PETTERSSON CURRENT METER. A meter designed by 

 Prof. 0. Pettersson and Dr. Hans Pettersson to give 

 a photographic record of both velocity and direc- 

 tion of the current. A detailed description by Dr. 

 Hans Pettersson is contained in the Quarterly Jour- 

 nal of the Royal Meteorological Society (London) 

 vol. XLI, No. 173, January 1915. There is also a 

 description of the meter in Coast and Geodetic Sur- 

 vey Special Publication No. 124, Instructions for 

 Tidal Current Surveys. (14) 



PF . U. S. Navy ship designation for a Patrol 

 Escort . 



PGM . U. S. Navy designation for a Motor Gunboat. 



PGR . Precision Graphic Recorder. 



pH . The acidity of a solution is determined by the 

 concentration of hydrogen ions in it. The pH of a 

 solution is a term used to express the effective 

 hydrogen ion concentration. It ranges from pH = 1 

 to pH =14. pH = 7 indicates a neutral solution. 

 Values lower than 7 indicate an acid condition. 

 The stronger the acidity the lower the pH. Con- 

 versely, values of pH above 7 indicate an alkaline 

 condition, the higher the pH the more alkaline the 

 solution. Fresh waters usually exhibit a pH of 

 about 6 to 7 . Sea water ranges from pH = 7.8 to 

 8.4 with an average of about 8.2. (35) 



P!-L\NTOM BOTTOM . A false bottom indicated by an 

 echo sounder, some distance above the actual bot- 

 tom. Such an indication, quite common in the 

 deeper parts of the ocean, is due to large quanti- 

 ties of small organisms. (17) 



PHASE SPEED (WAVE SPEED. PHASE VELOCITY, WAVE 

 VELOCITY, WAVE CELERITY) . The speed of propagation 

 of a point of constant phase (or phase angle) of a 

 simple harmonic wave component. Thus, the com- 

 ponent sin {2ti /X)(x - ct) represents a wave of 

 length >! traveling in the positive x-direction 

 with phase speed c. This concept is to be distin- 

 guished from signal velocity, GROUP VELOCITY, and 

 the velocity of fluid parcels. 



In oceanography, the terms wave velocity or 

 wave celerity are used more commonly than "phase 

 speed". (12) 



PHASE VELOCITY . See PHASE SPEED. 



PHIBLANT . Amphibious Forces, Atlantic (USN) . 



PHIBPAC. Amphibious Forces, Pacific (USN). 



illumination greater than 5 x 10"5 gm cal/cm^/min. , 

 and a neutral filter of density 4 is necessary if 

 the instrument is to be used at the surface. 



A photomultiplier tube is more sensitive to 

 short wave lengths than is a BARRIER LAYER CELL. 

 Its peak sensitivity is around 4,500 A. In deep 

 water it should be necessary to use only a blue- 

 green filter; however, an automatic filter chang- 

 ing device has been developed. (35) 



PHOTOSYNTHESIS . The manufacture of carbohydrate 

 from carbon dioxide and water in the presence of 

 chlorophyll, using light energy and releasing 

 oxygen. (18) 



PHOTOTUBE CURRENT METER . In this instrument, a 

 light of constant intensity is emitted from a light 

 source, and is reflected by a cylindrical mirror 

 into a phototube producing photoelectric current. 

 A disc (with a hole) which rotates in accordance 

 with the current by means of a propeller, is placed 

 in the path of the light between the light source 

 and the mirror. Therefore, an intermittent flash 

 of light is produced by a rotating disc, the fre- 

 quency of flashes being proportional to the speed 

 of the current. Thus, the latter can be measured 

 from the frequency of the flashes. The phototube 

 output is amplified and activates a recorder. (30) 



PHS. 



Public Health Service. 



PHYCHROPHILE . See STENOHALINE. 



PHYCOCYANIN . A blue, water-soluble accessory pig 

 ment found in such plants as blue-green al?ae. 

 (13) 



PHYCOERYTHRIN . Any of the red protein pigments in 

 the cells of red algae. (20) 



PHYCOXANTHIN . See DIATOMIN. 



PHYTO PLANKTON . See MARINE LIFE. 



PIEDMONT ICE . An ice sheet formed by the joining 

 of two or more glaciers on a comparatively level 

 plain at the base of the mountains down which the 

 glaciers descended. It may be partly afloat. (17) 



PIER . A long, narrow structure extending into the 

 water to afford a berthing place for vessels, to 

 serve as a promenade, etc. Such a structure usual- 

 ly of solid construction, intended as a berthing 

 place for vessels is also called a JETTY in British 

 terminology. See also MOLE, WHARF. (17) 



PHLEGER CORER . Designed to obtain cores up to 

 about 4 feet in length, the Phleger corer is uti- 

 lized where only the upper layers of the sea bottom 

 are to be analyzed . Coring tubes 12 and 36 inches 

 in length, a main body weight, an upper tube, check 

 valve, and tailfin assembly account for the overall 

 length of 3 to 5 feet. The upper tube, main body 

 weight, check valve, and tailfin assembly comprise 

 the mainweight. A check valve, located at the tail- 

 fin, prevents the flow of water into the upper sec- 

 tion and a consequent washing out of the core sample 

 while hoisting the corer. Plastic liners are used 

 to collect and store the cores. A short free fall 

 is provided by a counterweight and triggering 

 mechanism. The Phleger corer does not employ a 

 piston. (35) 



PHOTOMETER . See PHOTOMULTIPLIER TUBE. 



PHOTOMULTIPLIER TUBE (PHOTOMETER) . Photomultiplier- 

 type photometers are sufficiently sensitive to 

 measure illumination as little as lO"-'-^ gm cal/cm^ 

 /min. and can be used to a depth of 500 to 600 

 meters. It is necessary to use some type of shield- 

 ing device when using a photomultiplier tube in 



PIERHEAD . 



1. 

 2. 



The outer end of a pier. 

 A breakwater. This meaning 



general in the Great Lakes area but is only oc- 

 casionally used elsewhere. (17) 



PIEZOELECTRIC EFFECT . Phenomenon, exhibited by 

 certain crystals, in which mechanical compression 

 produces a potential difference between opposite 

 crystal faces, or, an applied electric field 

 produces corresponding changes in dimensions. (6) 



PIEZOELECTRICITY . Piezoelectricity is the property 

 exhibited by some asymmetrical crystalline materi- 

 als which when subjected to strain in suitable 

 directions develop electric polarization propor- 

 tional to the strain. Inverse piezoelectricity is 

 the effect in which mechanical strain is produced 

 in certain asymmetrical crystalline materials when 

 subjected to an external electric field; the strain 

 is proportional to the electric field. (1) 



PIEZOMETRIC . Of or related to pressure or the 

 PIEZOMETER. (20) 



90 



