Page:Dictionary of aviation.djvu/198

 174 DICTIONARY OF AVIATION

pole-star 'poot,sta:z n. the star alfa in Ursae Minoris, at present about 11-4 degrees distant from the northern pole of the hevens; the North Star; the Polar Star; Polaris.

polyplane 'peh^pteen n. a multiplane.

pongee ,pen'd3ii, (assumptivly) 'pen/isi n. a soft unbleacht Chinese silk made from the cocoons of a wild silk^worm, Bembyx pernyi or fantoni, which feeds n oak-leaves, some- times used in making balloon-envelops or gasbags; Chefoo silk.

pontoon ,pon'tuun n. a floating structure of light framework such as one of the flatebettomd boats used to support a dirigible upon a water-surface, or one of the hellow floats attacht to the lower part of a flymg-machine to keep it afloat in case it falls into or alights upon the water.

port poizt adj. en that side of an aircraft which is on the left as one faces the bow; larboard: the opposit of star- board.

potential-gradient pa'tenSa^gzee-di-ant. the gradient 01 electric potential; the rate of change in the electric po- tential of the air.

powder-down 'pau-d9z,daon n. the powdery down or fluffy, dusty, or scurfy exfoliation due to the presence of certain down-fethers or plumulae in some birds, as the heron; pulviplume.

power 'pau-az n. the capacity (of a balloon) to rise ; ability to ascend or mount; lifting-capacity ; ascensiv power.

power-gas 'pau-9z,gaes n. gas used for power, as that used in an mternal-combustion engin.

power-plant 'pau-9z,pz,a:nt n. a plant or apparatus which furnishes power; the engin or motor of an airship.

power-vessel 'pau-9z,ves3l n. the vessel or car in which the power-plant of an airship is located.

precess ,psi'ses intr. move forward; advance : as, vortices which *precess downward.

precipitation psi,sipi'tee-$3n n. condensation and deposi- tion of moisture from the state of vapor, as in the for- mation of dew, rain, or snow by cooling; also, that tuhich is so deposited, as rain, snow, or hail.

presentation ,p5izen'tee-$3n n. the precess, state, condi- tion, or mode of being presented to view; exhibition; ap- pearance, aspect : as, the shape of an aerofoil's face in ^presentation.

diagonal presentation, the presentation of an aeroplane in a diagonal or oblique manner, as in aerodynamic experi- mentation; oblique presentation.

square presentation, the presentation of an aeroplane in

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