PILE . A long, slender piece of wood, concrete, or 

 metal to be driven or jetted Into the earth or sea 

 bed to serve as a support or protection. (11) 



PILING . A group of PILES. (11) 



PILLAR BUOY . A buoy composed of a tall central 

 structure mounted on a broad flat base. Pillar 

 buoys are not used in United States waters. Also 

 called beacon buoy. (17) 



PING . Acoustic pulse signal projected by an echo- 

 ranging transducer. (6) 



PINNACLE. Any characteristic rocky column which is 

 dangerous to surface navigation. Any high tower or 

 spire-shaped pillar or rock, alone or cresting a 

 summit. (27) 



PINNACLED ICEBERG (PYRAMIDAL ICEBERG. IRREGULAR 

 ICEBERG) . An iceberg weathered in such manner as 

 to produce spires or pinnacles. (17) 



PINRO . Polar Institute for Fishing and Oceano- 

 graphy (USSR) . 



PIOSA . Pan-Indian Ocean Science Association. 



PIP . An echo trace on an indicator screen. (7) 



PIPICO . Panel on International Programs of the 

 ICO. 



PISCIVOROUS . Fish-eating. For instance, the food 

 habit of bathypelagic fishes must be mainly pis- 

 civorous due to the lack of plankton at great 

 depths. (13) 



PITCH . The oscillation of a ship about the lateral 

 axis, i.e., alternate rising and falling of bow 

 and stern. (12) 



PITTING . A type of corrosion that develops cavi- 

 ties or pits in highly localized areas on a metal 

 surface that is not particularly affected elsewhere. 

 These pits may vary from deep cavities of small 

 diameter to relatively shallow depressions. 



PLAIN . A flat, gently sloping or nearly level 

 region of the sea floor. (26) 



PLANE POLARIZED SOUND WAVE (LINEARLY POLARIZED 

 SOUND WAVE) . A plane polarized sound wave is a 

 transverse wave; hence, every particle in the 

 medium is moving at right angles to the direction 

 of propagation of the wave. There is added, 

 however, the additional requirement that the motion 

 at each point shall be along a straight line. (9) 



PLANE WAVE . A plane wave is a wave in which the 

 wave fronts are everywhere parallel planes normal 

 to the direction of propagation. (9) 



PLANFORM . The outline or shape of a body of water 

 as determined by the still water line. (11) 



PLANKTON . All the floating or drifting life found 

 in the pelagic division of the sea. Plankton are 

 further divided into PHYTOPLANKTON which includes 

 all the floating and drifting plants, and ZOOPLANK- 

 TON which includes (1) myriads of animals that live 

 permanently in a floating or drifting state and 

 countless numbers of helpless larvae and eggs of 

 the animal benthos and nekton. See MARINE LIFE. 



(2) 



PLATEAU . A comparatively flat-topped elevation of 

 the sea floor greater than 60 nautical miles across 

 the summit and normally rising more than 100 fath- 

 oms on all sides. (26) 



PLATE ICE. See PANCAKE ICE. 



TYPICAL PLANKTON-COLLECTING DEVICES 



SHIP ON 



RECULJIR 

 COMMERCIAL 



UNE 



SUSPENSION 

 WIRE 



[HYDROGRAPHIC 

 WIRE) 



PLANKTON SAMPLER 



TOWING CABLE 



VIBRATION DAMPER- 



COLLECTING 

 VESSEL 



PROPELLER 



TURNED WHEN 



TOWED 



THROUGH SEA- 



RUBBER TUBE 

 STERILE BOTTLE 



V;_:^L»- FRAME 



Q MESSENGER 



I RELEASE 



THE BACTERIA OR NANNOPLANKTON SAMPLING BOTTLES 



TAIL PLANE 



HARPY PLANKTON RECORDER 



TOWING 

 RECORDER AT 

 DEPTH OF 

 10 METRES 

 (33 FEET) 



91 



