpool (England) Observatory and Tidal 

 Institution. 



Doppler — See Doppler effect. 



Doppler effect- — (also called Doppler shift). 

 The change in frequency with which energy 

 reaches a receiver when the receiver and the 

 energy source are in motion relative to each 

 other. (5) 



Doppler shift — See Doppler effect. 



dorsal — Pertaining to or lying near the back; 

 opposite of ventral. (26) 



dosage — See dose. 



dose — (or dosage). According to current usage, 

 the radiation delivered to a specified area or 

 volume or to the whole body. Units for dose 

 specification are roentgens for X- or gamma 

 rays, reps or equivalent roentgens for beta rays. 

 In radiology the dose may be specified in air, 

 on the skin, or at some depth beneath the sur- 

 face; no statement of dose is complete without 

 specification of location. In recent years there 

 has been an increasing tendency to regard a 

 dose of radiation as the amount of energy 

 absorbed by tissue at the site of interest per unit 

 mass. See radiation absorbed dose, Roentgen 

 equivalent physical. (70) 



dosimeter — An instrument used to detect and 

 measure an accumulated dosage of radiation ; in 

 common usage it is a pencil size ionization 

 chamber with a built-in self reading electrom- 

 eter; used for personnel monitoring. (70) 



double ebb — An ebb current having two maxi- 

 mums of speed separated by a smaller ebb 

 speed. (50) 



double flood — A flood current having two maxi- 

 mums of speed separated by a smaller flood 

 speed. (50) 



double high water— xS^ee double tide. 



double tide — (or agger., double high water ^ 

 gulder). A high water consisting of two 

 maximums of nearly the same height separated 

 by a relatively small depression, or a low water 

 consisting of two minimums separated by a 

 relatively small elevation. (50) 



Douglas scale — A series of numbers from to 9 

 to indicate the condition of waves and swell. 

 Replaced by WMO Code 75. (73) 



No. State of Sea Swell 



Calm No swell. 



1 Smooth Low swell (short or average 



length) . 



2 Slight Low swell (long) . 



3 Moderate Moderate swell (short). 



4 Rough Moderate swell (average length). 



5 Very rough Moderate swell (long) . 



6 High Heavy swell (short) . 



7 Very high Heavy swell (average length). 



8 Precipitous Heavy swell (long). 



9 Confused..i-- Confused swell. 



downdrift — The direction of predominant move- 

 ment of littoral sediment. 



downstream — Generally the direction toward 

 which a fluid is moving, implying the horizontal 

 component of the mean direction or direction of 

 the basic current; the opposite of upstream. 

 (5) 



downward irradiance — The radiant flux on an 

 infinitesimal element of the upper face (0 to 180 

 degrees) of a horizontal surface containing the 

 point being considered, divided by the area of 

 that element. 



Unit of measurement is watt per square meter 

 (W/m=). (8) 



downwelling — See sinking (sense 1). 



dragon's tail — A towed thermistor chain used to 

 measure sea temperature. 



dredge — 1. A simple cylindrical or rectangular 

 device for collecting samples of bottom sedi- 

 ment and benthic fauna. These are generally 

 made of heavy gauge steel plate or pipe and 

 depend upon a scooping action to obtain the 

 sample. 



2. A ship designed to remove sediment from a 

 channel or dock region to maintain draft depths. 



dried ice — The ice surface from which the water 

 has disappeared after the formation of cracks 

 and holes. During the period of drying, the 

 surface becomes increasingly white. (74) 



dried weight — (or dry zveight, dry plankton). 

 The weight of organisms, such as plankton, 

 fouling, or benthos, from which water has been 

 driven but which has not been igiiited. The 

 term dry weight is more commonly used in the 

 study of fouling. 



dries — (or uncovers) . An area of a reef or other 

 projection from the bottom of a body of water 

 which periodically is covered and uncovered by 

 the water. 



drift — 1. The effect of the velocity of fluid flow 

 upon the velocity (relative to a fixed external 

 point) of an object moving within the fluid; 

 the vector difference between the velocity of 

 the object relative to the fluid and its velocity 

 to the fixed reference. ( 5 ) 



2. In publications for the mariner, drift is 

 the speed of a current or ice floe usuallj' given 

 in nautical miles per day or in knots. For the 

 oceanographer, drift is a wide, slow-moving cur- 

 rent principally caused by winds. 



3. Any rock material such as boulders, till, 

 gravel, sand, or clay, transported by a glacier 

 and deposited by the ice or by the water derived 

 from melting of the ice. (2) 



drift bottle — (also called bottle post). A bottle, 

 of one of various designs, which is released into 

 the sea for use in studying currents. It con- 

 tains a card (bottle paper), identifying the date 

 and place of release, to be returned by the finder 

 with the date and place of reco-\-ery. See drift 

 card. (5) 



51 



