Page:Dictionary of aviation.djvu/205

 DICTIONARY OF AVIATION 181

mercurial thermemeter enclosed in a glass vacuum-tube, used for mesuring solar radiation.

radiation-weather ,zedi'ee-$9n,wed9z n. wether due to, or controlled largely by, radiation of heat from the ground; the wether characteristic of an area of high atmosferic pres- sure, clear sky, and light winds, varying with the thermal radiations from the earth.

radiometer ,zedi'emi-t9z n. an instrument consisting of a frame supporting mica-vanes which are free to revelv in a vacuum, used for mesunng or demonstrating the effects of radiant energy, as light or heat.

radius 'zee-di-as n. [plural radii} one of the processes en each side of the upper border of a bird's fether; a barbule.

aerodromic radius, the distance in a straight line from the mass-center of an aerodone to the aerodromic wing- center.

aerodynamic radius, the distance in a straight line from the mass-center of an aerodone to the aerodynamic wing- center. raft zarft n.

aerial raft, a flat structure capable of floating in the air; an aeroplane.

rail zee! n. see startingzrail and launching^ -ail. rain zeen n. water in the form of drops resulting from the condensation and aggregation of vapor, falling thru the lower regions of the air or atmosfere; also, the descent or fall of water in this form; and, further, a shower, period, or season characterized by the fall of water in this ferm.

belt of rains, the belt or long narrow equatorial region between the tradewinds, nearly encircling the earth, char- acterized by frequent rains thruout the year; the equatorial rain-belt.

black rain, rain or rainwater which is somewhat black, or which leavs a black residue owing to the presence of black fungi, black seil, or soot carried down from the at- mosfere.

coast rain, one of the rains characteristic of the coast or costal regions of a continent or island, usually due to winds blowing off the sea toward the land.

convective rain, rain which is due to the cooling of air by expansion when forced upward by convection-currents.

cyclonic rain, rain whch is due to the cooling of air by expansion when forced upward by cyclonic circulation.

dynamic theory of the formation of rain, the theory of Espy and others that rain, snow, etc., is caused by thermo- dynamic processes.

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