78 DICTIONARY OF AVIATION
ship's compass, owing to the magnetism of the iron in the ship, or other local cause.
deviator 'dii-vi,etaz n. an apparatus attacht to a balloon by a rope and intended to tr.ail along behind in the sea and thus deviate or turn the balloon from its normal course.
dew djou n. the moisture occurring in minute drops en the grass or any cool surface, due to the condensation of the water^vapor in the air towards or during the night after a hot day, and especially plentiful in the early morning.
dew-bow 'djou,boo n. an iridescent bow or halo, seen on a surface coverd with dew; a rainbow^like effect caused by dew-drops.
dew-fall 'djuu,fc:l n. the fall, formation, or deposition of dew; a fall or deposit of dew; also, the time when this be- gins, in the evening.
dew-point 'djuujjeint n. that point or degree of the tempe- rature of the air at uuhich dew begins to form.
complement of the dewfpoint, the number of degrees by tuhich the temperature of the dew-point is below the tempe- rature of the air; the depression of the dew-point.
depression of the dew-point, the extent to tuhich the dew? peint is deprest below the temperature of the air; the com- plement of the dew-point.
dew-point apparatus, an apparatus for determining the dew-point.
dew-point hygrometer, see under hygrometer.
diagonal /lai'aegs-nl n. a diagonal brace or stay in the framework of a f lyingsmachine ; a cress^stay.
diaphragm / dai-9,fs3em n. [also spelt diafram] a septum, membrane, sheet, or any thin partition, as that dividing one compartment of the gasbag of a balloon from another.
diedral ,dai'ii-dr9l adj. same meaning as dihedral.
dietheroscope ,dai-i'0ez9,skop n. an instrument for show- ing the refraction of the air in mirage.
dihedral ,dai'hii-dr9l adj. [synonymous cognate diedral] fur- nisht with, or containd by, two planes or plane faces : said of a pair of wings or aerofoils inclined upward and away from each other.
dihedral angle, the solid angle formd by two planes; the inclination of two planes, as aeroplanes or wing^surfaces, which meet or approach each other usually at their lower edges.
dilatation ,dai-l9'tee-$9n . the action or process of dilat- ing; the state of being dilated; expansion, as of a balloon.
dimensional di'men$9-nl adj. relating, to dimension or magnitude: as, *dimensional theory.
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