formed ice from about 1 foot to 6 feet in diameter, 

 with raised rims. The shape is the result of almost 

 constant collision among the various pieces. An 

 individual piece of pancake ice is called a pan. 

 Sometimes called LILLYPAD ICE when the individual 

 pieces are not more than about 18 inches in dia- 

 meter. Pancakes frozen together are called com- 

 pound pancake ice. (17) 



PARALLEL . A circle on the surface of the earth, 

 parallel to the plane of the equator and connect- 

 ing all points of equal latitude, or a circle 

 parallel to the primary great circle of a sphere 

 or spheroid; also a closed curve approximating 

 such a circle. An astronomical parallel is a line 

 connecting points having the same astronomical 

 latitude. A geodetic parallel is a line connect- 

 ing points of equal geodetic latitude. Geodetic 

 and sometimes astronomical parallels are also 

 called geographic parallels. Geodetic parallels 

 are shown on charts. A standard parallel is one 

 a^ong which the scale of a chart is as stated. A 

 fictitious, grid, transverse or inverse, or oblique 

 equator, respectively. A magnetic parallel is a 

 line connecting points of equal magnetic dip. Also 

 called parallel of latitude, circle of longitude. 

 (17) 



PARALLEL OF LATITUDE . 1. A circle (or approxima- 

 tion of a circle) on the surface of the earth, 

 parallel to the equator, and connecting points of 

 equal latitude. Also called parallel. 



2. A circle of the celestial 

 sphere, parallel to the ecliptic, and connecting 

 points of equal celestial latitude. Also called 

 circle of longitude. (17) 



PARALOC . This patented (Bissett-Berman) system is 

 a precise telemetry subcarrier phase-shift oscil- 

 lator, whose frequency is modulated by the change 

 in a sensed variable. This frequency is controlled 

 by the ratio of the output voltage to the input 

 voltage of a 4-terminal network sensor "bridge". 

 Its high sensitivity makes possible the amplifica- 

 tion and telemetering of signals from low-output 

 devices such as strain gages, resistance thermo- 

 meters, displacement transducers, conductivity 

 sensors, etc. The frequency output can be made to 

 deviate + 307o for a +1/2% change in the "error" 

 signal with very stable operation. The sum (Er) of 

 the guadrature voltage (Eg) and the sensor voltage 

 (Eo) are applied to the input amplifier (Al) , 

 thus forming a complete loop, which will oscillate 



TRANSFORMER 



at a frequency where the sum of phase shift between 

 (El) and the resultant (E^-) of the guadrature net- 

 work and the sensor network and the phase shift 

 between the input and the outputs of the phase- 

 shifting network totals 180°. Linearity is in the 

 order +0.017.; frequency stability is +0.02% for 

 temperature changes of +30° and supply voltage 

 changes of +207.; sensitivity adjustments are made 

 in the guadrature network and zero adjustments in 

 the sensor network with complete interdependency. 

 The Paraloc oscillator is used in sea water 

 salinity sensors, temperature sensors, and pressure 

 sensors installed on the ASWEPS "fish" and the 

 Office of Naval Research long range telemetering 

 buoy. (35) 



PARAMETRONS . Oscillatory devices whose phase can 

 be used to store and manipulate information. 



PARAPET . A low wall built along the edge of a 

 structure as on a SEAWALL or QUAY. (11) 



PARASITIC . Growing on or in living tissues of 

 plants or animals , obtaining nourishment at the 

 expense of the host. (18) 



PARTIAL NODE . A partial node is the point, line or 

 surface in a standing wave system where some charac- 

 teristic of the wave field has a minimum amplitude 

 differing from zero. (2) 



PARTIAL PRESSURE . See DALTON'S LAW. 



PARTICLE ACCELERATOR . Modern machines which accel- 

 erate subatomic particles to such great velocities 

 that as these particles strike atoms, the nucleus 

 of the atom may be altered or "split". Among these 

 now in use are the cyclotron, the linear accelera- 

 tor, the Van de Graaff generator. Proton Synchro- 

 tron, and the Bevatron. (39) 



PARTICLE VELOCITY . In ocean wave studies, the in- 

 stantaneous velocity of a water particle undergoes 

 ORBITAL MOTION. It has the scalar value 



He 



-2,TZ/L 



where T is the wave period, H the wave height, z 

 the depth below still-water level, and L the wave 

 length. 



At the crest, its direction is the same as 

 the direction of progress of the wave, and at the 

 trough it is in the opposite direction. (12) 



PASS . In hydrographic usage a navigable channel, 

 through a BAR, REEF, or SHOAL, or between closely 

 adjacent islands. (11) 



PASSIVE SONAR . Passive sonar is the method or 

 equipment by which information concerning a distant 

 object is obtained by evaluation of sound generated 

 by the object. (1) 



PASSIVE STATE (Corrosion) . State of a metal active 

 in the EMF series, or an alloy composed of such 

 metals, when it exhibits an appreciably greater 

 resistance to corrosion and behaves similarly to 

 those having a noble potential in a galvanic series. 

 Chromium and stainless steel are passive in certain 

 environments. (35) 



PASSIVE TRANSDUCER . A transducer connecting a 

 given source and a given load, and developing a 

 load power which is independent of sources of 

 energy controlled by the given source, is known 

 as a passive transducer. (4) 



PATENT LOG . See TAFFRAIL LOG. 



PC . U. S. Navy ship designation for a Sub Chaser. 



FCCECMRP . Permanent Commission of the Convention 

 on the Exploitation and Conservation of the Mari- 

 time Resources of the Pacific. 



PCE . U. S. Navy ship designation for an Escort 

 Sub Chaser. 



PCER. U. S. Navy ship designation for a Rescue 

 Escort. 



PCH . U. S. Navy ship designation for a Sub Chaser, 

 Hydrofoil. 



PCIFC. Permanent Commission of the International 

 Fisheries Convention. 



PCS . U. S. Navy ship designation for a Sub Chaser. 



88 



